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