checksum last seen messages in acknowledgement order

src/client/chat.js

@@ -382,13 +382,15 @@ module.exports = function (client, options) {
   function getAcknowledgements () {
     let acc = 0
     const acknowledgements = []
+    const lastSeenMessages = []
 
     for (let i = 0; i < client._lastSeenMessages.capacity; i++) {
       const idx = (client._lastSeenMessages.offset + i) % 20
       const message = client._lastSeenMessages[idx]
       if (message) {
         acc |= 1 << i
         acknowledgements.push(message.signature)
+        lastSeenMessages.push(message)
         message.pending = false
       }
     }
@@ -400,7 +402,8 @@ module.exports = function (client, options) {
 
     return {
       acknowledgements,
-      acknowledged: bitset
+      acknowledged: bitset,
+      checksum: computeChatChecksum(lastSeenMessages)
     }
   }
 
@@ -411,15 +414,15 @@ module.exports = function (client, options) {
     if (message.startsWith('/')) {
       const command = message.slice(1)
       if (mcData.supportFeature('useChatSessions')) { // 1.19.3+
-        const { acknowledged, acknowledgements } = getAcknowledgements()
+        const { acknowledged, acknowledgements, checksum } = getAcknowledgements()
         const canSign = client.profileKeys && client._session
         const chatPacket = {
           command,
           timestamp: options.timestamp,
           salt: options.salt,
           argumentSignatures: canSign ? signaturesForCommand(command, options.timestamp, options.salt, options.preview, acknowledgements) : [],
           messageCount: client._lastSeenMessages.pending,
-          checksum: computeChatChecksum(client._lastSeenMessages), // 1.21.5+
+          checksum, // 1.21.5+
           acknowledged
         }
         client.write((mcData.supportFeature('seperateSignedChatCommandPacket') && canSign) ? 'chat_command_signed' : 'chat_command', chatPacket)
@@ -444,14 +447,14 @@ module.exports = function (client, options) {
     }
 
     if (mcData.supportFeature('useChatSessions')) {
-      const { acknowledgements, acknowledged } = getAcknowledgements()
+      const { acknowledgements, acknowledged, checksum } = getAcknowledgements()
       client.write('chat_message', {
         message,
         timestamp: options.timestamp,
         salt: options.salt,
         signature: (client.profileKeys && client._session) ? client.signMessage(message, options.timestamp, options.salt, undefined, acknowledgements) : undefined,
         offset: client._lastSeenMessages.pending,
-        checksum: computeChatChecksum(client._lastSeenMessages), // 1.21.5+
+        checksum, // 1.21.5+
         acknowledged
       })
       client._lastSeenMessages.pending = 0

test/chatAcknowledgementTest.js

@@ -0,0 +1,57 @@
+/* eslint-env mocha */
+
+const assert = require('assert')
+const EventEmitter = require('events')
+const injectChatPlugin = require('../src/client/chat')
+const { computeChatChecksum } = require('../src/datatypes/checksums')
+const { supportedVersions } = require('../src/version')
+
+const checksumVersions = supportedVersions.filter(version => require('minecraft-data')(version).version['>=']('1.21.5'))
+
+for (const version of checksumVersions) {
+  describe(`chat acknowledgements ${version}v`, () => {
+    for (const [outbound, packetName] of [
+      ['outbound message', 'chat_message'],
+      ['/outbound command', 'chat_command']
+    ]) {
+      it(`checksums wrapped last-seen messages in acknowledgement order for ${packetName}`, () => {
+        const client = new EventEmitter()
+        client.version = version
+        client.uuid = '00000000-0000-0000-0000-000000000001'
+
+        const writes = []
+        client.write = (name, data) => writes.push({ name, data })
+
+        injectChatPlugin(client, {})
+
+        const signatures = []
+        for (let i = 1; i <= 21; i++) {
+          const signature = Buffer.from([i, i + 1])
+          signatures.push(signature)
+          client.emit('player_chat', {
+            signature,
+            senderUuid: '00000000-0000-0000-0000-000000000002',
+            plainMessage: `message ${i}`,
+            index: i,
+            previousMessages: [],
+            salt: 1n,
+            timestamp: 1n,
+            unsignedChatContent: null,
+            type: 0,
+            networkName: null,
+            networkTargetName: null
+          })
+        }
+
+        client._signedChat(outbound, { timestamp: 1n, salt: 1n })
+
+        const expected = computeChatChecksum(
+          signatures.slice(-20).map(signature => ({ signature }))
+        )
+        assert.strictEqual(writes.length, 1)
+        assert.strictEqual(writes[0].name, packetName)
+        assert.strictEqual(writes[0].data.checksum, expected)
+      })
+    }
+  })
+}