From 887a82564f4809bd4b1d5fc10442d5844a00cd5a Mon Sep 17 00:00:00 2001
From: Verox001 <verox@cimeyclust.com>
Date: Fri, 21 Feb 2025 18:20:43 +0100
Subject: [PATCH] Added LoginStart. Doesn't work yet though

---
 main.go | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 84 insertions(+), 5 deletions(-)

diff --git a/main.go b/main.go
index de3a2cc..9dccd7e 100644
--- a/main.go
+++ b/main.go
@@ -18,6 +18,11 @@ const (
 	PongResponseID    = 0x01
 )
 
+type PrefixedByteArray struct {
+	Length int
+	Data   []byte
+}
+
 type HandshakePacket struct {
 	ProtocolVersion int
 	ServerAddress   string
@@ -25,6 +30,11 @@ type HandshakePacket struct {
 	NextState       int
 }
 
+type LoginStartPacket struct {
+	SharedSecret PrefixedByteArray
+	VerifyToken  PrefixedByteArray
+}
+
 type StatusResponse struct {
 	Version     VersionInfo `json:"version"`
 	Players     PlayerInfo  `json:"players"`
@@ -42,10 +52,6 @@ type PlayerInfo struct {
 	Sample []Player `json:"sample"`
 }
 
-type Pong struct {
-	Timestamp int64 `json:"timestamp"`
-}
-
 type Player struct {
 	Name string `json:"name"`
 	ID   string `json:"id"`
@@ -129,8 +135,40 @@ func handleConnection(client *ClientState) {
 			if client.nextState == 1 {
 				handleStatusRequest(client)
 			} else if client.nextState == 2 {
-				fmt.Println("Received status request in the wrong state")
+				fmt.Println("Received Login Start")
+
+				// Login Start
+				loginStart, err := handleLoginStart(packetReader)
+				if err != nil {
+					fmt.Println("Error processing login start:", err)
+					return
+				}
+				fmt.Println("Login Start:", loginStart)
+
+				// Send Encryption Request back
+				var packetData bytes.Buffer
+				writeVarInt(&packetData, 1) // Packet length: 1 byte for ID
+				packetData.WriteByte(0x01)  // Encryption Request ID
+
+				// Server ID
+				writeString(&packetData, "JustAnotherServer")
+
+				// Public Key
+				writePrefixedByteArray(&packetData, PrefixedByteArray{Length: 0, Data: []byte{}})
+
+				// Verify Token
+				writePrefixedByteArray(&packetData, PrefixedByteArray{Length: 0, Data: []byte{}})
+
+				// Should authenticate (actually a boolean)
+				packetData.WriteByte(1)
+
+				if _, err := client.conn.Write(packetData.Bytes()); err != nil {
+					fmt.Println("Error sending encryption request:", err)
+				} else {
+					fmt.Println("Encryption request sent successfully")
+				}
 			} else if client.nextState == 3 {
+				// Transfer
 				fmt.Println("Received status request in the wrong state")
 			} else {
 				handshake, err := handleHandshake(packetReader)
@@ -188,6 +226,24 @@ func handleHandshake(reader *bytes.Reader) (HandshakePacket, error) {
 	return handshake, nil
 }
 
+func handleLoginStart(reader *bytes.Reader) (LoginStartPacket, error) {
+	var packet LoginStartPacket
+	var err error
+
+	packet.SharedSecret, err = readPrefixedByteArray(reader)
+	if err != nil {
+		return packet, err
+	}
+
+	packet.VerifyToken, err = readPrefixedByteArray(reader)
+	if err != nil {
+		return packet, err
+	}
+
+	fmt.Printf("Login Start received: %+v\n", packet)
+	return packet, nil
+}
+
 func handleStatusRequest(client *ClientState) {
 	status := StatusResponse{
 		Version:     VersionInfo{"1.21.4", 769},
@@ -233,6 +289,16 @@ func writeVarInt(buf *bytes.Buffer, value int) {
 	}
 }
 
+func writeString(buf *bytes.Buffer, value string) {
+	writeVarInt(buf, len(value))
+	buf.WriteString(value)
+}
+
+func writePrefixedByteArray(buf *bytes.Buffer, value PrefixedByteArray) {
+	writeVarInt(buf, value.Length)
+	buf.Write(value.Data)
+}
+
 func readVarInt(reader *bytes.Reader) (int, error) {
 	value, position := 0, 0
 	for {
@@ -264,3 +330,16 @@ func readString(reader *bytes.Reader) (string, error) {
 	}
 	return string(strBuf), nil
 }
+
+func readPrefixedByteArray(reader *bytes.Reader) (PrefixedByteArray, error) {
+	length, err := readVarInt(reader)
+	if err != nil {
+		return PrefixedByteArray{}, err
+	}
+
+	data := make([]byte, length)
+	if _, err := reader.Read(data); err != nil {
+		return PrefixedByteArray{}, err
+	}
+	return PrefixedByteArray{Length: length, Data: data}, nil
+}