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+.\"
+.\" Copyright (c) 2006 Ceri Davies <ceri@FreeBSD.org>
+.\" Copyright (c) 2023 Olivier Certner <olce.freebsd@certner.fr>
+.\"
+.\" 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 DEVELOPERS ``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 DEVELOPERS 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 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 cr_bsd_visible 9 ,
+.Xr mac 9 ,
+.Xr p_cansee 9 ,
+.Xr prison_check 9