core: Remove disable_classes INI setting

Girgias · Girgias · commit d1614896fb2d · 2023-08-24T14:25:12.000+01:00
As described in the email to the PHP internals list [1] this feature is fundamentally broken and pointless. Only internal classes can be disable which brings the following observation. On a minimal build of PHP, with only the mandatory extensions enabled, there are 148 classes/interfaces/traits defined. [2] Other than the SPL ones (and even then), disabling any of these classes will cause issues within the engine. Moreover, the SPL ones are not a security concern. Therefore, any other class that can be disabled must come from an extension that can be disabled altogether. And "disabling" a class from an extension without disabling said extension will render it useless anyway. If a hosting provided is concerned about an extension, then it should not enable it in the first place. Not break it ad hoc. Considering the above, I cannot see how this functionality was ever useful. This is in stark contrast to the disable_functions INI setting, which can be used to selectively remove functionality of an extension without breaking it overall. What makes this setting particularly broken is that it does not unregister the class, it only overwrites the create CE handler to emit a warning and purge the properties and function hashtables. This leads to various use after free, segfaults, and broken expectations for the engine and extensions which define said classes. On top of that, it is possible to actually instantiate such a class (and even classes which actually disallow this like ext/imap) in userland, and pass it to function that are typed against said class without raising a TypeError. However, when trying to do anything with said object stuff is going to explode in countless ways. [1] https://news-web.php.net/php.internals/120896 [2] https://gist.github.com/Girgias/63d55ba1e50b580412b004046daed02b
diff --git a/Zend/tests/bug77494.phpt b/Zend/tests/bug77494.phpt
diff --git a/Zend/tests/disable_classes_warning.phpt b/Zend/tests/disable_classes_warning.phpt
@@ -0,0 +1,27 @@
+--TEST--
+Check that warning is emitted when disabling classes
+--INI--
+disable_classes=Exception
+--FILE--
+<?php
+$o = new Exception();
+var_dump($o);
+?>
+--EXPECTF--
+object(Exception)#1 (7) {
+  ["message":protected]=>
+  string(0) ""
+  ["string":"Exception":private]=>
+  string(0) ""
+  ["code":protected]=>
+  int(0)
+  ["file":protected]=>
+  string(%d) "%s"
+  ["line":protected]=>
+  int(2)
+  ["trace":"Exception":private]=>
+  array(0) {
+  }
+  ["previous":"Exception":private]=>
+  NULL
+}
diff --git a/Zend/tests/errmsg_021.phpt b/Zend/tests/errmsg_021.phpt
diff --git a/Zend/zend_API.c b/Zend/zend_API.c
@@ -3465,77 +3465,6 @@ ZEND_API void zend_disable_functions(const char *function_list) /* {{{ */
 }
 /* }}} */
 
-#ifdef ZEND_WIN32
-#pragma optimize("", off)
-#endif
-static ZEND_COLD zend_object *display_disabled_class(zend_class_entry *class_type) /* {{{ */
-{
-	zend_object *intern;
-
-	intern = zend_objects_new(class_type);
-
-	/* Initialize default properties */
-	if (EXPECTED(class_type->default_properties_count != 0)) {
-		zval *p = intern->properties_table;
-		zval *end = p + class_type->default_properties_count;
-		do {
-			ZVAL_UNDEF(p);
-			p++;
-		} while (p != end);
-	}
-
-	zend_error(E_WARNING, "%s() has been disabled for security reasons", ZSTR_VAL(class_type->name));
-	return intern;
-}
-#ifdef ZEND_WIN32
-#pragma optimize("", on)
-#endif
-/* }}} */
-
-static const zend_function_entry disabled_class_new[] = {
-	ZEND_FE_END
-};
-
-ZEND_API zend_result zend_disable_class(const char *class_name, size_t class_name_length) /* {{{ */
-{
-	zend_class_entry *disabled_class;
-	zend_string *key;
-	zend_function *fn;
-	zend_property_info *prop;
-
-	key = zend_string_alloc(class_name_length, 0);
-	zend_str_tolower_copy(ZSTR_VAL(key), class_name, class_name_length);
-	disabled_class = zend_hash_find_ptr(CG(class_table), key);
-	zend_string_release_ex(key, 0);
-	if (!disabled_class) {
-		return FAILURE;
-	}
-
-	/* Will be reset by INIT_CLASS_ENTRY. */
-	free(disabled_class->interfaces);
-
-	INIT_CLASS_ENTRY_INIT_METHODS((*disabled_class), disabled_class_new);
-	disabled_class->create_object = display_disabled_class;
-
-	ZEND_HASH_MAP_FOREACH_PTR(&disabled_class->function_table, fn) {
-		if ((fn->common.fn_flags & (ZEND_ACC_HAS_RETURN_TYPE|ZEND_ACC_HAS_TYPE_HINTS)) &&
-			fn->common.scope == disabled_class) {
-			zend_free_internal_arg_info(&fn->internal_function);
-		}
-	} ZEND_HASH_FOREACH_END();
-	zend_hash_clean(&disabled_class->function_table);
-	ZEND_HASH_MAP_FOREACH_PTR(&disabled_class->properties_info, prop) {
-		if (prop->ce == disabled_class) {
-			zend_string_release(prop->name);
-			zend_type_release(prop->type, /* persistent */ 1);
-			free(prop);
-		}
-	} ZEND_HASH_FOREACH_END();
-	zend_hash_clean(&disabled_class->properties_info);
-	return SUCCESS;
-}
-/* }}} */
-
 static zend_always_inline zend_class_entry *get_scope(zend_execute_data *frame)
 {
 	return frame && frame->func ? frame->func->common.scope : NULL;
diff --git a/Zend/zend_API.h b/Zend/zend_API.h
@@ -398,7 +398,6 @@ static zend_always_inline zend_result zend_register_class_alias(const char *name
 	zend_register_class_alias_ex(ZEND_NS_NAME(ns, name), sizeof(ZEND_NS_NAME(ns, name))-1, ce, 1)
 
