Implement force online/offline mode and offline name listening, create separated packet codec handler

src/main/kotlin/com/github/creeper123123321/viaaas/CloudCodec.kt

@@ -1,6 +1,7 @@
 package com.github.creeper123123321.viaaas
 
 import io.netty.buffer.ByteBuf
+import io.netty.buffer.ByteBufAllocator
 import io.netty.channel.Channel
 import io.netty.channel.ChannelHandlerContext
 import io.netty.channel.ChannelInitializer
@@ -27,6 +28,7 @@ object FrontChannelInit : ChannelInitializer<Channel>() {
             .addLast("frame", FrameCodec())
             // "compress"
             .addLast("flow-handler", FlowControlHandler())
+            .addLast("mc", CloudMinecraftCodec())
             .addLast(
                 "handler", CloudMinecraftHandler(
                     ConnectionData(frontChannel = ch), other = null, frontEnd = true
@@ -44,10 +46,34 @@ class BackendInit(val connectionData: ConnectionData) : ChannelInitializer<Chann
             .addLast("frame", FrameCodec())
             // compress
             .addLast("via-codec", CloudViaCodec(user))
+            .addLast("mc", CloudMinecraftCodec())
             .addLast("handler", CloudMinecraftHandler(connectionData, connectionData.frontChannel, frontEnd = false))
     }
 }
 
+class CloudMinecraftCodec: MessageToMessageCodec<ByteBuf, Packet>() {
+    override fun encode(ctx: ChannelHandlerContext, msg: Packet, out: MutableList<Any>) {
+        if (!ctx.channel().isActive) return
+        val buf = ByteBufAllocator.DEFAULT.buffer()
+        try {
+            val handler = ctx.pipeline().get(CloudMinecraftHandler::class.java)
+            PacketRegistry.encode(msg, buf, handler.data.frontVer!!)
+            out.add(buf.retain())
+        } finally {
+            buf.release()
+        }
+    }
+
+    override fun decode(ctx: ChannelHandlerContext, msg: ByteBuf, out: MutableList<Any>) {
+        if (!ctx.channel().isActive || !msg.isReadable) return
+        val handler = ctx.pipeline().get(CloudMinecraftHandler::class.java)
+        out.add(PacketRegistry.decode(msg,
+            handler.data.frontVer ?: 0,
+            handler.data.state.state, handler.frontEnd))
+        if (msg.isReadable) throw IllegalStateException("Remaining bytes!!!")
+    }
+}
+
 class CloudCrypto(val cipherDecode: Cipher, var cipherEncode: Cipher) : MessageToMessageCodec<ByteBuf, ByteBuf>() {
     override fun decode(ctx: ChannelHandlerContext, msg: ByteBuf, out: MutableList<Any>) {
         val i = msg.readerIndex()
@@ -130,9 +156,9 @@ class CloudCompressionCodec(val threshold: Int) : MessageToMessageCodec<ByteBuf,
 
 }
 
-class FrameCodec : ByteToMessageCodec<ByteBuf>() {
+val badLength = DecoderException("Invalid length!")
-    val badLength = DecoderException("Invalid length!")
 
+class FrameCodec : ByteToMessageCodec<ByteBuf>() {
     override fun decode(ctx: ChannelHandlerContext, input: ByteBuf, out: MutableList<Any>) {
         if (!ctx.channel().isActive) {
             input.clear() // Ignore, should prevent DoS https://github.com/SpigotMC/BungeeCord/pull/2908

src/main/kotlin/com/github/creeper123123321/viaaas/CloudHandler.kt

@@ -6,7 +6,6 @@ import com.google.gson.Gson
 import com.google.gson.JsonObject
 import io.ktor.client.request.*
 import io.netty.bootstrap.Bootstrap
-import io.netty.buffer.ByteBuf
 import io.netty.buffer.ByteBufAllocator
 import io.netty.channel.*
 import io.netty.channel.socket.SocketChannel
@@ -14,7 +13,6 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.launch
 import org.slf4j.LoggerFactory
-import us.myles.ViaVersion.api.protocol.ProtocolVersion
 import us.myles.ViaVersion.api.type.Type
 import us.myles.ViaVersion.exception.CancelCodecException
 import us.myles.ViaVersion.packets.State
@@ -26,6 +24,8 @@ import java.security.MessageDigest
 import java.security.PrivateKey
 import java.security.PublicKey
 import java.util.*
+import java.util.UUID
+import java.util.concurrent.CompletableFuture
 import javax.crypto.Cipher
 import javax.crypto.spec.IvParameterSpec
 import javax.crypto.spec.SecretKeySpec
@@ -42,11 +42,6 @@ class ConnectionData(
     var frontOnline: Boolean? = null, // todo
     var frontName: String? = null,
     var backName: String? = null,
-    var backPublicKey: PublicKey? = null,
-    var backToken: ByteArray? = null,
-    var frontToken: ByteArray? = null,
-    var frontServerId: String? = null,
-    var backServerId: String? = null,
     var frontVer: Int? = null,
     var backVer: Int? = null,
 ) {
@@ -58,13 +53,12 @@ class CloudMinecraftHandler(
     val data: ConnectionData,
     var other: Channel?,
     val frontEnd: Boolean
-) : SimpleChannelInboundHandler<ByteBuf>() {
+) : SimpleChannelInboundHandler<Packet>() {
     var remoteAddress: SocketAddress? = null
 
