grp/initgroups.c

   1 /* Copyright (C) 1989,1991,1993,1996-2006,2008,2010,2011
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <alloca.h>
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <grp.h>
  23 #include <limits.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <sys/param.h>
  28 #include <sys/types.h>
  29 #include <nsswitch.h>
  30
  31 #include "../nscd/nscd-client.h"
  32 #include "../nscd/nscd_proto.h"
  33
  34
  35 /* Type of the lookup function.  */
  36 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  37                                                     long int *, long int *,
  38                                                     gid_t **, long int, int *);
  39
  40 /* The lookup function for the first entry of this service.  */
  41 extern int __nss_group_lookup (service_user **nip, const char *name,
  42                                    void **fctp);
  43 extern void *__nss_lookup_function (service_user *ni, const char *fct_name);
  44
  45 extern service_user *__nss_group_database attribute_hidden;
  46 service_user *__nss_initgroups_database;
  47 static bool use_initgroups_entry;
  48
  49
  50 #include "compat-initgroups.c"
  51
  52
  53 static int
  54 internal_getgrouplist (const char *user, gid_t group, long int *size,
  55                        gid_t **groupsp, long int limit)
  56 {
  57 #ifdef USE_NSCD
  58   if (__nss_not_use_nscd_group > 0
  59       && ++__nss_not_use_nscd_group > NSS_NSCD_RETRY)
  60     __nss_not_use_nscd_group = 0;
  61   if (!__nss_not_use_nscd_group
  62       && !__nss_database_custom[NSS_DBSIDX_group])
  63     {
  64       int n = __nscd_getgrouplist (user, group, size, groupsp, limit);
  65       if (n >= 0)
  66         return n;
  67
  68       /* nscd is not usable.  */
  69       __nss_not_use_nscd_group = 1;
  70     }
  71 #endif
  72
  73   enum nss_status status = NSS_STATUS_UNAVAIL;
  74   int no_more = 0;
  75
  76   /* Never store more than the starting *SIZE number of elements.  */
  77   assert (*size > 0);
  78   (*groupsp)[0] = group;
  79   /* Start is one, because we have the first group as parameter.  */
  80   long int start = 1;
  81
  82   if (__nss_initgroups_database == NULL)
  83     {
  84       if (__nss_database_lookup ("initgroups", NULL, "",
  85                                  &__nss_initgroups_database) < 0)
  86         {
  87           if (__nss_group_database == NULL)
  88             no_more = __nss_database_lookup ("group", NULL, "compat files",
  89                                              &__nss_group_database);
  90
  91           __nss_initgroups_database = __nss_group_database;
  92         }
  93       else
  94         use_initgroups_entry = true;
  95     }
  96   else
  97     /* __nss_initgroups_database might have been set through
  98        __nss_configure_lookup in which case use_initgroups_entry was
  99        not set here.  */
 100     use_initgroups_entry = __nss_initgroups_database != __nss_group_database;
 101
 102   service_user *nip = __nss_initgroups_database;
 103   while (! no_more)
 104     {
 105       long int prev_start = start;
 106
 107       initgroups_dyn_function fct = __nss_lookup_function (nip,
 108                                                            "initgroups_dyn");
 109       if (fct == NULL)
 110         status = compat_call (nip, user, group, &start, size, groupsp,
 111                               limit, &errno);
 112       else
 113         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 114                                     limit, &errno));
 115
 116       /* Remove duplicates.  */
 117       long int cnt = prev_start;
 118       while (cnt < start)
 119         {
 120           long int inner;
 121           for (inner = 0; inner < prev_start; ++inner)
 122             if ((*groupsp)[inner] == (*groupsp)[cnt])
 123               break;
 124
 125           if (inner < prev_start)
 126             (*groupsp)[cnt] = (*groupsp)[--start];
 127           else
 128             ++cnt;
 129         }
 130
 131       /* This is really only for debugging.  */
 132       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 133         __libc_fatal ("illegal status in internal_getgrouplist");
 134
 135       /* For compatibility reason we will continue to look for more
 136          entries using the next service even though data has already
 137          been found if the nsswitch.conf file contained only a 'groups'
 138          line and no 'initgroups' line.  If the latter is available
 139          we always respect the status.  This means that the default
 140          for successful lookups is to return.  */
 141       if ((use_initgroups_entry || status != NSS_STATUS_SUCCESS)
 142           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 143          break;
 144
 145       if (nip->next == NULL)
 146         no_more = -1;
 147       else
 148         nip = nip->next;
 149     }
 150
 151   return start;
 152 }
 153
 154 /* Store at most *NGROUPS members of the group set for USER into
 155    *GROUPS.  Also include GROUP.  The actual number of groups found is
 156    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 157 int
 158 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 159 {
 160   long int size = MAX (1, *ngroups);
 161
 162   gid_t *newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 163   if (__builtin_expect (newgroups == NULL, 0))
 164     /* No more memory.  */
 165     // XXX This is wrong.  The user provided memory, we have to use
 166     // XXX it.  The internal functions must be called with the user
 167     // XXX provided buffer and not try to increase the size if it is
 168     // XXX too small.  For initgroups a flag could say: increase size.
 169     return -1;
 170
 171   int total = internal_getgrouplist (user, group, &size, &newgroups, -1);
 172
 173   memcpy (groups, newgroups, MIN (*ngroups, total) * sizeof (gid_t));
 174
 175   free (newgroups);
 176
 177   int retval = total > *ngroups ? -1 : total;
 178   *ngroups = total;
 179
 180   return retval;
 181 }
 182
 183 static_link_warning (getgrouplist)
 184
 185 /* Initialize the group set for the current user
 186    by reading the group database and using all groups
 187    of which USER is a member.  Also include GROUP.  */
 188 int
 189 initgroups (const char *user, gid_t group)
 190 {
 191 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 192
 193   /* No extra groups allowed.  */
 194   return 0;
 195
 196 #else
 197
 198   long int size;
 199   gid_t *groups;
 200   int ngroups;
 201   int result;
 202
 203  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 204      limit can be raised in the kernel configuration without having to
 205      recompile libc.  */
 206   long int limit = __sysconf (_SC_NGROUPS_MAX);
 207
 208   if (limit > 0)
 209     /* We limit the size of the intially allocated array.  */
 210     size = MIN (limit, 64);
 211   else
 212     /* No fixed limit on groups.  Pick a starting buffer size.  */
 213     size = 16;
 214
 215   groups = (gid_t *) malloc (size * sizeof (gid_t));
 216   if (__builtin_expect (groups == NULL, 0))
 217     /* No more memory.  */
 218     return -1;
 219
 220   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 221
 222   /* Try to set the maximum number of groups the kernel can handle.  */
 223   do
 224     result = setgroups (ngroups, groups);
 225   while (result == -1 && errno == EINVAL && --ngroups > 0);
 226
 227   free (groups);
 228
 229   return result;
 230 #endif
 231 }
 232
 233 static_link_warning (initgroups)