 ZEND_API void zend_disable_functions(const char *function_list);
-ZEND_API zend_result zend_disable_class(const char *class_name, size_t class_name_length);
 
 ZEND_API ZEND_COLD void zend_wrong_param_count(void);
 ZEND_API ZEND_COLD void zend_wrong_property_read(zval *object, zval *property);
diff --git a/main/main.c b/main/main.c
@@ -319,41 +319,6 @@ static PHP_INI_MH(OnSetLogFilter)
 }
 /* }}} */
 
-/* {{{ php_disable_classes */
-static void php_disable_classes(void)
-{
-	char *s = NULL, *e;
-
-	if (!*(INI_STR("disable_classes"))) {
-		return;
-	}
-
-	e = PG(disable_classes) = strdup(INI_STR("disable_classes"));
-
-	while (*e) {
-		switch (*e) {
-			case ' ':
-			case ',':
-				if (s) {
-					*e = '\0';
-					zend_disable_class(s, e-s);
-					s = NULL;
-				}
-				break;
-			default:
-				if (!s) {
-					s = e;
-				}
-				break;
-		}
-		e++;
-	}
-	if (s) {
-		zend_disable_class(s, e-s);
-	}
-}
-/* }}} */
-
 /* {{{ php_binary_init */
 static void php_binary_init(void)
 {
@@ -660,6 +625,17 @@ static PHP_INI_MH(OnChangeMailForceExtra)
 }
 /* }}} */
 
+/* Emit warning when using this INI setting as it is removed */
+static PHP_INI_MH(OnChangeDisableClasses)
+{
+	if (stage != PHP_INI_SYSTEM) {
+			return FAILURE;
+	}
+	php_error_docref("disable_clases", E_WARNING, "The disable_classes INI setting has been removed and has no effect");
+
+	return SUCCESS;
+}
+
 /* defined in browscap.c */
 PHP_INI_MH(OnChangeBrowscap);
 
@@ -757,7 +733,8 @@ PHP_INI_BEGIN()
 	PHP_INI_ENTRY("sendmail_path",	DEFAULT_SENDMAIL_PATH,	PHP_INI_SYSTEM,		NULL)
 	PHP_INI_ENTRY("mail.force_extra_parameters",NULL,		PHP_INI_SYSTEM|PHP_INI_PERDIR,		OnChangeMailForceExtra)
 	PHP_INI_ENTRY("disable_functions",			"",			PHP_INI_SYSTEM,		NULL)
-	PHP_INI_ENTRY("disable_classes",			"",			PHP_INI_SYSTEM,		NULL)
+	// TODO Add warning when disabling classes
+	//PHP_INI_ENTRY("disable_classes",			"",			PHP_INI_SYSTEM,		NULL)
 	PHP_INI_ENTRY("max_file_uploads",			"20",			PHP_INI_SYSTEM|PHP_INI_PERDIR,		NULL)
 	PHP_INI_ENTRY("max_multipart_body_parts",	"-1",			PHP_INI_SYSTEM|PHP_INI_PERDIR,		NULL)
 
