1/* Change the ownership and mode bits of a directory.
2
3   Copyright (C) 2006-2010 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/* Written by Paul Eggert.  */
19
20#include <config.h>
21
22#include "dirchownmod.h"
23
24#include <errno.h>
25#include <sys/types.h>
26#include <sys/stat.h>
27#include <unistd.h>
28
29#include "stat-macros.h"
30
31#ifndef HAVE_FCHMOD
32# define HAVE_FCHMOD 0
33# undef fchmod
34# define fchmod(fd, mode) (-1)
35#endif
36
37/* Change the ownership and mode bits of a directory.  If FD is
38   nonnegative, it should be a file descriptor associated with the
39   directory; close it before returning.  DIR is the name of the
40   directory.
41
42   If MKDIR_MODE is not (mode_t) -1, mkdir (DIR, MKDIR_MODE) has just
43   been executed successfully with umask zero, so DIR should be a
44   directory (not a symbolic link).
45
46   First, set the file's owner to OWNER and group to GROUP, but leave
47   the owner alone if OWNER is (uid_t) -1, and similarly for GROUP.
48
49   Then, set the file's mode bits to MODE, except preserve any of the
50   bits that correspond to zero bits in MODE_BITS.  In other words,
51   MODE_BITS is a mask that specifies which of the file's mode bits
52   should be set or cleared.  MODE should be a subset of MODE_BITS,
53   which in turn should be a subset of CHMOD_MODE_BITS.
54
55   This implementation assumes the current umask is zero.
56
57   Return 0 if successful, -1 (setting errno) otherwise.  Unsuccessful
58   calls may do the chown but not the chmod.  */
59
60int
61dirchownmod (int fd, char const *dir, mode_t mkdir_mode,
62             uid_t owner, gid_t group,
63             mode_t mode, mode_t mode_bits)
64{
65  struct stat st;
66  int result = (fd < 0 ? stat (dir, &st) : fstat (fd, &st));
67
68  if (result == 0)
69    {
70      mode_t dir_mode = st.st_mode;
71
72      /* Check whether DIR is a directory.  If FD is nonnegative, this
73         check avoids changing the ownership and mode bits of the
74         wrong file in many cases.  This doesn't fix all the race
75         conditions, but it is better than nothing.  */
76      if (! S_ISDIR (dir_mode))
77        {
78          errno = ENOTDIR;
79          result = -1;
80        }
81      else
82        {
83          /* If at least one of the S_IXUGO bits are set, chown might
84             clear the S_ISUID and S_SGID bits.  Keep track of any
85             file mode bits whose values are indeterminate due to this
86             issue.  */
87          mode_t indeterminate = 0;
88
89          /* On some systems, chown clears S_ISUID and S_ISGID, so do
90             chown before chmod.  On older System V hosts, ordinary
91             users can give their files away via chown; don't worry
92             about that here, since users shouldn't do that.  */
93
94          if ((owner != (uid_t) -1 && owner != st.st_uid)
95              || (group != (gid_t) -1 && group != st.st_gid))
96            {
97              result = (0 <= fd
98                        ? fchown (fd, owner, group)
99                        : mkdir_mode != (mode_t) -1
100                        ? lchown (dir, owner, group)
101                        : chown (dir, owner, group));
102
103              /* Either the user cares about an indeterminate bit and
104                 it'll be set properly by chmod below, or the user
105                 doesn't care and it's OK to use the bit's pre-chown
106                 value.  So there's no need to re-stat DIR here.  */
107
108              if (result == 0 && (dir_mode & S_IXUGO))
109                indeterminate = dir_mode & (S_ISUID | S_ISGID);
110            }
111
112          /* If the file mode bits might not be right, use chmod to
113             change them.  Don't change bits the user doesn't care
114             about.  */
115          if (result == 0 && (((dir_mode ^ mode) | indeterminate) & mode_bits))
116            {
117              mode_t chmod_mode =
118                mode | (dir_mode & CHMOD_MODE_BITS & ~mode_bits);
119              result = (HAVE_FCHMOD && 0 <= fd
120                        ? fchmod (fd, chmod_mode)
121                        : mkdir_mode != (mode_t) -1
122                        ? lchmod (dir, chmod_mode)
123                        : chmod (dir, chmod_mode));
124            }
125        }
126    }
127
128  if (0 <= fd)
129    {
130      if (result == 0)
131        result = close (fd);
132      else
133        {
134          int e = errno;
135          close (fd);
136          errno = e;
137        }
138    }
139
140  return result;
141}
142