2 * canonicalize.c -- canonicalize pathname by removing symlinks
3 * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU Library Public License as published by
7 * the Free Software Foundation; either version 2, or (at your option)
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU Library Public License for more details.
18 * This routine is part of libc. We include it nevertheless,
19 * since the libc version has some security flaws.
21 * TODO: use canonicalize_file_name() when exist in glibc
28 #include "canonicalize.h"
31 # define MAXSYMLINKS 256
35 myrealpath(const char *path, char *resolved_path, int maxreslth) {
38 char link_path[PATH_MAX+1];
42 npath = resolved_path;
44 /* If it's a relative pathname use getcwd for starters. */
46 if (!getcwd(npath, maxreslth-2))
48 npath += strlen(npath);
56 /* Expand each slash-separated pathname component. */
57 while (*path != '\0') {
58 /* Ignore stray "/" */
63 if (*path == '.' && (path[1] == '\0' || path[1] == '/')) {
68 if (*path == '.' && path[1] == '.' &&
69 (path[2] == '\0' || path[2] == '/')) {
72 while (npath > resolved_path+1 &&
77 /* Safely copy the next pathname component. */
78 while (*path != '\0' && *path != '/') {
79 if (npath-resolved_path > maxreslth-2) {
86 /* Protect against infinite loops. */
87 if (readlinks++ > MAXSYMLINKS) {
92 /* See if last pathname component is a symlink. */
94 n = readlink(resolved_path, link_path, PATH_MAX);
96 /* EINVAL means the file exists but isn't a symlink. */
103 /* Note: readlink doesn't add the null byte. */
105 if (*link_path == '/')
106 /* Start over for an absolute symlink. */
107 npath = resolved_path;
109 /* Otherwise back up over this component. */
110 while (*(--npath) != '/')
113 /* Insert symlink contents into path. */
115 newbuf = malloc(m + n + 1);
118 memcpy(newbuf, link_path, n);
119 memcpy(newbuf + n, path, m + 1);
125 /* Delete trailing slash but don't whomp a lone slash. */
126 if (npath != resolved_path+1 && npath[-1] == '/')
128 /* Make sure it's null terminated. */
132 return resolved_path;
140 canonicalize_path(const char *path) {
141 char canonical[PATH_MAX+2];
146 if (myrealpath (path, canonical, PATH_MAX+1))
147 return strdup(canonical);