websocket: improve parseCloseBody

lib/web/websocket/receiver.js

@@ -108,7 +108,7 @@ class ByteParser extends Writable {
             // sending a Close frame in response, the endpoint typically echos the
             // status code it received.)
             let body = emptyBuffer
-            if (this.#info.closeInfo.code) {
+            if (this.#info.closeInfo?.code) {
               body = Buffer.allocUnsafe(2)
               body.writeUInt16BE(this.#info.closeInfo.code, 0)
             }
@@ -298,26 +298,30 @@ class ByteParser extends Writable {
       // defined as the status code (Section 7.4) contained in the first Close
       // control frame received by the application
       code = data.readUInt16BE(0)
+      if (!isValidStatusCode(code)) {
+        return null
+      }
+    } else {
+      return null
     }
 
     // https://datatracker.ietf.org/doc/html/rfc6455#section-7.1.6
-    /** @type {Buffer} */
-    let reason = data.subarray(2)
+    /** @type {number} */
+    let reasonOffset = 2
 
-    // Remove BOM
-    if (reason[0] === 0xEF && reason[1] === 0xBB && reason[2] === 0xBF) {
-      reason = reason.subarray(3)
+    // Detect BOM and ignore it
+    if (data.length >= 5 && data[2] === 0xEF && data[3] === 0xBB && data[4] === 0xBF) {
+      reasonOffset = 5
     }
 
-    if (code !== undefined && !isValidStatusCode(code)) {
-      return null
+    if (data.length - reasonOffset < 1) {
+      return { code, reason: '' }
     }
 
+    let reason = ''
     try {
-      reason = utf8Decode(reason)
-    } catch {
-      return null
-    }
+      reason = utf8Decode(data.subarray(reasonOffset))
+    } catch { }
 
     return { code, reason }
   }

test/websocket/receive.js

@@ -1,11 +1,13 @@
 'use strict'
 
+const { tspl } = require('@matteo.collina/tspl')
 const { test } = require('node:test')
-const assert = require('node:assert')
 const { WebSocketServer } = require('ws')
 const { WebSocket } = require('../..')
 
-test('Receiving a frame with a payload length > 2^31-1 bytes', () => {
+test('Receiving a frame with a payload length > 2^31-1 bytes', async (t) => {
+  t = tspl(t, { plan: 1 })
+
   const server = new WebSocketServer({ port: 0 })
 
   server.on('connection', (ws) => {
@@ -16,19 +18,20 @@ test('Receiving a frame with a payload length > 2^31-1 bytes', () => {
 
   const ws = new WebSocket(`ws://localhost:${server.address().port}`)
 
-  return new Promise((resolve, reject) => {
-    ws.onmessage = reject
+  ws.onmessage = t.fail
 
-    ws.addEventListener('error', (event) => {
-      assert.ok(event.error instanceof Error) // error event is emitted
-      ws.close()
-      server.close()
-      resolve()
-    })
+  ws.addEventListener('error', (event) => {
+    ws.close()
+    server.close()
+    t.ok(event.error instanceof Error) // error event is emitted
   })
+
+  await t.completed
 })
 
-test('Receiving an ArrayBuffer', () => {
+test('Receiving an ArrayBuffer', async (t) => {
+  t = tspl(t, { plan: 3 })
+
   const server = new WebSocketServer({ port: 0 })
 
   server.on('connection', (ws) => {
@@ -43,18 +46,44 @@ test('Receiving an ArrayBuffer', () => {
 
   ws.addEventListener('open', () => {
     ws.binaryType = 'what'
-    assert.equal(ws.binaryType, 'blob')
+    t.strictEqual(ws.binaryType, 'blob')
 
     ws.binaryType = 'arraybuffer' // <--
     ws.send('Hello')
   })
 
-  return new Promise((resolve) => {
-    ws.addEventListener('message', ({ data }) => {
-      assert.ok(data instanceof ArrayBuffer)
-      assert.deepStrictEqual(Buffer.from(data), Buffer.from('Hello'))
-      server.close()
-      resolve()
+  ws.addEventListener('message', ({ data }) => {
+    t.ok(data instanceof ArrayBuffer)
+    t.deepStrictEqual(Buffer.from(data), Buffer.from('Hello'))
+    server.close()
+  })
+
+  await t.completed
+})
+
+test('Receiving a close reason', async (t) => {
+  t = tspl(t, { plan: 1 })
+
+  const server = new WebSocketServer({ port: 0 })
+
+  server.on('connection', (ws) => {
+    ws.on('message', (data, isBinary) => {
+      ws.send(data, { binary: true })
+
+      ws.close(1000, Buffer.from('\uFEFFGood Bye!'))
     })
   })
+
+  const ws = new WebSocket(`ws://localhost:${server.address().port}`)
+
+  ws.addEventListener('open', () => {
+    ws.send('Hello')
+  })
+
+  ws.addEventListener('close', ({ reason }) => {
+    t.strictEqual(reason, 'Good Bye!')
+    server.close()
+  })
+
+  await t.completed
 })