Create a filesystem abstraction layer for CSM and only allow accessing files that are scanned into it. (#5965)

* Load client-side mods into memory before executing them.

This removes the remaining filesystem access that client-sided mods had and it will hopefully make then more secure.

* Lua Virtual filesystem: don't load the files into memory just scan the filenames into memory.

* Fix the issues with backtrace

* fix most of the issues

* fix code style.

* add a comment

24 files changed, 230 insertions, 101 deletions

diff --git a/builtin/client/init.lua b/builtin/client/init.lua
index 3ac34d845..22256f6f7 100644
--- a/builtin/client/init.lua
+++ b/builtin/client/init.lua
@@ -1,5 +1,5 @@
 -- Minetest: builtin/client/init.lua
-local scriptpath = core.get_builtin_path()..DIR_DELIM
+local scriptpath = core.get_builtin_path()
 local clientpath = scriptpath.."client"..DIR_DELIM
 local commonpath = scriptpath.."common"..DIR_DELIM
 
diff --git a/builtin/game/init.lua b/builtin/game/init.lua
index e2635f07a..ab1503dee 100644
--- a/builtin/game/init.lua
+++ b/builtin/game/init.lua
@@ -1,5 +1,5 @@
 
-local scriptpath = core.get_builtin_path()..DIR_DELIM
+local scriptpath = core.get_builtin_path()
 local commonpath = scriptpath.."common"..DIR_DELIM
 local gamepath = scriptpath.."game"..DIR_DELIM
 
diff --git a/builtin/init.lua b/builtin/init.lua
index 356e119fb..e94f3213a 100644
--- a/builtin/init.lua
+++ b/builtin/init.lua
@@ -25,7 +25,7 @@ os.setlocale("C", "numeric")
 minetest = core
 
 -- Load other files
-local scriptdir = core.get_builtin_path() .. DIR_DELIM
+local scriptdir = core.get_builtin_path()
 local gamepath = scriptdir .. "game" .. DIR_DELIM
 local clientpath = scriptdir .. "client" .. DIR_DELIM
 local commonpath = scriptdir .. "common" .. DIR_DELIM
diff --git a/builtin/mainmenu/dlg_settings_advanced.lua b/builtin/mainmenu/dlg_settings_advanced.lua
index cac9f6983..90b8d1e67 100644
--- a/builtin/mainmenu/dlg_settings_advanced.lua
+++ b/builtin/mainmenu/dlg_settings_advanced.lua
@@ -264,7 +264,7 @@ end
 -- read_all: whether to ignore certain setting types for GUI or not
 -- parse_mods: whether to parse settingtypes.txt in mods and games
 local function parse_config_file(read_all, parse_mods)
-	local builtin_path = core.get_builtin_path() .. DIR_DELIM .. FILENAME
+	local builtin_path = core.get_builtin_path() .. FILENAME
 	local file = io.open(builtin_path, "r")
 	local settings = {}
 	if not file then
@@ -775,4 +775,4 @@ end
 
 -- Generate minetest.conf.example and settings_translation_file.cpp
 
---assert(loadfile(core.get_builtin_path()..DIR_DELIM.."mainmenu"..DIR_DELIM.."generate_from_settingtypes.lua"))(parse_config_file(true, false))
+--assert(loadfile(core.get_builtin_path().."mainmenu"..DIR_DELIM.."generate_from_settingtypes.lua"))(parse_config_file(true, false))
diff --git a/builtin/mainmenu/init.lua b/builtin/mainmenu/init.lua
index 7c6af7d27..da4c3ccef 100644
--- a/builtin/mainmenu/init.lua
+++ b/builtin/mainmenu/init.lua
@@ -27,12 +27,12 @@ local basepath = core.get_builtin_path()
 defaulttexturedir = core.get_texturepath_share() .. DIR_DELIM .. "base" ..
 					DIR_DELIM .. "pack" .. DIR_DELIM
 
