grp/initgroups.c

   1 /* Copyright (C) 1989,91,93,1996-2003, 2004  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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <alloca.h>
  20 #include <errno.h>
  21 #include <grp.h>
  22 #include <limits.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <sys/param.h>
  27 #include <sys/types.h>
  28 #include <nsswitch.h>
  29
  30 /* Type of the lookup function.  */
  31 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  32                                                     long int *, long int *,
  33                                                     gid_t **, long int, int *);
  34 /* Prototype for the setgrent functions we use here.  */
  35 typedef enum nss_status (*set_function) (void);
  36
  37 /* Prototype for the endgrent functions we use here.  */
  38 typedef enum nss_status (*end_function) (void);
  39
  40 /* Prototype for the setgrent functions we use here.  */
  41 typedef enum nss_status (*get_function) (struct group *, char *,
  42                                          size_t, int *);
  43
  44 /* The lookup function for the first entry of this service.  */
  45 extern int __nss_group_lookup (service_user **nip, const char *name,
  46                                    void **fctp);
  47 extern void *__nss_lookup_function (service_user *ni, const char *fct_name);
  48
  49 extern service_user *__nss_group_database attribute_hidden;
  50
  51 static enum nss_status
  52 compat_call (service_user *nip, const char *user, gid_t group, long int *start,
  53              long int *size, gid_t **groupsp, long int limit, int *errnop)
  54 {
  55   struct group grpbuf;
  56   size_t buflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
  57   char *tmpbuf;
  58   enum nss_status status;
  59   set_function setgrent_fct;
  60   get_function getgrent_fct;
  61   end_function endgrent_fct;
  62   gid_t *groups = *groupsp;
  63
  64   getgrent_fct = __nss_lookup_function (nip, "getgrent_r");
  65   if (getgrent_fct == NULL)
  66     return NSS_STATUS_UNAVAIL;
  67
  68   setgrent_fct = __nss_lookup_function (nip, "setgrent");
  69   if (setgrent_fct)
  70     {
  71       status = DL_CALL_FCT (setgrent_fct, ());
  72       if (status != NSS_STATUS_SUCCESS)
  73         return status;
  74     }
  75
  76   endgrent_fct = __nss_lookup_function (nip, "endgrent");
  77
  78   tmpbuf = __alloca (buflen);
  79
  80   do
  81     {
  82       while ((status = DL_CALL_FCT (getgrent_fct,
  83                                      (&grpbuf, tmpbuf, buflen, errnop)),
  84               status == NSS_STATUS_TRYAGAIN)
  85              && *errnop == ERANGE)
  86         {
  87           buflen *= 2;
  88           tmpbuf = __alloca (buflen);
  89         }
  90
  91       if (status != NSS_STATUS_SUCCESS)
  92         goto done;
  93
  94       if (grpbuf.gr_gid != group)
  95         {
  96           char **m;
  97
  98           for (m = grpbuf.gr_mem; *m != NULL; ++m)
  99             if (strcmp (*m, user) == 0)
 100               {
 101                 /* Matches user.  Insert this group.  */
 102                 if (__builtin_expect (*start == *size, 0))
 103                   {
 104                     /* Need a bigger buffer.  */
 105                     gid_t *newgroups;
 106                     long int newsize;
 107
 108                     if (limit > 0 && *size == limit)
 109                       /* We reached the maximum.  */
 110                       goto done;
 111
 112                     if (limit <= 0)
 113                       newsize = 2 * *size;
 114                     else
 115                       newsize = MIN (limit, 2 * *size);
 116
 117                     newgroups = realloc (groups, newsize * sizeof (*groups));
 118                     if (newgroups == NULL)
 119                       goto done;
 120                     *groupsp = groups = newgroups;
 121                     *size = newsize;
 122                   }
 123
 124                 groups[*start] = grpbuf.gr_gid;
 125                 *start += 1;
 126
 127                 break;
 128               }
 129         }
 130     }
 131   while (status == NSS_STATUS_SUCCESS);
 132
 133  done:
 134   if (endgrent_fct)