-    override fun channelRead0(ctx: ChannelHandlerContext, msg: ByteBuf) {
+    override fun channelRead0(ctx: ChannelHandlerContext, packet: Packet) {
-        if (ctx.channel().isActive && msg.isReadable) {
+        if (ctx.channel().isActive) {
-            data.state.handleMessage(this, ctx, msg)
+            data.state.handlePacket(this, ctx, packet)
-            if (msg.isReadable) throw IllegalStateException("Remaining bytes!!!")
         }
     }
 
@@ -97,9 +91,10 @@ class CloudMinecraftHandler(
 }
 
 interface MinecraftConnectionState {
-    fun handleMessage(
+    val state: State
+    fun handlePacket(
         handler: CloudMinecraftHandler, ctx: ChannelHandlerContext,
-        msg: ByteBuf
+        packet: Packet
     )
 
     fun disconnect(handler: CloudMinecraftHandler, msg: String) {
@@ -112,19 +107,27 @@ interface MinecraftConnectionState {
 }
 
 class HandshakeState : MinecraftConnectionState {
-    override fun handleMessage(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, msg: ByteBuf) {
+    fun connectBack(handler: CloudMinecraftHandler, socketAddr: InetSocketAddress): ChannelFuture {
-        val packet = PacketRegistry.decode(
+        return Bootstrap()
-            msg,
+            .handler(BackendInit(handler.data))
-            ProtocolVersion.v1_8, // we still dont know what protocol it is
+            .channelFactory(channelSocketFactory())
-            State.HANDSHAKE,
+            .group(handler.data.frontChannel.eventLoop())
-            handler.frontEnd
+            .option(ChannelOption.IP_TOS, 0x18)
-        )
+            .option(ChannelOption.TCP_NODELAY, true)
+            .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 15_000) // Half of mc timeout
+            .connect(socketAddr)
+    }
+
+    override val state: State
+        get() = State.HANDSHAKE
+
+    override fun handlePacket(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, packet: Packet) {
         if (packet !is HandshakePacket) throw IllegalArgumentException("Invalid packet!")
 
         handler.data.frontVer = packet.protocolId
         when (packet.nextState.ordinal) {
             1 -> handler.data.state = StatusState
-            2 -> handler.data.state = LoginState
+            2 -> handler.data.state = LoginState()
             else -> throw IllegalStateException("Invalid next state")
         }
 
@@ -161,22 +164,18 @@ class HandshakeState : MinecraftConnectionState {
 
                 if (checkLocalAddress(socketAddr.address)
                     || matchesAddress(socketAddr, VIAaaSConfig.blockedBackAddresses)
-                    || !matchesAddress(socketAddr, VIAaaSConfig.allowedBackAddresses)) {
+                    || !matchesAddress(socketAddr, VIAaaSConfig.allowedBackAddresses)
+                ) {
                     throw SecurityException("Not allowed")
                 }
 
-                val bootstrap = Bootstrap()
+                val future = connectBack(handler, socketAddr)
-                    .handler(BackendInit(handler.data))
-                    .channelFactory(channelSocketFactory())
-                    .group(handler.data.frontChannel.eventLoop())
-                    .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 15_000) // Half of mc timeout
-                    .connect(socketAddr)
 
-                bootstrap.addListener {
+                future.addListener {
                     if (it.isSuccess) {
                         mcLogger.info("Connected ${handler.remoteAddress} -> $socketAddr")
 
-                        val backChan = bootstrap.channel() as SocketChannel
+                        val backChan = future.channel() as SocketChannel
                         handler.data.backChannel = backChan
                         handler.other = backChan
 
@@ -205,15 +204,14 @@ class HandshakeState : MinecraftConnectionState {
     }
 }
 
-object LoginState : MinecraftConnectionState {
+class LoginState : MinecraftConnectionState {
-    override fun handleMessage(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, msg: ByteBuf) {
+    val callbackPlayerId = CompletableFuture<String>()
-        val packet = PacketRegistry.decode(
+    lateinit var frontToken: ByteArray
-            msg,
+    lateinit var frontServerId: String
-            ProtocolVersion.getProtocol(handler.data.frontVer!!),
+    override val state: State
-            State.LOGIN,
+        get() = State.LOGIN
-            handler.frontEnd
-        )
 
