/*
 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.security.auth.kerberos;

import java.util.Arrays;
import java.util.Objects;
import javax.crypto.SecretKey;
import javax.security.auth.DestroyFailedException;

This class encapsulates an EncryptionKey used in Kerberos.

An EncryptionKey is defined in Section 4.2.9 of the Kerberos Protocol
Specification (RFC 4120) as:
    EncryptionKey   ::= SEQUENCE {
            keytype         [0] Int32 -- actually encryption type --,
            keyvalue        [1] OCTET STRING
    }
 The key material of an EncryptionKey is defined as the value of the keyValue above. 
Since:
9/**
 * This class encapsulates an EncryptionKey used in Kerberos.<p>
 *
 * An EncryptionKey is defined in Section 4.2.9 of the Kerberos Protocol
 * Specification (<a href=http://www.ietf.org/rfc/rfc4120.txt>RFC 4120</a>) as:
 * <pre>
 *     EncryptionKey   ::= SEQUENCE {
 *             keytype         [0] Int32 -- actually encryption type --,
 *             keyvalue        [1] OCTET STRING
 *     }
 * </pre>
 * The key material of an {@code EncryptionKey} is defined as the value
 * of the {@code keyValue} above.
 *
 * @since 9
 */
public final class EncryptionKey implements SecretKey {

    private static final long serialVersionUID = 9L;

   
KeyImpl is serialized by writing out the ASN.1 encoded bytes of the encryption key. 
@serial
/**
    * {@code KeyImpl} is serialized by writing out the ASN.1 encoded bytes
    * of the encryption key.
    *
    * @serial
    */
    final private KeyImpl key;

    private transient boolean destroyed = false;

    
Constructs an EncryptionKey from the given bytes and the key type. 

The contents of the byte array are copied; subsequent modification of
the byte array does not affect the newly created key.
Params:
keyBytes – the key material for the key
keyType – the key type for the key as defined by the
               Kerberos protocol specification.
Throws:
NullPointerException – if keyBytes is null/**
     * Constructs an {@code EncryptionKey} from the given bytes and
     * the key type.
     * <p>
     * The contents of the byte array are copied; subsequent modification of
     * the byte array does not affect the newly created key.
     *
     * @param keyBytes the key material for the key
     * @param keyType the key type for the key as defined by the
     *                Kerberos protocol specification.
     * @throws NullPointerException if keyBytes is null
     */
    public EncryptionKey(byte[] keyBytes, int keyType) {
        key = new KeyImpl(Objects.requireNonNull(keyBytes), keyType);
    }

    
Returns the key type for this key.
Throws:
IllegalStateException – if the key is destroyed
Returns:
the key type./**
     * Returns the key type for this key.
     *
     * @return the key type.
     * @throws IllegalStateException if the key is destroyed
     */
    public int getKeyType() {
        // KeyImpl already checked if destroyed
        return key.getKeyType();
    }

    /*
     * Methods from java.security.Key
     */

    
Returns the standard algorithm name for this key. The algorithm names
are the encryption type string defined on the IANA
Kerberos Encryption Type Numbers
page.

This method can return the following value not defined on the IANA page:

    
none: for etype equal to 0
    
unknown: for etype greater than 0 but unsupported by
        the implementation
    
private: for etype smaller than 0

Throws:
IllegalStateException – if the key is destroyed
Returns:
the name of the algorithm associated with this key./**
     * Returns the standard algorithm name for this key. The algorithm names
     * are the encryption type string defined on the IANA
     * <a href="https://www.iana.org/assignments/kerberos-parameters/kerberos-parameters.xhtml#kerberos-parameters-1">Kerberos Encryption Type Numbers</a>
     * page.
     * <p>
     * This method can return the following value not defined on the IANA page:
     * <ol>
     *     <li>none: for etype equal to 0</li>
     *     <li>unknown: for etype greater than 0 but unsupported by
     *         the implementation</li>
     *     <li>private: for etype smaller than 0</li>
     * </ol>
     *
     * @return the name of the algorithm associated with this key.
     * @throws IllegalStateException if the key is destroyed
     */
    @Override
    public String getAlgorithm() {
        // KeyImpl already checked if destroyed
        return key.getAlgorithm();
    }

    
Returns the name of the encoding format for this key.
Throws:
IllegalStateException – if the key is destroyed
Returns:
the String "RAW"/**
     * Returns the name of the encoding format for this key.
     *
     * @return the String "RAW"
     * @throws IllegalStateException if the key is destroyed
     */
    @Override
    public String getFormat() {
        // KeyImpl already checked if destroyed
        return key.getFormat();
    }

    
Returns the key material of this key.
Throws:
IllegalStateException – if the key is destroyed
Returns:
a newly allocated byte array that contains the key material/**
     * Returns the key material of this key.
     *
     * @return a newly allocated byte array that contains the key material
     * @throws IllegalStateException if the key is destroyed
     */
    @Override
    public byte[] getEncoded() {
        // KeyImpl already checked if destroyed
        return key.getEncoded();
    }

    
Destroys this key by clearing out the key material of this key.
Throws:
DestroyFailedException – if some error occurs while destorying
this key./**
     * Destroys this key by clearing out the key material of this key.
     *
     * @throws DestroyFailedException if some error occurs while destorying
     * this key.
     */
    @Override
    public void destroy() throws DestroyFailedException {
        if (!destroyed) {
            key.destroy();
            destroyed = true;
        }
    }


    @Override
    public boolean isDestroyed() {
        return destroyed;
    }

    
Returns an informative textual representation of this EncryptionKey. 
Returns:
an informative textual representation of this EncryptionKey./**
     * Returns an informative textual representation of this {@code EncryptionKey}.
     *
     * @return an informative textual representation of this {@code EncryptionKey}.
     */
    @Override
    public String toString() {
        if (destroyed) {
            return "Destroyed EncryptionKey";
        }
        return "key "  + key.toString();
    }

    
Returns a hash code for this EncryptionKey. 
Returns:
a hash code for this EncryptionKey./**
     * Returns a hash code for this {@code EncryptionKey}.
     *
     * @return a hash code for this {@code EncryptionKey}.
     */
    @Override
    public int hashCode() {
        int result = 17;
        if (isDestroyed()) {
            return result;
        }
        result = 37 * result + Arrays.hashCode(getEncoded());
        return 37 * result + getKeyType();
    }

    
Compares the specified object with this key for equality. Returns true if the given object is also an EncryptionKey and the two EncryptionKey instances are equivalent. More formally two EncryptionKey instances are equal if they have equal key types and key material. A destroyed EncryptionKey object is only equal to itself. 
Params:
other – the object to compare to
Returns:
true if the specified object is equal to this EncryptionKey, false otherwise./**
     * Compares the specified object with this key for equality.
     * Returns true if the given object is also an
     * {@code EncryptionKey} and the two
     * {@code EncryptionKey} instances are equivalent. More formally two
     * {@code EncryptionKey} instances are equal if they have equal key types
     * and key material.
     * A destroyed {@code EncryptionKey} object is only equal to itself.
     *
     * @param other the object to compare to
     * @return true if the specified object is equal to this
     * {@code EncryptionKey}, false otherwise.
     */
    @Override
    public boolean equals(Object other) {

        if (other == this)
            return true;

        if (! (other instanceof EncryptionKey)) {
            return false;
        }

        EncryptionKey otherKey = ((EncryptionKey) other);
        if (isDestroyed() || otherKey.isDestroyed()) {
            return false;
        }

        return getKeyType() == otherKey.getKeyType()
                && Arrays.equals(getEncoded(), otherKey.getEncoded());
    }
}