xref: /titanic_41/usr/src/cmd/ssh/libopenbsd-compat/common/realpath.c (revision e4d060fb4c00d44cd578713eb9a921f594b733b8)
1 /*
2  * Copyright (c) 1994
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Jan-Simon Pendry.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 #include "includes.h"
31 
32 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
33 
34 #if defined(LIBC_SCCS) && !defined(lint)
35 static char *rcsid = "$OpenBSD: realpath.c,v 1.7 2002/05/24 21:22:37 deraadt Exp $";
36 #endif /* LIBC_SCCS and not lint */
37 
38 #include <sys/param.h>
39 #include <sys/stat.h>
40 
41 #include <errno.h>
42 #include <fcntl.h>
43 #include <stdlib.h>
44 #include <string.h>
45 #include <unistd.h>
46 
47 /*
48  * MAXSYMLINKS
49  */
50 #ifndef MAXSYMLINKS
51 #define MAXSYMLINKS 5
52 #endif
53 
54 /*
55  * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
56  *
57  * Find the real name of path, by removing all ".", ".." and symlink
58  * components.  Returns (resolved) on success, or (NULL) on failure,
59  * in which case the path which caused trouble is left in (resolved).
60  */
61 char *
62 realpath(const char *path, char *resolved)
63 {
64 	struct stat sb;
65 	int fd, n, rootd, serrno = 0;
66 	char *p, *q, wbuf[MAXPATHLEN], start[MAXPATHLEN];
67 	int symlinks = 0;
68 
69 	/* Save the starting point. */
70 	getcwd(start,MAXPATHLEN);
71 	if ((fd = open(".", O_RDONLY)) < 0) {
72 		(void)strlcpy(resolved, ".", MAXPATHLEN);
73 		return (NULL);
74 	}
75 	close(fd);
76 
77 	/* Convert "." -> "" to optimize away a needless lstat() and chdir() */
78 	if (path[0] == '.' && path[1] == '\0')
79 		path = "";
80 
81 	/*
82 	 * Find the dirname and basename from the path to be resolved.
83 	 * Change directory to the dirname component.
84 	 * lstat the basename part.
85 	 *     if it is a symlink, read in the value and loop.
86 	 *     if it is a directory, then change to that directory.
87 	 * get the current directory name and append the basename.
88 	 */
89 	strlcpy(resolved, path, MAXPATHLEN);
90 loop:
91 	q = strrchr(resolved, '/');
92 	if (q != NULL) {
93 		p = q + 1;
94 		if (q == resolved)
95 			q = "/";
96 		else {
97 			do {
98 				--q;
99 			} while (q > resolved && *q == '/');
100 			q[1] = '\0';
101 			q = resolved;
102 		}
103 		if (chdir(q) < 0)
104 			goto err1;
105 	} else
106 		p = resolved;
107 
108 	/* Deal with the last component. */
109 	if (*p != '\0' && lstat(p, &sb) == 0) {
110 		if (S_ISLNK(sb.st_mode)) {
111 			if (++symlinks > MAXSYMLINKS) {
112 				serrno = ELOOP;
113 				goto err1;
114 			}
115 			n = readlink(p, resolved, MAXPATHLEN-1);
116 			if (n < 0)
117 				goto err1;
118 			resolved[n] = '\0';
119 			goto loop;
120 		}
121 		if (S_ISDIR(sb.st_mode)) {
122 			if (chdir(p) < 0)
123 				goto err1;
124 			p = "";
125 		}
126 	}
127 
128 	/*
129 	 * Save the last component name and get the full pathname of
130 	 * the current directory.
131 	 */
132 	(void)strlcpy(wbuf, p, sizeof wbuf);
133 	if (getcwd(resolved, MAXPATHLEN) == 0)
134 		goto err1;
135 
136 	/*
137 	 * Join the two strings together, ensuring that the right thing
138 	 * happens if the last component is empty, or the dirname is root.
139 	 */
140 	if (resolved[0] == '/' && resolved[1] == '\0')
141 		rootd = 1;
142 	else
143 		rootd = 0;
144 
145 	if (*wbuf) {
146 		if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
147 			serrno = ENAMETOOLONG;
148 			goto err1;
149 		}
150 		if (rootd == 0)
151 			(void)strcat(resolved, "/");
152 		(void)strcat(resolved, wbuf);
153 	}
154 
155 	/* Go back to where we came from. */
156 	if (chdir(start) < 0) {
157 		serrno = errno;
158 		goto err2;
159 	}
160 	return (resolved);
161 
162 err1:	chdir(start);
163 err2:	errno = serrno;
164 	return (NULL);
165 }
166 #endif /* !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH) */
167 
168 #pragma ident	"%Z%%M%	%I%	%E% SMI"
169