Make it possible to deserialize SenderKeyDistributionMessages

java/src/main/java/org/whispersystems/libaxolotl/protocol/SenderKeyDistributionMessage.java

@@ -1,7 +1,12 @@
 package org.whispersystems.libaxolotl.protocol;
 
 import com.google.protobuf.ByteString;
+import com.google.protobuf.InvalidProtocolBufferException;
 
+import org.whispersystems.libaxolotl.InvalidKeyException;
+import org.whispersystems.libaxolotl.InvalidMessageException;
+import org.whispersystems.libaxolotl.LegacyMessageException;
+import org.whispersystems.libaxolotl.ecc.Curve;
 import org.whispersystems.libaxolotl.ecc.ECPublicKey;
 import org.whispersystems.libaxolotl.util.ByteUtil;
 
@@ -15,17 +20,52 @@ public class SenderKeyDistributionMessage implements CiphertextMessage {
 
   public SenderKeyDistributionMessage(int id, int iteration, byte[] chainKey, ECPublicKey signatureKey) {
     byte[] version = {ByteUtil.intsToByteHighAndLow(CURRENT_VERSION, CURRENT_VERSION)};
-
+    byte[] protobuf = WhisperProtos.SenderKeyDistributionMessage.newBuilder()
-    this.id           = id;
-    this.iteration    = iteration;
-    this.chainKey     = chainKey;
-    this.signatureKey = signatureKey;
-    this.serialized   = WhisperProtos.SenderKeyDistributionMessage.newBuilder()
                                                                 .setId(id)
                                                                 .setIteration(iteration)
                                                                 .setChainKey(ByteString.copyFrom(chainKey))
                                                                 .setSigningKey(ByteString.copyFrom(signatureKey.serialize()))
                                                                 .build().toByteArray();
+
+    this.id           = id;
+    this.iteration    = iteration;
+    this.chainKey     = chainKey;
+    this.signatureKey = signatureKey;
+    this.serialized   = ByteUtil.combine(version, protobuf);
+  }
+
+  public SenderKeyDistributionMessage(byte[] serialized) throws LegacyMessageException, InvalidMessageException {
+    try {
+      byte[][] messageParts = ByteUtil.split(serialized, 1, serialized.length - 1);
+      byte     version      = messageParts[0][0];
+      byte[]   message      = messageParts[1];
+
+      if (ByteUtil.highBitsToInt(version) < CiphertextMessage.CURRENT_VERSION) {
+        throw new LegacyMessageException("Legacy message: " + ByteUtil.highBitsToInt(version));
+      }
+
+      if (ByteUtil.highBitsToInt(version) > CURRENT_VERSION) {
+        throw new InvalidMessageException("Unknown version: " + ByteUtil.highBitsToInt(version));
+      }
+
+      WhisperProtos.SenderKeyDistributionMessage distributionMessage = WhisperProtos.SenderKeyDistributionMessage.parseFrom(message);
+
+      if (!distributionMessage.hasId()        ||
+          !distributionMessage.hasIteration() ||
+          !distributionMessage.hasChainKey()  ||
+          !distributionMessage.hasSigningKey())
+      {
+        throw new InvalidMessageException("Incomplete message.");
+      }
+
+      this.serialized   = serialized;
+      this.id           = distributionMessage.getId();
+      this.iteration    = distributionMessage.getIteration();
+      this.chainKey     = distributionMessage.getChainKey().toByteArray();
+      this.signatureKey = Curve.decodePoint(distributionMessage.getSigningKey().toByteArray(), 0);
+    } catch (InvalidProtocolBufferException | InvalidKeyException e) {
+      throw new InvalidMessageException(e);
+    }
   }
 
   @Override

tests/src/test/java/org/whispersystems/libaxolotl/groups/GroupCipherTest.java

@@ -30,9 +30,9 @@ public class GroupCipherTest extends TestCase {
     GroupCipher aliceGroupCipher = new GroupCipher(aliceStore, GROUP_SENDER);
     GroupCipher bobGroupCipher   = new GroupCipher(bobStore, GROUP_SENDER);
 
