rust-libp2p/protocols/secio/src/exchange/impl_ring.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
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//! Implementation of the key agreement process using the `ring` library.

use futures::{future, prelude::*};
use ring::agreement as ring_agreement;
use ring::rand as ring_rand;
use untrusted::Input as UntrustedInput;
use {KeyAgreement, SecioError};

impl Into<&'static ring_agreement::Algorithm> for KeyAgreement {
    #[inline]
    fn into(self) -> &'static ring_agreement::Algorithm {
        match self {
            KeyAgreement::EcdhP256 => &ring_agreement::ECDH_P256,
            KeyAgreement::EcdhP384 => &ring_agreement::ECDH_P384,
        }
    }
}

/// Opaque private key type.
pub type AgreementPrivateKey = ring_agreement::EphemeralPrivateKey;

/// Generates a new key pair as part of the exchange.
///
/// Returns the opaque private key and the corresponding public key.
pub fn generate_agreement(algorithm: KeyAgreement) -> impl Future<Item = (AgreementPrivateKey, Vec<u8>), Error = SecioError> {
    let rng = ring_rand::SystemRandom::new();

    match ring_agreement::EphemeralPrivateKey::generate(algorithm.into(), &rng) {
        Ok(tmp_priv_key) => {
            let mut tmp_pub_key: Vec<u8> = (0 .. tmp_priv_key.public_key_len()).map(|_| 0).collect();
            tmp_priv_key.compute_public_key(&mut tmp_pub_key).unwrap();
            future::ok((tmp_priv_key, tmp_pub_key))
        },
        Err(_) => {
            debug!("failed to generate ECDH key");
            future::err(SecioError::EphemeralKeyGenerationFailed)
        },
    }
}

/// Finish the agreement. On success, returns the shared key that both remote agreed upon.
pub fn agree(algorithm: KeyAgreement, my_private_key: AgreementPrivateKey, other_public_key: &[u8], _out_size: usize)
    -> impl Future<Item = Vec<u8>, Error = SecioError>
{
    ring_agreement::agree_ephemeral(my_private_key, algorithm.into(),
                                    UntrustedInput::from(other_public_key),
                                    SecioError::SecretGenerationFailed,
                                    |key_material| Ok(key_material.to_vec()))
        .into_future()
}