mlspp-sys

AI DISCLAIMER: This project was initially generated by Claude "Opus 4.6" language model. The work were supervised heavily but no warranties express or implied etc etc.

Raw FFI bindings to Cisco mlspp, a C++ implementation of the Messaging Layer Security (MLS) protocol (RFC 9420).

MLS is an end-to-end encryption protocol designed for group messaging. It provides forward secrecy, post-compromise security, and efficient group key management for groups of any size.

Features

Build requirements

When the vendored feature is enabled (default), building this crate requires:

• A C++17 compiler (GCC 8+, Clang 7+, MSVC 2019+)
• CMake 3.16+
• OpenSSL development headers (or set OPENSSL_ROOT_DIR)

Installation

Add to your Cargo.toml:

[dependencies]
mlspp-sys = "0.3"

Usage

All functions are unsafe and follow C conventions. Here is a minimal example that creates a cipher suite and generates a signing key:

use mlspp_sys::*;
use std::ptr;

fn main() {
    unsafe {
        // Create a cipher suite (MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519 = 1)
        let cs = mlspp_cipher_suite_create(1);
        if cs.is_null() {
            let err = mlspp_last_error();
            panic!("failed to create cipher suite: {:?}", std::ffi::CStr::from_ptr(err));
        }

        // Generate a signature key pair
        let sig_priv = mlspp_signature_private_key_generate(cs);
        assert!(!sig_priv.is_null(), "key generation failed");

        // Clean up
        mlspp_signature_private_key_free(sig_priv);
        mlspp_cipher_suite_free(cs);
    }
}

Memory management

The API uses two patterns:

• Opaque handles (mlspp_state_t, mlspp_session_t, etc.) are heap-allocated pointers. Each has a corresponding _free function that must be called exactly once.
• Byte buffers (mlspp_bytes_t) are {data, len} pairs. Free them with mlspp_bytes_free. Do not call free() on the inner data pointer directly.

Error handling

Functions that can fail return NULL (for handles) or {NULL, 0} (for byte buffers). Call mlspp_last_error() to retrieve a thread-local error string. On success, mlspp_last_error() returns NULL.

API overview

The bindings expose two API levels:

• Low-level (State) — direct MLS group state management with full control over proposals, commits, and application data protection.
• High-level (Client / Session) — a simplified API that manages key generation and state transitions internally, suited for straightforward group messaging.

Safety

All functions are unsafe. Callers must ensure:

• Pointer arguments are non-null and point to valid, live objects
• Handles are not used after being freed
• Handles are not shared across threads without external synchronization

License

MIT