Reorganise Minecraft network-facing code.

src/minecraft/connection.ts

@@ -17,17 +17,14 @@ import {
   parseCompressedPacket,
   parsePacket
 } from './packet'
-import { resolveHostname } from './utils'
-import { readVarInt, writeVarInt } from './packetUtils'
-import { authUrl, generateSharedSecret, mcHexDigest } from './onlineMode'
-
-export declare interface ServerConnection {
-  on: ((event: 'packet', listener: (packet: Packet) => void) => this) &
-    ((event: 'error', listener: (error: Error) => void) => this) &
-    ((event: 'data', listener: (data: Buffer) => void) => this) &
-    ((event: 'close', listener: () => void) => this) &
-    ((event: string, listener: Function) => this)
-}
+import {
+  readVarInt,
+  writeVarInt,
+  resolveHostname,
+  generateSharedSecret,
+  mcHexDigest,
+  authUrl
+} from './utils'
 
 export interface ConnectionOptions {
   host: string
@@ -38,6 +35,14 @@ export interface ConnectionOptions {
   accessToken?: string
 }
 
+export declare interface ServerConnection {
+  on: ((event: 'packet', listener: (packet: Packet) => void) => this) &
+    ((event: 'error', listener: (error: Error) => void) => this) &
+    ((event: 'data', listener: (data: Buffer) => void) => this) &
+    ((event: 'close', listener: () => void) => this) &
+    ((event: string, listener: Function) => this)
+}
+
 export class ServerConnection extends events.EventEmitter {
   bufferedData: Buffer = Buffer.from([])
   compressionThreshold = -1
@@ -155,22 +160,10 @@ const initiateConnection = async (opts: ConnectionOptions) => {
               conn.close()
             } else if (packet.id === 0x01 && !conn.loggedIn) {
               // https://wiki.vg/Protocol_Encryption
-              const [serverIdLen, serverIdLenLen] = readVarInt(packet.data)
-              // ASCII encoding of the server id string from Encryption Request
-              const serverId = packet.data.slice(
-                serverIdLenLen,
-                serverIdLen + serverIdLenLen
-              )
-              const data = packet.data.slice(serverIdLen + serverIdLenLen)
-              const [pkLen, pkLenLen] = readVarInt(data)
-              // Server's encoded public key from Encryption Request
-              const publicKey = data.slice(pkLenLen, pkLen + pkLenLen)
-              const verifyTokenData = data.slice(pkLen + pkLenLen)
-              const [, verifyTokenLengthLength] = readVarInt(verifyTokenData)
-              const verifyToken = verifyTokenData.slice(verifyTokenLengthLength)
+              const [serverId, publicKey, verifyToken] =
+                parseEncryptionRequestPacket(packet)
               ;(async () => {
-                // Generate random 16-byte shared secret.
-                const sharedSecret = await generateSharedSecret()
+                const sharedSecret = await generateSharedSecret() // Generate random 16-byte shared secret.
                 // Generate hash.
                 const sha1 = createHash('sha1')
                 sha1.update(serverId) // ASCII encoding of the server id string from Encryption Request
@@ -200,6 +193,12 @@ const initiateConnection = async (opts: ConnectionOptions) => {
                 const encryptedSharedSecret = publicEncrypt(ePrms, sharedSecret)
                 const encryptedVerifyToken = publicEncrypt(ePrms, verifyToken)
                 // Send encryption response packet.
+                // From this point forward, everything is encrypted, including the Login Success packet.
+                conn.aesDecipher = createDecipheriv(
+                  'aes-128-cfb8',
+                  sharedSecret,
+                  sharedSecret
+                )
                 await conn.writePacket(
                   0x01,
                   concatPacketData([
@@ -209,10 +208,11 @@ const initiateConnection = async (opts: ConnectionOptions) => {
                     encryptedVerifyToken
                   ])
                 )
-                // From this point forward, everything is encrypted, including the Login Success packet.
-                const ss = sharedSecret
-                conn.aesDecipher = createDecipheriv('aes-128-cfb8', ss, ss)
-                conn.aesCipher = createCipheriv('aes-128-cfb8', ss, ss)
+                conn.aesCipher = createCipheriv(
+                  'aes-128-cfb8',
+                  sharedSecret,
+                  sharedSecret
+                )
               })().catch(e => {
                 console.error(e)
                 conn.disconnectReason =
@@ -242,3 +242,20 @@ const initiateConnection = async (opts: ConnectionOptions) => {
 }
 
