Page MenuHomeFreeBSD
Differential D23130 Diff 66659 head/lib/libc/sys/getrandom.2

Changeset View

Standalone View

View Options

head/lib/libc/sys/getrandom.2

.\" Copyright (c) 2018 Conrad Meyer <cem@FreeBSD.org> .\" Copyright 2020, 2018 Conrad Meyer <cem@FreeBSD.org>. All rights reserved.
.\" All rights reserved.
.\" .\"
.\" Redistribution and use in source and binary forms, with or without .\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions .\" modification, are permitted provided that the following conditions
.\" are met: .\" are met:
.\" 1. Redistributions of source code must retain the above copyright .\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer. .\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright .\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the .\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution. .\" documentation and/or other materials provided with the distribution.
.\" .\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" 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 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd February 24, 2018 .Dd January 12, 2020
.Dt GETRANDOM 2 .Dt GETRANDOM 2
.Os .Os
.Sh NAME .Sh NAME
.Nm getrandom .Nm getrandom
.Nd get random data .Nd get random data
.Sh LIBRARY .Sh LIBRARY
.Lb libc .Lb libc
.Sh SYNOPSIS .Sh SYNOPSIS
Show All 23 Lines
will block until the device is seeded. will block until the device is seeded.
.It Ql GRND_RANDOM .It Ql GRND_RANDOM
This flag does nothing on This flag does nothing on
.Fx . .Fx .
.Pa /dev/random .Pa /dev/random
and and
.Pa /dev/urandom .Pa /dev/urandom
are identical. are identical.
.It Ql GRND_INSECURE
This flag is treated as an alternative name for
.Dv GRND_NONBLOCK .
It is provided solely for API compatibility with Linux.
.El .El
.Pp .Pp
If the If the
.Xr random 4 .Xr random 4
device has been seeded, reads of up to 256 bytes will always return as many device has been seeded, reads of up to 256 bytes will always return as many
bytes as requested and will not be interrupted by signals. bytes as requested and will not be interrupted by signals.
.Pp
.Sh RETURN VALUES .Sh RETURN VALUES
Upon successful completion, the number of bytes which were actually read is Upon successful completion, the number of bytes which were actually read is
returned. returned.
For requests larger than 256 bytes, this can be fewer bytes than were For requests larger than 256 bytes, this can be fewer bytes than were
requested. requested.
Otherwise, -1 is returned and the global variable Otherwise, -1 is returned and the global variable
.Va errno .Va errno
is set to indicate the error. is set to indicate the error.
.Sh ERRORS .Sh ERRORS
The The
.Fn getrandom .Fn getrandom
operation returns the following errors: operation returns the following errors:
.Bl -tag -width Er .Bl -tag -width Er
.It Bq Er EAGAIN .It Bq Er EAGAIN
The The
.Ql GRND_NONBLOCK .Ql GRND_NONBLOCK
(or
.Ql GRND_INSECURE )
flag was set and the flag was set and the
.Xr random 4 .Xr random 4
device was not yet seeded. device was not yet seeded.
.It Bq Er EFAULT .It Bq Er EFAULT
The The
.Fa buf .Fa buf
parameter points to an invalid address. parameter points to an invalid address.
.It Bq Er EINTR .It Bq Er EINTR
The sleep was interrupted by a signal. The sleep was interrupted by a signal.
.It Bq Er EINVAL .It Bq Er EINVAL
An invalid An invalid
.Fa flags .Fa flags
was specified. was specified.
.It Bq Er EINVAL .It Bq Er EINVAL
The requested The requested
.Fa buflen .Fa buflen
was larger than was larger than
.Dv IOSIZE_MAX . .Dv IOSIZE_MAX .
.El .El
.Sh SEE ALSO .Sh SEE ALSO
.Xr arc4random 3 , .Xr arc4random 3 ,
.Xr getentropy 3 , .Xr getentropy 3 ,
.Xr random 4 .Xr random 4
.Sh STANDARDS .Sh STANDARDS
.Fn getentropy .Fn getrandom
is non-standard. is non-standard.
It is present in Linux. It is present in Linux.
.Sh HISTORY .Sh HISTORY
The The
.Fn getrandom .Fn getrandom
system call first appeared in system call first appeared in
.Fx 12.0 . .Fx 12.0 .
.Sh CAVEATS
Unlike Linux, the
.Dv GRND_INSECURE
flag on
.Fx
does not produce any output before the
.Xr random 4
device is seeded.