nss/initgroups.c

   1 /* Copyright (C) 1989, 1991-2023 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    <https://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 /* Type of the lookup function.  */
  35 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  36                                                     long int *, long int *,
  37                                                     gid_t **, long int, int *);
  38
  39 static bool use_initgroups_entry;
  40
  41
  42 #include "initgroups-fallback.c"
  43
  44
  45 static int
  46 internal_getgrouplist (const char *user, gid_t group, long int *size,
  47                        gid_t **groupsp, long int limit)
  48 {
  49 #ifdef USE_NSCD
  50   if (__nss_not_use_nscd_group > 0
  51       && ++__nss_not_use_nscd_group > NSS_NSCD_RETRY)
  52     __nss_not_use_nscd_group = 0;
  53   if (!__nss_not_use_nscd_group
  54       && !__nss_database_custom[NSS_DBSIDX_group])
  55     {
  56       int n = __nscd_getgrouplist (user, group, size, groupsp, limit);
  57       if (n >= 0)
  58         return n;
  59
  60       /* nscd is not usable.  */
  61       __nss_not_use_nscd_group = 1;
  62     }
  63 #endif
  64
  65   enum nss_status status = NSS_STATUS_UNAVAIL;
  66
  67   /* Never store more than the starting *SIZE number of elements.  */
  68   assert (*size > 0);
  69   (*groupsp)[0] = group;
  70   /* Start is one, because we have the first group as parameter.  */
  71   long int start = 1;
  72
  73   nss_action_list nip;
  74
  75   if (__nss_database_get (nss_database_initgroups, &nip)
  76       && nip != NULL)
  77     {
  78       use_initgroups_entry = true;
  79     }
  80   else if (__nss_database_get (nss_database_group, &nip)
  81            && nip != NULL)
  82     {
  83       use_initgroups_entry = false;
  84     }
  85   else
  86     {
  87       nip = __nss_action_parse ("files");
  88       use_initgroups_entry = false;
  89     }
  90
  91   while (nip && nip->module)
  92     {
  93       long int prev_start = start;
  94
  95       initgroups_dyn_function fct = __nss_lookup_function (nip,
  96                                                            "initgroups_dyn");
  97       if (fct == NULL)
  98         status = compat_call (nip, user, group, &start, size, groupsp,
  99                               limit, &errno);
 100       else
 101         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 102                                     limit, &errno));
 103
 104       /* Remove duplicates.  */
 105       long int cnt = prev_start;
 106       while (cnt < start)
 107         {
 108           long int inner;
 109           for (inner = 0; inner < prev_start; ++inner)
 110             if ((*groupsp)[inner] == (*groupsp)[cnt])
 111               break;
 112
 113           if (inner < prev_start)
 114             (*groupsp)[cnt] = (*groupsp)[--start];
 115           else
 116             ++cnt;
 117         }
 118
 119       /* This is really only for debugging.  */
 120       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 121         __libc_fatal ("Illegal status in internal_getgrouplist.\n");
 122
 123       /* For compatibility reason we will continue to look for more
 124          entries using the next service even though data has already
 125          been found if the nsswitch.conf file contained only a 'groups'
 126          line and no 'initgroups' line.  If the latter is available
 127          we always respect the status.  This means that the default
 128          for successful lookups is to return.  */
 129       if ((use_initgroups_entry || status != NSS_STATUS_SUCCESS)
 130           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 131          break;
 132
 133       nip++;
 134     }
 135
 136   return start;
 137 }
 138
 139 /* Store at most *NGROUPS members of the group set for USER into
 140    *GROUPS.  Also include GROUP.  The actual number of groups found is
 141    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 142 int
 143 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 144 {
 145   long int size = MAX (1, *ngroups);
 146
 147   gid_t *newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 148   if (__glibc_unlikely (newgroups == NULL))
 149     /* No more memory.  */
 150     // XXX This is wrong.  The user provided memory, we have to use
 151     // XXX it.  The internal functions must be called with the user
 152     // XXX provided buffer and not try to increase the size if it is
 153     // XXX too small.  For initgroups a flag could say: increase size.
 154     return -1;
 155
 156   int total = internal_getgrouplist (user, group, &size, &newgroups, -1);
 157
 158   memcpy (groups, newgroups, MIN (*ngroups, total) * sizeof (gid_t));
 159
 160   free (newgroups);
 161
 162   int retval = total > *ngroups ? -1 : total;
 163   *ngroups = total;
 164
 165   return retval;
 166 }
 167
 168 nss_interface_function (getgrouplist)
 169
 170 /* Initialize the group set for the current user
 171    by reading the group database and using all groups
 172    of which USER is a member.  Also include GROUP.  */
 173 int
 174 initgroups (const char *user, gid_t group)
 175 {
 176 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 177
 178   /* No extra groups allowed.  */
 179   return 0;
 180
 181 #else
 182
 183   long int size;
 184   gid_t *groups;
 185   int ngroups;
 186   int result;
 187
 188  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 189      limit can be raised in the kernel configuration without having to
 190      recompile libc.  */
 191   long int limit = __sysconf (_SC_NGROUPS_MAX);
 192
 193   if (limit > 0)
 194     /* We limit the size of the initially allocated array.  */
 195     size = MIN (limit, 64);
 196   else
 197     /* No fixed limit on groups.  Pick a starting buffer size.  */
 198     size = 16;
 199
 200   groups = (gid_t *) malloc (size * sizeof (gid_t));
 201   if (__glibc_unlikely (groups == NULL))
 202     /* No more memory.  */
 203     return -1;
 204
 205   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 206
 207   /* Try to set the maximum number of groups the kernel can handle.  */
 208   do
 209     result = setgroups (ngroups, groups);
 210   while (result == -1 && errno == EINVAL && --ngroups > 0);
 211
 212   free (groups);
 213
 214   return result;
 215 #endif
 216 }
 217
 218 nss_interface_function (initgroups)