xref: /illumos-gate/usr/src/lib/libc/port/gen/realpath.c (revision 6a634c9d)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
24  */
25 
26 /*	Copyright (c) 1988 AT&T	*/
27 /*	  All Rights Reserved  	*/
28 
29 #include "lint.h"
30 #include <sys/types.h>
31 #include <dirent.h>
32 #include <sys/param.h>
33 #include <limits.h>
34 #include <errno.h>
35 #include <stdlib.h>
36 #include <unistd.h>
37 #include <string.h>
38 
39 /*
40  * Canonicalize the path given in file_name, resolving away all symbolic link
41  * components.  Store the result into the buffer named by resolved_name, which
42  * must be long enough (PATH_MAX bytes will suffice).  Returns NULL
43  * on failure and resolved_name on success.  On failure, to maintain
44  * compatibility with the past, the contents of file_name will be copied
45  * into resolved_name.
46  */
47 static char *
realpath_impl(const char * file_name,char * resolved_name)48 realpath_impl(const char *file_name, char *resolved_name)
49 {
50 	char cwd[PATH_MAX];
51 	int len;
52 
53 	if (file_name == NULL) {
54 		errno = EINVAL;
55 		return (NULL);
56 	}
57 
58 	/*
59 	 * Call resolvepath() to resolve all the symlinks in file_name,
60 	 * eliminate embedded "." components, and collapse embedded ".."
61 	 * components.  We may be left with leading ".." components.
62 	 */
63 	if ((len = resolvepath(file_name, resolved_name, PATH_MAX)) < 0) {
64 		(void) strlcpy(resolved_name, file_name, PATH_MAX);
65 		return (NULL);		/* errno set by resolvepath() */
66 	}
67 
68 	if (len >= PATH_MAX)	/* "can't happen" */
69 		len = PATH_MAX - 1;
70 	resolved_name[len] = '\0';
71 
72 	if (*resolved_name == '/')	/* nothing more to do */
73 		return (resolved_name);
74 
75 	/*
76 	 * Prepend the current working directory to the relative path.
77 	 * If the relative path is not empty (or "."), collapse all of the
78 	 * resulting embedded ".." components with trailing cwd components.
79 	 * We know that getcwd() returns a path name free of symlinks.
80 	 */
81 	if (getcwd(cwd, sizeof (cwd)) == NULL) {
82 		(void) strlcpy(resolved_name, file_name, PATH_MAX);
83 		return (NULL);		/* errno set by getcwd() */
84 	}
85 
86 	if (len != 0 && strcmp(resolved_name, ".") != 0) {
87 		char *relpath = resolved_name;
88 		char *endcwd = cwd + strlen(cwd);
89 
90 		/*
91 		 * Eliminate ".." components from the relative path
92 		 * left-to-right, components from cwd right-to-left.
93 		 */
94 		relpath[len++] = '/';
95 		while (len >= 3 && strncmp(relpath, "../", 3) == 0) {
96 			relpath += 3;
97 			len -= 3;
98 			while (*--endcwd != '/')
99 				continue;
100 		}
101 		if (len == 0) {
102 			/* the relative path was all ".." components */
103 			*endcwd = '\0';
104 		} else {
105 			/* there are non-null components on both sides */
106 			relpath[--len] = '\0';
107 			*endcwd++ = '/';
108 			if (endcwd + len >= cwd + PATH_MAX) {
109 				(void) strlcpy(resolved_name,
110 				    file_name, PATH_MAX);
111 				errno = ENAMETOOLONG;
112 				return (NULL);
113 			}
114 			(void) strcpy(endcwd, relpath);
115 		}
116 	}
117 
118 	(void) strcpy(resolved_name, cwd);
119 	return (resolved_name);
120 }
121 
122 /*
123  * Canonicalize the path given in file_name, resolving away all symbolic link
124  * components.  If resolved_name is a null pointer, return a malloc()d
125  * buffer containing the result, else store the result into resolved_name
126  * and return resolved_name.  Return NULL on failure.
127  */
128 char *
realpath(const char * file_name,char * resolved_name)129 realpath(const char *file_name, char *resolved_name)
130 {
131 	char buffer[PATH_MAX];
132 
133 	if (resolved_name != NULL)
134 		return (realpath_impl(file_name, resolved_name));
135 
136 	if (realpath_impl(file_name, buffer) != NULL)
137 		return (strdup(buffer));
138 
139 	return (NULL);
140 }
141 
142 /*
143  * GNU extension.
144  */
145 char *
canonicalize_file_name(const char * path)146 canonicalize_file_name(const char *path)
147 {
148 	return (realpath(path, NULL));
149 }
150