nl.open.jwtdependency.org.bouncycastle.crypto.tls.TlsMac Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of java-jwt-nodependencies Show documentation
This is a drop in replacement for the auth0 java-jwt library (see https://github.com/auth0/java-jwt). This jar makes sure there are no external dependencies (e.g. fasterXml, Apacha Commons) needed. This is useful when deploying to an application server (e.g. tomcat with Alfreso or Pega).
The newest version!
package org.bouncycastle.crypto.tls;

import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.digests.LongDigest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.Arrays;

/**
 * A generic TLS MAC implementation, acting as an HMAC based on some underlying Digest.
 */
public class TlsMac
{
    protected TlsContext context;
    protected byte[] secret;
    protected Mac mac;
    protected int digestBlockSize;
    protected int digestOverhead;
    protected int macLength;

    /**
     * Generate a new instance of an TlsMac.
     *
     * @param context the TLS client context
     * @param digest  The digest to use.
     * @param key     A byte-array where the key for this MAC is located.
     * @param keyOff  The number of bytes to skip, before the key starts in the buffer.
     * @param keyLen  The length of the key.
     */
    public TlsMac(TlsContext context, Digest digest, byte[] key, int keyOff, int keyLen)
    {
        this.context = context;

        KeyParameter keyParameter = new KeyParameter(key, keyOff, keyLen);

        this.secret = Arrays.clone(keyParameter.getKey());

        // TODO This should check the actual algorithm, not rely on the engine type
        if (digest instanceof LongDigest)
        {
            this.digestBlockSize = 128;
            this.digestOverhead = 16;
        }
        else
        {
            this.digestBlockSize = 64;
            this.digestOverhead = 8;
        }

        if (TlsUtils.isSSL(context))
        {
            this.mac = new SSL3Mac(digest);

            // TODO This should check the actual algorithm, not assume based on the digest size
            if (digest.getDigestSize() == 20)
            {
                /*
                 * NOTE: When SHA-1 is used with the SSL 3.0 MAC, the secret + input pad is not
                 * digest block-aligned.
                 */
                this.digestOverhead = 4;
            }
        }
        else
        {
            this.mac = new HMac(digest);

            // NOTE: The input pad for HMAC is always a full digest block
        }

        this.mac.init(keyParameter);

        this.macLength = mac.getMacSize();
        if (context.getSecurityParameters().truncatedHMac)
        {
            this.macLength = Math.min(this.macLength, 10);
        }
    }

    /**
     * @return the MAC write secret
     */
    public byte[] getMACSecret()
    {
        return this.secret;
    }

    /**
     * @return The output length of this MAC.
     */
    public int getSize()
    {
        return macLength;
    }

    /**
     * Calculate the MAC for some given data.
     *
     * @param type    The message type of the message.
     * @param message A byte-buffer containing the message.
     * @param offset  The number of bytes to skip, before the message starts.
     * @param length  The length of the message.
     * @return A new byte-buffer containing the MAC value.
     */
    public byte[] calculateMac(long seqNo, short type, byte[] message, int offset, int length)
    {
        ProtocolVersion serverVersion = context.getServerVersion();
        boolean isSSL = serverVersion.isSSL();

        byte[] macHeader = new byte[isSSL ? 11 : 13];
        TlsUtils.writeUint64(seqNo, macHeader, 0);
        TlsUtils.writeUint8(type, macHeader, 8);
        if (!isSSL)
        {
            TlsUtils.writeVersion(serverVersion, macHeader, 9);
        }
        TlsUtils.writeUint16(length, macHeader, macHeader.length - 2);

        mac.update(macHeader, 0, macHeader.length);
        mac.update(message, offset, length);

        byte[] result = new byte[mac.getMacSize()];
        mac.doFinal(result, 0);
        return truncate(result);
    }

    public byte[] calculateMacConstantTime(long seqNo, short type, byte[] message, int offset, int length,
        int fullLength, byte[] dummyData)
    {
        /*
         * Actual MAC only calculated on 'length' bytes...
         */
        byte[] result = calculateMac(seqNo, type, message, offset, length);

        /*
         * ...but ensure a constant number of complete digest blocks are processed (as many as would
         * be needed for 'fullLength' bytes of input).
         */
        int headerLength = TlsUtils.isSSL(context) ? 11 : 13;

        // How many extra full blocks do we need to calculate?
        int extra = getDigestBlockCount(headerLength + fullLength) - getDigestBlockCount(headerLength + length);

        while (--extra >= 0)
        {
            mac.update(dummyData, 0, digestBlockSize);
        }

        // One more byte in case the implementation is "lazy" about processing blocks
        mac.update(dummyData[0]);
        mac.reset();

        return result;
    }

    protected int getDigestBlockCount(int inputLength)
    {
        // NOTE: This calculation assumes a minimum of 1 pad byte
        return (inputLength + digestOverhead) / digestBlockSize;
    }

    protected byte[] truncate(byte[] bs)
    {
        if (bs.length <= macLength)
        {
            return bs;
        }

        return Arrays.copyOf(bs, macLength);
    }
}