lib/libdevinfo/devinfo_realpath.c

/*
 * 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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * 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);
}