1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
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 #include <sys/param.h>
32 #include <sys/stat.h>
33
34 #include <errno.h>
35 #include <fcntl.h>
36 #include <libsys.h>
37 #include <stdlib.h>
38 #include <string.h>
39 #include <unistd.h>
40 #include <ssp/ssp.h>
41
42 /*
43 * Find the real name of path, by removing all ".", ".." and symlink
44 * components. Returns (resolved) on success, or (NULL) on failure,
45 * in which case the path which caused trouble is left in (resolved).
46 */
47 static char * __noinline
realpath1(const char * path,char * resolved)48 realpath1(const char *path, char *resolved)
49 {
50 struct stat sb;
51 char *p, *q;
52 size_t left_len, prev_len, resolved_len, next_token_len;
53 unsigned symlinks;
54 ssize_t slen;
55 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
56
57 symlinks = 0;
58 if (path[0] == '/') {
59 resolved[0] = '/';
60 resolved[1] = '\0';
61 if (path[1] == '\0')
62 return (resolved);
63 resolved_len = 1;
64 left_len = strlcpy(left, path + 1, sizeof(left));
65 } else {
66 if (getcwd(resolved, PATH_MAX) == NULL) {
67 resolved[0] = '.';
68 resolved[1] = '\0';
69 return (NULL);
70 }
71 resolved_len = strlen(resolved);
72 left_len = strlcpy(left, path, sizeof(left));
73 }
74 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
75 errno = ENAMETOOLONG;
76 return (NULL);
77 }
78
79 /*
80 * Iterate over path components in `left'.
81 */
82 while (left_len != 0) {
83 /*
84 * Extract the next path component and adjust `left'
85 * and its length.
86 */
87 p = strchr(left, '/');
88
89 next_token_len = p != NULL ? (size_t)(p - left) : left_len;
90 memcpy(next_token, left, next_token_len);
91 next_token[next_token_len] = '\0';
92
93 if (p != NULL) {
94 left_len -= next_token_len + 1;
95 memmove(left, p + 1, left_len + 1);
96 } else {
97 left[0] = '\0';
98 left_len = 0;
99 }
100
101 prev_len = resolved_len;
102 if (resolved[resolved_len - 1] != '/') {
103 if (resolved_len + 1 >= PATH_MAX) {
104 errno = ENAMETOOLONG;
105 return (NULL);
106 }
107 resolved[resolved_len++] = '/';
108 resolved[resolved_len] = '\0';
109 }
110 if (next_token[0] == '\0') {
111 /* Handle consequential slashes. */
112 continue;
113 } else if (strcmp(next_token, ".") == 0) {
114 continue;
115 } else if (strcmp(next_token, "..") == 0) {
116 /*
117 * Strip the last path component except when we have
118 * single "/"
119 */
120 if (resolved_len > 1) {
121 resolved[resolved_len - 1] = '\0';
122 q = strrchr(resolved, '/') + 1;
123 *q = '\0';
124 resolved_len = q - resolved;
125 }
126 continue;
127 }
128
129 /*
130 * Append the next path component and lstat() it.
131 */
132 resolved_len = strlcat(resolved, next_token, PATH_MAX);
133 if (resolved_len >= PATH_MAX) {
134 errno = ENAMETOOLONG;
135 return (NULL);
136 }
137 if (lstat(resolved, &sb) != 0) {
138 /*
139 * EACCES means the parent directory is not
140 * readable, while ENOTDIR means the parent
141 * directory is not a directory. Rewind the path
142 * to correctly indicate where the error lies.
143 */
144 if (errno == EACCES || errno == ENOTDIR)
145 resolved[prev_len] = '\0';
146 return (NULL);
147 }
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)
155 return (NULL);
156 if (slen == 0) {
157 errno = ENOENT;
158 return (NULL);
159 }
160 if ((size_t)slen >= sizeof(symlink)) {
161 errno = ENAMETOOLONG;
162 return (NULL);
163 }
164 symlink[slen] = '\0';
165 if (symlink[0] == '/') {
166 resolved[1] = 0;
167 resolved_len = 1;
168 } else {
169 /* Strip the last path component. */
170 q = strrchr(resolved, '/') + 1;
171 *q = '\0';
172 resolved_len = q - resolved;
173 }
174
175 /*
176 * If there are any path components left, then
177 * append them to symlink. The result is placed
178 * in `left'.
179 */
180 if (p != NULL) {
181 if (symlink[slen - 1] != '/') {
182 if ((size_t)slen + 1 >= sizeof(symlink)) {
183 errno = ENAMETOOLONG;
184 return (NULL);
185 }
186 symlink[slen] = '/';
187 symlink[slen + 1] = 0;
188 }
189 left_len = strlcat(symlink, left,
190 sizeof(symlink));
191 if (left_len >= sizeof(symlink)) {
192 errno = ENAMETOOLONG;
193 return (NULL);
194 }
195 }
196 left_len = strlcpy(left, symlink, sizeof(left));
197 } else if (!S_ISDIR(sb.st_mode) && p != NULL) {
198 errno = ENOTDIR;
199 return (NULL);
200 }
201 }
202
203 /*
204 * Remove trailing slash except when the resolved pathname
205 * is a single "/".
206 */
207 if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
208 resolved[resolved_len - 1] = '\0';
209 return (resolved);
210 }
211
212 char *
realpath(const char * __restrict path,char * __restrict resolved)213 __ssp_real(realpath)(const char * __restrict path, char * __restrict resolved)
214 {
215 char *m, *res;
216
217 if (path == NULL) {
218 errno = EINVAL;
219 return (NULL);
220 }
221 if (path[0] == '\0') {
222 errno = ENOENT;
223 return (NULL);
224 }
225 if (resolved != NULL) {
226 m = NULL;
227 } else {
228 m = resolved = malloc(PATH_MAX);
229 if (resolved == NULL)
230 return (NULL);
231 }
232 if (__sys___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