tweak: safe undump support

Author: blattersturm

lua.h

@@ -60,6 +60,8 @@
 
 typedef struct lua_State lua_State;
 
+typedef int (*lua_UndumpHook) (const char* p, size_t n);
+
 
 /*
 ** basic types

lundump.c

@@ -24,6 +24,7 @@
 #include "lundump.h"
 #include "lzio.h"
 
+lua_UndumpHook pUndumpHook = NULL;
 
 #if defined(LUA_NO_BYTECODE)
 LClosure *luaU_undump(lua_State *L, ZIO *Z, const char *name) {
@@ -367,6 +368,8 @@ LClosure *luaU_undump(lua_State *L, ZIO *Z, const char *name) {
     S.name = name;
   S.L = L;
   S.Z = Z;
+  if (!pUndumpHook || !pUndumpHook(Z->p, Z->n))
+    error(&S, "forbidden");
   checkHeader(&S);
   cl = luaF_newLclosure(L, loadByte(&S));
   setclLvalue2s(L, L->top, cl);

lundump.h

@@ -26,6 +26,16 @@
 
 #define LUAC_FORMAT	0	/* this is the official format */
 
+extern
+#if defined(IS_FXSERVER)
+#if defined(_WIN32)
+__declspec(dllexport)
+#else
+__attribute__((visibility("default")))
+#endif
+#endif
+lua_UndumpHook pUndumpHook;
+
 /* load one chunk; from lundump.c */
 LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, const char* name);