1 /*
2 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. The names of the authors may not be used to endorse or promote
13 * products derived from this software without specific prior written
14 * permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #if defined(LIBC_SCCS) && !defined(lint)
30 static char sccsid[] = "@(#)realpath.c 8.1 (Berkeley) 2/16/94";
31 #endif /* LIBC_SCCS and not lint */
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34
35 #include "namespace.h"
36 #include <sys/param.h>
37 #include <sys/stat.h>
38
39 #include <errno.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <unistd.h>
43 #include "un-namespace.h"
44
45 /*
46 * Find the real name of path, by removing all ".", ".." and symlink
47 * components. Returns (resolved) on success, or (NULL) on failure,
48 * in which case the path which caused trouble is left in (resolved).
49 */
50 char *
realpath(const char * __restrict path,char * __restrict resolved)51 realpath(const char * __restrict path, char * __restrict resolved)
52 {
53 struct stat sb;
54 char *p, *q, *s;
55 size_t left_len, resolved_len;
56 unsigned symlinks;
57 int m, slen;
58 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
59
60 if (path == NULL) {
61 errno = EINVAL;
62 return (NULL);
63 }
64 if (path[0] == '\0') {
65 errno = ENOENT;
66 return (NULL);
67 }
68 if (resolved == NULL) {
69 resolved = malloc(PATH_MAX);
70 if (resolved == NULL)
71 return (NULL);
72 m = 1;
73 } else
74 m = 0;
75 symlinks = 0;
76 if (path[0] == '/') {
77 resolved[0] = '/';
78 resolved[1] = '\0';
79 if (path[1] == '\0')
80 return (resolved);
81 resolved_len = 1;
82 left_len = strlcpy(left, path + 1, sizeof(left));
83 } else {
84 if (getcwd(resolved, PATH_MAX) == NULL) {
85 if (m)
86 free(resolved);
87 else {
88 resolved[0] = '.';
89 resolved[1] = '\0';
90 }
91 return (NULL);
92 }
93 resolved_len = strlen(resolved);
94 left_len = strlcpy(left, path, sizeof(left));
95 }
96 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
97 if (m)
98 free(resolved);
99 errno = ENAMETOOLONG;
100 return (NULL);
101 }
102
103 /*
104 * Iterate over path components in `left'.
105 */
106 while (left_len != 0) {
107 /*
108 * Extract the next path component and adjust `left'
109 * and its length.
110 */
111 p = strchr(left, '/');
112 s = p ? p : left + left_len;
113 if (s - left >= sizeof(next_token)) {
114 if (m)
115 free(resolved);
116 errno = ENAMETOOLONG;
117 return (NULL);
118 }
119 memcpy(next_token, left, s - left);
120 next_token[s - left] = '\0';
121 left_len -= s - left;
122 if (p != NULL)
123 memmove(left, s + 1, left_len + 1);
124 if (resolved[resolved_len - 1] != '/') {
125 if (resolved_len + 1 >= PATH_MAX) {
126 if (m)
127 free(resolved);
128 errno = ENAMETOOLONG;
129 return (NULL);
130 }
131 resolved[resolved_len++] = '/';
132 resolved[resolved_len] = '\0';
133 }
134 if (next_token[0] == '\0') {
135 /*
136 * Handle consequential slashes. The path
137 * before slash shall point to a directory.
138 *
139 * Only the trailing slashes are not covered
140 * by other checks in the loop, but we verify
141 * the prefix for any (rare) "//" or "/\0"
142 * occurence to not implement lookahead.
143 */
144 if (lstat(resolved, &sb) != 0) {
145 if (m)
146 free(resolved);
147 return (NULL);
148 }
149 if (!S_ISDIR(sb.st_mode)) {
150 if (m)
151 free(resolved);
152 errno = ENOTDIR;
153 return (NULL);
154 }
155 continue;
156 }
157 else if (strcmp(next_token, ".") == 0)
158 continue;
159 else if (strcmp(next_token, "..") == 0) {
160 /*
161 * Strip the last path component except when we have
162 * single "/"
163 */
164 if (resolved_len > 1) {
165 resolved[resolved_len - 1] = '\0';
166 q = strrchr(resolved, '/') + 1;
167 *q = '\0';
168 resolved_len = q - resolved;
169 }
170 continue;
171 }
172
173 /*
174 * Append the next path component and lstat() it.
175 */
176 resolved_len = strlcat(resolved, next_token, PATH_MAX);
177 if (resolved_len >= PATH_MAX) {
178 if (m)
179 free(resolved);
180 errno = ENAMETOOLONG;
181 return (NULL);
182 }
183 if (lstat(resolved, &sb) != 0) {
184 if (m)
185 free(resolved);
186 return (NULL);
187 }
188 if (S_ISLNK(sb.st_mode)) {
189 if (symlinks++ > MAXSYMLINKS) {
190 if (m)
191 free(resolved);
192 errno = ELOOP;
193 return (NULL);
194 }
195 slen = readlink(resolved, symlink, sizeof(symlink) - 1);
196 if (slen < 0) {
197 if (m)
198 free(resolved);
199 return (NULL);
200 }
201 symlink[slen] = '\0';
202 if (symlink[0] == '/') {
203 resolved[1] = 0;
204 resolved_len = 1;
205 } else if (resolved_len > 1) {
206 /* Strip the last path component. */
207 resolved[resolved_len - 1] = '\0';
208 q = strrchr(resolved, '/') + 1;
209 *q = '\0';
210 resolved_len = q - resolved;
211 }
212
213 /*
214 * If there are any path components left, then
215 * append them to symlink. The result is placed
216 * in `left'.
217 */
218 if (p != NULL) {
219 if (symlink[slen - 1] != '/') {
220 if (slen + 1 >= sizeof(symlink)) {
221 if (m)
222 free(resolved);
223 errno = ENAMETOOLONG;
224 return (NULL);
225 }
226 symlink[slen] = '/';
227 symlink[slen + 1] = 0;
228 }
229 left_len = strlcat(symlink, left,
230 sizeof(symlink));
231 if (left_len >= sizeof(left)) {
232 if (m)
233 free(resolved);
234 errno = ENAMETOOLONG;
235 return (NULL);
236 }
237 }
238 left_len = strlcpy(left, symlink, sizeof(left));
239 }
240 }
241
242 /*
243 * Remove trailing slash except when the resolved pathname
244 * is a single "/".
245 */
246 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
247 resolved[resolved_len - 1] = '\0';
248 return (resolved);
249 }
250