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) __overloadable
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 /* Handle consequential slashes. */
136 continue;
137 }
138 else if (strcmp(next_token, ".") == 0)
139 continue;
140 else if (strcmp(next_token, "..") == 0) {
141 /*
142 * Strip the last path component except when we have
143 * single "/"
144 */
145 if (resolved_len > 1) {
146 resolved[resolved_len - 1] = '\0';
147 q = strrchr(resolved, '/') + 1;
148 *q = '\0';
149 resolved_len = q - resolved;
150 }
151 continue;
152 }
153
154 /*
155 * Append the next path component and lstat() it.
156 */
157 resolved_len = strlcat(resolved, next_token, PATH_MAX);
158 if (resolved_len >= PATH_MAX) {
159 if (m)
160 free(resolved);
161 errno = ENAMETOOLONG;
162 return (NULL);
163 }
164 if (lstat(resolved, &sb) != 0) {
165 if (m)
166 free(resolved);
167 return (NULL);
168 }
169 if (S_ISLNK(sb.st_mode)) {
170 if (symlinks++ > MAXSYMLINKS) {
171 if (m)
172 free(resolved);
173 errno = ELOOP;
174 return (NULL);
175 }
176 slen = readlink(resolved, symlink, sizeof(symlink) - 1);
177 if (slen < 0) {
178 if (m)
179 free(resolved);
180 return (NULL);
181 }
182 symlink[slen] = '\0';
183 if (symlink[0] == '/') {
184 resolved[1] = 0;
185 resolved_len = 1;
186 } else if (resolved_len > 1) {
187 /* Strip the last path component. */
188 resolved[resolved_len - 1] = '\0';
189 q = strrchr(resolved, '/') + 1;
190 *q = '\0';
191 resolved_len = q - resolved;
192 }
193
194 /*
195 * If there are any path components left, then
196 * append them to symlink. The result is placed
197 * in `left'.
198 */
199 if (p != NULL) {
200 if (symlink[slen - 1] != '/') {
201 if (slen + 1 >= sizeof(symlink)) {
202 if (m)
203 free(resolved);
204 errno = ENAMETOOLONG;
205 return (NULL);
206 }
207 symlink[slen] = '/';
208 symlink[slen + 1] = 0;
209 }
210 left_len = strlcat(symlink, left,
211 sizeof(symlink));
212 if (left_len >= sizeof(left)) {
213 if (m)
214 free(resolved);
215 errno = ENAMETOOLONG;
216 return (NULL);
217 }
218 }
219 left_len = strlcpy(left, symlink, sizeof(left));
220 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
221 if (m)
222 free(resolved);
223 errno = ENOTDIR;
224 return (NULL);
225 }
226 }
227
228 /*
229 * Remove trailing slash except when the resolved pathname
230 * is a single "/".
231 */
232 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
233 resolved[resolved_len - 1] = '\0';
234 return (resolved);
235 }
236