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lib/libcasper/services/cap_dns/cap_dns.3

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.\" Copyright (c) 2018 Mariusz Zaborski <oshogbo@FreeBSD.org>
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.Dd January 5, 2018
.Dt CAP_DNS 3
.Os
.Sh NAME
.Nm cap_gethostbyname ,
.Nm cap_gethostbyname2 ,
.Nm cap_gethostbyaddr ,
.Nm cap_getnameinfo ,
.Nm cap_dns_type_limit ,
.Nm cap_dns_family_limit
.Nd "library for getting network host entry in capability mode"
.Sh LIBRARY
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s/capabilitie/capability/

bcr: s/capabilitie/capability/
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geting -> getting

brueffer: geting -> getting
.Lb libcap_dns
.Sh SYNOPSIS
.In sys/nv.h
.In libcasper.h
.In casper/cap_dns.h
.Ft "struct hostent *"
.Fn cap_gethostbyname "const cap_channel_t *chan" "const char *name"
.Ft "struct hostent *"
.Fn cap_gethostbyname2 "const cap_channel_t *chan" "const char *name" "int af"
.Ft "struct hostent *"
.Fn cap_gethostbyaddr "const cap_channel_t *chan" "const void *addr" "socklen_t len" "int af"
.Ft "int"
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The cap_getnameinfo() signature is missing.

brueffer: The cap_getnameinfo() signature is missing.
.Fn cap_getnameinfo "const cap_channel_t *chan" "const void *name" "int namelen"
.Ft "int"
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The functions

brueffer: The functions
.Fn cap_dns_type_limit "cap_channel_t *chan" "const char * const *types" "size_t ntypes"
.Ft "int"
.Fn cap_dns_family_limit "const cap_channel_t *chan" "const int *families" "size_t nfamilies"
.Sh DESCRIPTION
The functions
.Fn cap_gethostbyname ,
.Fn cap_gethostbyname2 ,
.Fn cep_gethostbyaddr
and
.Xr cap_getnameinfo
are respectively equivalent to
.Xr gethostbyname 2 ,
.Xr gethostbyname2 2 ,
.Xr gethostbyaddr 2
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Not sure I understand this sentence correctly; is assume the system.dns connection is required for all four cap_* variants?

Maybe something like this?

and
.Xr getnameinfo 2 ,
and expect that a connection to the
.Nm system.dns
service is provided.

brueffer: Not sure I understand this sentence correctly; is assume the system.dns connection is required…
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I'm trying to say that the different between API of the get* and cap_get* are only in the one additional parameter with is connection to the system.dns.

oshogbo: I'm trying to say that the different between API of the get* and cap_get* are only in the one…
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Ah! "expect -> except" below then :-)

Also "need" -> "needs"

brueffer: Ah! "expect -> except" below then :-) Also "need" -> "needs"
and
.Xr getnameinfo 2
expect that the connection to the
.Nm system.dns
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s/value/values/

bcr: s/value/values/
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fallowing -> the following

brueffer: fallowing -> the following
services need to be provided.
.Pp
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services -> service

brueffer: services -> service
The
.Fn cap_dns_type_limit
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Probably .Va instead of .Dv since it's a variable?

brueffer: Probably .Va instead of .Dv since it's a variable?
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I'm really not sure about that.
.Va is an funtion argument
And the "type" here is an value of argument.
nvlist_add_type(nvl, "type", "ADDR");

oshogbo: I'm really not sure about that. .Va is an funtion argument And the "type" here is an value of…
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Sounds like .Va would be OK then. .Dv is more for constants and other explicit values.

brueffer: Sounds like .Va would be OK then. .Dv is more for constants and other explicit values.
function limits the functions allowed in the service.
The
.Fa types
variable can be set to
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needs a space between NAME and .

brueffer: needs a space between NAME and .
.Dv ADDR
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.Dv ADDR

brueffer: .Dv ADDR
or
.Dv NAME .
See the
.Sx LIMITS
for more deatls.
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are allowed.

brueffer: are allowed.
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"for more deatls" -> "section for more details"

brueffer: "for more deatls" -> "section for more details"
The
.Fa ntpyes
variable contains the number of
.Fa types
provided.
.Pp
The
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function is allowed

brueffer: function is allowed
.Fn cap_dns_family_limit
functions allows limit address families.
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s/on/one/

bcr: s/on/one/
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family -> families

brueffer: family -> families
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to limit

brueffer: to limit
For details see
.Sx LIMITS .
The
.Fa nfamilies
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I would remove the "the" here and rewrite it to have it read:

