rustbearer-token

How to make an hexadecimal token from a ring::hmac::Key?

I want to generate an authentication token in Rust. I tried to generate a random key with ring::hmac, like so:

use ring::{hmac, rand};

let rng = rand::SystemRandom::new();
let key = hmac::Key::generate(hmac::HMAC_SHA256, &rng)?;

How can I then make an hexadecimal string out of key? Or is there a better way to generate an hexadecimal, secure token in Rust?

Solution

  • If you are creating the Key yourself you can use Key::new() instead of Key::generate, which allows for specifying the key_value explicitily:

    use ring::{digest, hmac, rand};

fn main() {
    let msg = "hello, world";

    let rng = rand::SystemRandom::new();
    let key_value: [u8; digest::SHA256_OUTPUT_LEN] = rand::generate(&rng).unwrap().expose();
    let hex = key_value.iter().map(|b| format!("{:02X}", b)).collect::<String>();
    println!("{}", hex);

    let s_key = hmac::Key::new(hmac::HMAC_SHA256, key_value.as_ref());
    let _tag = hmac::sign(&s_key, msg.as_bytes());
}

    Here is the link to the Playground.