xref: /illumos-gate/usr/src/lib/libdevinfo/devinfo_realpath.c (revision 1da57d551424de5a9d469760be7c4b4d4f10a755)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the authors may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/realpath.c
 * $OpenBSD: realpath.c,v 1.13 2005/08/08 08:05:37 espie Exp $
 */

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>

/*
 * char *s_realpath(const char *path, char resolved_path[MAXPATHLEN]);
 *
 * Find the real name of path, by removing all ".", ".." and symlink
 * components.  Returns (resolved) on success, or (NULL) on failure,
 * in which case the path which caused trouble is left in (resolved).
 *
 * DEVINFO: For libdevinfo we have added code to special case symlinks into
 * /devices - the path below that point is known to not point to any
 * additional symlinks.  This knowledge allows us to avoid causing attach.
 */
char *
s_realpath(const char *path, char *resolved)
{
	struct stat sb;
	char *p, *q, *s;
	size_t left_len, resolved_len;
	unsigned symlinks;
	int serrno, slen;
	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];

	serrno = errno;
	symlinks = 0;
	if (path[0] == '/') {
		resolved[0] = '/';
		resolved[1] = '\0';
		if (path[1] == '\0')
			return (resolved);
		resolved_len = 1;
		left_len = strlcpy(left, path + 1, sizeof (left));
	} else {
		if (getcwd(resolved, PATH_MAX) == NULL) {
			(void) strlcpy(resolved, ".", PATH_MAX);
			return (NULL);
		}
		resolved_len = strlen(resolved);
		left_len = strlcpy(left, path, sizeof (left));
	}
	if (left_len >= sizeof (left) || resolved_len >= PATH_MAX) {
		errno = ENAMETOOLONG;
		return (NULL);
	}

	/*
	 * Iterate over path components in `left'.
	 */
	while (left_len != 0) {
		/*
		 * Extract the next path component and adjust `left'
		 * and its length.
		 */
		p = strchr(left, '/');
		s = p ? p : left + left_len;
		if (s - left >= sizeof (next_token)) {
			errno = ENAMETOOLONG;
			return (NULL);
		}
		(void) memcpy(next_token, left, s - left);
		next_token[s - left] = '\0';
		left_len -= s - left;
		if (p != NULL)
			(void) memmove(left, s + 1, left_len + 1);
		if (resolved[resolved_len - 1] != '/') {
			if (resolved_len + 1 >= PATH_MAX) {
				errno = ENAMETOOLONG;
				return (NULL);
			}
			resolved[resolved_len++] = '/';
			resolved[resolved_len] = '\0';
		}
		if (next_token[0] == '\0')
			continue;
		else if (strcmp(next_token, ".") == 0)
			continue;
		else if (strcmp(next_token, "..") == 0) {
			/*
			 * Strip the last path component except when we have
			 * single "/"
			 */
			if (resolved_len > 1) {
				resolved[resolved_len - 1] = '\0';
				q = strrchr(resolved, '/') + 1;
				*q = '\0';
				resolved_len = q - resolved;
			}
			continue;
		}

		/*
		 * Append the next path component and lstat() it. If
		 * lstat() fails we still can return successfully if
		 * there are no more path components left.
		 */
		resolved_len = strlcat(resolved, next_token, PATH_MAX);
		if (resolved_len >= PATH_MAX) {
			errno = ENAMETOOLONG;
			return (NULL);
		}

		/*
		 * DEVINFO: Check if link points into /devices and resolve
		 * without causing attach if that is the case - there are no
		 * further symlinks in /devices.
		 */
		if (strcmp(resolved, "/devices") == 0) {
			resolved[resolved_len] = '/';
			resolved_len = strlcat(resolved, left, sizeof (left));
			left_len = 0;
			continue;
		}

		if (lstat(resolved, &sb) != 0) {
			if (errno == ENOENT && p == NULL) {
				errno = serrno;
				return (resolved);
			}
			return (NULL);
		}

		if (S_ISLNK(sb.st_mode)) {
			if (symlinks++ > MAXSYMLINKS) {
				errno = ELOOP;
				return (NULL);
			}
			slen = readlink(resolved, symlink,
			    sizeof (symlink) - 1);
			if (slen < 0)
				return (NULL);
			symlink[slen] = '\0';

			if (symlink[0] == '/') {
				resolved[1] = 0;
				resolved_len = 1;
			} else if (resolved_len > 1) {
				/* Strip the last path component. */
				resolved[resolved_len - 1] = '\0';
				q = strrchr(resolved, '/') + 1;
				*q = '\0';
				resolved_len = q - resolved;
			}

			/*
			 * If there are any path components left, then
			 * append them to symlink. The result is placed
			 * in `left'.
			 */
			if (p != NULL) {
				if (symlink[slen - 1] != '/') {
					if (slen + 1 >= sizeof (symlink)) {
						errno = ENAMETOOLONG;
						return (NULL);
					}
					symlink[slen] = '/';
					symlink[slen + 1] = 0;
				}
				left_len = strlcat(symlink, left,
				    sizeof (left));
				if (left_len >= sizeof (left)) {
					errno = ENAMETOOLONG;
					return (NULL);
				}
			}
			left_len = strlcpy(left, symlink, sizeof (left));
		}
	}

	/*
	 * Remove trailing slash except when the resolved pathname
	 * is a single "/".
	 */
	if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
		resolved[resolved_len - 1] = '\0';
	return (resolved);
}