Index: head/crypto/openssh/moduli.5 =================================================================== --- head/crypto/openssh/moduli.5 (revision 290670) +++ head/crypto/openssh/moduli.5 (revision 290671) @@ -1,128 +1,127 @@ .\" $OpenBSD: moduli.5,v 1.17 2012/09/26 17:34:38 jmc Exp $ -.\" $FreeBSD$ .\" .\" Copyright (c) 2008 Damien Miller .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. -.Dd September 26, 2012 +.Dd $Mdocdate: September 26 2012 $ .Dt MODULI 5 .Os .Sh NAME .Nm moduli .Nd Diffie-Hellman moduli .Sh DESCRIPTION The .Pa /etc/moduli file contains prime numbers and generators for use by .Xr sshd 8 in the Diffie-Hellman Group Exchange key exchange method. .Pp New moduli may be generated with .Xr ssh-keygen 1 using a two-step process. An initial .Em candidate generation pass, using .Ic ssh-keygen -G , calculates numbers that are likely to be useful. A second .Em primality testing pass, using .Ic ssh-keygen -T , provides a high degree of assurance that the numbers are prime and are safe for use in Diffie-Hellman operations by .Xr sshd 8 . This .Nm format is used as the output from each pass. .Pp The file consists of newline-separated records, one per modulus, containing seven space-separated fields. These fields are as follows: .Bl -tag -width Description -offset indent .It timestamp The time that the modulus was last processed as YYYYMMDDHHMMSS. .It type Decimal number specifying the internal structure of the prime modulus. Supported types are: .Pp .Bl -tag -width 0x00 -compact .It 0 Unknown, not tested. .It 2 "Safe" prime; (p-1)/2 is also prime. .It 4 Sophie Germain; 2p+1 is also prime. .El .Pp Moduli candidates initially produced by .Xr ssh-keygen 1 are Sophie Germain primes (type 4). Further primality testing with .Xr ssh-keygen 1 produces safe prime moduli (type 2) that are ready for use in .Xr sshd 8 . Other types are not used by OpenSSH. .It tests Decimal number indicating the type of primality tests that the number has been subjected to represented as a bitmask of the following values: .Pp .Bl -tag -width 0x00 -compact .It 0x00 Not tested. .It 0x01 Composite number \(en not prime. .It 0x02 Sieve of Eratosthenes. .It 0x04 Probabilistic Miller-Rabin primality tests. .El .Pp The .Xr ssh-keygen 1 moduli candidate generation uses the Sieve of Eratosthenes (flag 0x02). Subsequent .Xr ssh-keygen 1 primality tests are Miller-Rabin tests (flag 0x04). .It trials Decimal number indicating the number of primality trials that have been performed on the modulus. .It size Decimal number indicating the size of the prime in bits. .It generator The recommended generator for use with this modulus (hexadecimal). .It modulus The modulus itself in hexadecimal. .El .Pp When performing Diffie-Hellman Group Exchange, .Xr sshd 8 first estimates the size of the modulus required to produce enough Diffie-Hellman output to sufficiently key the selected symmetric cipher. .Xr sshd 8 then randomly selects a modulus from .Fa /etc/moduli that best meets the size requirement. .Sh SEE ALSO .Xr ssh-keygen 1 , .Xr sshd 8 .Sh STANDARDS .Rs .%A M. Friedl .%A N. Provos .%A W. Simpson .%D March 2006 .%R RFC 4419 .%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol .%D 2006 .Re Index: head/crypto/openssh/scp.1 =================================================================== --- head/crypto/openssh/scp.1 (revision 290670) +++ head/crypto/openssh/scp.1 (revision 290671) @@ -1,246 +1,245 @@ .\" .\" scp.1 .\" .\" Author: Tatu Ylonen .\" .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" Created: Sun May 7 00:14:37 1995 ylo .\" .\" $OpenBSD: scp.1,v 1.61 2013/10/20 09:51:26 djm Exp $ -.\" $FreeBSD$ .\" -.Dd October 20, 2013 +.Dd $Mdocdate: October 20 2013 $ .Dt SCP 1 .Os .Sh NAME .Nm scp .Nd secure copy (remote file copy program) .Sh SYNOPSIS .Nm scp .Bk -words .Op Fl 12346BCpqrv .Op Fl c Ar cipher .Op Fl F Ar ssh_config .Op Fl i Ar identity_file .Op Fl l Ar limit .Op Fl o Ar ssh_option .Op Fl P Ar port .Op Fl S Ar program .Sm off .Oo .Op Ar user No @ .Ar host1 No : .Oc Ar file1 .Sm on .Ar ... .Sm off .Oo .Op Ar user No @ .Ar host2 No : .Oc Ar file2 .Sm on .Ek .Sh DESCRIPTION .Nm copies files between hosts on a network. It uses .Xr ssh 1 for data transfer, and uses the same authentication and provides the same security as .Xr ssh 1 . Unlike .Xr rcp 1 , .Nm will ask for passwords or passphrases if they are needed for authentication. .Pp File names may contain a user and host specification to indicate that the file is to be copied to/from that host. Local file names can be made explicit using absolute or relative pathnames to avoid .Nm treating file names containing .Sq :\& as host specifiers. Copies between two remote hosts are also permitted. .Pp The options are as follows: .Bl -tag -width Ds .It Fl 1 Forces .Nm to use protocol 1. .It Fl 2 Forces .Nm to use protocol 2. .It Fl 3 Copies between two remote hosts are transferred through the local host. Without this option the data is copied directly between the two remote hosts. Note that this option disables the progress meter. .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl B Selects batch mode (prevents asking for passwords or passphrases). .It Fl C Compression enable. Passes the .Fl C flag to .Xr ssh 1 to enable compression. .It Fl c Ar cipher Selects the cipher to use for encrypting the data transfer. This option is directly passed to .Xr ssh 1 . .It Fl F Ar ssh_config Specifies an alternative per-user configuration file for .Nm ssh . This option is directly passed to .Xr ssh 1 . .It Fl i Ar identity_file Selects the file from which the identity (private key) for public key authentication is read. This option is directly passed to .Xr ssh 1 . .It Fl l Ar limit Limits the used bandwidth, specified in Kbit/s. .It Fl o Ar ssh_option Can be used to pass options to .Nm ssh in the format used in .Xr ssh_config 5 . This is useful for specifying options for which there is no separate .Nm scp command-line flag. For full details of the options listed below, and their possible values, see .Xr ssh_config 5 . .Pp .Bl -tag -width Ds -offset indent -compact .It AddressFamily .It BatchMode .It BindAddress .It CanonicalDomains .It CanonicalizeFallbackLocal .It CanonicalizeHostname .It CanonicalizeMaxDots .It CanonicalizePermittedCNAMEs .It ChallengeResponseAuthentication .It CheckHostIP .It Cipher .It Ciphers .It Compression .It CompressionLevel .It ConnectionAttempts .It ConnectTimeout .It ControlMaster .It ControlPath .It ControlPersist .It GlobalKnownHostsFile .It GSSAPIAuthentication .It GSSAPIDelegateCredentials .It HashKnownHosts .It Host .It HostbasedAuthentication .It HostKeyAlgorithms .It HostKeyAlias .It HostName .It IdentityFile .It IdentitiesOnly .It IPQoS .It KbdInteractiveAuthentication .It KbdInteractiveDevices .It KexAlgorithms .It LogLevel .It MACs .It NoHostAuthenticationForLocalhost .It NumberOfPasswordPrompts .It PasswordAuthentication .It PKCS11Provider .It Port .It PreferredAuthentications .It Protocol .It ProxyCommand .It PubkeyAuthentication .It RekeyLimit .It RhostsRSAAuthentication .It RSAAuthentication .It SendEnv .It ServerAliveInterval .It ServerAliveCountMax .It StrictHostKeyChecking .It TCPKeepAlive .It UsePrivilegedPort .It User .It UserKnownHostsFile .It VerifyHostKeyDNS .El .It Fl P Ar port Specifies the port to connect to on the remote host. Note that this option is written with a capital .Sq P , because .Fl p is already reserved for preserving the times and modes of the file in .Xr rcp 1 . .It Fl p Preserves modification times, access times, and modes from the original file. .It Fl q Quiet mode: disables the progress meter as well as warning and diagnostic messages from .Xr ssh 1 . .It Fl r Recursively copy entire directories. Note that .Nm follows symbolic links encountered in the tree traversal. .It Fl S Ar program Name of .Ar program to use for the encrypted connection. The program must understand .Xr ssh 1 options. .It Fl v Verbose mode. Causes .Nm and .Xr ssh 1 to print debugging messages about their progress. This is helpful in debugging connection, authentication, and configuration problems. .El .Sh EXIT STATUS .Ex -std scp .Sh SEE ALSO .Xr rcp 1 , .Xr sftp 1 , .Xr ssh 1 , .Xr ssh-add 1 , .Xr ssh-agent 1 , .Xr ssh-keygen 1 , .Xr ssh_config 5 , .Xr sshd 8 .Sh HISTORY .Nm is based on the .Xr rcp 1 program in .Bx source code from the Regents of the University of California. .Sh AUTHORS .An Timo Rinne Aq Mt tri@iki.fi .An Tatu Ylonen Aq Mt ylo@cs.hut.fi Index: head/crypto/openssh/sftp-server.8 =================================================================== --- head/crypto/openssh/sftp-server.8 (revision 290670) +++ head/crypto/openssh/sftp-server.8 (revision 290671) @@ -1,171 +1,170 @@ .\" $OpenBSD: sftp-server.8,v 1.25 2013/10/14 14:18:56 jmc Exp $ -.\" $FreeBSD$ .\" .\" Copyright (c) 2000 Markus Friedl. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd October 14, 2013 +.Dd $Mdocdate: October 14 2013 $ .Dt SFTP-SERVER 8 .Os .Sh NAME .Nm sftp-server .Nd SFTP server subsystem .Sh SYNOPSIS .Nm sftp-server .Bk -words .Op Fl ehR .Op Fl d Ar start_directory .Op Fl f Ar log_facility .Op Fl l Ar log_level .Op Fl P Ar blacklisted_requests .Op Fl p Ar whitelisted_requests .Op Fl u Ar umask .Ek .Nm .Fl Q Ar protocol_feature .Sh DESCRIPTION .Nm is a program that speaks the server side of SFTP protocol to stdout and expects client requests from stdin. .Nm is not intended to be called directly, but from .Xr sshd 8 using the .Cm Subsystem option. .Pp Command-line flags to .Nm should be specified in the .Cm Subsystem declaration. See .Xr sshd_config 5 for more information. .Pp Valid options are: .Bl -tag -width Ds .It Fl d Ar start_directory specifies an alternate starting directory for users. The pathname may contain the following tokens that are expanded at runtime: %% is replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. The default is to use the user's home directory. This option is useful in conjunction with the .Xr sshd_config 5 .Cm ChrootDirectory option. .It Fl e Causes .Nm to print logging information to stderr instead of syslog for debugging. .It Fl f Ar log_facility Specifies the facility code that is used when logging messages from .Nm . The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH. .It Fl h Displays .Nm usage information. .It Fl l Ar log_level Specifies which messages will be logged by .Nm . The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. INFO and VERBOSE log transactions that .Nm performs on behalf of the client. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of debugging output. The default is ERROR. .It Fl P Ar blacklisted_requests Specify a comma-separated list of SFTP protocol requests that are banned by the server. .Nm will reply to any blacklisted request with a failure. The .Fl Q flag can be used to determine the supported request types. If both a blacklist and a whitelist are specified, then the blacklist is applied before the whitelist. .It Fl p Ar whitelisted_requests Specify a comma-separated list of SFTP protocol requests that are permitted by the server. All request types that are not on the whitelist will be logged and replied to with a failure message. .Pp Care must be taken when using this feature to ensure that requests made implicitly by SFTP clients are permitted. .It Fl Q Ar protocol_feature Query protocol features supported by .Nm . At present the only feature that may be queried is .Dq requests , which may be used for black or whitelisting (flags .Fl P and .Fl p respectively). .It Fl R Places this instance of .Nm into a read-only mode. Attempts to open files for writing, as well as other operations that change the state of the filesystem, will be denied. .It Fl u Ar umask Sets an explicit .Xr umask 2 to be applied to newly-created files and directories, instead of the user's default mask. .El .Pp For logging to work, .Nm must be able to access .Pa /dev/log . Use of .Nm in a chroot configuration therefore requires that .Xr syslogd 8 establish a logging socket inside the chroot directory. .Sh SEE ALSO .Xr sftp 1 , .Xr ssh 1 , .Xr sshd_config 5 , .Xr sshd 8 .Rs .%A T. Ylonen .%A S. Lehtinen .%T "SSH File Transfer Protocol" .%N draft-ietf-secsh-filexfer-02.txt .%D October 2001 .%O work in progress material .Re .Sh HISTORY .Nm first appeared in .Ox 2.8 . .Sh AUTHORS .An Markus Friedl Aq Mt markus@openbsd.org Index: head/crypto/openssh/sftp.1 =================================================================== --- head/crypto/openssh/sftp.1 (revision 290670) +++ head/crypto/openssh/sftp.1 (revision 290671) @@ -1,604 +1,603 @@ .\" $OpenBSD: sftp.1,v 1.97 2013/10/20 09:51:26 djm Exp $ -.\" $FreeBSD$ .\" .\" Copyright (c) 2001 Damien Miller. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd October 20, 2013 +.Dd $Mdocdate: October 20 2013 $ .Dt SFTP 1 .Os .Sh NAME .Nm sftp .Nd secure file transfer program .Sh SYNOPSIS .Nm sftp .Bk -words .Op Fl 1246aCfpqrv .Op Fl B Ar buffer_size .Op Fl b Ar batchfile .Op Fl c Ar cipher .Op Fl D Ar sftp_server_path .Op Fl F Ar ssh_config .Op Fl i Ar identity_file .Op Fl l Ar limit .Op Fl o Ar ssh_option .Op Fl P Ar port .Op Fl R Ar num_requests .Op Fl S Ar program .Op Fl s Ar subsystem | sftp_server .Ar host .Ek .Nm sftp .Oo Ar user Ns @ Oc Ns .Ar host Ns Op : Ns Ar .Nm sftp .Oo .Ar user Ns @ Oc Ns .Ar host Ns Oo : Ns Ar dir Ns .Op Ar / .Oc .Nm sftp .Fl b Ar batchfile .Oo Ar user Ns @ Oc Ns Ar host .Sh DESCRIPTION .Nm is an interactive file transfer program, similar to .Xr ftp 1 , which performs all operations over an encrypted .Xr ssh 1 transport. It may also use many features of ssh, such as public key authentication and compression. .Nm connects and logs into the specified .Ar host , then enters an interactive command mode. .Pp The second usage format will retrieve files automatically if a non-interactive authentication method is used; otherwise it will do so after successful interactive authentication. .Pp The third usage format allows .Nm to start in a remote directory. .Pp The final usage format allows for automated sessions using the .Fl b option. In such cases, it is necessary to configure non-interactive authentication to obviate the need to enter a password at connection time (see .Xr sshd 8 and .Xr ssh-keygen 1 for details). .Pp Since some usage formats use colon characters to delimit host names from path names, IPv6 addresses must be enclosed in square brackets to avoid ambiguity. .Pp The options are as follows: .Bl -tag -width Ds .It Fl 1 Specify the use of protocol version 1. .It Fl 2 Specify the use of protocol version 2. .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl a Attempt to continue interrupted downloads rather than overwriting existing partial or complete copies of files. If the remote file contents differ from the partial local copy then the resultant file is likely to be corrupt. .It Fl B Ar buffer_size Specify the size of the buffer that .Nm uses when transferring files. Larger buffers require fewer round trips at the cost of higher memory consumption. The default is 32768 bytes. .It Fl b Ar batchfile Batch mode reads a series of commands from an input .Ar batchfile instead of .Em stdin . Since it lacks user interaction it should be used in conjunction with non-interactive authentication. A .Ar batchfile of .Sq \- may be used to indicate standard input. .Nm will abort if any of the following commands fail: .Ic get , put , reget , rename , ln , .Ic rm , mkdir , chdir , ls , .Ic lchdir , chmod , chown , .Ic chgrp , lpwd , df , symlink , and .Ic lmkdir . Termination on error can be suppressed on a command by command basis by prefixing the command with a .Sq \- character (for example, .Ic -rm /tmp/blah* ) . .It Fl C Enables compression (via ssh's .Fl C flag). .It Fl c Ar cipher Selects the cipher to use for encrypting the data transfers. This option is directly passed to .Xr ssh 1 . .It Fl D Ar sftp_server_path Connect directly to a local sftp server (rather than via .Xr ssh 1 ) . This option may be useful in debugging the client and server. .It Fl F Ar ssh_config Specifies an alternative per-user configuration file for .Xr ssh 1 . This option is directly passed to .Xr ssh 1 . .It Fl f Requests that files be flushed to disk immediately after transfer. When uploading files, this feature is only enabled if the server implements the "fsync@openssh.com" extension. .It Fl i Ar identity_file Selects the file from which the identity (private key) for public key authentication is read. This option is directly passed to .Xr ssh 1 . .It Fl l Ar limit Limits the used bandwidth, specified in Kbit/s. .It Fl o Ar ssh_option Can be used to pass options to .Nm ssh in the format used in .Xr ssh_config 5 . This is useful for specifying options for which there is no separate .Nm sftp command-line flag. For example, to specify an alternate port use: .Ic sftp -oPort=24 . For full details of the options listed below, and their possible values, see .Xr ssh_config 5 . .Pp .Bl -tag -width Ds -offset indent -compact .It AddressFamily .It BatchMode .It BindAddress .It CanonicalDomains .It CanonicalizeFallbackLocal .It CanonicalizeHostname .It CanonicalizeMaxDots .It CanonicalizePermittedCNAMEs .It ChallengeResponseAuthentication .It CheckHostIP .It Cipher .It Ciphers .It Compression .It CompressionLevel .It ConnectionAttempts .It ConnectTimeout .It ControlMaster .It ControlPath .It ControlPersist .It GlobalKnownHostsFile .It GSSAPIAuthentication .It GSSAPIDelegateCredentials .It HashKnownHosts .It Host .It HostbasedAuthentication .It HostKeyAlgorithms .It HostKeyAlias .It HostName .It IdentityFile .It IdentitiesOnly .It IPQoS .It KbdInteractiveAuthentication .It KbdInteractiveDevices .It KexAlgorithms .It LogLevel .It MACs .It NoHostAuthenticationForLocalhost .It NumberOfPasswordPrompts .It PasswordAuthentication .It PKCS11Provider .It Port .It PreferredAuthentications .It Protocol .It ProxyCommand .It PubkeyAuthentication .It RekeyLimit .It RhostsRSAAuthentication .It RSAAuthentication .It SendEnv .It ServerAliveInterval .It ServerAliveCountMax .It StrictHostKeyChecking .It TCPKeepAlive .It UsePrivilegedPort .It User .It UserKnownHostsFile .It VerifyHostKeyDNS .El .It Fl P Ar port Specifies the port to connect to on the remote host. .It Fl p Preserves modification times, access times, and modes from the original files transferred. .It Fl q Quiet mode: disables the progress meter as well as warning and diagnostic messages from .Xr ssh 1 . .It Fl R Ar num_requests Specify how many requests may be outstanding at any one time. Increasing this may slightly improve file transfer speed but will increase memory usage. The default is 256 outstanding requests providing for 8MB of outstanding data with a 32KB buffer. .It Fl r Recursively copy entire directories when uploading and downloading. Note that .Nm does not follow symbolic links encountered in the tree traversal. .It Fl S Ar program Name of the .Ar program to use for the encrypted connection. The program must understand .Xr ssh 1 options. .It Fl s Ar subsystem | sftp_server Specifies the SSH2 subsystem or the path for an sftp server on the remote host. A path is useful for using .Nm over protocol version 1, or when the remote .Xr sshd 8 does not have an sftp subsystem configured. .It Fl v Raise logging level. This option is also passed to ssh. .El .Sh INTERACTIVE COMMANDS Once in interactive mode, .Nm understands a set of commands similar to those of .Xr ftp 1 . Commands are case insensitive. Pathnames that contain spaces must be enclosed in quotes. Any special characters contained within pathnames that are recognized by .Xr glob 3 must be escaped with backslashes .Pq Sq \e . .Bl -tag -width Ds .It Ic bye Quit .Nm sftp . .It Ic cd Ar path Change remote directory to .Ar path . .It Ic chgrp Ar grp Ar path Change group of file .Ar path to .Ar grp . .Ar path may contain .Xr glob 3 characters and may match multiple files. .Ar grp must be a numeric GID. .It Ic chmod Ar mode Ar path Change permissions of file .Ar path to .Ar mode . .Ar path may contain .Xr glob 3 characters and may match multiple files. .It Ic chown Ar own Ar path Change owner of file .Ar path to .Ar own . .Ar path may contain .Xr glob 3 characters and may match multiple files. .Ar own must be a numeric UID. .It Xo Ic df .Op Fl hi .Op Ar path .Xc Display usage information for the filesystem holding the current directory (or .Ar path if specified). If the .Fl h flag is specified, the capacity information will be displayed using "human-readable" suffixes. The .Fl i flag requests display of inode information in addition to capacity information. This command is only supported on servers that implement the .Dq statvfs@openssh.com extension. .It Ic exit Quit .Nm sftp . .It Xo Ic get .Op Fl afPpr .Ar remote-path .Op Ar local-path .Xc Retrieve the .Ar remote-path and store it on the local machine. If the local path name is not specified, it is given the same name it has on the remote machine. .Ar remote-path may contain .Xr glob 3 characters and may match multiple files. If it does and .Ar local-path is specified, then .Ar local-path must specify a directory. .Pp If the .Fl a flag is specified, then attempt to resume partial transfers of existing files. Note that resumption assumes that any partial copy of the local file matches the remote copy. If the remote file contents differ from the partial local copy then the resultant file is likely to be corrupt. .Pp If the .Fl f flag is specified, then .Xr fsync 2 will be called after the file transfer has completed to flush the file to disk. .Pp If either the .Fl P or .Fl p flag is specified, then full file permissions and access times are copied too. .Pp If the .Fl r flag is specified then directories will be copied recursively. Note that .Nm does not follow symbolic links when performing recursive transfers. .It Ic help Display help text. .It Ic lcd Ar path Change local directory to .Ar path . .It Ic lls Op Ar ls-options Op Ar path Display local directory listing of either .Ar path or current directory if .Ar path is not specified. .Ar ls-options may contain any flags supported by the local system's .Xr ls 1 command. .Ar path may contain .Xr glob 3 characters and may match multiple files. .It Ic lmkdir Ar path Create local directory specified by .Ar path . .It Xo Ic ln .Op Fl s .Ar oldpath .Ar newpath .Xc Create a link from .Ar oldpath to .Ar newpath . If the .Fl s flag is specified the created link is a symbolic link, otherwise it is a hard link. .It Ic lpwd Print local working directory. .It Xo Ic ls .Op Fl 1afhlnrSt .Op Ar path .Xc Display a remote directory listing of either .Ar path or the current directory if .Ar path is not specified. .Ar path may contain .Xr glob 3 characters and may match multiple files. .Pp The following flags are recognized and alter the behaviour of .Ic ls accordingly: .Bl -tag -width Ds .It Fl 1 Produce single columnar output. .It Fl a List files beginning with a dot .Pq Sq \&. . .It Fl f Do not sort the listing. The default sort order is lexicographical. .It Fl h When used with a long format option, use unit suffixes: Byte, Kilobyte, Megabyte, Gigabyte, Terabyte, Petabyte, and Exabyte in order to reduce the number of digits to four or fewer using powers of 2 for sizes (K=1024, M=1048576, etc.). .It Fl l Display additional details including permissions and ownership information. .It Fl n Produce a long listing with user and group information presented numerically. .It Fl r Reverse the sort order of the listing. .It Fl S Sort the listing by file size. .It Fl t Sort the listing by last modification time. .El .It Ic lumask Ar umask Set local umask to .Ar umask . .It Ic mkdir Ar path Create remote directory specified by .Ar path . .It Ic progress Toggle display of progress meter. .It Xo Ic put .Op Fl fPpr .Ar local-path .Op Ar remote-path .Xc Upload .Ar local-path and store it on the remote machine. If the remote path name is not specified, it is given the same name it has on the local machine. .Ar local-path may contain .Xr glob 3 characters and may match multiple files. If it does and .Ar remote-path is specified, then .Ar remote-path must specify a directory. .Pp If the .Fl f flag is specified, then a request will be sent to the server to call .Xr fsync 2 after the file has been transferred. Note that this is only supported by servers that implement the "fsync@openssh.com" extension. .Pp If either the .Fl P or .Fl p flag is specified, then full file permissions and access times are copied too. .Pp If the .Fl r flag is specified then directories will be copied recursively. Note that .Nm does not follow symbolic links when performing recursive transfers. .It Ic pwd Display remote working directory. .It Ic quit Quit .Nm sftp . .It Xo Ic reget .Op Fl Ppr .Ar remote-path .Op Ar local-path .Xc Resume download of .Ar remote-path . Equivalent to .Ic get with the .Fl a flag set. .It Ic rename Ar oldpath Ar newpath Rename remote file from .Ar oldpath to .Ar newpath . .It Ic rm Ar path Delete remote file specified by .Ar path . .It Ic rmdir Ar path Remove remote directory specified by .Ar path . .It Ic symlink Ar oldpath Ar newpath Create a symbolic link from .Ar oldpath to .Ar newpath . .It Ic version Display the .Nm protocol version. .It Ic \&! Ns Ar command Execute .Ar command in local shell. .It Ic \&! Escape to local shell. .It Ic \&? Synonym for help. .El .Sh SEE ALSO .Xr ftp 1 , .Xr ls 1 , .Xr scp 1 , .Xr ssh 1 , .Xr ssh-add 1 , .Xr ssh-keygen 1 , .Xr glob 3 , .Xr ssh_config 5 , .Xr sftp-server 8 , .Xr sshd 8 .Rs .