chat-rs

A client-server chat platform implemented in rust.

This crate contains the library implementing the chat-rs protocol. For the server and client implementations and further details, see the server, client_term and client_gui directories respectively.

The Protocol

Communication between the client and the server is done using Messages.
Not to be confused with a chat message, a BCMP message includes a header with information about the message contents, and then optionally additional message contents as needed.

Headers

A message's header consists of 3 bytes - first comes the discriminant, and then two (big endian) bytes describing the length of the following contents. Messages with no contents have a length of 0.

The discriminant distinguishes between different types of messages. For a comprehensive list of message types, see the Msg enum in this crate's source.

Message Contents

A message can optionally contain a UTF-8 encoded string. Nicked messages (as in, messages that come from the server and contain nickname information) first store the nickname, then a null byte, and then the rest of the message.

Encrypted Protocol Extension

For security and coherency reasons, encrypted messages are encoded in a slightly different way.

First, the message is encoded as normal into bytes. Then, encrypted using AES256-GCM with a random nonce. The data sent is 2 bytes containing the length of the ciphertext, followed by 12 bytes containing the nonce, followed by the ciphertext.

This crate has not been audited, and is written for recreational purposes only. Do not rely on chat-rs for confidentiality.