src/jdk.crypto.mscapi/windows/classes/sun/security/mscapi/CKey.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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package sun.security.mscapi;

import sun.security.util.KeyUtil;
import sun.security.util.Length;

import java.math.BigInteger;
import java.security.Key;
import java.security.interfaces.ECPrivateKey;
import java.security.interfaces.ECPublicKey;

/**
 * The handle for a key using the Microsoft Crypto API.
 *
 * @see CPrivateKey
 * @see CPublicKey
 *
 * @since 1.6
 * @author  Stanley Man-Kit Ho
 */
abstract class CKey implements Key, Length {
    private static final long serialVersionUID = -1088859394025049194L;

    static class NativeHandles {

        long hCryptProv = 0;
        long hCryptKey = 0;

        public NativeHandles(long hCryptProv, long hCryptKey) {
            this.hCryptProv = hCryptProv;
            this.hCryptKey = hCryptKey;
        }

        @SuppressWarnings("deprecation")
        protected void finalize() throws Throwable {
            try {
                synchronized(this) {
                    cleanUp(hCryptProv, hCryptKey);
                    hCryptProv = 0;
                    hCryptKey = 0;
                }
            } finally {
                super.finalize();
            }
        }
    }

    protected final NativeHandles handles;

    protected final int keyLength;

    protected final String algorithm;

    protected CKey(String algorithm, NativeHandles handles, int keyLength) {
        this.algorithm = algorithm;
        this.handles = handles;
        this.keyLength = keyLength;
    }

    // Native method to cleanup the key handle.
    private native static void cleanUp(long hCryptProv, long hCryptKey);

    @Override
    public int length() {
        return keyLength;
    }

    public long getHCryptKey() {
        return handles.hCryptKey;
    }

    public long getHCryptProvider() {
        return handles.hCryptProv;
    }

    public String getAlgorithm() {
        return algorithm;
    }

    protected native static String getContainerName(long hCryptProv);

    protected native static String getKeyType(long hCryptKey);

    // This java method generates EC BLOBs for public key or private key.
    // See https://docs.microsoft.com/en-us/windows/desktop/api/bcrypt/ns-bcrypt-_bcrypt_ecckey_blob
    static byte[] generateECBlob(Key k) {

        int keyBitLength = KeyUtil.getKeySize(k);
        int keyLen = (keyBitLength + 7) / 8;
        boolean isPrivate = k instanceof ECPrivateKey;

        byte[] keyBlob = new byte[8 + keyLen * (isPrivate ? 3 : 2)];
        keyBlob[0] = 'E';
        keyBlob[1] = 'C';
        keyBlob[2] = 'S';
        if (isPrivate) {
            keyBlob[3] = (byte) (keyBitLength == 256 ? '2'
                    : (keyBitLength == 384 ? '4' : '6'));
        } else {
            keyBlob[3] = (byte) (keyBitLength == 256 ? '1'
                    : (keyBitLength == 384 ? '3' : '5'));
        }
        BigInteger x;
        BigInteger y;
        // Fill the array in reverse order (s -> y -> x -> len) in case
        // one BigInteger encoding has an extra 0 at the beginning
        if (isPrivate) {
            // We can keep X and Y zero and it still works
            ECPrivateKey prk = (ECPrivateKey)k;
            BigInteger s = prk.getS();
            byte[] bs = s.toByteArray();
            System.arraycopy(
                    bs, 0,
                    keyBlob, 8 + keyLen + keyLen + keyLen - bs.length,
                    bs.length);
        } else {
            ECPublicKey puk = (ECPublicKey)k;
            x = puk.getW().getAffineX();
            y = puk.getW().getAffineY();
            byte[] by = y.toByteArray();
            System.arraycopy(by, 0, keyBlob, 8 + keyLen + keyLen - by.length,
                    by.length);
            byte[] bx = x.toByteArray();
            System.arraycopy(bx, 0, keyBlob, 8 + keyLen - bx.length, bx.length);
        }
        keyBlob[4] = (byte) keyLen;
        keyBlob[5] = keyBlob[6] = keyBlob[7] = 0;
        return keyBlob;
    }
}