fix (Connection): Add error handler to websocket instance (#393)

* add error handler to websocket instance to avoid crashing when receiving an invalid websocket frame

packages/server/src/Connection.ts

@@ -68,6 +68,7 @@ export class Connection {
     this.webSocket.on('close', this.close.bind(this))
     this.webSocket.on('message', this.handleMessage.bind(this))
     this.webSocket.on('pong', () => { this.pongReceived = true })
+    this.webSocket.on('error', this.handleError.bind(this))
 
     this.sendCurrentAwareness()
   }
@@ -175,6 +176,17 @@ export class Connection {
     ).apply(this.document, this)
   }
 
+  /**
+   * Handle a ws instance error, which is required to prevent
+   * the server from crashing when one happens
+   * See https://github.com/websockets/ws/issues/1777#issuecomment-660803472
+   * @private
+   */
+  private handleError(error: any): void {
+    this.logger.log('Error emitted from webSocket instance:')
+    this.logger.log(error)
+  }
+
   /**
    * Get the underlying connection instance
    * @deprecated

tests/server/websocketError.ts

@@ -0,0 +1,25 @@
+import test from 'ava'
+import { newHocuspocus, newHocuspocusProvider } from '../utils'
+
+test('does not crash when invalid opcode is sent', async t => {
+  await new Promise(resolve => {
+    const server = newHocuspocus()
+
+    const provider = newHocuspocusProvider(server, {
+      onSynced() {
+        // Send a bad opcode via the low level internal _socket
+        // Inspired by https://github.com/websockets/ws/blob/975382178f8a9355a5a564bb29cb1566889da9ba/test/websocket.test.js#L553-L589
+        // @ts-ignore
+        provider.webSocket?._socket.write(Buffer.from([0x00, 0x00])) // eslint-disable-line
+      },
+      onClose({ event }) {
+        t.is(event.code, 1002)
+        provider.destroy()
+      },
+      onDestroy() {
+        t.pass()
+        resolve(true)
+      },
+    })
+  })
+})