Java IllegalStateException: Protocol error from sending a Encryption Response packet to server

Issue

I am trying to make a java program to be able to login to a minecraft server. From this and help of some other related posts like this I have been able to deal with the Handshake, Login Start and Encryption Request packets. The problem is in the Encryption Response packet, I managed to generate and encrypt the shared secret and VerifyToken with the server's public key which have to be sent in this packet and send it; but instead of the server responding with Login Success, it gives a Disconnect packet with the error:

{"translate":"disconnect.genericReason","with":["Internal Exception: java.lang.IllegalStateException: Protocol error"]}

here is my code related to Encryption Response:

System.out.println("Proceeding with Encryption Response...");
        byte[] encryptionResponse = encryptionResponse(encryptedSecret.length, encryptedSecret,
                encryptedVerifyToken.length, encryptedVerifyToken);
        // C->S Encryption Response
        writeVarInt(output, encryptionResponse.length);
        output.write(encryptionResponse);


        System.out.println("Response length: " + encryptionResponse.length + " Response: " + Arrays.toString(encryptionResponse));
        System.out.println("Done!");

public static byte [] encryptionResponse(int secretLen, byte[] secret, int tokenLen, byte[] token) throws IOException {
        ByteArrayOutputStream buffers = new ByteArrayOutputStream();

        DataOutputStream response = new DataOutputStream(buffers);

        System.out.println(secretLen + " " + tokenLen);
        System.out.println("Secret: " + Arrays.toString(secret));
        System.out.println("Token: " + Arrays.toString(token));


        response.writeByte(0x01); //packet id for Encryption Response

        writeVarInt(response, secretLen); //secret length
        for (byte b : secret){ // send secret
            response.writeByte(b);
        }

        response.writeBoolean(true); // we have the verifyToken
        writeVarInt(response, tokenLen); // send the length of token
        for (byte b : token){ // send the token
            response.writeByte(b);
        }

        return buffers.toByteArray();
    }

This is the things that get printed to the console(or log or whatever):

Proceeding with Encryption Response...

128 128

Secret: [2, 105, 39, 117, -19, 27, -103, -102, -126, 58, 31, -75, 48, 26, -4, 116, 60, 52, 119, -37, -102, 127, 120, -21, 66, 72, 12, 127, -122, -27, -67, 53, -98, -23, -79, 28, 41, 10, 105, 45, 80, 14, -117, -4, 121, -82, 79, -57, 109, 31, 55, -36, -122, -78, -17, 33, -101, 67, -103, -103, -7, -99, -113, -86, -90, -1, 11, -75, -57, -90, -17, 97, 56, 39, 49, -107, -40, 119, 28, 52, -23, 75, -115, -9, 45, -117, -24, -49, -33, 19, -91, -45, 62, 119, 32, 52, -117, -121, -82, -44, -74, -17, -58, 54, 123, -114, 65, -75, 114, 62, -8, -6, 11, -35, -113, 64, 18, 33, -108, -62, -72, -119, -55, 96, 110, -75, 81, -84]

Token: [47, 114, -1, 115, -95, -35, 90, -27, -117, 92, 13, -78, -43, -96, 71, 112, 56, 34, 27, 127, 1, -22, -32, 123, 32, 88, -38, 28, -92, 24, -106, 57, 97, -25, -2, 87, 39, -57, -67, 48, -126, 113, -44, -31, 79, -72, 17, -97, 62, 90, -123, -117, 119, 37, 88, -116, 63, 84, -100, -92, 71, -88, 102, 55, 24, 100, -69, -115, 30, 27, -41, 123, -115, 67, 18, -110, -23, -71, 84, 38, -114, -32, 72, 10, -110, 22, -89, 24, -82, 110, 51, 46, 38, -112, 29, -65, -49, 83, 115, -70, 110, 32, -96, 35, -31, 7, -59, -71, -98, 22, 28, -108, -126, -83, 0, -18, 107, 125, -120, -50, -79, -44, -94, 111, -117, -53, 32, 51]

Response length: 262. Response: [1, -128, 1, 2, 105, 39, 117, -19, 27, -103, -102, -126, 58, 31, -75, 48, 26, -4, 116, 60, 52, 119, -37, -102, 127, 120, -21, 66, 72, 12, 127, -122, -27, -67, 53, -98, -23, -79, 28, 41, 10, 105, 45, 80, 14, -117, -4, 121, -82, 79, -57, 109, 31, 55, -36, -122, -78, -17, 33, -101, 67, -103, -103, -7, -99, -113, -86, -90, -1, 11, -75, -57, -90, -17, 97, 56, 39, 49, -107, -40, 119, 28, 52, -23, 75, -115, -9, 45, -117, -24, -49, -33, 19, -91, -45, 62, 119, 32, 52, -117, -121, -82, -44, -74, -17, -58, 54, 123, -114, 65, -75, 114, 62, -8, -6, 11, -35, -113, 64, 18, 33, -108, -62, -72, -119, -55, 96, 110, -75, 81, -84, 1, -128, 1, 47, 114, -1, 115, -95, -35, 90, -27, -117, 92, 13, -78, -43, -96, 71, 112, 56, 34, 27, 127, 1, -22, -32, 123, 32, 88, -38, 28, -92, 24, -106, 57, 97, -25, -2, 87, 39, -57, -67, 48, -126, 113, -44, -31, 79, -72, 17, -97, 62, 90, -123, -117, 119, 37, 88, -116, 63, 84, -100, -92, 71, -88, 102, 55, 24, 100, -69, -115, 30, 27, -41, 123, -115, 67, 18, -110, -23, -71, 84, 38, -114, -32, 72, 10, -110, 22, -89, 24, -82, 110, 51, 46, 38, -112, 29, -65, -49, 83, 115, -70, 110, 32, -96, 35, -31, 7, -59, -71, -98, 22, 28, -108, -126, -83, 0, -18, 107, 125, -120, -50, -79, -44, -94, 111, -117, -53, 32, 51]

Done!

more information on this can be found here

here is all of the code of my program

Solution

The problem is the lines where you encrypt the shared secret and the verify token:

byte[] encryptedSecret = encrypt(publicKeyBytes, Arrays.toString(secret.getEncoded()).getBytes(StandardCharsets.UTF_8), ALGORITHM);
...
byte[] encryptedVerifyToken = encrypt(publicKeyBytes, Arrays.toString(verifyTokenBytes).getBytes(StandardCharsets.UTF_8), ALGORITHM);

These should be:

byte[] encryptedSecret = encrypt(publicKeyBytes, secret.getEncoded(), ALGORITHM);
...
byte[] encryptedVerifyToken = encrypt(publicKeyBytes, verifyTokenBytes, ALGORITHM);

You want to encrypt the actual bytes of the shared secret / verify token, not the bytes of the string representation of the byte array.

Answered By - Donut