Add seed exchange support with modified global-metadata (Grasscutters#9)

## Description

Please carefully read the [Contributing note](https://github.com/Grasscutters/Grasscutter/blob/stable/CONTRIBUTING.md) and [Code of conduct](https://github.com/Grasscutters/Grasscutter/blob/development/CODE_OF_CONDUCT.md) before making any pull requests.
And, **Do not make a pull request to merge into stable unless it is a hotfix. Use the development branch instead.**
## Issues fixed by this PR

<!--- Put the links of issues that may be fixed by this PR here (if any). -->
## Type of changes

<!--- Put an `x` in all the boxes that apply your changes. -->

- [ ] Bug fix
- [x] New feature
- [x] Enhancement
- [ ] Documentation

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] My pull request is unique and no other pull requests have been opened for these changes
- [x] I have read the [Contributing note](https://github.com/Grasscutters/Grasscutter/blob/stable/CONTRIBUTING.md) and [Code of conduct](https://github.com/Grasscutters/Grasscutter/blob/development/CODE_OF_CONDUCT.md)
- [x] I am responsible for any copyright issues with my code if it occurs in the future.

Co-authored-by: ayy lmao <ridvan-nuri@windowslive.com>
Co-authored-by: Benj <benjamin7006@gmail.com>
Reviewed-on: https://git.4benj.com/Grasscutter-Backrooms/Grasscutter/pulls/9

proto/GetPlayerTokenReq.proto

@@ -29,4 +29,7 @@ message GetPlayerTokenReq {
 	string psn_id = 5;
 	string client_ip_str = 6;
 	string birthday = 966;
+	uint32 unk1 = 1883;
+	string client_seed = 924;
+	uint32 key_id = 550;
 }

proto/GetPlayerTokenRsp.proto

@@ -37,4 +37,10 @@ message GetPlayerTokenRsp {
 	uint32 reg_platform = 633;
 	string client_ip_str = 1238;
 	string birthday = 1109;
+	uint32 unk1 = 1728;
+	bool unk2 = 1679;
+	repeated uint32 unk3 = 2012;
+	string encrypted_seed = 1596;
+	string seed_signature = 1501;
+	uint32 unk6 = 1447;
 }

src/main/java/emu/grasscutter/net/packet/BasePacket.java

@@ -10,131 +10,126 @@
 public class BasePacket {
 	private static final int const1 = 17767; // 0x4567
 	private static final int const2 = -30293; // 0x89ab
-	
+
 	private int opcode;
 	private boolean shouldBuildHeader = false;
 
 	private byte[] header;
 	private byte[] data;
-	
+
 	// Encryption
 	private boolean useDispatchKey;
 	public boolean shouldEncrypt = true;
-	
+
 	public BasePacket(int opcode) {
 		this.opcode = opcode;
 	}
-	
+
 	public BasePacket(int opcode, int clientSequence) {
 		this.opcode = opcode;
 		this.buildHeader(clientSequence);
 	}
-	
+
 	public BasePacket(int opcode, boolean buildHeader) {
 		this.opcode = opcode;
 		this.shouldBuildHeader = buildHeader;
 	}
 
 	public int getOpcode() {
-		return opcode;
+		return this.opcode;
 	}
 
 	public void setOpcode(int opcode) {
 		this.opcode = opcode;
 	}
 
 	public boolean useDispatchKey() {
-		return useDispatchKey;
+		return this.useDispatchKey;
 	}
 
 	public void setUseDispatchKey(boolean useDispatchKey) {
 		this.useDispatchKey = useDispatchKey;
 	}
 
 	public byte[] getHeader() {
-		return header;
+		return this.header;
 	}
 
 	public void setHeader(byte[] header) {
 		this.header = header;
 	}
 
 	public boolean shouldBuildHeader() {
-		return shouldBuildHeader;
+		return this.shouldBuildHeader;
 	}
 
