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/* group-member.c -- determine whether group id is in calling user's group list
Copyright (C) 1994, 1997, 1998, 2003, 2005 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "group-member.h"
#include <stdbool.h>
#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include "xalloc.h"
struct group_info
{
int n_groups;
GETGROUPS_T *group;
};
#if HAVE_GETGROUPS
static void
free_group_info (struct group_info const *g)
{
free (g->group);
}
static bool
get_group_info (struct group_info *gi)
{
int n_groups;
int n_group_slots = getgroups (0, NULL);
GETGROUPS_T *group;
if (n_group_slots < 0)
return false;
/* Avoid xnmalloc, as it goes awry when SIZE_MAX < n_group_slots. */
if (xalloc_oversized (n_group_slots, sizeof *group))
xalloc_die ();
group = xmalloc (n_group_slots * sizeof *group);
n_groups = getgroups (n_group_slots, group);
/* In case of error, the user loses. */
if (n_groups < 0)
{
free (group);
return false;
}
gi->n_groups = n_groups;
gi->group = group;
return true;
}
#endif /* not HAVE_GETGROUPS */
/* Return non-zero if GID is one that we have in our groups list.
If there is no getgroups function, return non-zero if GID matches
either of the current or effective group IDs. */
int
group_member (gid_t gid)
{
#ifndef HAVE_GETGROUPS
return ((gid == getgid ()) || (gid == getegid ()));
#else
int i;
int found;
struct group_info gi;
if (! get_group_info (&gi))
return 0;
/* Search through the list looking for GID. */
found = 0;
for (i = 0; i < gi.n_groups; i++)
{
if (gid == gi.group[i])
{
found = 1;
break;
}
}
free_group_info (&gi);
return found;
#endif /* HAVE_GETGROUPS */
}
#ifdef TEST
char *program_name;
int
main (int argc, char **argv)
{
int i;
program_name = argv[0];
for (i=1; i<argc; i++)
{
gid_t gid;
gid = atoi (argv[i]);
printf ("%d: %s\n", gid, group_member (gid) ? "yes" : "no");
}
exit (0);
}
#endif /* TEST */
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