@@ -1955,9 +1932,6 @@ static void core_globals_dtor(php_core_globals *core_globals)
 	ZEND_ASSERT(!core_globals->last_error_message);
 	ZEND_ASSERT(!core_globals->last_error_file);
 
-	if (core_globals->disable_classes) {
-		free(core_globals->disable_classes);
-	}
 	if (core_globals->php_binary) {
 		free(core_globals->php_binary);
 	}
@@ -2223,9 +2197,8 @@ zend_result php_module_startup(sapi_module_struct *sf, zend_module_entry *additi
 		}
 	}
 
-	/* disable certain classes and functions as requested by php.ini */
+	/* disable certain functions as requested by php.ini */
 	zend_disable_functions(INI_STR("disable_functions"));
-	php_disable_classes();
 
 	/* make core report what it should */
 	if ((module = zend_hash_str_find_ptr(&module_registry, "core", sizeof("core")-1)) != NULL) {
diff --git a/main/php_globals.h b/main/php_globals.h
@@ -142,7 +142,6 @@ struct _php_core_globals {
 
 	char *php_sys_temp_dir;
 
-	char *disable_classes;
 	zend_long max_input_nesting_level;
 	zend_long max_input_vars;
 
diff --git a/php.ini-development b/php.ini-development
@@ -332,11 +332,6 @@ serialize_precision = -1
 ; https://php.net/disable-functions
 disable_functions =
 
-; This directive allows you to disable certain classes.
-; It receives a comma-delimited list of class names.
-; https://php.net/disable-classes
-disable_classes =
-
 ; Colors for Syntax Highlighting mode.  Anything that's acceptable in
 ; <span style="color: ???????"> would work.
 ; https://php.net/syntax-highlighting
diff --git a/php.ini-production b/php.ini-production
@@ -332,11 +332,6 @@ serialize_precision = -1
 ; https://php.net/disable-functions
 disable_functions =
 
-; This directive allows you to disable certain classes.
-; It receives a comma-delimited list of class names.
-; https://php.net/disable-classes
-disable_classes =
-
 ; Colors for Syntax Highlighting mode.  Anything that's acceptable in
 ; <span style="color: ???????"> would work.
 ; https://php.net/syntax-highlighting
diff --git a/sapi/fpm/fpm/fpm_php.c b/sapi/fpm/fpm/fpm_php.c
@@ -48,35 +48,6 @@ static int fpm_php_zend_ini_alter_master(char *name, int name_length, char *new_
 }
 /* }}} */
 
-static void fpm_php_disable(char *value, int (*zend_disable)(const char *, size_t)) /* {{{ */
-{
-	char *s = 0, *e = value;
-
-	while (*e) {
-		switch (*e) {
-			case ' ':
-			case ',':
-				if (s) {
-					*e = '\0';
-					zend_disable(s, e - s);
-					s = 0;
-				}
-				break;
-			default:
-				if (!s) {
-					s = e;
-				}
-				break;
-		}
-		e++;
-	}
-
-	if (s) {
-		zend_disable(s, e - s);
-	}
-}
-/* }}} */
-
 int fpm_php_apply_defines_ex(struct key_value_s *kv, int mode) /* {{{ */
 {
 
@@ -100,13 +71,6 @@ int fpm_php_apply_defines_ex(struct key_value_s *kv, int mode) /* {{{ */
 		return 1;
 	}
 
-	if (!strcmp(name, "disable_classes") && *value) {
-		char *v = strdup(value);
-		PG(disable_classes) = v;
-		fpm_php_disable(v, zend_disable_class);
-		return 1;
-	}
-
 	return 1;
 }
 /* }}} */
diff --git a/sapi/fpm/www.conf.in b/sapi/fpm/www.conf.in
@@ -474,9 +474,8 @@ pm.max_spare_servers = 3
 ; For php_*flag, valid values are on, off, 1, 0, true, false, yes or no.
 
 ; Defining 'extension' will load the corresponding shared extension from
-; extension_dir. Defining 'disable_functions' or 'disable_classes' will not
-; overwrite previously defined php.ini values, but will append the new value
-; instead.
+; extension_dir. Defining 'disable_functions' will not overwrite previously
+; defined php.ini values, but will append the new value instead.
 
 ; Note: path INI options can be relative and will be expanded with the prefix
 ; (pool, global or @prefix@)