%A T. Ylonen .%A S. Lehtinen .%T "SSH File Transfer Protocol" .%N draft-ietf-secsh-filexfer-00.txt .%D January 2001 .%O work in progress material .Re Index: head/crypto/openssh/ssh-add.1 =================================================================== --- head/crypto/openssh/ssh-add.1 (revision 290670) +++ head/crypto/openssh/ssh-add.1 (revision 290671) @@ -1,202 +1,201 @@ .\" $OpenBSD: ssh-add.1,v 1.59 2013/12/07 11:58:46 naddy Exp $ -.\" $FreeBSD$ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd December 7, 2013 +.Dd $Mdocdate: December 7 2013 $ .Dt SSH-ADD 1 .Os .Sh NAME .Nm ssh-add .Nd adds private key identities to the authentication agent .Sh SYNOPSIS .Nm ssh-add .Op Fl cDdkLlXx .Op Fl t Ar life .Op Ar .Nm ssh-add .Fl s Ar pkcs11 .Nm ssh-add .Fl e Ar pkcs11 .Sh DESCRIPTION .Nm adds private key identities to the authentication agent, .Xr ssh-agent 1 . When run without arguments, it adds the files .Pa ~/.ssh/id_rsa , .Pa ~/.ssh/id_dsa , .Pa ~/.ssh/id_ecdsa , .Pa ~/.ssh/id_ed25519 and .Pa ~/.ssh/identity . After loading a private key, .Nm will try to load corresponding certificate information from the filename obtained by appending .Pa -cert.pub to the name of the private key file. Alternative file names can be given on the command line. .Pp If any file requires a passphrase, .Nm asks for the passphrase from the user. The passphrase is read from the user's tty. .Nm retries the last passphrase if multiple identity files are given. .Pp The authentication agent must be running and the .Ev SSH_AUTH_SOCK environment variable must contain the name of its socket for .Nm to work. .Pp The options are as follows: .Bl -tag -width Ds .It Fl c Indicates that added identities should be subject to confirmation before being used for authentication. Confirmation is performed by the .Ev SSH_ASKPASS program mentioned below. Successful confirmation is signaled by a zero exit status from the .Ev SSH_ASKPASS program, rather than text entered into the requester. .It Fl D Deletes all identities from the agent. .It Fl d Instead of adding identities, removes identities from the agent. If .Nm has been run without arguments, the keys for the default identities and their corresponding certificates will be removed. Otherwise, the argument list will be interpreted as a list of paths to public key files to specify keys and certificates to be removed from the agent. If no public key is found at a given path, .Nm will append .Pa .pub and retry. .It Fl e Ar pkcs11 Remove keys provided by the PKCS#11 shared library .Ar pkcs11 . .It Fl k When loading keys into or deleting keys from the agent, process plain private keys only and skip certificates. .It Fl L Lists public key parameters of all identities currently represented by the agent. .It Fl l Lists fingerprints of all identities currently represented by the agent. .It Fl s Ar pkcs11 Add keys provided by the PKCS#11 shared library .Ar pkcs11 . .It Fl t Ar life Set a maximum lifetime when adding identities to an agent. The lifetime may be specified in seconds or in a time format specified in .Xr sshd_config 5 . .It Fl X Unlock the agent. .It Fl x Lock the agent with a password. .El .Sh ENVIRONMENT .Bl -tag -width Ds .It Ev "DISPLAY" and "SSH_ASKPASS" If .Nm needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If .Nm does not have a terminal associated with it but .Ev DISPLAY and .Ev SSH_ASKPASS are set, it will execute the program specified by .Ev SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling .Nm from a .Pa .xsession or related script. (Note that on some machines it may be necessary to redirect the input from .Pa /dev/null to make this work.) .It Ev SSH_AUTH_SOCK Identifies the path of a .Ux Ns -domain socket used to communicate with the agent. .El .Sh FILES .Bl -tag -width Ds .It Pa ~/.ssh/identity Contains the protocol version 1 RSA authentication identity of the user. .It Pa ~/.ssh/id_dsa Contains the protocol version 2 DSA authentication identity of the user. .It Pa ~/.ssh/id_ecdsa Contains the protocol version 2 ECDSA authentication identity of the user. .It Pa ~/.ssh/id_ed25519 Contains the protocol version 2 ED25519 authentication identity of the user. .It Pa ~/.ssh/id_rsa Contains the protocol version 2 RSA authentication identity of the user. .El .Pp Identity files should not be readable by anyone but the user. Note that .Nm ignores identity files if they are accessible by others. .Sh EXIT STATUS Exit status is 0 on success, 1 if the specified command fails, and 2 if .Nm is unable to contact the authentication agent. .Sh SEE ALSO .Xr ssh 1 , .Xr ssh-agent 1 , .Xr ssh-keygen 1 , .Xr sshd 8 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Index: head/crypto/openssh/ssh-keygen.1 =================================================================== --- head/crypto/openssh/ssh-keygen.1 (revision 290670) +++ head/crypto/openssh/ssh-keygen.1 (revision 290671) @@ -1,855 +1,854 @@ .\" $OpenBSD: ssh-keygen.1,v 1.120 2014/02/05 20:13:25 naddy Exp $ -.\" $FreeBSD$ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd February 5, 2014 +.Dd $Mdocdate: February 5 2014 $ .Dt SSH-KEYGEN 1 .Os .Sh NAME .Nm ssh-keygen .Nd authentication key generation, management and conversion .Sh SYNOPSIS .Bk -words .Nm ssh-keygen .Op Fl q .Op Fl b Ar bits .Op Fl t Ar type .Op Fl N Ar new_passphrase .Op Fl C Ar comment .Op Fl f Ar output_keyfile .Nm ssh-keygen .Fl p .Op Fl P Ar old_passphrase .Op Fl N Ar new_passphrase .Op Fl f Ar keyfile .Nm ssh-keygen .Fl i .Op Fl m Ar key_format .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl e .Op Fl m Ar key_format .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl y .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl c .Op Fl P Ar passphrase .Op Fl C Ar comment .Op Fl f Ar keyfile .Nm ssh-keygen .Fl l .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl B .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl D Ar pkcs11 .Nm ssh-keygen .Fl F Ar hostname .Op Fl f Ar known_hosts_file .Op Fl l .Nm ssh-keygen .Fl H .Op Fl f Ar known_hosts_file .Nm ssh-keygen .Fl R Ar hostname .Op Fl f Ar known_hosts_file .Nm ssh-keygen .Fl r Ar hostname .Op Fl f Ar input_keyfile .Op Fl g .Nm ssh-keygen .Fl G Ar output_file .Op Fl v .Op Fl b Ar bits .Op Fl M Ar memory .Op Fl S Ar start_point .Nm ssh-keygen .Fl T Ar output_file .Fl f Ar input_file .Op Fl v .Op Fl a Ar rounds .Op Fl J Ar num_lines .Op Fl j Ar start_line .Op Fl K Ar checkpt .Op Fl W Ar generator .Nm ssh-keygen .Fl s Ar ca_key .Fl I Ar certificate_identity .Op Fl h .Op Fl n Ar principals .Op Fl O Ar option .Op Fl V Ar validity_interval .Op Fl z Ar serial_number .Ar .Nm ssh-keygen .Fl L .Op Fl f Ar input_keyfile .Nm ssh-keygen .Fl A .Nm ssh-keygen .Fl k .Fl f Ar krl_file .Op Fl u .Op Fl s Ar ca_public .Op Fl z Ar version_number .Ar .Nm ssh-keygen .Fl Q .Fl f Ar krl_file .Ar .Ek .Sh DESCRIPTION .Nm generates, manages and converts authentication keys for .Xr ssh 1 . .Nm can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA, ED25519 or RSA keys for use by SSH protocol version 2. The type of key to be generated is specified with the .Fl t option. If invoked without any arguments, .Nm will generate an RSA key for use in SSH protocol 2 connections. .Pp .Nm is also used to generate groups for use in Diffie-Hellman group exchange (DH-GEX). See the .Sx MODULI GENERATION section for details. .Pp Finally, .Nm can be used to generate and update Key Revocation Lists, and to test whether given keys have been revoked by one. See the .Sx KEY REVOCATION LISTS section for details. .Pp Normally each user wishing to use SSH with public key authentication runs this once to create the authentication key in .Pa ~/.ssh/identity , .Pa ~/.ssh/id_dsa , .Pa ~/.ssh/id_ecdsa , .Pa ~/.ssh/id_ed25519 or .Pa ~/.ssh/id_rsa . Additionally, the system administrator may use this to generate host keys, as seen in .Pa /etc/rc . .Pp Normally this program generates the key and asks for a file in which to store the private key. The public key is stored in a file with the same name but .Dq .pub appended. The program also asks for a passphrase. The passphrase may be empty to indicate no passphrase (host keys must have an empty passphrase), or it may be a string of arbitrary length. A passphrase is similar to a password, except it can be a phrase with a series of words, punctuation, numbers, whitespace, or any string of characters you want. Good passphrases are 10-30 characters long, are not simple sentences or otherwise easily guessable (English prose has only 1-2 bits of entropy per character, and provides very bad passphrases), and contain a mix of upper and lowercase letters, numbers, and non-alphanumeric characters. The passphrase can be changed later by using the .Fl p option. .Pp There is no way to recover a lost passphrase. If the passphrase is lost or forgotten, a new key must be generated and the corresponding public key copied to other machines. .Pp For RSA1 keys, there is also a comment field in the key file that is only for convenience to the user to help identify the key. The comment can tell what the key is for, or whatever is useful. The comment is initialized to .Dq user@host when the key is created, but can be changed using the .Fl c option. .Pp After a key is generated, instructions below detail where the keys should be placed to be activated. .Pp The options are as follows: .Bl -tag -width Ds .It Fl A For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519) for which host keys do not exist, generate the host keys with the default key file path, an empty passphrase, default bits for the key type, and default comment. This is used by .Pa /etc/rc to generate new host keys. .It Fl a Ar rounds When saving a new-format private key (i.e. an ed25519 key or any SSH protocol 2 key when the .Fl o flag is set), this option specifies the number of KDF (key derivation function) rounds used. Higher numbers result in slower passphrase verification and increased resistance to brute-force password cracking (should the keys be stolen). .Pp When screening DH-GEX candidates ( using the .Fl T command). This option specifies the number of primality tests to perform. .It Fl B Show the bubblebabble digest of specified private or public key file. .It Fl b Ar bits Specifies the number of bits in the key to create. For RSA keys, the minimum size is 768 bits and the default is 2048 bits. Generally, 2048 bits is considered sufficient. DSA keys must be exactly 1024 bits as specified by FIPS 186-2. For ECDSA keys, the .Fl b flag determines the key length by selecting from one of three elliptic curve sizes: 256, 384 or 521 bits. Attempting to use bit lengths other than these three values for ECDSA keys will fail. ED25519 keys have a fixed length and the .Fl b flag will be ignored. .It Fl C Ar comment Provides a new comment. .It Fl c Requests changing the comment in the private and public key files. This operation is only supported for RSA1 keys. The program will prompt for the file containing the private keys, for the passphrase if the key has one, and for the new comment. .It Fl D Ar pkcs11 Download the RSA public keys provided by the PKCS#11 shared library .Ar pkcs11 . When used in combination with .Fl s , this option indicates that a CA key resides in a PKCS#11 token (see the .Sx CERTIFICATES section for details). .It Fl e This option will read a private or public OpenSSH key file and print to stdout the key in one of the formats specified by the .Fl m option. The default export format is .Dq RFC4716 . This option allows exporting OpenSSH keys for use by other programs, including several commercial SSH implementations. .It Fl F Ar hostname Search for the specified .Ar hostname in a .Pa known_hosts file, listing any occurrences found. This option is useful to find hashed host names or addresses and may also be used in conjunction with the .Fl H option to print found keys in a hashed format. .It Fl f Ar filename Specifies the filename of the key file. .It Fl G Ar output_file Generate candidate primes for DH-GEX. These primes must be screened for safety (using the .Fl T option) before use. .It Fl g Use generic DNS format when printing fingerprint resource records using the .Fl r command. .It Fl H Hash a .Pa known_hosts file. This replaces all hostnames and addresses with hashed representations within the specified file; the original content is moved to a file with a .old suffix. These hashes may be used normally by .Nm ssh and .Nm sshd , but they do not reveal identifying information should the file's contents be disclosed. This option will not modify existing hashed hostnames and is therefore safe to use on files that mix hashed and non-hashed names. .It Fl h When signing a key, create a host certificate instead of a user certificate. Please see the .Sx CERTIFICATES section for details. .It Fl I Ar certificate_identity Specify the key identity when signing a public key. Please see the .Sx CERTIFICATES section for details. .It Fl i This option will read an unencrypted private (or public) key file in the format specified by the .Fl m option and print an OpenSSH compatible private (or public) key to stdout. .It Fl J Ar num_lines Exit after screening the specified number of lines while performing DH candidate screening using the .Fl T option. .It Fl j Ar start_line Start screening at the specified line number while performing DH candidate screening using the .Fl T option. .It Fl K Ar checkpt Write the last line processed to the file .Ar checkpt while performing DH candidate screening using the .Fl T option. This will be used to skip lines in the input file that have already been processed if the job is restarted. This option allows importing keys from other software, including several commercial SSH implementations. The default import format is .Dq RFC4716 . .It Fl k Generate a KRL file. In this mode, .Nm will generate a KRL file at the location specified via the .Fl f flag that revokes every key or certificate presented on the command line. Keys/certificates to be revoked may be specified by public key file or using the format described in the .Sx KEY REVOCATION LISTS section. .It Fl L Prints the contents of a certificate. .It Fl l Show fingerprint of specified public key file. Private RSA1 keys are also supported. For RSA and DSA keys .Nm tries to find the matching public key file and prints its fingerprint. If combined with .Fl v , an ASCII art representation of the key is supplied with the fingerprint. .It Fl M Ar memory Specify the amount of memory to use (in megabytes) when generating candidate moduli for DH-GEX. .It Fl m Ar key_format Specify a key format for the .Fl i (import) or .Fl e (export) conversion options. The supported key formats are: .Dq RFC4716 (RFC 4716/SSH2 public or private key), .Dq PKCS8 (PEM PKCS8 public key) or .Dq PEM (PEM public key). The default conversion format is .Dq RFC4716 . .It Fl N Ar new_passphrase Provides the new passphrase. .It Fl n Ar principals Specify one or more principals (user or host names) to be included in a certificate when signing a key. Multiple principals may be specified, separated by commas. Please see the .Sx CERTIFICATES section for details. .It Fl O Ar option Specify a certificate option when signing a key. This option may be specified multiple times. Please see the .Sx CERTIFICATES section for details. The options that are valid for user certificates are: .Bl -tag -width Ds .It Ic clear Clear all enabled permissions. This is useful for clearing the default set of permissions so permissions may be added individually. .It Ic force-command Ns = Ns Ar command Forces the execution of .Ar command instead of any shell or command specified by the user when the certificate is used for authentication. .It Ic no-agent-forwarding Disable .Xr ssh-agent 1 forwarding (permitted by default). .It Ic no-port-forwarding Disable port forwarding (permitted by default). .It Ic no-pty Disable PTY allocation (permitted by default). .It Ic no-user-rc Disable execution of .Pa ~/.ssh/rc by .Xr sshd 8 (permitted by default). .It Ic no-x11-forwarding Disable X11 forwarding (permitted by default). .It Ic permit-agent-forwarding Allows .Xr ssh-agent 1 forwarding. .It Ic permit-port-forwarding Allows port forwarding. .It Ic permit-pty Allows PTY allocation. .It Ic permit-user-rc Allows execution of .Pa ~/.ssh/rc by .Xr sshd 8 . .It Ic permit-x11-forwarding Allows X11 forwarding. .It Ic source-address Ns = Ns Ar address_list Restrict the source addresses from which the certificate is considered valid. The .Ar address_list is a comma-separated list of one or more address/netmask pairs in CIDR format. .El .Pp At present, no options are valid for host keys. .It Fl o Causes .Nm to save SSH protocol 2 private keys using the new OpenSSH format rather than the more compatible PEM format. The new format has increased resistance to brute-force password cracking but is not supported by versions of OpenSSH prior to 6.5. Ed25519 keys always use the new private key format. .It Fl P Ar passphrase Provides the (old) passphrase. .It Fl p Requests changing the passphrase of a private key file instead of creating a new private key. The program will prompt for the file containing the private key, for the old passphrase, and twice for the new passphrase. .It Fl Q Test whether keys have been revoked in a KRL. .It Fl q Silence .Nm ssh-keygen . .It Fl R Ar hostname Removes all keys belonging to .Ar hostname from a .Pa known_hosts file. This option is useful to delete hashed hosts (see the .Fl H option above). .It Fl r Ar hostname Print the SSHFP fingerprint resource record named .Ar hostname for the specified public key file. .It Fl S Ar start Specify start point (in hex) when generating candidate moduli for DH-GEX. .It Fl s Ar ca_key Certify (sign) a public key using the specified CA key. Please see the .Sx CERTIFICATES section for details. .Pp When generating a KRL, .Fl s specifies a path to a CA public key file used to revoke certificates directly by key ID or serial number. See the .Sx KEY REVOCATION LISTS section for details. .It Fl T Ar output_file Test DH group exchange candidate primes (generated using the .Fl G option) for safety. .It Fl t Ar type Specifies the type of key to create. The possible values are .Dq rsa1 for protocol version 1 and .Dq dsa , .Dq ecdsa , .Dq ed25519 , or .Dq rsa for protocol version 2. .It Fl u Update a KRL. When specified with .Fl k , keys listed via the command line are added to the existing KRL rather than a new KRL being created. .It Fl V Ar validity_interval Specify a validity interval when signing a certificate. A validity interval may consist of a single time, indicating that the certificate is valid beginning now and expiring at that time, or may consist of two times separated by a colon to indicate an explicit time interval. The start time may be specified as a date in YYYYMMDD format, a time in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting of a minus sign followed by a relative time in the format described in the TIME FORMATS section of .Xr sshd_config 5 . The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or a relative time starting with a plus character. .Pp For example: .Dq +52w1d (valid from now to 52 weeks and one day from now), .Dq -4w:+4w (valid from four weeks ago to four weeks from now), .Dq 20100101123000:20110101123000 (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), .Dq -1d:20110101 (valid from yesterday to midnight, January 1st, 2011). .It Fl v Verbose mode. Causes .Nm to print debugging messages about its progress. This is helpful for debugging moduli generation. Multiple .Fl v options increase the verbosity. The maximum is 3. .It Fl W Ar generator Specify desired generator when testing candidate moduli for DH-GEX. .It Fl y This option will read a private OpenSSH format file and print an OpenSSH public key to stdout. .It Fl z Ar serial_number Specifies a serial number to be embedded in the certificate to distinguish this certificate from others from the same CA. The default serial number is zero. .Pp When generating a KRL, the .Fl z flag is used to specify a KRL version number. .El .Sh MODULI GENERATION .Nm may be used to generate groups for the Diffie-Hellman Group Exchange (DH-GEX) protocol. Generating these groups is a two-step process: first, candidate primes are generated using a fast, but memory intensive process. These candidate primes are then tested for suitability (a CPU-intensive process). .Pp Generation of primes is performed using the .Fl G option. The desired length of the primes may be specified by the .Fl b option. For example: .Pp .Dl # ssh-keygen -G moduli-2048.candidates -b 2048 .Pp By default, the search for primes begins at a random point in the desired length range. This may be overridden using the .Fl S option, which specifies a different start point (in hex). .Pp Once a set of candidates have been generated, they must be screened for suitability. This may be performed using the .Fl T option. In this mode .Nm will read candidates from standard input (or a file specified using the .Fl f option). For example: .Pp .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates .Pp By default, each candidate will be subjected to 100 primality tests. This may be overridden using the .Fl a option. The DH generator value will be chosen automatically for the prime under consideration. If a specific generator is desired, it may be requested using the .Fl W option. Valid generator values are 2, 3, and 5. .Pp Screened DH groups may be installed in .Pa /etc/moduli . It is important that this file contains moduli of a range of bit lengths and that both ends of a connection share common moduli. .Sh CERTIFICATES .Nm supports signing of keys to produce certificates that may be used for user or host authentication. Certificates consist of a public key, some identity information, zero or more principal (user or host) names and a set of options that are signed by a Certification Authority (CA) key. Clients or servers may then trust only the CA key and verify its signature on a certificate rather than trusting many user/host keys. Note that OpenSSH certificates are a different, and much simpler, format to the X.509 certificates used in .Xr ssl 8 . .Pp .Nm supports two types of certificates: user and host. User certificates authenticate users to servers, whereas host certificates authenticate server hosts to users. To generate a user certificate: .Pp .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub .Pp The resultant certificate will be placed in .Pa /path/to/user_key-cert.pub . A host certificate requires the .Fl h option: .Pp .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub .Pp The host certificate will be output to .Pa /path/to/host_key-cert.pub . .Pp It is possible to sign using a CA key stored in a PKCS#11 token by providing the token library using .Fl D and identifying the CA key by providing its public half as an argument to .Fl s : .Pp .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub .Pp In all cases, .Ar key_id is a "key identifier" that is logged by the server when the certificate is used for authentication. .Pp Certificates may be limited to be valid for a set of principal (user/host) names. By default, generated certificates are valid for all users or hosts. To generate a certificate for a specified set of principals: .Pp .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub" .Pp Additional limitations on the validity and use of user certificates may be specified through certificate options. A certificate option may disable features of the SSH session, may be valid only when presented from particular source addresses or may force the use of a specific command. For a list of valid certificate options, see the documentation for the .Fl O option above. .Pp Finally, certificates may be defined with a validity lifetime. The .Fl V option allows specification of certificate start and end times. A certificate that is presented at a time outside this range will not be considered valid. By default, certificates are valid from .Ux Epoch to the distant future. .Pp For certificates to be used for user or host authentication, the CA public key must be trusted by .Xr sshd 8 or .Xr ssh 1 . Please refer to those manual pages for details. .Sh KEY REVOCATION LISTS .Nm is able to manage OpenSSH format Key Revocation Lists (KRLs). These binary files specify keys or certificates to be revoked using a compact format, taking as little as one bit per certificate if they are being revoked by serial number. .Pp KRLs may be generated using the .Fl k flag. This option reads one or more files from the command line and generates a new KRL. The files may either contain a KRL specification (see below) or public keys, listed one per line. Plain public keys are revoked by listing their hash or contents in the KRL and certificates revoked by serial number or key ID (if the serial is zero or not available). .Pp Revoking keys using a KRL specification offers explicit control over the types of record used to revoke keys and may be used to directly revoke certificates by serial number or key ID without having the complete original certificate on hand. A KRL specification consists of lines containing one of the following directives followed by a colon and some directive-specific information. .Bl -tag -width Ds .