port/gen/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 (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*  Copyright (c) 1988 AT&T */
/*    All Rights Reserved   */

#include "lint.h"
#include <sys/types.h>
#include <dirent.h>
#include <sys/param.h>
#include <limits.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/*
 * Canonicalize the path given in file_name, resolving away all symbolic link
 * components.  Store the result into the buffer named by resolved_name, which
 * must be long enough (PATH_MAX bytes will suffice).  Returns NULL
 * on failure and resolved_name on success.  On failure, to maintain
 * compatibility with the past, the contents of file_name will be copied
 * into resolved_name.
 */
static char *
realpath_impl(const char *file_name, char *resolved_name)
{
    char cwd[PATH_MAX];
    int len;

    if (file_name == NULL) {
        errno = EINVAL;
        return (NULL);
    }

    /*
     * Call resolvepath() to resolve all the symlinks in file_name,
     * eliminate embedded "." components, and collapse embedded ".."
     * components.  We may be left with leading ".." components.
     */
    if ((len = resolvepath(file_name, resolved_name, PATH_MAX)) < 0) {
        (void) strlcpy(resolved_name, file_name, PATH_MAX);
        return (NULL);      /* errno set by resolvepath() */
    }

    if (len >= PATH_MAX)    /* "can't happen" */
        len = PATH_MAX - 1;
    resolved_name[len] = '\0';

    if (*resolved_name == '/')  /* nothing more to do */
        return (resolved_name);

    /*
     * Prepend the current working directory to the relative path.
     * If the relative path is not empty (or "."), collapse all of the
     * resulting embedded ".." components with trailing cwd components.
     * We know that getcwd() returns a path name free of symlinks.
     */
    if (getcwd(cwd, sizeof (cwd)) == NULL) {
        (void) strlcpy(resolved_name, file_name, PATH_MAX);
        return (NULL);      /* errno set by getcwd() */
    }

    if (len != 0 && strcmp(resolved_name, ".") != 0) {
        char *relpath = resolved_name;
        char *endcwd = cwd + strlen(cwd);

        /*
         * Eliminate ".." components from the relative path
         * left-to-right, components from cwd right-to-left.
         */
        relpath[len++] = '/';
        while (len >= 3 && strncmp(relpath, "../", 3) == 0) {
            relpath += 3;
            len -= 3;
            while (*--endcwd != '/')
                continue;
        }
        if (len == 0) {
            /* the relative path was all ".." components */
            *endcwd = '\0';
        } else {
            /* there are non-null components on both sides */
            relpath[--len] = '\0';
            *endcwd++ = '/';
            if (endcwd + len >= cwd + PATH_MAX) {
                (void) strlcpy(resolved_name,
                    file_name, PATH_MAX);
                errno = ENAMETOOLONG;
                return (NULL);
            }
            (void) strcpy(endcwd, relpath);
        }
    }

    (void) strcpy(resolved_name, cwd);
    return (resolved_name);
}

/*
 * Canonicalize the path given in file_name, resolving away all symbolic link
 * components.  If resolved_name is a null pointer, return a malloc()d
 * buffer containing the result, else store the result into resolved_name
 * and return resolved_name.  Return NULL on failure.
 */
char *
realpath(const char *file_name, char *resolved_name)
{
    char buffer[PATH_MAX];

    if (resolved_name != NULL)
        return (realpath_impl(file_name, resolved_name));

    if (realpath_impl(file_name, buffer) != NULL)
        return (strdup(buffer));

    return (NULL);
}

/*
 * GNU extension.
 */
char *
canonicalize_file_name(const char *path)
{
    return (realpath(path, NULL));
}