PUC Rio Lua
LuaJIT
Tarantool

Lua C API tests

is a set of fuzzing tests for C implementations of Lua runtime (PUC Rio Lua and LuaJIT).

Building

git clone https://github.com/ligurio/lua-c-api-tests
cd lua-c-api-tests
git clone https://github.com/ligurio/lua-c-api-corpus
CC=clang CXX=clang++ cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DUSE_LUA=ON [-DUSE_LUAJIT=ON]
cmake --build build --parallel

CMake options:

• USE_LUA enables building PUC Rio Lua.
• USE_LUAJIT enables building LuaJIT.
• LUA_VERSION could be a Git branch, tag or commit. By default LUA_VERSION is master for PUC Rio Lua and v2.1 for LuaJIT.
• ENABLE_LUAJIT_RANDOM_RA enables randomness in a register allocation. Option is LuaJIT-specific.
• ENABLE_ASAN enables AddressSanitizer.
• ENABLE_UBSAN enables UndefinedBehaviorSanitizer.
• ENABLE_COV enables coverage instrumentation.
• ENABLE_LUA_ASSERT enables all assertions inside Lua source code.
• ENABLE_LUA_APICHECK enables consistency checks on the C API.
• OSS_FUZZ enables support of OSS Fuzz.
• ENABLE_BUILD_PROTOBUF enables building Protobuf library, otherwise system library is used.
• ENABLE_INTERNAL_TESTS enables internal tests.
• ENABLE_LAPI_TESTS enables Lua API tests.

Running

cmake --build build --target test
cd build && RUNS=100000 ctest -R luaL_gsub_test --verbose
<snipped>
1: Done 100000 runs in 5 second(s)

References

• Lua 5.4 Reference Manual: 4 – The Application Program Interface
• Lua 5.3 Reference Manual: 4 – The Application Program Interface
• Lua 5.2 Reference Manual: 4 – The Application Program Interface
• Lua 5.1 Reference Manual: 3 – The Application Program Interface

Known Issues

Fuzzing can find a wide variety of problems, but not all problems are considered bugs. Some problems are due to known limitations in the implementation. This section contains a list of such limitations in LuaJIT and PUC Rio Lua:

1. In LuaJIT, the build infrastructure includes a source code that contains memory leaks and other problems. For example, src/host/buildvm.c and src/host/minilua.c, these files are only used during the LuaJIT build process, and they are not a part of the LuaJIT itself. Memory leaks are suppressed in AddressSanitizer with a function __lsan_is_turned_off() that disallows leak checking for the program it is linked into.
2. In LuaJIT, a function lj_str_new() may read past a buffer end (so-called "dirty" read), and that's ok. Suppressed in AddressSanitizer with __attribute__((no_sanitize_address)).
3. In LuaJIT, bytecode input is unsafe; see LuaJIT#847 and LuaJIT FAQ. The string "mode" controls whether the chunk can be text or binary (that is, a precompiled chunk). It may be the string "b" (only binary chunks), "t" (only text chunks), or "bt" (both binary and text). The default is "bt". PUC Rio Lua and LuaJIT both have bytecode and Lua source code parsers. It is desired to test both parsers; however, the LuaJIT bytecode parser failed with the assertion: LuaJIT ASSERT lj_bcread.c:123: bcread_byte: buffer read overflow, so with LuaJIT only text mode is used, and therefore only the text parser is tested.
4. The debug library is defined as unsafe. There are tons of ways to produce a crash with it. This library provides the functionality of the debug interface to Lua programs. Several of its functions violate basic assumptions about Lua code and therefore can compromise otherwise secure code. See LuaJIT#1264 and Lua 5.4 Reference Manual. The debug functions are not a subject of testing, and these functions are used carefully.
5. In LuaJIT, there are a number of places with undefined behavior ("nonnull-attribute", "signed-integer-overflow", "bounds"). These problems remain unfixed and suppressed in UndefinedBehavior Sanitizer.
6. In LuaJIT, there is a minimal C declaration parser, and it is not a validating C parser: "The parser ought to return correct results for properly formed C declarations, but it may accept some invalid declarations, too (and return nonsense)".

License

Copyright (C) 2022-2025 Sergey Bronnikov, released under the ISC license. See a full Copyright Notice in the LICENSE file.