-dofile(basepath .. DIR_DELIM .. "common" .. DIR_DELIM .. "async_event.lua")
-dofile(basepath .. DIR_DELIM .. "common" .. DIR_DELIM .. "filterlist.lua")
-dofile(basepath .. DIR_DELIM .. "fstk" .. DIR_DELIM .. "buttonbar.lua")
-dofile(basepath .. DIR_DELIM .. "fstk" .. DIR_DELIM .. "dialog.lua")
-dofile(basepath .. DIR_DELIM .. "fstk" .. DIR_DELIM .. "tabview.lua")
-dofile(basepath .. DIR_DELIM .. "fstk" .. DIR_DELIM .. "ui.lua")
+dofile(basepath .. "common" .. DIR_DELIM .. "async_event.lua")
+dofile(basepath .. "common" .. DIR_DELIM .. "filterlist.lua")
+dofile(basepath .. "fstk" .. DIR_DELIM .. "buttonbar.lua")
+dofile(basepath .. "fstk" .. DIR_DELIM .. "dialog.lua")
+dofile(basepath .. "fstk" .. DIR_DELIM .. "tabview.lua")
+dofile(basepath .. "fstk" .. DIR_DELIM .. "ui.lua")
 dofile(menupath .. DIR_DELIM .. "common.lua")
 dofile(menupath .. DIR_DELIM .. "gamemgr.lua")
 dofile(menupath .. DIR_DELIM .. "modmgr.lua")
diff --git a/builtin/profiler/init.lua b/builtin/profiler/init.lua
index 874950364..a0033d752 100644
--- a/builtin/profiler/init.lua
+++ b/builtin/profiler/init.lua
@@ -23,7 +23,7 @@ local function get_bool_default(name, default)
 	return val
 end
 
-local profiler_path = core.get_builtin_path()..DIR_DELIM.."profiler"..DIR_DELIM
+local profiler_path = core.get_builtin_path().."profiler"..DIR_DELIM
 local profiler = {}
 local sampler = assert(loadfile(profiler_path .. "sampling.lua"))(profiler)
 local instrumentation  = assert(loadfile(profiler_path .. "instrumentation.lua"))(profiler, sampler, get_bool_default)
diff --git a/clientmods/preview/example.lua b/clientmods/preview/example.lua
new file mode 100644
index 000000000..2f661c073
--- /dev/null
+++ b/clientmods/preview/example.lua
@@ -0,0 +1,2 @@
+print("Loaded example file!, loading more examples")
+dofile("preview:examples/first.lua")
diff --git a/clientmods/preview/examples/first.lua b/clientmods/preview/examples/first.lua
new file mode 100644
index 000000000..c24f461e6
--- /dev/null
+++ b/clientmods/preview/examples/first.lua
@@ -0,0 +1 @@
+print("loaded first.lua example file")
diff --git a/clientmods/preview/init.lua b/clientmods/preview/init.lua
index 809e4f017..150db1816 100644
--- a/clientmods/preview/init.lua
+++ b/clientmods/preview/init.lua
@@ -1,6 +1,7 @@
 local modname = core.get_current_modname() or "??"
 local modstorage = core.get_mod_storage()
 
+dofile("preview:example.lua")
 -- This is an example function to ensure it's working properly, should be removed before merge
 core.register_on_shutdown(function()
 	print("[PREVIEW] shutdown client")
diff --git a/src/client.cpp b/src/client.cpp
index 5681c3ddb..0f689a714 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -104,17 +104,17 @@ Client::Client(
 	m_script->setEnv(&m_env);
 }
 
-void Client::initMods()
+void Client::loadMods()
 {
-	m_script->loadMod(getBuiltinLuaPath() + DIR_DELIM "init.lua", BUILTIN_MOD_NAME);
+	// Load builtin
+	scanModIntoMemory(BUILTIN_MOD_NAME, getBuiltinLuaPath());
 
 	// If modding is not enabled, don't load mods, just builtin
 	if (!m_modding_enabled) {
 		return;
 	}
-
 	ClientModConfiguration modconf(getClientModsLuaPath());
-	std::vector<ModSpec> mods = modconf.getMods();
+	m_mods = modconf.getMods();
 	std::vector<ModSpec> unsatisfied_mods = modconf.getUnsatisfiedMods();
 	// complain about mods with unsatisfied dependencies
 	if (!modconf.isConsistent()) {
@@ -123,28 +123,52 @@ void Client::initMods()
 
