grp/initgroups.c

   1 /* Copyright (C) 1989, 1991-2020 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 "compat-initgroups.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   int no_more = 0;
  67
  68   /* Never store more than the starting *SIZE number of elements.  */
  69   assert (*size > 0);
  70   (*groupsp)[0] = group;
  71   /* Start is one, because we have the first group as parameter.  */
  72   long int start = 1;
  73
  74   if (__nss_initgroups_database == NULL)
  75     {
  76       if (__nss_database_lookup2 ("initgroups", NULL, "",
  77                                   &__nss_initgroups_database) < 0)
  78         {
  79           if (__nss_group_database == NULL)
  80             no_more = __nss_database_lookup2 ("group", NULL, "files",
  81                                               &__nss_group_database);
  82
  83           __nss_initgroups_database = __nss_group_database;
  84         }
  85       else
  86         use_initgroups_entry = true;
  87     }
  88   else
  89     /* __nss_initgroups_database might have been set through
  90        __nss_configure_lookup in which case use_initgroups_entry was
  91        not set here.  */
  92     use_initgroups_entry = __nss_initgroups_database != __nss_group_database;
  93
  94   service_user *nip = __nss_initgroups_database;
  95   while (! no_more)
  96     {
  97       long int prev_start = start;
  98
  99       initgroups_dyn_function fct = __nss_lookup_function (nip,
 100                                                            "initgroups_dyn");
 101       if (fct == NULL)
 102         status = compat_call (nip, user, group, &start, size, groupsp,
 103                               limit, &errno);
 104       else
 105         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 106                                     limit, &errno));
 107
 108       /* Remove duplicates.  */
 109       long int cnt = prev_start;
 110       while (cnt < start)
 111         {
 112           long int inner;
 113           for (inner = 0; inner < prev_start; ++inner)
 114             if ((*groupsp)[inner] == (*groupsp)[cnt])
 115               break;
 116
 117           if (inner < prev_start)
 118             (*groupsp)[cnt] = (*groupsp)[--start];
 119           else
 120             ++cnt;
 121         }
 122
 123       /* This is really only for debugging.  */
 124       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 125         __libc_fatal ("Illegal status in internal_getgrouplist.\n");
 126
 127       /* For compatibility reason we will continue to look for more
 128          entries using the next service even though data has already
 129          been found if the nsswitch.conf file contained only a 'groups'
 130          line and no 'initgroups' line.  If the latter is available
 131          we always respect the status.  This means that the default
 132          for successful lookups is to return.  */
 133       if ((use_initgroups_entry || status != NSS_STATUS_SUCCESS)
 134           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 135          break;
 136
 137       if (nip->next == NULL)
 138         no_more = -1;
 139       else
 140         nip = nip->next;
 141     }
 142
 143   return start;
 144 }
 145
 146 /* Store at most *NGROUPS members of the group set for USER into
 147    *GROUPS.  Also include GROUP.  The actual number of groups found is
 148    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 149 int
 150 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 151 {
 152   long int size = MAX (1, *ngroups);
 153
 154   gid_t *newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 155   if (__glibc_unlikely (newgroups == NULL))
 156     /* No more memory.  */
 157     // XXX This is wrong.  The user provided memory, we have to use
 158     // XXX it.  The internal functions must be called with the user
 159     // XXX provided buffer and not try to increase the size if it is
 160     // XXX too small.  For initgroups a flag could say: increase size.
 161     return -1;
 162
 163   int total = internal_getgrouplist (user, group, &size, &newgroups, -1);
 164
 165   memcpy (groups, newgroups, MIN (*ngroups, total) * sizeof (gid_t));
 166
 167   free (newgroups);
 168
 169   int retval = total > *ngroups ? -1 : total;
 170   *ngroups = total;
 171
 172   return retval;
 173 }
 174
 175 nss_interface_function (getgrouplist)
 176
 177 /* Initialize the group set for the current user
 178    by reading the group database and using all groups
 179    of which USER is a member.  Also include GROUP.  */
 180 int
 181 initgroups (const char *user, gid_t group)
 182 {
 183 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 184
 185   /* No extra groups allowed.  */
 186   return 0;
 187
 188 #else
 189
 190   long int size;
 191   gid_t *groups;
 192   int ngroups;
 193   int result;
 194
 195  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 196      limit can be raised in the kernel configuration without having to
 197      recompile libc.  */
 198   long int limit = __sysconf (_SC_NGROUPS_MAX);
 199
 200   if (limit > 0)
 201     /* We limit the size of the intially allocated array.  */
 202     size = MIN (limit, 64);
 203   else
 204     /* No fixed limit on groups.  Pick a starting buffer size.  */
 205     size = 16;
 206
 207   groups = (gid_t *) malloc (size * sizeof (gid_t));
 208   if (__glibc_unlikely (groups == NULL))
 209     /* No more memory.  */
 210     return -1;
 211
 212   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 213
 214   /* Try to set the maximum number of groups the kernel can handle.  */
 215   do
 216     result = setgroups (ngroups, groups);
 217   while (result == -1 && errno == EINVAL && --ngroups > 0);
 218
 219   free (groups);
 220
 221   return result;
 222 #endif
 223 }
 224
 225 nss_interface_function (initgroups)