From 4188c2164dd51f619736eca06bb1123277bd9644 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bitbucket@bruce-hill.com>
Date: Sat, 10 Feb 2018 16:48:58 -0800
Subject: [PATCH] Added slightly more error checking.

---
 limmutable.c | 28 ++++++++++++++++++++++------
 test.lua     |  8 ++++++++
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/limmutable.c b/limmutable.c
index 1bb7f42..1a85788 100644
--- a/limmutable.c
+++ b/limmutable.c
@@ -107,7 +107,7 @@ static int Lcreate_instance(lua_State *L)
         // Stack: [inst, buckets]
         lua_createtable(L, 1, 0);
         // Stack: [inst, buckets, bucket]
-        lua_pushlightuserdata(L, (void*)Lcreate_instance);
+        lua_pushlightuserdata(L, (void*)Lcreate_instance); // Shared bucket metatable
         lua_gettable(L, LUA_REGISTRYINDEX);
         // Stack: [inst, buckets, bucket, {'__mode'='k'}]
         lua_setmetatable(L, -2);
@@ -223,13 +223,17 @@ static int Lindex(lua_State *L)
     // Stack: [mt, indices]
     lua_pushvalue(L, 2);
     // Stack: [mt, indices, k]
-    lua_rawget(L, -2);
+    lua_gettable(L, -2);
     // Stack: [mt, indices, i]
     if (! lua_isnil(L, -1)) {
         // Stack: [mt, indices, i]
         lua_getfield(L, -3, "__instances");
         // Stack: [mt, indices, i, buckets]
-        lua_rawgeti(L, -1, *((lua_Integer*)lua_touserdata(L, 1)));
+        lua_Integer* hash_address = (lua_Integer*)lua_touserdata(L, 1);
+        if (! hash_address) {
+            luaL_error(L, "invalid type");
+        }
+        lua_rawgeti(L, -1, *hash_address);
         // Stack: [mt, indices, i, buckets, bucket]
         lua_pushvalue(L, 1);
         // Stack: [mt, indices, i, buckets, bucket, inst_udata]
@@ -268,7 +272,11 @@ static int Ltostring(lua_State *L)
     
     lua_getfield(L, -1, "__instances");
     // Stack: [mt, buckets]
-    lua_rawgeti(L, -1, *((lua_Integer*)lua_touserdata(L, 1)));
+    lua_Integer* hash_address = (lua_Integer*)lua_touserdata(L, 1);
+    if (! hash_address) {
+        luaL_error(L, "invalid type");
+    }
+    lua_rawgeti(L, -1, *hash_address);
     // Stack: [mt, buckets, bucket]
     lua_pushvalue(L, 1);
     // Stack: [mt, buckets, bucket, inst_udata]
@@ -317,7 +325,11 @@ static int Lnexti(lua_State *L)
     // Stack: [mt]
     lua_getfield(L, -1, "__instances");
     // Stack: [mt, buckets]
-    lua_rawgeti(L, -1, *((lua_Integer*)lua_touserdata(L, 1)));
+    lua_Integer* hash_address = (lua_Integer*)lua_touserdata(L, 1);
+    if (! hash_address) {
+        luaL_error(L, "invalid type");
+    }
+    lua_rawgeti(L, -1, *hash_address);
     // Stack: [mt, buckets, bucket]
     lua_pushvalue(L, 1);
     // Stack: [mt, buckets, bucket, inst_udata]
@@ -357,7 +369,11 @@ static int Lnext(lua_State *L)
     // Stack: [mt]
     lua_getfield(L, -1, "__instances");
     // Stack: [mt, buckets]
-    lua_rawgeti(L, -1, *((lua_Integer*)lua_touserdata(L, 1)));
+    lua_Integer* hash_address = (lua_Integer*)lua_touserdata(L, 1);
+    if (! hash_address) {
+        luaL_error(L, "invalid type");
+    }
+    lua_rawgeti(L, -1, *hash_address);
     // Stack: [mt, buckets, bucket]
     lua_pushvalue(L, 1);
     // Stack: [mt, buckets, bucket, inst_udata]
diff --git a/test.lua b/test.lua
index c2c4f62..0b21c58 100644
--- a/test.lua
+++ b/test.lua
@@ -148,6 +148,14 @@ test("Testing similar class", function()
     assert(FooVec(1,1) ~= Vec(1,1))
 end)
 
+test("Testing spoofing", function()
+    local t = {99,100}
+    setmetatable(t, Vec)
+    assert(not pcall(function() return t.x end))
+    assert(not pcall(function() return Vec(88) end))
+    assert(not pcall(function() return Vec.__tostring(t) end))
+end)
+
 if num_errors == 0 then
     print(green.."All tests passed!"..reset)
 else