 	public byte[] getData() {
-		return data;
+		return this.data;
 	}
 
 	public void setData(byte[] data) {
 		this.data = data;
 	}
-	
+
 	public void setData(GeneratedMessageV3 proto) {
 		this.data = proto.toByteArray();
 	}
-	
+
 	@SuppressWarnings("rawtypes")
 	public void setData(GeneratedMessageV3.Builder proto) {
 		this.data = proto.build().toByteArray();
 	}
-	
+
 	public BasePacket buildHeader(int clientSequence) {
 		if (this.getHeader() != null && clientSequence == 0) {
 			return this;
 		}
-		setHeader(PacketHead.newBuilder().setClientSequenceId(clientSequence).setTimestamp(System.currentTimeMillis()).build().toByteArray());
+		this.setHeader(PacketHead.newBuilder().setClientSequenceId(clientSequence).setTimestamp(System.currentTimeMillis()).build().toByteArray());
 		return this;
 	}
-	
+
 	public byte[] build() {
-		if (getHeader() == null) {
+		if (this.getHeader() == null) {
 			this.header = new byte[0];
 		}
-		
-		if (getData() == null) {
+
+		if (this.getData() == null) {
 			this.data = new byte[0];
 		}
-		
-		ByteArrayOutputStream baos = new ByteArrayOutputStream(2 + 2 + 2 + 4 + getHeader().length + getData().length + 2);
-		
+
+		ByteArrayOutputStream baos = new ByteArrayOutputStream(2 + 2 + 2 + 4 + this.getHeader().length + this.getData().length + 2);
+
 		this.writeUint16(baos, const1);
-		this.writeUint16(baos, opcode);
-		this.writeUint16(baos, header.length);
-		this.writeUint32(baos, data.length);
-		this.writeBytes(baos, header);
-		this.writeBytes(baos, data);
+		this.writeUint16(baos, this.opcode);
+		this.writeUint16(baos, this.header.length);
+		this.writeUint32(baos, this.data.length);
+		this.writeBytes(baos, this.header);
+		this.writeBytes(baos, this.data);
 		this.writeUint16(baos, const2);
-		
+
 		byte[] packet = baos.toByteArray();
 
-		if (this.shouldEncrypt) {
-			if(this.useDispatchKey()) {
-				Crypto.xor(packet, Crypto.DISPATCH_KEY, true);
-			}
-			else {
-				Crypto.xor(packet, Crypto.ENCRYPT_KEY, false);
-			}
-		}
+        if (this.shouldEncrypt) {
+            Crypto.xor(packet, this.useDispatchKey() ? Crypto.DISPATCH_KEY : Crypto.ENCRYPT_KEY);
+        }
 
 		return packet;
 	}
-	
+
 	public void writeUint16(ByteArrayOutputStream baos, int i) {
 		// Unsigned short
         baos.write((byte) ((i >>> 8) & 0xFF));
         baos.write((byte) (i & 0xFF));
     }
-	
+
 	public void writeUint32(ByteArrayOutputStream baos, int i) {
     	// Unsigned int (long)
         baos.write((byte) ((i >>> 24) & 0xFF));
         baos.write((byte) ((i >>> 16) & 0xFF));
         baos.write((byte) ((i >>> 8) & 0xFF));
         baos.write((byte) (i & 0xFF));
     }
-	
+
 	public void writeBytes(ByteArrayOutputStream baos, byte[] bytes) {
     	try {
 			baos.write(bytes);
@@ -143,4 +138,4 @@ public void writeBytes(ByteArrayOutputStream baos, byte[] bytes) {
 			e.printStackTrace();
 		}
     }
-}
+}

src/main/java/emu/grasscutter/server/game/GameSession.java

@@ -186,9 +186,9 @@ public void onConnected(GameSessionManager.KcpTunnel tunnel) {
 
 	@Override
 	public void handleReceive(byte[] bytes) {
-		// Decrypt and turn back into a packet
-		Crypto.xor(bytes, useSecretKey() ? Crypto.ENCRYPT_KEY : Crypto.DISPATCH_KEY);
-		ByteBuf packet = Unpooled.wrappedBuffer(bytes);
+        // Decrypt and turn back into a packet
+        Crypto.xor(bytes, useSecretKey() ? Crypto.ENCRYPT_KEY : Crypto.DISPATCH_KEY);
+        ByteBuf packet = Unpooled.wrappedBuffer(bytes);
 
