fn x25519_diffie_hellman()

in aws-lc-rs/src/agreement.rs [763:791]

• 22 lines of code
• 4 McCabe index (conditional complexity)

fn x25519_diffie_hellman<'a>(
    buffer: &'a mut [u8; MAX_AGREEMENT_SECRET_LEN],
    priv_key: &LcPtr<EVP_PKEY>,
    peer_pub_key: &[u8],
) -> Result<&'a [u8], ()> {
    let mut pkey_ctx = priv_key.create_EVP_PKEY_CTX()?;

    if 1 != unsafe { EVP_PKEY_derive_init(*pkey_ctx.as_mut()) } {
        return Err(());
    }

    let mut pub_key = try_parse_x25519_public_key_bytes(peer_pub_key)?;

    if 1 != unsafe { EVP_PKEY_derive_set_peer(*pkey_ctx.as_mut(), *pub_key.as_mut()) } {
        return Err(());
    }

    let mut out_key_len = buffer.len();

    if 1 != indicator_check!(unsafe {
        EVP_PKEY_derive(*pkey_ctx.as_mut(), buffer.as_mut_ptr(), &mut out_key_len)
    }) {
        return Err(());
    }

    debug_assert!(out_key_len == AlgorithmID::X25519.pub_key_len());

    Ok(&buffer[0..AlgorithmID::X25519.pub_key_len()])
}