luau/fuzz/proto.cpp

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// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "src/libfuzzer/libfuzzer_macro.h"
#include "luau.pb.h"
#include "Luau/TypeInfer.h"
#include "Luau/BuiltinDefinitions.h"
#include "Luau/ModuleResolver.h"
#include "Luau/ModuleResolver.h"
#include "Luau/Compiler.h"
#include "Luau/Linter.h"
#include "Luau/BytecodeBuilder.h"
#include "Luau/Common.h"
#include "Luau/ToString.h"
#include "Luau/Transpiler.h"
#include "lua.h"
#include "lualib.h"
#include <chrono>
// Select components to fuzz
const bool kFuzzCompiler = true;
const bool kFuzzLinter = true;
const bool kFuzzTypeck = true;
const bool kFuzzVM = true;
const bool kFuzzTypes = true;
const bool kFuzzTranspile = true;
static_assert(!(kFuzzVM && !kFuzzCompiler), "VM requires the compiler!");
std::string protoprint(const luau::StatBlock& stat, bool types);
LUAU_FASTINT(LuauTypeInferRecursionLimit)
LUAU_FASTINT(LuauTypeInferTypePackLoopLimit)
LUAU_FASTINT(LuauCheckRecursionLimit)
LUAU_FASTINT(LuauTableTypeMaximumStringifierLength)
LUAU_FASTINT(LuauTypeInferIterationLimit)
LUAU_FASTINT(LuauTarjanChildLimit)
std::chrono::milliseconds kInterruptTimeout(10);
std::chrono::time_point<std::chrono::system_clock> interruptDeadline;
size_t kHeapLimit = 512 * 1024 * 1024;
size_t heapSize = 0;
void interrupt(lua_State* L, int gc)
{
if (gc >= 0)
return;
if (std::chrono::system_clock::now() > interruptDeadline)
{
lua_checkstack(L, 1);
luaL_error(L, "execution timed out");
}
}
void* allocate(lua_State* L, void* ud, void* ptr, size_t osize, size_t nsize)
{
if (nsize == 0)
{
heapSize -= osize;
free(ptr);
return NULL;
}
else
{
if (heapSize - osize + nsize > kHeapLimit)
return NULL;
heapSize -= osize;
heapSize += nsize;
return realloc(ptr, nsize);
}
}
lua_State* createGlobalState()
{
lua_State* L = lua_newstate(allocate, NULL);
lua_callbacks(L)->interrupt = interrupt;
luaL_openlibs(L);
luaL_sandbox(L);
return L;
}
int registerTypes(Luau::TypeChecker& env)
{
using namespace Luau;
using std::nullopt;
Luau::registerBuiltinTypes(env);
TypeArena& arena = env.globalTypes;
// Vector3 stub
TypeId vector3MetaType = arena.addType(TableTypeVar{});
TypeId vector3InstanceType = arena.addType(ClassTypeVar{"Vector3", {}, nullopt, vector3MetaType, {}, {}});
getMutable<ClassTypeVar>(vector3InstanceType)->props = {
{"X", {env.numberType}},
{"Y", {env.numberType}},
{"Z", {env.numberType}},
};
getMutable<TableTypeVar>(vector3MetaType)->props = {
{"__add", {makeFunction(arena, nullopt, {vector3InstanceType, vector3InstanceType}, {vector3InstanceType})}},
};
env.globalScope->exportedTypeBindings["Vector3"] = TypeFun{{}, vector3InstanceType};
// Instance stub
TypeId instanceType = arena.addType(ClassTypeVar{"Instance", {}, nullopt, nullopt, {}, {}});
getMutable<ClassTypeVar>(instanceType)->props = {
{"Name", {env.stringType}},
};
env.globalScope->exportedTypeBindings["Instance"] = TypeFun{{}, instanceType};
// Part stub
TypeId partType = arena.addType(ClassTypeVar{"Part", {}, instanceType, nullopt, {}, {}});
getMutable<ClassTypeVar>(partType)->props = {
{"Position", {vector3InstanceType}},
};
env.globalScope->exportedTypeBindings["Part"] = TypeFun{{}, partType};
for (const auto& [_, fun] : env.globalScope->exportedTypeBindings)
persist(fun.type);
return 0;
}
static std::string debugsource;
DEFINE_PROTO_FUZZER(const luau::StatBlock& message)
{
FInt::LuauTypeInferRecursionLimit.value = 100;
FInt::LuauTypeInferTypePackLoopLimit.value = 100;