 	// Print mods
 	infostream << "Client Loading mods: ";
-	for (std::vector<ModSpec>::const_iterator i = mods.begin();
-		i != mods.end(); ++i) {
-		infostream << (*i).name << " ";
-	}
-
+	for (const ModSpec &mod : m_mods)
+		infostream << mod.name << " ";
 	infostream << std::endl;
+
 	// Load and run "mod" scripts
-	for (std::vector<ModSpec>::const_iterator it = mods.begin();
-		it != mods.end(); ++it) {
-		const ModSpec &mod = *it;
+	for (const ModSpec &mod : m_mods) {
 		if (!string_allowed(mod.name, MODNAME_ALLOWED_CHARS)) {
 			throw ModError("Error loading mod \"" + mod.name +
 				"\": Mod name does not follow naming conventions: "
 					"Only characters [a-z0-9_] are allowed.");
 		}
-		std::string script_path = mod.path + DIR_DELIM + "init.lua";
-		infostream << "  [" << padStringRight(mod.name, 12) << "] [\""
-			<< script_path << "\"]" << std::endl;
-		m_script->loadMod(script_path, mod.name);
+		scanModIntoMemory(mod.name, mod.path);
+	}
+}
+
+void Client::scanModSubfolder(const std::string &mod_name, const std::string &mod_path,
+			std::string mod_subpath)
+{
+	std::string full_path = mod_path + DIR_DELIM + mod_subpath;
+	std::vector<fs::DirListNode> mod = fs::GetDirListing(full_path);
+	for (unsigned int j=0; j < mod.size(); j++){
+		std::string filename = mod[j].name;
+		if (mod[j].dir) {
+			scanModSubfolder(mod_name, mod_path, mod_subpath
+					+ filename + DIR_DELIM);
+			continue;
+		}
+		std::replace( mod_subpath.begin(), mod_subpath.end(), DIR_DELIM_CHAR, '/');
+		m_mod_files[mod_name + ":" + mod_subpath + filename] = full_path  + filename;
 	}
 }
 
+void Client::initMods()
+{
+	m_script->loadModFromMemory(BUILTIN_MOD_NAME);
+
+	// If modding is not enabled, don't load mods, just builtin
+	if (!m_modding_enabled) {
+		return;
+	}
+
+	// Load and run "mod" scripts
+	for (const ModSpec &mod : m_mods)
+		m_script->loadModFromMemory(mod.name);
+}
+
 const std::string &Client::getBuiltinLuaPath()
 {
 	static const std::string builtin_dir = porting::path_share + DIR_DELIM + "builtin";
@@ -1898,6 +1922,17 @@ scene::IAnimatedMesh* Client::getMesh(const std::string &filename)
 	return mesh;
 }
 
+const std::string* Client::getModFile(const std::string &filename)
+{
+	StringMap::const_iterator it = m_mod_files.find(filename);
+	if (it == m_mod_files.end()) {
+		errorstream << "Client::getModFile(): File not found: \"" << filename
+			<< "\"" << std::endl;
+		return NULL;
+	}
+	return &it->second;
+}
+
 bool Client::registerModStorage(ModMetadata *storage)
 {
 	if (m_mod_storages.find(storage->getModName()) != m_mod_storages.end()) {
diff --git a/src/client.h b/src/client.h
index ab9801d62..0255b2803 100644
--- a/src/client.h
+++ b/src/client.h
@@ -37,6 +37,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "mapnode.h"
 #include "tileanimation.h"
 #include "mesh_generator_thread.h"
+#include <fstream>
+#include "filesys.h"
 
 #define CLIENT_CHAT_MESSAGE_LIMIT_PER_10S 10.0f
 
@@ -273,6 +275,16 @@ public:
 	~Client();
 	DISABLE_CLASS_COPY(Client);
 
+	// Load local mods into memory
+	void loadMods();
+	void scanModSubfolder(const std::string &mod_name, const std::string &mod_path,
+				std::string mod_subpath);
+	inline void scanModIntoMemory(const std::string &mod_name, const std::string &mod_path)
+	{
+		scanModSubfolder(mod_name, mod_path, "");
+	}
+
+	// Initizle the mods
 	void initMods();
 
