2 * chroot_realpath.c -- resolve pathname as if inside chroot
3 * Based on realpath.c Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
10 * This library 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 GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; see the file COPYING.LIB. If not,
17 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 * Boston, MA 02111-1307, USA.
20 * 2005/09/12: Dan Howell (modified from realpath.c to emulate chroot)
25 #define MAX_READLINKS 32
27 char *chroot_realpath(const char *root
, const char *path
,
28 char resolved_path
[]);
30 char *chroot_realpath(const char *root
, const char *path
,
33 char copy_path
[PATH_MAX
];
34 char link_path
[PATH_MAX
];
35 char got_path
[PATH_MAX
];
36 char *got_path_root
= got_path
;
37 char *new_path
= got_path
;
44 if (root
== NULL
|| *root
== '\0' ||
45 (*root
== '/' && root
[1] == '\0')) {
46 strcpy(resolved_path
, path
);
50 chroot_len
= strlen(root
);
52 if (chroot_len
+ strlen(path
) >= PATH_MAX
- 3) {
57 /* Make a copy of the source path since we may need to modify it. */
58 strcpy(copy_path
, path
);
60 max_path
= copy_path
+ PATH_MAX
- chroot_len
- 3;
62 /* Start with the chroot path. */
63 strcpy(new_path
, root
);
64 new_path
+= chroot_len
;
65 while (*new_path
== '/' && new_path
> got_path
)
67 got_path_root
= new_path
;
70 /* Expand each slash-separated pathname component. */
71 while (*path
!= '\0') {
72 /* Ignore stray "/". */
79 if (path
[1] == '\0' || path
[1] == '/') {
84 if (path
[2] == '\0' || path
[2] == '/') {
86 /* Ignore ".." at root. */
87 if (new_path
== got_path_root
+ 1)
89 /* Handle ".." by backing up. */
90 while ((--new_path
)[-1] != '/') ;
95 /* Safely copy the next pathname component. */
96 while (*path
!= '\0' && *path
!= '/') {
97 if (path
> max_path
) {
101 *new_path
++ = *path
++;
104 /* Don't follow symlink for last pathname component. */
107 /* Protect against infinite loops. */
108 if (readlinks
++ > MAX_READLINKS
) {
112 /* See if latest pathname component is a symlink. */
114 n
= readlink(got_path
, link_path
, PATH_MAX
- 1);
116 /* EINVAL means the file exists but isn't a symlink. */
117 if (errno
!= EINVAL
) {
118 /* Make sure it's null terminated. */
120 strcpy(resolved_path
, got_path
);
124 /* Note: readlink doesn't add the null byte. */
126 if (*link_path
== '/')
127 /* Start over for an absolute symlink. */
128 new_path
= got_path_root
;
130 /* Otherwise back up over this component. */
131 while (*(--new_path
) != '/') ;
132 /* Safe sex check. */
133 if (strlen(path
) + n
>= PATH_MAX
- 2) {
134 errno
= ENAMETOOLONG
;
137 /* Insert symlink contents into path. */
138 strcat(link_path
, path
);
139 strcpy(copy_path
, link_path
);
145 /* Delete trailing slash but don't whomp a lone slash. */
146 if (new_path
!= got_path
+ 1 && new_path
[-1] == '/')
148 /* Make sure it's null terminated. */
150 strcpy(resolved_path
, got_path
);
151 return resolved_path
;