FInt::LuauCheckRecursionLimit.value = 100;
FInt::LuauTypeInferIterationLimit.value = 1000;
FInt::LuauTarjanChildLimit.value = 1000;
FInt::LuauTableTypeMaximumStringifierLength.value = 100;
for (Luau::FValue<bool>* flag = Luau::FValue<bool>::list; flag; flag = flag->next)
if (strncmp(flag->name, "Luau", 4) == 0)
flag->value = true;
Luau::Allocator allocator;
Luau::AstNameTable names(allocator);
std::string source = protoprint(message, kFuzzTypes);
// stash source in a global for easier crash dump debugging
debugsource = source;
Luau::ParseResult parseResult = Luau::Parser::parse(source.c_str(), source.size(), names, allocator);
// "static" here is to accelerate fuzzing process by only creating and populating the type environment once
static Luau::NullModuleResolver moduleResolver;
static Luau::InternalErrorReporter iceHandler;
static Luau::TypeChecker sharedEnv(&moduleResolver, &iceHandler);
static int once = registerTypes(sharedEnv);
(void)once;
static int once2 = (Luau::freeze(sharedEnv.globalTypes), 0);
(void)once2;
iceHandler.onInternalError = [](const char* error) {
printf("ICE: %s\n", error);
LUAU_ASSERT(!"ICE");
};
static bool debug = getenv("LUAU_DEBUG") != 0;
if (debug)
{
fprintf(stdout, "--\n%s\n", source.c_str());
fflush(stdout);
}
std::string bytecode;
// compile
if (kFuzzCompiler && parseResult.errors.empty())
{
Luau::CompileOptions compileOptions;
try
{
Luau::BytecodeBuilder bcb;
Luau::compileOrThrow(bcb, parseResult.root, names, compileOptions);
bytecode = bcb.getBytecode();
}
catch (const Luau::CompileError&)
{
// not all valid ASTs can be compiled due to limits on number of registers
}
}
// typecheck
if (kFuzzTypeck && parseResult.root)
{
Luau::SourceModule sourceModule;
sourceModule.root = parseResult.root;
sourceModule.mode = Luau::Mode::Nonstrict;
Luau::TypeChecker typeck(&moduleResolver, &iceHandler);
typeck.globalScope = sharedEnv.globalScope;
Luau::ModulePtr module = nullptr;
try
{
module = typeck.check(sourceModule, Luau::Mode::Nonstrict);
}
catch (std::exception&)
{
// This catches internal errors that the type checker currently (unfortunately) throws in some cases
}
// lint (note that we need access to types so we need to do this with typeck in scope)
if (kFuzzLinter)
{
Luau::LintOptions lintOptions = {~0u};
Luau::lint(parseResult.root, names, sharedEnv.globalScope, module.get(), lintOptions);
}
}
// validate sharedEnv post-typecheck; valuable for debugging some typeck crashes but slows fuzzing down
// note: it's important for typeck to be destroyed at this point!
if (kFuzzTypeck)
{
for (auto& p : sharedEnv.globalScope->bindings)
{
Luau::ToStringOptions opts;
opts.exhaustive = true;
opts.maxTableLength = 0;
opts.maxTypeLength = 0;
toString(p.second.typeId, opts); // toString walks the entire type, making sure ASAN catches access to destroyed type arenas
}
}
if (kFuzzTranspile && parseResult.root)
{
transpileWithTypes(*parseResult.root);
}
// run resulting bytecode
if (kFuzzVM && bytecode.size())
{
static lua_State* globalState = createGlobalState();
lua_State* L = lua_newthread(globalState);
luaL_sandboxthread(L);
if (luau_load(L, "=fuzz", bytecode.data(), bytecode.size(), 0) == 0)
{
interruptDeadline = std::chrono::system_clock::now() + kInterruptTimeout;
lua_resume(L, NULL, 0);
}
lua_pop(globalState, 1);
// we'd expect full GC to reclaim all memory allocated by the script
lua_gc(globalState, LUA_GCCOLLECT, 0);
LUAU_ASSERT(heapSize < 256 * 1024);
}
}