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number Revokes a certificate with the specified serial number. Serial numbers are 64-bit values, not including zero and may be expressed in decimal, hex or octal. If two serial numbers are specified separated by a hyphen, then the range of serial numbers including and between each is revoked. The CA key must have been specified on the .Nm command line using the .Fl s option. .It Cm id : Ar key_id Revokes a certificate with the specified key ID string. The CA key must have been specified on the .Nm command line using the .Fl s option. .It Cm key : Ar public_key Revokes the specified key. If a certificate is listed, then it is revoked as a plain public key. .It Cm sha1 : Ar public_key Revokes the specified key by its SHA1 hash. .El .Pp KRLs may be updated using the .Fl u flag in addition to .Fl k . When this option is specified, keys listed via the command line are merged into the KRL, adding to those already there. .Pp It is also possible, given a KRL, to test whether it revokes a particular key (or keys). The .Fl Q flag will query an existing KRL, testing each key specified on the commandline. If any key listed on the command line has been revoked (or an error encountered) then .Nm will exit with a non-zero exit status. A zero exit status will only be returned if no key was revoked. .Sh FILES .Bl -tag -width Ds -compact .It Pa ~/.ssh/identity Contains the protocol version 1 RSA authentication identity of the user. This file should not be readable by anyone but the user. It is possible to specify a passphrase when generating the key; that passphrase will be used to encrypt the private part of this file using 3DES. This file is not automatically accessed by .Nm but it is offered as the default file for the private key. .Xr ssh 1 will read this file when a login attempt is made. .Pp .It Pa ~/.ssh/identity.pub Contains the protocol version 1 RSA public key for authentication. The contents of this file should be added to .Pa ~/.ssh/authorized_keys on all machines where the user wishes to log in using RSA authentication. There is no need to keep the contents of this file secret. .Pp .It Pa ~/.ssh/id_dsa .It Pa ~/.ssh/id_ecdsa .It Pa ~/.ssh/id_ed25519 .It Pa ~/.ssh/id_rsa Contains the protocol version 2 DSA, ECDSA, ED25519 or RSA authentication identity of the user. This file should not be readable by anyone but the user. It is possible to specify a passphrase when generating the key; that passphrase will be used to encrypt the private part of this file using 128-bit AES. This file is not automatically accessed by .Nm but it is offered as the default file for the private key. .Xr ssh 1 will read this file when a login attempt is made. .Pp .It Pa ~/.ssh/id_dsa.pub .It Pa ~/.ssh/id_ecdsa.pub .It Pa ~/.ssh/id_ed25519.pub .It Pa ~/.ssh/id_rsa.pub Contains the protocol version 2 DSA, ECDSA, ED25519 or RSA public key for authentication. The contents of this file should be added to .Pa ~/.ssh/authorized_keys on all machines where the user wishes to log in using public key authentication. There is no need to keep the contents of this file secret. .Pp .It Pa /etc/moduli Contains Diffie-Hellman groups used for DH-GEX. The file format is described in .Xr moduli 5 . .El .Sh SEE ALSO .Xr ssh 1 , .Xr ssh-add 1 , .Xr ssh-agent 1 , .Xr moduli 5 , .Xr sshd 8 .Rs .%R RFC 4716 .%T "The Secure Shell (SSH) Public Key File Format" .%D 2006 .Re .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Index: head/crypto/openssh/ssh-keyscan.1 =================================================================== --- head/crypto/openssh/ssh-keyscan.1 (revision 290670) +++ head/crypto/openssh/ssh-keyscan.1 (revision 290671) @@ -1,178 +1,177 @@ .\" $OpenBSD: ssh-keyscan.1,v 1.34 2014/01/28 14:13:39 jmc Exp $ -.\" $FreeBSD$ .\" .\" Copyright 1995, 1996 by David Mazieres . .\" .\" Modification and redistribution in source and binary forms is .\" permitted provided that due credit is given to the author and the .\" OpenBSD project by leaving this copyright notice intact. .\" -.Dd January 28, 2014 +.Dd $Mdocdate: January 28 2014 $ .Dt SSH-KEYSCAN 1 .Os .Sh NAME .Nm ssh-keyscan .Nd gather ssh public keys .Sh SYNOPSIS .Nm ssh-keyscan .Bk -words .Op Fl 46Hv .Op Fl f Ar file .Op Fl p Ar port .Op Fl T Ar timeout .Op Fl t Ar type .Op Ar host | addrlist namelist .Ar ... .Ek .Sh DESCRIPTION .Nm is a utility for gathering the public ssh host keys of a number of hosts. It was designed to aid in building and verifying .Pa ssh_known_hosts files. .Nm provides a minimal interface suitable for use by shell and perl scripts. .Pp .Nm uses non-blocking socket I/O to contact as many hosts as possible in parallel, so it is very efficient. The keys from a domain of 1,000 hosts can be collected in tens of seconds, even when some of those hosts are down or do not run ssh. For scanning, one does not need login access to the machines that are being scanned, nor does the scanning process involve any encryption. .Pp The options are as follows: .Bl -tag -width Ds .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl f Ar file Read hosts or .Dq addrlist namelist pairs from .Ar file , one per line. If .Pa - is supplied instead of a filename, .Nm will read hosts or .Dq addrlist namelist pairs from the standard input. .It Fl H Hash all hostnames and addresses in the output. Hashed names may be used normally by .Nm ssh and .Nm sshd , but they do not reveal identifying information should the file's contents be disclosed. .It Fl p Ar port Port to connect to on the remote host. .It Fl T Ar timeout Set the timeout for connection attempts. If .Ar timeout seconds have elapsed since a connection was initiated to a host or since the last time anything was read from that host, then the connection is closed and the host in question considered unavailable. Default is 5 seconds. .It Fl t Ar type Specifies the type of the key to fetch from the scanned hosts. The possible values are .Dq rsa1 for protocol version 1 and .Dq dsa , .Dq ecdsa , .Dq ed25519 , or .Dq rsa for protocol version 2. Multiple values may be specified by separating them with commas. The default is to fetch .Dq rsa and .Dq ecdsa keys. .It Fl v Verbose mode. Causes .Nm to print debugging messages about its progress. .El .Sh SECURITY If an ssh_known_hosts file is constructed using .Nm without verifying the keys, users will be vulnerable to .Em man in the middle attacks. On the other hand, if the security model allows such a risk, .Nm can help in the detection of tampered keyfiles or man in the middle attacks which have begun after the ssh_known_hosts file was created. .Sh FILES Input format: .Bd -literal 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4 .Ed .Pp Output format for rsa1 keys: .Bd -literal host-or-namelist bits exponent modulus .Ed .Pp Output format for rsa, dsa and ecdsa keys: .Bd -literal host-or-namelist keytype base64-encoded-key .Ed .Pp Where .Ar keytype is either .Dq ecdsa-sha2-nistp256 , .Dq ecdsa-sha2-nistp384 , .Dq ecdsa-sha2-nistp521 , .Dq ssh-ed25519 , .Dq ssh-dss or .Dq ssh-rsa . .Pp .Pa /etc/ssh/ssh_known_hosts .Sh EXAMPLES Print the rsa host key for machine .Ar hostname : .Bd -literal $ ssh-keyscan hostname .Ed .Pp Find all hosts from the file .Pa ssh_hosts which have new or different keys from those in the sorted file .Pa ssh_known_hosts : .Bd -literal $ ssh-keyscan -t rsa,dsa,ecdsa -f ssh_hosts | \e sort -u - ssh_known_hosts | diff ssh_known_hosts - .Ed .Sh SEE ALSO .Xr ssh 1 , .Xr sshd 8 .Sh AUTHORS .An -nosplit .An David Mazieres Aq Mt dm@lcs.mit.edu wrote the initial version, and .An Wayne Davison Aq Mt wayned@users.sourceforge.net added support for protocol version 2. .Sh BUGS It generates "Connection closed by remote host" messages on the consoles of all the machines it scans if the server is older than version 2.9. This is because it opens a connection to the ssh port, reads the public key, and drops the connection as soon as it gets the key. Index: head/crypto/openssh/ssh-keysign.8 =================================================================== --- head/crypto/openssh/ssh-keysign.8 (revision 290670) +++ head/crypto/openssh/ssh-keysign.8 (revision 290671) @@ -1,94 +1,93 @@ .\" $OpenBSD: ssh-keysign.8,v 1.14 2013/12/07 11:58:46 naddy Exp $ -.\" $FreeBSD$ .\" .\" Copyright (c) 2002 Markus Friedl. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd December 7, 2013 +.Dd $Mdocdate: December 7 2013 $ .Dt SSH-KEYSIGN 8 .Os .Sh NAME .Nm ssh-keysign .Nd ssh helper program for host-based authentication .Sh SYNOPSIS .Nm .Sh DESCRIPTION .Nm is used by .Xr ssh 1 to access the local host keys and generate the digital signature required during host-based authentication with SSH protocol version 2. .Pp .Nm is disabled by default and can only be enabled in the global client configuration file .Pa /etc/ssh/ssh_config by setting .Cm EnableSSHKeysign to .Dq yes . .Pp .Nm is not intended to be invoked by the user, but from .Xr ssh 1 . See .Xr ssh 1 and .Xr sshd 8 for more information about host-based authentication. .Sh FILES .Bl -tag -width Ds -compact .It Pa /etc/ssh/ssh_config Controls whether .Nm is enabled. .Pp .It Pa /etc/ssh/ssh_host_dsa_key .It Pa /etc/ssh/ssh_host_ecdsa_key .It Pa /etc/ssh/ssh_host_ed25519_key .It Pa /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys used to generate the digital signature. They should be owned by root, readable only by root, and not accessible to others. Since they are readable only by root, .Nm must be set-uid root if host-based authentication is used. .Pp .It Pa /etc/ssh/ssh_host_dsa_key-cert.pub .It Pa /etc/ssh/ssh_host_ecdsa_key-cert.pub .It Pa /etc/ssh/ssh_host_ed25519_key-cert.pub .It Pa /etc/ssh/ssh_host_rsa_key-cert.pub If these files exist they are assumed to contain public certificate information corresponding with the private keys above. .El .Sh SEE ALSO .Xr ssh 1 , .Xr ssh-keygen 1 , .Xr ssh_config 5 , .Xr sshd 8 .Sh HISTORY .Nm first appeared in .Ox 3.2 . .Sh AUTHORS .An Markus Friedl Aq Mt markus@openbsd.org Index: head/crypto/openssh/ssh-pkcs11-helper.8 =================================================================== --- head/crypto/openssh/ssh-pkcs11-helper.8 (revision 290670) +++ head/crypto/openssh/ssh-pkcs11-helper.8 (revision 290671) @@ -1,44 +1,43 @@ .\" $OpenBSD: ssh-pkcs11-helper.8,v 1.4 2013/07/16 00:07:52 schwarze Exp $ -.\" $FreeBSD$ .\" .\" Copyright (c) 2010 Markus Friedl. All rights reserved. .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" -.Dd July 16, 2013 +.Dd $Mdocdate: July 16 2013 $ .Dt SSH-PKCS11-HELPER 8 .Os .Sh NAME .Nm ssh-pkcs11-helper .Nd ssh-agent helper program for PKCS#11 support .Sh SYNOPSIS .Nm .Sh DESCRIPTION .Nm is used by .Xr ssh-agent 1 to access keys provided by a PKCS#11 token. .Pp .Nm is not intended to be invoked by the user, but from .Xr ssh-agent 1 . .Sh SEE ALSO .Xr ssh 1 , .Xr ssh-add 1 , .Xr ssh-agent 1 .Sh HISTORY .Nm first appeared in .Ox 4.7 . .Sh AUTHORS .An Markus Friedl Aq Mt markus@openbsd.org Index: head/crypto/openssh/ssh.1 =================================================================== --- head/crypto/openssh/ssh.1 (revision 290670) +++ head/crypto/openssh/ssh.1 (revision 290671) @@ -1,1595 +1,1595 @@ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: ssh.1,v 1.343 2013/12/07 11:58:46 naddy Exp $ .\" $FreeBSD$ -.Dd December 7, 2013 +.Dd $Mdocdate: December 7 2013 $ .Dt SSH 1 .Os .Sh NAME .Nm ssh .Nd OpenSSH SSH client (remote login program) .Sh SYNOPSIS .Nm ssh .Bk -words .Op Fl 1246AaCfgKkMNnqsTtVvXxYy .Op Fl b Ar bind_address .Op Fl c Ar cipher_spec .Op Fl D Oo Ar bind_address : Oc Ns Ar port .Op Fl E Ar log_file .Op Fl e Ar escape_char .Op Fl F Ar configfile .Op Fl I Ar pkcs11 .Op Fl i Ar identity_file .Op Fl L Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport .Op Fl l Ar login_name .Op Fl m Ar mac_spec .Op Fl O Ar ctl_cmd .Op Fl o Ar option .Op Fl p Ar port .Op Fl Q Cm cipher | cipher-auth | mac | kex | key .Op Fl R Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport .Op Fl S Ar ctl_path .Op Fl W Ar host : Ns Ar port .Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun .Oo Ar user Ns @ Oc Ns Ar hostname .Op Ar command .Ek .Sh DESCRIPTION .Nm (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to replace rlogin and rsh, and provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections and arbitrary TCP ports can also be forwarded over the secure channel. .Pp .Nm connects and logs into the specified .Ar hostname (with optional .Ar user name). The user must prove his/her identity to the remote machine using one of several methods depending on the protocol version used (see below). .Pp If .Ar command is specified, it is executed on the remote host instead of a login shell. .Pp The options are as follows: .Bl -tag -width Ds .It Fl 1 Forces .Nm to try protocol version 1 only. .It Fl 2 Forces .Nm to try protocol version 2 only. .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl A Enables forwarding of the authentication agent connection. This can also be specified on a per-host basis in a configuration file. .Pp Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's .Ux Ns -domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. .It Fl a Disables forwarding of the authentication agent connection. .It Fl b Ar bind_address Use .Ar bind_address on the local machine as the source address of the connection. Only useful on systems with more than one address. .It Fl C Requests compression of all data (including stdin, stdout, stderr, and data for forwarded X11 and TCP connections). The compression algorithm is the same used by .Xr gzip 1 , and the .Dq level can be controlled by the .Cm CompressionLevel option for protocol version 1. Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the .Cm Compression option. .It Fl c Ar cipher_spec Selects the cipher specification for encrypting the session. .Pp Protocol version 1 allows specification of a single cipher. The supported values are .Dq 3des , .Dq blowfish , and .Dq des . .Ar 3des (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. It is believed to be secure. .Ar blowfish is a fast block cipher; it appears very secure and is much faster than .Ar 3des . .Ar des is only supported in the .Nm client for interoperability with legacy protocol 1 implementations that do not support the .Ar 3des cipher. Its use is strongly discouraged due to cryptographic weaknesses. The default is .Dq 3des . .Pp For protocol version 2, .Ar cipher_spec is a comma-separated list of ciphers listed in order of preference. See the .Cm Ciphers keyword in .Xr ssh_config 5 for more information. .It Fl D Xo .Sm off .Oo Ar bind_address : Oc .Ar port .Sm on .Xc Specifies a local .Dq dynamic application-level port forwarding. This works by allocating a socket to listen to .Ar port on the local side, optionally bound to the specified .Ar bind_address . Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and .Nm will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file. .Pp IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .It Fl E Ar log_file Append debug logs to .Ar log_file instead of standard error. .It Fl e Ar escape_char Sets the escape character for sessions with a pty (default: .Ql ~ ) . The escape character is only recognized at the beginning of a line. The escape character followed by a dot .Pq Ql \&. closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to .Dq none disables any escapes and makes the session fully transparent. .It Fl F Ar configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file .Pq Pa /etc/ssh/ssh_config will be ignored. The default for the per-user configuration file is .Pa ~/.ssh/config . .It Fl f Requests .Nm to go to background just before command execution. This is useful if .Nm is going to ask for passwords or passphrases, but the user wants it in the background. This implies .Fl n . The recommended way to start X11 programs at a remote site is with something like .Ic ssh -f host xterm . .Pp If the .Cm ExitOnForwardFailure configuration option is set to .Dq yes , then a client started with .Fl f will wait for all remote port forwards to be successfully established before placing itself in the background. .It Fl g Allows remote hosts to connect to local forwarded ports. .It Fl I Ar pkcs11 Specify the PKCS#11 shared library .Nm should use to communicate with a PKCS#11 token providing the user's private RSA key. .It Fl i Ar identity_file Selects a file from which the identity (private key) for public key authentication is read. The default is .Pa ~/.ssh/identity for protocol version 1, and .Pa ~/.ssh/id_dsa , .Pa ~/.ssh/id_ecdsa , .Pa ~/.ssh/id_ed25519 and .Pa ~/.ssh/id_rsa for protocol version 2. Identity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple .Fl i options (and multiple identities specified in configuration files). .Nm will also try to load certificate information from the filename obtained by appending .Pa -cert.pub to identity filenames. .It Fl K Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI credentials to the server. .It Fl k Disables forwarding (delegation) of GSSAPI credentials to the server. .It Fl L Xo .Sm off .Oo Ar bind_address : Oc .Ar port : host : hostport .Sm on .Xc Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side. This works by allocating a socket to listen to .Ar port on the local side, optionally bound to the specified .Ar bind_address . Whenever a connection is made to this port, the connection is forwarded over the secure channel, and a connection is made to .Ar host port .Ar hostport from the remote machine. Port forwardings can also be specified in the configuration file. IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .It Fl l Ar login_name Specifies the user to log in as on the remote machine. This also may be specified on a per-host basis in the configuration file. .It Fl M Places the .Nm client into .Dq master mode for connection sharing. Multiple .Fl M options places .Nm into .Dq master mode with confirmation required before slave connections are accepted. Refer to the description of .Cm ControlMaster in .Xr ssh_config 5 for details. .It Fl m Ar mac_spec Additionally, for protocol version 2 a comma-separated list of MAC (message authentication code) algorithms can be specified in order of preference. See the .Cm MACs keyword for more information. .It Fl N Do not execute a remote command. This is useful for just forwarding ports (protocol version 2 only). .It Fl n Redirects stdin from .Pa /dev/null (actually, prevents reading from stdin). This must be used when .Nm is run in the background. A common trick is to use this to run X11 programs on a remote machine. For example, .Ic ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. The .Nm program will be put in the background. (This does not work if .Nm needs to ask for a password or passphrase; see also the .Fl f option.) .It Fl O Ar ctl_cmd Control an active connection multiplexing master process. When the .Fl O option is specified, the .Ar ctl_cmd argument is interpreted and passed to the master process. Valid commands are: .Dq check (check that the master process is running), .Dq forward (request forwardings without command execution), .Dq cancel (cancel forwardings), .Dq exit (request the master to exit), and .Dq stop (request the master to stop accepting further multiplexing requests). .It Fl o Ar option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options listed below, and their possible values, see .Xr ssh_config 5 . .Pp .Bl -tag -width Ds -offset indent -compact .It AddressFamily .It BatchMode .It BindAddress .It CanonicalDomains .It CanonicalizeFallbackLocal .It CanonicalizeHostname .It CanonicalizeMaxDots .It CanonicalizePermittedCNAMEs .It ChallengeResponseAuthentication .It CheckHostIP .It Cipher .It Ciphers .It ClearAllForwardings .It Compression .It CompressionLevel .It ConnectionAttempts .It ConnectTimeout .It ControlMaster .It ControlPath .It ControlPersist .It DynamicForward .It EscapeChar .It ExitOnForwardFailure .It ForwardAgent .It ForwardX11 .It ForwardX11Timeout .It ForwardX11Trusted .It GatewayPorts .It GlobalKnownHostsFile .It GSSAPIAuthentication .It GSSAPIDelegateCredentials .It HashKnownHosts .It Host .It HostbasedAuthentication .It HostKeyAlgorithms .It HostKeyAlias .It HostName .It IdentityFile .It IdentitiesOnly .It IPQoS .It KbdInteractiveAuthentication .It KbdInteractiveDevices .It KexAlgorithms .It LocalCommand .It LocalForward .It LogLevel .It MACs .It Match .It NoHostAuthenticationForLocalhost .It NumberOfPasswordPrompts .It PasswordAuthentication .It PermitLocalCommand .It PKCS11Provider .It Port .It PreferredAuthentications .It Protocol .It ProxyCommand .It ProxyUseFdpass .It PubkeyAuthentication .It RekeyLimit .It RemoteForward .It RequestTTY .It RhostsRSAAuthentication .It RSAAuthentication .It SendEnv .It ServerAliveInterval .It ServerAliveCountMax .It StrictHostKeyChecking .It TCPKeepAlive .It Tunnel .It TunnelDevice .It UsePrivilegedPort .It User .It UserKnownHostsFile .It VerifyHostKeyDNS .It VersionAddendum .It VisualHostKey .It XAuthLocation .El .It Fl p Ar port Port to connect to on the remote host. This can be specified on a per-host basis in the configuration file. .It Fl Q Cm cipher | cipher-auth | mac | kex | key Queries .Nm for the algorithms supported for the specified version 2. The available features are: .Ar cipher (supported symmetric ciphers), .Ar cipher-auth (supported symmetric ciphers that support authenticated encryption), .Ar mac (supported message integrity codes), .Ar kex (key exchange algorithms), .Ar key (key types). .It Fl q Quiet mode. Causes most warning and diagnostic messages to be suppressed. .It Fl R Xo .Sm off .Oo Ar bind_address : Oc .Ar port : host : hostport .Sm on .Xc Specifies that the given port on the remote (server) host is to be forwarded to the given host and port on the local side. This works by allocating a socket to listen to .Ar port on the remote side, and whenever a connection is made to this port, the connection is forwarded over the secure channel, and a connection is made to .Ar host port .Ar hostport from the local machine. .Pp Port forwardings can also be specified in the configuration file. Privileged ports can be forwarded only when logging in as root on the remote machine. IPv6 addresses can be specified by enclosing the address in square brackets. .Pp By default, the listening socket on the server will be bound to the loopback interface only. This may be overridden by specifying a .Ar bind_address . An empty .Ar bind_address , or the address .Ql * , indicates that the remote socket should listen on all interfaces. Specifying a remote .Ar bind_address will only succeed if the server's .Cm GatewayPorts option is enabled (see .Xr sshd_config 5 ) . .Pp If the .Ar port argument is .Ql 0 , the listen port will be dynamically allocated on the server and reported to the client at run time. When used together with .Ic -O forward the allocated port will be printed to the standard output. .It Fl S Ar ctl_path Specifies the location of a control socket for connection sharing, or the string .Dq none to disable connection sharing. Refer to the description of .Cm ControlPath and .Cm ControlMaster in .Xr ssh_config 5 for details. .It Fl s May be used to request invocation of a subsystem on the remote system. Subsystems are a feature of the SSH2 protocol which facilitate the use of SSH as a secure transport for other applications (eg.