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85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
/* much like chdir(2), but safer
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Copyright (C) 2005, 2006 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* written by Jim Meyering */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "chdir-safer.h"
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#include <stdbool.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include "same-inode.h"
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#ifndef O_DIRECTORY
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# define O_DIRECTORY 0
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#endif
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#ifndef O_NOFOLLOW
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# define O_NOFOLLOW 0
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#endif
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/* Like chdir, but fail if DIR is a symbolic link to a directory (or
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similar funny business), or if DIR is not readable. This avoids a
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minor race condition between when a directory is created or statted
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and when the process chdirs into it. */
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int
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chdir_no_follow (char const *dir)
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{
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int result = 0;
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int saved_errno;
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int fd = open (dir,
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O_RDONLY | O_DIRECTORY | O_NOCTTY | O_NOFOLLOW | O_NONBLOCK);
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if (fd < 0)
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return -1;
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/* If open follows symlinks, lstat DIR and fstat FD to ensure that
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they are the same file; if they are different files, set errno to
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ELOOP (the same value that open uses for symlinks with
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O_NOFOLLOW) so the caller can report a failure. */
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if (! O_NOFOLLOW)
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{
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struct stat sb1;
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result = lstat (dir, &sb1);
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if (result == 0)
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{
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struct stat sb2;
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result = fstat (fd, &sb2);
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if (result == 0 && ! SAME_INODE (sb1, sb2))
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{
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errno = ELOOP;
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result = -1;
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}
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}
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}
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if (result == 0)
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result = fchdir (fd);
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saved_errno = errno;
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close (fd);
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errno = saved_errno;
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return result;
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}
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