Basic Ibft message validators (#314)

6 years ago · a8b52e19f5
parent 14957899d6
commit a8b52e19f5
4 changed files with 485 additions and 1 deletions
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashing.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashing.java
@ -41,6 +41,11 @@ public class IbftBlockHashing {
    return Hash.hash(serializeHeader(header, ibftExtraData::encodeWithoutCommitSeals));
  }

+  public static Hash calculateDataHashForCommittedSeal(final BlockHeader header) {
+    final IbftExtraData ibftExtraData = IbftExtraData.decode(header.getExtraData());
+    return Hash.hash(serializeHeader(header, ibftExtraData::encodeWithoutCommitSeals));
+  }
+
  /**
   * Constructs a hash of the block header, but omits the committerSeals and sets round number to 0
   * (as these change on each of the potentially circulated blocks at the current chain height).
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ibftmessagedata/IbftUnsignedPrePrepareMessageData.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ibftmessagedata/IbftUnsignedPrePrepareMessageData.java
@ -36,7 +36,8 @@ public class IbftUnsignedPrePrepareMessageData extends AbstractIbftUnsignedInRou

    rlpInput.enterList();
    final ConsensusRoundIdentifier roundIdentifier = ConsensusRoundIdentifier.readFrom(rlpInput);
-    final Block block = Block.readFrom(rlpInput, IbftBlockHashing::calculateHashOfIbftBlockOnChain);
+    final Block block =
+        Block.readFrom(rlpInput, IbftBlockHashing::calculateDataHashForCommittedSeal);
    rlpInput.leaveList();

    return new IbftUnsignedPrePrepareMessageData(roundIdentifier, block);
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/validation/MessageValidator.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/validation/MessageValidator.java
@ -0,0 +1,204 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.validation;
+
+import static tech.pegasys.pantheon.ethereum.mainnet.HeaderValidationMode.FULL;
+
+import tech.pegasys.pantheon.consensus.ibft.ConsensusRoundIdentifier;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.AbstractIbftUnsignedInRoundMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftSignedMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedCommitMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedPrePrepareMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedPrepareMessageData;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.Block;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.ethereum.mainnet.BlockHeaderValidator;
+
+import java.util.Collection;
+import java.util.Optional;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+public class MessageValidator {
+
+  private static final Logger LOG = LogManager.getLogger();
+
+  private final Collection<Address> validators;
+  private final Address expectedProposer;
+  private final ConsensusRoundIdentifier roundIdentifier;
+  private final BlockHeaderValidator<IbftContext> headerValidator;
+  private final ProtocolContext<IbftContext> protocolContext;
+  private final BlockHeader parentHeader;
+
+  private Optional<IbftSignedMessageData<IbftUnsignedPrePrepareMessageData>> preprepareMessage =
+      Optional.empty();
+
+  public MessageValidator(
+      final Collection<Address> validators,
+      final Address expectedProposer,
+      final ConsensusRoundIdentifier roundIdentifier,
+      final BlockHeaderValidator<IbftContext> headerValidator,
+      final ProtocolContext<IbftContext> protocolContext,
+      final BlockHeader parentHeader) {
+    this.validators = validators;
+    this.expectedProposer = expectedProposer;
+    this.roundIdentifier = roundIdentifier;
+    this.headerValidator = headerValidator;
+    this.protocolContext = protocolContext;
+    this.parentHeader = parentHeader;
+  }
+
+  public boolean addPreprepareMessage(
+      final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> msg) {
+
+    if (preprepareMessage.isPresent()) {
+      return handleSubsequentPreprepareMessage(preprepareMessage.get(), msg);
+    }
+
+    if (!validatePreprepareMessage(msg)) {
+      return false;
+    }
+
+    preprepareMessage = Optional.of(msg);
+    return true;
+  }
+
+  private boolean validatePreprepareMessage(
+      final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> msg) {
+
+    if (!msg.getUnsignedMessageData().getRoundIdentifier().equals(roundIdentifier)) {
+      LOG.info("Invalid Preprepare message, does not match current round.");
+      return false;
+    }
+
+    if (!msg.getSender().equals(expectedProposer)) {