+    override fun handlePacket(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, packet: Packet) {
         when (packet) {
             is LoginStart -> handleLoginStart(handler, packet)
             is CryptoResponse -> handleCryptoResponse(handler, packet)
@@ -253,12 +251,7 @@ object LoginState : MinecraftConnectionState {
         }
     }
 
-    fun handleCryptoRequest(handler: CloudMinecraftHandler, cryptoRequest: CryptoRequest) {
+    fun authenticateOnlineFront(frontHandler: CloudMinecraftHandler) {
-        val data = handler.data
-        data.backServerId = cryptoRequest.serverId
-        data.backPublicKey = cryptoRequest.publicKey
-        data.backToken = cryptoRequest.token
-
         val id = "VIAaaS" + ByteArray(10).let {
             secureRandom.nextBytes(it)
             Base64.getEncoder().withoutPadding().encodeToString(it)
@@ -269,14 +262,66 @@ object LoginState : MinecraftConnectionState {
             secureRandom.nextBytes(it)
             it
         }
-        data.frontToken = token
+        frontToken = token
-        data.frontServerId = id
+        frontServerId = id
 
+        val cryptoRequest = CryptoRequest()
         cryptoRequest.serverId = id
         cryptoRequest.publicKey = mcCryptoKey.public
         cryptoRequest.token = token
 
-        forward(handler, cryptoRequest)
+        frontHandler.data.frontChannel.writeAndFlush(cryptoRequest)
+    }
+
+    fun handleCryptoRequest(handler: CloudMinecraftHandler, cryptoRequest: CryptoRequest) {
+        val data = handler.data
+        val backServerId = cryptoRequest.serverId
+        val backPublicKey = cryptoRequest.publicKey
+        val backToken = cryptoRequest.token
+
+        if (data.frontOnline == null) {
+            authenticateOnlineFront(handler)
+        }
+
+        val backKey = ByteArray(16).let {
+            secureRandom.nextBytes(it)
+            it
+        }
+        val backHash = generateServerHash(backServerId, backKey, backPublicKey)
+
+        callbackPlayerId.whenComplete { playerId, e ->
+            if (e != null) return@whenComplete
+            val frontHandler = handler.data.frontHandler
+            GlobalScope.launch(Dispatchers.IO) {
+                try {
+                    val sessionJoin = viaWebServer.requestSessionJoin(
+                        parseUndashedId(playerId),
+                        handler.data.backName!!,
+                        backHash,
+                        frontHandler.remoteAddress!!, // Frontend handler
+                        backPublicKey
+                    )
+
+                    val backChan = handler.data.backChannel!!
+                    sessionJoin.whenCompleteAsync({ _, throwable ->
+                        if (throwable != null) {
+                            frontHandler.data.backHandler!!.disconnect("Online mode error: $throwable")
+                        } else {
+                            val cryptoResponse = CryptoResponse()
+                            cryptoResponse.encryptedKey = encryptRsa(backPublicKey, backKey)
+                            cryptoResponse.encryptedToken = encryptRsa(backPublicKey, backToken)
+                            forward(frontHandler, cryptoResponse, true)
+
+                            val backAesEn = mcCfb8(backKey, Cipher.ENCRYPT_MODE)
+                            val backAesDe = mcCfb8(backKey, Cipher.DECRYPT_MODE)
+                            backChan.pipeline().addBefore("frame", "crypto", CloudCrypto(backAesDe, backAesEn))
+                        }
+                    }, backChan.eventLoop())
+                } catch (e: Exception) {
+                    frontHandler.disconnect("Online mode error: $e")
+                }
+            }
+        }
     }
 
     fun handleCryptoResponse(handler: CloudMinecraftHandler, cryptoResponse: CryptoResponse) {
@@ -285,23 +330,16 @@ object LoginState : MinecraftConnectionState {
             // RSA token - wat??? why is it encrypted with RSA if it was sent unencrypted?
             val decryptedToken = decryptRsa(mcCryptoKey.private, cryptoResponse.encryptedToken)
 
-            if (!decryptedToken.contentEquals(handler.data.frontToken!!)) throw IllegalStateException("invalid token!")
+            if (!decryptedToken.contentEquals(frontToken)) throw IllegalStateException("invalid token!")
 
             val aesEn = mcCfb8(frontKey, Cipher.ENCRYPT_MODE)
             val aesDe = mcCfb8(frontKey, Cipher.DECRYPT_MODE)
 
             handler.data.frontChannel.pipeline().addBefore("frame", "crypto", CloudCrypto(aesDe, aesEn))
 
