lib/fopen-safer.c

   1 /* Invoke fopen, but avoid some glitches.
   2
   3    Copyright (C) 2001, 2004-2006, 2009-2020 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 #include <config.h>
  21
  22 #include "stdio-safer.h"
  23
  24 #include <errno.h>
  25 #include <unistd.h>
  26 #include "unistd-safer.h"
  27
  28 /* Like fopen, but do not return stdin, stdout, or stderr.  */
  29
  30 FILE *
  31 fopen_safer (char const *file, char const *mode)
  32 {
  33   FILE *fp = fopen (file, mode);
  34
  35   if (fp)
  36     {
  37       int fd = fileno (fp);
  38
  39       if (0 <= fd && fd <= STDERR_FILENO)
  40         {
  41           int f = dup_safer (fd);
  42
  43           if (f < 0)
  44             {
  45               int e = errno;
  46               fclose (fp);
  47               errno = e;
  48               return NULL;
  49             }
  50
  51           if (fclose (fp) != 0
  52               || ! (fp = fdopen (f, mode)))
  53             {
  54               int e = errno;
  55               close (f);
  56               errno = e;
  57               return NULL;
  58             }
  59         }
  60     }
  61
  62   return fp;
  63 }