+      LOG.info(
+          "Invalid Preprepare message, was not created by the proposer expected for the "
+              + "associated round.");
+      return false;
+    }
+
+    final Block proposedBlock = msg.getUnsignedMessageData().getBlock();
+    if (!headerValidator.validateHeader(
+        proposedBlock.getHeader(), parentHeader, protocolContext, FULL)) {
+      LOG.info("Invalid Prepare message, block did not pass header validation.");
+      return false;
+    }
+
+    return true;
+  }
+
+  private boolean handleSubsequentPreprepareMessage(
+      final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> existingMsg,
+      final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> newMsg) {
+    if (!existingMsg.getSender().equals(newMsg.getSender())) {
+      LOG.debug("Received subsequent invalid Preprepare message; sender differs from original.");
+      return false;
+    }
+
+    final IbftUnsignedPrePrepareMessageData existingData = existingMsg.getUnsignedMessageData();
+    final IbftUnsignedPrePrepareMessageData newData = newMsg.getUnsignedMessageData();
+
+    if (!preprepareMessagesAreIdentical(existingData, newData)) {
+      LOG.debug("Received subsequent invalid Preprepare message; content differs from original.");
+      return false;
+    }
+
+    return true;
+  }
+
+  public boolean validatePrepareMessage(
+      final IbftSignedMessageData<IbftUnsignedPrepareMessageData> msg) {
+    final String msgType = "Prepare";
+
+    if (!isMessageForCurrentRoundFromValidatorAndPreprareMessageAvailable(msg, msgType)) {
+      return false;
+    }
+
+    if (msg.getSender().equals(expectedProposer)) {
+      LOG.info("Illegal Prepare message; was sent by the round's proposer.");
+      return false;
+    }
+
+    return validateDigestMatchesPreprepareBlock(msg.getUnsignedMessageData().getDigest(), msgType);
+  }
+
+  public boolean validateCommmitMessage(
+      final IbftSignedMessageData<IbftUnsignedCommitMessageData> msg) {
+    final String msgType = "Commit";
+
+    if (!isMessageForCurrentRoundFromValidatorAndPreprareMessageAvailable(msg, msgType)) {
+      return false;
+    }
+
+    final Block proposedBlock = preprepareMessage.get().getUnsignedMessageData().getBlock();
+    final Address commitSealCreator =
+        Util.signatureToAddress(
+            msg.getUnsignedMessageData().getCommitSeal(), proposedBlock.getHash());
+
+    if (!commitSealCreator.equals(msg.getSender())) {
+      LOG.info("Invalid Commit message. Seal was not created by the message transmitter.");
+      return false;
+    }
+
+    return validateDigestMatchesPreprepareBlock(msg.getUnsignedMessageData().getDigest(), msgType);
+  }
+
+  private boolean isMessageForCurrentRoundFromValidatorAndPreprareMessageAvailable(
+      final IbftSignedMessageData<? extends AbstractIbftUnsignedInRoundMessageData> msg,
+      final String msgType) {
+
+    if (!msg.getUnsignedMessageData().getRoundIdentifier().equals(roundIdentifier)) {
+      LOG.info("Invalid {} message, does not match current round.", msgType);
+      return false;
+    }
+
+    if (!validators.contains(msg.getSender())) {
+      LOG.info(
+          "Invalid {} message, was not transmitted by a validator for the " + "associated round.",
+          msgType);
+      return false;
+    }
+
+    if (!preprepareMessage.isPresent()) {
+      LOG.info(
+          "Unable to validate {} message. No Preprepare message exists against "
+              + "which to validate block digest.",
+          msgType);
+      return false;
+    }
+    return true;
+  }
+
+  private boolean validateDigestMatchesPreprepareBlock(final Hash digest, final String msgType) {
+    final Block proposedBlock = preprepareMessage.get().getUnsignedMessageData().getBlock();
+    if (!digest.equals(proposedBlock.getHash())) {
+      LOG.info(
+          "Illegal {} message, digest does not match the block in the Prepare Message.", msgType);
+      return false;
+    }
+    return true;
+  }
+
+  private boolean preprepareMessagesAreIdentical(
+      final IbftUnsignedPrePrepareMessageData right, final IbftUnsignedPrePrepareMessageData left) {
+    return right.getBlock().getHash().equals(left.getBlock().getHash())
+        && (right.getRoundIdentifier().compareTo(left.getRoundIdentifier()) == 0);
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/validation/MessageValidatorTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/validation/MessageValidatorTest.java
