grp/initgroups.c

   1 /* Copyright (C) 1989,91,93,1996-2001, 2002 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/types.h>
  27 #include <nsswitch.h>
  28
  29 /* Type of the lookup function.  */
  30 typedef enum nss_status (*initgroups_dyn_function) (const char *, gid_t,
  31                                                     long int *, long int *,
  32                                                     gid_t **, long int, int *);
  33 /* Prototype for the setgrent functions we use here.  */
  34 typedef enum nss_status (*set_function) (void);
  35
  36 /* Prototype for the endgrent functions we use here.  */
  37 typedef enum nss_status (*end_function) (void);
  38
  39 /* Prototype for the setgrent functions we use here.  */
  40 typedef enum nss_status (*get_function) (struct group *, char *,
  41                                          size_t, int *);
  42
  43 /* The lookup function for the first entry of this service.  */
  44 extern int __nss_group_lookup (service_user **nip, const char *name,
  45                                    void **fctp);
  46 extern void *__nss_lookup_function (service_user *ni, const char *fct_name);
  47
  48 extern service_user *__nss_group_database attribute_hidden;
  49
  50 static enum nss_status
  51 compat_call (service_user *nip, const char *user, gid_t group, long int *start,
  52              long int *size, gid_t **groupsp, long int limit, int *errnop)
  53 {
  54   struct group grpbuf;
  55   size_t buflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
  56   char *tmpbuf;
  57   enum nss_status status;
  58   set_function setgrent_fct;
  59   get_function getgrent_fct;
  60   end_function endgrent_fct;
  61   gid_t *groups = *groupsp;
  62
  63   getgrent_fct = __nss_lookup_function (nip, "getgrent_r");
  64   if (getgrent_fct == NULL)
  65     return NSS_STATUS_UNAVAIL;
  66
  67   setgrent_fct = __nss_lookup_function (nip, "setgrent");
  68   if (setgrent_fct)
  69     {
  70       status = DL_CALL_FCT (setgrent_fct, ());
  71       if (status != NSS_STATUS_SUCCESS)
  72         return status;
  73     }
  74
  75   endgrent_fct = __nss_lookup_function (nip, "endgrent");
  76
  77   tmpbuf = __alloca (buflen);
  78
  79   do
  80     {
  81       while ((status = DL_CALL_FCT (getgrent_fct,
  82                                      (&grpbuf, tmpbuf, buflen, errnop)),
  83               status == NSS_STATUS_TRYAGAIN)
  84              && *errnop == ERANGE)
  85         {
  86           buflen *= 2;
  87           tmpbuf = __alloca (buflen);
  88         }
  89
  90       if (status != NSS_STATUS_SUCCESS)
  91         goto done;
  92
  93       if (grpbuf.gr_gid != group)
  94         {
  95           char **m;
  96
  97           for (m = grpbuf.gr_mem; *m != NULL; ++m)
  98             if (strcmp (*m, user) == 0)
  99               {
 100                 /* Matches user.  Insert this group.  */
 101                 if (__builtin_expect (*start == *size, 0))
 102                   {
 103                     /* Need a bigger buffer.  */
 104                     gid_t *newgroups;
 105                     long int newsize;
 106
 107                     if (limit > 0 && *size == limit)
 108                       /* We reached the maximum.  */
 109                       goto done;
 110
 111                     if (limit <= 0)
 112                       newsize = 2 * *size;
 113                     else
 114                       newsize = MIN (limit, 2 * *size);
 115
 116                     newgroups = realloc (groups, newsize * sizeof (*groups));
 117                     if (newgroups == NULL)
 118                       goto done;
 119                     *groupsp = groups = newgroups;
 120                     *size = newsize;
 121                   }
 122
 123                 groups[*start] = grpbuf.gr_gid;
 124                 *start += 1;
 125
 126                 break;
 127               }
 128         }
 129     }
 130   while (status == NSS_STATUS_SUCCESS);
 131
 132  done:
 133   if (endgrent_fct)
 134     DL_CALL_FCT (endgrent_fct, ());
