snow 0.7.2

A pure-rust implementation of the Noise Protocol Framework
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# Snow

[![Crates.io](https://img.shields.io/crates/v/snow.svg)](https://crates.io/crates/snow)
[![Docs.rs](https://docs.rs/snow/badge.svg)](https://docs.rs/snow)
[![Build Status](https://travis-ci.org/mcginty/snow.svg?branch=master)](https://travis-ci.org/mcginty/snow)
[![dependency status](https://deps.rs/repo/github/mcginty/snow/status.svg)](https://deps.rs/repo/github/mcginty/snow)

![totally official snow logo](https://i.imgur.com/gFgvo49.jpg?1)

An implementation of Trevor Perrin's [Noise Protocol](https://noiseprotocol.org/) that
is designed to be Hard To Fuck Upâ„¢.

🔥 **Warning** 🔥 This library has not received any formal audit.

## What's it look like?
See `examples/simple.rs` for a more complete TCP client/server example.

```rust
let mut noise = snow::Builder::new("Noise_NN_25519_ChaChaPoly_BLAKE2s".parse()?)
                    .build_initiator()?;
 
let mut buf = [0u8; 65535];
 
// write first handshake message
noise.write_message(&[], &mut buf)?;
 
// receive response message
let incoming = receive_message_from_the_mysterious_ether();
noise.read_message(&incoming, &mut buf)?;
 
// complete handshake, and transition the state machine into transport mode
let mut noise = noise.into_transport_mode()?;
```

See the full documentation at [https://docs.rs/snow](https://docs.rs/snow).


## Implemented

Snow is currently tracking against [Noise spec revision 34](https://noiseprotocol.org/noise_rev34.html).

However, a not all features have been implemented yet (pull requests welcome):

- [ ] [The `fallback` modifier](https://noiseprotocol.org/noise_rev34.html#the-fallback-modifier)

## Crypto
Cryptographic providers are swappable through `Builder::with_resolver()`, but by default
it chooses select, artisanal pure-Rust implementations (see `Cargo.toml` for a quick
overview).

### Other Providers

#### ring

[ring](https://github.com/briansmith/ring) is a crypto library based off of BoringSSL
and is significantly faster than most of the pure-Rust implementations.

If you enable the `ring-resolver` feature, Snow will include a `resolvers::ring` module
as well as a `RingAcceleratedResolver` available to be used with
`Builder::with_resolver()`.

If you enable the `ring-accelerated` feature, Snow will default to choosing `ring`'s
crypto implementations when available.

#### libsodium
[libsodium](https://libsodium.org/) is a fork of NaCl focused on improved usability
and regular maintenance.

##### Compatibility caveat
libsodium [blacklists a set of low-order points](https://github.com/jedisct1/libsodium/blob/master/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L20)
that it deems unsafe because they would output an all-zeroes result.

Noise [does not validate Curve25519 points](https://moderncrypto.org/mail-archive/noise/2017/000971.html),
so if another Noise implementation provides an all-zero (or another low-order) public
key for some reason (be it testing, or a real life foot-shot), if you use the libsodium
backend of snow, it will error in a way that's not fully compatible with the
specification.


### Resolver primitives supported

|            | default | ring | libsodium |
|-----------:|:-------:|:----:|:---------:|
| CSPRNG     | ✔       | ✔    | ✔         |
| 25519      | ✔       | ✔    | ✔         |
| 448        |         |      |           |
| AESGCM     | ✔       | ✔    |           |
| ChaChaPoly | ✔       | ✔    | ✔         |
| SHA256     | ✔       | ✔    | ✔         |
| SHA512     | ✔       | ✔    |           |
| BLAKE2s    | ✔       |      |           |
| BLAKE2b    | ✔       |      |           |