-    SenderKeyDistributionMessage aliceDistributionMessage = aliceSessionBuilder.create(GROUP_SENDER);
+    SenderKeyDistributionMessage sentAliceDistributionMessage     = aliceSessionBuilder.create(GROUP_SENDER);
-
+    SenderKeyDistributionMessage receivedAliceDistributionMessage = new SenderKeyDistributionMessage(sentAliceDistributionMessage.serialize());
-    bobSessionBuilder.process(GROUP_SENDER, aliceDistributionMessage);
+    bobSessionBuilder.process(GROUP_SENDER, receivedAliceDistributionMessage);
 
     byte[] ciphertextFromAlice = aliceGroupCipher.encrypt("smert ze smert".getBytes());
     byte[] plaintextFromAlice  = bobGroupCipher.decrypt(ciphertextFromAlice);
@@ -54,10 +54,12 @@ public class GroupCipherTest extends TestCase {
     GroupCipher aliceGroupCipher = new GroupCipher(aliceStore, aliceName);
     GroupCipher bobGroupCipher   = new GroupCipher(bobStore, aliceName);
 
-    SenderKeyDistributionMessage aliceDistributionMessage =
+    SenderKeyDistributionMessage sentAliceDistributionMessage =
         aliceSessionBuilder.create(aliceName);
+    SenderKeyDistributionMessage receivedAliceDistributionMessage =
+        new SenderKeyDistributionMessage(sentAliceDistributionMessage.serialize());
 
-    bobSessionBuilder.process(aliceName, aliceDistributionMessage);
+    bobSessionBuilder.process(aliceName, receivedAliceDistributionMessage);
 
     byte[] ciphertextFromAlice  = aliceGroupCipher.encrypt("smert ze smert".getBytes());
     byte[] ciphertextFromAlice2 = aliceGroupCipher.encrypt("smert ze smert2".getBytes());
@@ -80,6 +82,40 @@ public class GroupCipherTest extends TestCase {
     assertTrue(new String(plaintextFromAlice3).equals("smert ze smert3"));
   }
 
+  public void testLateJoin() throws NoSessionException, InvalidMessageException, LegacyMessageException, DuplicateMessageException {
+    InMemorySenderKeyStore aliceStore = new InMemorySenderKeyStore();
+    InMemorySenderKeyStore bobStore   = new InMemorySenderKeyStore();
+
+    GroupSessionBuilder aliceSessionBuilder = new GroupSessionBuilder(aliceStore);
+
+
+    SenderKeyName aliceName = GROUP_SENDER;
+
+    GroupCipher aliceGroupCipher = new GroupCipher(aliceStore, aliceName);
+
+
+    SenderKeyDistributionMessage aliceDistributionMessage = aliceSessionBuilder.create(aliceName);
+    // Send off to some people.
+
+    for (int i=0;i<100;i++) {
+      aliceGroupCipher.encrypt("up the punks up the punks up the punks".getBytes());
+    }
+
+    // Now Bob Joins.
+    GroupSessionBuilder bobSessionBuilder = new GroupSessionBuilder(bobStore);
+    GroupCipher         bobGroupCipher    = new GroupCipher(bobStore, aliceName);
+
+
+    SenderKeyDistributionMessage distributionMessageToBob = aliceSessionBuilder.create(aliceName);
+    bobSessionBuilder.process(aliceName, new SenderKeyDistributionMessage(distributionMessageToBob.serialize()));
+
+    byte[] ciphertext = aliceGroupCipher.encrypt("welcome to the group".getBytes());
+    byte[] plaintext  = bobGroupCipher.decrypt(ciphertext);
+
+    assertEquals(new String(plaintext), "welcome to the group");
+  }
+
+
   public void testOutOfOrder()
       throws LegacyMessageException, DuplicateMessageException, InvalidMessageException, NoSessionException
   {