Salted Challenge Response Authentication Mechanism (SCRAM)

This implementation currently provides a client for the SCRAM-SHA-256 mechanism according to RFC5802 and RFC7677. It doesn't support channel-binding.

Read the documentation.

Limitations

There is no server-side implementation of the SCRAM mechanism and no SHA-1 support. If you like to contribute or maintain them I appreciate that.

Usage

A typical usage scenario is shown below. For a detailed explanation of the methods please consider their documentation. In productive code you should replace the unwrapping by proper error handling.

At first the user and the password must be supplied using either of the methods ClientFirst::new or ClientFirst::with_rng. These methods return a SCRAM state you can use to compute the first client message.

The server and the client exchange four messages using the SCRAM mechanism. There is a rust type for each one of them. Calling the methods client_first, handle_server_first, client_final and handle_server_final on the different types advances the SCRAM handshake step by step. Computing client messages never fails but processing server messages can result in failure.

use scram::ClientFirst;

// This function represents your I/O implementation.
fn send_and_receive(message: &str) -> String {
    unimplemented!()
}

// Create a SCRAM state from the credentials.
let scram = ClientFirst::new("user", "password", None).unwrap();

// Get the client message and reassign the SCRAM state.
let (scram, client_first) = scram.client_first();

// Send the client first message and receive the servers reply.
let server_first = send_and_receive(&client_first);

// Process the reply and again reassign the SCRAM state. You can add error handling to
// abort the authentication attempt.
let scram = scram.handle_server_first(&server_first).unwrap();

// Get the client final message and reassign the SCRAM state.
let (scram, client_final) = scram.client_final();

// Send the client final message and receive the servers reply.
let server_final = send_and_receive(&client_final);

// Process the last message. Any error returned means that the authentication attempt
// wasn't successful.
let () = scram.handle_server_final(&server_final).unwrap();