Refactor cipher logic.

native/src/main/java/com/velocitypowered/natives/encryption/JavaVelocityCipher.java

@@ -10,10 +10,22 @@ import javax.crypto.spec.IvParameterSpec;
 import java.security.GeneralSecurityException;
 
 public class JavaVelocityCipher implements VelocityCipher {
+    public static final VelocityCipherFactory FACTORY = new VelocityCipherFactory() {
+        @Override
+        public VelocityCipher forEncryption(SecretKey key) throws GeneralSecurityException {
+            return new JavaVelocityCipher(true, key);
+        }
+
+        @Override
+        public VelocityCipher forDecryption(SecretKey key) throws GeneralSecurityException {
+            return new JavaVelocityCipher(false, key);
+        }
+    };
+
     private final Cipher cipher;
     private boolean disposed = false;
 
-    public JavaVelocityCipher(boolean encrypt, SecretKey key) throws GeneralSecurityException {
+    private JavaVelocityCipher(boolean encrypt, SecretKey key) throws GeneralSecurityException {
         this.cipher = Cipher.getInstance("AES/CFB8/NoPadding");
         this.cipher.init(encrypt ? Cipher.ENCRYPT_MODE : Cipher.DECRYPT_MODE, key, new IvParameterSpec(key.getEncoded()));
     }

native/src/main/java/com/velocitypowered/natives/encryption/VelocityCipherFactory.java

@@ -0,0 +1,10 @@
+package com.velocitypowered.natives.encryption;
+
+import javax.crypto.SecretKey;
+import java.security.GeneralSecurityException;
+
+public interface VelocityCipherFactory {
+    VelocityCipher forEncryption(SecretKey key) throws GeneralSecurityException;
+
+    VelocityCipher forDecryption(SecretKey key) throws GeneralSecurityException;
+}

native/src/main/java/com/velocitypowered/natives/util/Natives.java

@@ -5,6 +5,8 @@ import com.velocitypowered.natives.compression.JavaVelocityCompressor;
 import com.velocitypowered.natives.compression.NativeVelocityCompressor;
 import com.velocitypowered.natives.compression.VelocityCompressor;
 import com.velocitypowered.natives.compression.VelocityCompressorFactory;
+import com.velocitypowered.natives.encryption.JavaVelocityCipher;
+import com.velocitypowered.natives.encryption.VelocityCipherFactory;
 
 import java.io.IOException;
 import java.nio.file.Files;
@@ -46,4 +48,10 @@ public class Natives {
                     new NativeCodeLoader.Variant<>(NativeCodeLoader.ALWAYS, () -> {}, "Java compression", JavaVelocityCompressor.FACTORY)
             )
     );
+
+    public static final NativeCodeLoader<VelocityCipherFactory> cipher = new NativeCodeLoader<>(
+            ImmutableList.of(
+                    new NativeCodeLoader.Variant<>(NativeCodeLoader.ALWAYS, () -> {}, "Java cipher", JavaVelocityCipher.FACTORY)
+            )
+    );
 }

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -54,6 +54,7 @@ public class VelocityServer {
 
     public void start() {
         logger.info("Using {}", Natives.compressor.getLoadedVariant());
+        logger.info("Using {}", Natives.cipher.getLoadedVariant());
 
         // Create a key pair
         logger.info("Booting up Velocity...");

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftConnection.java

@@ -2,6 +2,7 @@ package com.velocitypowered.proxy.connection;
 
 import com.google.common.base.Preconditions;
 import com.velocitypowered.natives.compression.VelocityCompressor;
+import com.velocitypowered.natives.encryption.VelocityCipherFactory;
 import com.velocitypowered.natives.util.Natives;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.protocol.PacketWrapper;
@@ -205,8 +206,9 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
     public void enableEncryption(byte[] secret) throws GeneralSecurityException {
         SecretKey key = new SecretKeySpec(secret, "AES");
 
-        VelocityCipher decryptionCipher = new JavaVelocityCipher(false, key);
-        VelocityCipher encryptionCipher = new JavaVelocityCipher(true, key);
+        VelocityCipherFactory factory = Natives.cipher.get();
+        VelocityCipher decryptionCipher = factory.forDecryption(key);
+        VelocityCipher encryptionCipher = factory.forEncryption(key);
         channel.pipeline().addBefore(FRAME_DECODER, CIPHER_DECODER, new MinecraftCipherDecoder(decryptionCipher));
         channel.pipeline().addBefore(FRAME_ENCODER, CIPHER_ENCODER, new MinecraftCipherEncoder(encryptionCipher));
     }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -101,6 +101,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation {
     }
 
     public void handleConnectionException(ServerInfo info, Component disconnectReason) {
+        connectionInFlight = null;
         if (connectedServer == null || connectedServer.getServerInfo().equals(info)) {
             // The player isn't yet connected to a server or they are already connected to the server
             // they're disconnected from.