Add unit tests for AuxPoW header validation.

src/main/java/org/bitcoinj/core/AuxPoW.java

@@ -313,12 +313,11 @@ public class AuxPoW extends ChildMessage implements Serializable {
             return false;
         }
 
-        // Check that the chain merkle root is in the coinbase
         Sha256Hash nRootHash = getChainMerkleBranch().calculateMerkleRoot(hashAuxBlock);
         final byte[] vchRootHash = nRootHash.getBytes();
-        //std::reverse(vchRootHash.begin(), vchRootHash.end()); // correct endian// correct endian
 
-        // Check that we are in the parent block merkle tree
+        // Check that the coinbase transaction is in the merkle tree of the
+        // parent block header
         if (!getCoinbaseBranch().calculateMerkleRoot(getCoinbase().getHash()).equals(parentBlockHeader.getMerkleRoot())) {
             if (throwException) {
                 throw new VerificationException("Aux POW merkle root incorrect");
@@ -326,31 +325,35 @@ public class AuxPoW extends ChildMessage implements Serializable {
             return false;
         }
 
+        if (this.getCoinbase().getInputs().isEmpty()) {
+            throw new VerificationException("Coinbase transaction has no inputs");
+        }
+
+        // Check that the chain merkle root is in the coinbase
         final byte[] script = this.getCoinbase().getInput(0).getScriptBytes();
 
-        // Check that the same work is not submitted twice to our chain.
-        //
-        int pcHead = -1;
+        // Check that the same work is not submitted twice to our chain, by
+        // confirming that the child block hash is in the coinbase merkle tree
+        int pcHeader = -1;
         int pc = -1;
 
         for (int scriptIdx = 0; scriptIdx < script.length; scriptIdx++) {
             if (arrayMatch(script, scriptIdx, MERGED_MINING_HEADER)) {
                 // Enforce only one chain merkle root by checking that a single instance of the merged
                 // mining header exists just before.
-                if (pcHead >= 0) {
+                if (pcHeader >= 0) {
                     if (throwException) {
                         throw new VerificationException("Multiple merged mining headers in coinbase");
                     }
                     return false;
                 }
-                pcHead = scriptIdx;
-            }
-            if (arrayMatch(script, scriptIdx, vchRootHash)) {
+                pcHeader = scriptIdx;
+            } else if (arrayMatch(script, scriptIdx, vchRootHash)) {
                 pc = scriptIdx;
             }
         }
 
-        if (-1 == pcHead) {
+        if (-1 == pcHeader) {
             if (throwException) {
                 throw new VerificationException("MergedMiningHeader missing from parent coinbase");
             }
@@ -364,7 +367,7 @@ public class AuxPoW extends ChildMessage implements Serializable {
             return false;
         }
 
-        if (pcHead + MERGED_MINING_HEADER.length != pc) {
+        if (pcHeader + MERGED_MINING_HEADER.length != pc) {
             if (throwException) {
                 throw new VerificationException("Merged mining header is not just before chain merkle root");
             }
@@ -449,7 +452,22 @@ public class AuxPoW extends ChildMessage implements Serializable {
     /**
      * Get the chain ID from a block header.
      */
-    protected long getChainID(final Block blockHeader) {
+    public static long getChainID(final Block blockHeader) {
         return blockHeader.getVersion() / AltcoinBlock.BLOCK_VERSION_CHAIN_START;
     }
+
+    /**
+     * Set the merkle branch used to connect the coinbase transaction to the
+     * parent block header.
+     */
+    public void setCoinbaseBranch(final MerkleBranch merkleBranch) {
+        this.coinbaseBranch = merkleBranch;
+    }
+
+    /**
+     * Set the parent chain block header.
+     */
+    public void setParentBlockHeader(final AltcoinBlock header) {
+        this.parentBlockHeader = header;
+    }
 }

src/main/java/org/bitcoinj/core/MerkleBranch.java

@@ -48,15 +48,15 @@ public class MerkleBranch extends ChildMessage implements Serializable {
     // can properly keep track of optimal encoded size
     private transient int optimalEncodingMessageSize;
 