 export default initiateConnection
+
+const parseEncryptionRequestPacket = (packet: Packet) => {
+  // ASCII encoding of the server id string
+  let data = packet.data
+  const [sidLen, sidLenLen] = readVarInt(data)
+  const serverId = data.slice(sidLenLen, sidLenLen + sidLen)
+  // Server's encoded public key
+  data = data.slice(sidLen + sidLenLen)
+  const [pkLen, pkLenLen] = readVarInt(data)
+  const publicKey = data.slice(pkLenLen, pkLen + pkLenLen)
+  // Server's randomly generated verify token
+  data = data.slice(pkLen + pkLenLen)
+  const [vtLen, vtLenLen] = readVarInt(data)
+  const verifyToken = data.slice(vtLenLen, vtLenLen + vtLen)
+
+  return [serverId, publicKey, verifyToken]
+}

src/minecraft/packet.ts

@@ -1,7 +1,6 @@
 import zlib from 'zlib'
 import { Buffer } from 'buffer'
-import { toggleEndian } from './utils'
-import { encodeString, readVarInt, writeVarInt } from './packetUtils'
+import { toggleEndian, encodeString, readVarInt, writeVarInt } from './utils'
 
 export const makeBasePacket = (packetId: number, data: Buffer) => {
   const finalData = Buffer.concat([writeVarInt(packetId), data])

src/minecraft/pingServer.ts

@@ -1,10 +1,15 @@
 import net from 'react-native-tcp'
 import { Buffer } from 'buffer'
 
+import {
+  toggleEndian,
+  padBufferToLength,
+  resolveHostname,
+  readVarInt,
+  writeVarInt
+} from './utils'
 import { makeBasePacket, concatPacketData, parsePacket, Packet } from './packet'
-import { toggleEndian, padBufferToLength, resolveHostname } from './utils'
 import { parseValidJson, PlainTextChat } from './chatToJsx'
-import { readVarInt, writeVarInt } from './packetUtils'
 
 export interface LegacyPing {
   ff: number

src/minecraft/utils.ts

@@ -1,3 +1,5 @@
+// Other crypto libraries: simple-crypto, sha256, aes-crypto and rsa-native
+import { randomBytes } from 'react-native-randombytes'
 import { Buffer } from 'buffer'
 