\& .Xr sftp 1 ) . The subsystem is specified as the remote command. .It Fl T Disable pseudo-tty allocation. .It Fl t Force pseudo-tty allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple .Fl t options force tty allocation, even if .Nm has no local tty. .It Fl V Display the version number and exit. .It Fl v Verbose mode. Causes .Nm to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuration problems. Multiple .Fl v options increase the verbosity. The maximum is 3. .It Fl W Ar host : Ns Ar port Requests that standard input and output on the client be forwarded to .Ar host on .Ar port over the secure channel. Implies .Fl N , .Fl T , .Cm ExitOnForwardFailure and .Cm ClearAllForwardings . Works with Protocol version 2 only. .It Fl w Xo .Ar local_tun Ns Op : Ns Ar remote_tun .Xc Requests tunnel device forwarding with the specified .Xr tun 4 devices between the client .Pq Ar local_tun and the server .Pq Ar remote_tun . .Pp The devices may be specified by numerical ID or the keyword .Dq any , which uses the next available tunnel device. If .Ar remote_tun is not specified, it defaults to .Dq any . See also the .Cm Tunnel and .Cm TunnelDevice directives in .Xr ssh_config 5 . If the .Cm Tunnel directive is unset, it is set to the default tunnel mode, which is .Dq point-to-point . .It Fl X Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. .Pp X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. .Pp For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Please refer to the .Nm .Fl Y option and the .Cm ForwardX11Trusted directive in .Xr ssh_config 5 for more information. .It Fl x Disables X11 forwarding. .It Fl Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. .It Fl y Send log information using the .Xr syslog 3 system module. By default this information is sent to stderr. .El .Pp .Nm may additionally obtain configuration data from a per-user configuration file and a system-wide configuration file. The file format and configuration options are described in .Xr ssh_config 5 . .Sh AUTHENTICATION The OpenSSH SSH client supports SSH protocols 1 and 2. The default is to use protocol 2 only, though this can be changed via the .Cm Protocol option in .Xr ssh_config 5 or the .Fl 1 and .Fl 2 options (see above). Both protocols support similar authentication methods, but protocol 2 is the default since it provides additional mechanisms for confidentiality (the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour) and integrity (hmac-md5, hmac-sha1, hmac-sha2-256, hmac-sha2-512, umac-64, umac-128, hmac-ripemd160). Protocol 1 lacks a strong mechanism for ensuring the integrity of the connection. .Pp The methods available for authentication are: GSSAPI-based authentication, host-based authentication, public key authentication, challenge-response authentication, and password authentication. Authentication methods are tried in the order specified above, though protocol 2 has a configuration option to change the default order: .Cm PreferredAuthentications . .Pp Host-based authentication works as follows: If the machine the user logs in from is listed in .Pa /etc/hosts.equiv or .Pa /etc/shosts.equiv on the remote machine, and the user names are the same on both sides, or if the files .Pa ~/.rhosts or .Pa ~/.shosts exist in the user's home directory on the remote machine and contain a line containing the name of the client machine and the name of the user on that machine, the user is considered for login. Additionally, the server .Em must be able to verify the client's host key (see the description of .Pa /etc/ssh/ssh_known_hosts and .Pa ~/.ssh/known_hosts , below) for login to be permitted. This authentication method closes security holes due to IP spoofing, DNS spoofing, and routing spoofing. [Note to the administrator: .Pa /etc/hosts.equiv , .Pa ~/.rhosts , and the rlogin/rsh protocol in general, are inherently insecure and should be disabled if security is desired.] .Pp Public key authentication works as follows: The scheme is based on public-key cryptography, using cryptosystems where encryption and decryption are done using separate keys, and it is unfeasible to derive the decryption key from the encryption key. The idea is that each user creates a public/private key pair for authentication purposes. The server knows the public key, and only the user knows the private key. .Nm implements public key authentication protocol automatically, using one of the DSA, ECDSA, ED25519 or RSA algorithms. Protocol 1 is restricted to using only RSA keys, but protocol 2 may use any. The HISTORY section of .Xr ssl 8 contains a brief discussion of the DSA and RSA algorithms. .Pp The file .Pa ~/.ssh/authorized_keys lists the public keys that are permitted for logging in. When the user logs in, the .Nm program tells the server which key pair it would like to use for authentication. The client proves that it has access to the private key and the server checks that the corresponding public key is authorized to accept the account. .Pp The user creates his/her key pair by running .Xr ssh-keygen 1 . This stores the private key in .Pa ~/.ssh/identity (protocol 1), .Pa ~/.ssh/id_dsa (protocol 2 DSA), .Pa ~/.ssh/id_ecdsa (protocol 2 ECDSA), .Pa ~/.ssh/id_ed25519 (protocol 2 ED25519), or .Pa ~/.ssh/id_rsa (protocol 2 RSA) and stores the public key in .Pa ~/.ssh/identity.pub (protocol 1), .Pa ~/.ssh/id_dsa.pub (protocol 2 DSA), .Pa ~/.ssh/id_ecdsa.pub (protocol 2 ECDSA), .Pa ~/.ssh/id_ed25519.pub (protocol 2 ED25519), or .Pa ~/.ssh/id_rsa.pub (protocol 2 RSA) in the user's home directory. The user should then copy the public key to .Pa ~/.ssh/authorized_keys in his/her home directory on the remote machine. The .Pa authorized_keys file corresponds to the conventional .Pa ~/.rhosts file, and has one key per line, though the lines can be very long. After this, the user can log in without giving the password. .Pp A variation on public key authentication is available in the form of certificate authentication: instead of a set of public/private keys, signed certificates are used. This has the advantage that a single trusted certification authority can be used in place of many public/private keys. See the CERTIFICATES section of .Xr ssh-keygen 1 for more information. .Pp The most convenient way to use public key or certificate authentication may be with an authentication agent. See .Xr ssh-agent 1 for more information. .Pp Challenge-response authentication works as follows: The server sends an arbitrary .Qq challenge text, and prompts for a response. Protocol 2 allows multiple challenges and responses; protocol 1 is restricted to just one challenge/response. Examples of challenge-response authentication include .Bx Authentication (see .Xr login.conf 5 ) and PAM (some .Pf non- Ox systems). .Pp Finally, if other authentication methods fail, .Nm prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. .Pp .Nm automatically maintains and checks a database containing identification for all hosts it has ever been used with. Host keys are stored in .Pa ~/.ssh/known_hosts in the user's home directory. Additionally, the file .Pa /etc/ssh/ssh_known_hosts is automatically checked for known hosts. Any new hosts are automatically added to the user's file. If a host's identification ever changes, .Nm warns about this and disables password authentication to prevent server spoofing or man-in-the-middle attacks, which could otherwise be used to circumvent the encryption. The .Cm StrictHostKeyChecking option can be used to control logins to machines whose host key is not known or has changed. .Pp When the user's identity has been accepted by the server, the server either executes the given command, or logs into the machine and gives the user a normal shell on the remote machine. All communication with the remote command or shell will be automatically encrypted. .Pp If a pseudo-terminal has been allocated (normal login session), the user may use the escape characters noted below. .Pp If no pseudo-tty has been allocated, the session is transparent and can be used to reliably transfer binary data. On most systems, setting the escape character to .Dq none will also make the session transparent even if a tty is used. .Pp The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed. .Sh ESCAPE CHARACTERS When a pseudo-terminal has been requested, .Nm supports a number of functions through the use of an escape character. .Pp A single tilde character can be sent as .Ic ~~ or by following the tilde by a character other than those described below. The escape character must always follow a newline to be interpreted as special. The escape character can be changed in configuration files using the .Cm EscapeChar configuration directive or on the command line by the .Fl e option. .Pp The supported escapes (assuming the default .Ql ~ ) are: .Bl -tag -width Ds .It Cm ~. Disconnect. .It Cm ~^Z Background .Nm . .It Cm ~# List forwarded connections. .It Cm ~& Background .Nm at logout when waiting for forwarded connection / X11 sessions to terminate. .It Cm ~? Display a list of escape characters. .It Cm ~B Send a BREAK to the remote system (only useful for SSH protocol version 2 and if the peer supports it). .It Cm ~C Open command line. Currently this allows the addition of port forwardings using the .Fl L , .Fl R and .Fl D options (see above). It also allows the cancellation of existing port-forwardings with .Sm off .Fl KL Oo Ar bind_address : Oc Ar port .Sm on for local, .Sm off .Fl KR Oo Ar bind_address : Oc Ar port .Sm on for remote and .Sm off .Fl KD Oo Ar bind_address : Oc Ar port .Sm on for dynamic port-forwardings. .Ic !\& Ns Ar command allows the user to execute a local command if the .Ic PermitLocalCommand option is enabled in .Xr ssh_config 5 . Basic help is available, using the .Fl h option. .It Cm ~R Request rekeying of the connection (only useful for SSH protocol version 2 and if the peer supports it). .It Cm ~V Decrease the verbosity .Pq Ic LogLevel when errors are being written to stderr. .It Cm ~v Increase the verbosity .Pq Ic LogLevel when errors are being written to stderr. .El .Sh TCP FORWARDING Forwarding of arbitrary TCP connections over the secure channel can be specified either on the command line or in a configuration file. One possible application of TCP forwarding is a secure connection to a mail server; another is going through firewalls. .Pp In the example below, we look at encrypting communication between an IRC client and server, even though the IRC server does not directly support encrypted communications. This works as follows: the user connects to the remote host using .Nm , specifying a port to be used to forward connections to the remote server. After that it is possible to start the service which is to be encrypted on the client machine, connecting to the same local port, and .Nm will encrypt and forward the connection. .Pp The following example tunnels an IRC session from client machine .Dq 127.0.0.1 (localhost) to remote server .Dq server.example.com : .Bd -literal -offset 4n $ ssh -f -L 1234:localhost:6667 server.example.com sleep 10 $ irc -c '#users' -p 1234 pinky 127.0.0.1 .Ed .Pp This tunnels a connection to IRC server .Dq server.example.com , joining channel .Dq #users , nickname .Dq pinky , using port 1234. It doesn't matter which port is used, as long as it's greater than 1023 (remember, only root can open sockets on privileged ports) and doesn't conflict with any ports already in use. The connection is forwarded to port 6667 on the remote server, since that's the standard port for IRC services. .Pp The .Fl f option backgrounds .Nm and the remote command .Dq sleep 10 is specified to allow an amount of time (10 seconds, in the example) to start the service which is to be tunnelled. If no connections are made within the time specified, .Nm will exit. .Sh X11 FORWARDING If the .Cm ForwardX11 variable is set to .Dq yes (or see the description of the .Fl X , .Fl x , and .Fl Y options above) and the user is using X11 (the .Ev DISPLAY environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made from the local machine. The user should not manually set .Ev DISPLAY . Forwarding of X11 connections can be configured on the command line or in configuration files. .Pp The .Ev DISPLAY value set by .Nm will point to the server machine, but with a display number greater than zero. This is normal, and happens because .Nm creates a .Dq proxy X server on the server machine for forwarding the connections over the encrypted channel. .Pp .Nm will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when the connection is opened. The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). .Pp If the .Cm ForwardAgent variable is set to .Dq yes (or see the description of the .Fl A and .Fl a options above) and the user is using an authentication agent, the connection to the agent is automatically forwarded to the remote side. .Sh VERIFYING HOST KEYS When connecting to a server for the first time, a fingerprint of the server's public key is presented to the user (unless the option .Cm StrictHostKeyChecking has been disabled). Fingerprints can be determined using .Xr ssh-keygen 1 : .Pp .Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key .Pp If the fingerprint is already known, it can be matched and the key can be accepted or rejected. Because of the difficulty of comparing host keys just by looking at hex strings, there is also support to compare host keys visually, using .Em random art . By setting the .Cm VisualHostKey option to .Dq yes , a small ASCII graphic gets displayed on every login to a server, no matter if the session itself is interactive or not. By learning the pattern a known server produces, a user can easily find out that the host key has changed when a completely different pattern is displayed. Because these patterns are not unambiguous however, a pattern that looks similar to the pattern remembered only gives a good probability that the host key is the same, not guaranteed proof. .Pp To get a listing of the fingerprints along with their random art for all known hosts, the following command line can be used: .Pp .Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts .Pp If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. An additional resource record (RR), SSHFP, is added to a zonefile and the connecting client is able to match the fingerprint with that of the key presented. .Pp In this example, we are connecting a client to a server, .Dq host.example.com . The SSHFP resource records should first be added to the zonefile for host.example.com: .Bd -literal -offset indent $ ssh-keygen -r host.example.com. .Ed .Pp The output lines will have to be added to the zonefile. To check that the zone is answering fingerprint queries: .Pp .Dl $ dig -t SSHFP host.example.com .Pp Finally the client connects: .Bd -literal -offset indent $ ssh -o "VerifyHostKeyDNS ask" host.example.com [...] Matching host key fingerprint found in DNS. Are you sure you want to continue connecting (yes/no)? .Ed .Pp See the .Cm VerifyHostKeyDNS option in .Xr ssh_config 5 for more information. .Sh SSH-BASED VIRTUAL PRIVATE NETWORKS .Nm contains support for Virtual Private Network (VPN) tunnelling using the .Xr tun 4 network pseudo-device, allowing two networks to be joined securely. The .Xr sshd_config 5 configuration option .Cm PermitTunnel controls whether the server supports this, and at what level (layer 2 or 3 traffic). .Pp The following example would connect client network 10.0.50.0/24 with remote network 10.0.99.0/24 using a point-to-point connection from 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway to the remote network, at 192.168.1.15, allows it. .Pp On the client: .Bd -literal -offset indent # ssh -f -w 0:1 192.168.1.15 true # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 # route add 10.0.99.0/24 10.1.1.2 .Ed .Pp On the server: .Bd -literal -offset indent # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 # route add 10.0.50.0/24 10.1.1.1 .Ed .Pp Client access may be more finely tuned via the .Pa /root/.ssh/authorized_keys file (see below) and the .Cm PermitRootLogin server option. The following entry would permit connections on .Xr tun 4 device 1 from user .Dq jane and on tun device 2 from user .Dq john , if .Cm PermitRootLogin is set to .Dq forced-commands-only : .Bd -literal -offset 2n tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john .Ed .Pp Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as .Xr ipsecctl 8 and .Xr isakmpd 8 . .Sh ENVIRONMENT .Nm will normally set the following environment variables: .Bl -tag -width "SSH_ORIGINAL_COMMAND" .It Ev DISPLAY The .Ev DISPLAY variable indicates the location of the X11 server. It is automatically set by .Nm to point to a value of the form .Dq hostname:n , where .Dq hostname indicates the host where the shell runs, and .Sq n is an integer \*(Ge 1. .Nm uses this special value to forward X11 connections over the secure channel. The user should normally not set .Ev DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). .It Ev HOME Set to the path of the user's home directory. .It Ev LOGNAME Synonym for .Ev USER ; set for compatibility with systems that use this variable. .It Ev MAIL Set to the path of the user's mailbox. .It Ev PATH Set to the default .Ev PATH , as specified when compiling .Nm . .It Ev SSH_ASKPASS If .Nm needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If .Nm does not have a terminal associated with it but .Ev DISPLAY and .Ev SSH_ASKPASS are set, it will execute the program specified by .Ev SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling .Nm from a .Pa .xsession or related script. (Note that on some machines it may be necessary to redirect the input from .Pa /dev/null to make this work.) .It Ev SSH_AUTH_SOCK Identifies the path of a .Ux Ns -domain socket used to communicate with the agent. .It Ev SSH_CONNECTION Identifies the client and server ends of the connection. The variable contains four space-separated values: client IP address, client port number, server IP address, and server port number. .It Ev SSH_ORIGINAL_COMMAND This variable contains the original command line if a forced command is executed. It can be used to extract the original arguments. .It Ev SSH_TTY This is set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set. .It Ev TZ This variable is set to indicate the present time zone if it was set when the daemon was started (i.e. the daemon passes the value on to new connections). .It Ev USER Set to the name of the user logging in. .El .Pp Additionally, .Nm reads .Pa ~/.ssh/environment , and adds lines of the format .Dq VARNAME=value to the environment if the file exists and users are allowed to change their environment. For more information, see the .Cm PermitUserEnvironment option in .Xr sshd_config 5 . .Sh FILES .Bl -tag -width Ds -compact .It Pa ~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world-readable if the user's home directory is on an NFS partition, because .Xr sshd 8 reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. .Pp .It Pa ~/.shosts This file is used in exactly the same way as .Pa .rhosts , but allows host-based authentication without permitting login with rlogin/rsh. .Pp .It Pa ~/.ssh/ This directory is the default location for all user-specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. .Pp .It Pa ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, ED25519, RSA) that can be used for logging in as this user. The format of this file is described in the .Xr sshd 8 manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. .Pp .It Pa ~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in .Xr ssh_config 5 . Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others. .Pp .It Pa ~/.ssh/environment Contains additional definitions for environment variables; see .Sx ENVIRONMENT , above. .Pp .It Pa ~/.ssh/identity .It Pa ~/.ssh/id_dsa .It Pa ~/.ssh/id_ecdsa .It Pa ~/.ssh/id_ed25519 .It Pa ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not accessible by others (read/write/execute). .Nm will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using 3DES. .Pp .It Pa ~/.ssh/identity.pub .It Pa ~/.ssh/id_dsa.pub .It Pa ~/.ssh/id_ecdsa.pub .It Pa ~/.ssh/id_ed25519.pub .It Pa ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. .Pp .It Pa ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See .Xr sshd 8 for further details of the format of this file. .Pp .It Pa ~/.ssh/rc Commands in this file are executed by .Nm when the user logs in, just before the user's shell (or command) is started. See the .Xr sshd 8 manual page for more information. .Pp .It Pa /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. .Pp .It Pa /etc/shosts.equiv This file is used in exactly the same way as .Pa hosts.equiv , but allows host-based authentication without permitting login with rlogin/rsh. .Pp .It Pa /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in .Xr ssh_config 5 . .Pp .It Pa /etc/ssh/ssh_host_key .It Pa /etc/ssh/ssh_host_dsa_key .It Pa /etc/ssh/ssh_host_ecdsa_key .It Pa /etc/ssh/ssh_host_ed25519_key .It Pa /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. If protocol version 1 is used, .Nm must be setuid root, since the host key is readable only by root. For protocol version 2, .Nm uses .Xr ssh-keysign 8 to access the host keys, eliminating the requirement that .Nm be setuid root when host-based authentication is used. By default .Nm is not setuid root. .Pp .It Pa /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See .Xr sshd 8 for further details of the format of this file. .Pp .It Pa /etc/ssh/sshrc Commands in this file are executed by .Nm when the user logs in, just before the user's shell (or command) is started. See the .Xr sshd 8 manual page for more information. .El .Sh EXIT STATUS .Nm exits with the exit status of the remote command or with 255 if an error occurred. .Sh SEE ALSO .Xr scp 1 , .Xr sftp 1 , .Xr ssh-add 1 , .Xr ssh-agent 1 , .Xr ssh-keygen 1 , .Xr ssh-keyscan 1 , .Xr tun 4 , .Xr hosts.equiv 5 , .Xr ssh_config 5 , .Xr ssh-keysign 8 , .Xr sshd 8 .Sh STANDARDS .Rs .%A S. Lehtinen .%A C. Lonvick .%D January 2006 .%R RFC 4250 .%T The Secure Shell (SSH) Protocol Assigned Numbers .Re .Pp .Rs .%A T. Ylonen .%A C. Lonvick .%D January 2006 .%R RFC 4251 .%T The Secure Shell (SSH) Protocol Architecture .Re .Pp .Rs .%A T. Ylonen .%A C. Lonvick .%D January 2006 .%R RFC 4252 .%T The Secure Shell (SSH) Authentication Protocol .Re .Pp .Rs .%A T. Ylonen .%A C. Lonvick .%D January 2006 .%R RFC 4253 .%T The Secure Shell (SSH) Transport Layer Protocol .Re .Pp .Rs .%A T. Ylonen .%A C. Lonvick .%D January 2006 .%R RFC 4254 .%T The Secure Shell (SSH) Connection Protocol .Re .Pp .Rs .%A J. Schlyter .%A W. Griffin .%D January 2006 .%R RFC 4255 .%T Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints .Re .Pp .Rs .%A F. Cusack .%A M. Forssen .%D January 2006 .%R RFC 4256 .%T Generic Message Exchange Authentication for the Secure Shell Protocol (SSH) .Re .Pp .Rs .%A J. Galbraith .%A P. Remaker .%D January 2006 .%R RFC 4335 .%T The Secure Shell (SSH) Session Channel Break Extension .Re .Pp .Rs .%A M. Bellare .%A T. Kohno .%A C. Namprempre .%D January 2006 .%R RFC 4344 .%T The Secure Shell (SSH) Transport Layer Encryption Modes .Re .Pp .Rs .%A B. Harris .%D January 2006 .%R RFC 4345 .%T Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol .Re .Pp .Rs .%A M. Friedl .%A N. Provos .%A W. Simpson .%D March 2006 .%R RFC 4419 .%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol .Re .Pp .Rs .%A J. Galbraith .%A R. Thayer .%D November 2006 .%R RFC 4716 .%T The Secure Shell (SSH) Public Key File Format .Re .Pp .Rs .%A D. Stebila .%A J. Green .%D December 2009 .%R RFC 5656 .%T Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer .Re .Pp .Rs .%A A. Perrig .%A D. Song .%D 1999 .%O International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99) .%T Hash Visualization: a New Technique to improve Real-World Security .Re .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Index: head/crypto/openssh/ssh_config.5 =================================================================== --- head/crypto/openssh/ssh_config.5 (revision 290670) +++ head/crypto/openssh/ssh_config.5 (revision 290671) @@ -1,1509 +1,1509 @@ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: ssh_config.5,v 1.185 2014/02/23 20:11:36 djm Exp $ .\" $FreeBSD$ -.Dd March 22, 2015 +.Dd $Mdocdate: February 23 2014 $ .Dt SSH_CONFIG 5 .Os .Sh NAME .Nm ssh_config .Nd OpenSSH SSH client configuration files .Sh SYNOPSIS .Nm ~/.ssh/config .Nm /etc/ssh/ssh_config .Sh DESCRIPTION .Xr ssh 1 obtains configuration data from the following sources in the following order: .Pp .Bl -enum -offset indent -compact .It command-line options .It user's configuration file .Pq Pa ~/.ssh/config .It system-wide configuration file .Pq Pa /etc/ssh/ssh_config .El .Pp For each parameter, the first obtained value will be used. The configuration files contain sections separated by .Dq Host specifications, and that section is only applied for hosts that match one of the patterns given in the specification. The matched host name is the one given on the command line. .Pp Since the first obtained value for each parameter is used, more host-specific declarations should be given near the beginning of the file, and general defaults at the end. .Pp The configuration file has the following format: .Pp Empty lines and lines starting with .Ql # are comments. Otherwise a line is of the format .Dq keyword arguments . Configuration options may be separated by whitespace or optional whitespace and exactly one .Ql = ; the latter format is useful to avoid the need to quote whitespace when specifying configuration options using the .Nm ssh , .Nm scp , and .Nm sftp .Fl o option. Arguments may optionally be enclosed in double quotes .Pq \&" in order to represent arguments containing spaces. .Pp The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive): .Bl -tag -width Ds .It Cm Host Restricts the following declarations (up to the next .Cm Host or .Cm Match keyword) to be only for those hosts that match one of the patterns given after the keyword. If more than one pattern is provided, they should be separated by whitespace. A single .Ql * as a pattern can be used to provide global defaults for all hosts. The host is the .Ar hostname argument given on the command line (i.e. the name is not converted to a canonicalized host name before matching). .Pp A pattern entry may be negated by prefixing it with an exclamation mark .Pq Sq !