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use subtle::ConstantTimeEq;
use crate::constants::{CRYPTO_AUTH_BYTES, CRYPTO_AUTH_HMACSHA512256_BYTES, CRYPTO_AUTH_KEYBYTES};
use crate::error::Error;
use crate::sha512::Sha512;
use crate::types::*;
struct HmacSha512State {
octx: Sha512,
ictx: Sha512,
}
pub type Key = [u8; CRYPTO_AUTH_KEYBYTES];
pub type Mac = [u8; CRYPTO_AUTH_BYTES];
fn crypto_auth_hmacsha512256(output: &mut Mac, message: &[u8], key: &Key) {
let mut state = crypto_auth_hmacsha512256_init(key);
crypto_auth_hmacsha512256_update(&mut state, message);
crypto_auth_hmacsha512256_final(state, output);
}
fn crypto_auth_hmacsha512256_verify(mac: &Mac, input: &[u8], key: &Key) -> Result<(), Error> {
let mut computed_mac = Mac::default();
crypto_auth_hmacsha512256(&mut computed_mac, input, key);
if mac.ct_eq(&computed_mac).unwrap_u8() == 1 {
Ok(())
} else {
Err(dryoc_error!("authentication codes do not match"))
}
}
fn crypto_auth_hmacsha512256_init(key: &[u8]) -> HmacSha512State {
let mut pad = [0x36u8; 128];
let mut khash = [0u8; 64];
let keylen = key.len();
let key = if keylen > 128 {
Sha512::compute_into_bytes(&mut khash, key);
&khash
} else {
key
};
let mut ictx = Sha512::new();
for i in 0..keylen {
pad[i] ^= key[i]
}
ictx.update(&pad);
let mut octx = Sha512::new();
pad.fill(0x5c);
for i in 0..keylen {
pad[i] ^= key[i]
}
octx.update(&pad);
HmacSha512State { octx, ictx }
}
fn crypto_auth_hmacsha512256_update(state: &mut HmacSha512State, input: &[u8]) {
state.ictx.update(input)
}
fn crypto_auth_hmacsha512256_final(
mut state: HmacSha512State,
output: &mut [u8; CRYPTO_AUTH_HMACSHA512256_BYTES],
) {
let mut ihash = [0u8; 64];
state.ictx.finalize_into_bytes(&mut ihash);
state.octx.update(&ihash);
state.octx.finalize_into_bytes(&mut ihash);
output.copy_from_slice(&ihash[..CRYPTO_AUTH_HMACSHA512256_BYTES])
}
pub fn crypto_auth(mac: &mut Mac, message: &[u8], key: &Key) {
crypto_auth_hmacsha512256(mac, message, key)
}
pub fn crypto_auth_verify(mac: &Mac, input: &[u8], key: &Key) -> Result<(), Error> {
crypto_auth_hmacsha512256_verify(mac, input, key)
}
pub struct AuthState {
state: HmacSha512State,
}
pub fn crypto_auth_keygen() -> Key {
Key::gen()
}
pub fn crypto_auth_init(key: &Key) -> AuthState {
AuthState {
state: crypto_auth_hmacsha512256_init(key),
}
}
pub fn crypto_auth_update(state: &mut AuthState, input: &[u8]) {
crypto_auth_hmacsha512256_update(&mut state.state, input)
}
pub fn crypto_auth_final(state: AuthState, output: &mut [u8; CRYPTO_AUTH_BYTES]) {
crypto_auth_hmacsha512256_final(state.state, output)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_crypto_auth() {
use rand_core::{OsRng, RngCore};
use sodiumoxide::crypto::auth;
use sodiumoxide::crypto::auth::Key as SOKey;
use crate::rng::copy_randombytes;
for _ in 0..20 {
let mlen = (OsRng.next_u32() % 5000) as usize;
let mut message = vec![0u8; mlen];
copy_randombytes(&mut message);
let key = crypto_auth_keygen();
let so_tag =
auth::authenticate(&message, &SOKey::from_slice(&key).expect("key failed"));
let mut mac = Mac::new_byte_array();
crypto_auth(&mut mac, &message, &key);
assert_eq!(mac, so_tag.0);
crypto_auth_verify(&mac, &message, &key).expect("verify failed");
crypto_auth_verify(&mac, b"invalid message", &key)
.expect_err("verify should have failed");
}
}
}