1/* group-member.c -- determine whether group id is in calling user's group list 2 3 Copyright (C) 1994, 1997-1998, 2003, 2005-2006, 2009-2010 Free Software 4 Foundation, Inc. 5 6 This program is free software: you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19#include <config.h> 20 21#include "group-member.h" 22 23#include <stdbool.h> 24#include <stdio.h> 25#include <sys/types.h> 26#include <stdlib.h> 27 28#include <unistd.h> 29 30#include "xalloc.h" 31 32struct group_info 33 { 34 int n_groups; 35 gid_t *group; 36 }; 37 38static void 39free_group_info (struct group_info const *g) 40{ 41 free (g->group); 42} 43 44static bool 45get_group_info (struct group_info *gi) 46{ 47 int n_groups; 48 int n_group_slots = getgroups (0, NULL); 49 gid_t *group; 50 51 if (n_group_slots < 0) 52 return false; 53 54 /* Avoid xnmalloc, as it goes awry when SIZE_MAX < n_group_slots. */ 55 if (xalloc_oversized (n_group_slots, sizeof *group)) 56 xalloc_die (); 57 group = xmalloc (n_group_slots * sizeof *group); 58 n_groups = getgroups (n_group_slots, group); 59 60 /* In case of error, the user loses. */ 61 if (n_groups < 0) 62 { 63 free (group); 64 return false; 65 } 66 67 gi->n_groups = n_groups; 68 gi->group = group; 69 70 return true; 71} 72 73/* Return non-zero if GID is one that we have in our groups list. 74 Note that the groups list is not guaranteed to contain the current 75 or effective group ID, so they should generally be checked 76 separately. */ 77 78int 79group_member (gid_t gid) 80{ 81 int i; 82 int found; 83 struct group_info gi; 84 85 if (! get_group_info (&gi)) 86 return 0; 87 88 /* Search through the list looking for GID. */ 89 found = 0; 90 for (i = 0; i < gi.n_groups; i++) 91 { 92 if (gid == gi.group[i]) 93 { 94 found = 1; 95 break; 96 } 97 } 98 99 free_group_info (&gi); 100 101 return found; 102} 103 104#ifdef TEST 105 106char *program_name; 107 108int 109main (int argc, char **argv) 110{ 111 int i; 112 113 program_name = argv[0]; 114 115 for (i = 1; i < argc; i++) 116 { 117 gid_t gid; 118 119 gid = atoi (argv[i]); 120 printf ("%d: %s\n", gid, group_member (gid) ? "yes" : "no"); 121 } 122 exit (0); 123} 124 125#endif /* TEST */ 126