1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 2003 Constantin S. Svintsoff <[email protected]>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. The names of the authors may not be used to endorse or promote
15 * products derived from this software without specific prior written
16 * permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #if defined(LIBC_SCCS) && !defined(lint)
32 static char sccsid[] = "@(#)realpath.c 8.1 (Berkeley) 2/16/94";
33 #endif /* LIBC_SCCS and not lint */
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36
37 #include "namespace.h"
38 #include <sys/param.h>
39 #include <sys/stat.h>
40
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include "un-namespace.h"
46
47 /*
48 * Find the real name of path, by removing all ".", ".." and symlink
49 * components. Returns (resolved) on success, or (NULL) on failure,
50 * in which case the path which caused trouble is left in (resolved).
51 */
52 static char *
realpath1(const char * path,char * resolved)53 realpath1(const char *path, char *resolved)
54 {
55 struct stat sb;
56 char *p, *q;
57 size_t left_len, resolved_len, next_token_len;
58 unsigned symlinks;
59 ssize_t slen;
60 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
61
62 symlinks = 0;
63 if (path[0] == '/') {
64 resolved[0] = '/';
65 resolved[1] = '\0';
66 if (path[1] == '\0')
67 return (resolved);
68 resolved_len = 1;
69 left_len = strlcpy(left, path + 1, sizeof(left));
70 } else {
71 if (getcwd(resolved, PATH_MAX) == NULL) {
72 resolved[0] = '.';
73 resolved[1] = '\0';
74 return (NULL);
75 }
76 resolved_len = strlen(resolved);
77 left_len = strlcpy(left, path, sizeof(left));
78 }
79 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
80 errno = ENAMETOOLONG;
81 return (NULL);
82 }
83
84 /*
85 * Iterate over path components in `left'.
86 */
87 while (left_len != 0) {
88 /*
89 * Extract the next path component and adjust `left'
90 * and its length.
91 */
92 p = strchr(left, '/');
93
94 next_token_len = p != NULL ? p - left : left_len;
95 memcpy(next_token, left, next_token_len);
96 next_token[next_token_len] = '\0';
97
98 if (p != NULL) {
99 left_len -= next_token_len + 1;
100 memmove(left, p + 1, left_len + 1);
101 } else {
102 left[0] = '\0';
103 left_len = 0;
104 }
105
106 if (resolved[resolved_len - 1] != '/') {
107 if (resolved_len + 1 >= PATH_MAX) {
108 errno = ENAMETOOLONG;
109 return (NULL);
110 }
111 resolved[resolved_len++] = '/';
112 resolved[resolved_len] = '\0';
113 }
114 if (next_token[0] == '\0') {
115 /* Handle consequential slashes. */
116 continue;
117 } else if (strcmp(next_token, ".") == 0) {
118 continue;
119 } else if (strcmp(next_token, "..") == 0) {
120 /*
121 * Strip the last path component except when we have
122 * single "/"
123 */
124 if (resolved_len > 1) {
125 resolved[resolved_len - 1] = '\0';
126 q = strrchr(resolved, '/') + 1;
127 *q = '\0';
128 resolved_len = q - resolved;
129 }
130 continue;
131 }
132
133 /*
134 * Append the next path component and lstat() it.
135 */
136 resolved_len = strlcat(resolved, next_token, PATH_MAX);
137 if (resolved_len >= PATH_MAX) {
138 errno = ENAMETOOLONG;
139 return (NULL);
140 }
141 if (lstat(resolved, &sb) != 0)
142 return (NULL);
143 if (S_ISLNK(sb.st_mode)) {
144 if (symlinks++ > MAXSYMLINKS) {
145 errno = ELOOP;
146 return (NULL);
147 }
148 slen = readlink(resolved, symlink, sizeof(symlink));
149 if (slen <= 0 || slen >= sizeof(symlink)) {
150 if (slen < 0)
151 ; /* keep errno from readlink(2) call */
152 else if (slen == 0)
153 errno = ENOENT;
154 else
155 errno = ENAMETOOLONG;
156 return (NULL);
157 }
158 symlink[slen] = '\0';
159 if (symlink[0] == '/') {
160 resolved[1] = 0;
161 resolved_len = 1;
162 } else {
163 /* Strip the last path component. */
164 q = strrchr(resolved, '/') + 1;
165 *q = '\0';
166 resolved_len = q - resolved;
167 }
168
169 /*
170 * If there are any path components left, then
171 * append them to symlink. The result is placed
172 * in `left'.
173 */
174 if (p != NULL) {
175 if (symlink[slen - 1] != '/') {
176 if (slen + 1 >= sizeof(symlink)) {
177 errno = ENAMETOOLONG;
178 return (NULL);
179 }
180 symlink[slen] = '/';
181 symlink[slen + 1] = 0;
182 }
183 left_len = strlcat(symlink, left,
184 sizeof(symlink));
185 if (left_len >= sizeof(symlink)) {
186 errno = ENAMETOOLONG;
187 return (NULL);
188 }
189 }
190 left_len = strlcpy(left, symlink, sizeof(left));
191 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
192 errno = ENOTDIR;
193 return (NULL);
194 }
195 }
196
197 /*
198 * Remove trailing slash except when the resolved pathname
199 * is a single "/".
200 */
201 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
202 resolved[resolved_len - 1] = '\0';
203 return (resolved);
204 }
205
206 char *
realpath(const char * __restrict path,char * __restrict resolved)207 realpath(const char * __restrict path, char * __restrict resolved)
208 {
209 char *m, *res;
210
211 if (path == NULL) {
212 errno = EINVAL;
213 return (NULL);
214 }
215 if (path[0] == '\0') {
216 errno = ENOENT;
217 return (NULL);
218 }
219 if (resolved != NULL) {
220 m = NULL;
221 } else {
222 m = resolved = malloc(PATH_MAX);
223 if (resolved == NULL)
224 return (NULL);
225 }
226 res = realpath1(path, resolved);
227 if (res == NULL)
228 free(m);
229 return (res);
230 }
231