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-rw-r--r--utils/chroot_realpath.c163
1 files changed, 163 insertions, 0 deletions
diff --git a/utils/chroot_realpath.c b/utils/chroot_realpath.c
new file mode 100644
index 000000000..43ce9a528
--- /dev/null
+++ b/utils/chroot_realpath.c
@@ -0,0 +1,163 @@
+/*
+ * chroot_realpath.c -- reslove pathname as if inside chroot
+ * Based on realpath.c Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Library Public License for more details.
+ *
+ * 2005/09/12: Dan Howell (modified from realpath.c to emulate chroot)
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <limits.h> /* for PATH_MAX */
+#include <sys/param.h> /* for MAXPATHLEN */
+#include <errno.h>
+#ifndef __set_errno
+#define __set_errno(val) ((errno) = (val))
+#endif
+
+#include <sys/stat.h> /* for S_IFLNK */
+
+#ifndef PATH_MAX
+#define PATH_MAX _POSIX_PATH_MAX
+#endif
+
+#define MAX_READLINKS 32
+
+char *chroot_realpath(const char *chroot, const char *path, char resolved_path[])
+{
+ char copy_path[PATH_MAX];
+ char link_path[PATH_MAX];
+ char got_path[PATH_MAX];
+ char *got_path_root = got_path;
+ char *new_path = got_path;
+ char *max_path;
+ int readlinks = 0;
+ int n;
+ int chroot_len;
+
+ /* Trivial case. */
+ if (chroot == NULL || *chroot == '\0' ||
+ (*chroot == '/' && chroot[1] == '\0')) {
+ strcpy(resolved_path, path);
+ return resolved_path;
+ }
+
+ chroot_len = strlen(chroot);
+
+ if (chroot_len + strlen(path) >= PATH_MAX - 3) {
+ __set_errno(ENAMETOOLONG);
+ return NULL;
+ }
+
+ /* Make a copy of the source path since we may need to modify it. */
+ strcpy(copy_path, path);
+ path = copy_path;
+ max_path = copy_path + PATH_MAX - chroot_len - 3;
+
+ /* Start with the chroot path. */
+ strcpy(new_path, chroot);
+ new_path += chroot_len;
+ while (*new_path == '/' && new_path > got_path)
+ new_path--;
+ got_path_root = new_path;
+ *new_path++ = '/';
+
+ /* Expand each slash-separated pathname component. */
+ while (*path != '\0') {
+ /* Ignore stray "/". */
+ if (*path == '/') {
+ path++;
+ continue;
+ }
+ if (*path == '.') {
+ /* Ignore ".". */
+ if (path[1] == '\0' || path[1] == '/') {
+ path++;
+ continue;
+ }
+ if (path[1] == '.') {
+ if (path[2] == '\0' || path[2] == '/') {
+ path += 2;
+ /* Ignore ".." at root. */
+ if (new_path == got_path_root + 1)
+ continue;
+ /* Handle ".." by backing up. */
+ while ((--new_path)[-1] != '/');
+ continue;
+ }
+ }
+ }
+ /* Safely copy the next pathname component. */
+ while (*path != '\0' && *path != '/') {
+ if (path > max_path) {
+ __set_errno(ENAMETOOLONG);
+ return NULL;
+ }
+ *new_path++ = *path++;
+ }
+ if (*path == '\0')
+ /* Don't follow symlink for last pathname component. */
+ break;
+#ifdef S_IFLNK
+ /* Protect against infinite loops. */
+ if (readlinks++ > MAX_READLINKS) {
+ __set_errno(ELOOP);
+ return NULL;
+ }
+ /* See if latest pathname component is a symlink. */
+ *new_path = '\0';
+ n = readlink(got_path, link_path, PATH_MAX - 1);
+ if (n < 0) {
+ /* EINVAL means the file exists but isn't a symlink. */
+ if (errno != EINVAL) {
+ /* Make sure it's null terminated. */
+ *new_path = '\0';
+ strcpy(resolved_path, got_path);
+ return NULL;
+ }
+ } else {
+ /* Note: readlink doesn't add the null byte. */
+ link_path[n] = '\0';
+ if (*link_path == '/')
+ /* Start over for an absolute symlink. */
+ new_path = got_path_root;
+ else
+ /* Otherwise back up over this component. */
+ while (*(--new_path) != '/');
+ /* Safe sex check. */
+ if (strlen(path) + n >= PATH_MAX - 2) {
+ __set_errno(ENAMETOOLONG);
+ return NULL;
+ }
+ /* Insert symlink contents into path. */
+ strcat(link_path, path);
+ strcpy(copy_path, link_path);
+ path = copy_path;
+ }
+#endif /* S_IFLNK */
+ *new_path++ = '/';
+ }
+ /* Delete trailing slash but don't whomp a lone slash. */
+ if (new_path != got_path + 1 && new_path[-1] == '/')
+ new_path--;
+ /* Make sure it's null terminated. */
+ *new_path = '\0';
+ strcpy(resolved_path, got_path);
+ return resolved_path;
+}