@ -0,0 +1,274 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.validation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import tech.pegasys.pantheon.consensus.ibft.ConsensusRoundIdentifier;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftMessageFactory;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftSignedMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedCommitMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedPrePrepareMessageData;
+import tech.pegasys.pantheon.consensus.ibft.ibftmessagedata.IbftUnsignedPrepareMessageData;
+import tech.pegasys.pantheon.crypto.SECP256K1;
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.chain.MutableBlockchain;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.Block;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.ethereum.db.WorldStateArchive;
+import tech.pegasys.pantheon.ethereum.mainnet.BlockHeaderValidator;
+
+import java.util.List;
+
+import com.google.common.collect.Lists;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class MessageValidatorTest {
+
+  private final KeyPair proposerKey = KeyPair.generate();
+  private final KeyPair validatorKey = KeyPair.generate();
+  private final KeyPair nonValidatorKey = KeyPair.generate();
+  private final IbftMessageFactory proposerMessageFactory = new IbftMessageFactory(proposerKey);
+  private final IbftMessageFactory validatorMessageFactory = new IbftMessageFactory(validatorKey);
+  private final IbftMessageFactory nonValidatorMessageFactory =
+      new IbftMessageFactory(nonValidatorKey);
+
+  private List<Address> validators = Lists.newArrayList();
+
+  @Mock private BlockHeaderValidator<IbftContext> headerValidator;
+  private BlockHeader parentHeader = mock(BlockHeader.class);
+  private final ConsensusRoundIdentifier roundIdentifier = new ConsensusRoundIdentifier(2, 0);
+  private MessageValidator validator;
+
+  private final Block block = mock(Block.class);
+
+  @Before
+  public void setup() {
+    validators.add(Util.publicKeyToAddress(proposerKey.getPublicKey()));
+    validators.add(Util.publicKeyToAddress(validatorKey.getPublicKey()));
+
+    final ProtocolContext<IbftContext> protocolContext =
+        new ProtocolContext<>(
+            mock(MutableBlockchain.class), mock(WorldStateArchive.class), mock(IbftContext.class));
+
+    validator =
+        new MessageValidator(
+            validators,
+            Util.publicKeyToAddress(proposerKey.getPublicKey()),
+            roundIdentifier,
+            headerValidator,
+            protocolContext,
+            parentHeader);
+
+    when(block.getHash()).thenReturn(Hash.fromHexStringLenient("1"));
+  }
+
+  @Test
+  public void receivingAPrepareMessageBeforePrePrepareFails() {
+    final IbftSignedMessageData<IbftUnsignedPrepareMessageData> prepareMsg =
+        proposerMessageFactory.createIbftSignedPrepareMessageData(roundIdentifier, Hash.ZERO);
+
+    assertThat(validator.validatePrepareMessage(prepareMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingACommitMessageBeforePreprepareFails() {
+    final IbftSignedMessageData<IbftUnsignedCommitMessageData> commitMsg =
+        proposerMessageFactory.createIbftSignedCommitMessageData(
+            roundIdentifier, Hash.ZERO, SECP256K1.sign(Hash.ZERO, proposerKey));
+
+    assertThat(validator.validateCommmitMessage(commitMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingPreprepareMessageFromNonProposerFails() {
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        validatorMessageFactory.createIbftSignedPrePrepareMessageData(
+            roundIdentifier, mock(Block.class));
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingPreprepareMessageWithIllegalBlockFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(false);
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(
+            roundIdentifier, mock(Block.class));
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingPrepareFromProposerFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+
+    final IbftSignedMessageData<IbftUnsignedPrepareMessageData> prepareMsg =
+        proposerMessageFactory.createIbftSignedPrepareMessageData(roundIdentifier, block.getHash());
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validatePrepareMessage(prepareMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingPrepareFromNonValidatorFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+    final Block block = mock(Block.class);
+    final BlockHeader header = mock(BlockHeader.class);
+    when(header.getHash()).thenReturn(Hash.fromHexStringLenient("1")); // arbitrary hash value.
