Compressor handling update for 1.20.60 (#479)

* support compressor in header

* use mcdata features

* cleanup

Author: extremeheat

src/client.js

@@ -42,6 +42,7 @@ class Client extends Connection {
     this.validateOptions()
     this.serializer = createSerializer(this.options.version)
     this.deserializer = createDeserializer(this.options.version)
+    this._loadFeatures()
 
     KeyExchange(this, null, this.options)
     Login(this, null, this.options)
@@ -55,6 +56,17 @@ class Client extends Connection {
     this.emit('connect_allowed')
   }
 
+  _loadFeatures () {
+    try {
+      const mcData = require('minecraft-data')('bedrock_' + this.options.version)
+      this.features = {
+        compressorInHeader: mcData.supportFeature('compressorInPacketHeader')
+      }
+    } catch (e) {
+      throw new Error(`Unsupported version: '${this.options.version}', no data available`)
+    }
+  }
+
   connect () {
     if (!this.connection) throw new Error('Connect not currently allowed') // must wait for `connect_allowed`, or use `createClient`
     this.on('session', this._connect)
@@ -120,6 +132,7 @@ class Client extends Connection {
   updateCompressorSettings (packet) {
     this.compressionAlgorithm = packet.compression_algorithm || 'deflate'
     this.compressionThreshold = packet.compression_threshold
+    this.compressionReady = true
   }
 
   sendLogin () {

src/connection.js

@@ -65,7 +65,7 @@ class Connection extends EventEmitter {
   write (name, params) {
     this.outLog?.(name, params)
     if (name === 'start_game') this.updateItemPalette(params.itemstates)
-    const batch = new Framer(this.compressionAlgorithm, this.compressionLevel, this.compressionThreshold)
+    const batch = new Framer(this)
     const packet = this.serializer.createPacketBuffer({ name, params })
     batch.addEncodedPacket(packet)
 
@@ -91,7 +91,7 @@ class Connection extends EventEmitter {
 
   _tick () {
     if (this.sendQ.length) {
-      const batch = new Framer(this.compressionAlgorithm, this.compressionLevel, this.compressionThreshold)
+      const batch = new Framer(this)
       batch.addEncodedPackets(this.sendQ)
       this.sendQ = []
       this.sendIds = []
@@ -115,7 +115,7 @@ class Connection extends EventEmitter {
    */
   sendBuffer (buffer, immediate = false) {
     if (immediate) {
-      const batch = new Framer(this.compressionAlgorithm, this.compressionLevel, this.compressionThreshold)
+      const batch = new Framer(this)
       batch.addEncodedPacket(buffer)
       if (this.encryptionEnabled) {
         this.sendEncryptedBatch(batch)
@@ -150,13 +150,11 @@ class Connection extends EventEmitter {
   // These are callbacks called from encryption.js
   onEncryptedPacket = (buf) => {
     const packet = Buffer.concat([Buffer.from([0xfe]), buf]) // add header
-
     this.sendMCPE(packet)
   }
 
   onDecryptedPacket = (buf) => {
     const packets = Framer.getPackets(buf)
-
     for (const packet of packets) {
       this.readPacket(packet)
     }
@@ -167,11 +165,13 @@ class Connection extends EventEmitter {
       if (this.encryptionEnabled) {
         this.decrypt(buffer.slice(1))
       } else {
-        const packets = Framer.decode(this.compressionAlgorithm, buffer)
+        const packets = Framer.decode(this, buffer)
         for (const packet of packets) {
           this.readPacket(packet)
         }
       }
+    } else {
+      throw Error('Bad packet header ' + buffer[0])
     }
   }
 }

src/server.js

@@ -15,6 +15,7 @@ class Server extends EventEmitter {
 
     this.RakServer = require('./rak')(this.options.raknetBackend).RakServer
 
+    this._loadFeatures(this.options.version)
     this.serializer = createSerializer(this.options.version)
     this.deserializer = createDeserializer(this.options.version)
     this.advertisement = new ServerAdvertisement(this.options.motd, this.options.port, this.options.version)
@@ -27,6 +28,17 @@ class Server extends EventEmitter {
     this.setCompressor(this.options.compressionAlgorithm, this.options.compressionLevel, this.options.compressionThreshold)
   }
 
+  _loadFeatures (version) {
+    try {
+      const mcData = require('minecraft-data')('bedrock_' + version)
+      this.features = {
+        compressorInHeader: mcData.supportFeature('compressorInPacketHeader')
+      }
+    } catch (e) {
+      throw new Error(`Unsupported version: '${version}', no data available`)
+    }
+  }
+
   setCompressor (algorithm, level = 1, threshold = 256) {
     switch (algorithm) {
       case 'none':

src/serverPlayer.js

@@ -10,6 +10,7 @@ class Player extends Connection {
   constructor (server, connection) {
     super()
     this.server = server
+    this.features = server.features
     this.serializer = server.serializer
     this.deserializer = server.deserializer
     this.connection = connection
@@ -23,8 +24,8 @@ class Player extends Connection {
     this.status = ClientStatus.Authenticating
 
     if (isDebug) {
-      this.inLog = (...args) => debug('S ->', ...args)
-      this.outLog = (...args) => debug('S <-', ...args)
+      this.inLog = (...args) => debug('-> S', ...args)
+      this.outLog = (...args) => debug('<- S', ...args)
     }
 