 	/*
@@ -492,6 +504,7 @@ public:
 	bool checkLocalPrivilege(const std::string &priv)
 	{ return checkPrivilege(priv); }
 	virtual scene::IAnimatedMesh* getMesh(const std::string &filename);
+	const std::string* getModFile(const std::string &filename);
 
 	virtual std::string getModStoragePath() const;
 	virtual bool registerModStorage(ModMetadata *meta);
@@ -672,6 +685,8 @@ private:
 	// Storage for mesh data for creating multiple instances of the same mesh
 	StringMap m_mesh_data;
 
+	StringMap m_mod_files;
+
 	// own state
 	LocalClientState m_state;
 
@@ -684,6 +699,7 @@ private:
 	bool m_modding_enabled;
 	std::unordered_map<std::string, ModMetadata *> m_mod_storages;
 	float m_mod_storage_save_timer = 10.0f;
+	std::vector<ModSpec> m_mods;
 	GameUIFlags *m_game_ui_flags;
 
 	bool m_shutdown = false;
diff --git a/src/game.cpp b/src/game.cpp
index 4c903cc70..841b2d7ee 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -2121,6 +2121,7 @@ bool Game::connectToServer(const std::string &playername,
 
 		fps_control.last_time = RenderingEngine::get_timer_time();
 
+		client->loadMods();
 		client->initMods();
 
 		while (RenderingEngine::run()) {
diff --git a/src/script/common/c_internal.cpp b/src/script/common/c_internal.cpp
index b349f9dd1..0b388e383 100644
--- a/src/script/common/c_internal.cpp
+++ b/src/script/common/c_internal.cpp
@@ -24,37 +24,9 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 std::string script_get_backtrace(lua_State *L)
 {
-	std::string s;
-	lua_getglobal(L, "debug");
-	if(lua_istable(L, -1)){
-		lua_getfield(L, -1, "traceback");
-		if(lua_isfunction(L, -1)) {
-			lua_call(L, 0, 1);
-			if(lua_isstring(L, -1)){
-				s = lua_tostring(L, -1);
-			}
-		}
-		lua_pop(L, 1);
-	}
-	lua_pop(L, 1);
-	return s;
-}
-
-int script_error_handler(lua_State *L) {
-	lua_getglobal(L, "debug");
-	if (!lua_istable(L, -1)) {
-		lua_pop(L, 1);
-		return 1;
-	}
-	lua_getfield(L, -1, "traceback");
-	if (!lua_isfunction(L, -1)) {
-		lua_pop(L, 2);
-		return 1;
-	}
-	lua_pushvalue(L, 1);
-	lua_pushinteger(L, 2);
-	lua_call(L, 2, 1);
-	return 1;
+	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE);
+	lua_call(L, 0, 1);
+	return luaL_checkstring(L, -1);
 }
 
 int script_exception_wrapper(lua_State *L, lua_CFunction f)
diff --git a/src/script/common/c_internal.h b/src/script/common/c_internal.h
index fc59b0e2e..b77f0a7c3 100644
--- a/src/script/common/c_internal.h
+++ b/src/script/common/c_internal.h
@@ -53,11 +53,11 @@ extern "C" {
 #define CUSTOM_RIDX_SCRIPTAPI           (CUSTOM_RIDX_BASE)
 #define CUSTOM_RIDX_GLOBALS_BACKUP      (CUSTOM_RIDX_BASE + 1)
 #define CUSTOM_RIDX_CURRENT_MOD_NAME    (CUSTOM_RIDX_BASE + 2)
-#define CUSTOM_RIDX_ERROR_HANDLER       (CUSTOM_RIDX_BASE + 3)
+#define CUSTOM_RIDX_BACKTRACE           (CUSTOM_RIDX_BASE + 3)
 
 // Pushes the error handler onto the stack and returns its index
 #define PUSH_ERROR_HANDLER(L) \
-	(lua_rawgeti((L), LUA_REGISTRYINDEX, CUSTOM_RIDX_ERROR_HANDLER), lua_gettop((L)))
+	(lua_rawgeti((L), LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE), lua_gettop((L)))
 
 #define PCALL_RESL(L, RES) do {                         \
 	int result_ = (RES);                                \
diff --git a/src/script/cpp_api/s_base.cpp b/src/script/cpp_api/s_base.cpp
index aaf26a9c3..6bea8230b 100644
--- a/src/script/cpp_api/s_base.cpp
+++ b/src/script/cpp_api/s_base.cpp
@@ -89,8 +89,10 @@ ScriptApiBase::ScriptApiBase()
 	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
 