\& . If a negated entry is matched, then the .Cm Host entry is ignored, regardless of whether any other patterns on the line match. Negated matches are therefore useful to provide exceptions for wildcard matches. .Pp See .Sx PATTERNS for more information on patterns. .It Cm Match Restricts the following declarations (up to the next .Cm Host or .Cm Match keyword) to be used only when the conditions following the .Cm Match keyword are satisfied. Match conditions are specified using one or more keyword/criteria pairs or the single token .Cm all which matches all criteria. The available keywords are: .Cm exec , .Cm host , .Cm originalhost , .Cm user , and .Cm localuser . .Pp The .Cm exec keyword executes the specified command under the user's shell. If the command returns a zero exit status then the condition is considered true. Commands containing whitespace characters must be quoted. The following character sequences in the command will be expanded prior to execution: .Ql %L will be substituted by the first component of the local host name, .Ql %l will be substituted by the local host name (including any domain name), .Ql %h will be substituted by the target host name, .Ql %n will be substituted by the original target host name specified on the command-line, .Ql %p the destination port, .Ql %r by the remote login username, and .Ql %u by the username of the user running .Xr ssh 1 . .Pp The other keywords' criteria must be single entries or comma-separated lists and may use the wildcard and negation operators described in the .Sx PATTERNS section. The criteria for the .Cm host keyword are matched against the target hostname, after any substitution by the .Cm Hostname option. The .Cm originalhost keyword matches against the hostname as it was specified on the command-line. The .Cm user keyword matches against the target username on the remote host. The .Cm localuser keyword matches against the name of the local user running .Xr ssh 1 (this keyword may be useful in system-wide .Nm files). .It Cm AddressFamily Specifies which address family to use when connecting. Valid arguments are .Dq any , .Dq inet (use IPv4 only), or .Dq inet6 (use IPv6 only). .It Cm BatchMode If set to .Dq yes , passphrase/password querying will be disabled. This option is useful in scripts and other batch jobs where no user is present to supply the password. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm BindAddress Use the specified address on the local machine as the source address of the connection. Only useful on systems with more than one address. Note that this option does not work if .Cm UsePrivilegedPort is set to .Dq yes . .It Cm CanonicalDomains When .Cm CanonicalizeHostname is enabled, this option specifies the list of domain suffixes in which to search for the specified destination host. .It Cm CanonicalizeFallbackLocal Specifies whether to fail with an error when hostname canonicalization fails. The default, .Dq yes , will attempt to look up the unqualified hostname using the system resolver's search rules. A value of .Dq no will cause .Xr ssh 1 to fail instantly if .Cm CanonicalizeHostname is enabled and the target hostname cannot be found in any of the domains specified by .Cm CanonicalDomains . .It Cm CanonicalizeHostname Controls whether explicit hostname canonicalization is performed. The default, .Dq no , is not to perform any name rewriting and let the system resolver handle all hostname lookups. If set to .Dq yes then, for connections that do not use a .Cm ProxyCommand , .Xr ssh 1 will attempt to canonicalize the hostname specified on the command line using the .Cm CanonicalDomains suffixes and .Cm CanonicalizePermittedCNAMEs rules. If .Cm CanonicalizeHostname is set to .Dq always , then canonicalization is applied to proxied connections too. .Pp If this option is enabled and canonicalisation results in the target hostname changing, then the configuration files are processed again using the new target name to pick up any new configuration in matching .Cm Host stanzas. .It Cm CanonicalizeMaxDots Specifies the maximum number of dot characters in a hostname before canonicalization is disabled. The default, .Dq 1 , allows a single dot (i.e. hostname.subdomain). .It Cm CanonicalizePermittedCNAMEs Specifies rules to determine whether CNAMEs should be followed when canonicalizing hostnames. The rules consist of one or more arguments of .Ar source_domain_list : Ns Ar target_domain_list , where .Ar source_domain_list is a pattern-list of domains that may follow CNAMEs in canonicalization, and .Ar target_domain_list is a pattern-list of domains that they may resolve to. .Pp For example, .Dq *.a.example.com:*.b.example.com,*.c.example.com will allow hostnames matching .Dq *.a.example.com to be canonicalized to names in the .Dq *.b.example.com or .Dq *.c.example.com domains. .It Cm ChallengeResponseAuthentication Specifies whether to use challenge-response authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm CheckHostIP If this flag is set to .Dq yes , .Xr ssh 1 will additionally check the host IP address in the .Pa known_hosts file. This allows ssh to detect if a host key changed due to DNS spoofing. If the option is set to .Dq no , the check will not be executed. The default is .Dq no . .It Cm Cipher Specifies the cipher to use for encrypting the session in protocol version 1. Currently, .Dq blowfish , .Dq 3des , and .Dq des are supported. .Ar des is only supported in the .Xr ssh 1 client for interoperability with legacy protocol 1 implementations that do not support the .Ar 3des cipher. Its use is strongly discouraged due to cryptographic weaknesses. The default is .Dq 3des . .It Cm Ciphers Specifies the ciphers allowed for protocol version 2 in order of preference. Multiple ciphers must be comma-separated. The supported ciphers are: .Pp .Dq 3des-cbc , .Dq aes128-cbc , .Dq aes192-cbc , .Dq aes256-cbc , .Dq aes128-ctr , .Dq aes192-ctr , .Dq aes256-ctr , .Dq aes128-gcm@openssh.com , .Dq aes256-gcm@openssh.com , .Dq arcfour128 , .Dq arcfour256 , .Dq arcfour , .Dq blowfish-cbc , .Dq cast128-cbc , and .Dq chacha20-poly1305@openssh.com . .Pp The default is: .Bd -literal -offset 3n aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, aes128-gcm@openssh.com,aes256-gcm@openssh.com, chacha20-poly1305@openssh.com, aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, aes256-cbc,arcfour .Ed .Pp The list of available ciphers may also be obtained using the .Fl Q option of .Xr ssh 1 . .It Cm ClearAllForwardings Specifies that all local, remote, and dynamic port forwardings specified in the configuration files or on the command line be cleared. This option is primarily useful when used from the .Xr ssh 1 command line to clear port forwardings set in configuration files, and is automatically set by .Xr scp 1 and .Xr sftp 1 . The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm Compression Specifies whether to use compression. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm CompressionLevel Specifies the compression level to use if compression is enabled. The argument must be an integer from 1 (fast) to 9 (slow, best). The default level is 6, which is good for most applications. The meaning of the values is the same as in .Xr gzip 1 . Note that this option applies to protocol version 1 only. .It Cm ConnectionAttempts Specifies the number of tries (one per second) to make before exiting. The argument must be an integer. This may be useful in scripts if the connection sometimes fails. The default is 1. .It Cm ConnectTimeout Specifies the timeout (in seconds) used when connecting to the SSH server, instead of using the default system TCP timeout. This value is used only when the target is down or really unreachable, not when it refuses the connection. .It Cm ControlMaster Enables the sharing of multiple sessions over a single network connection. When set to .Dq yes , .Xr ssh 1 will listen for connections on a control socket specified using the .Cm ControlPath argument. Additional sessions can connect to this socket using the same .Cm ControlPath with .Cm ControlMaster set to .Dq no (the default). These sessions will try to reuse the master instance's network connection rather than initiating new ones, but will fall back to connecting normally if the control socket does not exist, or is not listening. .Pp Setting this to .Dq ask will cause ssh to listen for control connections, but require confirmation using the .Ev SSH_ASKPASS program before they are accepted (see .Xr ssh-add 1 for details). If the .Cm ControlPath cannot be opened, ssh will continue without connecting to a master instance. .Pp X11 and .Xr ssh-agent 1 forwarding is supported over these multiplexed connections, however the display and agent forwarded will be the one belonging to the master connection i.e. it is not possible to forward multiple displays or agents. .Pp Two additional options allow for opportunistic multiplexing: try to use a master connection but fall back to creating a new one if one does not already exist. These options are: .Dq auto and .Dq autoask . The latter requires confirmation like the .Dq ask option. .It Cm ControlPath Specify the path to the control socket used for connection sharing as described in the .Cm ControlMaster section above or the string .Dq none to disable connection sharing. In the path, .Ql %L will be substituted by the first component of the local host name, .Ql %l will be substituted by the local host name (including any domain name), .Ql %h will be substituted by the target host name, .Ql %n will be substituted by the original target host name specified on the command line, .Ql %p the destination port, .Ql %r by the remote login username, and .Ql %u by the username of the user running .Xr ssh 1 . It is recommended that any .Cm ControlPath used for opportunistic connection sharing include at least %h, %p, and %r. This ensures that shared connections are uniquely identified. .It Cm ControlPersist When used in conjunction with .Cm ControlMaster , specifies that the master connection should remain open in the background (waiting for future client connections) after the initial client connection has been closed. If set to .Dq no , then the master connection will not be placed into the background, and will close as soon as the initial client connection is closed. If set to .Dq yes , then the master connection will remain in the background indefinitely (until killed or closed via a mechanism such as the .Xr ssh 1 .Dq Fl O No exit option). If set to a time in seconds, or a time in any of the formats documented in .Xr sshd_config 5 , then the backgrounded master connection will automatically terminate after it has remained idle (with no client connections) for the specified time. .It Cm DynamicForward Specifies that a TCP port on the local machine be forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. .Pp The argument must be .Sm off .Oo Ar bind_address : Oc Ar port . .Sm on IPv6 addresses can be specified by enclosing addresses in square brackets. By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .Pp Currently the SOCKS4 and SOCKS5 protocols are supported, and .Xr ssh 1 will act as a SOCKS server. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. .It Cm EnableSSHKeysign Setting this option to .Dq yes in the global client configuration file .Pa /etc/ssh/ssh_config enables the use of the helper program .Xr ssh-keysign 8 during .Cm HostbasedAuthentication . The argument must be .Dq yes or .Dq no . The default is .Dq no . This option should be placed in the non-hostspecific section. See .Xr ssh-keysign 8 for more information. .It Cm EscapeChar Sets the escape character (default: .Ql ~ ) . The escape character can also be set on the command line. The argument should be a single character, .Ql ^ followed by a letter, or .Dq none to disable the escape character entirely (making the connection transparent for binary data). .It Cm ExitOnForwardFailure Specifies whether .Xr ssh 1 should terminate the connection if it cannot set up all requested dynamic, tunnel, local, and remote port forwardings. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm ForwardAgent Specifies whether the connection to the authentication agent (if any) will be forwarded to the remote machine. The argument must be .Dq yes or .Dq no . The default is .Dq no . .Pp Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. .It Cm ForwardX11 Specifies whether X11 connections will be automatically redirected over the secure channel and .Ev DISPLAY set. The argument must be .Dq yes or .Dq no . The default is .Dq no . .Pp X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X11 authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring if the .Cm ForwardX11Trusted option is also enabled. .It Cm ForwardX11Timeout Specify a timeout for untrusted X11 forwarding using the format described in the TIME FORMATS section of .Xr sshd_config 5 . X11 connections received by .Xr ssh 1 after this time will be refused. The default is to disable untrusted X11 forwarding after twenty minutes has elapsed. .It Cm ForwardX11Trusted If this option is set to .Dq yes , remote X11 clients will have full access to the original X11 display. .Pp If this option is set to .Dq no , remote X11 clients will be considered untrusted and prevented from stealing or tampering with data belonging to trusted X11 clients. Furthermore, the .Xr xauth 1 token used for the session will be set to expire after 20 minutes. Remote clients will be refused access after this time. .Pp The default is .Dq no . .Pp See the X11 SECURITY extension specification for full details on the restrictions imposed on untrusted clients. .It Cm GatewayPorts Specifies whether remote hosts are allowed to connect to local forwarded ports. By default, .Xr ssh 1 binds local port forwardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. .Cm GatewayPorts can be used to specify that ssh should bind local port forwardings to the wildcard address, thus allowing remote hosts to connect to forwarded ports. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm GlobalKnownHostsFile Specifies one or more files to use for the global host key database, separated by whitespace. The default is .Pa /etc/ssh/ssh_known_hosts , .Pa /etc/ssh/ssh_known_hosts2 . .It Cm GSSAPIAuthentication Specifies whether user authentication based on GSSAPI is allowed. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm GSSAPIDelegateCredentials Forward (delegate) credentials to the server. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm HashKnownHosts Indicates that .Xr ssh 1 should hash host names and addresses when they are added to .Pa ~/.ssh/known_hosts . These hashed names may be used normally by .Xr ssh 1 and .Xr sshd 8 , but they do not reveal identifying information should the file's contents be disclosed. The default is .Dq no . Note that existing names and addresses in known hosts files will not be converted automatically, but may be manually hashed using .Xr ssh-keygen 1 . .It Cm HostbasedAuthentication Specifies whether to try rhosts based authentication with public key authentication. The argument must be .Dq yes or .Dq no . The default is .Dq no . This option applies to protocol version 2 only and is similar to .Cm RhostsRSAAuthentication . .It Cm HostKeyAlgorithms Specifies the protocol version 2 host key algorithms that the client wants to use in order of preference. The default for this option is: .Bd -literal -offset 3n ecdsa-sha2-nistp256-cert-v01@openssh.com, ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com, ssh-ed25519-cert-v01@openssh.com, ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com, ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com, ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, ssh-ed25519,ssh-rsa,ssh-dss .Ed .Pp If hostkeys are known for the destination host then this default is modified to prefer their algorithms. .It Cm HostKeyAlias Specifies an alias that should be used instead of the real host name when looking up or saving the host key in the host key database files. This option is useful for tunneling SSH connections or for multiple servers running on a single host. .It Cm HostName Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts. If the hostname contains the character sequence .Ql %h , then this will be replaced with the host name specified on the command line (this is useful for manipulating unqualified names). The default is the name given on the command line. Numeric IP addresses are also permitted (both on the command line and in .Cm HostName specifications). .It Cm IdentitiesOnly Specifies that .Xr ssh 1 should only use the authentication identity files configured in the .Nm files, even if .Xr ssh-agent 1 or a .Cm PKCS11Provider offers more identities. The argument to this keyword must be .Dq yes or .Dq no . This option is intended for situations where ssh-agent offers many different identities. The default is .Dq no . .It Cm IdentityFile Specifies a file from which the user's DSA, ECDSA, ED25519 or RSA authentication identity is read. The default is .Pa ~/.ssh/identity for protocol version 1, and .Pa ~/.ssh/id_dsa , .Pa ~/.ssh/id_ecdsa , .Pa ~/.ssh/id_ed25519 and .Pa ~/.ssh/id_rsa for protocol version 2. Additionally, any identities represented by the authentication agent will be used for authentication unless .Cm IdentitiesOnly is set. .Xr ssh 1 will try to load certificate information from the filename obtained by appending .Pa -cert.pub to the path of a specified .Cm IdentityFile . .Pp The file name may use the tilde syntax to refer to a user's home directory or one of the following escape characters: .Ql %d (local user's home directory), .Ql %u (local user name), .Ql %l (local host name), .Ql %h (remote host name) or .Ql %r (remote user name). .Pp It is possible to have multiple identity files specified in configuration files; all these identities will be tried in sequence. Multiple .Cm IdentityFile directives will add to the list of identities tried (this behaviour differs from that of other configuration directives). .Pp .Cm IdentityFile may be used in conjunction with .Cm IdentitiesOnly to select which identities in an agent are offered during authentication. .It Cm IgnoreUnknown Specifies a pattern-list of unknown options to be ignored if they are encountered in configuration parsing. This may be used to suppress errors if .Nm contains options that are unrecognised by .Xr ssh 1 . It is recommended that .Cm IgnoreUnknown be listed early in the configuration file as it will not be applied to unknown options that appear before it. .It Cm IPQoS Specifies the IPv4 type-of-service or DSCP class for connections. Accepted values are .Dq af11 , .Dq af12 , .Dq af13 , .Dq af21 , .Dq af22 , .Dq af23 , .Dq af31 , .Dq af32 , .Dq af33 , .Dq af41 , .Dq af42 , .Dq af43 , .Dq cs0 , .Dq cs1 , .Dq cs2 , .Dq cs3 , .Dq cs4 , .Dq cs5 , .Dq cs6 , .Dq cs7 , .Dq ef , .Dq lowdelay , .Dq throughput , .Dq reliability , or a numeric value. This option may take one or two arguments, separated by whitespace. If one argument is specified, it is used as the packet class unconditionally. If two values are specified, the first is automatically selected for interactive sessions and the second for non-interactive sessions. The default is .Dq lowdelay for interactive sessions and .Dq throughput for non-interactive sessions. .It Cm KbdInteractiveAuthentication Specifies whether to use keyboard-interactive authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm KbdInteractiveDevices Specifies the list of methods to use in keyboard-interactive authentication. Multiple method names must be comma-separated. The default is to use the server specified list. The methods available vary depending on what the server supports. For an OpenSSH server, it may be zero or more of: .Dq bsdauth , .Dq pam , and .Dq skey . .It Cm KexAlgorithms Specifies the available KEX (Key Exchange) algorithms. Multiple algorithms must be comma-separated. The default is: .Bd -literal -offset indent curve25519-sha256@libssh.org, ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521, diffie-hellman-group-exchange-sha256, diffie-hellman-group-exchange-sha1, diffie-hellman-group14-sha1, diffie-hellman-group1-sha1 .Ed .It Cm LocalCommand Specifies a command to execute on the local machine after successfully connecting to the server. The command string extends to the end of the line, and is executed with the user's shell. The following escape character substitutions will be performed: .Ql %d (local user's home directory), .Ql %h (remote host name), .Ql %l (local host name), .Ql %n (host name as provided on the command line), .Ql %p (remote port), .Ql %r (remote user name) or .Ql %u (local user name). .Pp The command is run synchronously and does not have access to the session of the .Xr ssh 1 that spawned it. It should not be used for interactive commands. .Pp This directive is ignored unless .Cm PermitLocalCommand has been enabled. .It Cm LocalForward Specifies that a TCP port on the local machine be forwarded over the secure channel to the specified host and port from the remote machine. The first argument must be .Sm off .Oo Ar bind_address : Oc Ar port .Sm on and the second argument must be .Ar host : Ns Ar hostport . IPv6 addresses can be specified by enclosing addresses in square brackets. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .It Cm LogLevel Gives the verbosity level that is used when logging messages from .Xr ssh 1 . The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of verbose output. .It Cm MACs Specifies the MAC (message authentication code) algorithms in order of preference. The MAC algorithm is used in protocol version 2 for data integrity protection. Multiple algorithms must be comma-separated. The algorithms that contain .Dq -etm calculate the MAC after encryption (encrypt-then-mac). These are considered safer and their use recommended. The default is: .Bd -literal -offset indent hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com, umac-64-etm@openssh.com,umac-128-etm@openssh.com, hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com, hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com, hmac-md5-96-etm@openssh.com, hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com, hmac-sha2-256,hmac-sha2-512,hmac-ripemd160, hmac-sha1-96,hmac-md5-96 .Ed .It Cm NoHostAuthenticationForLocalhost This option can be used if the home directory is shared across machines. In this case localhost will refer to a different machine on each of the machines and the user will get many warnings about changed host keys. However, this option disables host authentication for localhost. The argument to this keyword must be .Dq yes or .Dq no . The default is to check the host key for localhost. .It Cm NumberOfPasswordPrompts Specifies the number of password prompts before giving up. The argument to this keyword must be an integer. The default is 3. .It Cm PasswordAuthentication Specifies whether to use password authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm PermitLocalCommand Allow local command execution via the .Ic LocalCommand option or using the .Ic !\& Ns Ar command escape sequence in .Xr ssh 1 . The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm PKCS11Provider Specifies which PKCS#11 provider to use. The argument to this keyword is the PKCS#11 shared library .Xr ssh 1 should use to communicate with a PKCS#11 token providing the user's private RSA key. .It Cm Port Specifies the port number to connect on the remote host. The default is 22. .It Cm PreferredAuthentications Specifies the order in which the client should try protocol 2 authentication methods. This allows a client to prefer one method (e.g.\& .Cm keyboard-interactive ) over another method (e.g.