1/* Work around unlink bugs.
2
3   Copyright (C) 2009, 2010 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#include <config.h>
19
20#include <unistd.h>
21
22#include <errno.h>
23#include <stdlib.h>
24#include <string.h>
25#include <sys/stat.h>
26
27#undef unlink
28
29/* Remove file NAME.
30   Return 0 if successful, -1 if not.  */
31
32int
33rpl_unlink (char const *name)
34{
35  /* Work around Solaris 9 bug where unlink("file/") succeeds.  */
36  size_t len = strlen (name);
37  int result = 0;
38  if (len && ISSLASH (name[len - 1]))
39    {
40      /* We can't unlink(2) something if it doesn't exist.  If it does
41         exist, then it resolved to a directory, due to the trailing
42         slash, and POSIX requires that the unlink attempt to remove
43         that directory (which would leave the symlink dangling).
44         Unfortunately, Solaris 9 is one of the platforms where the
45         root user can unlink directories, and we don't want to
46         cripple this behavior on real directories, even if it is
47         seldom needed (at any rate, it's nicer to let coreutils'
48         unlink(1) give the correct errno for non-root users).  But we
49         don't know whether name was an actual directory, or a symlink
50         to a directory; and due to the bug of ignoring trailing
51         slash, Solaris 9 would end up successfully unlinking the
52         symlink instead of the directory.  Technically, we could use
53         realpath to find the canonical directory name to attempt
54         deletion on.  But that is a lot of work for a corner case; so
55         we instead just use an lstat on the shortened name, and
56         reject symlinks with trailing slashes.  The root user of
57         unlink(1) will just have to live with the rule that they
58         can't delete a directory via a symlink.  */
59      struct stat st;
60      result = lstat (name, &st);
61      if (result == 0)
62        {
63          /* Trailing NUL will overwrite the trailing slash.  */
64          char *short_name = malloc (len);
65          if (!short_name)
66            {
67              errno = EPERM;
68              return -1;
69            }
70          memcpy (short_name, name, len);
71          while (len && ISSLASH (short_name[len - 1]))
72            short_name[--len] = '\0';
73          if (len && (lstat (short_name, &st) || S_ISLNK (st.st_mode)))
74            {
75              free (short_name);
76              errno = EPERM;
77              return -1;
78            }
79          free (short_name);
80        }
81    }
82  if (!result)
83    result = unlink (name);
84  return result;
85}
86