Don't allow empty message bodies.

bramble-api/src/main/java/org/briarproject/bramble/api/client/BdfMessageValidator.java

@@ -48,12 +48,8 @@ public abstract class BdfMessageValidator implements MessageValidator {
 			throw new InvalidMessageException(
 					"Timestamp is too far in the future");
 		}
-		byte[] body = m.getBody();
-		if (body.length == 0) {
-			throw new InvalidMessageException("Message is too short");
-		}
 		try {
-			BdfList bodyList = clientHelper.toList(body);
+			BdfList bodyList = clientHelper.toList(m.getBody());
 			BdfMessageContext result = validateMessage(m, g, bodyList);
 			Metadata meta = metadataEncoder.encode(result.getDictionary());
 			return new MessageContext(meta, result.getDependencies());

bramble-api/src/main/java/org/briarproject/bramble/api/sync/Message.java

@@ -16,6 +16,7 @@ public class Message {
 	private final byte[] body;
 
 	public Message(MessageId id, GroupId groupId, long timestamp, byte[] body) {
+		if (body.length == 0) throw new IllegalArgumentException();
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -1508,7 +1508,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			rs.close();
 			ps.close();
 			if (raw == null) throw new MessageDeletedException();
-			if (raw.length < MESSAGE_HEADER_LENGTH) throw new AssertionError();
+			if (raw.length <= MESSAGE_HEADER_LENGTH) throw new AssertionError();
 			byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
 			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 			return new Message(m, g, timestamp, body);

bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java

@@ -36,6 +36,7 @@ class MessageFactoryImpl implements MessageFactory {
 
 	@Override
 	public Message createMessage(GroupId g, long timestamp, byte[] body) {
+		if (body.length == 0) throw new IllegalArgumentException();
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
 		MessageId id = getMessageId(g, timestamp, body);
@@ -54,7 +55,7 @@ class MessageFactoryImpl implements MessageFactory {
 
 	@Override
 	public Message createMessage(byte[] raw) {
-		if (raw.length < MESSAGE_HEADER_LENGTH)
+		if (raw.length <= MESSAGE_HEADER_LENGTH)
 			throw new IllegalArgumentException();
 		if (raw.length > MAX_MESSAGE_LENGTH)
 			throw new IllegalArgumentException();

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderImpl.java

@@ -124,7 +124,8 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 		if (!hasMessage()) throw new FormatException();
 		if (nextRecord == null) throw new AssertionError();
 		byte[] payload = nextRecord.getPayload();
-		if (payload.length < MESSAGE_HEADER_LENGTH) throw new FormatException();
+		if (payload.length <= MESSAGE_HEADER_LENGTH)
+			throw new FormatException();
 		// Validate timestamp
 		long timestamp = ByteUtils.readUint64(payload, UniqueId.LENGTH);
 		if (timestamp < 0) throw new FormatException();

bramble-core/src/test/java/org/briarproject/bramble/client/BdfMessageValidatorTest.java

@@ -79,18 +79,6 @@ public class BdfMessageValidatorTest extends ValidatorTestCase {
 		assertSame(meta, messageContext.getMetadata());
 	}
 
-	@Test(expected = InvalidMessageException.class)
-	public void testRejectsTooShortMessage() throws Exception {
-		Message invalidMessage = getMessage(groupId, 0);
-
-		context.checking(new Expectations() {{
-			oneOf(clock).currentTimeMillis();
-			will(returnValue(timestamp));
-		}});
-
-		failIfSubclassIsCalled.validateMessage(invalidMessage, group);
-	}
-
 	@Test
 	public void testAcceptsMinLengthMessage() throws Exception {
 		Message shortMessage = getMessage(groupId, 1);