Add client -> proxy connections, encryption and mojang authentication.

src/main/java/net/md_5/bungee/EncryptionUtil.java

@@ -0,0 +1,89 @@
+package net.md_5.bungee;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.math.BigInteger;
+import java.net.URL;
+import java.net.URLEncoder;
+import java.security.Key;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.Security;
+import java.util.Arrays;
+import java.util.Random;
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.SecretKeySpec;
+import net.md_5.bungee.packet.PacketFCEncryptionResponse;
+import net.md_5.bungee.packet.PacketFDEncryptionRequest;
+import org.bouncycastle.crypto.BufferedBlockCipher;
+import org.bouncycastle.crypto.engines.AESFastEngine;
+import org.bouncycastle.crypto.modes.CFBBlockCipher;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.crypto.params.ParametersWithIV;
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
+
+public class EncryptionUtil {
+
+    private static final Random random = new Random();
+    private static KeyPair keys;
+
+    static {
+        Security.addProvider(new BouncyCastleProvider());
+    }
+
+    public static PacketFDEncryptionRequest encryptRequest() throws NoSuchAlgorithmException {
+        if (keys == null) {
+            keys = KeyPairGenerator.getInstance("RSA").generateKeyPair();
+        }
+
+        String hash = Long.toString(random.nextLong(), 16);
+        byte[] pubKey = keys.getPublic().getEncoded();
+        byte[] verify = new byte[4];
+        random.nextBytes(verify);
+        return new PacketFDEncryptionRequest(hash, pubKey, verify);
+    }
+
+    public static SecretKey getSecret(PacketFCEncryptionResponse resp, PacketFDEncryptionRequest request) throws Exception {
+        Cipher cipher = Cipher.getInstance("RSA");
+        cipher.init(Cipher.DECRYPT_MODE, keys.getPrivate());
+        byte[] decrypted = cipher.doFinal(resp.verifyToken);
+
+        if (!Arrays.equals(request.verifyToken, decrypted)) {
+            throw new IllegalStateException("Key pairs do not match!");
+        }
+
+        cipher.init(Cipher.DECRYPT_MODE, keys.getPrivate());
+        byte[] shared = resp.sharedSecret;
+        byte[] secret = cipher.doFinal(shared);
+
+        return new SecretKeySpec(secret, "AES");
+    }
+
+    public static boolean isAuthenticated(String username, String connectionHash, SecretKey shared) throws NoSuchAlgorithmException, IOException {
+        String encName = URLEncoder.encode(username, "UTF-8");
+
+        MessageDigest sha = MessageDigest.getInstance("SHA-1");
+        for (byte[] bit : new byte[][]{connectionHash.getBytes("ISO_8859_1"), shared.getEncoded(), keys.getPublic().getEncoded()}) {
+            sha.update(bit);
+        }
+
+        String encodedHash = URLEncoder.encode(new BigInteger(sha.digest()).toString(16), "UTF-8");
+        String authURL = "http://session.minecraft.net/game/checkserver.jsp?user=" + encName + "&serverId=" + encodedHash;
+        String reply;
+        try (BufferedReader in = new BufferedReader(new InputStreamReader(new URL(authURL).openStream()))) {
+            reply = in.readLine();
+        }
+
+        return "YES".equals(reply);
+    }
+
+    public static BufferedBlockCipher getCipher(boolean forEncryption, Key shared) {
+        BufferedBlockCipher cip = new BufferedBlockCipher(new CFBBlockCipher(new AESFastEngine(), 8));
+        cip.init(forEncryption, new ParametersWithIV(new KeyParameter(shared.getEncoded()), shared.getEncoded(), 0, 16));
+        return cip;
+    }
+}

src/main/java/net/md_5/bungee/InitialHandler.java

@@ -1,17 +1,23 @@
 package net.md_5.bungee;
 
+import java.io.BufferedOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.Socket;
+import javax.crypto.SecretKey;
 import net.md_5.bungee.packet.Packet2Handshake;
+import net.md_5.bungee.packet.PacketFCEncryptionResponse;
+import net.md_5.bungee.packet.PacketFDEncryptionRequest;
 import net.md_5.bungee.packet.PacketFFKick;
 import net.md_5.bungee.packet.PacketInputStream;
+import org.bouncycastle.crypto.io.CipherInputStream;
+import org.bouncycastle.crypto.io.CipherOutputStream;
 
 public class InitialHandler implements Runnable {
 
     private final Socket socket;
-    private final PacketInputStream in;
-    private final OutputStream out;
+    private PacketInputStream in;
+    private OutputStream out;
 
     public InitialHandler(Socket socket) throws IOException {
         this.socket = socket;
@@ -27,6 +33,24 @@ public class InitialHandler implements Runnable {
             switch (id) {
                 case 0x02:
                     Packet2Handshake handshake = new Packet2Handshake(packet);
+                    PacketFDEncryptionRequest request = EncryptionUtil.encryptRequest();
+                    out.write(request.getPacket());
+                    PacketFCEncryptionResponse response = new PacketFCEncryptionResponse(in.readPacket());
+
+                    SecretKey shared = EncryptionUtil.getSecret(response, request);
+                    if (!EncryptionUtil.isAuthenticated(handshake.username, request.serverId, shared)) {
+                        throw new KickException("Not authenticated with minecraft.net");
+                    }
+
+                    out.write(new PacketFCEncryptionResponse().getPacket());
+                    in = new PacketInputStream(new CipherInputStream(socket.getInputStream(), EncryptionUtil.getCipher(false, shared)));
+                    out = new BufferedOutputStream(new CipherOutputStream(socket.getOutputStream(), EncryptionUtil.getCipher(true, shared)), 5120);
+
+                    int ciphId = Util.getId(in.readPacket());
+                    if (ciphId != 0xCD) {
+                        throw new KickException("Unable to receive encrypted client status");
+                    }
+
                     break;
                 case 0xFE:
                     throw new KickException(BungeeCord.instance.config.motd + ChatColor.COLOR_CHAR + BungeeCord.instance.getOnlinePlayers() + ChatColor.COLOR_CHAR + BungeeCord.instance.config.maxPlayers);

src/main/java/net/md_5/bungee/packet/DefinedPacket.java

@@ -42,7 +42,6 @@ public abstract class DefinedPacket implements DataInput, DataOutput {
         out = ByteStreams.newDataOutput();
         this.id = id;
         writeByte(id);
-        packet = null;
     }
 
     public byte[] getPacket() {