 	// Add and save an error handler
-	lua_pushcfunction(m_luastack, script_error_handler);
-	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_ERROR_HANDLER);
+	lua_getglobal(m_luastack, "debug");
+	lua_getfield(m_luastack, -1, "traceback");
+	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE);
+	lua_pop(m_luastack, 1); // pop debug
 
 	// If we are using LuaJIT add a C++ wrapper function to catch
 	// exceptions thrown in Lua -> C++ calls
@@ -158,6 +160,35 @@ void ScriptApiBase::loadScript(const std::string &script_path)
 	lua_pop(L, 1); // Pop error handler
 }
 
+#ifndef SERVER
+void ScriptApiBase::loadModFromMemory(const std::string &mod_name)
+{
+	ModNameStorer mod_name_storer(getStack(), mod_name);
+
+	const std::string *init_filename = getClient()->getModFile(mod_name + ":init.lua");
+	const std::string display_filename = mod_name + ":init.lua";
+	if(init_filename == NULL)
+		throw ModError("Mod:\"" + mod_name + "\" lacks init.lua");
+
+	verbosestream << "Loading and running script " << display_filename << std::endl;
+
+	lua_State *L = getStack();
+
+	int error_handler = PUSH_ERROR_HANDLER(L);
+
+	bool ok = ScriptApiSecurity::safeLoadFile(L, init_filename->c_str(), display_filename.c_str());
+	if (ok)
+		ok = !lua_pcall(L, 0, 0, error_handler);
+	if (!ok) {
+		std::string error_msg = luaL_checkstring(L, -1);
+		lua_pop(L, 2); // Pop error message and error handler
+		throw ModError("Failed to load and run mod \"" +
+				mod_name + "\":\n" + error_msg);
+	}
+	lua_pop(L, 1); // Pop error handler
+}
+#endif
+
 // Push the list of callbacks (a lua table).
 // Then push nargs arguments.
 // Then call this function, which
diff --git a/src/script/cpp_api/s_base.h b/src/script/cpp_api/s_base.h
index 38ee9901b..28fefdd37 100644
--- a/src/script/cpp_api/s_base.h
+++ b/src/script/cpp_api/s_base.h
@@ -54,6 +54,12 @@ extern "C" {
 #define setOriginFromTable(index) \
 	setOriginFromTableRaw(index, __FUNCTION__)
 
+enum class ScriptingType: u8 {
+	Client,
+	Server,
+	MainMenu
+};
+
 class Server;
 #ifndef SERVER
 class Client;
@@ -73,6 +79,10 @@ public:
 	void loadMod(const std::string &script_path, const std::string &mod_name);
 	void loadScript(const std::string &script_path);
 
+#ifndef SERVER
+	void loadModFromMemory(const std::string &mod_name);
+#endif
+
 	void runCallbacksRaw(int nargs,
 		RunCallbacksMode mode, const char *fxn);
 
@@ -82,6 +92,8 @@ public:
 
 	IGameDef *getGameDef() { return m_gamedef; }
 	Server* getServer();
+	void setType(ScriptingType type) { m_type = type; }
+	ScriptingType getType() { return m_type; }
 #ifndef SERVER
 	Client* getClient();
 #endif
@@ -133,6 +145,7 @@ private:
 	IGameDef       *m_gamedef = nullptr;
 	Environment    *m_environment = nullptr;
 	GUIEngine      *m_guiengine = nullptr;
+	ScriptingType  m_type;
 };
 
 #endif /* S_BASE_H_ */
diff --git a/src/script/cpp_api/s_security.cpp b/src/script/cpp_api/s_security.cpp
index 5ad7947d5..761597701 100644
--- a/src/script/cpp_api/s_security.cpp
+++ b/src/script/cpp_api/s_security.cpp
@@ -22,6 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "filesys.h"
 #include "porting.h"
 #include "server.h"
+#include "client.h"
 #include "settings.h"
 
 #include <cerrno>
@@ -140,8 +141,18 @@ void ScriptApiSecurity::initializeSecurity()
 
 	lua_State *L = getStack();
 