 135     DL_CALL_FCT (endgrent_fct, ());
 136
 137   return NSS_STATUS_SUCCESS;
 138 }
 139
 140 static int
 141 internal_getgrouplist (const char *user, gid_t group, long int *size,
 142                        gid_t **groupsp, long int limit)
 143 {
 144   service_user *nip = NULL;
 145   initgroups_dyn_function fct;
 146   enum nss_status status = NSS_STATUS_UNAVAIL;
 147   int no_more;
 148   /* Start is one, because we have the first group as parameter.  */
 149   long int start = 1;
 150
 151   *groupsp[0] = group;
 152
 153   if (__nss_group_database != NULL)
 154     {
 155       no_more = 0;
 156       nip = __nss_group_database;
 157     }
 158   else
 159     no_more = __nss_database_lookup ("group", NULL,
 160                                      "compat [NOTFOUND=return] files", &nip);
 161
 162   while (! no_more)
 163     {
 164       fct = __nss_lookup_function (nip, "initgroups_dyn");
 165
 166       if (fct == NULL)
 167         {
 168           status = compat_call (nip, user, group, &start, size, groupsp,
 169                                 limit, &errno);
 170
 171           if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
 172             break;
 173         }
 174       else
 175         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 176                                     limit, &errno));
 177
 178       /* This is really only for debugging.  */
 179       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 180         __libc_fatal ("illegal status in internal_getgrouplist");
 181
 182       if (status != NSS_STATUS_SUCCESS
 183           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 184          break;
 185
 186       if (nip->next == NULL)
 187         no_more = -1;
 188       else
 189         nip = nip->next;
 190     }
 191
 192   return start;
 193 }
 194
 195 /* Store at most *NGROUPS members of the group set for USER into
 196    *GROUPS.  Also include GROUP.  The actual number of groups found is
 197    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 198 int
 199 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 200 {
 201   gid_t *newgroups;
 202   long int size = *ngroups;
 203   int result;
 204
 205   newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 206   if (__builtin_expect (newgroups == NULL, 0))
 207     /* No more memory.  */
 208     return -1;
 209
 210   result = internal_getgrouplist (user, group, &size, &newgroups, -1);
 211
 212   memcpy (groups, newgroups, MIN (*ngroups, result) * sizeof (gid_t));
 213
 214   if (result > *ngroups)
 215     {
 216       *ngroups = result;
 217       result = -1;
 218     }
 219   else
 220     *ngroups = result;
 221
 222   free (newgroups);
 223   return result;
 224 }
 225
 226 static_link_warning (getgrouplist)
 227
 228 /* Initialize the group set for the current user
 229    by reading the group database and using all groups
 230    of which USER is a member.  Also include GROUP.  */
 231 int
 232 initgroups (const char *user, gid_t group)
 233 {
 234 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 235
 236   /* No extra groups allowed.  */
 237   return 0;
 238
 239 #else
 240
 241   long int size;
 242   gid_t *groups;
 243   int ngroups;
 244   int result;
 245
 246  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 247      limit can be raised in the kernel configuration without having to
 248      recompile libc.  */
 249   long int limit = __sysconf (_SC_NGROUPS_MAX);
 250
 251   if (limit > 0)
 252     /* We limit the size of the intially allocated array.  */
 253     size = MIN (limit, 64);
 254   else
 255     /* No fixed limit on groups.  Pick a starting buffer size.  */
 256     size = 16;
 257
 258   groups = (gid_t *) malloc (size * sizeof (gid_t));
 259   if (__builtin_expect (groups == NULL, 0))
 260     /* No more memory.  */
 261     return -1;
 262
 263   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 264
 265   /* Try to set the maximum number of groups the kernel can handle.  */
 266   do
 267     result = setgroups (ngroups, groups);
 268   while (result == -1 && errno == EINVAL && --ngroups > 0);
 269
 270   free (groups);
 271
 272   return result;
 273 #endif
 274 }
 275
 276 static_link_warning (initgroups)