-    private List<Sha256Hash> branchHashes;
+    private List<Sha256Hash> hashes;
     private long index;
 
     public MerkleBranch(NetworkParameters params, @Nullable ChildMessage parent) {
         super(params);
         setParent(parent);
 
-		this.branchHashes = new ArrayList<Sha256Hash>();
-		this.index = 0;
+        this.hashes = new ArrayList<Sha256Hash>();
+        this.index = 0;
     }
 
     /**
@@ -86,7 +86,7 @@ public class MerkleBranch extends ChildMessage implements Serializable {
         super(params);
         setParent(parent);
 
-        this.branchHashes = hashes;
+        this.hashes = hashes;
         this.index = branchSideMask;
     }
 
@@ -111,19 +111,19 @@ public class MerkleBranch extends ChildMessage implements Serializable {
 
         final int hashCount = (int) readVarInt();
         optimalEncodingMessageSize += VarInt.sizeOf(hashCount);
-        branchHashes = new ArrayList<Sha256Hash>(hashCount);
+        hashes = new ArrayList<Sha256Hash>(hashCount);
         for (int hashIdx = 0; hashIdx < hashCount; hashIdx++) {
-                branchHashes.add(readHash());
+            hashes.add(readHash());
         }
         optimalEncodingMessageSize += 32 * hashCount;
-		index = readUint32();
+        setIndex(readUint32());
         optimalEncodingMessageSize += 4;
     }
 
     @Override
     protected void bitcoinSerializeToStream(OutputStream stream) throws IOException {
-        stream.write(new VarInt(branchHashes.size()).encode());
-        for (Sha256Hash hash: branchHashes) {
+        stream.write(new VarInt(hashes.size()).encode());
+        for (Sha256Hash hash: hashes) {
                 stream.write(Utils.reverseBytes(hash.getBytes()));
         }
         Utils.uint32ToByteStreamLE(index, stream);
@@ -137,7 +137,7 @@ public class MerkleBranch extends ChildMessage implements Serializable {
         byte[] target = reverseBytes(leaf.getBytes());
         long mask = index;
 
-        for (Sha256Hash hash: branchHashes) {
+        for (Sha256Hash hash: hashes) {
             target = (mask & 1) == 0
                 ? doubleDigestTwoBuffers(target, 0, 32, reverseBytes(hash.getBytes()), 0, 32)
                 : doubleDigestTwoBuffers(reverseBytes(hash.getBytes()), 0, 32, target, 0, 32);
@@ -150,7 +150,7 @@ public class MerkleBranch extends ChildMessage implements Serializable {
      * Get the hashes which make up this branch.
      */
     public List<Sha256Hash> getHashes() {
-        return Collections.unmodifiableList(this.branchHashes);
+        return Collections.unmodifiableList(this.hashes);
     }
 
     /**
@@ -162,11 +162,26 @@ public class MerkleBranch extends ChildMessage implements Serializable {
         return index;
     }
 
+    /**
+     * @param hashes the hashes to set
+     */
+    public void setHashes(List<Sha256Hash> hashes) {
+        this.hashes = hashes;
+    }
+
+    /**
+     * Set the mask used to determine the sides in which hashes are applied.
+     */
+    public void setIndex(final long newIndex) {
+        assert newIndex >= 0;
+        this.index = newIndex;
+    }
+
     /**
      * Get the number of hashes in this branch.
      */
     public int size() {
-        return branchHashes.size();
+        return hashes.size();
     }
 
     public int getOptimalEncodingMessageSize() {
@@ -214,7 +229,7 @@ public class MerkleBranch extends ChildMessage implements Serializable {
 
         MerkleBranch input = (MerkleBranch) o;
 
-        if (!branchHashes.equals(input.branchHashes)) return false;
+        if (!hashes.equals(input.hashes)) return false;
         if (index != input.index) return false;
 
         return true;
@@ -223,7 +238,7 @@ public class MerkleBranch extends ChildMessage implements Serializable {
     @Override
     public int hashCode() {
         int result = 1;
-        result = 31 * result + branchHashes.hashCode();
+        result = 31 * result + hashes.hashCode();
         result = 31 * result + (int) index;
         return result;
     }

src/test/java/org/bitcoinj/core/AuxPoWTest.java

@@ -1,19 +1,32 @@
 package org.bitcoinj.core;
 
