Hax

hax is a tool for high assurance translations that translates a large subset of Rust into formal languages such as F* or Coq. This extends the scope of the hacspec project, which was previously a DSL embedded in Rust, to a usable tool for verifying Rust programs.

So what is hacspec now?

hacspec is the functional subset of Rust that can be used, together with a hacspec standard library, to write succinct, executable, and verifiable specifications in Rust. These specifications can be translated into formal languages with hax.

Usage

Hax is a cargo subcommand. The command cargo hax accepts the following subcommands:

• into (cargo hax into BACKEND): translate a Rust crate to the backend BACKEND (e.g. fstar, coq).
• json (cargo hax json): extract the typed AST of your crate as a JSON file.

Note:

• BACKEND can be fstar, coq or easycrypt. The list of supported backends can be displayed running cargo hax into --help.
• The subcommand cargo hax takes options, list them with cargo hax --help.
• The subcommand cargo hax into takes also options, list them with cargo hax into --help.

Installation

Nix

This should work on Linux, MacOS and Windows.

Prerequisites: Nix package manager (with flakes enabled)

• Either using the Determinate Nix Installer, with the following bash one-liner:

  curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install
  

• or following those steps.

• Run hax on a crate to get F*/Coq/…:
  • cd path/to/your/crate
  • nix run github:hacspec/hacspec-v2 -- into fstar
    will create fst modules in the directory hax/extraction/fstar.
    Note: replace fstar by your backend of choice
• Install the tool: nix profile install github:hacspec/hacspec-v2
  • then run cargo hax --help anywhere

Using Docker

1. Clone this repo: git clone git@github.com:hacspec/hacspec-v2.git && cd hacspec-v2
2. Build the docker image: docker build -f .docker/Dockerfile . -t hacspec-v2
3. Get a shell: docker run -it --rm -v /some/dir/with/a/crate:/work hacspec-v2 bash
4. You can now run cargo-hax --help (notice here we use cargo-hax instead of cargo hax)

Manual installation

1. Make sure to have the following installed on your system:

• opam (opam switch create 4.14.1)
• rustup
• nodejs
• jq

1. Clone this repo: git clone git@github.com:hacspec/hacspec-v2.git && cd hacspec-v2
2. Run the setup.sh script: ./setup.sh.
3. Run cargo-hax --help

Examples

There’s a set of examples that show what hax can do for you. Please check out the examples directory

Hacking on Hax

Edit the sources (Nix)

Just clone & cd into the repo, then run nix develop .. You can also just use direnv, with editor integration.

Structure of this repository

• rust-frontend/: Rust library that hooks in the rust compiler and extract its internal typed abstract syntax tree THIR as JSON.
• engine/: the simplication and elaboration engine that translate programs from the Rust language to various backends (see engine/backends/).
• cli/: the hax subcommand for Cargo.

Recompiling

You can use the .utils/rebuild.sh script (which is available automatically as the command rebuild when using the Nix devshell):

• rebuild: rebuild the Rust then the OCaml part;
• rebuild TARGET: rebuild the TARGET part (TARGET is either rust or ocaml).

Publications & Other material

• 📕 Tech report
• 📕 HACSpec: A gateway to high-assurance cryptography
• 📕 Hax - Enabling High Assurance Cryptographic Software at RustVerify’24
• 📕 Original hacspec paper

Secondary literature, using hacspec:

• 📕 A Verified Pipeline from a Specification Language to Optimized, Safe Rust at CoqPL’22
• 📕 Last yard
• 📕 A formal security analysis of Blockchain voting at CoqPL’24
• 📕 Specifying Smart Contract with Hax and ConCert at CoqPL’24

Contributing

Before starting any work please join the Zulip chat, start a discussion on Github, or file an issue to discuss your contribution.