Add hashing functionality

src/main/java/COSE/AlgorithmID.java

@@ -58,7 +58,12 @@ public enum AlgorithmID {
 
     RSA_PSS_256(-37, 0, 0),
     RSA_PSS_384(-38, 0, 0),
-    RSA_PSS_512(-39, 0, 0),
+    RSA_PSS_512(-39, 0, 0), 
+
+    SHA_512(0, 512, 0),
+    SHA_256(0, 256, 0),
+    SHA3_512(0, 512, 0),
+    SHA3_256(0, 256, 0)
     ;
 
     private final CBORObject value;

src/main/java/COSE/HashCommon.java

@@ -0,0 +1,54 @@
+package COSE;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+public abstract class HashCommon extends Message {
+
+	protected String contextString;
+	protected byte[] rgbHash;
+
+	byte[] computeHash(byte[] rgbToBeSigned) throws CoseException {
+		AlgorithmID alg = AlgorithmID.FromCBOR(findAttribute(HeaderKeys.Algorithm));
+		return computeHash(alg, rgbToBeSigned);
+	}
+
+	protected byte[] computeHash(AlgorithmID alg, byte[] rgbToBeHashed) throws CoseException {
+		String algName = null;
+
+		switch (alg) {
+		case SHA_512:
+			algName = "SHA-512";
+			break;
+		case SHA_256:
+			algName = "SHA-256";
+			break;
+		case SHA3_512:
+			algName = "SHA3-512";
+			break;
+		case SHA3_256:
+			algName = "SHA3-256";
+			break;
+
+        default:
+			throw new CoseException("Unsupported Algorithm Specified");
+		}
+
+		try {
+			MessageDigest messageDigest = MessageDigest.getInstance(algName);
+			rgbHash = messageDigest.digest(rgbToBeHashed);
+			return rgbHash;
+		} catch (NoSuchAlgorithmException e) {
+			throw new CoseException("Hashing not possible. Unsupported Algorithm Specified");
+		}
+
+	}
+
+	public byte[] getHashedContent() throws CoseException {
+		if (rgbHash == null)
+			throw new CoseException("No hashed Content Specified");
+
+		return rgbHash;
+	}
+
+}

src/main/java/COSE/HashMessage.java

@@ -0,0 +1,132 @@
+package COSE;
+
+import com.upokecenter.cbor.CBORObject;
+import com.upokecenter.cbor.CBORType;
+
+public class HashMessage extends HashCommon {
+	/**
+	 * Create a HashMessage object. This object corresponds to the encrypt message
+	 * format in COSE. The leading CBOR tag will be emitted. The message content
+	 * will be emitted.
+	 */
+	public HashMessage() {
+		this(true, true);
+	}
+
+	/**
+	 * Create a HashMessage object. Emission of the leading tag is controlled by the
+	 * parameter.
+	 * 
+	 * @param emitTag emit leading tag when message is serialized
+	 */
+	public HashMessage(boolean emitTag) {
+		this(emitTag, true);
+	}
+
+	/**
+	 * Create a HashMessage object for which the emission of the leading tag and
+	 * content is controlled by the parameters.
+	 * 
+	 * @param emitTag     emit leading tag when message is serialized
+	 * @param emitContent emit the content as part of the message
+	 */
+	public HashMessage(boolean emitTag, boolean emitContent) {
+		this.emitTag = emitTag;
+		this.contextString = "Hash";
+		this.emitContent = emitContent;
+		this.messageTag = MessageTag.Hash;
+	}
+
+	/**
+	 * Create a hash for the message if one does not exist.
+	 * 
+	 * @throws CoseException
+	 */
+	public void hash() throws CoseException {
+		if (rgbContent == null)
+			throw new CoseException("No Content Specified");
+		if (rgbHash != null)
+			return;
+
+		if (rgbProtected == null) {
+			if (objProtected.size() > 0)
+				rgbProtected = objProtected.EncodeToBytes();
+			else
+				rgbProtected = new byte[0];
+		}
+
+		CBORObject obj = CBORObject.NewArray();
+		obj.Add(contextString);
+		obj.Add(rgbProtected);
+		obj.Add(externalData);
+		obj.Add(rgbContent);
+
+		rgbHash = computeHash(rgbContent);
+
+	}
+
+	/**
+	 * Internal function used in creating a HashMessage object from a byte string.
+	 * 
+	 * @param messageObject HashMessage encoded object.
+	 * @throws CoseException Errors generated by the COSE module
+	 */
+	@Override
+	protected void DecodeFromCBORObject(CBORObject messageObject) throws CoseException {
+		if (messageObject.size() != 4)
+			throw new CoseException("Invalid Hash structure");
+
+		if (messageObject.get(0).getType() == CBORType.ByteString) {
+			rgbProtected = messageObject.get(0).GetByteString();
+			if (messageObject.get(0).GetByteString().length == 0)
+				objProtected = CBORObject.NewMap();
+			else {
+				objProtected = CBORObject.DecodeFromBytes(rgbProtected);
+				if (objProtected.size() == 0)
+					rgbProtected = new byte[0];
+			}
+		} else
+			throw new CoseException("Invalid Hash structure");
+
+		if (messageObject.get(1).getType() == CBORType.Map) {
+			objUnprotected = messageObject.get(1);
+		} else
+			throw new CoseException("Invalid Hash structure");
+
+		if (messageObject.get(2).getType() == CBORType.ByteString)
+			rgbContent = messageObject.get(2).GetByteString();
+		else if (!messageObject.get(2).isNull())
+			throw new CoseException("Invalid Hash structure");
+
+		if (messageObject.get(3).getType() == CBORType.ByteString)
+			rgbHash = messageObject.get(3).GetByteString();
+		else
+			throw new CoseException("Invalid Hash structure");
+	}
+
+	/**
+	 * Internal function used to create a serialization of a HashMessage 
+	 * 
+	 * @return CBOR object which can be encoded.
+	 * @throws CoseException Errors generated by the COSE module
+	 */
+	@Override
+	protected CBORObject EncodeCBORObject() throws CoseException {
+		if (rgbHash == null)
+			throw new CoseException("hash function not called");
+		if (rgbProtected == null)
+			throw new CoseException("Internal Error");
+
+		CBORObject obj = CBORObject.NewArray();
+		obj.Add(rgbProtected);
+		obj.Add(objUnprotected);
+		if (emitContent)
+			obj.Add(rgbContent);
+		else
+			obj.Add(null);
+		obj.Add(rgbHash);
+
+		return obj;
+	}
+
+}

src/main/java/COSE/Message.java

@@ -39,6 +39,7 @@ public abstract class Message extends Attribute {
      * What is the plain text content of the message.
      */
     protected byte[] rgbContent = null;
+
 
     /**
      * Decode a COSE message object.  This function assumes that the message
@@ -108,7 +109,11 @@ else if (defaultTag != MessageTag.FromInt(messageObject.getMostInnerTag().ToInt3
             case Sign:
                 msg = new SignMessage();
                 break;
-
+
+            case Hash:
+                msg = new HashMessage();
+                break;
+
             default:
                 throw new CoseException("Message is not recognized as a COSE security Object");
         }

src/main/java/COSE/MessageTag.java

@@ -16,7 +16,8 @@ public enum MessageTag {
     Sign1(18),
     Sign(98),
     MAC(97),
-    MAC0(17);
+    MAC0(17), 
+    Hash(20);
 
     public final int value;