Authentication

/**
 * Client-side SASL authentication bootstrap for secure connections
 */
public class SaslClientBootstrap implements TransportClientBootstrap {
    /**
     * Create a SASL client bootstrap
     * @param conf Transport configuration containing SASL settings
     * @param appId Application identifier for authentication
     * @param secretKeyHolder Provider for secret keys and user information
     */
    public SaslClientBootstrap(TransportConf conf, String appId, SecretKeyHolder secretKeyHolder);
    
    /**
     * Bootstrap the client channel with SASL authentication
     * @param client Transport client instance
     * @param channel Netty channel to authenticate
     * @throws RuntimeException if authentication fails
     */
    public void doBootstrap(TransportClient client, Channel channel) throws RuntimeException;
}

/**
 * Server-side SASL authentication bootstrap for accepting secure connections
 */
public class SaslServerBootstrap implements TransportServerBootstrap {
    /**
     * Create a SASL server bootstrap
     * @param conf Transport configuration containing SASL settings
     * @param secretKeyHolder Provider for secret keys and user information
     */
    public SaslServerBootstrap(TransportConf conf, SecretKeyHolder secretKeyHolder);
    
    /**
     * Bootstrap the server channel with SASL authentication
     * @param channel Netty channel to authenticate
     * @param rpcHandler Original RPC handler to wrap with authentication
     * @return RPC handler with SASL authentication support
     */
    public RpcHandler doBootstrap(Channel channel, RpcHandler rpcHandler);
}

// Client-side SASL setup
SecretKeyHolder keyHolder = new MySecretKeyHolder();
List<TransportClientBootstrap> clientBootstraps = Arrays.asList(
    new SaslClientBootstrap(conf, "my-app-id", keyHolder)
);
TransportClientFactory factory = context.createClientFactory(clientBootstraps);
TransportClient client = factory.createClient("spark-server", 7337);

// Server-side SASL setup
List<TransportServerBootstrap> serverBootstraps = Arrays.asList(
    new SaslServerBootstrap(conf, keyHolder)
);
TransportServer server = context.createServer(7337, serverBootstraps);

/**
 * Interface for holding and retrieving secret keys for authentication
 * Implementations should provide secure storage and retrieval of credentials
 */
public interface SecretKeyHolder {
    /**
     * Get the SASL user identifier for the given application
     * @param appId Application identifier
     * @return SASL username for authentication
     */
    String getSaslUser(String appId);
    
    /**
     * Get the secret key for the given application
     * @param appId Application identifier  
     * @return Secret key for authentication
     */
    String getSecretKey(String appId);
}

// Implementing SecretKeyHolder
public class FileBasedSecretKeyHolder implements SecretKeyHolder {
    private final Properties secrets;
    
    public FileBasedSecretKeyHolder(String secretsFile) throws IOException {
        secrets = new Properties();
        try (InputStream is = new FileInputStream(secretsFile)) {
            secrets.load(is);
        }
    }
    
    @Override
    public String getSaslUser(String appId) {
        return secrets.getProperty(appId + ".user", appId);
    }
    
    @Override
    public String getSecretKey(String appId) {
        return secrets.getProperty(appId + ".secret");
    }
}

// In-memory implementation
public class MapBasedSecretKeyHolder implements SecretKeyHolder {
    private final Map<String, String> users = new HashMap<>();
    private final Map<String, String> secrets = new HashMap<>();
    
    public void addCredential(String appId, String user, String secret) {
        users.put(appId, user);
        secrets.put(appId, secret);
    }
    
    @Override
    public String getSaslUser(String appId) {
        return users.get(appId);
    }
    
    @Override
    public String getSecretKey(String appId) {
        return secrets.get(appId);
    }
}

/**
 * SASL client implementation for Spark providing authentication handshake
 */
public class SparkSaslClient {
    /**
     * Create a SASL client for authentication
     * @param secretKeyId Application identifier for key lookup
     * @param secretKeyHolder Provider for authentication credentials
     * @param encrypt Whether to enable SASL encryption after authentication
     */
    public SparkSaslClient(String secretKeyId, SecretKeyHolder secretKeyHolder, boolean encrypt);
    
    /**
     * Check if client is complete (authentication finished)
     * @return true if authentication is complete
     */
    public boolean isComplete();
    
    /**
     * Process challenge from server and generate response
     * @param challenge Challenge bytes from server
     * @return Response bytes to send to server
     * @throws Exception if processing fails
     */
    public byte[] response(byte[] challenge) throws Exception;
    
    /**
     * Dispose of client resources and cleanup
     */
    public void dispose();
}

/**
 * SASL server implementation for Spark providing authentication verification
 */
public class SparkSaslServer {
    /**
     * Create a SASL server for authentication
     * @param secretKeyId Application identifier for key lookup
     * @param secretKeyHolder Provider for authentication credentials
     * @param encrypt Whether to enable SASL encryption after authentication
     */
    public SparkSaslServer(String secretKeyId, SecretKeyHolder secretKeyHolder, boolean encrypt);
    
