grp/initgroups.c

   1 /* Copyright (C) 1989, 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <errno.h>
  20 #include <grp.h>
  21 #include <limits.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <sys/param.h>
  26 #include <sys/types.h>
  27 #include <nsswitch.h>
  28 #include <scratch_buffer.h>
  29 #include <config.h>
  30
  31 #include "../nscd/nscd-client.h"
  32 #include "../nscd/nscd_proto.h"
  33
  34 #ifdef LINK_OBSOLETE_NSL
  35 # define DEFAULT_CONFIG "compat [NOTFOUND=return] files"
  36 #else
  37 # define DEFAULT_CONFIG "files"
  38 #endif
  39
  40 /* Type of the lookup function.  */
  41 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  42                                                     long int *, long int *,
  43                                                     gid_t **, long int, int *);
  44
  45 static bool use_initgroups_entry;
  46
  47
  48 #include "compat-initgroups.c"
  49
  50
  51 static int
  52 internal_getgrouplist (const char *user, gid_t group, long int *size,
  53                        gid_t **groupsp, long int limit)
  54 {
  55 #ifdef USE_NSCD
  56   if (__nss_not_use_nscd_group > 0
  57       && ++__nss_not_use_nscd_group > NSS_NSCD_RETRY)
  58     __nss_not_use_nscd_group = 0;
  59   if (!__nss_not_use_nscd_group
  60       && !__nss_database_custom[NSS_DBSIDX_group])
  61     {
  62       int n = __nscd_getgrouplist (user, group, size, groupsp, limit);
  63       if (n >= 0)
  64         return n;
  65
  66       /* nscd is not usable.  */
  67       __nss_not_use_nscd_group = 1;
  68     }
  69 #endif
  70
  71   enum nss_status status = NSS_STATUS_UNAVAIL;
  72   int no_more = 0;
  73
  74   /* Never store more than the starting *SIZE number of elements.  */
  75   assert (*size > 0);
  76   (*groupsp)[0] = group;
  77   /* Start is one, because we have the first group as parameter.  */
  78   long int start = 1;
  79
  80   if (__nss_initgroups_database == NULL)
  81     {
  82       if (__nss_database_lookup ("initgroups", NULL, "",
  83                                  &__nss_initgroups_database) < 0)
  84         {
  85           if (__nss_group_database == NULL)
  86             no_more = __nss_database_lookup ("group", NULL, DEFAULT_CONFIG,
  87                                              &__nss_group_database);
  88
  89           __nss_initgroups_database = __nss_group_database;
  90         }
  91       else
  92         use_initgroups_entry = true;
  93     }
  94   else
  95     /* __nss_initgroups_database might have been set through
  96        __nss_configure_lookup in which case use_initgroups_entry was
  97        not set here.  */
  98     use_initgroups_entry = __nss_initgroups_database != __nss_group_database;
  99
 100   service_user *nip = __nss_initgroups_database;
 101   while (! no_more)
 102     {
 103       long int prev_start = start;
 104
 105       initgroups_dyn_function fct = __nss_lookup_function (nip,
 106                                                            "initgroups_dyn");
 107       if (fct == NULL)
 108         status = compat_call (nip, user, group, &start, size, groupsp,
 109                               limit, &errno);
 110       else
 111         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 112                                     limit, &errno));
 113
 114       /* Remove duplicates.  */
 115       long int cnt = prev_start;
 116       while (cnt < start)
 117         {
 118           long int inner;
 119           for (inner = 0; inner < prev_start; ++inner)
 120             if ((*groupsp)[inner] == (*groupsp)[cnt])
 121               break;
 122
 123           if (inner < prev_start)
 124             (*groupsp)[cnt] = (*groupsp)[--start];
 125           else
 126             ++cnt;
 127         }
 128
 129       /* This is really only for debugging.  */
 130       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 131         __libc_fatal ("illegal status in internal_getgrouplist");
 132
 133       /* For compatibility reason we will continue to look for more
 134          entries using the next service even though data has already
 135          been found if the nsswitch.conf file contained only a 'groups'
 136          line and no 'initgroups' line.  If the latter is available
 137          we always respect the status.  This means that the default
 138          for successful lookups is to return.  */
 139       if ((use_initgroups_entry || status != NSS_STATUS_SUCCESS)
 140           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 141          break;
 142
 143       if (nip->next == NULL)
 144         no_more = -1;
 145       else
 146         nip = nip->next;
 147     }
 148
 149   return start;
 150 }
 151
 152 /* Store at most *NGROUPS members of the group set for USER into
 153    *GROUPS.  Also include GROUP.  The actual number of groups found is
 154    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 155 int
 156 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 157 {
 158   long int size = MAX (1, *ngroups);
 159
 160   gid_t *newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 161   if (__glibc_unlikely (newgroups == NULL))
 162     /* No more memory.  */
 163     // XXX This is wrong.  The user provided memory, we have to use
 164     // XXX it.  The internal functions must be called with the user
 165     // XXX provided buffer and not try to increase the size if it is
 166     // XXX too small.  For initgroups a flag could say: increase size.
 167     return -1;
 168
 169   int total = internal_getgrouplist (user, group, &size, &newgroups, -1);
 170
 171   memcpy (groups, newgroups, MIN (*ngroups, total) * sizeof (gid_t));
 172
 173   free (newgroups);
 174
 175   int retval = total > *ngroups ? -1 : total;
 176   *ngroups = total;
 177
 178   return retval;
 179 }
 180
 181 nss_interface_function (getgrouplist)
 182
 183 /* Initialize the group set for the current user
 184    by reading the group database and using all groups
 185    of which USER is a member.  Also include GROUP.  */
 186 int
 187 initgroups (const char *user, gid_t group)
 188 {
 189 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 190
 191   /* No extra groups allowed.  */
 192   return 0;
 193
 194 #else
 195
 196   long int size;
 197   gid_t *groups;
 198   int ngroups;
 199   int result;
 200
 201  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 202      limit can be raised in the kernel configuration without having to
 203      recompile libc.  */
 204   long int limit = __sysconf (_SC_NGROUPS_MAX);
 205
 206   if (limit > 0)
 207     /* We limit the size of the intially allocated array.  */
 208     size = MIN (limit, 64);
 209   else
 210     /* No fixed limit on groups.  Pick a starting buffer size.  */
 211     size = 16;
 212
 213   groups = (gid_t *) malloc (size * sizeof (gid_t));
 214   if (__glibc_unlikely (groups == NULL))
 215     /* No more memory.  */
 216     return -1;
 217
 218   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 219
 220   /* Try to set the maximum number of groups the kernel can handle.  */
 221   do
 222     result = setgroups (ngroups, groups);
 223   while (result == -1 && errno == EINVAL && --ngroups > 0);
 224
 225   free (groups);
 226
 227   return result;
 228 #endif
 229 }
 230
 231 nss_interface_function (initgroups)