*
 * This class provides helper methods for working with ASN.1
 * encoded data structures used in Kerberos PAC processing.
 */
public final class ASN1Util {

    private ASN1Util() {
    }

    /**
     * Casts an object to the specified type with type checking
     * @param <T> the target type
     * @param type the target class type
     * @param object the object to cast

                DERGeneralString derRealm = ASN1Util.as(DERGeneralString.class, tagged);
                this.userRealm = derRealm.getString();
                break;
            case 3: // Principal
                ASN1Sequence principalSequence = ASN1Util.as(ASN1Sequence.class, tagged);
                ASN1Sequence nameSequence = ASN1Util.as(ASN1Sequence.class, ASN1Util.as(ASN1TaggedObject.class, principalSequence, 1));

        while (authElements.hasMoreElements()) {
            ASN1Sequence authElement = ASN1Util.as(ASN1Sequence.class, authElements);
            ASN1Integer authType = ASN1Util.as(ASN1Integer.class, ASN1Util.as(ASN1TaggedObject.class, authElement, 0));
            DEROctetString authData = ASN1Util.as(DEROctetString.class, ASN1Util.as(ASN1TaggedObject.class, authElement, 1));

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.ASN1TaggedObject;
import org.bouncycastle.asn1.BERTags;

import jcifs.pac.ASN1Util;
import jcifs.pac.PACDecodingException;

/**
 * Represents a Kerberos authentication token.
 */
public class KerberosToken {

    private KerberosApRequest apRequest;

    /**

import org.junit.jupiter.api.Test;

/**
 * Tests for the {@link ASN1Util} class.
 */
class ASN1UtilTest {

    // --- as(Class, Object) ---

    @Test
    void testAs_Object_Success() throws PACDecodingException {
        // Test successful casting
        String expected = "test string";
        Object obj = expected;
        String result = ASN1Util.as(String.class, obj);
        assertSame(expected, result);
    }

            case 3:// Encrypted part
                ASN1Sequence encSequence = ASN1Util.as(ASN1Sequence.class, tagged);
                ASN1Integer encType = ASN1Util.as(ASN1Integer.class, ASN1Util.as(ASN1TaggedObject.class, encSequence, 0));
                DEROctetString encOctets = ASN1Util.as(DEROctetString.class, ASN1Util.as(ASN1TaggedObject.class, encSequence, 2));
                byte[] crypt = encOctets.getOctets();

        Enumeration<?> fields = seq.getObjects();
        while (fields.hasMoreElements()) {
            ASN1TaggedObject tagged = ASN1Util.as(ASN1TaggedObject.class, fields.nextElement());
            switch (tagged.getTagNo()) {
            case 0:
                ASN1Integer pvno = ASN1Util.as(ASN1Integer.class, tagged);
                if (!pvno.getValue().equals(new BigInteger(KerberosConstants.KERBEROS_VERSION))) {

        byte[] emptyToken = new byte[0];
        Map<Integer, KerberosKey> keys = new HashMap<>();

        // 2. WHEN & 3. THEN
        // When ASN1InputStream.readObject() returns null due to empty input,
        // ASN1Util.as() throws NullPointerException (not wrapped)
        Exception exception = assertThrows(Exception.class, () -> {
            new KerberosRelevantAuthData(emptyToken, keys);

        ASN1Sequence seq = new DERSequence(v);

        // Act + Assert
        // Note: The actual error will be from ASN1Util.as() trying to cast to ASN1TaggedObject
        assertThrows(PACDecodingException.class, () -> new KerberosApRequest(seq, null));
    }

    @Test
    @DisplayName("seq ctor: tag 3 APPLICATION triggers ticket parsing")