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fix(LuaMod): Resolve stack indexing and sanitize params in StaticConstructObject #1245

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fix(LuaMod): Resolve stack indexing and sanitize params in StaticConstructObject #1245

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f3c1484
fix(security): sanitize StaticConstructObject parameters
500Byte May 7, 2026
605a26f
fix(LuaMod): fix StaticConstructObject stack indexing (Issue #1149)
500Byte May 7, 2026
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76 changes: 48 additions & 28 deletions UE4SS/src/Mod/LuaMod.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1893,76 +1893,96 @@ No overload found for function 'StaticConstructObject'.

))"};

lua_State* L = lua.get_lua_state();
int num_args = lua_gettop(L);

// For now, we're assuming that if there's userdata, that userdata is of the correct underlying type
if (!lua.is_userdata())
if (num_args < 1 || !lua.is_userdata(1))
{
lua.throw_error(error_overload_not_found);
}
Unreal::UClass* param_class = lua.get_userdata<LuaType::UClass>().get_remote_cpp_object();
Unreal::UClass* param_class = lua.get_userdata<LuaType::UClass>(1, true).get_remote_cpp_object();

if (!lua.is_userdata())
if (num_args < 2 || !lua.is_userdata(2))
{
lua.throw_error(error_overload_not_found);
}
Unreal::UObject* param_outer = lua.get_userdata<LuaType::UObject>().get_remote_cpp_object();
Unreal::UObject* param_outer = lua.get_userdata<LuaType::UObject>(2, true).get_remote_cpp_object();

Unreal::FName param_name;
if (lua.is_userdata())
{
param_name = lua.get_userdata<LuaType::FName>().get_local_cpp_object();
}
else if (lua.is_integer())
{
param_name = Unreal::FName(lua.get_integer());
}
else
if (num_args >= 3)
{
param_name = Unreal::FName(static_cast<int64_t>(0));
if (lua.is_userdata(3))
{
param_name = lua.get_userdata<LuaType::FName>(3, true).get_local_cpp_object();
}
else if (lua.is_integer(3))
{
param_name = Unreal::FName(lua_tointeger(L, 3));
}
else
{
param_name = Unreal::FName(static_cast<int64_t>(0));
}
}

Unreal::EObjectFlags param_set_flags{};
if (lua.is_integer())
if (num_args >= 4 && lua.is_integer(4))
{
param_set_flags = static_cast<Unreal::EObjectFlags>(lua.get_integer());
param_set_flags = static_cast<Unreal::EObjectFlags>(lua_tointeger(L, 4));
}

Unreal::EInternalObjectFlags param_internal_set_flags{};
if (lua.is_integer())
if (num_args >= 5 && lua.is_integer(5))
{
param_internal_set_flags = static_cast<Unreal::EInternalObjectFlags>(lua.get_integer());
param_internal_set_flags = static_cast<Unreal::EInternalObjectFlags>(lua_tointeger(L, 5));
}

// The rest are all optional parameters
bool param_copy_transients_from_class_defaults{};
if (lua.is_bool())
if (num_args >= 6 && lua.is_bool(6))
{
param_copy_transients_from_class_defaults = lua.get_bool();
param_copy_transients_from_class_defaults = lua_toboolean(L, 6);
}

bool param_assume_template_is_archetype{};
if (lua.is_bool())
if (num_args >= 7 && lua.is_bool(7))
{
param_assume_template_is_archetype = lua.get_bool();
param_assume_template_is_archetype = lua_toboolean(L, 7);
}

Unreal::UObject* param_template{};
if (lua.is_userdata())
if (num_args >= 8 && lua.is_userdata(8))
{
param_template = lua.get_userdata<LuaType::UObject>().get_remote_cpp_object();
param_template = lua.get_userdata<LuaType::UObject>(8, true).get_remote_cpp_object();
}

// Change this to userdata if support for 'FObjectInstancingGraph' is ever added
void* param_instance_graph{};
if (lua.is_integer())
if (num_args >= 9)
{
param_instance_graph = reinterpret_cast<void*>(static_cast<uintptr_t>(lua.get_integer()));
if (lua_islightuserdata(L, 9))
{
param_instance_graph = lua_touserdata(L, 9);
}
else if (!lua_isnil(L, 9))
{
lua.throw_error("StaticConstructObject: InstanceGraph must be lightuserdata or nil");
}
}

// Change this to userdata if support for 'UPackage' is ever added
void* param_external_package{};
if (lua.is_integer())
if (num_args >= 10)
{
param_external_package = reinterpret_cast<void*>(static_cast<uintptr_t>(lua.get_integer()));
if (lua_islightuserdata(L, 10))
{
param_external_package = lua_touserdata(L, 10);
}
else if (!lua_isnil(L, 10))
{
lua.throw_error("StaticConstructObject: ExternalPackage must be lightuserdata or nil");
}
}

// void* param_subobject_overrides{};
Expand Down