Support encrypted native identity keys

src/native.rs

@@ -358,13 +358,24 @@ pub fn derive_native_session_key(
 }
 
 pub fn load_ed25519_identity(path: &Path) -> Result<SigningKey> {
+    load_ed25519_identity_with_passphrase(path, None)
+}
+
+pub fn load_ed25519_identity_with_passphrase(
+    path: &Path,
+    passphrase: Option<&str>,
+) -> Result<SigningKey> {
     let private_key = ssh_key::PrivateKey::read_openssh_file(path)
         .with_context(|| format!("read OpenSSH identity {}", path.display()))?;
-    anyhow::ensure!(
-        !private_key.is_encrypted(),
-        "OpenSSH identity {} is encrypted; encrypted-key prompts are not wired yet",
-        path.display()
-    );
+    let private_key = if private_key.is_encrypted() {
+        let passphrase = passphrase
+            .ok_or_else(|| anyhow::anyhow!("OpenSSH identity {} is encrypted", path.display()))?;
+        private_key
+            .decrypt(passphrase)
+            .with_context(|| format!("decrypt OpenSSH identity {}", path.display()))?
+    } else {
+        private_key
+    };
     let ed25519 = private_key
         .key_data()
         .ed25519()
@@ -929,6 +940,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn load_ed25519_identity_decrypts_encrypted_openssh_private_key() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("id_ed25519");
+        let signing = SigningKey::from_bytes(&[12u8; 32]);
+        let keypair = ssh_key::private::Ed25519Keypair::from(&signing);
+        let private =
+            ssh_key::PrivateKey::new(ssh_key::private::KeypairData::from(keypair), "").unwrap();
+        let encrypted = private
+            .encrypt(&mut rand::rngs::OsRng, "correct horse battery staple")
+            .unwrap();
+        encrypted
+            .write_openssh_file(&path, ssh_key::LineEnding::LF)
+            .unwrap();
+
+        assert!(load_ed25519_identity(&path).is_err());
+        assert!(load_ed25519_identity_with_passphrase(&path, Some("wrong")).is_err());
+        let loaded =
+            load_ed25519_identity_with_passphrase(&path, Some("correct horse battery staple"))
+                .unwrap();
+        assert_eq!(
+            VerifyingKey::from(&loaded).to_bytes(),
+            VerifyingKey::from(&signing).to_bytes()
+        );
+    }
+
     #[test]
     fn native_session_key_derivation_matches_and_binds_transcript() {
         let host_signing = SigningKey::from_bytes(&[3u8; 32]);