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The Bouncy Castle Java APIs for the TLS, including a JSSE provider. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.

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package org.bouncycastle.tls.crypto.impl;

import java.io.IOException;

import org.bouncycastle.tls.crypto.TlsCertificate;
import org.bouncycastle.tls.crypto.TlsCipher;
import org.bouncycastle.tls.crypto.TlsCrypto;
import org.bouncycastle.tls.crypto.TlsCryptoParameters;
import org.bouncycastle.tls.crypto.TlsHMAC;
import org.bouncycastle.tls.crypto.TlsSecret;
import org.bouncycastle.util.Arrays;

/**
 * Base class for a TlsSecret implementation which captures common code and fields.
 */
public abstract class AbstractTlsSecret
    implements TlsSecret
{
    protected byte[] data;

    /**
     * Base constructor.
     *
     * @param data the byte[] making up the secret value.
     */
    protected AbstractTlsSecret(byte[] data)
    {
        this.data = data;
    }

    protected abstract TlsSecret adoptLocalSecret(byte[] data);

    protected void checkAlive()
    {
        if (data == null)
        {
            throw new IllegalStateException("Secret has already been extracted or destroyed");
        }
    }

    protected abstract AbstractTlsCrypto getCrypto();

    public TlsCipher createCipher(TlsCryptoParameters cryptoParams, int encryptionAlgorithm, int macAlgorithm)
        throws IOException
    {
        return getCrypto().createCipher(cryptoParams, encryptionAlgorithm, macAlgorithm);
    }

    public synchronized void destroy()
    {
        if (data != null)
        {
            // TODO Is there a way to ensure the data is really overwritten?
            Arrays.fill(data, (byte)0);
            this.data = null;
        }
    }

    public synchronized byte[] encrypt(TlsCertificate certificate) throws IOException
    {
        checkAlive();

        return getCrypto().createEncryptor(certificate).encrypt(data, 0, data.length);
    }

    public synchronized byte[] extract()
    {
        checkAlive();

        byte[] result = data;
        this.data = null;
        return result;
    }

    public synchronized TlsSecret hkdfExpand(short hashAlgorithm, byte[] info, int length)
    {
        checkAlive();

        byte[] prk = data;

        TlsCrypto crypto = getCrypto();
        TlsHMAC hmac = crypto.createHMAC(hashAlgorithm);

        hmac.setKey(prk, 0, prk.length);

        byte[] okm = new byte[length];

        int hashLen = hmac.getMacLength();
        byte[] t = new byte[hashLen];
        byte counter = 0x00;

        int pos = 0;
        while (pos < length)
        {
            if (counter != 0x00)
            {
                hmac.update(t, 0, t.length);
            }
            hmac.update(info, 0, info.length);
            hmac.update(new byte[]{ ++counter }, 0, 1);

            hmac.calculateMAC(t, 0);

            int copyLength = Math.min(hashLen, length - pos);
            System.arraycopy(t, 0, okm, pos, copyLength);
            pos += copyLength;
        }

        return adoptLocalSecret(okm);
    }

    public synchronized TlsSecret hkdfExtract(short hashAlgorithm, byte[] ikm)
    {
        checkAlive();

        byte[] salt = data;

        TlsCrypto crypto = getCrypto();
        TlsHMAC hmac = crypto.createHMAC(hashAlgorithm);

        hmac.setKey(salt, 0, salt.length);
        hmac.update(ikm, 0, ikm.length);

        byte[] prk = hmac.calculateMAC();

        return adoptLocalSecret(prk);
    }

    synchronized byte[] copyData()
    {
        return Arrays.clone(data);
    }
}