CipherWithWrappingSpi.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * accompanied this code).
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package com.sun.crypto.provider;

import java.security.Key;
import java.security.PublicKey;
import java.security.PrivateKey;
import java.security.KeyFactory;
import java.security.InvalidKeyException;
import java.security.NoSuchProviderException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.Cipher;
import javax.crypto.CipherSpi;
import javax.crypto.SecretKey;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.BadPaddingException;
import javax.crypto.spec.SecretKeySpec;

/**
 * This class entends the javax.crypto.CipherSpi class with a concrete
 * implementation of the methods for wrapping and unwrapping
 * keys.
 *
 * @author Sharon Liu
 *
 *
 * @see javax.crypto.CipherSpi
 * @see BlowfishCipher
 * @see DESCipher
 * @see PBEWithMD5AndDESCipher
 */

public abstract class CipherWithWrappingSpi extends CipherSpi {

    /**
     * Wrap a key.
     *
     * @param key the key to be wrapped.
     *
     * @return the wrapped key.
     *
     * @exception IllegalBlockSizeException if this cipher is a block
     * cipher, no padding has been requested, and the length of the
     * encoding of the key to be wrapped is not a
     * multiple of the block size.
     *
     * @exception InvalidKeyException if it is impossible or unsafe to
     * wrap the key with this cipher (e.g., a hardware protected key is
     * being passed to a software only cipher).
     */
    protected final byte[] engineWrap(Key key)
        throws IllegalBlockSizeException, InvalidKeyException
    {
        byte[] result = null;

        try {
            byte[] encodedKey = key.getEncoded();
            if ((encodedKey == null) || (encodedKey.length == 0)) {
                throw new InvalidKeyException("Cannot get an encoding of " +
                                              "the key to be wrapped");
            }

            result = engineDoFinal(encodedKey, 0, encodedKey.length);
        } catch (BadPaddingException e) {
            // Should never happen
        }

        return result;
    }

    /**
     * Unwrap a previously wrapped key.
     *
     * @param wrappedKey the key to be unwrapped.
     *
     * @param wrappedKeyAlgorithm the algorithm the wrapped key is for.
     *
     * @param wrappedKeyType the type of the wrapped key.
     * This is one of <code>Cipher.SECRET_KEY</code>,
     * <code>Cipher.PRIVATE_KEY</code>, or <code>Cipher.PUBLIC_KEY</code>.
     *
     * @return the unwrapped key.
     *
     * @exception InvalidKeyException if <code>wrappedKey</code> does not
     * represent a wrapped key, or if the algorithm associated with the
     * wrapped key is different from <code>wrappedKeyAlgorithm</code>
     * and/or its key type is different from <code>wrappedKeyType</code>.
     *
     * @exception NoSuchAlgorithmException if no installed providers
     * can create keys for the <code>wrappedKeyAlgorithm</code>.
     */
    protected final Key engineUnwrap(byte[] wrappedKey,
                                     String wrappedKeyAlgorithm,
                                     int wrappedKeyType)
        throws InvalidKeyException, NoSuchAlgorithmException
    {
        byte[] encodedKey;
        Key result = null;

        try {
            encodedKey = engineDoFinal(wrappedKey, 0,
                                       wrappedKey.length);
        } catch (BadPaddingException ePadding) {
            throw new InvalidKeyException();
        } catch (IllegalBlockSizeException eBlockSize) {
            throw new InvalidKeyException();
        }

        switch (wrappedKeyType) {
        case Cipher.SECRET_KEY:
            result = constructSecretKey(encodedKey,
                                        wrappedKeyAlgorithm);
            break;
        case Cipher.PRIVATE_KEY:
            result = constructPrivateKey(encodedKey,
                                         wrappedKeyAlgorithm);
            break;
        case Cipher.PUBLIC_KEY:
            result = constructPublicKey(encodedKey,
                                        wrappedKeyAlgorithm);
            break;
        }

        return result;

    }

    /**
     * Construct a public key from its encoding.
     *
     * @param encodedKey the encoding of a public key.
     *
     * @param encodedKeyAlgorithm the algorithm the encodedKey is for.
     *
     * @return a public key constructed from the encodedKey.
     */
    private final PublicKey constructPublicKey(byte[] encodedKey,
                                               String encodedKeyAlgorithm)
        throws InvalidKeyException, NoSuchAlgorithmException
    {
        PublicKey key = null;

        try {
            KeyFactory keyFactory =
                KeyFactory.getInstance(encodedKeyAlgorithm,
                    SunJCE.getInstance());
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encodedKey);
            key = keyFactory.generatePublic(keySpec);
        } catch (NoSuchAlgorithmException nsae) {
            // Try to see whether there is another
            // provider which supports this algorithm
            try {
                KeyFactory keyFactory =
                    KeyFactory.getInstance(encodedKeyAlgorithm);
                X509EncodedKeySpec keySpec =
                    new X509EncodedKeySpec(encodedKey);
                key = keyFactory.generatePublic(keySpec);
            } catch (NoSuchAlgorithmException nsae2) {
                throw new NoSuchAlgorithmException("No installed providers " +
                                                   "can create keys for the " +
                                                   encodedKeyAlgorithm +
                                                   "algorithm");
            } catch (InvalidKeySpecException ikse2) {
                // Should never happen.
            }
        } catch (InvalidKeySpecException ikse) {
            // Should never happen.
        }

        return key;
    }

    /**
     * Construct a private key from its encoding.
     *
     * @param encodedKey the encoding of a private key.
     *
     * @param encodedKeyAlgorithm the algorithm the wrapped key is for.
     *
     * @return a private key constructed from the encodedKey.
     */
    private final PrivateKey constructPrivateKey(byte[] encodedKey,
                                                 String encodedKeyAlgorithm)
        throws InvalidKeyException, NoSuchAlgorithmException
    {
        PrivateKey key = null;

        try {
            KeyFactory keyFactory =
                KeyFactory.getInstance(encodedKeyAlgorithm,
                    SunJCE.getInstance());
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encodedKey);
            return keyFactory.generatePrivate(keySpec);
        } catch (NoSuchAlgorithmException nsae) {
            // Try to see whether there is another
            // provider which supports this algorithm
            try {
                KeyFactory keyFactory =
                    KeyFactory.getInstance(encodedKeyAlgorithm);
                PKCS8EncodedKeySpec keySpec =
                    new PKCS8EncodedKeySpec(encodedKey);
                key = keyFactory.generatePrivate(keySpec);
            } catch (NoSuchAlgorithmException nsae2) {
                throw new NoSuchAlgorithmException("No installed providers " +
                                                   "can create keys for the " +
                                                   encodedKeyAlgorithm +
                                                   "algorithm");
            } catch (InvalidKeySpecException ikse2) {
                // Should never happen.
            }
        } catch (InvalidKeySpecException ikse) {
            // Should never happen.
        }

        return key;
    }

    /**
     * Construct a secret key from its encoding.
     *
     * @param encodedKey the encoding of a secret key.
     *
     * @param encodedKeyAlgorithm the algorithm the secret key is for.
     *
     * @return a secret key constructed from the encodedKey.
     */
    private final SecretKey constructSecretKey(byte[] encodedKey,
                                               String encodedKeyAlgorithm)
    {
        return (new SecretKeySpec(encodedKey, encodedKeyAlgorithm));
    }
}