Harden terminal reconnect packet handling

src/bin/dosh-client.rs

@@ -5679,19 +5679,21 @@ fn stale_mouse_report_maybe_incomplete(bytes: &[u8], offset: usize) -> bool {
         [0x1b] | [0x1b, b'['] | [0x1b, b'[', b'<'] => true,
         [0x1b, b'[', b'M', ..] if rest.len() < 6 => true,
         [0x1b, b'[', b'<', params @ ..] | [0x1b, b'[', params @ ..]
-            if params_are_mouse_prefix(params) =>
+            if params_are_mouse_prefix(params, 2) =>
         {
             true
         }
         [0x9b] | [0x9b, b'<'] => true,
         [0x9b, b'M', ..] if rest.len() < 5 => true,
-        [0x9b, b'<', params @ ..] | [0x9b, params @ ..] if params_are_mouse_prefix(params) => true,
-        params if params_are_mouse_prefix(params) => true,
+        [0x9b, b'<', params @ ..] | [0x9b, params @ ..] if params_are_mouse_prefix(params, 2) => {
+            true
+        }
+        params if params_are_mouse_prefix(params, 2) => true,
         _ => false,
     }
 }
 
-fn params_are_mouse_prefix(params: &[u8]) -> bool {
+fn params_are_mouse_prefix(params: &[u8], min_semicolons: usize) -> bool {
     let mut semicolons = 0usize;
     let mut saw_digit = false;
     for byte in params {
@@ -5701,7 +5703,7 @@ fn params_are_mouse_prefix(params: &[u8]) -> bool {
             _ => return false,
         }
     }
-    saw_digit && semicolons >= 1
+    saw_digit && semicolons >= min_semicolons
 }
 
 async fn flush_startup_input_if_ready(
@@ -8529,6 +8531,20 @@ mod tests {
         assert_eq!(strip_stale_mouse_reports(b"10m"), b"");
     }
 
+    #[test]
+    fn numeric_semicolon_input_survives_stale_filter() {
+        assert_eq!(strip_stale_mouse_reports(b"123;"), b"123;");
+        assert_eq!(strip_stale_mouse_reports(b"12;34"), b"12;34");
+        assert_eq!(strip_stale_mouse_reports(b"echo 1;"), b"echo 1;");
+    }
+
+    #[test]
+    fn incomplete_three_field_mouse_prefix_is_suppressed() {
+        assert_eq!(strip_stale_mouse_reports(b"35;152;"), b"");
+        assert_eq!(strip_stale_mouse_reports(b"\x1b[<35;152;"), b"");
+        assert_eq!(strip_stale_mouse_reports(b"\x9b35;152;"), b"");
+    }
+
     #[test]
     fn stale_focus_reports_are_stripped_from_pending_input() {
         assert_eq!(strip_stale_mouse_reports(b"\x1b[Ihello\x1b[O"), b"hello");

src/bin/dosh-server.rs

@@ -865,6 +865,7 @@ async fn handle_packet(
         | PacketKind::StreamEof
         | PacketKind::StreamWindowAdjust
         | PacketKind::RekeyAck
+        | PacketKind::Detach
             if find_client_decrypt_key(state, &packet.header).is_err() =>
         {
             send_reject_to_client(socket, peer, packet.header.conn_id, "unknown client").await
@@ -1734,7 +1735,14 @@ async fn handle_ping(
 }
 
 async fn handle_detach(state: &Arc<Mutex<ServerState>>, packet: &protocol::Packet) -> Result<()> {
+    let (key, _) = find_client_decrypt_key(state, &packet.header)?;
+    let _ = protocol::decrypt_body(packet, &key, CLIENT_TO_SERVER)?;
     let mut locked = state.lock().expect("server state poisoned");
+    if let Some(client) = locked.client_mut(&packet.header.conn_id) {
+        if !client.replay.accept(packet.header.seq) {
+            return Ok(());
+        }
+    }
     locked.remove_client_everywhere(&packet.header.conn_id);
     Ok(())
 }
@@ -4105,6 +4113,63 @@ mod tests {
         assert!(locked.lookup_client(&client_id).is_none());
     }
 