    /**
     * Check if server is complete (authentication finished)
     * @return true if authentication is complete
     */
    public boolean isComplete();
    
    /**
     * Process response from client and generate challenge
     * @param response Response bytes from client
     * @return Challenge bytes to send to client, or null if complete
     * @throws Exception if processing fails
     */
    public byte[] response(byte[] response) throws Exception;
    
    /**
     * Get the authenticated user identifier
     * @return User ID that was authenticated
     */
    public String getAuthenticatedUser();
    
    /**
     * Dispose of server resources and cleanup
     */
    public void dispose();
}

/**
 * RPC handler with SASL authentication support
 * Wraps application RPC handlers to provide authentication before processing
 */
public class SaslRpcHandler extends RpcHandler {
    /**
     * Create a SASL RPC handler
     * @param conf Transport configuration
     * @param wrapped Application RPC handler to protect with authentication
     * @param secretKeyHolder Provider for authentication credentials
     */
    public SaslRpcHandler(TransportConf conf, RpcHandler wrapped, SecretKeyHolder secretKeyHolder);
    
    /**
     * Receive and process RPC message with authentication check
     * @param client Transport client connection
     * @param message RPC message content
     * @param callback Callback for sending response
     */
    public void receive(TransportClient client, ByteBuffer message, RpcResponseCallback callback);
    
    /**
     * Get stream manager with authentication support
     * @return StreamManager that checks authentication before serving streams
     */
    public StreamManager getStreamManager();
    
    /**
     * Handle channel activation with authentication setup
     * @param client Transport client that connected
     */
    public void channelActive(TransportClient client);
    
    /**
     * Handle channel deactivation with cleanup
     * @param client Transport client that disconnected
     */
    public void channelInactive(TransportClient client);
}

/**
 * Client bootstrap for custom authentication protocol
 */
public class AuthClientBootstrap implements TransportClientBootstrap {
    /**
     * Create custom auth client bootstrap
     * @param conf Transport configuration
     * @param appId Application identifier
     * @param secretKeyHolder Provider for authentication credentials
     */
    public AuthClientBootstrap(TransportConf conf, String appId, SecretKeyHolder secretKeyHolder);
    
    /**
     * Bootstrap client channel with custom authentication
     * @param client Transport client instance
     * @param channel Netty channel to authenticate
     * @throws RuntimeException if authentication fails
     */
    public void doBootstrap(TransportClient client, Channel channel) throws RuntimeException;
}

/**
 * Server bootstrap for custom authentication protocol
 */
public class AuthServerBootstrap implements TransportServerBootstrap {
    /**
     * Create custom auth server bootstrap
     * @param conf Transport configuration
     * @param secretKeyHolder Provider for authentication credentials
     */
    public AuthServerBootstrap(TransportConf conf, SecretKeyHolder secretKeyHolder);
    
    /**
     * Bootstrap server channel with custom authentication
     * @param channel Netty channel to authenticate
     * @param rpcHandler Original RPC handler to protect
     * @return RPC handler with authentication support
     */
    public RpcHandler doBootstrap(Channel channel, RpcHandler rpcHandler);
}

/**
 * Client challenge message for authentication negotiation
 */
public class ClientChallenge implements Encodable {
    /**
     * Create a client challenge message
     * @param appId Application identifier
     * @param kdf Key derivation function name
     * @param iterations Number of iterations for key derivation
     * @param cipher Cipher algorithm name
     * @param keyLength Key length in bits
     * @param nonce Random nonce for challenge
     * @param challenge Challenge data
     */
    public ClientChallenge(String appId, String kdf, int iterations, String cipher, 
                          int keyLength, byte[] nonce, byte[] challenge);
    
    /**
     * Get application identifier
     * @return Application ID string
     */
    public String appId();
    
    /**
     * Get key derivation function name
     * @return KDF algorithm name
     */
    public String kdf();
    
    /**
     * Get key derivation iterations
     * @return Number of iterations
     */
    public int iterations();
    
    /**
     * Get cipher algorithm name
     * @return Cipher algorithm
     */
    public String cipher();
    
    /**
     * Get key length in bits
     * @return Key length
     */
    public int keyLength();
    
    /**
     * Get challenge nonce
     * @return Nonce bytes
     */
    public byte[] nonce();
    
    /**
     * Get challenge data
     * @return Challenge bytes
     */
    public byte[] challenge();
    
    /**
     * Calculate encoded length
     * @return Length in bytes
     */
    public int encodedLength();
    
    /**
     * Encode to ByteBuf
     * @param buf Output buffer
     */
    public void encode(ByteBuf buf);
    
