| 1 | /* Invoke opendir, but avoid some glitches.
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| 2 |
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| 3 | Copyright (C) 2009-2012 Free Software Foundation, Inc.
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| 4 |
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| 5 | This program is free software: you can redistribute it and/or modify
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| 6 | it under the terms of the GNU General Public License as published by
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| 7 | the Free Software Foundation; either version 3 of the License, or
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| 8 | (at your option) any later version.
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| 9 |
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| 10 | This program is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU General Public License
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| 16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */
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| 17 |
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| 18 | /* Written by Eric Blake. */
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| 19 |
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| 20 | #include <config.h>
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| 21 |
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| 22 | #include "dirent-safer.h"
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| 23 |
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| 24 | #include <errno.h>
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| 25 | #include <unistd.h>
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| 26 | #include "unistd-safer.h"
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| 27 |
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| 28 | /* Like opendir, but do not clobber stdin, stdout, or stderr. */
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| 29 |
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| 30 | DIR *
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| 31 | opendir_safer (char const *name)
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| 32 | {
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| 33 | DIR *dp = opendir (name);
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| 34 |
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| 35 | if (dp)
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| 36 | {
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| 37 | int fd = dirfd (dp);
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| 38 |
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| 39 | if (0 <= fd && fd <= STDERR_FILENO)
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| 40 | {
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| 41 | /* If fdopendir is native (as on Linux), then it is safe to
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| 42 | assume dirfd(fdopendir(n))==n. If we are using the
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| 43 | gnulib module fdopendir, then this guarantee is not met,
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| 44 | but fdopendir recursively calls opendir_safer up to 3
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| 45 | times to at least get a safe fd. If fdopendir is not
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| 46 | present but dirfd is accurate (as on cygwin 1.5.x), then
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| 47 | we recurse up to 3 times ourselves. Finally, if dirfd
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| 48 | always fails (as on mingw), then we are already safe. */
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| 49 | DIR *newdp;
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| 50 | int e;
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| 51 | #if HAVE_FDOPENDIR || GNULIB_FDOPENDIR
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| 52 | int f = dup_safer (fd);
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| 53 | if (f < 0)
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| 54 | {
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| 55 | e = errno;
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| 56 | newdp = NULL;
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| 57 | }
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| 58 | else
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| 59 | {
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| 60 | newdp = fdopendir (f);
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| 61 | e = errno;
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| 62 | if (! newdp)
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| 63 | close (f);
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| 64 | }
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| 65 | #else /* !FDOPENDIR */
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| 66 | newdp = opendir_safer (name);
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| 67 | e = errno;
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| 68 | #endif
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| 69 | closedir (dp);
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| 70 | errno = e;
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| 71 | dp = newdp;
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| 72 | }
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| 73 | }
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| 74 |
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| 75 | return dp;
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| 76 | }
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