nss/nss_files/files-initgroups.c

   1 /* Initgroups handling in nss_files module.
   2    Copyright (C) 2011-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <grp.h>
  21 #include <nss.h>
  22 #include <stdio_ext.h>
  23 #include <string.h>
  24 #include <sys/param.h>
  25 #include <stdbool.h>
  26 #include <stdlib.h>
  27 #include <scratch_buffer.h>
  28 #include <nss.h>
  29 #include <nss_files.h>
  30
  31 enum nss_status
  32 _nss_files_initgroups_dyn (const char *user, gid_t group, long int *start,
  33                            long int *size, gid_t **groupsp, long int limit,
  34                            int *errnop)
  35 {
  36   FILE *stream = __nss_files_fopen ("/etc/group");
  37   if (stream == NULL)
  38     {
  39       *errnop = errno;
  40       return *errnop == ENOMEM ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
  41     }
  42
  43   char *line = NULL;
  44   size_t linelen = 0;
  45   enum nss_status status = NSS_STATUS_SUCCESS;
  46   bool any = false;
  47
  48   struct scratch_buffer tmpbuf;
  49   scratch_buffer_init (&tmpbuf);
  50
  51   gid_t *groups = *groupsp;
  52
  53   /* We have to iterate over the entire file.  */
  54   while (1)
  55     {
  56       fpos_t pos;
  57       fgetpos (stream, &pos);
  58       ssize_t n = __getline (&line, &linelen, stream);
  59       if (n < 0)
  60         {
  61           if (! __feof_unlocked (stream))
  62             status = ((*errnop = errno) == ENOMEM
  63                       ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL);
  64           break;
  65         }
  66
  67       struct group grp;
  68       int res = _nss_files_parse_grent (line, &grp,
  69                                         tmpbuf.data, tmpbuf.length, errnop);
  70       if (res == -1)
  71         {
  72           if (!scratch_buffer_grow (&tmpbuf))
  73             {
  74               *errnop = ENOMEM;
  75               status = NSS_STATUS_TRYAGAIN;
  76               goto out;
  77             }
  78           /* Reread current line, the parser has clobbered it.  */
  79           fsetpos (stream, &pos);
  80           continue;
  81         }
  82
  83       if (res > 0 && grp.gr_gid != group)
  84         for (char **m = grp.gr_mem; *m != NULL; ++m)
  85           if (strcmp (*m, user) == 0)
  86             {
  87               /* Matches user.  Insert this group.  */
  88               if (*start == *size)
  89                 {
  90                   /* Need a bigger buffer.  */
  91                   if (limit > 0 && *size == limit)
  92                     /* We reached the maximum.  */
  93                     goto out;
  94
  95                   long int newsize;
  96                   if (limit <= 0)
  97                     newsize = 2 * *size;
  98                   else
  99                     newsize = MIN (limit, 2 * *size);
 100
 101                   gid_t *newgroups = realloc (groups,
 102                                               newsize * sizeof (*groups));
 103                   if (newgroups == NULL)
 104                     {
 105                       *errnop = ENOMEM;
 106                       status = NSS_STATUS_TRYAGAIN;
 107                       goto out;
 108                     }
 109                   *groupsp = groups = newgroups;
 110                   *size = newsize;
 111                 }
 112
 113               groups[*start] = grp.gr_gid;
 114               *start += 1;
 115               any = true;
 116
 117               break;
 118             }
 119     }
 120
 121  out:
 122   /* Free memory.  */
 123   scratch_buffer_free (&tmpbuf);
 124   free (line);
 125
 126   fclose (stream);
 127
 128   return status == NSS_STATUS_SUCCESS && !any ? NSS_STATUS_NOTFOUND : status;
 129 }
 130 libc_hidden_def (_nss_files_initgroups_dyn)