-            generateServerHash(handler.data.frontServerId!!, frontKey, mcCryptoKey.public)
+            generateServerHash(frontServerId, frontKey, mcCryptoKey.public)
         }
 
-        val backKey = ByteArray(16).let {
-            secureRandom.nextBytes(it)
-            it
-        }
-
-        val backHash = generateServerHash(handler.data.backServerId!!, backKey, handler.data.backPublicKey!!)
-
         handler.data.frontChannel.setAutoRead(false)
         GlobalScope.launch(Dispatchers.IO) {
             try {
@@ -309,45 +347,40 @@ object LoginState : MinecraftConnectionState {
                     "https://sessionserver.mojang.com/session/minecraft/hasJoined?username=" +
                             UrlEscapers.urlFormParameterEscaper().escape(handler.data.frontName!!) +
                             "&serverId=$frontHash"
-                )
+                ) ?: throw IllegalArgumentException("Couldn't authenticate with session servers")
-                    ?: throw IllegalArgumentException("Couldn't authenticate with session servers")
 
-                val sessionJoin = viaWebServer.requestSessionJoin(
+                val id = profile.get("id")!!.asString
-                    fromUndashed(profile.get("id")!!.asString),
+                mcLogger.info("Validated front-end session: ${handler.data.frontName} $id")
-                    handler.data.backName!!,
+                callbackPlayerId.complete(id)
-                    backHash,
-                    handler.remoteAddress!!, // Frontend handler
-                    handler.data.backPublicKey!!
-                )
-
-                val backChan = handler.other!!
-                sessionJoin.whenCompleteAsync({ _, throwable ->
-                    if (throwable != null) {
-                        handler.disconnect("Online mode error: $throwable")
-                    } else {
-                        cryptoResponse.encryptedKey = encryptRsa(handler.data.backPublicKey!!, backKey)
-                        cryptoResponse.encryptedToken =
-                            encryptRsa(handler.data.backPublicKey!!, handler.data.backToken!!)
-                        forward(handler, cryptoResponse, true)
-
-                        val backAesEn = mcCfb8(backKey, Cipher.ENCRYPT_MODE)
-                        val backAesDe = mcCfb8(backKey, Cipher.DECRYPT_MODE)
-                        backChan.pipeline().addBefore("frame", "crypto", CloudCrypto(backAesDe, backAesEn))
-                    }
-                }, backChan.eventLoop())
             } catch (e: Exception) {
-                handler.disconnect("Online mode error: $e")
+                callbackPlayerId.completeExceptionally(e)
             }
             handler.data.frontChannel.setAutoRead(true)
         }
     }
 
     fun handleLoginStart(handler: CloudMinecraftHandler, loginStart: LoginStart) {
+        if (loginStart.username.length > 16) throw badLength
+
         handler.data.frontName = loginStart.username
         handler.data.backName = handler.data.backName ?: handler.data.frontName
 
         loginStart.username = handler.data.backName!!
-        forward(handler, loginStart)
+
+        callbackPlayerId.whenComplete { _, e -> if (e != null) disconnect(handler, "Profile error: $e") }
+
+        if (handler.data.frontOnline == false) {
+            callbackPlayerId.complete(generateOfflinePlayerUuid(handler.data.frontName!!).toString().replace("-", ""))
+        }
+
+        if (handler.data.frontOnline == true) { // forced
+            authenticateOnlineFront(handler.data.backHandler!!)
+            callbackPlayerId.whenComplete { _, e ->
+                if (e == null) forward(handler, loginStart, true)
+            }
+        } else {
+            forward(handler, loginStart)
+        }
     }
 
     override fun disconnect(handler: CloudMinecraftHandler, msg: String) {
@@ -367,12 +400,12 @@ object LoginState : MinecraftConnectionState {
 }
 
 object StatusState : MinecraftConnectionState {
-    override fun handleMessage(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, msg: ByteBuf) {
+    override val state: State
-        val i = msg.readerIndex()
+        get() = State.STATUS
-        if (Type.VAR_INT.readPrimitive(msg) !in 0..1) throw IllegalArgumentException("Invalid packet id!")
+
-        msg.readerIndex(i)
+    override fun handlePacket(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, packet: Packet) {
-        forward(handler, msg.retainedSlice())
+        if ((packet as UnknownPacket).id !in 0..1) throw IllegalArgumentException("Invalid packet id!")
-        msg.clear()
+        forward(handler, packet)
     }
 
     override fun disconnect(handler: CloudMinecraftHandler, msg: String) {
@@ -394,12 +427,12 @@ object StatusState : MinecraftConnectionState {
 }
 
