Jędrzej Stuczyński
80 lines
2.3 KiB
Rust
80 lines
2.3 KiB
Rust
// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
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// SPDX-License-Identifier: Apache-2.0
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use hmac::{
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digest::{crypto_common::BlockSizeUser, CtOutput, Digest, Output},
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Mac, SimpleHmac,
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};
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pub use hmac;
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// TODO: We should probably change it to use some sealed trait to allow for both `Hmac` and `SimpleHmac`
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pub type HmacOutput<D> = CtOutput<SimpleHmac<D>>;
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/// Compute keyed hmac
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pub fn compute_keyed_hmac<D>(key: &[u8], data: &[u8]) -> HmacOutput<D>
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where
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D: Digest + BlockSizeUser,
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{
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let mut hmac = SimpleHmac::<D>::new_from_slice(key)
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.expect("HMAC was instantiated with a key of an invalid size!");
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hmac.update(data);
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hmac.finalize()
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}
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/// Compute keyed hmac and performs constant time equality check with the provided tag value.
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pub fn recompute_keyed_hmac_and_verify_tag<D>(key: &[u8], data: &[u8], tag: &[u8]) -> bool
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where
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D: Digest + BlockSizeUser,
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{
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let mut hmac = SimpleHmac::<D>::new_from_slice(key)
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.expect("HMAC was instantiated with a key of an invalid size!");
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hmac.update(data);
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let tag_arr = Output::<D>::from_slice(tag);
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// note, under the hood ct_eq is called
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hmac.verify(tag_arr).is_ok()
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}
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/// Verifies tag of an hmac output.
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pub fn verify_tag<D>(tag: &[u8], out: HmacOutput<D>) -> bool
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where
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D: Digest + BlockSizeUser,
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{
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if tag.len() != <D as Digest>::output_size() {
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return false;
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}
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let tag_arr = Output::<D>::from_slice(tag);
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out == tag_arr.into()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::blake3;
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// TODO: is it somehow possible to make the test not depend on blake3 specifically and
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// make it more generic?
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#[test]
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fn verifying_tags_work_using_both_methods_with_blake3() {
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let key = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
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let msg = b"Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam sodales ultricies scelerisque.";
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// expected
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let output = compute_keyed_hmac::<blake3::Hasher>(&key, msg);
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let output_tag = output.into_bytes().to_vec();
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assert!(recompute_keyed_hmac_and_verify_tag::<blake3::Hasher>(
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&key,
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msg,
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&output_tag
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));
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assert!(verify_tag::<blake3::Hasher>(
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&output_tag,
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compute_keyed_hmac::<blake3::Hasher>(&key, msg)
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));
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}
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}
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