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/*
* 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.
*/
/*
* This is originally from:
* android-n-mr2-preview-1-303-gccec0f4c1
* libc/upstream-freebsd/lib/libc/stdlib/realpath.c
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)realpath.c 8.1 (Berkeley) 2/16/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "base/string_util.h"
#include "SandboxBroker.h"
// Original copy in, but not usable from here:
// toolkit/crashreporter/google-breakpad/src/common/linux/linux_libc_support.cc
static size_t my_strlcat(char* s1, const char* s2, size_t len) {
size_t pos1 = 0;
while (pos1 < len && s1[pos1] != '\0') pos1++;
if (pos1 == len) return pos1;
return pos1 + base::strlcpy(s1 + pos1, s2, len - pos1);
}
namespace mozilla {
/*
* Original: realpath
* 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).
* Changes:
* Resolve relative paths, but don't allow backing out of a symlink
* target. Fail with permission error if any dir is writable.
*/
char* SandboxBroker::SymlinkPath(const Policy* policy,
const char* __restrict path,
char* __restrict resolved, int* perms) {
struct stat sb;
char *p, *q, *s;
size_t left_len, resolved_len, backup_allowed;
unsigned symlinks;
int m, slen;
char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
if (*perms) {
*perms = 0;
}
if (path == NULL) {
errno = EINVAL;
return (NULL);
}
if (path[0] == '\0') {
errno = ENOENT;
return (NULL);
}
if (resolved == NULL) {
resolved = (char*)malloc(PATH_MAX);
if (resolved == NULL) return (NULL);
m = 1;
} else
m = 0;
symlinks = 0;
backup_allowed = PATH_MAX;
if (path[0] == '/') {
resolved[0] = '/';
resolved[1] = '\0';
if (path[1] == '\0') return (resolved);
resolved_len = 1;
left_len = base::strlcpy(left, path + 1, sizeof(left));
} else {
if (getcwd(resolved, PATH_MAX) == NULL) {
if (m)
free(resolved);
else {
resolved[0] = '.';
resolved[1] = '\0';
}
return (NULL);
}
resolved_len = strlen(resolved);
left_len = base::strlcpy(left, path, sizeof(left));
}
if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
if (m) free(resolved);
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 >= (ssize_t)sizeof(next_token)) {
if (m) free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
memcpy(next_token, left, s - left);
next_token[s - left] = '\0';
left_len -= s - left;
if (p != NULL) memmove(left, s + 1, left_len + 1);
if (resolved[resolved_len - 1] != '/') {
if (resolved_len + 1 >= PATH_MAX) {
if (m) free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
resolved[resolved_len++] = '/';
resolved[resolved_len] = '\0';
}
if (next_token[0] == '\0') {
/* Handle consequential slashes. */
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) {
if (backup_allowed > 0) {
resolved[resolved_len - 1] = '\0';
q = strrchr(resolved, '/') + 1;
*q = '\0';
resolved_len = q - resolved;
backup_allowed--;
} else {
// Backing out past a symlink target.
// We don't allow this, because it can eliminate
// permissions we accumulated while descending.
if (m) free(resolved);
errno = EPERM;
return (NULL);
}
}
continue;
}
/*
* Append the next path component and lstat() it.
*/
resolved_len = my_strlcat(resolved, next_token, PATH_MAX);
backup_allowed++;
if (resolved_len >= PATH_MAX) {
if (m) free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
if (lstat(resolved, &sb) != 0) {
if (m) free(resolved);
return (NULL);
}
if (S_ISLNK(sb.st_mode)) {
if (symlinks++ > MAXSYMLINKS) {
if (m) free(resolved);
errno = ELOOP;
return (NULL);
}
/* Our changes start here:
* It's a symlink, check for write permissions on the path where
* it sits in, in which case we won't resolve and just error out. */
int link_path_perms = policy->Lookup(resolved);
if (link_path_perms & MAY_WRITE) {
if (m) free(resolved);
errno = EPERM;
return (NULL);
} else {
/* Accumulate permissions so far */
*perms |= link_path_perms;
}
/* Original symlink lookup code */
slen = readlink(resolved, symlink, sizeof(symlink) - 1);
if (slen < 0) {
if (m) free(resolved);
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 >= (ssize_t)sizeof(symlink)) {
if (m) free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
symlink[slen] = '/';
symlink[slen + 1] = 0;
}
left_len = my_strlcat(symlink, left, sizeof(symlink));
if (left_len >= sizeof(left)) {
if (m) free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
}
left_len = base::strlcpy(left, symlink, sizeof(left));
backup_allowed = 0;
} else if (!S_ISDIR(sb.st_mode) && p != NULL) {
if (m) free(resolved);
errno = ENOTDIR;
return (NULL);
}
}
/*
* Remove trailing slash except when the resolved pathname
* is a single "/".
*/
if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
resolved[resolved_len - 1] = '\0';
/* Accumulate permissions. */
*perms |= policy->Lookup(resolved);
return (resolved);
}
} // namespace mozilla