 export const protocolMap = {
@@ -56,3 +58,86 @@ export const resolveHostname = async (
     return [record[3], +record[2]]
   } else return [hostname, port]
 }
+
+// Online-mode cryptography utilities.
+export const authUrl = 'https://sessionserver.mojang.com/session/minecraft/join'
+
+export const generateSharedSecret = async () =>
+  await new Promise<Buffer>((resolve, reject) => {
+    randomBytes(16, (err, buf) => {
+      if (err) reject(err)
+      else resolve(buf)
+    })
+  })
+
+// Credits for following 2 functions: https://gist.github.com/andrewrk/4425843
+export function mcHexDigest(hash: Buffer) {
+  // check for negative hashes
+  const negative = hash.readInt8(0) < 0
+  if (negative) performTwosCompliment(hash)
+  let digest = hash.toString('hex')
+  // trim leading zeroes
+  digest = digest.replace(/^0+/g, '')
+  if (negative) digest = '-' + digest
+  return digest
+}
+
+function performTwosCompliment(buffer: Buffer) {
+  let carry = true
+  let newByte, value
+  for (let i = buffer.length - 1; i >= 0; --i) {
+    value = buffer.readUInt8(i)
+    newByte = ~value & 0xff
+    if (carry) {
+      carry = newByte === 0xff
+      buffer.writeUInt8(carry ? 0 : newByte + 1, i)
+    } else {
+      buffer.writeUInt8(newByte, i)
+    }
+  }
+}
+
+// Minecraft data type utilities.
+export const encodeString = (str: string): Buffer => {
+  const buffer = Buffer.from(str, 'utf8')
+  return Buffer.concat([writeVarInt(buffer.byteLength), buffer])
+}
+
+// Adapted from https://wiki.vg/Protocol which is licensed under CC-BY-SA-3.0.
+// VarLong is unsupported as JavaScript cannot fit VarLong except with BigInt.
+// BigInt is unsupported in React Native at the moment.
+export const readVarInt = (
+  buffer: Buffer,
+  offset: number = 0,
+  varlong: boolean = false
+): [number, number] => {
+  let numRead = 0
+  let result = 0
+  let read: number
+  do {
+    read = buffer.readUInt8(offset + numRead)
+    const value = read & 0b01111111
+    result |= value << (7 * numRead)
+    numRead++
+    if (!varlong && numRead > 5) {
+      throw new Error('VarInt is too big')
+    } else if (varlong && numRead > 10) {
+      throw new Error('VarLong is too big')
+    }
+  } while ((read & 0b10000000) !== 0)
+  return [result, numRead]
+}
+
+export const writeVarInt = (value: number): Buffer => {
+  let result = Buffer.alloc(0)
+  do {
+    let temp = value & 0b01111111
+    // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
+    value >>>= 7
+    if (value !== 0) {
+      temp |= 0b10000000
+    }
+    result = Buffer.concat([result, Buffer.from([temp])])
+  } while (value !== 0)
+  return result
+}

src/screens/ChatScreen.tsx

@@ -24,7 +24,7 @@ import {
   ClickEvent,
   ColorMap
 } from '../minecraft/chatToJsx'
-import { readVarInt, writeVarInt } from '../minecraft/packetUtils'
+import { readVarInt, writeVarInt } from '../minecraft/utils'
 import { concatPacketData } from '../minecraft/packet'
 import TextField from '../components/TextField'
 import Text from '../components/Text'

src/screens/accounts/AccountScreen.tsx

@@ -9,7 +9,7 @@ import Dialog, { dialogStyles } from '../../components/Dialog'
 import useDarkMode from '../../context/useDarkMode'
 import UsersContext from '../../context/accountsContext'
 import ElevatedView from '../../components/ElevatedView'
-import { invalidate } from '../../minecraft/yggdrasil'
+import { invalidate } from '../../minecraft/authentication/yggdrasil'
 
 // LOW-TODO: Reload to update account info for online mode using /refresh.
 // Also, to reload all the skin images?

src/screens/accounts/AddAccountDialog.tsx

@@ -8,7 +8,7 @@ import Dialog, { dialogStyles } from '../../components/Dialog'
 import TextField from '../../components/TextField'
 import useDarkMode from '../../context/useDarkMode'
 import UsersContext from '../../context/accountsContext'
-import { authenticate } from '../../minecraft/yggdrasil'
+import { authenticate } from '../../minecraft/authentication/yggdrasil'
 
 const AddAccountDialog = ({
   open,

src/screens/accounts/MicrosoftLogin.tsx

@@ -13,7 +13,7 @@ import {
   getXstsTokenAndUserHash,
   authenticateWithXsts,
   getGameProfile
-} from '../../minecraft/microsoft'
+} from '../../minecraft/authentication/microsoft'
 
 const MicrosoftLogin = ({ close }: { close: () => void }) => {
   const darkMode = useDarkMode()