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b4a555d6 UD |
1 | /* Return the canonical absolute name of a given file inside chroot. |
2 | Copyright (C) 1996, 1997, 1998, 1999, 2000 Free Software Foundation, Inc. | |
3 | This file is part of the GNU C Library. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
41bdb6e2 AJ |
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. | |
b4a555d6 UD |
9 | |
10 | The GNU C 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 | |
41bdb6e2 | 13 | Lesser General Public License for more details. |
b4a555d6 | 14 | |
41bdb6e2 AJ |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, write to the Free | |
17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
18 | 02111-1307 USA. */ | |
b4a555d6 UD |
19 | |
20 | #include <stdlib.h> | |
21 | #include <string.h> | |
22 | #include <unistd.h> | |
23 | #include <limits.h> | |
24 | #include <sys/param.h> | |
25 | #include <sys/stat.h> | |
26 | #include <errno.h> | |
27 | #include <stddef.h> | |
0b87a270 AJ |
28 | #include <stdint.h> |
29 | ||
b4a555d6 UD |
30 | #include "ldconfig.h" |
31 | ||
32 | #ifndef PATH_MAX | |
33 | #define PATH_MAX 1024 | |
34 | #endif | |
35 | ||
36 | /* Return the canonical absolute name of file NAME as if chroot(CHROOT) was | |
37 | done first. A canonical name does not contain any `.', `..' components | |
38 | nor any repeated path separators ('/') or symlinks. All path components | |
39 | must exist and NAME must be absolute filename. The result is malloc'd. | |
40 | The returned name includes the CHROOT prefix. */ | |
41 | ||
42 | char * | |
43 | chroot_canon (const char *chroot, const char *name) | |
44 | { | |
45 | char *rpath, *dest, *extra_buf = NULL, *rpath_root; | |
46 | const char *start, *end, *rpath_limit; | |
47 | int num_links = 0; | |
48 | size_t chroot_len = strlen (chroot); | |
49 | ||
50 | if (chroot_len < 1) | |
51 | { | |
52 | __set_errno (EINVAL); | |
53 | return NULL; | |
54 | } | |
55 | ||
56 | rpath = malloc (chroot_len + PATH_MAX); | |
57 | rpath_limit = rpath + chroot_len + PATH_MAX; | |
58 | ||
59 | rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1; | |
60 | if (*rpath_root != '/') | |
61 | *++rpath_root = '/'; | |
62 | dest = rpath_root + 1; | |
63 | ||
64 | for (start = end = name; *start; start = end) | |
65 | { | |
66 | struct stat64 st; | |
67 | int n; | |
68 | ||
69 | /* Skip sequence of multiple path-separators. */ | |
70 | while (*start == '/') | |
71 | ++start; | |
72 | ||
73 | /* Find end of path component. */ | |
74 | for (end = start; *end && *end != '/'; ++end) | |
75 | /* Nothing. */; | |
76 | ||
77 | if (end - start == 0) | |
78 | break; | |
79 | else if (end - start == 1 && start[0] == '.') | |
80 | /* nothing */; | |
81 | else if (end - start == 2 && start[0] == '.' && start[1] == '.') | |
82 | { | |
83 | /* Back up to previous component, ignore if at root already. */ | |
84 | if (dest > rpath_root + 1) | |
85 | while ((--dest)[-1] != '/'); | |
86 | } | |
87 | else | |
88 | { | |
89 | size_t new_size; | |
90 | ||
91 | if (dest[-1] != '/') | |
92 | *dest++ = '/'; | |
93 | ||
94 | if (dest + (end - start) >= rpath_limit) | |
95 | { | |
96 | ptrdiff_t dest_offset = dest - rpath; | |
97 | ||
98 | new_size = rpath_limit - rpath; | |
99 | if (end - start + 1 > PATH_MAX) | |
100 | new_size += end - start + 1; | |
101 | else | |
102 | new_size += PATH_MAX; | |
103 | rpath = realloc (rpath, new_size); | |
104 | rpath_limit = rpath + new_size; | |
105 | if (rpath == NULL) | |
106 | return NULL; | |
107 | ||
108 | dest = rpath + dest_offset; | |
109 | } | |
110 | ||
111 | dest = mempcpy (dest, start, end - start); | |
112 | *dest = '\0'; | |
113 | ||
114 | if (lstat64 (rpath, &st) < 0) | |
115 | { | |
116 | if (*end == '\0') | |
117 | goto done; | |
118 | goto error; | |
119 | } | |
120 | ||
121 | if (S_ISLNK (st.st_mode)) | |
122 | { | |
123 | char *buf = alloca (PATH_MAX); | |
124 | size_t len; | |
125 | ||
126 | if (++num_links > MAXSYMLINKS) | |
127 | { | |
128 | __set_errno (ELOOP); | |
129 | goto error; | |
130 | } | |
131 | ||
132 | n = readlink (rpath, buf, PATH_MAX); | |
133 | if (n < 0) | |
134 | { | |
135 | if (*end == '\0') | |
136 | goto done; | |
137 | goto error; | |
138 | } | |
139 | buf[n] = '\0'; | |
140 | ||
141 | if (!extra_buf) | |
142 | extra_buf = alloca (PATH_MAX); | |
143 | ||
144 | len = strlen (end); | |
145 | if ((long int) (n + len) >= PATH_MAX) | |
146 | { | |
147 | __set_errno (ENAMETOOLONG); | |
148 | goto error; | |
149 | } | |
150 | ||
151 | /* Careful here, end may be a pointer into extra_buf... */ | |
152 | memmove (&extra_buf[n], end, len + 1); | |
153 | name = end = memcpy (extra_buf, buf, n); | |
154 | ||
155 | if (buf[0] == '/') | |
156 | dest = rpath_root + 1; /* It's an absolute symlink */ | |
157 | else | |
158 | /* Back up to previous component, ignore if at root already: */ | |
159 | if (dest > rpath_root + 1) | |
160 | while ((--dest)[-1] != '/'); | |
161 | } | |
162 | } | |
163 | } | |
164 | done: | |
165 | if (dest > rpath_root + 1 && dest[-1] == '/') | |
166 | --dest; | |
167 | *dest = '\0'; | |
168 | ||
169 | return rpath; | |
170 | ||
171 | error: | |
172 | free (rpath); | |
173 | return NULL; | |
174 | } |