 135
 136   return NSS_STATUS_SUCCESS;
 137 }
 138
 139 static int
 140 internal_getgrouplist (const char *user, gid_t group, long int *size,
 141                        gid_t **groupsp, long int limit)
 142 {
 143   service_user *nip = NULL;
 144   initgroups_dyn_function fct;
 145   enum nss_status status = NSS_STATUS_UNAVAIL;
 146   int no_more;
 147   /* Start is one, because we have the first group as parameter.  */
 148   long int start = 1;
 149
 150   *groupsp[0] = group;
 151
 152   if (__nss_group_database != NULL)
 153     {
 154       no_more = 0;
 155       nip = __nss_group_database;
 156     }
 157   else
 158     no_more = __nss_database_lookup ("group", NULL,
 159                                      "compat [NOTFOUND=return] files", &nip);
 160
 161   while (! no_more)
 162     {
 163       fct = __nss_lookup_function (nip, "initgroups_dyn");
 164
 165       if (fct == NULL)
 166         {
 167           status = compat_call (nip, user, group, &start, size, groupsp,
 168                                 limit, &errno);
 169
 170           if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
 171             break;
 172         }
 173       else
 174         status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 175                                     limit, &errno));
 176
 177       /* This is really only for debugging.  */
 178       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 179         __libc_fatal ("illegal status in internal_getgrouplist");
 180
 181       if (status != NSS_STATUS_SUCCESS
 182           && nss_next_action (nip, status) == NSS_ACTION_RETURN)
 183          break;
 184
 185       if (nip->next == NULL)
 186         no_more = -1;
 187       else
 188         nip = nip->next;
 189     }
 190
 191   return start;
 192 }
 193
 194 /* Store at most *NGROUPS members of the group set for USER into
 195    *GROUPS.  Also include GROUP.  The actual number of groups found is
 196    returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
 197 int
 198 getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
 199 {
 200   gid_t *newgroups;
 201   long int size = *ngroups;
 202   int result;
 203
 204   newgroups = (gid_t *) malloc (size * sizeof (gid_t));
 205   if (__builtin_expect (newgroups == NULL, 0))
 206     /* No more memory.  */
 207     return -1;
 208
 209   result = internal_getgrouplist (user, group, &size, &newgroups, -1);
 210   if (result > *ngroups)
 211     {
 212       *ngroups = result;
 213       result = -1;
 214     }
 215   else
 216     *ngroups = result;
 217
 218   memcpy (groups, newgroups, *ngroups * sizeof (gid_t));
 219
 220   free (newgroups);
 221   return result;
 222 }
 223
 224 /* Initialize the group set for the current user
 225    by reading the group database and using all groups
 226    of which USER is a member.  Also include GROUP.  */
 227 int
 228 initgroups (const char *user, gid_t group)
 229 {
 230 #if defined NGROUPS_MAX && NGROUPS_MAX == 0
 231
 232   /* No extra groups allowed.  */
 233   return 0;
 234
 235 #else
 236
 237   long int size;
 238   gid_t *groups;
 239   int ngroups;
 240   int result;
 241
 242  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
 243      limit can be raised in the kernel configuration without having to
 244      recompile libc.  */
 245   long int limit = __sysconf (_SC_NGROUPS_MAX);
 246
 247   if (limit > 0)
 248     size = limit;
 249   else
 250     {
 251       /* No fixed limit on groups.  Pick a starting buffer size.  */
 252       size = 16;
 253     }
 254
 255   groups = (gid_t *) malloc (size * sizeof (gid_t));
 256   if (__builtin_expect (groups == NULL, 0))
 257     /* No more memory.  */
 258     return -1;
 259
 260   ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
 261
 262   /* Try to set the maximum number of groups the kernel can handle.  */
 263   do
 264     result = setgroups (ngroups, groups);
 265   while (result == -1 && errno == EINVAL && --ngroups > 0);
 266
 267   free (groups);
 268
 269   return result;
 270 #endif
 271 }