Refactor trusted mod checking code

2 files changed, 42 insertions, 5 deletions

diff --git a/src/script/cpp_api/s_security.cpp b/src/script/cpp_api/s_security.cpp
index 11c277839..ccd1214e3 100644
--- a/src/script/cpp_api/s_security.cpp
+++ b/src/script/cpp_api/s_security.cpp
@@ -27,6 +27,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include <cerrno>
 #include <string>
+#include <algorithm>
 #include <iostream>
 
 
@@ -604,6 +605,38 @@ bool ScriptApiSecurity::checkPath(lua_State *L, const char *path,
 	return false;
 }
 
+bool ScriptApiSecurity::checkWhitelisted(lua_State *L, const std::string &setting)
+{
+	assert(str_starts_with(setting, "secure."));
+
+	// We have to make sure that this function is being called directly by
+	// a mod, otherwise a malicious mod could override this function and
+	// steal its return value.
+	lua_Debug info;
+
+	// Make sure there's only one item below this function on the stack...
+	if (lua_getstack(L, 2, &info))
+		return false;
+	FATAL_ERROR_IF(!lua_getstack(L, 1, &info), "lua_getstack() failed");
+	FATAL_ERROR_IF(!lua_getinfo(L, "S", &info), "lua_getinfo() failed");
+
+	// ...and that that item is the main file scope.
+	if (strcmp(info.what, "main") != 0)
+		return false;
+
+	// Mod must be listed in secure.http_mods or secure.trusted_mods
+	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_CURRENT_MOD_NAME);
+	if (!lua_isstring(L, -1))
+		return false;
+	std::string mod_name = readParam<std::string>(L, -1);
+
+	std::string value = g_settings->get(setting);
+	value.erase(std::remove(value.begin(), value.end(), ' '), value.end());
+	auto mod_list = str_split(value, ',');
+
+	return CONTAINS(mod_list, mod_name);
+}
+
 
 int ScriptApiSecurity::sl_g_dofile(lua_State *L)
 {
diff --git a/src/script/cpp_api/s_security.h b/src/script/cpp_api/s_security.h
index 73e763548..619bf824f 100644
--- a/src/script/cpp_api/s_security.h
+++ b/src/script/cpp_api/s_security.h
@@ -40,11 +40,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 class ScriptApiSecurity : virtual public ScriptApiBase
 {
 public:
-	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();
@@ -57,8 +52,17 @@ public:
 	// 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);
+	// Check if mod is whitelisted in the given setting
+	// This additionally checks that the mod's main file scope is executing.
+	static bool checkWhitelisted(lua_State *L, const std::string &setting);
 
 private:
+	int getThread(lua_State *L);
+	// sets the enviroment to the table thats on top of the stack
+	void setLuaEnv(lua_State *L, int thread);
+	// creates an empty Lua environment
+	void createEmptyEnv(lua_State *L);
+
 	// Syntax: "sl_" <Library name or 'g' (global)> '_' <Function name>
 	// (sl stands for Secure Lua)