+	// Backup globals to the registry
+	lua_getglobal(L, "_G");
+	lua_rawseti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_GLOBALS_BACKUP);
 
-	int old_globals = backupGlobals(L);
+	// Replace the global environment with an empty one
+	int thread = getThread(L);
+	createEmptyEnv(L);
+	setLuaEnv(L, thread);
+
+	// Get old globals
+	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_GLOBALS_BACKUP);
+	int old_globals = lua_gettop(L);
 
 
 	// Copy safe base functions
@@ -274,80 +285,83 @@ void ScriptApiSecurity::initializeSecurityClient()
 	m_secure = true;
 
 	lua_State *L = getStack();
+	int thread = getThread(L);
 
-
-	int old_globals = backupGlobals(L);
-
+	// create an empty environment
+	createEmptyEnv(L);
 
 	// Copy safe base functions
 	lua_getglobal(L, "_G");
+	lua_getfield(L, -2, "_G");
 	copy_safe(L, whitelist, sizeof(whitelist));
 
 	// And replace unsafe ones
 	SECURE_API(g, dofile);
+	SECURE_API(g, load);
+	SECURE_API(g, loadfile);
 	SECURE_API(g, loadstring);
 	SECURE_API(g, require);
-	lua_pop(L, 1);
+	lua_pop(L, 2);
 
 
 
 	// Copy safe OS functions
-	lua_getfield(L, old_globals, "os");
+	lua_getglobal(L, "os");
 	lua_newtable(L);
 	copy_safe(L, os_whitelist, sizeof(os_whitelist));
-	lua_setglobal(L, "os");
+	lua_setfield(L, -3, "os");
 	lua_pop(L, 1);  // Pop old OS
 
 
 	// Copy safe debug functions
-	lua_getfield(L, old_globals, "debug");
+	lua_getglobal(L, "debug");
 	lua_newtable(L);
 	copy_safe(L, debug_whitelist, sizeof(debug_whitelist));
-	lua_setglobal(L, "debug");
+	lua_setfield(L, -3, "debug");
 	lua_pop(L, 1);  // Pop old debug
 
 #if USE_LUAJIT
 	// Copy safe jit functions, if they exist
-	lua_getfield(L, -1, "jit");
-	if (!lua_isnil(L, -1)) {
-		lua_newtable(L);
-		copy_safe(L, jit_whitelist, sizeof(jit_whitelist));
-		lua_setglobal(L, "jit");
-	}
+	lua_getglobal(L, "jit");
+	lua_newtable(L);
+	copy_safe(L, jit_whitelist, sizeof(jit_whitelist));
+	lua_setfield(L, -3, "jit");
 	lua_pop(L, 1);  // Pop old jit
 #endif
 
-	lua_pop(L, 1); // Pop globals_backup
+	// Set the environment to the one we created earlier
+	setLuaEnv(L, thread);
 }
 
-int ScriptApiSecurity::backupGlobals(lua_State *L)
+int ScriptApiSecurity::getThread(lua_State *L)
 {
-	// Backup globals to the registry
-	lua_getglobal(L, "_G");
-	lua_rawseti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_GLOBALS_BACKUP);
-
-	// Replace the global environment with an empty one
 #if LUA_VERSION_NUM <= 501
 	int is_main = lua_pushthread(L);  // Push the main thread
 	FATAL_ERROR_IF(!is_main, "Security: ScriptApi's Lua state "
 		"isn't the main Lua thread!");
+	return lua_gettop(L);
 #endif
+	return 0;
+}
+
+void ScriptApiSecurity::createEmptyEnv(lua_State *L)
+{
 	lua_newtable(L);  // Create new environment
 	lua_pushvalue(L, -1);
-	lua_setfield(L, -2, "_G");  // Set _G of new environment
+	lua_setfield(L, -2, "_G");  // Create the _G loop
+}
+
+void ScriptApiSecurity::setLuaEnv(lua_State *L, int thread)
+{
 #if LUA_VERSION_NUM >= 502  // Lua >= 5.2
 	// Set the global environment
 	lua_rawseti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS);
 #else  // Lua <= 5.1
 	// Set the environment of the main thread
-	FATAL_ERROR_IF(!lua_setfenv(L, -2), "Security: Unable to set "
+	FATAL_ERROR_IF(!lua_setfenv(L, thread), "Security: Unable to set "
 		"environment of the main Lua thread!");
 	lua_pop(L, 1);  // Pop thread
 #endif
-
-	// Get old globals
-	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_GLOBALS_BACKUP);
-	return lua_gettop(L);
 }
 
 bool ScriptApiSecurity::isSecure(lua_State *L)
@@ -367,11 +381,13 @@ bool ScriptApiSecurity::isSecure(lua_State *L)
 	}
 