 object PlayState : MinecraftConnectionState {
-    override fun handleMessage(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, msg: ByteBuf) {
+    override val state: State
-        val i = msg.readerIndex()
+        get() = State.PLAY
-        if (Type.VAR_INT.readPrimitive(msg) !in 0..127) throw IllegalArgumentException("Invalid packet id!")
+
-        msg.readerIndex(i)
+    override fun handlePacket(handler: CloudMinecraftHandler, ctx: ChannelHandlerContext, packet: Packet) {
-        forward(handler, msg.retainedSlice())
+        if ((packet as UnknownPacket).id !in 0..127) throw IllegalArgumentException("Invalid packet id!")
-        msg.clear()
+        forward(handler, packet)
     }
 
     override fun disconnect(handler: CloudMinecraftHandler, msg: String) {
@@ -449,22 +482,17 @@ fun generateServerHash(serverId: String, sharedSecret: ByteArray?, key: PublicKe
 private fun forward(handler: CloudMinecraftHandler, packet: Packet, flush: Boolean = false) {
     val msg = ByteBufAllocator.DEFAULT.buffer()
     try {
-        PacketRegistry.encode(packet, msg, ProtocolVersion.getProtocol(handler.data.frontVer!!))
+        val ch = handler.other!!
-        forward(handler, msg.retain(), flush)
+        if (flush) {
+            ch.writeAndFlush(packet, ch.voidPromise())
+        } else {
+            ch.write(packet, ch.voidPromise())
+        }
     } finally {
         msg.release()
     }
 }
 
-private fun forward(handler: CloudMinecraftHandler, byteBuf: ByteBuf, flush: Boolean = false) {
-    val ch = handler.other!!
-    if (flush) {
-        ch.writeAndFlush(byteBuf, ch.voidPromise())
-    } else {
-        ch.write(byteBuf, ch.voidPromise())
-    }
-}
-
 private fun resolveSrv(address: String, port: Int): Pair<String, Int> {
     if (port == 25565) {
         try {
@@ -509,3 +537,7 @@ private fun matchAddress(addr: String, list: List<String>): Boolean {
         list.contains(query)
     }
 }
+
+// https://github.com/VelocityPowered/Velocity/blob/e3f17eeb245b8d570f16c1f2aff5e7eafb698d5e/api/src/main/java/com/velocitypowered/api/util/UuidUtils.java
+fun generateOfflinePlayerUuid(username: String) =
+    UUID.nameUUIDFromBytes("OfflinePlayer:$username".toByteArray(Charsets.UTF_8))

src/main/kotlin/com/github/creeper123123321/viaaas/CloudPackets.kt

@@ -16,8 +16,8 @@ import kotlin.properties.Delegates
  * A mutable object which represents a Minecraft packet data
  */
 interface Packet {
-    fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion)
+    fun decode(byteBuf: ByteBuf, protocolVersion: Int)
-    fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion)
+    fun encode(byteBuf: ByteBuf, protocolVersion: Int)
 }
 
 object PacketRegistry {
@@ -70,24 +70,24 @@ object PacketRegistry {
     )
 
     fun getPacketConstructor(
-        protocolVersion: ProtocolVersion,
+        protocolVersion: Int,
         state: State,
         id: Int,
         serverBound: Boolean
     ): Supplier<out Packet>? {
         return entries.firstOrNull {
             it.serverBound == serverBound && it.state == state
-                    && it.versionRange.contains(protocolVersion.version) && it.id == id
+                    && it.versionRange.contains(protocolVersion) && it.id == id
         }?.constructor
     }
 
-    fun getPacketId(packetClass: Class<out Packet>, protocolVersion: ProtocolVersion): Int? {
+    fun getPacketId(packetClass: Class<out Packet>, protocolVersion: Int): Int? {
         return entries.firstOrNull {
-            it.versionRange.contains(protocolVersion.version) && it.packetClass == packetClass
+            it.versionRange.contains(protocolVersion) && it.packetClass == packetClass
         }?.id
     }
 
-    fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion, state: State, serverBound: Boolean): Packet {
+    fun decode(byteBuf: ByteBuf, protocolVersion: Int, state: State, serverBound: Boolean): Packet {
         val packetId = Type.VAR_INT.readPrimitive(byteBuf)
         val packet =
             getPacketConstructor(protocolVersion, state, packetId, serverBound)?.get() ?: UnknownPacket(packetId)
@@ -96,7 +96,7 @@ object PacketRegistry {
         return packet
     }
 