    /**
     * Decode from ByteBuffer
     * @param buffer Input buffer
     * @return Decoded ClientChallenge
     */
    public static ClientChallenge decodeMessage(ByteBuffer buffer);
}

/**
 * Server response message for authentication negotiation
 */
public class ServerResponse implements Encodable {
    /**
     * Create a server response message
     * @param response Response data to client challenge
     * @param inputIv Input initialization vector for encryption
     * @param outputIv Output initialization vector for encryption
     */
    public ServerResponse(byte[] response, byte[] inputIv, byte[] outputIv);
    
    /**
     * Get server response data
     * @return Response bytes
     */
    public byte[] response();
    
    /**
     * Get input initialization vector
     * @return Input IV bytes
     */
    public byte[] inputIv();
    
    /**
     * Get output initialization vector
     * @return Output IV bytes
     */
    public byte[] outputIv();
    
    /**
     * Calculate encoded length
     * @return Length in bytes
     */
    public int encodedLength();
    
    /**
     * Encode to ByteBuf
     * @param buf Output buffer
     */
    public void encode(ByteBuf buf);
    
    /**
     * Decode from ByteBuffer
     * @param buffer Input buffer
     * @return Decoded ServerResponse
     */
    public static ServerResponse decodeMessage(ByteBuffer buffer);
}

/**
 * Manages encryption/decryption for transport channels after authentication
 */
public class TransportCipher {
    /**
     * Create a transport cipher with encryption parameters
     * @param cryptoConf Crypto configuration properties
     * @param cipher Cipher transformation string
     * @param inKey Key for decrypting incoming data
     * @param outKey Key for encrypting outgoing data
     * @param inIv Initialization vector for incoming data
     * @param outIv Initialization vector for outgoing data
     * @throws IOException if cipher setup fails
     */
    public TransportCipher(Properties cryptoConf, String cipher, byte[] inKey, byte[] outKey, 
                          byte[] inIv, byte[] outIv) throws IOException;
    
    /**
     * Get the cipher transformation string
     * @return Cipher transformation (e.g., "AES/CTR/NoPadding")
     */
    public String getCipherTransformation();
    
    /**
     * Get input initialization vector
     * @return Input IV bytes
     */
    public byte[] getInputIv();
    
    /**
     * Get output initialization vector
     * @return Output IV bytes
     */
    public byte[] getOutputIv();
    
    /**
     * Add encryption handlers to the Netty channel pipeline
     * @param ch Channel to add encryption to
     * @throws IOException if handlers cannot be added
     */
    public void addToChannel(Channel ch) throws IOException;
}

// Setting up encrypted transport after custom auth
Properties cryptoConf = new Properties();
cryptoConf.setProperty("spark.network.crypto.keyLength", "128");
cryptoConf.setProperty("spark.network.crypto.keyFactoryAlgorithm", "PBKDF2WithHmacSHA1");

TransportCipher cipher = new TransportCipher(
    cryptoConf,
    "AES/CTR/NoPadding", 
    inKey, outKey, 
    inIv, outIv
);

// Add encryption to channel after authentication
cipher.addToChannel(channel);

// Server setup with SASL
SecretKeyHolder secretKeyHolder = new MySecretKeyHolder();
List<TransportServerBootstrap> serverBootstraps = Arrays.asList(
    new SaslServerBootstrap(conf, secretKeyHolder)
);

TransportContext context = new TransportContext(conf, new MyRpcHandler());
TransportServer server = context.createServer(7337, serverBootstraps);

// Client setup with SASL
List<TransportClientBootstrap> clientBootstraps = Arrays.asList(
    new SaslClientBootstrap(conf, "my-app", secretKeyHolder)
);

TransportClientFactory factory = context.createClientFactory(clientBootstraps);
TransportClient client = factory.createClient("localhost", 7337);

// Client is now authenticated and can send RPCs
client.sendRpc(message, callback);

// Custom auth server
List<TransportServerBootstrap> bootstraps = Arrays.asList(
    new AuthServerBootstrap(conf, secretKeyHolder)
);
TransportServer server = context.createServer(8080, bootstraps);

// Custom auth client
List<TransportClientBootstrap> clientBootstraps = Arrays.asList(
    new AuthClientBootstrap(conf, "custom-app", secretKeyHolder)
);
TransportClientFactory factory = context.createClientFactory(clientBootstraps);
TransportClient client = factory.createClient("localhost", 8080);

// Configure authentication and encryption settings
Map<String, String> configMap = new HashMap<>();
configMap.put("spark.authenticate", "true");
configMap.put("spark.network.sasl.serverAlwaysEncrypt", "true");
configMap.put("spark.network.crypto.enabled", "true");
configMap.put("spark.network.crypto.keyLength", "256");

TransportConf conf = new TransportConf("secure-app", new MapConfigProvider(configMap));