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 <fcntl.h>
46 #include "un-namespace.h"
47 #include "libc_private.h"
48
49 extern int __realpathat(int fd, const char *path, char *buf, size_t size,
50 int flags);
51
52 /*
53 * Find the real name of path, by removing all ".", ".." and symlink
54 * components. Returns (resolved) on success, or (NULL) on failure,
55 * in which case the path which caused trouble is left in (resolved).
56 */
57 static char * __noinline
realpath1(const char * path,char * resolved)58 realpath1(const char *path, char *resolved)
59 {
60 struct stat sb;
61 char *p, *q;
62 size_t left_len, resolved_len, next_token_len;
63 unsigned symlinks;
64 ssize_t slen;
65 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
66
67 symlinks = 0;
68 if (path[0] == '/') {
69 resolved[0] = '/';
70 resolved[1] = '\0';
71 if (path[1] == '\0')
72 return (resolved);
73 resolved_len = 1;
74 left_len = strlcpy(left, path + 1, sizeof(left));
75 } else {
76 if (getcwd(resolved, PATH_MAX) == NULL) {
77 resolved[0] = '.';
78 resolved[1] = '\0';
79 return (NULL);
80 }
81 resolved_len = strlen(resolved);
82 left_len = strlcpy(left, path, sizeof(left));
83 }
84 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
85 errno = ENAMETOOLONG;
86 return (NULL);
87 }
88
89 /*
90 * Iterate over path components in `left'.
91 */
92 while (left_len != 0) {
93 /*
94 * Extract the next path component and adjust `left'
95 * and its length.
96 */
97 p = strchr(left, '/');
98
99 next_token_len = p != NULL ? (size_t)(p - left) : left_len;
100 memcpy(next_token, left, next_token_len);
101 next_token[next_token_len] = '\0';
102
103 if (p != NULL) {
104 left_len -= next_token_len + 1;
105 memmove(left, p + 1, left_len + 1);
106 } else {
107 left[0] = '\0';
108 left_len = 0;
109 }
110
111 if (resolved[resolved_len - 1] != '/') {
112 if (resolved_len + 1 >= PATH_MAX) {
113 errno = ENAMETOOLONG;
114 return (NULL);
115 }
116 resolved[resolved_len++] = '/';
117 resolved[resolved_len] = '\0';
118 }
119 if (next_token[0] == '\0') {
120 /* Handle consequential slashes. */
121 continue;
122 } else if (strcmp(next_token, ".") == 0) {
123 continue;
124 } else if (strcmp(next_token, "..") == 0) {
125 /*
126 * Strip the last path component except when we have
127 * single "/"
128 */
129 if (resolved_len > 1) {
130 resolved[resolved_len - 1] = '\0';
131 q = strrchr(resolved, '/') + 1;
132 *q = '\0';
133 resolved_len = q - resolved;
134 }
135 continue;
136 }
137
138 /*
139 * Append the next path component and lstat() it.
140 */
141 resolved_len = strlcat(resolved, next_token, PATH_MAX);
142 if (resolved_len >= PATH_MAX) {
143 errno = ENAMETOOLONG;
144 return (NULL);
145 }
146 if (lstat(resolved, &sb) != 0)
147 return (NULL);
148 if (S_ISLNK(sb.st_mode)) {
149 if (symlinks++ > MAXSYMLINKS) {
150 errno = ELOOP;
151 return (NULL);
152 }
153 slen = readlink(resolved, symlink, sizeof(symlink));
154 if (slen <= 0 || slen >= (ssize_t)sizeof(symlink)) {
155 if (slen < 0)
156 ; /* keep errno from readlink(2) call */
157 else if (slen == 0)
158 errno = ENOENT;
159 else
160 errno = ENAMETOOLONG;
161 return (NULL);
162 }
163 symlink[slen] = '\0';
164 if (symlink[0] == '/') {
165 resolved[1] = 0;
166 resolved_len = 1;
167 } else {
168 /* Strip the last path component. */
169 q = strrchr(resolved, '/') + 1;
170 *q = '\0';
171 resolved_len = q - resolved;
172 }
173
174 /*
175 * If there are any path components left, then
176 * append them to symlink. The result is placed
177 * in `left'.
178 */
179 if (p != NULL) {
180 if (symlink[slen - 1] != '/') {
181 if (slen + 1 >= (ssize_t)sizeof(symlink)) {
182 errno = ENAMETOOLONG;
183 return (NULL);
184 }
185 symlink[slen] = '/';
186 symlink[slen + 1] = 0;
187 }
188 left_len = strlcat(symlink, left,
189 sizeof(symlink));
190 if (left_len >= sizeof(symlink)) {
191 errno = ENAMETOOLONG;
192 return (NULL);
193 }
194 }
195 left_len = strlcpy(left, symlink, sizeof(left));
196 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
197 errno = ENOTDIR;
198 return (NULL);
199 }
200 }
201
202 /*
203 * Remove trailing slash except when the resolved pathname
204 * is a single "/".
205 */
206 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
207 resolved[resolved_len - 1] = '\0';
208 return (resolved);
209 }
210
211 char *
realpath(const char * __restrict path,char * __restrict resolved)212 realpath(const char * __restrict path, char * __restrict resolved)
213 {
214 char *m, *res;
215
216 if (path == NULL) {
217 errno = EINVAL;
218 return (NULL);
219 }
220 if (path[0] == '\0') {
221 errno = ENOENT;
222 return (NULL);
223 }
224 if (resolved != NULL) {
225 m = NULL;
226 } else {
227 m = resolved = malloc(PATH_MAX);
228 if (resolved == NULL)
229 return (NULL);
230 }
231 if (__getosreldate() >= 1300080) {
232 if (__realpathat(AT_FDCWD, path, resolved, PATH_MAX, 0) == 0)
233 return (resolved);
234 }
235 res = realpath1(path, resolved);
236 if (res == NULL)
237 free(m);
238 return (res);
239 }
240