 
-bool ScriptApiSecurity::safeLoadFile(lua_State *L, const char *path)
+bool ScriptApiSecurity::safeLoadFile(lua_State *L, const char *path, const char *display_name)
 {
 	FILE *fp;
 	char *chunk_name;
-	if (path == NULL) {
+	if (!display_name)
+		display_name = path;
+	if (!path) {
 		fp = stdin;
 		chunk_name = const_cast<char *>("=stdin");
 	} else {
@@ -380,10 +396,10 @@ bool ScriptApiSecurity::safeLoadFile(lua_State *L, const char *path)
 			lua_pushfstring(L, "%s: %s", path, strerror(errno));
 			return false;
 		}
-		chunk_name = new char[strlen(path) + 2];
+		chunk_name = new char[strlen(display_name) + 2];
 		chunk_name[0] = '@';
 		chunk_name[1] = '\0';
-		strcat(chunk_name, path);
+		strcat(chunk_name, display_name);
 	}
 
 	size_t start = 0;
@@ -626,8 +642,29 @@ int ScriptApiSecurity::sl_g_load(lua_State *L)
 
 int ScriptApiSecurity::sl_g_loadfile(lua_State *L)
 {
-	const char *path = NULL;
+#ifndef SERVER
+	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
+	ScriptApiBase *script = (ScriptApiBase *) lua_touserdata(L, -1);
+	lua_pop(L, 1);
 
+	if (script->getType() == ScriptingType::Client) {
+		std:: string display_path = lua_tostring(L, 1);
+		const std::string *path = script->getClient()->getModFile(display_path);
+		if (!path) {
+			std::string error_msg = "Coudln't find script called:" + display_path;
+			lua_pushnil(L);
+			lua_pushstring(L, error_msg.c_str());
+			return 2;
+		}
+		if (!safeLoadFile(L, path->c_str(), display_path.c_str())) {
+			lua_pushnil(L);
+			lua_insert(L, -2);
+			return 2;
+		}
+		return 1;
+	}
+#endif
+	const char *path = NULL;
 	if (lua_isstring(L, 1)) {
 		path = lua_tostring(L, 1);
 		CHECK_SECURE_PATH_INTERNAL(L, path, false, NULL);
diff --git a/src/script/cpp_api/s_security.h b/src/script/cpp_api/s_security.h
index f0eef00bb..059dccef1 100644
--- a/src/script/cpp_api/s_security.h
+++ b/src/script/cpp_api/s_security.h
@@ -41,14 +41,18 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 class ScriptApiSecurity : virtual public ScriptApiBase
 {
 public:
-	int backupGlobals(lua_State *L);
+	int getThread(lua_State *L);
+	// creates an empty Lua environment
+	void createEmptyEnv(lua_State *L);
+	// sets the enviroment to the table thats on top of the stack
+	void setLuaEnv(lua_State *L, int thread);
 	// Sets up security on the ScriptApi's Lua state
 	void initializeSecurity();
 	void initializeSecurityClient();
 	// Checks if the Lua state has been secured
 	static bool isSecure(lua_State *L);
 	// Loads a file as Lua code safely (doesn't allow bytecode).
-	static bool safeLoadFile(lua_State *L, const char *path);
+	static bool safeLoadFile(lua_State *L, const char *path, const char *display_name = NULL);
 	// Checks if mods are allowed to read (and optionally write) to the path
 	static bool checkPath(lua_State *L, const char *path, bool write_required,
 			bool *write_allowed=NULL);
diff --git a/src/script/lua_api/l_client.cpp b/src/script/lua_api/l_client.cpp
index 84eafd3f0..1077d5f2d 100644
--- a/src/script/lua_api/l_client.cpp
+++ b/src/script/lua_api/l_client.cpp
@@ -341,6 +341,14 @@ int ModApiClient::l_get_privilege_list(lua_State *L)
 	}
 	return 1;
 }
+
+// get_builtin_path()
+int ModApiClient::l_get_builtin_path(lua_State *L)
+{
+	lua_pushstring(L, BUILTIN_MOD_NAME ":");
+	return 1;
+}
+
 void ModApiClient::Initialize(lua_State *L, int top)
 {
 	API_FCT(get_current_modname);
@@ -366,4 +374,5 @@ void ModApiClient::Initialize(lua_State *L, int top)
 	API_FCT(get_node_def);
 	API_FCT(take_screenshot);
 	API_FCT(get_privilege_list);
+	API_FCT(get_builtin_path);
 }
diff --git a/src/script/lua_api/l_client.h b/src/script/lua_api/l_client.h
index 2f0c2e3f8..7472915f5 100644
--- a/src/script/lua_api/l_client.h
+++ b/src/script/lua_api/l_client.h
@@ -95,6 +95,9 @@ private:
 	// get_privilege_list()
 	static int l_get_privilege_list(lua_State *L);
 
