MesaPy is a memory-safe Python implementation based on PyPy. In addition to PyPy's distinct features -- speed (thanks to the JIT compiler), memory usage, compatibility and stackless (massive concurrency), MesaPy mainly focuses on improving its security and memory safety. On top of the enhancements, we also bring MesaPy into Intel SGX to write memory-safe applications running in the trusted execution environment.

We achieve the memory-safety promise through various methods: hardening RPython's type system (RPython is the language for writing PyPy), modifying PyPy/RPython's libraries, and verifying the RPython's libraries as well as its translator/JIT backend. Overall, there are four most notable security features of MesaPy:

• Memory safety: To provide a memory-safe runtime, MesaPy replaces external libraries written in C, which could introduce memory issues, with Rust, a memory-safe programming language. This guarantees the memory safety across all libraries including those written in Python, but also external libraries.

• Security hardening: PyPy is implemented with RPython, a statically-typed language with translation and support framework. We also enhanced memory-safety of RPython through hardening RPython's type system, i.e., the RPython typer. For example, we improve RPython's list with runtime index check to avoid arbitrarily list read/write during PyPy's implementation.

• Formal verification: Some code in RPython's libraries and its translator/JIT backend are still written in C, which may contain potential memory bugs. To prove the memory safety of RPython, we aim to formally verify its libraries and backend written in C using state-of-the-art verification tools.

• SGX support (WIP): With the memory safety of MesaPy, we also port it to Intel SGX, which is a trusted execution environment to provide integrity and confidentiality guarantees to security-sensitive computation. Developers now can easily use MesaPy to implement SGX applications without worrying about memory issues.

See README.cn.md for Chinese translation.