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//! Mid-level cryptographic operations used in the onion service protocol.
use tor_llcrypto::d::Sha3_256;
use tor_llcrypto::util::ct::CtByteArray;
use digest::Digest;
/// Compute the lightweight MAC function used in the onion service protocol.
///
/// (rend-spec-v3 section 0.3 `MAC`)
pub fn hs_mac(key: &[u8], msg: &[u8]) -> CtByteArray<32> {
// rend-spec-v3 says: "Instantiate H with SHA3-256... Instantiate MAC(key=k,
// message=m) with H(k_len | k | m), where k_len is htonll(len(k))."
let mut hasher = Sha3_256::new();
let klen = key.len() as u64;
hasher.update(klen.to_be_bytes());
hasher.update(key);
hasher.update(msg);
let a: [u8; 32] = hasher.finalize().into();
a.into()
}
#[cfg(test)]
mod test {
// @@ begin test lint list maintained by maint/add_warning @@
#![allow(clippy::bool_assert_comparison)]
#![allow(clippy::clone_on_copy)]
#![allow(clippy::dbg_macro)]
#![allow(clippy::print_stderr)]
#![allow(clippy::print_stdout)]
#![allow(clippy::single_char_pattern)]
#![allow(clippy::unwrap_used)]
#![allow(clippy::unchecked_duration_subtraction)]
//! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
use super::*;
use hex_literal::hex;
/// Helper: just call Sha3_256 and return the result as a CtByteArray.
fn d(s: &[u8]) -> CtByteArray<32> {
let a: [u8; 32] = Sha3_256::digest(s).into();
a.into()
}
#[test]
fn mac_from_definition() {
assert_eq!(hs_mac(b"", b""), d(&[0; 8]));
assert_eq!(
hs_mac(b"hello", b"world"),
d(b"\0\0\0\0\0\0\0\x05helloworld")
);
assert_eq!(
hs_mac(b"helloworl", b"d"),
d(b"\0\0\0\0\0\0\0\x09helloworld")
);
}
#[test]
fn mac_testvec() {
// From C Tor; originally generated in Python.
let msg = b"i am in a library somewhere using my computer";
let key = b"i'm from the past talking to the future.";
assert_eq!(
hs_mac(key, msg).as_ref(),
&hex!("753fba6d87d49497238a512a3772dd291e55f7d1cd332c9fb5c967c7a10a13ca")
);
}
}
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