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

2 files changed, 5 insertions, 33 deletions

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);                                \