fix #40931 (open_basedir bypass via symlink and move_uploaded_file())

NEWS

@@ -57,6 +57,8 @@ PHP                                                                        NEWS
 - Fixed bug #40998 (long session array keys are truncated). (Tony)
 - Implement feature request #40947, allow a single filter as argument 
   for filter_var_array (Pierre)
+- Fixed bug #40931 (open_basedir bypass via symlink and move_uploaded_file()). 
+  (Tony)
 - Fixed bug #40921 (php_default_post_reader crashes when post_max_size is
   exceeded). (trickie at gmail dot com, Ilia)
 - Fixed bug #40915 (addcslashes unexpected behavior with binary input). (Tony)

main/fopen_wrappers.c

@@ -90,8 +90,12 @@ PHPAPI int php_check_specific_open_basedir(const char *basedir, const char *path
 	char resolved_name[MAXPATHLEN];
 	char resolved_basedir[MAXPATHLEN];
 	char local_open_basedir[MAXPATHLEN];
+	char path_tmp[MAXPATHLEN];
+	char *path_file;
 	int resolved_basedir_len;
 	int resolved_name_len;
+	int path_len;
+	int nesting_level = 0;
 	
 	/* Special case basedir==".": Use script-directory */
 	if (strcmp(basedir, ".") || !VCWD_GETCWD(local_open_basedir, MAXPATHLEN)) {
@@ -99,8 +103,64 @@ PHPAPI int php_check_specific_open_basedir(const char *basedir, const char *path
 		strlcpy(local_open_basedir, basedir, sizeof(local_open_basedir));
 	}
 
-	/* Resolve the real path into resolved_name */
-	if ((expand_filepath(path, resolved_name TSRMLS_CC) != NULL) && (expand_filepath(local_open_basedir, resolved_basedir TSRMLS_CC) != NULL)) {
+	path_len = strlen(path);
+	if (path_len > (MAXPATHLEN - 1)) {
+		/* empty and too long paths are invalid */
+		return -1;
+	}
+
+	/* normalize and expand path */
+	if (expand_filepath(path, resolved_name TSRMLS_CC) == NULL) {
+		return -1;
+	}
+	
+	path_len = strlen(resolved_name);
+	memcpy(path_tmp, resolved_name, path_len + 1); /* safe */
+
+	while (VCWD_REALPATH(path_tmp, resolved_name) == NULL) {
+#ifdef HAVE_SYMLINK
+		if (nesting_level == 0) {
+			int ret;
+			char buf[MAXPATHLEN];
+			
+			ret = readlink(path_tmp, buf, MAXPATHLEN - 1);
+			if (ret < 0) {
+				/* not a broken symlink, move along.. */
+			} else {
+				/* put the real path into the path buffer */
+				memcpy(path_tmp, buf, ret);
+				path_tmp[ret] = '\0';
+			}
+		}
+#endif
+
+#if defined(PHP_WIN32) || defined(NETWARE)
+		path_file = strrchr(path_tmp, DEFAULT_SLASH);
+		if (!path_file) {
+			path_file = strrchr(path_tmp, '/');
+		}
+#else
+		path_file = strrchr(path_tmp, DEFAULT_SLASH);
+#endif
+		if (!path_file) {
+			/* none of the path components exist. definitely not in open_basedir.. */
+			return -1;
+		} else {
+			path_len = path_file - path_tmp + 1;
+#if defined(PHP_WIN32) || defined(NETWARE)
+			if (path_len > 1 && path_tmp[path_len - 2] == ':') {
+				/* this is c:\,  */
+				path_tmp[path_len] = '\0';
+			}
+#else
+			path_tmp[path_len - 1] = '\0';
+#endif
+		}
+		nesting_level++;
+	}
+
+	/* Resolve open_basedir to resolved_basedir */
+	if (expand_filepath(local_open_basedir, resolved_basedir TSRMLS_CC) != NULL) {
 		/* Handler for basedirs that end with a / */
 		resolved_basedir_len = strlen(resolved_basedir);
 		if (basedir[strlen(basedir) - 1] == PHP_DIR_SEPARATOR) {
@@ -110,7 +170,7 @@ PHPAPI int php_check_specific_open_basedir(const char *basedir, const char *path
 			}
 		}
 
-		if (path[strlen(path)-1] == PHP_DIR_SEPARATOR) {
+		if (path_tmp[path_len - 1] == PHP_DIR_SEPARATOR) {
 			resolved_name_len = strlen(resolved_name);
 			if (resolved_name[resolved_name_len - 1] != PHP_DIR_SEPARATOR) {
 				resolved_name[resolved_name_len] = PHP_DIR_SEPARATOR;