COSE.MacCommon.java Source code

Introduction

Here is the source code for COSE.MacCommon.java

Source

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package COSE;

import com.upokecenter.cbor.CBORObject;
import com.upokecenter.cbor.CBORType;
import java.util.ArrayList;
import java.util.List;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.digests.SHA256Digest;
import org.bouncycastle.crypto.digests.SHA384Digest;
import org.bouncycastle.crypto.digests.SHA512Digest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.params.KeyParameter;

/**
 *
 * @author jimsch
 */

public abstract class MacCommon extends Message {
    protected byte[] rgbContent;
    protected byte[] rgbTag;
    protected List<Recipient> recipientList = new ArrayList<Recipient>();
    protected String strContext;

    protected MacCommon() {
        super();
    }

    protected boolean Validate(byte[] rgbKey) throws CoseException {
        boolean f;
        int i;
        byte[] rgbTest;

        CBORObject alg = FindAttribute(CBORObject.FromObject(1)); //HeaderKeys.Algorithm);
        if (alg.getType() == CBORType.TextString) {
            throw new CoseException("Unsupported MAC Algorithm");
        } else if (alg.getType() != CBORType.Number) {
            throw new CoseException("Malformed MAC algorithm field");
        }

        switch (alg.AsInt32()) {
        case 4: // HMAC_SHA_256_64
        case 5: // HMAC_SHA_256
        case 6: // HMAC_SHA_384
        case 7: // HMAC_SHA_512
            rgbTest = HMAC(alg, rgbKey);
            break;

        default:
            throw new CoseException("Unsupported MAC Algorithm");
        }

        if (rgbTest.length != rgbTag.length)
            return false;
        f = true;
        for (i = 0; i < rgbTest.length; i++) {
            f &= (rgbTest[i] == rgbTag[i]);
        }
        return f;
    }

    private byte[] BuildContentBytes() {
        CBORObject obj = CBORObject.NewArray();

        obj.Add(strContext);
        if (objProtected.size() > 0)
            obj.Add(objProtected.EncodeToBytes());
        else
            obj.Add(CBORObject.FromObject(new byte[0]));
        if (externalData != null)
            obj.Add(CBORObject.FromObject(externalData));
        else
            obj.Add(CBORObject.FromObject(new byte[0]));
        obj.Add(rgbContent);

        return obj.EncodeToBytes();
    }

    private byte[] HMAC(CBORObject alg, byte[] rgbKey) throws CoseException {
        Digest digest;
        int cbitKey;
        int cbResult;

        switch (alg.AsInt32()) {
        case 4: // HMAC_SHA_256_64
            cbitKey = 256;
            cbResult = 64 / 8;
            digest = new SHA256Digest();
            break;

        case 5: // HMAC_SHA_256
            cbitKey = 256;
            cbResult = 256 / 8;
            digest = new SHA256Digest();
            break;

        case 6: // HMAC_SHA_384
            cbitKey = 384;
            cbResult = 384 / 8;
            digest = new SHA384Digest();
            break;

        case 7: // HMAC_SHA_512
            cbitKey = 512;
            cbResult = 512 / 8;
            digest = new SHA512Digest();
            break;

        default:
            throw new CoseException("Internal Error");
        }

        if (rgbKey.length != cbitKey / 8)
            throw new CoseException("Key is incorrect size");

        HMac hmac = new HMac(digest);
        KeyParameter key = new KeyParameter(rgbKey);
        byte[] toDigest = BuildContentBytes();

        byte[] resBuf = new byte[hmac.getMacSize()];

        hmac.init(key);
        hmac.update(toDigest, 0, toDigest.length);
        hmac.doFinal(resBuf, 0);

        byte[] returnVal = new byte[cbResult];
        System.arraycopy(resBuf, 0, returnVal, 0, cbResult);
        return returnVal;
    }
}