\& .Cm password ) . The default is: .Bd -literal -offset indent gssapi-with-mic,hostbased,publickey, keyboard-interactive,password .Ed .It Cm Protocol Specifies the protocol versions .Xr ssh 1 should support in order of preference. The possible values are .Sq 1 and .Sq 2 . Multiple versions must be comma-separated. When this option is set to .Dq 2,1 .Nm ssh will try version 2 and fall back to version 1 if version 2 is not available. The default is .Sq 2 . .It Cm ProxyCommand Specifies the command to use to connect to the server. The command string extends to the end of the line, and is executed with the user's shell. In the command string, any occurrence of .Ql %h will be substituted by the host name to connect, .Ql %p by the port, and .Ql %r by the remote user name. The command can be basically anything, and should read from its standard input and write to its standard output. It should eventually connect an .Xr sshd 8 server running on some machine, or execute .Ic sshd -i somewhere. Host key management will be done using the HostName of the host being connected (defaulting to the name typed by the user). Setting the command to .Dq none disables this option entirely. Note that .Cm CheckHostIP is not available for connects with a proxy command. .Pp This directive is useful in conjunction with .Xr nc 1 and its proxy support. For example, the following directive would connect via an HTTP proxy at 192.0.2.0: .Bd -literal -offset 3n ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p .Ed .It Cm ProxyUseFdpass Specifies that .Cm ProxyCommand will pass a connected file descriptor back to .Xr ssh 1 instead of continuing to execute and pass data. The default is .Dq no . .It Cm PubkeyAuthentication Specifies whether to try public key authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . This option applies to protocol version 2 only. .It Cm RekeyLimit Specifies the maximum amount of data that may be transmitted before the session key is renegotiated, optionally followed a maximum amount of time that may pass before the session key is renegotiated. The first argument is specified in bytes and may have a suffix of .Sq K , .Sq M , or .Sq G to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between .Sq 1G and .Sq 4G , depending on the cipher. The optional second value is specified in seconds and may use any of the units documented in the TIME FORMATS section of .Xr sshd_config 5 . The default value for .Cm RekeyLimit is .Dq default none , which means that rekeying is performed after the cipher's default amount of data has been sent or received and no time based rekeying is done. This option applies to protocol version 2 only. .It Cm RemoteForward Specifies that a TCP port on the remote machine be forwarded over the secure channel to the specified host and port from the local machine. The first argument must be .Sm off .Oo Ar bind_address : Oc Ar port .Sm on and the second argument must be .Ar host : Ns Ar hostport . IPv6 addresses can be specified by enclosing addresses in square brackets. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Privileged ports can be forwarded only when logging in as root on the remote machine. .Pp If the .Ar port argument is .Ql 0 , the listen port will be dynamically allocated on the server and reported to the client at run time. .Pp If the .Ar bind_address is not specified, the default is to only bind to loopback addresses. If the .Ar bind_address is .Ql * or an empty string, then the forwarding is requested to listen on all interfaces. Specifying a remote .Ar bind_address will only succeed if the server's .Cm GatewayPorts option is enabled (see .Xr sshd_config 5 ) . .It Cm RequestTTY Specifies whether to request a pseudo-tty for the session. The argument may be one of: .Dq no (never request a TTY), .Dq yes (always request a TTY when standard input is a TTY), .Dq force (always request a TTY) or .Dq auto (request a TTY when opening a login session). This option mirrors the .Fl t and .Fl T flags for .Xr ssh 1 . .It Cm RhostsRSAAuthentication Specifies whether to try rhosts based authentication with RSA host authentication. The argument must be .Dq yes or .Dq no . The default is .Dq no . This option applies to protocol version 1 only and requires .Xr ssh 1 to be setuid root. .It Cm RSAAuthentication Specifies whether to try RSA authentication. The argument to this keyword must be .Dq yes or .Dq no . RSA authentication will only be attempted if the identity file exists, or an authentication agent is running. The default is .Dq yes . Note that this option applies to protocol version 1 only. .It Cm SendEnv Specifies what variables from the local .Xr environ 7 should be sent to the server. Note that environment passing is only supported for protocol 2. The server must also support it, and the server must be configured to accept these environment variables. Refer to .Cm AcceptEnv in .Xr sshd_config 5 for how to configure the server. Variables are specified by name, which may contain wildcard characters. Multiple environment variables may be separated by whitespace or spread across multiple .Cm SendEnv directives. The default is not to send any environment variables. .Pp See .Sx PATTERNS for more information on patterns. .It Cm ServerAliveCountMax Sets the number of server alive messages (see below) which may be sent without .Xr ssh 1 receiving any messages back from the server. If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. It is important to note that the use of server alive messages is very different from .Cm TCPKeepAlive (below). The server alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by .Cm TCPKeepAlive is spoofable. The server alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. .Pp The default value is 3. If, for example, .Cm ServerAliveInterval (see below) is set to 15 and .Cm ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. This option applies to protocol version 2 only. .It Cm ServerAliveInterval Sets a timeout interval in seconds after which if no data has been received from the server, .Xr ssh 1 will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only. .It Cm StrictHostKeyChecking If this flag is set to .Dq yes , .Xr ssh 1 will never automatically add host keys to the .Pa ~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This provides maximum protection against trojan horse attacks, though it can be annoying when the .Pa /etc/ssh/ssh_known_hosts file is poorly maintained or when connections to new hosts are frequently made. This option forces the user to manually add all new hosts. If this flag is set to .Dq no , ssh will automatically add new host keys to the user known hosts files. If this flag is set to .Dq ask , new host keys will be added to the user known host files only after the user has confirmed that is what they really want to do, and ssh will refuse to connect to hosts whose host key has changed. The host keys of known hosts will be verified automatically in all cases. The argument must be .Dq yes , .Dq no , or .Dq ask . The default is .Dq ask . .It Cm TCPKeepAlive Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. .Pp The default is .Dq yes (to send TCP keepalive messages), and the client will notice if the network goes down or the remote host dies. This is important in scripts, and many users want it too. .Pp To disable TCP keepalive messages, the value should be set to .Dq no . .It Cm Tunnel Request .Xr tun 4 device forwarding between the client and the server. The argument must be .Dq yes , .Dq point-to-point (layer 3), .Dq ethernet (layer 2), or .Dq no . Specifying .Dq yes requests the default tunnel mode, which is .Dq point-to-point . The default is .Dq no . .It Cm TunnelDevice Specifies the .Xr tun 4 devices to open on the client .Pq Ar local_tun and the server .Pq Ar remote_tun . .Pp The argument must be .Sm off .Ar local_tun Op : Ar remote_tun . .Sm on The devices may be specified by numerical ID or the keyword .Dq any , which uses the next available tunnel device. If .Ar remote_tun is not specified, it defaults to .Dq any . The default is .Dq any:any . .It Cm UsePrivilegedPort Specifies whether to use a privileged port for outgoing connections. The argument must be .Dq yes or .Dq no . The default is .Dq no . If set to .Dq yes , .Xr ssh 1 must be setuid root. Note that this option must be set to .Dq yes for .Cm RhostsRSAAuthentication with older servers. .It Cm User Specifies the user to log in as. This can be useful when a different user name is used on different machines. This saves the trouble of having to remember to give the user name on the command line. .It Cm UserKnownHostsFile Specifies one or more files to use for the user host key database, separated by whitespace. The default is .Pa ~/.ssh/known_hosts , .Pa ~/.ssh/known_hosts2 . .It Cm VerifyHostKeyDNS Specifies whether to verify the remote key using DNS and SSHFP resource records. If this option is set to .Dq yes , the client will implicitly trust keys that match a secure fingerprint from DNS. Insecure fingerprints will be handled as if this option was set to .Dq ask . If this option is set to .Dq ask , information on fingerprint match will be displayed, but the user will still need to confirm new host keys according to the .Cm StrictHostKeyChecking option. The argument must be .Dq yes , .Dq no , or .Dq ask . The default is .Dq yes if compiled with LDNS and .Dq no otherwise. Note that this option applies to protocol version 2 only. .Pp See also VERIFYING HOST KEYS in .Xr ssh 1 . .It Cm VersionAddendum Specifies a string to append to the regular version string to identify OS- or site-specific modifications. The default is .Dq FreeBSD-20140420 . The value .Dq none may be used to disable this. .It Cm VisualHostKey If this flag is set to .Dq yes , an ASCII art representation of the remote host key fingerprint is printed in addition to the hex fingerprint string at login and for unknown host keys. If this flag is set to .Dq no , no fingerprint strings are printed at login and only the hex fingerprint string will be printed for unknown host keys. The default is .Dq no . .It Cm XAuthLocation Specifies the full pathname of the .Xr xauth 1 program. The default is .Pa /usr/local/bin/xauth . .El .Sh PATTERNS A .Em pattern consists of zero or more non-whitespace characters, .Sq * (a wildcard that matches zero or more characters), or .Sq ?\& (a wildcard that matches exactly one character). For example, to specify a set of declarations for any host in the .Dq .co.uk set of domains, the following pattern could be used: .Pp .Dl Host *.co.uk .Pp The following pattern would match any host in the 192.168.0.[0-9] network range: .Pp .Dl Host 192.168.0.? .Pp A .Em pattern-list is a comma-separated list of patterns. Patterns within pattern-lists may be negated by preceding them with an exclamation mark .Pq Sq !\& . For example, to allow a key to be used from anywhere within an organization except from the .Dq dialup pool, the following entry (in authorized_keys) could be used: .Pp .Dl from=\&"!*.dialup.example.com,*.example.com\&" .Sh FILES .Bl -tag -width Ds .It Pa ~/.ssh/config This is the per-user configuration file. The format of this file is described above. This file is used by the SSH client. Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not accessible by others. .It Pa /etc/ssh/ssh_config Systemwide configuration file. This file provides defaults for those values that are not specified in the user's configuration file, and for those users who do not have a configuration file. This file must be world-readable. .El .Sh SEE ALSO .Xr ssh 1 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Index: head/crypto/openssh/sshd.8 =================================================================== --- head/crypto/openssh/sshd.8 (revision 290670) +++ head/crypto/openssh/sshd.8 (revision 290671) @@ -1,993 +1,993 @@ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: sshd.8,v 1.273 2013/12/07 11:58:46 naddy Exp $ .\" $FreeBSD$ -.Dd December 7, 2013 +.Dd $Mdocdate: December 7 2013 $ .Dt SSHD 8 .Os .Sh NAME .Nm sshd .Nd OpenSSH SSH daemon .Sh SYNOPSIS .Nm sshd .Bk -words .Op Fl 46DdeiqTt .Op Fl b Ar bits .Op Fl C Ar connection_spec .Op Fl c Ar host_certificate_file .Op Fl E Ar log_file .Op Fl f Ar config_file .Op Fl g Ar login_grace_time .Op Fl h Ar host_key_file .Op Fl k Ar key_gen_time .Op Fl o Ar option .Op Fl p Ar port .Op Fl u Ar len .Ek .Sh DESCRIPTION .Nm (OpenSSH Daemon) is the daemon program for .Xr ssh 1 . Together these programs replace .Xr rlogin 1 and .Xr rsh 1 , and provide secure encrypted communications between two untrusted hosts over an insecure network. .Pp .Nm listens for connections from clients. It is normally started at boot from .Pa /etc/rc.d/sshd . It forks a new daemon for each incoming connection. The forked daemons handle key exchange, encryption, authentication, command execution, and data exchange. .Pp .Nm can be configured using command-line options or a configuration file (by default .Xr sshd_config 5 ) ; command-line options override values specified in the configuration file. .Nm rereads its configuration file when it receives a hangup signal, .Dv SIGHUP , by executing itself with the name and options it was started with, e.g.\& .Pa /usr/sbin/sshd . .Pp The options are as follows: .Bl -tag -width Ds .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl b Ar bits Specifies the number of bits in the ephemeral protocol version 1 server key (default 1024). .It Fl C Ar connection_spec Specify the connection parameters to use for the .Fl T extended test mode. If provided, any .Cm Match directives in the configuration file that would apply to the specified user, host, and address will be set before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs. The keywords are .Dq user , .Dq host , .Dq laddr , .Dq lport , and .Dq addr . All are required and may be supplied in any order, either with multiple .Fl C options or as a comma-separated list. .It Fl c Ar host_certificate_file Specifies a path to a certificate file to identify .Nm during key exchange. The certificate file must match a host key file specified using the .Fl h option or the .Cm HostKey configuration directive. .It Fl D When this option is specified, .Nm will not detach and does not become a daemon. This allows easy monitoring of .Nm sshd . .It Fl d Debug mode. The server sends verbose debug output to standard error, and does not put itself in the background. The server also will not fork and will only process one connection. This option is only intended for debugging for the server. Multiple .Fl d options increase the debugging level. Maximum is 3. .It Fl E Ar log_file Append debug logs to .Ar log_file instead of the system log. .It Fl e Write debug logs to standard error instead of the system log. .It Fl f Ar config_file Specifies the name of the configuration file. The default is .Pa /etc/ssh/sshd_config . .Nm refuses to start if there is no configuration file. .It Fl g Ar login_grace_time Gives the grace time for clients to authenticate themselves (default 120 seconds). If the client fails to authenticate the user within this many seconds, the server disconnects and exits. A value of zero indicates no limit. .It Fl h Ar host_key_file Specifies a file from which a host key is read. This option must be given if .Nm is not run as root (as the normal host key files are normally not readable by anyone but root). The default is .Pa /etc/ssh/ssh_host_key for protocol version 1, and .Pa /etc/ssh/ssh_host_dsa_key , .Pa /etc/ssh/ssh_host_ecdsa_key . .Pa /etc/ssh/ssh_host_ed25519_key and .Pa /etc/ssh/ssh_host_rsa_key for protocol version 2. It is possible to have multiple host key files for the different protocol versions and host key algorithms. .It Fl i Specifies that .Nm is being run from .Xr inetd 8 . .Nm is normally not run from inetd because it needs to generate the server key before it can respond to the client, and this may take tens of seconds. Clients would have to wait too long if the key was regenerated every time. However, with small key sizes (e.g. 512) using .Nm from inetd may be feasible. .It Fl k Ar key_gen_time Specifies how often the ephemeral protocol version 1 server key is regenerated (default 3600 seconds, or one hour). The motivation for regenerating the key fairly often is that the key is not stored anywhere, and after about an hour it becomes impossible to recover the key for decrypting intercepted communications even if the machine is cracked into or physically seized. A value of zero indicates that the key will never be regenerated. .It Fl o Ar option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options, and their values, see .Xr sshd_config 5 . .It Fl p Ar port Specifies the port on which the server listens for connections (default 22). Multiple port options are permitted. Ports specified in the configuration file with the .Cm Port option are ignored when a command-line port is specified. Ports specified using the .Cm ListenAddress option override command-line ports. .It Fl q Quiet mode. Nothing is sent to the system log. Normally the beginning, authentication, and termination of each connection is logged. .It Fl T Extended test mode. Check the validity of the configuration file, output the effective configuration to stdout and then exit. Optionally, .Cm Match rules may be applied by specifying the connection parameters using one or more .Fl C options. .It Fl t Test mode. Only check the validity of the configuration file and sanity of the keys. This is useful for updating .Nm reliably as configuration options may change. .It Fl u Ar len This option is used to specify the size of the field in the .Li utmp structure that holds the remote host name. If the resolved host name is longer than .Ar len , the dotted decimal value will be used instead. This allows hosts with very long host names that overflow this field to still be uniquely identified. Specifying .Fl u0 indicates that only dotted decimal addresses should be put into the .Pa utmp file. .Fl u0 may also be used to prevent .Nm from making DNS requests unless the authentication mechanism or configuration requires it. Authentication mechanisms that may require DNS include .Cm RhostsRSAAuthentication , .Cm HostbasedAuthentication , and using a .Cm from="pattern-list" option in a key file. Configuration options that require DNS include using a USER@HOST pattern in .Cm AllowUsers or .Cm DenyUsers . .El .Sh AUTHENTICATION The OpenSSH SSH daemon supports SSH protocols 1 and 2. The default is to use protocol 2 only, though this can be changed via the .Cm Protocol option in .Xr sshd_config 5 . Protocol 2 supports DSA, ECDSA, ED25519 and RSA keys; protocol 1 only supports RSA keys. For both protocols, each host has a host-specific key, normally 2048 bits, used to identify the host. .Pp Forward security for protocol 1 is provided through an additional server key, normally 768 bits, generated when the server starts. This key is normally regenerated every hour if it has been used, and is never stored on disk. Whenever a client connects, the daemon responds with its public host and server keys. The client compares the RSA host key against its own database to verify that it has not changed. The client then generates a 256-bit random number. It encrypts this random number using both the host key and the server key, and sends the encrypted number to the server. Both sides then use this random number as a session key which is used to encrypt all further communications in the session. The rest of the session is encrypted using a conventional cipher, currently Blowfish or 3DES, with 3DES being used by default. The client selects the encryption algorithm to use from those offered by the server. .Pp For protocol 2, forward security is provided through a Diffie-Hellman key agreement. This key agreement results in a shared session key. The rest of the session is encrypted using a symmetric cipher, currently 128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The client selects the encryption algorithm to use from those offered by the server. Additionally, session integrity is provided through a cryptographic message authentication code (hmac-md5, hmac-sha1, umac-64, umac-128, hmac-ripemd160, hmac-sha2-256 or hmac-sha2-512). .Pp Finally, the server and the client enter an authentication dialog. The client tries to authenticate itself using host-based authentication, public key authentication, challenge-response authentication, or password authentication. .Pp Regardless of the authentication type, the account is checked to ensure that it is accessible. An account is not accessible if it is locked, listed in .Cm DenyUsers or its group is listed in .Cm DenyGroups \&. The definition of a locked account is system dependant. Some platforms have their own account database (eg AIX) and some modify the passwd field ( .Ql \&*LK\&* on Solaris and UnixWare, .Ql \&* on HP-UX, containing .Ql Nologin on Tru64, a leading .Ql \&*LOCKED\&* on FreeBSD and a leading .Ql \&! on most Linuxes). If there is a requirement to disable password authentication for the account while allowing still public-key, then the passwd field should be set to something other than these values (eg .Ql NP or .Ql \&*NP\&* ). .Pp If the client successfully authenticates itself, a dialog for preparing the session is entered. At this time the client may request things like allocating a pseudo-tty, forwarding X11 connections, forwarding TCP connections, or forwarding the authentication agent connection over the secure channel. .Pp After this, the client either requests a shell or execution of a command. The sides then enter session mode. In this mode, either side may send data at any time, and such data is forwarded to/from the shell or command on the server side, and the user terminal in the client side. .Pp When the user program terminates and all forwarded X11 and other connections have been closed, the server sends command exit status to the client, and both sides exit. .Sh LOGIN PROCESS When a user successfully logs in, .Nm does the following: .Bl -enum -offset indent .It If the login is on a tty, and no command has been specified, prints last login time and .Pa /etc/motd (unless prevented in the configuration file or by .Pa ~/.hushlogin ; see the .Sx FILES section). .It If the login is on a tty, records login time. .It Checks .Pa /etc/nologin and .Pa /var/run/nologin ; if one exists, it prints the contents and quits (unless root). .It Changes to run with normal user privileges. .It Sets up basic environment. .It Reads the file .Pa ~/.ssh/environment , if it exists, and users are allowed to change their environment. See the .Cm PermitUserEnvironment option in .Xr sshd_config 5 . .It Changes to user's home directory. .It If .Pa ~/.ssh/rc exists, runs it; else if .Pa /etc/ssh/sshrc exists, runs it; otherwise runs .Xr xauth 1 . The .Dq rc files are given the X11 authentication protocol and cookie in standard input. See .Sx SSHRC , below. .It Runs user's shell or command. .El .Sh SSHRC If the file .Pa ~/.ssh/rc exists, .Xr sh 1 runs it after reading the environment files but before starting the user's shell or command. It must not produce any output on stdout; stderr must be used instead. If X11 forwarding is in use, it will receive the "proto cookie" pair in its standard input (and .Ev DISPLAY in its environment). The script must call .Xr xauth 1 because .Nm will not run xauth automatically to add X11 cookies. .Pp The primary purpose of this file is to run any initialization routines which may be needed before the user's home directory becomes accessible; AFS is a particular example of such an environment. .Pp This file will probably contain some initialization code followed by something similar to: .Bd -literal -offset 3n if read proto cookie && [ -n "$DISPLAY" ]; then if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then # X11UseLocalhost=yes echo add unix:`echo $DISPLAY | cut -c11-` $proto $cookie else # X11UseLocalhost=no echo add $DISPLAY $proto $cookie fi | xauth -q - fi .Ed .Pp If this file does not exist, .Pa /etc/ssh/sshrc is run, and if that does not exist either, xauth is used to add the cookie. .Sh AUTHORIZED_KEYS FILE FORMAT .Cm AuthorizedKeysFile specifies the files containing public keys for public key authentication; if none is specified, the default is .Pa ~/.ssh/authorized_keys and .Pa ~/.ssh/authorized_keys2 . Each line of the file contains one key (empty lines and lines starting with a .Ql # are ignored as comments). Protocol 1 public keys consist of the following space-separated fields: options, bits, exponent, modulus, comment. Protocol 2 public key consist of: options, keytype, base64-encoded key, comment. The options field is optional; its presence is determined by whether the line starts with a number or not (the options field never starts with a number). The bits, exponent, modulus, and comment fields give the RSA key for protocol version 1; the comment field is not used for anything (but may be convenient for the user to identify the key). For protocol version 2 the keytype is .Dq ecdsa-sha2-nistp256 , .Dq ecdsa-sha2-nistp384 , .Dq ecdsa-sha2-nistp521 , .Dq ssh-ed25519 , .Dq ssh-dss or .Dq ssh-rsa . .Pp Note that lines in this file are usually several hundred bytes long (because of the size of the public key encoding) up to a limit of 8 kilobytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16 kilobits. You don't want to type them in; instead, copy the .Pa identity.pub , .Pa id_dsa.pub , .Pa id_ecdsa.pub , .Pa id_ed25519.pub , or the .Pa id_rsa.pub file and edit it. .Pp .Nm enforces a minimum RSA key modulus size for protocol 1 and protocol 2 keys of 768 bits. .Pp The options (if present) consist of comma-separated option specifications. No spaces are permitted, except within double quotes. The following option specifications are supported (note that option keywords are case-insensitive): .Bl -tag -width Ds .It Cm cert-authority Specifies that the listed key is a certification authority (CA) that is trusted to validate signed certificates for user authentication. .Pp Certificates may encode access restrictions similar to these key options. If both certificate restrictions and key options are present, the most restrictive union of the two is applied. .It Cm command="command" Specifies that the command is executed whenever this key is used for authentication. The command supplied by the user (if any) is ignored. The command is run on a pty if the client requests a pty; otherwise it is run without a tty. If an 8-bit clean channel is required, one must not request a pty or should specify .Cm no-pty . A quote may be included in the command by quoting it with a backslash. This option might be useful to restrict certain public keys to perform just a specific operation. An example might be a key that permits remote backups but nothing else. Note that the client may specify TCP and/or X11 forwarding unless they are explicitly prohibited. The command originally supplied by the client is available in the .Ev SSH_ORIGINAL_COMMAND environment variable. Note that this option applies to shell, command or subsystem execution. Also note that this command may be superseded by either a .Xr sshd_config 5 .Cm ForceCommand directive or a command embedded in a certificate. .It Cm environment="NAME=value" Specifies that the string is to be added to the environment when logging in using this key. Environment variables set this way override other default environment values. Multiple options of this type are permitted. Environment processing is disabled by default and is controlled via the .Cm PermitUserEnvironment option. This option is automatically disabled if .Cm UseLogin is enabled. .It Cm from="pattern-list" Specifies that in addition to public key authentication, either the canonical name of the remote host or its IP address must be present in the comma-separated list of patterns. See PATTERNS in .Xr ssh_config 5 for more information on patterns. .Pp In addition to the wildcard matching that may be applied to hostnames or addresses, a .Cm from stanza may match IP addresses using CIDR address/masklen notation. .Pp The purpose of this option is to optionally increase security: public key authentication by itself does not trust the network or name servers or anything (but the key); however, if somebody somehow steals the key, the key permits an intruder to log in from anywhere in the world. This additional option makes using a stolen key more difficult (name servers and/or routers would have to be compromised in addition to just the key). .It Cm no-agent-forwarding Forbids authentication agent forwarding when this key is used for authentication. .It Cm no-port-forwarding Forbids TCP forwarding when this key is used for authentication. Any port forward requests by the client will return an error. This might be used, e.g. in connection with the .Cm command option. .It Cm no-pty Prevents tty allocation (a request to allocate a pty will fail). .It Cm no-user-rc Disables execution of .Pa ~/.ssh/rc . .It Cm no-X11-forwarding Forbids X11 forwarding when this key is used for authentication. Any X11 forward requests by the client will return an error. .It Cm permitopen="host:port" Limit local .Li ``ssh -L'' port forwarding such that it may only connect to the specified host and port. IPv6 addresses can be specified by enclosing the address in square brackets. Multiple .Cm permitopen options may be applied separated by commas. No pattern matching is performed on the specified hostnames, they must be literal domains or addresses. A port specification of .Cm * matches any port. .It Cm principals="principals" On a .Cm cert-authority line, specifies allowed principals for certificate authentication as a comma-separated list. At least one name from the list must appear in the certificate's list of principals for the certificate to be accepted. This option is ignored for keys that are not marked as trusted certificate signers using the .Cm cert-authority option. .It Cm tunnel="n" Force a .Xr tun 4 device on the server. Without this option, the next available device will be used if the client requests a tunnel. .El .Pp An example authorized_keys file: .Bd -literal -offset 3n # Comments allowed at start of line ssh-rsa AAAAB3Nza...LiPk== user@example.net from="*.sales.example.net,!pc.sales.example.net" ssh-rsa AAAAB2...19Q== john@example.net command="dump /home",no-pty,no-port-forwarding ssh-dss AAAAC3...51R== example.net permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss AAAAB5...21S== tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...== jane@example.net .Ed .Sh SSH_KNOWN_HOSTS FILE FORMAT The .Pa /etc/ssh/ssh_known_hosts and .Pa ~/.ssh/known_hosts files contain host public keys for all known hosts. The global file should be prepared by the administrator (optional), and the per-user file is maintained automatically: whenever the user connects from an unknown host, its key is added to the per-user file. .Pp Each line in these files contains the following fields: markers (optional), hostnames, bits, exponent, modulus, comment. The fields are separated by spaces. .Pp The marker is optional, but if it is present then it must be one of .Dq @cert-authority , to indicate that the line contains a certification authority (CA) key, or .Dq @revoked , to indicate that the key contained on the line is revoked and must not ever be accepted. Only one marker should be used on a key line. .Pp Hostnames is a comma-separated list of patterns .Pf ( Ql * and .Ql \&? act as wildcards); each pattern in turn is matched against the canonical host name (when authenticating a client) or against the user-supplied name (when authenticating a server). A pattern may also be preceded by .Ql \&! to indicate negation: if the host name matches a negated pattern, it is not accepted (by that line) even if it matched another pattern on the line. A hostname or address may optionally be enclosed within .Ql \&[ and .Ql \&] brackets then followed by .Ql \&: and a non-standard port number. .Pp Alternately, hostnames may be stored in a hashed form which hides host names and addresses should the file's contents be disclosed. Hashed hostnames start with a .Ql | character. Only one hashed hostname may appear on a single line and none of the above negation or wildcard operators may be applied. .Pp Bits, exponent, and modulus are taken directly from the RSA host key; they can be obtained, for example, from .Pa /etc/ssh/ssh_host_key.pub . The optional comment field continues to the end of the line, and is not used. .Pp Lines starting with .Ql # and empty lines are ignored as comments. .Pp When performing host authentication, authentication is accepted if any matching line has the proper key; either one that matches exactly or, if the server has presented a certificate for authentication, the key of the certification authority that signed the certificate. For a key to be trusted as a certification authority, it must use the .Dq @cert-authority marker described above. .Pp The known hosts file also provides a facility to mark keys as revoked, for example when it is known that the associated private key has been stolen. Revoked keys are specified by including the .Dq @revoked marker at the beginning of the key line, and are never accepted for authentication or as certification authorities, but instead will produce a warning from .Xr ssh 1 when they are encountered. .Pp It is permissible (but not recommended) to have several lines or different host keys for the same names. This will inevitably happen when short forms of host names from different domains are put in the file. It is possible that the files contain conflicting information; authentication is accepted if valid information can be found from either file. .Pp Note that the lines in these files are typically hundreds of characters long, and you definitely don't want to type in the host keys by hand. Rather, generate them by a script, .Xr ssh-keyscan 1 or by taking .Pa /etc/ssh/ssh_host_key.pub and adding the host names at the front. .Xr ssh-keygen 1 also offers some basic automated editing for .Pa ~/.ssh/known_hosts including removing hosts matching a host name and converting all host names to their hashed representations. .Pp An example ssh_known_hosts file: .Bd -literal -offset 3n # Comments allowed at start of line closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....= # A hashed hostname |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa AAAA1234.....= # A revoked key @revoked * ssh-rsa AAAAB5W... # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W... .Ed .Sh FILES .Bl -tag -width Ds -compact .It Pa ~/.hushlogin This file is used to suppress printing the last login time and .Pa /etc/motd , if .Cm PrintLastLog and .Cm PrintMotd , respectively, are enabled. It does not suppress printing of the banner specified by .Cm Banner . .Pp .It Pa ~/.rhosts This file is used for host-based authentication (see .Xr ssh 1 for more information). On some machines this file may need to be world-readable if the user's home directory is on an NFS partition, because .Nm reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. .Pp .It Pa ~/.shosts This file is used in exactly the same way as .Pa .rhosts , but allows host-based authentication without permitting login with rlogin/rsh. .Pp .It Pa ~/.ssh/ This directory is the default location for all user-specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. .Pp .It Pa ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, ED25519, RSA) that can be used for logging in as this user. The format of this file is described above. The content of the file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. .Pp If this file, the .Pa ~/.ssh directory, or the user's home directory are writable by other users, then the file could be modified or replaced by unauthorized users. In this case, .Nm will not allow it to be used unless the .Cm StrictModes option has been set to .Dq no . .Pp .It Pa ~/.ssh/environment This file is read into the environment at login (if it exists). It can only contain empty lines, comment lines (that start with .Ql # ) , and assignment lines of the form name=value. The file should be writable only by the user; it need not be readable by anyone else. Environment processing is disabled by default and is controlled via the .Cm PermitUserEnvironment option. .Pp .It Pa ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. The format of this file is described above. This file should be writable only by root/the owner and can, but need not be, world-readable. .Pp .It Pa ~/.ssh/rc Contains initialization routines to be run before the user's home directory becomes accessible. This file should be writable only by the user, and need not be readable by anyone else. .Pp .It Pa /etc/hosts.allow .It Pa /etc/hosts.deny Access controls that should be enforced by tcp-wrappers are defined here. Further details are described in .Xr hosts_access 5 . .Pp .It Pa /etc/hosts.equiv This file is for host-based authentication (see .Xr ssh 1 ) . It should only be writable by root. .Pp .It Pa /etc/moduli Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange". The file format is described in .Xr moduli 5 . .Pp .It Pa /etc/motd See .Xr motd 5 . .Pp .It Pa /etc/nologin If this file exists, .Nm refuses to let anyone except root log in. The contents of the file are displayed to anyone trying to log in, and non-root connections are refused. The file should be world-readable. .Pp .It Pa /etc/shosts.equiv This file is used in exactly the same way as .Pa hosts.equiv , but allows host-based authentication without permitting login with rlogin/rsh. .Pp .It Pa /etc/ssh/ssh_host_key .It Pa /etc/ssh/ssh_host_dsa_key .It Pa /etc/ssh/ssh_host_ecdsa_key .It Pa /etc/ssh/ssh_host_ed25519_key .It Pa /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys. These files should only be owned by root, readable only by root, and not accessible to others. Note that .Nm does not start if these files are group/world-accessible. .Pp .It Pa /etc/ssh/ssh_host_key.pub .It Pa /etc/ssh/ssh_host_dsa_key.pub .It Pa /etc/ssh/ssh_host_ecdsa_key.pub .It Pa /etc/ssh/ssh_host_ed25519_key.pub .It Pa /etc/ssh/ssh_host_rsa_key.pub These files contain the public parts of the host keys. These files should be world-readable but writable only by root. Their contents should match the respective private parts. These files are not really used for anything; they are provided for the convenience of the user so their contents can be copied to known hosts files. These files are created using .Xr ssh-keygen 1 . .Pp .It Pa /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. The format of this file is described above. This file should be writable only by root/the owner and should be world-readable. .Pp .It Pa /etc/ssh/sshd_config Contains configuration data for .Nm sshd . The file format and configuration options are described in .Xr sshd_config 5 . .Pp .It Pa /etc/ssh/sshrc Similar to .Pa ~/.ssh/rc , it can be used to specify machine-specific login-time initializations globally. This file should be writable only by root, and should be world-readable. .Pp .It Pa /var/empty .Xr chroot 2 directory used by .Nm during privilege separation in the pre-authentication phase. The directory should not contain any files and must be owned by root and not group or world-writable. .Pp .It Pa /var/run/sshd.pid Contains the process ID of the .Nm listening for connections (if there are several daemons running concurrently for different ports, this contains the process ID of the one started last). The content of this file is not sensitive; it can be world-readable. .El .Sh SEE ALSO .Xr scp 1 , .Xr sftp 1 , .Xr ssh 1 , .Xr ssh-add 1 , .Xr ssh-agent 1 , .Xr ssh-keygen 1 , .Xr ssh-keyscan 1 , .Xr chroot 2 , .Xr hosts_access 5 , .Xr login.conf 5 , .Xr moduli 5 , .Xr sshd_config 5 , .Xr inetd 8 , .Xr sftp-server 8 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support for privilege separation. .Sh CAVEATS System security is not improved unless .Nm rshd , .Nm rlogind , and .Nm rexecd are disabled (thus completely disabling .Xr rlogin and .Xr rsh into the machine). Index: head/crypto/openssh/sshd_config.5 =================================================================== --- head/crypto/openssh/sshd_config.5 (revision 290670) +++ head/crypto/openssh/sshd_config.5 (revision 290671) @@ -1,1393 +1,1393 @@ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: sshd_config.5,v 1.172 2014/02/27 22:47:07 djm Exp $ .\" $FreeBSD$ -.Dd March 22, 2015 +.Dd $Mdocdate: February 27 2014 $ .Dt SSHD_CONFIG 5 .Os .Sh NAME .Nm sshd_config .Nd OpenSSH SSH daemon configuration file .Sh SYNOPSIS .Nm /etc/ssh/sshd_config .Sh DESCRIPTION .Xr sshd 8 reads configuration data from .Pa /etc/ssh/sshd_config (or the file specified with .Fl f on the command line). The file contains keyword-argument pairs, one per line. Lines starting with .Ql # and empty lines are interpreted as comments. Arguments may optionally be enclosed in double quotes .Pq \&" in order to represent arguments containing spaces. .Pp The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive): .Bl -tag -width Ds .It Cm AcceptEnv Specifies what environment variables sent by the client will be copied into the session's .Xr environ 7 . See .Cm SendEnv in .Xr ssh_config 5 for how to configure the client. Note that environment passing is only supported for protocol 2. Variables are specified by name, which may contain the wildcard characters .Ql * and .Ql \&? . Multiple environment variables may be separated by whitespace or spread across multiple .Cm AcceptEnv directives. Be warned that some environment variables could be used to bypass restricted user environments. For this reason, care should be taken in the use of this directive. The default is not to accept any environment variables. .It Cm AddressFamily Specifies which address family should be used by .Xr sshd 8 . Valid arguments are .Dq any , .Dq inet (use IPv4 only), or .Dq inet6 (use IPv6 only). The default is .Dq any . .It Cm AllowAgentForwarding Specifies whether .Xr ssh-agent 1 forwarding is permitted. The default is .Dq yes . Note that disabling agent forwarding does not improve security unless users are also denied shell access, as they can always install their own forwarders. .It Cm AllowGroups This keyword can be followed by a list of group name patterns, separated by spaces. If specified, login is allowed only for users whose primary group or supplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm AllowTcpForwarding Specifies whether TCP forwarding is permitted. The available options are .Dq yes or .Dq all to allow TCP forwarding, .Dq no to prevent all TCP forwarding, .Dq local to allow local (from the perspective of .Xr ssh 1 ) forwarding only or .Dq remote to allow remote forwarding only. The default is .Dq yes . Note that disabling TCP forwarding does not improve security unless users are also denied shell access, as they can always install their own forwarders. .It Cm AllowUsers This keyword can be followed by a list of user name patterns, separated by spaces. If specified, login is allowed only for user names that match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm AuthenticationMethods Specifies the authentication methods that must be successfully completed for a user to be granted access. This option must be followed by one or more comma-separated lists of authentication method names. Successful authentication requires completion of every method in at least one of these lists. .Pp For example, an argument of .Dq publickey,password publickey,keyboard-interactive would require the user to complete public key authentication, followed by either password or keyboard interactive authentication. Only methods that are next in one or more lists are offered at each stage, so for this example, it would not be possible to attempt password or keyboard-interactive authentication before public key. .Pp For keyboard interactive authentication it is also possible to restrict authentication to a specific device by appending a colon followed by the device identifier .Dq bsdauth , .Dq pam , or .Dq skey , depending on the server configuration. For example, .Dq keyboard-interactive:bsdauth would restrict keyboard interactive authentication to the .Dq bsdauth device. .Pp This option is only available for SSH protocol 2 and will yield a fatal error if enabled if protocol 1 is also enabled. Note that each authentication method listed should also be explicitly enabled in the configuration. The default is not to require multiple authentication; successful completion of a single authentication method is sufficient. .It Cm AuthorizedKeysCommand Specifies a program to be used to look up the user's public keys. The program must be owned by root and not writable by group or others. It will be invoked with a single argument of the username being authenticated, and should produce on standard output zero or more lines of authorized_keys output (see AUTHORIZED_KEYS in .Xr sshd 8 ) . If a key supplied by AuthorizedKeysCommand does not successfully authenticate and authorize the user then public key authentication continues using the usual .Cm AuthorizedKeysFile files. By default, no AuthorizedKeysCommand is run. .It Cm AuthorizedKeysCommandUser Specifies the user under whose account the AuthorizedKeysCommand is run. It is recommended to use a dedicated user that has no other role on the host than running authorized keys commands. .It Cm AuthorizedKeysFile Specifies the file that contains the public keys that can be used for user authentication. The format is described in the AUTHORIZED_KEYS FILE FORMAT section of .Xr sshd 8 . .Cm AuthorizedKeysFile may contain tokens of the form %T which are substituted during connection setup. The following tokens are defined: %% is replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. After expansion, .Cm AuthorizedKeysFile is taken to be an absolute path or one relative to the user's home directory. Multiple files may be listed, separated by whitespace. The default is .Dq .ssh/authorized_keys .ssh/authorized_keys2 . .It Cm AuthorizedPrincipalsFile Specifies a file that lists principal names that are accepted for certificate authentication. When using certificates signed by a key listed in .Cm TrustedUserCAKeys , this file lists names, one of which must appear in the certificate for it to be accepted for authentication. Names are listed one per line preceded by key options (as described in AUTHORIZED_KEYS FILE FORMAT in .Xr sshd 8 ) . Empty lines and comments starting with .Ql # are ignored. .Pp .Cm AuthorizedPrincipalsFile may contain tokens of the form %T which are substituted during connection setup. The following tokens are defined: %% is replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. After expansion, .Cm AuthorizedPrincipalsFile is taken to be an absolute path or one relative to the user's home directory. .Pp The default is .Dq none , i.e. not to use a principals file \(en in this case, the username of the user must appear in a certificate's principals list for it to be accepted. Note that .Cm AuthorizedPrincipalsFile is only used when authentication proceeds using a CA listed in .Cm TrustedUserCAKeys and is not consulted for certification authorities trusted via .Pa ~/.ssh/authorized_keys , though the .Cm principals= key option offers a similar facility (see .Xr sshd 8 for details). .It Cm Banner The contents of the specified file are sent to the remote user before authentication is allowed. If the argument is .Dq none then no banner is displayed. This option is only available for protocol version 2. By default, no banner is displayed. .It Cm ChallengeResponseAuthentication Specifies whether challenge-response authentication is allowed (e.g. via PAM or though authentication styles supported in .Xr login.conf 5 ) The default is .Dq yes . .It Cm ChrootDirectory Specifies the pathname of a directory to .Xr chroot 2 to after authentication. All components of the pathname must be root-owned directories that are not writable by any other user or group. After the chroot, .Xr sshd 8 changes the working directory to the user's home directory. .Pp The pathname may contain the following tokens that are expanded at runtime once the connecting user has been authenticated: %% is replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. .Pp The .Cm ChrootDirectory must contain the necessary files and directories to support the user's session. For an interactive session this requires at least a shell, typically .Xr sh 1 , and basic .Pa /dev nodes such as .Xr null 4 , .Xr zero 4 , .Xr stdin 4 , .Xr stdout 4 , .Xr stderr 4 , .Xr arandom 4 and .Xr tty 4 devices. For file transfer sessions using .Dq sftp , no additional configuration of the environment is necessary if the in-process sftp server is used, though sessions which use logging do require .Pa /dev/log inside the chroot directory (see .Xr sftp-server 8 for details). .Pp The default is not to .Xr chroot 2 . .It Cm Ciphers Specifies the ciphers allowed for protocol version 2. Multiple ciphers must be comma-separated. The supported ciphers are: .Pp .Dq 3des-cbc , .Dq aes128-cbc , .Dq aes192-cbc , .Dq aes256-cbc , .Dq aes128-ctr , .Dq aes192-ctr , .Dq aes256-ctr , .Dq aes128-gcm@openssh.com , .Dq aes256-gcm@openssh.com , .Dq arcfour128 , .Dq arcfour256 , .Dq arcfour , .Dq blowfish-cbc , .Dq cast128-cbc , and .Dq chacha20-poly1305@openssh.com . .Pp The default is: .Bd -literal -offset 3n aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, aes128-gcm@openssh.com,aes256-gcm@openssh.com, chacha20-poly1305@openssh.com, aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, aes256-cbc,arcfour .Ed .Pp The list of available ciphers may also be obtained using the .Fl Q option of .Xr ssh 1 . .It Cm ClientAliveCountMax Sets the number of client alive messages (see below) which may be sent without .Xr sshd 8 receiving any messages back from the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of client alive messages is very different from .Cm TCPKeepAlive (below). The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by .Cm TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. .Pp The default value is 3. If .Cm ClientAliveInterval (see below) is set to 15, and .Cm ClientAliveCountMax is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds. This option applies to protocol version 2 only. .It Cm ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, .Xr sshd 8 will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. This option applies to protocol version 2 only. .It Cm Compression Specifies whether compression is allowed, or delayed until the user has authenticated successfully. The argument must be .Dq yes , .Dq delayed , or .Dq no . The default is .Dq delayed . .It Cm DenyGroups This keyword can be followed by a list of group name patterns, separated by spaces. Login is disallowed for users whose primary group or supplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm DenyUsers This keyword can be followed by a list of user name patterns, separated by spaces. Login is disallowed for user names that match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm ForceCommand Forces the execution of the command specified by .Cm ForceCommand , ignoring any command supplied by the client and .Pa ~/.ssh/rc if present. The command is invoked by using the user's login shell with the -c option. This applies to shell, command, or subsystem execution. It is most useful inside a .Cm Match block. The command originally supplied by the client is available in the .Ev SSH_ORIGINAL_COMMAND environment variable. Specifying a command of .Dq internal-sftp will force the use of an in-process sftp server that requires no support files when used with .Cm ChrootDirectory . .It Cm GatewayPorts Specifies whether remote hosts are allowed to connect to ports forwarded for the client. By default, .Xr sshd 8 binds remote port forwardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. .Cm GatewayPorts can be used to specify that sshd should allow remote port forwardings to bind to non-loopback addresses, thus allowing other hosts to connect. The argument may be .Dq no to force remote port forwardings to be available to the local host only, .Dq yes to force remote port forwardings to bind to the wildcard address, or .Dq clientspecified to allow the client to select the address to which the forwarding is bound. The default is .Dq no . .It Cm GSSAPIAuthentication Specifies whether user authentication based on GSSAPI is allowed. