1 /* $OpenBSD: realpath.c,v 1.20 2015/10/13 20:55:37 millert Exp $ */
2 /*
3 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The names of the authors may not be used to endorse or promote
14 * products derived from this software without specific prior written
15 * permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /* OPENBSD ORIGINAL: lib/libc/stdlib/realpath.c */
31
32 #include "includes.h"
33
34 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
35
36 #include <sys/types.h>
37 #include <sys/param.h>
38 #include <sys/stat.h>
39
40 #include <errno.h>
41 #include <stdlib.h>
42 #include <stddef.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include <limits.h>
46
47 #ifndef SYMLOOP_MAX
48 # define SYMLOOP_MAX 32
49 #endif
50
51 /* A slightly modified copy of this file exists in libexec/ld.so */
52
53 /*
54 * char *realpath(const char *path, char resolved[PATH_MAX]);
55 *
56 * Find the real name of path, by removing all ".", ".." and symlink
57 * components. Returns (resolved) on success, or (NULL) on failure,
58 * in which case the path which caused trouble is left in (resolved).
59 */
60 char *
realpath(const char * path,char * resolved)61 realpath(const char *path, char *resolved)
62 {
63 struct stat sb;
64 char *p, *q, *s;
65 size_t left_len, resolved_len;
66 unsigned symlinks;
67 int serrno, slen, mem_allocated;
68 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
69
70 if (path[0] == '\0') {
71 errno = ENOENT;
72 return (NULL);
73 }
74
75 serrno = errno;
76
77 if (resolved == NULL) {
78 resolved = malloc(PATH_MAX);
79 if (resolved == NULL)
80 return (NULL);
81 mem_allocated = 1;
82 } else
83 mem_allocated = 0;
84
85 symlinks = 0;
86 if (path[0] == '/') {
87 resolved[0] = '/';
88 resolved[1] = '\0';
89 if (path[1] == '\0')
90 return (resolved);
91 resolved_len = 1;
92 left_len = strlcpy(left, path + 1, sizeof(left));
93 } else {
94 if (getcwd(resolved, PATH_MAX) == NULL) {
95 if (mem_allocated)
96 free(resolved);
97 else
98 strlcpy(resolved, ".", PATH_MAX);
99 return (NULL);
100 }
101 resolved_len = strlen(resolved);
102 left_len = strlcpy(left, path, sizeof(left));
103 }
104 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
105 errno = ENAMETOOLONG;
106 goto err;
107 }
108
109 /*
110 * Iterate over path components in `left'.
111 */
112 while (left_len != 0) {
113 /*
114 * Extract the next path component and adjust `left'
115 * and its length.
116 */
117 p = strchr(left, '/');
118 s = p ? p : left + left_len;
119 if (s - left >= (ptrdiff_t)sizeof(next_token)) {
120 errno = ENAMETOOLONG;
121 goto err;
122 }
123 memcpy(next_token, left, s - left);
124 next_token[s - left] = '\0';
125 left_len -= s - left;
126 if (p != NULL)
127 memmove(left, s + 1, left_len + 1);
128 if (resolved[resolved_len - 1] != '/') {
129 if (resolved_len + 1 >= PATH_MAX) {
130 errno = ENAMETOOLONG;
131 goto err;
132 }
133 resolved[resolved_len++] = '/';
134 resolved[resolved_len] = '\0';
135 }
136 if (next_token[0] == '\0')
137 continue;
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. If
156 * lstat() fails we still can return successfully if
157 * there are no more path components left.
158 */
159 resolved_len = strlcat(resolved, next_token, PATH_MAX);
160 if (resolved_len >= PATH_MAX) {
161 errno = ENAMETOOLONG;
162 goto err;
163 }
164 if (lstat(resolved, &sb) != 0) {
165 if (errno == ENOENT && p == NULL) {
166 errno = serrno;
167 return (resolved);
168 }
169 goto err;
170 }
171 if (S_ISLNK(sb.st_mode)) {
172 if (symlinks++ > SYMLOOP_MAX) {
173 errno = ELOOP;
174 goto err;
175 }
176 slen = readlink(resolved, symlink, sizeof(symlink) - 1);
177 if (slen < 0)
178 goto err;
179 symlink[slen] = '\0';
180 if (symlink[0] == '/') {
181 resolved[1] = 0;
182 resolved_len = 1;
183 } else if (resolved_len > 1) {
184 /* Strip the last path component. */
185 resolved[resolved_len - 1] = '\0';
186 q = strrchr(resolved, '/') + 1;
187 *q = '\0';
188 resolved_len = q - resolved;
189 }
190
191 /*
192 * If there are any path components left, then
193 * append them to symlink. The result is placed
194 * in `left'.
195 */
196 if (p != NULL) {
197 if (symlink[slen - 1] != '/') {
198 if (slen + 1 >=
199 (ptrdiff_t)sizeof(symlink)) {
200 errno = ENAMETOOLONG;
201 goto err;
202 }
203 symlink[slen] = '/';
204 symlink[slen + 1] = 0;
205 }
206 left_len = strlcat(symlink, left, sizeof(symlink));
207 if (left_len >= sizeof(symlink)) {
208 errno = ENAMETOOLONG;
209 goto err;
210 }
211 }
212 left_len = strlcpy(left, symlink, sizeof(left));
213 }
214 }
215
216 /*
217 * Remove trailing slash except when the resolved pathname
218 * is a single "/".
219 */
220 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
221 resolved[resolved_len - 1] = '\0';
222 return (resolved);
223
224 err:
225 if (mem_allocated)
226 free(resolved);
227 return (NULL);
228 }
229 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */
230