 		// Log
 		//logPacket(packet);

src/main/java/emu/grasscutter/server/http/dispatch/RegionHandler.java

@@ -1,11 +1,9 @@
 package emu.grasscutter.server.http.dispatch;
 
 import com.google.protobuf.ByteString;
-import com.google.protobuf.InvalidProtocolBufferException;
 import emu.grasscutter.Grasscutter;
 import emu.grasscutter.Grasscutter.ServerRunMode;
-import emu.grasscutter.net.proto.QueryCurrRegionHttpRspOuterClass.*;
-import emu.grasscutter.net.proto.RegionInfoOuterClass;
+import emu.grasscutter.net.proto.QueryCurrRegionHttpRspOuterClass.QueryCurrRegionHttpRsp;
 import emu.grasscutter.net.proto.RegionInfoOuterClass.RegionInfo;
 import emu.grasscutter.net.proto.RegionSimpleInfoOuterClass.RegionSimpleInfo;
 import emu.grasscutter.server.event.dispatch.QueryAllRegionsEvent;
@@ -21,17 +19,19 @@
 import io.javalin.Javalin;
 
 import javax.crypto.Cipher;
-import java.io.File;
-import java.io.StringReader;
-import java.nio.charset.Charset;
-import java.security.*;
+import java.io.ByteArrayOutputStream;
+import java.security.KeyFactory;
+import java.security.PrivateKey;
+import java.security.PublicKey;
 import java.security.spec.PKCS8EncodedKeySpec;
 import java.security.spec.X509EncodedKeySpec;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
+import java.security.Signature;
+
 
 import static emu.grasscutter.Configuration.*;
-import static emu.grasscutter.net.proto.QueryRegionListHttpRspOuterClass.*;
+import static emu.grasscutter.net.proto.QueryRegionListHttpRspOuterClass.QueryRegionListHttpRsp;
 
 /**
  * Handles requests related to region queries.
@@ -85,8 +85,7 @@ private void initialize() {
             // Create a region info object.
             var regionInfo = RegionInfo.newBuilder()
                     .setGateserverIp(region.Ip).setGateserverPort(region.Port)
-                    //.setSecretKey(ByteString.copyFrom(Crypto.DISPATCH_SEED))
-                    .setSecretKey(ByteString.copyFrom(new byte[]{0}))
+                    .setSecretKey(ByteString.copyFrom(Crypto.DISPATCH_SEED))
                     .build();
             // Create an updated region query.
             var updatedQuery = QueryCurrRegionHttpRsp.newBuilder().setRegionInfo(regionInfo).build();
@@ -95,7 +94,7 @@ private void initialize() {
 
         // Create a config object.
         byte[] customConfig = "{\"sdkenv\":\"2\",\"checkdevice\":\"false\",\"loadPatch\":\"false\",\"showexception\":\"false\",\"regionConfig\":\"pm|fk|add\",\"downloadMode\":\"0\"}".getBytes();
-        Crypto.xor(customConfig, Crypto.DISPATCH_KEY, false); // XOR the config with the key.
+        Crypto.xor(customConfig, Crypto.DISPATCH_KEY); // XOR the config with the key.
 
         // Create an updated region list.
         QueryRegionListHttpRsp updatedRegionList = QueryRegionListHttpRsp.newBuilder()
@@ -144,28 +143,39 @@ private static void queryCurrentRegion(Request request, Response response) {
 
         if( versionName.contains("2.7.5") || versionName.contains("2.8.")) {
             try {
-                var key = FileUtils.readResource("/keys/" + (versionName.contains("OSCB") ? "OSCB_Pub.der" : "OSCN_Pub.der") );
-
-                KeyFactory keyFactory = KeyFactory.getInstance("RSA");
-                X509EncodedKeySpec  keySpec = new X509EncodedKeySpec(key);
-                PublicKey pub_key = keyFactory.generatePublic(keySpec);
-
                 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
-                cipher.init(Cipher.ENCRYPT_MODE, pub_key);
+                cipher.init(Cipher.ENCRYPT_MODE, versionName.contains("OSCB") ? Crypto.CUR_OSCB_ENCRYPT_KEY : Crypto.CUR_OSCN_ENCRYPT_KEY);
 
