GHSA-q7pg-9pr4-mrp2 httpsig-rs: HMAC verification is vulnerable to timing attack

• crates.io httpsig: < 0.0.19 → fixed in 0.0.19

Summary HMAC signature comparison is not timing-safe and is vulnerable to timing attacks. Details `SharedKey::sign()` returns a `Vec` which has a non-constant-time equality implementation. `Hmac::finalize()` returns a constant-time wrapper (`CtOutput`) which was discarded. Alternatively, `Hmac` has a constant-time `verify()` method. The problem reported here is due to the following lines in `SharedKey::sign()` of the previous code: ```rust let mut mac = HmacSha256::new_from_slice(key).unwrap(); mac.update(data); Ok(mac.finalize().into_bytes().to_vec()) ``` and the merged update changes the third line to directly verify with `verify_slice`. Impact Anyone who uses HS256 signature verification is vulnerably to Timing Attack that allows the attacker to forge a signature.