     // Compression is server-wide
@@ -48,6 +49,7 @@ class Player extends Connection {
       client_throttle_scalar: 0
     })
     this._sentNetworkSettings = true
+    this.compressionReady = true
   }
 
   handleClientProtocolVersion (clientVersion) {
@@ -152,7 +154,7 @@ class Player extends Connection {
       return
     }
 
-    this.inLog?.(des.data.name, serialize(des.data.params).slice(0, 200))
+    this.inLog?.(des.data.name, serialize(des.data.params))
 
     switch (des.data.name) {
       // This is the first packet on 1.19.30 & above

src/transforms/encryption.js

@@ -36,7 +36,10 @@ function createEncryptor (client, iv) {
   // The send counter is represented as a little-endian 64-bit long and incremented after each packet.
 
   function process (chunk) {
-    const buffer = Zlib.deflateRawSync(chunk, { level: client.compressionLevel })
+    const compressed = Zlib.deflateRawSync(chunk, { level: client.compressionLevel })
+    const buffer = client.features.compressorInHeader
+      ? Buffer.concat([Buffer.from([0]), compressed])
+      : compressed
     const packet = Buffer.concat([buffer, computeCheckSum(buffer, client.sendCounter, client.secretKeyBytes)])
     client.sendCounter++
     client.cipher.write(packet)
@@ -70,7 +73,22 @@ function createDecryptor (client, iv) {
       return
     }
 
-    const buffer = Zlib.inflateRawSync(chunk, { chunkSize: 512000 })
+    let buffer
+    if (client.features.compressorInHeader) {
+      switch (packet[0]) {
+        case 0:
+          buffer = Zlib.inflateRawSync(packet.slice(1), { chunkSize: 512000 })
+          break
+        case 255:
+          buffer = packet.slice(1)
+          break
+        default:
+          client.emit('error', Error(`Unsupported compressor: ${packet[0]}`))
+      }
+    } else {
+      buffer = Zlib.inflateRawSync(packet, { chunkSize: 512000 })
+    }
+
     client.onDecryptedPacket(buffer)
   }
 

src/transforms/framer.js

@@ -3,12 +3,13 @@ const zlib = require('zlib')
 
 // Concatenates packets into one batch packet, and adds length prefixs.
 class Framer {
-  constructor (compressor, compressionLevel, compressionThreshold) {
+  constructor (client) {
     // Encoding
     this.packets = []
-    this.compressor = compressor || 'none'
-    this.compressionLevel = compressionLevel
-    this.compressionThreshold = compressionThreshold
+    this.compressor = client.compressionAlgorithm || 'none'
+    this.compressionLevel = client.compressionLevel
+    this.compressionThreshold = client.compressionThreshold
+    this.writeCompressor = client.features.compressorInHeader && client.compressionReady
   }
 
   // No compression in base class
@@ -21,30 +22,45 @@ class Framer {
   }
 
   static decompress (algorithm, buffer) {
-    try {
-      switch (algorithm) {
-        case 'deflate': return zlib.inflateRawSync(buffer, { chunkSize: 512000 })
-        case 'snappy': throw Error('Snappy compression not implemented')
-        case 'none': return buffer
-        default: throw Error('Unknown compression type ' + this.compressor)
-      }
-    } catch {
-      return buffer
+    switch (algorithm) {
+      case 0:
+      case 'deflate':
+        return zlib.inflateRawSync(buffer, { chunkSize: 512000 })
+      case 1:
+      case 'snappy':
+        throw Error('Snappy compression not implemented')
+      case 'none':
+      case 255:
+        return buffer
+      default: throw Error('Unknown compression type ' + algorithm)
     }
   }
 
-  static decode (compressor, buf) {
+  static decode (client, buf) {
     // Read header
     if (buf[0] !== 0xfe) throw Error('bad batch packet header ' + buf[0])
     const buffer = buf.slice(1)
-    const decompressed = this.decompress(compressor, buffer)
+    // Decompress
+    let decompressed
+    if (client.features.compressorInHeader && client.compressionReady) {
+      decompressed = this.decompress(buffer[0], buffer.slice(1))
+    } else {
+      // On old versions, compressor is session-wide ; failing to decompress
+      // a packet will assume it's not compressed
+      try {
+        decompressed = this.decompress(client.compressionAlgorithm, buffer)
+      } catch (e) {
+        decompressed = buffer
+      }
+    }
     return Framer.getPackets(decompressed)
   }
 
   encode () {
     const buf = Buffer.concat(this.packets)
     const compressed = (buf.length > this.compressionThreshold) ? this.compress(buf) : buf
-    return Buffer.concat([Buffer.from([0xfe]), compressed])
+    const header = this.writeCompressor ? [0xfe, 0] : [0xfe]
+    return Buffer.concat([Buffer.from(header), compressed])
   }
 
   addEncodedPacket (chunk) {