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.\" Copyright (c) 2006 Ceri Davies <ceri@FreeBSD.org>
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.Dd August 18, 2023
.Dt CR_CANSEE 9
.Os
.Sh NAME
.Nm cr_cansee
.Nd "determine visibility of objects given their user credentials"
.Sh SYNOPSIS
.In sys/proc.h
.Ft int
.Fn cr_cansee "struct ucred *u1" "struct ucred *u2"
.Sh DESCRIPTION
This function determines if a subject with credential
.Fa u1
can see a subject or object associated to credential
.Fa u2 .
.Pp
Specific types of subjects may need to submit to additional or different
restrictions.
As an example, for processes, see
.Xr p_cansee 9 ,
which calls this function.
.Pp
The implementation relies on
.Xr cr_bsd_visible 9
and consequently the
.Xr sysctl 8
variables referenced in its manual page influence the result.
.Sh RETURN VALUES
This function returns zero if the subject with credential
.Fa u1
can
.Dq see
the subject or object with credential
.Fa u2 ,
or
.Er ESRCH
otherwise.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ESRCH
The subject with credential
.Fa u1
has been jailed and the subject or object with credential
.Fa u2
does not belong to the same jail or one of its sub-jails, as determined by
.Xr prison_check 9 .
.It Bq Er ESRCH
The MAC subsystem denied visibility.
.It Bq Er ESRCH
.Xr cr_bsd_visible 9
denied visibility according to the BSD security policies in force.
.El
.Sh SEE ALSO
.Xr prison_check 9 ,
.Xr mac 9 ,
.Xr cr_bsd_visible 9 ,
.Xr p_cansee 9