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm GSSAPICleanupCredentials Specifies whether to automatically destroy the user's credentials cache on logout. The default is .Dq yes . Note that this option applies to protocol version 2 only. .It Cm HostbasedAuthentication Specifies whether rhosts or /etc/hosts.equiv authentication together with successful public key client host authentication is allowed (host-based authentication). This option is similar to .Cm RhostsRSAAuthentication and applies to protocol version 2 only. The default is .Dq no . .It Cm HostbasedUsesNameFromPacketOnly Specifies whether or not the server will attempt to perform a reverse name lookup when matching the name in the .Pa ~/.shosts , .Pa ~/.rhosts , and .Pa /etc/hosts.equiv files during .Cm HostbasedAuthentication . A setting of .Dq yes means that .Xr sshd 8 uses the name supplied by the client rather than attempting to resolve the name from the TCP connection itself. The default is .Dq no . .It Cm HostCertificate Specifies a file containing a public host certificate. The certificate's public key must match a private host key already specified by .Cm HostKey . The default behaviour of .Xr sshd 8 is not to load any certificates. .It Cm HostKey Specifies a file containing a private host key used by SSH. The default is .Pa /etc/ssh/ssh_host_key for protocol version 1, and .Pa /etc/ssh/ssh_host_dsa_key , .Pa /etc/ssh/ssh_host_ecdsa_key , .Pa /etc/ssh/ssh_host_ed25519_key and .Pa /etc/ssh/ssh_host_rsa_key for protocol version 2. Note that .Xr sshd 8 will refuse to use a file if it is group/world-accessible. It is possible to have multiple host key files. .Dq rsa1 keys are used for version 1 and .Dq dsa , .Dq ecdsa , .Dq ed25519 or .Dq rsa are used for version 2 of the SSH protocol. It is also possible to specify public host key files instead. In this case operations on the private key will be delegated to an .Xr ssh-agent 1 . .It Cm HostKeyAgent Identifies the UNIX-domain socket used to communicate with an agent that has access to the private host keys. If .Dq SSH_AUTH_SOCK is specified, the location of the socket will be read from the .Ev SSH_AUTH_SOCK environment variable. .It Cm IgnoreRhosts Specifies that .Pa .rhosts and .Pa .shosts files will not be used in .Cm RhostsRSAAuthentication or .Cm HostbasedAuthentication . .Pp .Pa /etc/hosts.equiv and .Pa /etc/ssh/shosts.equiv are still used. The default is .Dq yes . .It Cm IgnoreUserKnownHosts Specifies whether .Xr sshd 8 should ignore the user's .Pa ~/.ssh/known_hosts during .Cm RhostsRSAAuthentication or .Cm HostbasedAuthentication . The default is .Dq no . .It Cm IPQoS Specifies the IPv4 type-of-service or DSCP class for the connection. Accepted values are .Dq af11 , .Dq af12 , .Dq af13 , .Dq af21 , .Dq af22 , .Dq af23 , .Dq af31 , .Dq af32 , .Dq af33 , .Dq af41 , .Dq af42 , .Dq af43 , .Dq cs0 , .Dq cs1 , .Dq cs2 , .Dq cs3 , .Dq cs4 , .Dq cs5 , .Dq cs6 , .Dq cs7 , .Dq ef , .Dq lowdelay , .Dq throughput , .Dq reliability , or a numeric value. This option may take one or two arguments, separated by whitespace. If one argument is specified, it is used as the packet class unconditionally. If two values are specified, the first is automatically selected for interactive sessions and the second for non-interactive sessions. The default is .Dq lowdelay for interactive sessions and .Dq throughput for non-interactive sessions. .It Cm KbdInteractiveAuthentication Specifies whether to allow keyboard-interactive authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is to use whatever value .Cm ChallengeResponseAuthentication is set to (by default .Dq yes ) . .It Cm KerberosAuthentication Specifies whether the password provided by the user for .Cm PasswordAuthentication will be validated through the Kerberos KDC. To use this option, the server needs a Kerberos servtab which allows the verification of the KDC's identity. The default is .Dq no . .It Cm KerberosGetAFSToken If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire an AFS token before accessing the user's home directory. The default is .Dq no . .It Cm KerberosOrLocalPasswd If password authentication through Kerberos fails then the password will be validated via any additional local mechanism such as .Pa /etc/passwd . The default is .Dq yes . .It Cm KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache file on logout. The default is .Dq yes . .It Cm KexAlgorithms Specifies the available KEX (Key Exchange) algorithms. Multiple algorithms must be comma-separated. The default is .Bd -literal -offset indent curve25519-sha256@libssh.org, ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521, diffie-hellman-group-exchange-sha256, diffie-hellman-group-exchange-sha1, diffie-hellman-group14-sha1, diffie-hellman-group1-sha1 .Ed .It Cm KeyRegenerationInterval In protocol version 1, the ephemeral server key is automatically regenerated after this many seconds (if it has been used). The purpose of regeneration is to prevent decrypting captured sessions by later breaking into the machine and stealing the keys. The key is never stored anywhere. If the value is 0, the key is never regenerated. The default is 3600 (seconds). .It Cm ListenAddress Specifies the local addresses .Xr sshd 8 should listen on. The following forms may be used: .Pp .Bl -item -offset indent -compact .It .Cm ListenAddress .Sm off .Ar host No | Ar IPv4_addr No | Ar IPv6_addr .Sm on .It .Cm ListenAddress .Sm off .Ar host No | Ar IPv4_addr No : Ar port .Sm on .It .Cm ListenAddress .Sm off .Oo .Ar host No | Ar IPv6_addr Oc : Ar port .Sm on .El .Pp If .Ar port is not specified, sshd will listen on the address and all prior .Cm Port options specified. The default is to listen on all local addresses. Multiple .Cm ListenAddress options are permitted. Additionally, any .Cm Port options must precede this option for non-port qualified addresses. .It Cm LoginGraceTime The server disconnects after this time if the user has not successfully logged in. If the value is 0, there is no time limit. The default is 120 seconds. .It Cm LogLevel Gives the verbosity level that is used when logging messages from .Xr sshd 8 . The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of debugging output. Logging with a DEBUG level violates the privacy of users and is not recommended. .It Cm MACs Specifies the available MAC (message authentication code) algorithms. The MAC algorithm is used in protocol version 2 for data integrity protection. Multiple algorithms must be comma-separated. The algorithms that contain .Dq -etm calculate the MAC after encryption (encrypt-then-mac). These are considered safer and their use recommended. The default is: .Bd -literal -offset indent hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com, umac-64-etm@openssh.com,umac-128-etm@openssh.com, hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com, hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com, hmac-md5-96-etm@openssh.com, hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com, hmac-sha2-256,hmac-sha2-512,hmac-ripemd160, hmac-sha1-96,hmac-md5-96 .Ed .It Cm Match Introduces a conditional block. If all of the criteria on the .Cm Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another .Cm Match line or the end of the file. If a keyword appears in multiple .Cm Match blocks that are satisified, only the first instance of the keyword is applied. .Pp The arguments to .Cm Match are one or more criteria-pattern pairs or the single token .Cm All which matches all criteria. The available criteria are .Cm User , .Cm Group , .Cm Host , .Cm LocalAddress , .Cm LocalPort , and .Cm Address . The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNS section of .Xr ssh_config 5 . .Pp The patterns in an .Cm Address criteria may additionally contain addresses to match in CIDR address/masklen format, e.g.\& .Dq 192.0.2.0/24 or .Dq 3ffe:ffff::/32 . Note that the mask length provided must be consistent with the address - it is an error to specify a mask length that is too long for the address or one with bits set in this host portion of the address. For example, .Dq 192.0.2.0/33 and .Dq 192.0.2.0/8 respectively. .Pp Only a subset of keywords may be used on the lines following a .Cm Match keyword. Available keywords are .Cm AcceptEnv , .Cm AllowAgentForwarding , .Cm AllowGroups , .Cm AllowTcpForwarding , .Cm AllowUsers , .Cm AuthenticationMethods , .Cm AuthorizedKeysCommand , .Cm AuthorizedKeysCommandUser , .Cm AuthorizedKeysFile , .Cm AuthorizedPrincipalsFile , .Cm Banner , .Cm ChrootDirectory , .Cm DenyGroups , .Cm DenyUsers , .Cm ForceCommand , .Cm GatewayPorts , .Cm GSSAPIAuthentication , .Cm HostbasedAuthentication , .Cm HostbasedUsesNameFromPacketOnly , .Cm KbdInteractiveAuthentication , .Cm KerberosAuthentication , .Cm MaxAuthTries , .Cm MaxSessions , .Cm PasswordAuthentication , .Cm PermitEmptyPasswords , .Cm PermitOpen , .Cm PermitRootLogin , .Cm PermitTTY , .Cm PermitTunnel , .Cm PubkeyAuthentication , .Cm RekeyLimit , .Cm RhostsRSAAuthentication , .Cm RSAAuthentication , .Cm X11DisplayOffset , .Cm X11Forwarding and .Cm X11UseLocalHost . .It Cm MaxAuthTries Specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures are logged. The default is 6. .It Cm MaxSessions Specifies the maximum number of open sessions permitted per network connection. The default is 10. .It Cm MaxStartups Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the .Cm LoginGraceTime expires for a connection. The default is 10:30:100. .Pp Alternatively, random early drop can be enabled by specifying the three colon separated values .Dq start:rate:full (e.g. "10:30:60"). .Xr sshd 8 will refuse connection attempts with a probability of .Dq rate/100 (30%) if there are currently .Dq start (10) unauthenticated connections. The probability increases linearly and all connection attempts are refused if the number of unauthenticated connections reaches .Dq full (60). .It Cm PasswordAuthentication Specifies whether password authentication is allowed. See also .Cm UsePAM . The default is .Dq no . .It Cm PermitEmptyPasswords When password authentication is allowed, it specifies whether the server allows login to accounts with empty password strings. The default is .Dq no . .It Cm PermitOpen Specifies the destinations to which TCP port forwarding is permitted. The forwarding specification must be one of the following forms: .Pp .Bl -item -offset indent -compact .It .Cm PermitOpen .Sm off .Ar host : port .Sm on .It .Cm PermitOpen .Sm off .Ar IPv4_addr : port .Sm on .It .Cm PermitOpen .Sm off .Ar \&[ IPv6_addr \&] : port .Sm on .El .Pp Multiple forwards may be specified by separating them with whitespace. An argument of .Dq any can be used to remove all restrictions and permit any forwarding requests. An argument of .Dq none can be used to prohibit all forwarding requests. By default all port forwarding requests are permitted. .It Cm PermitRootLogin Specifies whether root can log in using .Xr ssh 1 . The argument must be .Dq yes , .Dq without-password , .Dq forced-commands-only , or .Dq no . The default is .Dq no . Note that if .Cm ChallengeResponseAuthentication is .Dq yes , the root user may be allowed in with its password even if .Cm PermitRootLogin is set to .Dq without-password . .Pp If this option is set to .Dq without-password , password authentication is disabled for root. .Pp If this option is set to .Dq forced-commands-only , root login with public key authentication will be allowed, but only if the .Ar command option has been specified (which may be useful for taking remote backups even if root login is normally not allowed). All other authentication methods are disabled for root. .Pp If this option is set to .Dq no , root is not allowed to log in. .It Cm PermitTunnel Specifies whether .Xr tun 4 device forwarding is allowed. The argument must be .Dq yes , .Dq point-to-point (layer 3), .Dq ethernet (layer 2), or .Dq no . Specifying .Dq yes permits both .Dq point-to-point and .Dq ethernet . The default is .Dq no . .It Cm PermitTTY Specifies whether .Xr pty 4 allocation is permitted. The default is .Dq yes . .It Cm PermitUserEnvironment Specifies whether .Pa ~/.ssh/environment and .Cm environment= options in .Pa ~/.ssh/authorized_keys are processed by .Xr sshd 8 . The default is .Dq no . Enabling environment processing may enable users to bypass access restrictions in some configurations using mechanisms such as .Ev LD_PRELOAD . .It Cm PidFile Specifies the file that contains the process ID of the SSH daemon. The default is .Pa /var/run/sshd.pid . .It Cm Port Specifies the port number that .Xr sshd 8 listens on. The default is 22. Multiple options of this type are permitted. See also .Cm ListenAddress . .It Cm PrintLastLog Specifies whether .Xr sshd 8 should print the date and time of the last user login when a user logs in interactively. The default is .Dq yes . .It Cm PrintMotd Specifies whether .Xr sshd 8 should print .Pa /etc/motd when a user logs in interactively. (On some systems it is also printed by the shell, .Pa /etc/profile , or equivalent.) The default is .Dq yes . .It Cm Protocol Specifies the protocol versions .Xr sshd 8 supports. The possible values are .Sq 1 and .Sq 2 . Multiple versions must be comma-separated. The default is .Sq 2 . Note that the order of the protocol list does not indicate preference, because the client selects among multiple protocol versions offered by the server. Specifying .Dq 2,1 is identical to .Dq 1,2 . .It Cm PubkeyAuthentication Specifies whether public key authentication is allowed. The default is .Dq yes . Note that this option applies to protocol version 2 only. .It Cm RekeyLimit Specifies the maximum amount of data that may be transmitted before the session key is renegotiated, optionally followed a maximum amount of time that may pass before the session key is renegotiated. The first argument is specified in bytes and may have a suffix of .Sq K , .Sq M , or .Sq G to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between .Sq 1G and .Sq 4G , depending on the cipher. The optional second value is specified in seconds and may use any of the units documented in the .Sx TIME FORMATS section. The default value for .Cm RekeyLimit is .Dq default none , which means that rekeying is performed after the cipher's default amount of data has been sent or received and no time based rekeying is done. This option applies to protocol version 2 only. .It Cm RevokedKeys Specifies revoked public keys. Keys listed in this file will be refused for public key authentication. Note that if this file is not readable, then public key authentication will be refused for all users. Keys may be specified as a text file, listing one public key per line, or as an OpenSSH Key Revocation List (KRL) as generated by .Xr ssh-keygen 1 . For more information on KRLs, see the KEY REVOCATION LISTS section in .Xr ssh-keygen 1 . .It Cm RhostsRSAAuthentication Specifies whether rhosts or .Pa /etc/hosts.equiv authentication together with successful RSA host authentication is allowed. The default is .Dq no . This option applies to protocol version 1 only. .It Cm RSAAuthentication Specifies whether pure RSA authentication is allowed. The default is .Dq yes . This option applies to protocol version 1 only. .It Cm ServerKeyBits Defines the number of bits in the ephemeral protocol version 1 server key. The minimum value is 512, and the default is 1024. .It Cm StrictModes Specifies whether .Xr sshd 8 should check file modes and ownership of the user's files and home directory before accepting login. This is normally desirable because novices sometimes accidentally leave their directory or files world-writable. The default is .Dq yes . Note that this does not apply to .Cm ChrootDirectory , whose permissions and ownership are checked unconditionally. .It Cm Subsystem Configures an external subsystem (e.g. file transfer daemon). Arguments should be a subsystem name and a command (with optional arguments) to execute upon subsystem request. .Pp The command .Xr sftp-server 8 implements the .Dq sftp file transfer subsystem. .Pp Alternately the name .Dq internal-sftp implements an in-process .Dq sftp server. This may simplify configurations using .Cm ChrootDirectory to force a different filesystem root on clients. .Pp By default no subsystems are defined. Note that this option applies to protocol version 2 only. .It Cm SyslogFacility Gives the facility code that is used when logging messages from .Xr sshd 8 . The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH. .It Cm TCPKeepAlive Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. On the other hand, if TCP keepalives are not sent, sessions may hang indefinitely on the server, leaving .Dq ghost users and consuming server resources. .Pp The default is .Dq yes (to send TCP keepalive messages), and the server will notice if the network goes down or the client host crashes. This avoids infinitely hanging sessions. .Pp To disable TCP keepalive messages, the value should be set to .Dq no . .It Cm TrustedUserCAKeys Specifies a file containing public keys of certificate authorities that are trusted to sign user certificates for authentication. Keys are listed one per line; empty lines and comments starting with .Ql # are allowed. If a certificate is presented for authentication and has its signing CA key listed in this file, then it may be used for authentication for any user listed in the certificate's principals list. Note that certificates that lack a list of principals will not be permitted for authentication using .Cm TrustedUserCAKeys . For more details on certificates, see the CERTIFICATES section in .Xr ssh-keygen 1 . .It Cm UseDNS Specifies whether .Xr sshd 8 should look up the remote host name and check that the resolved host name for the remote IP address maps back to the very same IP address. The default is .Dq yes . .It Cm UseLogin Specifies whether .Xr login 1 is used for interactive login sessions. The default is .Dq no . Note that .Xr login 1 is never used for remote command execution. Note also, that if this is enabled, .Cm X11Forwarding will be disabled because .Xr login 1 does not know how to handle .Xr xauth 1 cookies. If .Cm UsePrivilegeSeparation is specified, it will be disabled after authentication. .It Cm UsePAM Enables the Pluggable Authentication Module interface. If set to .Dq yes this will enable PAM authentication using .Cm ChallengeResponseAuthentication and .Cm PasswordAuthentication in addition to PAM account and session module processing for all authentication types. .Pp Because PAM challenge-response authentication usually serves an equivalent role to password authentication, you should disable either .Cm PasswordAuthentication or .Cm ChallengeResponseAuthentication. .Pp If .Cm UsePAM is enabled, you will not be able to run .Xr sshd 8 as a non-root user. The default is .Dq yes . .It Cm UsePrivilegeSeparation Specifies whether .Xr sshd 8 separates privileges by creating an unprivileged child process to deal with incoming network traffic. After successful authentication, another process will be created that has the privilege of the authenticated user. The goal of privilege separation is to prevent privilege escalation by containing any corruption within the unprivileged processes. The default is .Dq sandbox . If .Cm UsePrivilegeSeparation is set to .Dq sandbox then the pre-authentication unprivileged process is subject to additional restrictions. .It Cm VersionAddendum Optionally specifies additional text to append to the SSH protocol banner sent by the server upon connection. The default is .Dq FreeBSD-20140420 . The value .Dq none may be used to disable this. .It Cm X11DisplayOffset Specifies the first display number available for .Xr sshd 8 Ns 's X11 forwarding. This prevents sshd from interfering with real X11 servers. The default is 10. .It Cm X11Forwarding Specifies whether X11 forwarding is permitted. The argument must be .Dq yes or .Dq no . The default is .Dq yes . .Pp When X11 forwarding is enabled, there may be additional exposure to the server and to client displays if the .Xr sshd 8 proxy display is configured to listen on the wildcard address (see .Cm X11UseLocalhost below), though this is not the default. Additionally, the authentication spoofing and authentication data verification and substitution occur on the client side. The security risk of using X11 forwarding is that the client's X11 display server may be exposed to attack when the SSH client requests forwarding (see the warnings for .Cm ForwardX11 in .Xr ssh_config 5 ) . A system administrator may have a stance in which they want to protect clients that may expose themselves to attack by unwittingly requesting X11 forwarding, which can warrant a .Dq no setting. .Pp Note that disabling X11 forwarding does not prevent users from forwarding X11 traffic, as users can always install their own forwarders. X11 forwarding is automatically disabled if .Cm UseLogin is enabled. .It Cm X11UseLocalhost Specifies whether .Xr sshd 8 should bind the X11 forwarding server to the loopback address or to the wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the hostname part of the .Ev DISPLAY environment variable to .Dq localhost . This prevents remote hosts from connecting to the proxy display. However, some older X11 clients may not function with this configuration. .Cm X11UseLocalhost may be set to .Dq no to specify that the forwarding server should be bound to the wildcard address. The argument must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm XAuthLocation Specifies the full pathname of the .Xr xauth 1 program. The default is .Pa /usr/local/bin/xauth . .El .Sh TIME FORMATS .Xr sshd 8 command-line arguments and configuration file options that specify time may be expressed using a sequence of the form: .Sm off .Ar time Op Ar qualifier , .Sm on where .Ar time is a positive integer value and .Ar qualifier is one of the following: .Pp .Bl -tag -width Ds -compact -offset indent .It Aq Cm none seconds .It Cm s | Cm S seconds .It Cm m | Cm M minutes .It Cm h | Cm H hours .It Cm d | Cm D days .It Cm w | Cm W weeks .El .Pp Each member of the sequence is added together to calculate the total time value. .Pp Time format examples: .Pp .Bl -tag -width Ds -compact -offset indent .It 600 600 seconds (10 minutes) .It 10m 10 minutes .It 1h30m 1 hour 30 minutes (90 minutes) .El .Sh FILES .Bl -tag -width Ds .It Pa /etc/ssh/sshd_config Contains configuration data for .Xr sshd 8 . This file should be writable by root only, but it is recommended (though not necessary) that it be world-readable. .El .Sh SEE ALSO .Xr sshd 8 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support for privilege separation.