+    when(block.getHeader()).thenReturn(header);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+
+    final IbftSignedMessageData<IbftUnsignedPrepareMessageData> prepareMsg =
+        nonValidatorMessageFactory.createIbftSignedPrepareMessageData(
+            roundIdentifier, header.getHash());
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validatePrepareMessage(prepareMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingMessagesWithDifferentRoundIdFromPreprepareFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+
+    final ConsensusRoundIdentifier invalidRoundIdentifier =
+        new ConsensusRoundIdentifier(
+            roundIdentifier.getSequenceNumber(), roundIdentifier.getRoundNumber() + 1);
+    final IbftSignedMessageData<IbftUnsignedPrepareMessageData> prepareMsg =
+        validatorMessageFactory.createIbftSignedPrepareMessageData(
+            invalidRoundIdentifier, block.getHash());
+    final IbftSignedMessageData<IbftUnsignedCommitMessageData> commitMsg =
+        validatorMessageFactory.createIbftSignedCommitMessageData(
+            invalidRoundIdentifier, block.getHash(), SECP256K1.sign(block.getHash(), proposerKey));
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validatePrepareMessage(prepareMsg)).isFalse();
+    assertThat(validator.validateCommmitMessage(commitMsg)).isFalse();
+  }
+
+  @Test
+  public void receivingPrepareNonProposerValidatorWithCorrectRoundIsSuccessful() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+    final Block block = mock(Block.class);
+    final BlockHeader header = mock(BlockHeader.class);
+    final Hash blockHash = Hash.fromHexStringLenient("1");
+    when(header.getHash()).thenReturn(blockHash); // arbitrary hash value.
+    when(block.getHeader()).thenReturn(header);
+    when(block.getHash()).thenReturn(blockHash);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    final IbftSignedMessageData<IbftUnsignedPrepareMessageData> prepareMsg =
+        validatorMessageFactory.createIbftSignedPrepareMessageData(
+            roundIdentifier, header.getHash());
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validatePrepareMessage(prepareMsg)).isTrue();
+  }
+
+  @Test
+  public void receivingACommitMessageWithAnInvalidCommitSealFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+
+    final IbftSignedMessageData<IbftUnsignedCommitMessageData> commitMsg =
+        proposerMessageFactory.createIbftSignedCommitMessageData(
+            roundIdentifier, block.getHash(), SECP256K1.sign(block.getHash(), nonValidatorKey));
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validateCommmitMessage(commitMsg)).isFalse();
+  }
+
+  @Test
+  public void commitMessageContainingValidSealFromValidatorIsSuccessful() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+
+    final IbftSignedMessageData<IbftUnsignedCommitMessageData> proposerCommitMsg =
+        proposerMessageFactory.createIbftSignedCommitMessageData(
+            roundIdentifier, block.getHash(), SECP256K1.sign(block.getHash(), proposerKey));
+
+    final IbftSignedMessageData<IbftUnsignedCommitMessageData> validatorCommitMsg =
+        validatorMessageFactory.createIbftSignedCommitMessageData(
+            roundIdentifier, block.getHash(), SECP256K1.sign(block.getHash(), validatorKey));
+
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+    assertThat(validator.validateCommmitMessage(proposerCommitMsg)).isTrue();
+    assertThat(validator.validateCommmitMessage(validatorCommitMsg)).isTrue();
+  }
+
+  @Test
+  public void subsequentPreprepareHasDifferentSenderFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> secondPreprepareMsg =
+        validatorMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(secondPreprepareMsg)).isFalse();
+  }
+
+  @Test
+  public void subsequentPreprepareHasDifferentContentFails() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+
+    final ConsensusRoundIdentifier newRoundIdentifier = new ConsensusRoundIdentifier(3, 0);
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> secondPreprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(newRoundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(secondPreprepareMsg)).isFalse();
+  }
+
+  @Test
+  public void subsequentPreprepareHasIdenticalSenderAndContentIsSuccessful() {
+    when(headerValidator.validateHeader(any(), any(), any(), any())).thenReturn(true);
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> preprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(preprepareMsg)).isTrue();
+
+    final IbftSignedMessageData<IbftUnsignedPrePrepareMessageData> secondPreprepareMsg =
+        proposerMessageFactory.createIbftSignedPrePrepareMessageData(roundIdentifier, block);
+    assertThat(validator.addPreprepareMessage(secondPreprepareMsg)).isTrue();
+  }
+}