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use std::cmp::Ordering;
use crate::crypto;
use crate::crypto::mem;
use crate::packet;
use crate::Packet;
/// Holds an MDC packet.
///
/// A modification detection code packet. This packet appears after a
/// SEIP packet. See [Section 5.13.1 of RFC 9580] for details.
///
/// [Section 5.13.1 of RFC 9580]: https://www.rfc-editor.org/rfc/rfc9580.html#section-5.13.1
///
/// # A note on equality
///
/// Two `MDC` packets are considered equal if their serialized form is
/// equal. This excludes the computed digest.
#[derive(Clone, Debug)]
pub struct MDC {
/// CTB packet header fields.
pub(crate) common: packet::Common,
/// Our SHA-1 hash.
computed_digest: [u8; 20],
/// A 20-octet SHA-1 hash of the preceding plaintext data.
digest: [u8; 20],
}
assert_send_and_sync!(MDC);
impl PartialEq for MDC {
fn eq(&self, other: &MDC) -> bool {
self.common == other.common
&& self.digest == other.digest
}
}
impl Eq for MDC {}
impl std::hash::Hash for MDC {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
std::hash::Hash::hash(&self.common, state);
std::hash::Hash::hash(&self.digest, state);
}
}
impl MDC {
/// Creates an MDC packet.
pub fn new(digest: [u8; 20], computed_digest: [u8; 20]) -> Self {
MDC {
common: Default::default(),
computed_digest,
digest,
}
}
/// Gets the packet's hash value.
pub fn digest(&self) -> &[u8] {
&self.digest[..]
}
/// Gets the computed hash value.
pub fn computed_digest(&self) -> &[u8] {
&self.computed_digest[..]
}
/// Returns whether the data protected by the MDC is valid.
pub fn valid(&self) -> bool {
if self.digest == [ 0; 20 ] {
// If the computed_digest and digest are uninitialized, then
// return false.
false
} else {
mem::secure_cmp(&self.computed_digest, &self.digest) == Ordering::Equal
}
}
}
impl From<MDC> for Packet {
fn from(s: MDC) -> Self {
#[allow(deprecated)]
Packet::MDC(s)
}
}
impl From<[u8; 20]> for MDC {
fn from(digest: [u8; 20]) -> Self {
MDC {
common: Default::default(),
// All 0s.
computed_digest: Default::default(),
digest,
}
}
}
impl From<crypto::hash::Context> for MDC {
fn from(mut hash: crypto::hash::Context) -> Self {
let mut value : [u8; 20] = Default::default();
let _ = hash.digest(&mut value[..]);
value.into()
}
}