nscd/nscd_initgroups.c

   1 /* Copyright (C) 2004-2020 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <grp.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <not-cancel.h>
  26
  27 #include "nscd-client.h"
  28 #include "nscd_proto.h"
  29
  30
  31 /* We use the same mapping as in nscd_getgr.   */
  32 libc_locked_map_ptr (extern, __gr_map_handle) attribute_hidden;
  33
  34
  35 int
  36 __nscd_getgrouplist (const char *user, gid_t group, long int *size,
  37                      gid_t **groupsp, long int limit)
  38 {
  39   size_t userlen = strlen (user) + 1;
  40   int gc_cycle;
  41   int nretries = 0;
  42
  43   /* If the mapping is available, try to search there instead of
  44      communicating with the nscd.  */
  45   struct mapped_database *mapped;
  46   mapped = __nscd_get_map_ref (GETFDGR, "group", &__gr_map_handle, &gc_cycle);
  47
  48  retry:;
  49   char *respdata = NULL;
  50   int retval = -1;
  51   int sock = -1;
  52   initgr_response_header initgr_resp;
  53
  54   if (mapped != NO_MAPPING)
  55     {
  56       struct datahead *found = __nscd_cache_search (INITGROUPS, user,
  57                                                     userlen, mapped,
  58                                                     sizeof initgr_resp);
  59       if (found != NULL)
  60         {
  61           respdata = (char *) (&found->data[0].initgrdata + 1);
  62           initgr_resp = found->data[0].initgrdata;
  63           char *recend = (char *) found->data + found->recsize;
  64
  65           /* Now check if we can trust initgr_resp fields.  If GC is
  66              in progress, it can contain anything.  */
  67           if (mapped->head->gc_cycle != gc_cycle)
  68             {
  69               retval = -2;
  70               goto out;
  71             }
  72
  73           if (respdata + initgr_resp.ngrps * sizeof (int32_t) > recend)
  74             goto out;
  75         }
  76     }
  77
  78   /* If we do not have the cache mapped, try to get the data over the
  79      socket.  */
  80   if (respdata == NULL)
  81     {
  82       sock = __nscd_open_socket (user, userlen, INITGROUPS, &initgr_resp,
  83                                  sizeof (initgr_resp));
  84       if (sock == -1)
  85         {
  86           /* nscd not running or wrong version.  */
  87           __nss_not_use_nscd_group = 1;
  88           goto out;
  89         }
  90     }
  91
  92   if (initgr_resp.found == 1)
  93     {
  94       /* The following code assumes that gid_t and int32_t are the
  95          same size.  This is the case for al existing implementation.
  96          If this should change some code needs to be added which
  97          doesn't use memcpy but instead copies each array element one
  98          by one.  */
  99       assert (sizeof (int32_t) == sizeof (gid_t));
 100       assert (initgr_resp.ngrps >= 0);
 101
 102       /* Make sure we have enough room.  We always count GROUP in even
 103          though we might not end up adding it.  */
 104       if (*size < initgr_resp.ngrps + 1)
 105         {
 106           gid_t *newp = realloc (*groupsp,
 107                                  (initgr_resp.ngrps + 1) * sizeof (gid_t));
 108           if (newp == NULL)
 109             /* We cannot increase the buffer size.  */
 110             goto out_close;
 111
 112           *groupsp = newp;
 113           *size = initgr_resp.ngrps + 1;
 114         }
 115
 116       if (respdata == NULL)
 117         {
 118           /* Read the data from the socket.  */
 119           if ((size_t) __readall (sock, *groupsp, initgr_resp.ngrps
 120                                                   * sizeof (gid_t))
 121               == initgr_resp.ngrps * sizeof (gid_t))
 122             retval = initgr_resp.ngrps;
 123         }
 124       else
 125         {
 126           /* Just copy the data.  */
 127           retval = initgr_resp.ngrps;
 128           memcpy (*groupsp, respdata, retval * sizeof (gid_t));
 129         }
 130     }
 131   else
 132     {
 133       if (__glibc_unlikely (initgr_resp.found == -1))
 134         {
 135           /* The daemon does not cache this database.  */
 136           __nss_not_use_nscd_group = 1;
 137           goto out_close;
 138         }
 139
 140       /* No group found yet.   */
 141       retval = 0;
 142
 143       assert (*size >= 1);
 144     }
 145
 146   /* Check whether GROUP is part of the mix.  If not, add it.  */
 147   if (retval >= 0)
 148     {
 149       int cnt;
 150       for (cnt = 0; cnt < retval; ++cnt)
 151         if ((*groupsp)[cnt] == group)
 152           break;
 153
 154       if (cnt == retval)
 155         (*groupsp)[retval++] = group;
 156     }
 157
 158  out_close:
 159   if (sock != -1)
 160     __close_nocancel_nostatus (sock);
 161  out:
 162   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 163     {
 164       /* When we come here this means there has been a GC cycle while we
 165          were looking for the data.  This means the data might have been
 166          inconsistent.  Retry if possible.  */
 167       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 168         {
 169           /* nscd is just running gc now.  Disable using the mapping.  */
 170           if (atomic_decrement_val (&mapped->counter) == 0)
 171             __nscd_unmap (mapped);
 172           mapped = NO_MAPPING;
 173         }
 174
 175       if (retval != -1)
 176         goto retry;
 177     }
 178
 179   return retval;
 180 }