1 /* $Id: realpath.c,v 1.3 2013/01/25 17:06:09 sjg Exp $ */
2 /* from: $NetBSD: getcwd.c,v 1.53 2012/06/21 23:29:23 enami Exp $ */
3
4 /*
5 * Copyright (c) 1989, 1991, 1993, 1995
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Jan-Simon Pendry.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35 #ifdef HAVE_CONFIG_H
36 # include <config.h>
37 #endif
38 #ifndef HAVE_REALPATH
39
40 #include <sys/cdefs.h>
41 #include <sys/param.h>
42 #include <sys/stat.h>
43
44 #include <errno.h>
45 #ifdef HAVE_STDLIB_H
46 # include <stdlib.h>
47 #endif
48 #ifdef HAVE_STRING_H
49 # include <string.h>
50 #endif
51 #ifdef HAVE_UNISTD_H
52 # include <unistd.h>
53 #endif
54
55 #ifndef __restrict
56 # define __restrict /* restrict */
57 #endif
58
59 /*
60 * char *realpath(const char *path, char *resolved);
61 *
62 * Find the real name of path, by removing all ".", ".." and symlink
63 * components. Returns (resolved) on success, or (NULL) on failure,
64 * in which case the path which caused trouble is left in (resolved).
65 */
66 char *
realpath(const char * __restrict path,char * __restrict resolved)67 realpath(const char * __restrict path, char * __restrict resolved)
68 {
69 struct stat sb;
70 int idx = 0, nlnk = 0;
71 const char *q;
72 char *p, wbuf[2][MAXPATHLEN], *fres;
73 size_t len;
74 ssize_t n;
75
76 /* POSIX sez we must test for this */
77 if (path == NULL) {
78 errno = EINVAL;
79 return NULL;
80 }
81
82 if (resolved == NULL) {
83 fres = resolved = malloc(MAXPATHLEN);
84 if (resolved == NULL)
85 return NULL;
86 } else
87 fres = NULL;
88
89
90 /*
91 * Build real path one by one with paying an attention to .,
92 * .. and symbolic link.
93 */
94
95 /*
96 * `p' is where we'll put a new component with prepending
97 * a delimiter.
98 */
99 p = resolved;
100
101 if (*path == '\0') {
102 *p = '\0';
103 errno = ENOENT;
104 goto out;
105 }
106
107 /* If relative path, start from current working directory. */
108 if (*path != '/') {
109 /* check for resolved pointer to appease coverity */
110 if (resolved && getcwd(resolved, MAXPATHLEN) == NULL) {
111 p[0] = '.';
112 p[1] = '\0';
113 goto out;
114 }
115 len = strlen(resolved);
116 if (len > 1)
117 p += len;
118 }
119
120 loop:
121 /* Skip any slash. */
122 while (*path == '/')
123 path++;
124
125 if (*path == '\0') {
126 if (p == resolved)
127 *p++ = '/';
128 *p = '\0';
129 return resolved;
130 }
131
132 /* Find the end of this component. */
133 q = path;
134 do
135 q++;
136 while (*q != '/' && *q != '\0');
137
138 /* Test . or .. */
139 if (path[0] == '.') {
140 if (q - path == 1) {
141 path = q;
142 goto loop;
143 }
144 if (path[1] == '.' && q - path == 2) {
145 /* Trim the last component. */
146 if (p != resolved)
147 while (*--p != '/')
148 continue;
149 path = q;
150 goto loop;
151 }
152 }
153
154 /* Append this component. */
155 if (p - resolved + 1 + q - path + 1 > MAXPATHLEN) {
156 errno = ENAMETOOLONG;
157 if (p == resolved)
158 *p++ = '/';
159 *p = '\0';
160 goto out;
161 }
162 p[0] = '/';
163 memcpy(&p[1], path,
164 /* LINTED We know q > path. */
165 q - path);
166 p[1 + q - path] = '\0';
167
168 /*
169 * If this component is a symlink, toss it and prepend link
170 * target to unresolved path.
171 */
172 if (lstat(resolved, &sb) == -1)
173 goto out;
174
175 if (S_ISLNK(sb.st_mode)) {
176 if (nlnk++ >= MAXSYMLINKS) {
177 errno = ELOOP;
178 goto out;
179 }
180 n = readlink(resolved, wbuf[idx], sizeof(wbuf[0]) - 1);
181 if (n < 0)
182 goto out;
183 if (n == 0) {
184 errno = ENOENT;
185 goto out;
186 }
187
188 /* Append unresolved path to link target and switch to it. */
189 if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
190 errno = ENAMETOOLONG;
191 goto out;
192 }
193 memcpy(&wbuf[idx][n], q, len + 1);
194 path = wbuf[idx];
195 idx ^= 1;
196
197 /* If absolute symlink, start from root. */
198 if (*path == '/')
199 p = resolved;
200 goto loop;
201 }
202 if (*q == '/' && !S_ISDIR(sb.st_mode)) {
203 errno = ENOTDIR;
204 goto out;
205 }
206
207 /* Advance both resolved and unresolved path. */
208 p += 1 + q - path;
209 path = q;
210 goto loop;
211 out:
212 free(fres);
213 return NULL;
214 }
215 #endif
216