nss/nss_files/files-initgroups.c

   1 /* Initgroups handling in nss_files module.
   2    Copyright (C) 2011-2015 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <alloca.h>
  20 #include <errno.h>
  21 #include <grp.h>
  22 #include <nss.h>
  23 #include <stdio_ext.h>
  24 #include <string.h>
  25 #include <sys/param.h>
  26 #include <stdbool.h>
  27 #include <stdlib.h>
  28
  29 enum nss_status
  30 _nss_files_initgroups_dyn (const char *user, gid_t group, long int *start,
  31                            long int *size, gid_t **groupsp, long int limit,
  32                            int *errnop)
  33 {
  34   FILE *stream = fopen ("/etc/group", "rce");
  35   if (stream == NULL)
  36     {
  37       *errnop = errno;
  38       return *errnop == ENOMEM ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
  39     }
  40
  41   /* No other thread using this stream.  */
  42   __fsetlocking (stream, FSETLOCKING_BYCALLER);
  43
  44   char *line = NULL;
  45   size_t linelen = 0;
  46   enum nss_status status = NSS_STATUS_SUCCESS;
  47   bool any = false;
  48
  49   size_t buflen = 1024;
  50   void *buffer = alloca (buflen);
  51   bool buffer_use_malloc = false;
  52
  53   gid_t *groups = *groupsp;
  54
  55   /* We have to iterate over the entire file.  */
  56   while (1)
  57     {
  58       fpos_t pos;
  59       fgetpos (stream, &pos);
  60       ssize_t n = getline (&line, &linelen, stream);
  61       if (n < 0)
  62         {
  63           if (! feof_unlocked (stream))
  64             status = ((*errnop = errno) == ENOMEM
  65                       ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL);
  66           break;
  67         }
  68
  69       struct group grp;
  70       int res = _nss_files_parse_grent (line, &grp, buffer, buflen, errnop);
  71       if (res == -1)
  72         {
  73           size_t newbuflen = 2 * buflen;
  74           if (buffer_use_malloc || ! __libc_use_alloca (buflen + newbuflen))
  75             {
  76               void *newbuf = realloc (buffer_use_malloc ? buffer : NULL,
  77                                       newbuflen);
  78               if (newbuf == NULL)
  79                 {
  80                   *errnop = ENOMEM;
  81                   status = NSS_STATUS_TRYAGAIN;
  82                   goto out;
  83                 }
  84               buffer = newbuf;
  85               buflen = newbuflen;
  86               buffer_use_malloc = true;
  87             }
  88           else
  89             buffer = extend_alloca (buffer, buflen, newbuflen);
  90           /* Reread current line, the parser has clobbered it.  */
  91           fsetpos (stream, &pos);
  92           continue;
  93         }
  94
  95       if (res > 0 && grp.gr_gid != group)
  96         for (char **m = grp.gr_mem; *m != NULL; ++m)
  97           if (strcmp (*m, user) == 0)
  98             {
  99               /* Matches user.  Insert this group.  */
 100               if (*start == *size)
 101                 {
 102                   /* Need a bigger buffer.  */
 103                   if (limit > 0 && *size == limit)
 104                     /* We reached the maximum.  */
 105                     goto out;
 106
 107                   long int newsize;
 108                   if (limit <= 0)
 109                     newsize = 2 * *size;
 110                   else
 111                     newsize = MIN (limit, 2 * *size);
 112
 113                   gid_t *newgroups = realloc (groups,
 114                                               newsize * sizeof (*groups));
 115                   if (newgroups == NULL)
 116                     {
 117                       *errnop = ENOMEM;
 118                       status = NSS_STATUS_TRYAGAIN;
 119                       goto out;
 120                     }
 121                   *groupsp = groups = newgroups;
 122                   *size = newsize;
 123                 }
 124
 125               groups[*start] = grp.gr_gid;
 126               *start += 1;
 127               any = true;
 128
 129               break;
 130             }
 131     }
 132
 133  out:
 134   /* Free memory.  */
 135   if (buffer_use_malloc)
 136     free (buffer);
 137   free (line);
 138
 139   fclose (stream);
 140
 141   return status == NSS_STATUS_SUCCESS && !any ? NSS_STATUS_NOTFOUND : status;
 142 }