+	// get_builtin_path()
+	static int l_get_builtin_path(lua_State *L);
+
 public:
 	static void Initialize(lua_State *L, int top);
 };
diff --git a/src/script/lua_api/l_util.cpp b/src/script/lua_api/l_util.cpp
index 3cf19f024..c68f64a64 100644
--- a/src/script/lua_api/l_util.cpp
+++ b/src/script/lua_api/l_util.cpp
@@ -246,7 +246,7 @@ int ModApiUtil::l_get_builtin_path(lua_State *L)
 {
 	NO_MAP_LOCK_REQUIRED;
 
-	std::string path = porting::path_share + DIR_DELIM + "builtin";
+	std::string path = porting::path_share + DIR_DELIM + "builtin" + DIR_DELIM;
 	lua_pushstring(L, path.c_str());
 
 	return 1;
@@ -470,8 +470,6 @@ void ModApiUtil::InitializeClient(lua_State *L, int top)
 
 	API_FCT(is_yes);
 
-	API_FCT(get_builtin_path);
-
 	API_FCT(compress);
 	API_FCT(decompress);
 
diff --git a/src/script/scripting_client.cpp b/src/script/scripting_client.cpp
index da289e564..904f735f3 100644
--- a/src/script/scripting_client.cpp
+++ b/src/script/scripting_client.cpp
@@ -36,6 +36,7 @@ ClientScripting::ClientScripting(Client *client):
 	ScriptApiBase()
 {
 	setGameDef(client);
+	setType(ScriptingType::Client);
 
 	SCRIPTAPI_PRECHECKHEADER
 
@@ -58,6 +59,9 @@ ClientScripting::ClientScripting(Client *client):
 	lua_pushstring(L, "client");
 	lua_setglobal(L, "INIT");
 
+	lua_pushstring(L, "/");
+	lua_setglobal(L, "DIR_DELIM");
+
 	infostream << "SCRIPTAPI: Initialized client game modules" << std::endl;
 }
 
diff --git a/src/script/scripting_mainmenu.cpp b/src/script/scripting_mainmenu.cpp
index 48957b472..e2f735927 100644
--- a/src/script/scripting_mainmenu.cpp
+++ b/src/script/scripting_mainmenu.cpp
@@ -36,6 +36,7 @@ extern "C" {
 MainMenuScripting::MainMenuScripting(GUIEngine* guiengine)
 {
 	setGuiEngine(guiengine);
+	setType(ScriptingType::MainMenu);
 
 	SCRIPTAPI_PRECHECKHEADER
 
diff --git a/src/script/scripting_server.cpp b/src/script/scripting_server.cpp
index cd01b0773..51e13f04d 100644
--- a/src/script/scripting_server.cpp
+++ b/src/script/scripting_server.cpp
@@ -50,6 +50,7 @@ extern "C" {
 ServerScripting::ServerScripting(Server* server)
 {
 	setGameDef(server);
+	setType(ScriptingType::Server);
 
 	// setEnv(env) is called by ScriptApiEnv::initializeEnvironment()
 	// once the environment has been created