-    fun encode(packet: Packet, byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    fun encode(packet: Packet, byteBuf: ByteBuf, protocolVersion: Int) {
         val id = if (packet is UnknownPacket) {
             packet.id
         } else {
@@ -108,13 +108,13 @@ object PacketRegistry {
 }
 
 class UnknownPacket(val id: Int) : Packet {
-    lateinit var content: ByteBuf
+    lateinit var content: ByteArray
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
-        content = byteBuf.slice().clear()
+        content = ByteArray(byteBuf.readableBytes()).also { byteBuf.readBytes(it) }
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         byteBuf.writeBytes(content)
     }
 }
@@ -127,14 +127,14 @@ class HandshakePacket : Packet {
     var port by Delegates.notNull<Int>()
     lateinit var nextState: State
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         protocolId = Type.VAR_INT.readPrimitive(byteBuf)
         address = Type.STRING.read(byteBuf)
         port = byteBuf.readUnsignedShort()
         nextState = State.values()[Type.VAR_INT.readPrimitive(byteBuf)]
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.VAR_INT.writePrimitive(byteBuf, protocolId)
         Type.STRING.write(byteBuf, address)
         byteBuf.writeShort(port)
@@ -145,11 +145,11 @@ class HandshakePacket : Packet {
 class LoginStart : Packet {
     lateinit var username: String
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         username = Type.STRING.read(byteBuf)
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.STRING.write(byteBuf, username)
     }
 }
@@ -158,8 +158,8 @@ class CryptoResponse : Packet {
     lateinit var encryptedKey: ByteArray
     lateinit var encryptedToken: ByteArray
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
-        if (protocolVersion.version >= ProtocolVersion.v1_8.version) {
+        if (protocolVersion >= ProtocolVersion.v1_8.version) {
             encryptedKey = Type.BYTE_ARRAY_PRIMITIVE.read(byteBuf)
             encryptedToken = Type.BYTE_ARRAY_PRIMITIVE.read(byteBuf)
         } else {
@@ -168,8 +168,8 @@ class CryptoResponse : Packet {
         }
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
-        if (protocolVersion.version >= ProtocolVersion.v1_8.version) {
+        if (protocolVersion >= ProtocolVersion.v1_8.version) {
             Type.BYTE_ARRAY_PRIMITIVE.write(byteBuf, encryptedKey)
             Type.BYTE_ARRAY_PRIMITIVE.write(byteBuf, encryptedToken)
         } else {
@@ -184,16 +184,16 @@ class CryptoResponse : Packet {
 class PluginResponse : Packet {
     var id by Delegates.notNull<Int>()
     var success by Delegates.notNull<Boolean>()
-    lateinit var data: ByteBuf
+    lateinit var data: ByteArray
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         id = Type.VAR_INT.readPrimitive(byteBuf)
         success = byteBuf.readBoolean()
         if (success) {
-            data = byteBuf.slice().clear()
+            data = ByteArray(byteBuf.readableBytes()).also { byteBuf.readBytes(it) }
         }
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.VAR_INT.writePrimitive(byteBuf, id)
         byteBuf.writeBoolean(success)
         if (success) {
@@ -204,11 +204,11 @@ class PluginResponse : Packet {
 
 class LoginDisconnect : Packet {
     lateinit var msg: String
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         msg = Type.STRING.read(byteBuf)
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.STRING.write(byteBuf, msg)
     }
 }
@@ -218,9 +218,9 @@ class CryptoRequest : Packet {
     lateinit var publicKey: PublicKey
     lateinit var token: ByteArray
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         serverId = Type.STRING.read(byteBuf)
-        if (protocolVersion.version >= ProtocolVersion.v1_8.version) {
+        if (protocolVersion >= ProtocolVersion.v1_8.version) {
             publicKey = KeyFactory.getInstance("RSA")
                 .generatePublic(X509EncodedKeySpec(Type.BYTE_ARRAY_PRIMITIVE.read(byteBuf)))
             token = Type.BYTE_ARRAY_PRIMITIVE.read(byteBuf)
@@ -231,9 +231,9 @@ class CryptoRequest : Packet {
         }
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.STRING.write(byteBuf, serverId)
-        if (protocolVersion.version >= ProtocolVersion.v1_8.version) {
+        if (protocolVersion >= ProtocolVersion.v1_8.version) {
             Type.BYTE_ARRAY_PRIMITIVE.write(byteBuf, publicKey.encoded)
             Type.BYTE_ARRAY_PRIMITIVE.write(byteBuf, token)
         } else {
@@ -250,25 +250,25 @@ class LoginSuccess : Packet {
     lateinit var id: UUID
     lateinit var username: String
 
