1 /* Invoke opendir, but avoid some glitches.
2
3 Copyright (C) 2009-2016 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 <http://www.gnu.org/licenses/>. */
17
18 /* Written by Eric Blake. */
19
20 #include <config.h>
21
22 #include "dirent-safer.h"
23
24 #include <errno.h>
25 #include <unistd.h>
26 #include "unistd-safer.h"
27
28 /* Like opendir, but do not clobber stdin, stdout, or stderr. */
29
30 DIR *
opendir_safer(char const * name)31 opendir_safer (char const *name)
32 {
33 DIR *dp = opendir (name);
34
35 if (dp)
36 {
37 int fd = dirfd (dp);
38
39 if (0 <= fd && fd <= STDERR_FILENO)
40 {
41 /* If fdopendir is native (as on Linux), then it is safe to
42 assume dirfd(fdopendir(n))==n. If we are using the
43 gnulib module fdopendir, then this guarantee is not met,
44 but fdopendir recursively calls opendir_safer up to 3
45 times to at least get a safe fd. If fdopendir is not
46 present but dirfd is accurate (as on cygwin 1.5.x), then
47 we recurse up to 3 times ourselves. Finally, if dirfd
48 always fails (as on mingw), then we are already safe. */
49 DIR *newdp;
50 int e;
51 #if HAVE_FDOPENDIR || GNULIB_FDOPENDIR
52 int f = dup_safer (fd);
53 if (f < 0)
54 {
55 e = errno;
56 newdp = NULL;
57 }
58 else
59 {
60 newdp = fdopendir (f);
61 e = errno;
62 if (! newdp)
63 close (f);
64 }
65 #else /* !FDOPENDIR */
66 newdp = opendir_safer (name);
67 e = errno;
68 #endif
69 closedir (dp);
70 errno = e;
71 dp = newdp;
72 }
73 }
74
75 return dp;
76 }
77