"The following example first opens capability to casper and then uses this capability to create a new capability to the system.dns casper service and uses the latter capability to resolve an IP address.

bcr: I would remove the "the" here and rewrite it to have it read: "The following example first…
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a capability

brueffer: a capability
variable contains the number of
.Fa family
provided.
.Sh LIMITS
The preferred way of setting limits is to use the
.Fn cap_dns_type_limit
and
.Fn cap_dns_family_limit
functions, but the limits of service can be set also using
.Xr cap_limit_set 3 .
The nvlist for that function can contain the fallowing values and types:
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I would remove "the" here, unless you add "service" after Casper.

bcr: I would remove "the" here, unless you add "service" after Casper.
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fallowing -> following

brueffer: fallowing -> following
.Bl -ohang -offset indent
.It type ( NV_TYPE_STRING )
The
.Dv type
can have two values:
.Dv ADDR
or
.Dv NAME .
The
.Dv ADDR
means that functions
.Fn cap_gethostbyname ,
.Fn cap_gethostbyname2
and
.Fn cap_gethostbyaddr
are allowed.
In case when
.Dv type
is set to
.Dv NAME
the
.Fn cap_getnameinfo
function is allowed.
.It family ( NV_TYPE_NUMBER )
The
.Dv family
limits service to one of the address families (e.g.
.Dv AF_INET , AF_INET6 ,
etc.).
.Sh EXAMPLES
The following example first opens capability to casper and then uses this
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a capability

brueffer: a capability
capability to create a capability to the
.Nm system.dns
casper service and uses the latter capability to resolve an IP address.
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Lots of capabilities in one sentence :-) I'm not sure how to make this clearer though...

brueffer: Lots of capabilities in one sentence :-) I'm not sure how to make this clearer though...
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Maybe like that?

oshogbo: Maybe like that?
.Bd -literal
cap_channel_t *capcas, *capdns;
const char *typelimit = "ADDR";
int familylimit;
const char *ipstr = "127.0.0.1";
struct in_addr ip;
struct hostent *hp;
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All four entries above need a space between "3" and ","

brueffer: All four entries above need a space between "3" and ","
/* Open capability to Casper. */
capcas = cap_init();
if (capcas == NULL)
err(1, "Unable to contact Casper");
/* Enter capability mode sandbox. */
if (cap_enter() < 0 && errno != ENOSYS)
err(1, "Unable to enter capability mode");
/* Use Casper capability to create capability to the system.dns service. */
capdns = cap_service_open(capcas, "system.dns");
if (capdns == NULL)
err(1, "Unable to open system.dns service");
/* Close Casper capability, we don't need it anymore. */
cap_close(capcas);
/* Limit system.dns to reverse DNS lookups. */
if (cap_dns_type_limit(capdns, &typelimit, 1) < 0)
err(1, "Unable to limit access to the system.dns service");
/* Limit system.dns to reserve IPv4 addresses */
familylimit = AF_INET;
if (cap_dns_family_limit(capdns, &familylimit, 1) < 0)
err(1, "Unable to limit access to the system.dns service");
/* Convert IP address in C-string to in_addr. */
if (!inet_aton(ipstr, &ip))
errx(1, "Unable to parse IP address %s.", ipstr);
/* Find hostname for the given IP address. */
hp = cap_gethostbyaddr(capdns, (const void *)&ip, sizeof(ip), AF_INET);
if (hp == NULL)
errx(1, "No name associated with %s.", ipstr);
printf("Name associated with %s is %s.\\n", ipstr, hp->h_name);
.Ed
.Sh SEE ALSO
.Xr cap_enter 2 ,
.Xr err 3 ,
.Xr gethostbyaddr 3 ,
.Xr gethostbyname 3 ,
.Xr gethostbyname2 3 ,
.Xr getnameinfo 3,
.Xr nv 3 ,
.Xr capsicum 4
.Sh AUTHORS
The cap_dns service was implemented by
.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
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.Nm cap_dns

brueffer: .Nm cap_dns
under sponsorship from the FreeBSD Foundation.
.Pp
This manual page was written by
.An Mariusz Zaborski Aq Mt oshogbo@FreeBSD.org .