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 * @(#)realpath.c 8.1 (Berkeley) 2/16/94
29 * $FreeBSD: head/lib/libc/stdlib/realpath.c 264417 2014-04-13 19:48:28Z jilles $
30 */
31
32 #include "namespace.h"
33 #include <sys/param.h>
34 #include <sys/stat.h>
35
36 #include <errno.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include <unistd.h>
41 #include "un-namespace.h"
42
43 int __realpath(const char *path, char *rbuf, size_t len);
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], my_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 }
76
77 if (getosreldate() >= 500710) {
78 if (__realpath(path, resolved, PATH_MAX) < 0) {
79 if (m) {
80 free(resolved);
81 } else {
82 snprintf(resolved, PATH_MAX, "%s", path);
83 }
84 return (NULL);
85 }
86 return resolved;
87 }
88
89 symlinks = 0;
90 if (path[0] == '/') {
91 resolved[0] = '/';
92 resolved[1] = '\0';
93 if (path[1] == '\0')
94 return (resolved);
95 resolved_len = 1;
96 left_len = strlcpy(left, path + 1, sizeof(left));
97 } else {
98 if (getcwd(resolved, PATH_MAX) == NULL) {
99 if (m) {
100 free(resolved);
101 } else {
102 resolved[0] = '.';
103 resolved[1] = '\0';
104 }
105 return (NULL);
106 }
107 resolved_len = strlen(resolved);
108 left_len = strlcpy(left, path, sizeof(left));
109 }
110 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
111 if (m)
112 free(resolved);
113 errno = ENAMETOOLONG;
114 return (NULL);
115 }
116
117 /*
118 * Iterate over path components in `left'.
119 */
120 while (left_len != 0) {
121 /*
122 * Extract the next path component and adjust `left'
123 * and its length.
124 */
125 p = strchr(left, '/');
126 s = p ? p : left + left_len;
127 if (s - left >= sizeof(next_token)) {
128 if (m)
129 free(resolved);
130 errno = ENAMETOOLONG;
131 return (NULL);
132 }
133 memcpy(next_token, left, s - left);
134 next_token[s - left] = '\0';
135 left_len -= s - left;
136 if (p != NULL)
137 memmove(left, s + 1, left_len + 1);
138 if (resolved[resolved_len - 1] != '/') {
139 if (resolved_len + 1 >= PATH_MAX) {
140 if (m)
141 free(resolved);
142 errno = ENAMETOOLONG;
143 return (NULL);
144 }
145 resolved[resolved_len++] = '/';
146 resolved[resolved_len] = '\0';
147 }
148 if (next_token[0] == '\0') {
149 /* Handle consequential slashes. */
150 continue;
151 } else if (strcmp(next_token, ".") == 0) {
152 continue;
153 } else if (strcmp(next_token, "..") == 0) {
154 /*
155 * Strip the last path component except when we have
156 * single "/"
157 */
158 if (resolved_len > 1) {
159 resolved[resolved_len - 1] = '\0';
160 q = strrchr(resolved, '/') + 1;
161 *q = '\0';
162 resolved_len = q - resolved;
163 }
164 continue;
165 }
166
167 /*
168 * Append the next path component and lstat() it.
169 */
170 resolved_len = strlcat(resolved, next_token, PATH_MAX);
171 if (resolved_len >= PATH_MAX) {
172 if (m)
173 free(resolved);
174 errno = ENAMETOOLONG;
175 return (NULL);
176 }
177 if (lstat(resolved, &sb) != 0) {
178 if (m)
179 free(resolved);
180 return (NULL);
181 }
182 if (S_ISLNK(sb.st_mode)) {
183 if (symlinks++ > MAXSYMLINKS) {
184 if (m)
185 free(resolved);
186 errno = ELOOP;
187 return (NULL);
188 }
189 slen = readlink(resolved, my_symlink, sizeof(my_symlink) - 1);
190 if (slen < 0) {
191 if (m)
192 free(resolved);
193 return (NULL);
194 }
195 my_symlink[slen] = '\0';
196 if (my_symlink[0] == '/') {
197 resolved[1] = 0;
198 resolved_len = 1;
199 } else if (resolved_len > 1) {
200 /* Strip the last path component. */
201 resolved[resolved_len - 1] = '\0';
202 q = strrchr(resolved, '/') + 1;
203 *q = '\0';
204 resolved_len = q - resolved;
205 }
206
207 /*
208 * If there are any path components left, then
209 * append them to symlink. The result is placed
210 * in `left'.
211 */
212 if (p != NULL) {
213 if (my_symlink[slen - 1] != '/') {
214 if (slen + 1 >= (int)sizeof(my_symlink)) {
215 if (m)
216 free(resolved);
217 errno = ENAMETOOLONG;
218 return (NULL);
219 }
220 my_symlink[slen] = '/';
221 my_symlink[slen + 1] = 0;
222 }
223 left_len = strlcat(my_symlink, left,
224 sizeof(my_symlink));
225 if (left_len >= sizeof(left)) {
226 if (m)
227 free(resolved);
228 errno = ENAMETOOLONG;
229 return (NULL);
230 }
231 }
232 left_len = strlcpy(left, my_symlink, sizeof(left));
233 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
234 if (m)
235 free(resolved);
236 errno = ENOTDIR;
237 return (NULL);
238 }
239 }
240
241 /*
242 * Remove trailing slash except when the resolved pathname
243 * is a single "/".
244 */
245 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
246 resolved[resolved_len - 1] = '\0';
247 return (resolved);
248 }
249