116 lines
2.6 KiB
C
116 lines
2.6 KiB
C
/* group-member.c -- determine whether group id is in calling user's group list
|
|
|
|
Copyright (C) 1994, 1997-1998, 2003, 2005-2006, 2009-2020 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 3 of the License, 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, see <https://www.gnu.org/licenses/>. */
|
|
|
|
#include <config.h>
|
|
|
|
/* Specification. */
|
|
#include <unistd.h>
|
|
|
|
#include <stdio.h>
|
|
#include <sys/types.h>
|
|
#include <stdlib.h>
|
|
|
|
#include "xalloc-oversized.h"
|
|
|
|
/* Most processes have no more than this many groups, and for these
|
|
processes we can avoid using malloc. */
|
|
enum { GROUPBUF_SIZE = 100 };
|
|
|
|
struct group_info
|
|
{
|
|
gid_t *group;
|
|
gid_t groupbuf[GROUPBUF_SIZE];
|
|
};
|
|
|
|
static void
|
|
free_group_info (struct group_info const *g)
|
|
{
|
|
if (g->group != g->groupbuf)
|
|
free (g->group);
|
|
}
|
|
|
|
static int
|
|
get_group_info (struct group_info *gi)
|
|
{
|
|
int n_groups = getgroups (GROUPBUF_SIZE, gi->groupbuf);
|
|
gi->group = gi->groupbuf;
|
|
|
|
if (n_groups < 0)
|
|
{
|
|
int n_group_slots = getgroups (0, NULL);
|
|
if (0 <= n_group_slots
|
|
&& ! xalloc_oversized (n_group_slots, sizeof *gi->group))
|
|
{
|
|
gi->group = malloc (n_group_slots * sizeof *gi->group);
|
|
if (gi->group)
|
|
n_groups = getgroups (n_group_slots, gi->group);
|
|
}
|
|
}
|
|
|
|
/* In case of error, the user loses. */
|
|
return n_groups;
|
|
}
|
|
|
|
/* Return non-zero if GID is one that we have in our groups list.
|
|
Note that the groups list is not guaranteed to contain the current
|
|
or effective group ID, so they should generally be checked
|
|
separately. */
|
|
|
|
int
|
|
group_member (gid_t gid)
|
|
{
|
|
int i;
|
|
int found;
|
|
struct group_info gi;
|
|
int n_groups = get_group_info (&gi);
|
|
|
|
/* Search through the list looking for GID. */
|
|
found = 0;
|
|
for (i = 0; i < n_groups; i++)
|
|
{
|
|
if (gid == gi.group[i])
|
|
{
|
|
found = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
free_group_info (&gi);
|
|
|
|
return found;
|
|
}
|
|
|
|
#ifdef TEST
|
|
|
|
int
|
|
main (int argc, char **argv)
|
|
{
|
|
int i;
|
|
|
|
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 */
|