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.\" Copyright (c) 2023 Olivier Certner <olce.freebsd@certner.fr>
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.Dd August 18, 2023
.Dt CR_CANSEEOTHERGIDS 9
.Os
.Sh NAME
.Nm cr_canseeothergids
.Nd determine if subjects may see entities in a disjoint group set
.Sh SYNOPSIS
.Ft int
.Fn cr_canseeothergids "struct ucred *u1" "struct ucred *u2"
.Sh DESCRIPTION
.Bf -emphasis
This function is internal.
Its functionality is integrated into the function
.Xr cr_bsd_visible 9 ,
which should be called instead.
.Ef
.Pp
This function checks if a subject associated to credentials
.Fa u1
is denied seeing a subject or object associated to credentials
.Fa u2
by a policy that requires both credentials to have at least one group in common.
For this determination, the real and supplementary group IDs are used, but
not the effective group IDs, as per
.Xr realgroupmember 9 .
.Pp
This policy is active if and only if the
.Xr sysctl 8
variable
.Va security.bsd.see_other_gids
is set to zero.
.Pp
As usual, the superuser (effective user ID 0) is exempt from this policy
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 .
.Sh RETURN VALUES
The
.Fn cr_canseeothergids
function returns 0 if the policy is disabled, the credentials share at least one
common group, or if
.Fa u1
has privilege exempting it from the policy.
Otherwise, it returns
.Er ESRCH .
.Sh SEE ALSO
.Xr cr_bsd_visible 9 ,
.Xr priv_check_cred 9 ,
.Xr realgroupmember 9