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use serde::{Deserialize, Serialize};
#[cfg(feature = "native_crypto")]
use subtle::ConstantTimeEq;
use zbus::zvariant::Type;
use zeroize::{Zeroize, ZeroizeOnDrop};
// There is no constructor to avoid performing sanity checks, e.g. length.
/// A message authentication code. It provides constant-time comparison when
/// compared against another mac or against a slice of bytes.
#[derive(Deserialize, Serialize, Type, Clone, Zeroize, ZeroizeOnDrop)]
pub struct Mac(#[serde(with = "serde_bytes")] Vec<u8>);
impl std::fmt::Debug for Mac {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "Mac([REDACTED])")
}
impl Mac {
pub(crate) const fn new(inner: Vec<u8>) -> Self {
Self(inner)
/// Constant-time comparison against a slice of bytes.
fn verify_slice(&self, other: &[u8]) -> bool {
{
self.0.ct_eq(other).into()
#[cfg(feature = "openssl_crypto")]
openssl::memcmp::eq(&self.0, other)
// This is made private to prevent non-constant-time comparisons.
pub(crate) fn as_slice(&self) -> &[u8] {
self.0.as_slice()
impl PartialEq for Mac {
fn eq(&self, other: &Self) -> bool {
self.verify_slice(&other.0)
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn mac_debug_is_redacted() {
let mac = Mac::new(vec![1, 2, 3, 4]);
assert_eq!(format!("{:?}", mac), "Mac([REDACTED])");