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use std::time::Instant;
use blake2::Blake2s;
use subtle::ConstantTimeEq;
use x25519_dalek::PublicKey;
use zerocopy::{AsBytes, ByteSlice, FromBytes, LayoutVerified};
const LABEL_MAC1: &[u8] = b"mac1----";
const LABEL_COOKIE: &[u8] = b"cookie--";
const SIZE_COOKIE: usize = 16;
const SIZE_MAC: usize = 16; // blake2s-mac128
macro_rules! HASH {
( $($input:expr),* ) => {{
use blake2::Digest;
let mut hsh = Blake2s::new();
$(
hsh.input($input);
)*
hsh.result()
}};
}
macro_rules! MAC {
( $key:expr, $($input:expr),* ) => {{
use blake2::VarBlake2s;
use digest::Input;
use digest::VariableOutput;
let mut tag = [0u8; SIZE_MAC];
let mut mac = VarBlake2s::new_keyed($key, SIZE_MAC);
$(
mac.input($input);
)*
mac.variable_result(|buf| tag.copy_from_slice(buf));
tag
}};
}
#[repr(C)]
#[derive(Copy, Clone, FromBytes, AsBytes)]
pub struct MacsFooter {
pub f_mac1: [u8; SIZE_MAC],
pub f_mac2: [u8; SIZE_MAC],
}
impl Default for MacsFooter {
fn default() -> Self {
Self {
f_mac1: [0u8; SIZE_MAC],
f_mac2: [0u8; SIZE_MAC],
}
}
}
struct Generator {
mac1_key: [u8; 32],
cookie_value: [u8; 16],
cookie_birth: Option<Instant>, // when was the cookie set?
}
impl Generator {
fn new(pk: PublicKey) -> Generator {
Generator {
mac1_key: HASH!(LABEL_MAC1, pk.as_bytes()).into(),
cookie_value: [0u8; SIZE_COOKIE],
cookie_birth: None,
}
}
fn mac1(&self, msg: &[u8]) -> [u8; SIZE_MAC] {
MAC!(&self.mac1_key, msg)
}
fn mac2(&self, msg: &[u8]) -> [u8; SIZE_MAC] {
MAC!(&self.cookie_value, msg)
}
pub fn set_cookie(&mut self, cookie: &[u8; SIZE_COOKIE]) {
self.cookie_birth = Some(Instant::now());
self.cookie_value = *cookie;
}
pub fn generate(&self, msg: &[u8]) -> MacsFooter {
MacsFooter {
f_mac1: self.mac1(msg),
f_mac2: self.mac2(msg),
}
}
}
struct Validator {}
impl Validator {}
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