fix(cable): propagate post-handshake errors from protocol::connection (#217)

- Add EncryptionFailed transport error variant
- Surface decode/encrypt failures out of the cable connection task instead of swallowing them
- Forward tunnel-connection errors via send_error so callers see the real cause
- Hoist CableTunnelMessage::from_slice and CableKnownDeviceInfo::new to return TransportError directly

Author: AlfioEmanueleFresta

libwebauthn/src/transport/cable/known_devices.rs

@@ -98,24 +98,27 @@ impl From<&CableLinkingInfo> for CableKnownDeviceId {
 }
 
 impl CableKnownDeviceInfo {
-    pub(crate) fn new(tunnel_domain: &str, linking_info: &CableLinkingInfo) -> Result<Self, Error> {
+    pub(crate) fn new(
+        tunnel_domain: &str,
+        linking_info: &CableLinkingInfo,
+    ) -> Result<Self, TransportError> {
         let info = Self {
             contact_id: linking_info.contact_id.to_vec(),
             link_id: linking_info
                 .link_id
                 .clone()
                 .try_into()
-                .map_err(|_| Error::Transport(TransportError::InvalidFraming))?,
+                .map_err(|_| TransportError::InvalidFraming)?,
             link_secret: linking_info
                 .link_secret
                 .clone()
                 .try_into()
-                .map_err(|_| Error::Transport(TransportError::InvalidFraming))?,
+                .map_err(|_| TransportError::InvalidFraming)?,
             public_key: linking_info
                 .authenticator_public_key
                 .clone()
                 .try_into()
-                .map_err(|_| Error::Transport(TransportError::InvalidFraming))?,
+                .map_err(|_| TransportError::InvalidFraming)?,
             name: linking_info.authenticator_name.clone(),
             tunnel_domain: tunnel_domain.to_string(),
         };
@@ -223,10 +226,17 @@ impl<'d> Device<'d, Cable, CableChannel> for CableKnownDevice {
                 cbor_rx_send,
             );
 
-            protocol::connection(tunnel_input).await;
-            ux_sender
-                .set_connection_state(ConnectionState::Terminated)
-                .await;
+            match protocol::connection(tunnel_input).await {
+                Ok(()) => {
+                    ux_sender
+                        .set_connection_state(ConnectionState::Terminated)
+                        .await;
+                }
+                Err(e) => {
+                    // send_error already transitions to Terminated.
+                    ux_sender.send_error(e).await;
+                }
+            }
         });
 
         Ok(CableChannel {