ssh-key: have PublicKey and its parts implment Hash

This change derives the Hash trait for PublicKey and it's constitutent
parts. Since Mpint implements its own PartialEq, an explicit Hash
implmenetation delegating to the backing byte vector is added.

A test verifying that a HashSet containing a public key can
indeed be created and queried is also added.

ssh-key/src/mpint.rs

@@ -4,6 +4,7 @@ use crate::{Error, Result};
 use alloc::vec::Vec;
 use core::fmt;
 use encoding::{CheckedSum, Decode, Encode, Reader, Writer};
+use core::hash::{Hash, Hasher};
 use subtle::{Choice, ConstantTimeEq};
 use zeroize::Zeroize;
 
@@ -114,6 +115,12 @@ impl PartialEq for Mpint {
     }
 }
 
+impl Hash for Mpint {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.inner.hash(state)
+    }
+}
+
 impl Decode for Mpint {
     type Error = Error;
 

ssh-key/src/public.rs

@@ -78,7 +78,7 @@ use std::{fs, path::Path};
 /// The serialization uses a binary encoding with binary formats like bincode
 /// and CBOR, and the OpenSSH string serialization when used with
 /// human-readable formats like JSON and TOML.
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct PublicKey {
     /// Key data.
     pub(crate) key_data: KeyData,

ssh-key/src/public/dsa.rs

@@ -6,7 +6,7 @@ use encoding::{CheckedSum, Decode, Encode, Reader, Writer};
 /// Digital Signature Algorithm (DSA) public key.
 ///
 /// Described in [FIPS 186-4 § 4.1](https://csrc.nist.gov/publications/detail/fips/186/4/final).
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct DsaPublicKey {
     /// Prime modulus.
     pub p: Mpint,

ssh-key/src/public/ecdsa.rs

@@ -20,7 +20,7 @@ pub type EcdsaNistP521PublicKey = sec1::EncodedPoint<U66>;
 /// `sec1` feature of this crate is enabled (which it is by default).
 ///
 /// Described in [FIPS 186-4](https://csrc.nist.gov/publications/detail/fips/186/4/final).
-#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub enum EcdsaPublicKey {
     /// NIST P-256 ECDSA public key.
     NistP256(EcdsaNistP256PublicKey),

ssh-key/src/public/key_data.rs

@@ -11,7 +11,7 @@ use super::{DsaPublicKey, OpaquePublicKey, RsaPublicKey};
 use super::{EcdsaPublicKey, SkEcdsaSha2NistP256};
 
 /// Public key data.
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 #[non_exhaustive]
 pub enum KeyData {
     /// Digital Signature Algorithm (DSA) public key data.

ssh-key/src/public/opaque.rs

@@ -16,7 +16,7 @@ use encoding::{Decode, Encode, Reader, Writer};
 ///
 /// The encoded representation of an `OpaquePublicKey` is the encoded representation of its
 /// [`OpaquePublicKeyBytes`].
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct OpaquePublicKey {
     /// The [`Algorithm`] of this public key.
     pub algorithm: Algorithm,
@@ -28,7 +28,7 @@ pub struct OpaquePublicKey {
 ///
 /// The encoded representation of an `OpaquePublicKeyBytes` consists of a 4-byte length prefix,
 /// followed by its byte representation.
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct OpaquePublicKeyBytes(Vec<u8>);
 
 impl OpaquePublicKey {

ssh-key/src/public/rsa.rs

@@ -13,7 +13,7 @@ use {
 /// RSA public key.
 ///
 /// Described in [RFC4253 § 6.6](https://datatracker.ietf.org/doc/html/rfc4253#section-6.6).
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct RsaPublicKey {
     /// RSA public exponent.
     pub e: Mpint,

ssh-key/src/public/sk.rs

@@ -18,7 +18,7 @@ const DEFAULT_APPLICATION_STRING: &str = "ssh:";
 /// Security Key (FIDO/U2F) ECDSA/NIST P-256 public key as specified in
 /// [PROTOCOL.u2f](https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.u2f?annotate=HEAD).
 #[cfg(feature = "ecdsa")]
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct SkEcdsaSha2NistP256 {
     /// Elliptic curve point representing a public key.
     ec_point: EcdsaNistP256PublicKey,
@@ -112,7 +112,7 @@ impl From<SkEcdsaSha2NistP256> for EcdsaNistP256PublicKey {
 
 /// Security Key (FIDO/U2F) Ed25519 public key as specified in
 /// [PROTOCOL.u2f](https://cvsweb.openbsd.org/src/usr.bin/ssh/PROTOCOL.u2f?annotate=HEAD).
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 pub struct SkEd25519 {
     /// Ed25519 public key.
     public_key: Ed25519PublicKey,

ssh-key/tests/public_key.rs

@@ -2,6 +2,7 @@
 
 use hex_literal::hex;
 use ssh_key::{Algorithm, PublicKey};
+use std::collections::HashSet;
 
 #[cfg(feature = "ecdsa")]
 use ssh_key::EcdsaCurve;
@@ -378,3 +379,10 @@ fn encode_rsa_4096_openssh() {
     let key = PublicKey::from_openssh(OPENSSH_RSA_4096_EXAMPLE).unwrap();
     assert_eq!(OPENSSH_RSA_4096_EXAMPLE.trim_end(), &key.to_string());
 }
+
+#[test]
+fn public_keys_are_hashable() {
+    let key = PublicKey::from_openssh(OPENSSH_ED25519_EXAMPLE).unwrap();
+    let set = HashSet::from([&key]);
+    assert_eq!(true, set.contains(&key));
+}