Grcov report - ops.rs

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//! Mid-level cryptographic operations used in the onion service protocol.

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use tor_llcrypto::d::Sha3_256;

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use tor_llcrypto::util::ct::CtByteArray;

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use digest::Digest;

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/// The length of the MAC returned by [`hs_mac`].

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pub const HS_MAC_LEN: usize = 32;

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/// Compute the lightweight MAC function used in the onion service protocol.

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///

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/// (See rend-spec-v3 section 0.3 `MAC`.)

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///

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/// This is not a great MAC; KMAC wasn't defined at the time that the HSv3

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/// design was written. Please don't use this MAC in new protocols.

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pub fn hs_mac(key: &[u8], msg: &[u8]) -> CtByteArray<HS_MAC_LEN> {

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866

    // rend-spec-v3 says: "Instantiate H with SHA3-256... Instantiate MAC(key=k,

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    // message=m) with H(k_len | k | m), where k_len is htonll(len(k))."

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866

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    let mut hasher = Sha3_256::new();

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    let klen = key.len() as u64;

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    hasher.update(klen.to_be_bytes());

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    hasher.update(key);

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    hasher.update(msg);

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    let a: [u8; HS_MAC_LEN] = hasher.finalize().into();

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    a.into()

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866

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/// Reference to a slice of bytes usable to compute the [`hs_mac`] function.

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#[derive(Copy, Clone, derive_more::From)]

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pub struct HsMacKey<'a>(&'a [u8]);

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impl<'a> tor_llcrypto::traits::ShortMac<HS_MAC_LEN> for HsMacKey<'a> {

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    fn mac(&self, input: &[u8]) -> CtByteArray<HS_MAC_LEN> {

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        hs_mac(self.0, input)

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    fn validate(&self, input: &[u8], mac: &[u8; HS_MAC_LEN]) -> subtle::Choice {

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        use subtle::ConstantTimeEq;

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        let m = hs_mac(self.0, input);

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        m.as_ref().ct_eq(mac)

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#[cfg(test)]

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mod test {

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    // @@ begin test lint list maintained by maint/add_warning @@

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    #![allow(clippy::bool_assert_comparison)]

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    #![allow(clippy::clone_on_copy)]

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    #![allow(clippy::dbg_macro)]

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    #![allow(clippy::mixed_attributes_style)]

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    #![allow(clippy::print_stderr)]

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    #![allow(clippy::print_stdout)]

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    #![allow(clippy::single_char_pattern)]

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    #![allow(clippy::unwrap_used)]

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    #![allow(clippy::unchecked_duration_subtraction)]

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    #![allow(clippy::useless_vec)]

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    #![allow(clippy::needless_pass_by_value)]

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    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

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    use super::*;

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    use hex_literal::hex;

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    /// Helper: just call Sha3_256 and return the result as a CtByteArray.

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    fn d(s: &[u8]) -> CtByteArray<32> {

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        let a: [u8; 32] = Sha3_256::digest(s).into();

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        a.into()

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    #[test]

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    fn mac_from_definition() {

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        assert_eq!(hs_mac(b"", b""), d(&[0; 8]));

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        assert_eq!(

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            hs_mac(b"hello", b"world"),

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            d(b"\0\0\0\0\0\0\0\x05helloworld")

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);

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        assert_eq!(

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            hs_mac(b"helloworl", b"d"),

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            d(b"\0\0\0\0\0\0\0\x09helloworld")

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);

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    #[test]

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    fn mac_testvec() {

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        // From C Tor; originally generated in Python.

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        let msg = b"i am in a library somewhere using my computer";

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        let key = b"i'm from the past talking to the future.";

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        assert_eq!(

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            hs_mac(key, msg).as_ref(),

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            &hex!("753fba6d87d49497238a512a3772dd291e55f7d1cd332c9fb5c967c7a10a13ca")

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);

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