+    #[tokio::test]
+    async fn forged_plaintext_detach_does_not_remove_client() {
+        let (pty_tx, _pty_rx) = mpsc::unbounded_channel();
+        let mut state = ServerState::new(ServerConfig::default(), [0u8; 32], pty_tx);
+        state
+            .ensure_session("work", 80, 24, "forward-only", &[])
+            .unwrap();
+        let client_id = [21u8; 16];
+        let session_key = [22u8; 32];
+        state.insert_client("work", client_id, test_client_state(session_key));
+        let state = Arc::new(Mutex::new(state));
+        let mut packet = protocol::decode(
+            &protocol::encode_plain(PacketKind::Detach, client_id, 1, 0, b"").unwrap(),
+        )
+        .unwrap();
+        packet.header.session_key_id = protocol::session_key_id(&session_key);
+
+        assert!(handle_detach(&state, &packet).await.is_err());
+
+        let locked = state.lock().unwrap();
+        assert!(
+            locked.lookup_client(&client_id).is_some(),
+            "plaintext detach with a copied key id must not remove a live client"
+        );
+    }
+
+    #[tokio::test]
+    async fn authenticated_detach_removes_client() {
+        let (pty_tx, _pty_rx) = mpsc::unbounded_channel();
+        let mut state = ServerState::new(ServerConfig::default(), [0u8; 32], pty_tx);
+        state
+            .ensure_session("work", 80, 24, "forward-only", &[])
+            .unwrap();
+        let client_id = [23u8; 16];
+        let session_key = [24u8; 32];
+        state.insert_client("work", client_id, test_client_state(session_key));
+        let state = Arc::new(Mutex::new(state));
+        let packet = protocol::decode(
+            &protocol::encode_encrypted(
+                PacketKind::Detach,
+                client_id,
+                1,
+                0,
+                &session_key,
+                CLIENT_TO_SERVER,
+                b"",
+            )
+            .unwrap(),
+        )
+        .unwrap();
+
+        handle_detach(&state, &packet).await.unwrap();
+
+        let locked = state.lock().unwrap();
+        assert!(locked.lookup_client(&client_id).is_none());
+    }
+
     #[tokio::test]
     async fn duplicate_stream_open_for_open_stream_resends_ok() {
         let (pty_tx, _pty_rx) = mpsc::unbounded_channel();

src/protocol.rs

@@ -280,7 +280,7 @@ pub fn decode(input: &[u8]) -> Result<Packet> {
 
 pub fn decrypt_body(packet: &Packet, key: &[u8; 32], direction: u32) -> Result<Vec<u8>> {
     if packet.header.flags & 1 == 0 {
-        return Ok(packet.body.clone());
+        bail!("packet body is not encrypted");
     }
     let nonce = crypto::nonce_from(direction, packet.header.seq);
     let aad = packet.header.aad();

tests/protocol_auth.rs

@@ -58,6 +58,19 @@ fn encrypted_packet_round_trips() {
     assert_eq!(plain, b"hello");
 }
 
+#[test]
+fn plaintext_packet_never_decrypts_as_authenticated_body() {
+    let key = crypto::random_32();
+    let mut decoded = protocol::decode(
+        &protocol::encode_plain(PacketKind::Input, crypto::random_16(), 1, 0, b"hello").unwrap(),
+    )
+    .unwrap();
+    decoded.header.session_key_id = protocol::session_key_id(&key);
+
+    let err = protocol::decrypt_body(&decoded, &key, CLIENT_TO_SERVER).unwrap_err();
+    assert!(err.to_string().contains("not encrypted"));
+}
+
 #[test]
 fn encrypted_packet_rejects_wrong_session_key_id_before_decrypt() {
     let key = crypto::random_32();