                 QueryCurrentRegionEvent event = new QueryCurrentRegionEvent(regionData); event.call();
-                var regionInfo = event.getRegionInfo();
+                var regionInfo = Utils.base64Decode(event.getRegionInfo());
+
+                //Encrypt regionInfo in chunks
+                ByteArrayOutputStream encryptedRegionInfoStream = new ByteArrayOutputStream();
+
+                //Thank you so much GH Copilot
+                int chunkSize = 256 - 11;
+                int regionInfoLength = regionInfo.length;
+                int numChunks = (int) Math.ceil(regionInfoLength / (double) chunkSize);
+
+                for (int i = 0; i < numChunks; i++) {
+                    byte[] chunk = Arrays.copyOfRange(regionInfo, i * chunkSize, Math.min((i + 1) * chunkSize, regionInfoLength));
+                    byte[] encryptedChunk = cipher.doFinal(chunk);
+                    encryptedRegionInfoStream.write(encryptedChunk);
+                }
+
+                Signature privateSignature = Signature.getInstance("SHA256withRSA");
+                privateSignature.initSign(Crypto.CUR_SIGNING_KEY);
+                privateSignature.update(regionInfo);
 
-                String encodedRsp = Utils.base64Encode(cipher.doFinal(Utils.base64Decode(regionInfo)));
                 var rsp = new QueryCurRegionRspJson();
 
-                rsp.content = encodedRsp;
-                rsp.sign = "ZnVja195b3VfbWh5";
+                rsp.content = Utils.base64Encode(encryptedRegionInfoStream.toByteArray());
+                rsp.sign = Utils.base64Encode(privateSignature.sign());
 
                 response.send(rsp);
             }
-            catch(Exception e) {
-                e.printStackTrace();
+            catch (Exception e) {
+                Grasscutter.getLogger().error("An error occurred while handling query_cur_region.", e);
             }
         }
         else {
@@ -206,4 +216,4 @@ public String getBase64() {
     public static QueryCurrRegionHttpRsp getCurrentRegion() {
         return SERVER.runMode == ServerRunMode.HYBRID ? regions.get("os_usa").getRegionQuery() : null;
     }
-}
+}

src/main/java/emu/grasscutter/server/packet/recv/HandlerGetPlayerTokenReq.java

@@ -14,6 +14,13 @@
 import emu.grasscutter.server.game.GameSession;
 import emu.grasscutter.server.game.GameSession.SessionState;
 import emu.grasscutter.server.packet.send.PacketGetPlayerTokenRsp;
+import emu.grasscutter.utils.Crypto;
+import emu.grasscutter.utils.Utils;
+
+import javax.crypto.Cipher;
+
+import java.nio.ByteBuffer;
+import java.security.Signature;
 
 @Opcodes(PacketOpcodes.GetPlayerTokenReq)
 public class HandlerGetPlayerTokenReq extends PacketHandler {
@@ -90,8 +97,32 @@ public void handle(GameSession session, byte[] header, byte[] payload) throws Ex
 		session.setUseSecretKey(true);
 		session.setState(SessionState.WAITING_FOR_LOGIN);
 
-		// Send packet
-		session.send(new PacketGetPlayerTokenRsp(session));
-	}
-
+        // Only >= 2.7.50 has this
+        if (req.getKeyId() > 0) {
+            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
+            cipher.init(Cipher.DECRYPT_MODE, Crypto.CUR_SIGNING_KEY);
+
+            var client_seed_encrypted = Utils.base64Decode(req.getClientSeed());
+            var client_seed = ByteBuffer.wrap(cipher.doFinal(client_seed_encrypted))
+                .getLong();
+
+            byte[] seed_bytes = ByteBuffer.wrap(new byte[8])
+                .putLong(Crypto.ENCRYPT_SEED ^ client_seed)
+                .array();
+
+            //Kind of a hack, but whatever
+            cipher.init(Cipher.ENCRYPT_MODE, req.getKeyId() == 3 ? Crypto.CUR_OSCB_ENCRYPT_KEY : Crypto.CUR_OSCN_ENCRYPT_KEY);
+            var seed_encrypted = cipher.doFinal(seed_bytes);
+
+            Signature privateSignature = Signature.getInstance("SHA256withRSA");
+            privateSignature.initSign(Crypto.CUR_SIGNING_KEY);
+            privateSignature.update(seed_bytes);
+
+            session.send(new PacketGetPlayerTokenRsp(session, Utils.base64Encode(seed_encrypted), Utils.base64Encode(privateSignature.sign())));
+        }
+        else {
+            // Send packet
+            session.send(new PacketGetPlayerTokenRsp(session));
+        }
+    }
 }