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         id = when {
-            protocolVersion.version >= ProtocolVersion.v1_16.version -> {
+            protocolVersion >= ProtocolVersion.v1_16.version -> {
                 Type.UUID_INT_ARRAY.read(byteBuf)
             }
-            protocolVersion.version >= ProtocolVersion.v1_7_6.version -> {
+            protocolVersion >= ProtocolVersion.v1_7_6.version -> {
                 UUID.fromString(Type.STRING.read(byteBuf))
             }
-            else -> fromUndashed(Type.STRING.read(byteBuf))
+            else -> parseUndashedId(Type.STRING.read(byteBuf))
         }
         username = Type.STRING.read(byteBuf)
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         when {
-            protocolVersion.version >= ProtocolVersion.v1_16.version -> {
+            protocolVersion >= ProtocolVersion.v1_16.version -> {
                 Type.UUID_INT_ARRAY.write(byteBuf, id)
             }
-            protocolVersion.version >= ProtocolVersion.v1_7_6.version -> {
+            protocolVersion >= ProtocolVersion.v1_7_6.version -> {
                 Type.STRING.write(byteBuf, id.toString())
             }
             else -> Type.STRING.write(byteBuf, id.toString().replace("-", ""))
@@ -279,11 +279,11 @@ class LoginSuccess : Packet {
 
 class SetCompression : Packet {
     var threshold by Delegates.notNull<Int>()
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         threshold = Type.VAR_INT.readPrimitive(byteBuf)
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.VAR_INT.writePrimitive(byteBuf, threshold)
     }
 }
@@ -291,14 +291,14 @@ class SetCompression : Packet {
 class PluginRequest : Packet {
     var id by Delegates.notNull<Int>()
     lateinit var channel: String
-    lateinit var data: ByteBuf
+    lateinit var data: ByteArray
-    override fun decode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun decode(byteBuf: ByteBuf, protocolVersion: Int) {
         id = Type.VAR_INT.readPrimitive(byteBuf)
         channel = Type.STRING.read(byteBuf)
-        data = byteBuf.slice().clear()
+        data = ByteArray(byteBuf.readableBytes()).also { byteBuf.readBytes(it) }
     }
 
-    override fun encode(byteBuf: ByteBuf, protocolVersion: ProtocolVersion) {
+    override fun encode(byteBuf: ByteBuf, protocolVersion: Int) {
         Type.VAR_INT.writePrimitive(byteBuf, id)
         Type.STRING.write(byteBuf, channel)
         byteBuf.writeBytes(data)

src/main/kotlin/com/github/creeper123123321/viaaas/ViaWeb.kt

@@ -4,20 +4,15 @@ import com.google.common.base.Preconditions
 import com.google.common.cache.CacheBuilder
 import com.google.common.cache.CacheLoader
 import com.google.gson.Gson
-import com.google.gson.JsonArray
 import com.google.gson.JsonObject
 import io.ktor.application.*
-import io.ktor.client.features.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.*
 import io.ktor.features.*
 import io.ktor.http.*
 import io.ktor.http.cio.websocket.*
 import io.ktor.http.content.*
-import io.ktor.request.*
-import io.ktor.response.*
 import io.ktor.routing.*
-import io.ktor.util.*
 import io.ktor.websocket.*
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.channels.consumeEach
@@ -61,7 +56,7 @@ class ViaWebApp {
                         }
                     }
                 } catch (e: Exception) {
-                    e.printStackTrace()
+                    webLogger.info("${call.request.local.remoteHost} (O: ${call.request.origin.remoteHost}) exception: $e")
                     viaWebServer.onException(this, e)
                     this.close(CloseReason(CloseReason.Codes.INTERNAL_ERROR, "INTERNAL ERROR"))
                 } finally {
@@ -78,7 +73,7 @@ class ViaWebApp {
 }
 
 // https://github.com/VelocityPowered/Velocity/blob/6467335f74a7d1617512a55cc9acef5e109b51ac/api/src/main/java/com/velocitypowered/api/util/UuidUtils.java
-fun fromUndashed(string: String): UUID {
+fun parseUndashedId(string: String): UUID {
     Preconditions.checkArgument(string.length == 32, "Length is incorrect")
     return UUID(
         java.lang.Long.parseUnsignedLong(string.substring(0, 16), 16),
@@ -100,7 +95,7 @@ class WebDashboardServer {
             runBlocking {
                 withContext(Dispatchers.IO) {
                     httpClient.get<JsonObject?>("https://api.mojang.com/users/profiles/minecraft/$name")
-                        ?.get("id")?.asString?.let { fromUndashed(it) }
+                        ?.get("id")?.asString?.let { parseUndashedId(it) }
                 }
             }
         })
@@ -184,9 +179,23 @@ class WebLogin : WebState {
         val obj = Gson().fromJson(msg, JsonObject::class.java)
 
