Replace message separation marker with message length prefix in digest as well

meerkat-common/src/main/java/meerkat/crypto/Digest.java

@@ -8,13 +8,6 @@ import java.security.MessageDigest;
  * Created by talm on 11/9/15.
  */
 public interface Digest {
-
-    /**
-     * Marker between messages
-     */
-    public static final byte[] CONCAT_MARKER = {(byte) 0xde, (byte) 0xad, (byte) 0xbe, (byte) 0xef,
-            (byte) 0xba, (byte) 0x1d, (byte) 0xfa, (byte) 0xce};
-
     /**
      * Completes the hash computation by performing final operations such as padding.
      * (copied from {@link MessageDigest#digest()})
@@ -25,9 +18,7 @@ public interface Digest {
     /**
      * Updates the digest using the specified message (in serialized wire form)
      *
-     * Includes a special message concatenation marker (the 64 bit message {@link #CONCAT_MARKER}) in the digest (digesting a single message
-     * will give a different result than the same message split into two messages).
-     * Messages must not contain the {@link #CONCAT_MARKER}) marker.
+     * Each message is (automatically) prepended with its length as a 32-bit big-endian unsigned integer.
      * @param msg
      * @return
      */

meerkat-common/src/main/java/meerkat/crypto/DigitalSignature.java

@@ -41,8 +41,8 @@ public interface DigitalSignature {
 
 
     /**
-     * Add msg to the content stream to be verified / signed. Each message is always (automatically)
-     * prepended with its length as a 32-bit unsigned integer in network byte order.
+     * Add msg to the content stream to be verified / signed. Each message is (automatically)
+     * prepended with its length as a 32-bit big-endian unsigned integer.
      *
      * @param msg
      * @throws SignatureException

meerkat-common/src/main/java/meerkat/crypto/concrete/ECDSASignature.java

@@ -2,13 +2,13 @@ package meerkat.crypto.concrete;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.ByteBuffer;
 import java.security.*;
 import java.security.cert.*;
 import java.security.cert.Certificate;
 import java.util.*;
 
 import com.google.protobuf.ByteString;
-import meerkat.crypto.Digest;
 import meerkat.protobuf.Crypto;
 import meerkat.util.Hex;
 import org.slf4j.Logger;
@@ -27,7 +27,7 @@ import javax.security.auth.callback.UnsupportedCallbackException;
 
 /**
  * Sign and verify digital signatures.
- * <p/>
+ *
  * This class is not thread-safe (each thread should have its own instance).
  */
 public class ECDSASignature extends GlobalCryptoSetup implements DigitalSignature {
@@ -38,6 +38,12 @@ public class ECDSASignature extends GlobalCryptoSetup implements DigitalSignatur
 
     SHA256Digest digest = new SHA256Digest();
 
+    /**
+     * Buffer used to hold length in for hash update
+     */
+    ByteBuffer lenBuf = ByteBuffer.allocate(4);
+
+
     Map<ByteString, Certificate> loadedCertificates = new HashMap<>();
 
     /**
@@ -111,7 +117,7 @@ public class ECDSASignature extends GlobalCryptoSetup implements DigitalSignatur
 
     /**
      * Add the list of messages to the stream that is being verified/signed.
-     * Messages are separated with {@link Digest#CONCAT_MARKER}
+     * Messages are prepended with their length in 32-bit big-endian format.
      *
      * @param msg
      * @throws SignatureException
@@ -119,10 +125,11 @@ public class ECDSASignature extends GlobalCryptoSetup implements DigitalSignatur
     @Override
     public void updateContent(Message msg) throws SignatureException {
         assert msg != null;
-        int len = msg.getSerializedSize();
 
-        byte[] lenBytes = { (byte) ((len >>> 24) & 0xff), (byte) ((len >>> 16) & 0xff), (byte) ((len >>> 8) & 0xff), (byte) (len & 0xff) };
-        signer.update(lenBytes);
+        lenBuf.clear();
+        lenBuf.putInt(msg.getSerializedSize());
+        lenBuf.flip();
+        signer.update(lenBuf);
         signer.update(msg.toByteString().asReadOnlyByteBuffer());
     }
 

meerkat-common/src/main/java/meerkat/crypto/concrete/SHA256Digest.java

@@ -6,6 +6,7 @@ import meerkat.crypto.Digest;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.nio.ByteBuffer;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 
@@ -18,6 +19,11 @@ public class SHA256Digest extends GlobalCryptoSetup implements Digest {
 
     MessageDigest hash;
 
+    /**
+     * Used to convert length to bytes in proper order.
+     */
+    ByteBuffer lenBuf = ByteBuffer.allocate(4);
+
     /**
      * Instantiate with a specified algorithm.
      * @param algorithm
@@ -56,6 +62,11 @@ public class SHA256Digest extends GlobalCryptoSetup implements Digest {
 
     @Override
     public void update(Message msg) {
+
+        lenBuf.clear();
+        lenBuf.putInt(msg.getSerializedSize());
+        lenBuf.flip();
+        hash.update(lenBuf);
         hash.update(msg.toByteString().asReadOnlyByteBuffer());
     }