1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
/* Return the canonical absolute name of a given file inside chroot.
Copyright (C) 1996-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>. */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/stat.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <eloop-threshold.h>
#include <ldconfig.h>
#ifndef PATH_MAX
#define PATH_MAX 1024
#endif
/* Return the canonical absolute name of file NAME as if chroot(CHROOT) was
done first. A canonical name does not contain any `.', `..' components
nor any repeated path separators ('/') or symlinks. All path components
must exist and NAME must be absolute filename. The result is malloc'd.
The returned name includes the CHROOT prefix. */
char *
chroot_canon (const char *chroot, const char *name)
{
char *rpath;
char *dest;
char *extra_buf = NULL;
char *rpath_root;
const char *start;
const char *end;
const char *rpath_limit;
int num_links = 0;
size_t chroot_len = strlen (chroot);
if (chroot_len < 1)
{
__set_errno (EINVAL);
return NULL;
}
rpath = xmalloc (chroot_len + PATH_MAX);
rpath_limit = rpath + chroot_len + PATH_MAX;
rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1;
if (*rpath_root != '/')
*++rpath_root = '/';
dest = rpath_root + 1;
for (start = end = name; *start; start = end)
{
struct stat64 st;
/* Skip sequence of multiple path-separators. */
while (*start == '/')
++start;
/* Find end of path component. */
for (end = start; *end && *end != '/'; ++end)
/* Nothing. */;
if (end - start == 0)
break;
else if (end - start == 1 && start[0] == '.')
/* nothing */;
else if (end - start == 2 && start[0] == '.' && start[1] == '.')
{
/* Back up to previous component, ignore if at root already. */
if (dest > rpath_root + 1)
while ((--dest)[-1] != '/');
}
else
{
size_t new_size;
if (dest[-1] != '/')
*dest++ = '/';
if (dest + (end - start) >= rpath_limit)
{
ptrdiff_t dest_offset = dest - rpath;
char *new_rpath;
new_size = rpath_limit - rpath;
if (end - start + 1 > PATH_MAX)
new_size += end - start + 1;
else
new_size += PATH_MAX;
new_rpath = (char *) xrealloc (rpath, new_size);
rpath = new_rpath;
rpath_limit = rpath + new_size;
dest = rpath + dest_offset;
}
dest = mempcpy (dest, start, end - start);
*dest = '\0';
if (lstat64 (rpath, &st) < 0)
{
if (*end == '\0')
goto done;
goto error;
}
if (S_ISLNK (st.st_mode))
{
char *buf = alloca (PATH_MAX);
size_t len;
if (++num_links > __eloop_threshold ())
{
__set_errno (ELOOP);
goto error;
}
ssize_t n = readlink (rpath, buf, PATH_MAX - 1);
if (n < 0)
{
if (*end == '\0')
goto done;
goto error;
}
buf[n] = '\0';
if (!extra_buf)
extra_buf = alloca (PATH_MAX);
len = strlen (end);
if (len >= PATH_MAX - n)
{
__set_errno (ENAMETOOLONG);
goto error;
}
/* Careful here, end may be a pointer into extra_buf... */
memmove (&extra_buf[n], end, len + 1);
name = end = memcpy (extra_buf, buf, n);
if (buf[0] == '/')
dest = rpath_root + 1; /* It's an absolute symlink */
else
/* Back up to previous component, ignore if at root already: */
if (dest > rpath_root + 1)
while ((--dest)[-1] != '/');
}
}
}
done:
if (dest > rpath_root + 1 && dest[-1] == '/')
--dest;
*dest = '\0';
return rpath;
error:
free (rpath);
return NULL;
}
|
