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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <alloca.h>
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <grp.h>
  24 #include <limits.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <sys/param.h>
  29 #include <sys/types.h>
  30 #include <nsswitch.h>
  31
  32 #include "../nscd/nscd-client.h"
  33 #include "../nscd/nscd_proto.h"
  34
  35
  36 /* Type of the lookup function.  */
  37 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  38                                                     long int *, long int *,
  39                                                     gid_t **, long int, int *);
  40
  41 /* The lookup function for the first entry of this service.  */
  42 extern int __nss_group_lookup (service_user **nip, const char *name,
  43                                    void **fctp);
  44 extern void *__nss_lookup_function (service_user *ni, const char *fct_name);
  45
  46 extern service_user *__nss_group_database attribute_hidden;
  47 service_user *__nss_initgroups_database;
  48 static bool use_initgroups_entry;
  49
  50
  51 #include "compat-initgroups.c"
  52
  53
  54 static int
  55 internal_getgrouplist (const char *user, gid_t group, long int *size,
  56                        gid_t **groupsp, long int limit)
  57 {
  58 #ifdef USE_NSCD
  59   if (__nss_not_use_nscd_group > 0
  60       && ++__nss_not_use_nscd_group > NSS_NSCD_RETRY)
  61     __nss_not_use_nscd_group = 0;
  62   if (!__nss_not_use_nscd_group
  63       && !__nss_database_custom[NSS_DBSIDX_group])
  64     {
  65       int n = __nscd_getgrouplist (user, group, size, groupsp, limit);
  66       if (n >= 0)
  67         return n;
  68
  69       /* nscd is not usable.  */
  70       __nss_not_use_nscd_group = 1;
  71     }
  72 #endif
  73
  74   enum nss_status status = NSS_STATUS_UNAVAIL;
  75   int no_more = 0;
  76
  77   /* Never store more than the starting *SIZE number of elements.  */
  78   assert (*size > 0);
  79   (*groupsp)[0] = group;
  80   /* Start is one, because we have the first group as parameter.  */
  81   long int start = 1;
  82
  83   if (__nss_initgroups_database == NULL)
  84     {
  85       if (__nss_database_lookup ("initgroups", NULL, "",
  86                                  &__nss_initgroups_database) < 0)
  87         {
  88           if (__nss_group_database == NULL)
  89             no_more = __nss_database_lookup ("group", NULL, "compat files",
  90                                              &__nss_group_database);
  91
  92           __nss_initgroups_database = __nss_group_database;
  93         }
  94       else
  95         use_initgroups_entry = true;
  96     }
  97   else
  98     /* __nss_initgroups_database might have been set through
  99        __nss_configure_lookup in which case use_initgroups_entry was
 100        not set here.  */
 101     use_initgroups_entry = __nss_initgroups_database != __nss_group_database;
 102
 103   service_user *nip = __nss_initgroups_database;
 104   while (! no_more)
 105     {
 106       long int prev_start = start;
 107
 108       initgroups_dyn_function fct = __nss_lookup_function (nip,
 109                                                            "initgroups_dyn");
 110       if (fct == NULL)
 111         status = compat_call (nip, user, group, &start, size, groupsp,
 112                               limit, &errno);
 113       else
 114         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 115                                     limit, &errno));
 116
 117       /* Remove duplicates.  */
 118       long int cnt = prev_start;
 119       while (cnt < start)
 120         {
 121           long int inner;
 122           for (inner = 0; inner < prev_start; ++inner)
 123             if ((*groupsp)[inner] == (*groupsp)[cnt])
 124               break;
 125
 126           if (inner < prev_start)
 127             (*groupsp)[cnt] = (*groupsp)[--start];
 128           else
 129             ++cnt;
 130         }
 131
 132       /* This is really only for debugging.  */
 133       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 134         __libc_fatal ("illegal status in internal_getgrouplist");
 135
 136       /* For compatibility reason we will continue to look for more
 137          entries using the next service even though data has already
 138          been found if the nsswitch.conf file contained only a 'groups'
 139          line and no 'initgroups' line.  If the latter is available
 140          we always respect the status.  This means that the default
 141          for successful lookups is to return.  */
 142       if ((use_initgroups_entry || status != NSS_STATUS_SUCCESS)
 143           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 144          break;
 145
 146       if (nip->next == NULL)
 147         no_more = -1;
 148       else
 149         nip = nip->next;
 150     }
 151
 152   return start;
 153 }
 154
 155 /* Store at most *NGROUPS members of the group set for USER into
 156    *GROUPS.  Also include GROUP.  The actual number of groups found is
 157    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 158 int
 159 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 160 {
 161   long int size = MAX (1, *ngroups);
 162
 163   gid_t *newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 164   if (__builtin_expect (newgroups == NULL, 0))
 165     /* No more memory.  */
 166     // XXX This is wrong.  The user provided memory, we have to use
 167     // XXX it.  The internal functions must be called with the user
 168     // XXX provided buffer and not try to increase the size if it is
 169     // XXX too small.  For initgroups a flag could say: increase size.
 170     return -1;
 171
 172   int total = internal_getgrouplist (user, group, &size, &newgroups, -1);
 173
 174   memcpy (groups, newgroups, MIN (*ngroups, total) * sizeof (gid_t));
 175
 176   free (newgroups);
 177
 178   int retval = total > *ngroups ? -1 : total;
 179   *ngroups = total;
 180
 181   return retval;
 182 }
 183
 184 static_link_warning (getgrouplist)
 185
 186 /* Initialize the group set for the current user
 187    by reading the group database and using all groups
 188    of which USER is a member.  Also include GROUP.  */
 189 int
 190 initgroups (const char *user, gid_t group)
 191 {
 192 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 193
 194   /* No extra groups allowed.  */
 195   return 0;
 196
 197 #else
 198
 199   long int size;
 200   gid_t *groups;
 201   int ngroups;
 202   int result;
 203
 204  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 205      limit can be raised in the kernel configuration without having to
 206      recompile libc.  */
 207   long int limit = __sysconf (_SC_NGROUPS_MAX);
 208
 209   if (limit > 0)
 210     /* We limit the size of the intially allocated array.  */
 211     size = MIN (limit, 64);
 212   else
 213     /* No fixed limit on groups.  Pick a starting buffer size.  */
 214     size = 16;
 215
 216   groups = (gid_t *) malloc (size * sizeof (gid_t));
 217   if (__builtin_expect (groups == NULL, 0))
 218     /* No more memory.  */
 219     return -1;
 220
 221   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 222
 223   /* Try to set the maximum number of groups the kernel can handle.  */
 224   do
 225     result = setgroups (ngroups, groups);
 226   while (result == -1 && errno == EINVAL && --ngroups > 0);
 227
 228   free (groups);
 229
 230   return result;
 231 #endif
 232 }
 233
 234 static_link_warning (initgroups)