         when (obj.getAsJsonPrimitive("action").asString) {
+            "offline_login" -> {
+                // todo add some spam check
+                val username = obj.get("username").asString
+                val token = UUID.randomUUID()
+                val uuid = generateOfflinePlayerUuid(username)
+
+                webClient.server.loginTokens.put(token, uuid)
+                webClient.ws.send(
+                    """{"action": "login_result", "success": true,
+                        | "username": "$username", "uuid": "$uuid", "token": "$token"}""".trimMargin()
+                )
+
+                webLogger.info("${webClient.ws.call.request.local.remoteHost} (O: ${webClient.ws.call.request.origin.remoteHost}) generated a token for offline account $username")
+            }
             "minecraft_id_login" -> {
-                val username = obj.getAsJsonPrimitive("username").asString
+                val username = obj.get("username").asString
-                val code = obj.getAsJsonPrimitive("code").asString
+                val code = obj.get("code").asString
 
                 val check = httpClient.submitForm<JsonObject>(
                     "https://api.minecraft.id/gateway/verify/${URLEncoder.encode(username, Charsets.UTF_8)}",
@@ -200,13 +209,13 @@ class WebLogin : WebState {
 
                     webClient.server.loginTokens.put(token, uuid)
                     webClient.ws.send(
-                        """{"action": "minecraft_id_result", "success": true,
+                        """{"action": "login_result", "success": true,
                         | "username": "$mcIdUser", "uuid": "$uuid", "token": "$token"}""".trimMargin()
                     )
 
                     webLogger.info("${webClient.ws.call.request.local.remoteHost} (O: ${webClient.ws.call.request.origin.remoteHost}) generated a token for account $mcIdUser $uuid")
                 } else {
-                    webClient.ws.send("""{"action": "minecraft_id_result", "success": false}""")
+                    webClient.ws.send("""{"action": "login_result", "success": false}""")
                     webLogger.info("${webClient.ws.call.request.local.remoteHost} (O: ${webClient.ws.call.request.origin.remoteHost})  failed to generated a token for account $username")
                 }
             }

src/main/resources/web/auth.js

@@ -219,44 +219,48 @@ function renderActions() {
     actions.innerHTML = "";
     if (listenVisible) {
         if (username != null && mcauth_code != null) {
-            let p = document.createElement("p");
+            addAction("Listen to " + username, () => {
-            let add = document.createElement("a");
-            p.appendChild(add);
-            add.innerText = "Listen to " + username;
-            add.href = "#";
-            add.onclick = () => {
                 socket.send(JSON.stringify({
                     "action": "minecraft_id_login",
                     "username": username,
                     "code": mcauth_code}));
                 mcauth_code = null;
-            };
+            });
-            actions.appendChild(p);
         }
-        let p = document.createElement("p");
+        addAction("Listen to premium login in VIAaaS instance", () => {
-        let link = document.createElement("a");
+            let user = prompt("Premium username (case-sensitive): ", "");
-        p.appendChild(link);
-        link.innerText = "Listen to username in VIAaaS instance";
-        link.href = "#";
-        link.onclick = () => {
-            let user = prompt("Username (Minecraft.ID is case-sensitive): ", "");
             if (!user) return;
             let callbackUrl = new URL(location.origin + location.pathname + "#username=" + encodeURIComponent(user));
-            location = "https://api.minecraft.id/gateway/start/" + encodeURIComponent(user) + "?callback=" + encodeURIComponent(callbackUrl);
+            location = "https://api.minecraft.id/gateway/start/" + encodeURIComponent(user)
-        };
+                + "?callback=" + encodeURIComponent(callbackUrl);
-        actions.appendChild(p);
+        });
+        addAction("Listen to offline login in VIAaaS instance", () => {
+            let user = prompt("Offline username (case-sensitive):", "");
+            if (!user) return;
+            socket.send(JSON.stringify({"action": "offline_login", "username": user}));
+        });
     }
 }
 
+function addAction(text, onClick) {
+    let p = document.createElement("p");
+    let link = document.createElement("a");
+    p.appendChild(link);
+    link.innerText = text;
+    link.href = "#";
+    link.onclick = onClick;
+    actions.appendChild(p);
+}
+
 function onSocketMsg(event) {
     console.log(event.data.toString());
     let parsed = JSON.parse(event.data);
     if (parsed.action == "ad_minecraft_id_login") {
         listenVisible = true;
         renderActions();
-    } else if (parsed.action == "minecraft_id_result") {
+    } else if (parsed.action == "login_result") {
         if (!parsed.success) {
-            alert("VIAaaS instance couldn't verify account via Minecraft.ID");
+            alert("VIAaaS instance couldn't verify Minecraft account");
         } else {
             listen(parsed.token);
             saveToken(parsed.token);