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.Dd August 18, 2023
.Dt CR_BSD_VISIBLE 9
.Os
.Sh NAME
.Nm cr_bsd_visible
.Nd determine if subjects may see entities according to BSD security policies
.Sh SYNOPSIS
.In sys/proc.h
.Ft int
.Fn cr_bsd_visible "struct ucred *u1" "struct ucred *u2"
.Sh DESCRIPTION
This function determines if a subject with credentials
.Fa u1
is denied seeing an object or subject associated to credentials
.Fa u2
by the following policies and associated
.Xr sysctl 8
knobs:
.Bl -tag -width indent
.It Va security.bsd.seeotheruids
If set to 0, subjects cannot see other subjects or objects if they are not
associated with the same real user ID.
The corresponding internal function is
.Xr cr_canseeotheruids 9 .
.It Va security.bsd.seeothergids
If set to 0, subjects cannot see other subjects or objects if they are not both
a member of at least one common group.
The corresponding internal function is
.Xr cr_canseeothergids 9 .
.It Va security.bsd.see_jail_proc
If set to 0, subjects cannot see other subjects or objects that are not
associated with the same jail as they are.
The corresponding internal function is
.Xr cr_canseejailproc 9 .
.El
.Pp
As usual, the superuser (effective user ID 0) is exempt from any of these
policies provided that the
.Xr sysctl 8
variable
.Va security.bsd.suser_enabled
is non-zero and no active MAC policy explicitly denies the exemption
.Po
see
.Xr priv_check_cred 9
.Pc .
.Pp
This function is intended to be used as a helper to implement
.Xr cr_cansee 9
and similar functions.
.Sh RETURN VALUES
This function returns zero if a subject with credentials
.Fa u1
may see a subject or object with credentials
.Fa u2
by the active above-mentioned policies, or
.Er ESRCH
otherwise.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ESRCH
Credentials
.Fa u1
and
.Fa u2
do not have the same real user ID.
.It Bq Er ESRCH
Credentials
.Fa u1
and
.Fa u2
are not members of any common group
.Po
as determined by
.Xr realgroupmember 9
.Pc .
.It Bq Er ESRCH
Credentials
.Fa u1
and
.Fa u2
are not in the same jail.
.El
.Sh SEE ALSO
.Xr cr_canseeotheruids 9 ,
.Xr cr_canseeothergids 9 ,
.Xr cr_canseejailproc 9 ,
.Xr priv_check_cred 9 ,
.Xr cr_cansee 9
.Sh AUTHORS
This function and its manual page were written by
.An Olivier Certner Aq Mt olce.freebsd@certner.fr .