-import java.math.BigInteger;
-import org.altcoinj.params.DogecoinTestNet3Params;
+import java.util.Arrays;
+import java.util.Collections;
+import org.altcoinj.core.AltcoinSerializer;
+import org.altcoinj.params.DogecoinMainNetParams;
 import org.junit.Test;
 
 import static org.bitcoinj.core.Util.getBytes;
+import static org.bitcoinj.core.Utils.doubleDigestTwoBuffers;
+import static org.bitcoinj.core.Utils.reverseBytes;
 
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.rules.ExpectedException;
 
 /**
  * AuxPoW header parsing/serialization and validation
  */
 public class AuxPoWTest {
-    static final NetworkParameters params = DogecoinTestNet3Params.get();
+    static final NetworkParameters params = DogecoinMainNetParams.get();
+    private static final int MERKLE_ROOT_COINBASE_INDEX = 0;
+
+    @Before
+    public void setUp() throws Exception {
+        Context context = new Context(params);
+    }
 
     /**
      * Parse the AuxPoW header from Dogecoin block #403,931.
@@ -56,4 +69,290 @@ public class AuxPoWTest {
         auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
             Utils.decodeCompactBits(0x1b06f8f0), true);
     }
+    
+    @Rule
+    public ExpectedException expectedEx = ExpectedException.none();
+
+    /**
+     * Check that a non-generate AuxPoW transaction is rejected.
+     */
+    @Test
+    public void shouldRejectNonGenerateAuxPoW() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+        auxpow.getCoinbaseBranch().setIndex(0x01);
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("AuxPow is not a generate");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Check that block headers from the child chain are rejected as parent
+     * chain for AuxPoW, via checking of the chain IDs.
+     */
+    @Test
+    public void shouldRejectOwnChainID() throws Exception {
+        byte[] payload = Util.getBytes(getClass().getResourceAsStream("dogecoin_block371337.bin"));
+        AltcoinSerializer serializer = (AltcoinSerializer)params.getDefaultSerializer();
+        final AltcoinBlock block = (AltcoinBlock)serializer.makeBlock(payload);
+        final AuxPoW auxpow = block.getAuxPoW();
+        auxpow.setParentBlockHeader((AltcoinBlock)block.cloneAsHeader());
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW parent has our chain ID");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Check that where the merkle branch is far too long to use, it's rejected.
+     */
+    @Test
+    public void shouldRejectVeryLongMerkleBranch() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+        auxpow.getChainMerkleBranch().setHashes(Arrays.asList(new Sha256Hash[32]));
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW chain merkle branch too long");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Later steps in AuxPoW validation depend on the contents of the coinbase
+     * transaction. Obviously that's useless if we don't check the coinbase
+     * transaction is actually part of the parent chain block, so first we test
+     * that the transaction hash is part of the merkle tree. This test modifies
+     * the transaction, invalidating the hash, to confirm that it's rejected.
+     */
+    @Test
+    public void shouldRejectIfCoinbaseTransactionNotInMerkleBranch() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+        auxpow.getCoinbase().clearOutputs();
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW merkle root incorrect");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Ensure that in case of a malformed coinbase transaction (no inputs) it's
+     * caught and processed neatly.
+     */
+    @Test
+    public void shouldRejectIfCoinbaseTransactionHasNoInputs() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        auxpow.getCoinbase().clearInputs();
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Coinbase transaction has no inputs");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that the merged mine header is missing from the coinbase
+     * transaction.
+     */
+    @Test
+    public void shouldRejectIfMergedMineHeaderMissing() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        in.getScriptBytes()[4] = 0; // Break the first byte of the header
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("MergedMiningHeader missing from parent coinbase");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that more than one merged mine header is present in the 
+     * coinbase transaction (this is considered an attempt to confuse the parser).
+     */
+    @Test
+    public void shouldRejectIfMergedMineHeaderDuplicated() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        final byte[] newBytes = Arrays.copyOf(in.getScriptBytes(), in.getScriptBytes().length + 4);
+        for (int byteIdx = 0; byteIdx < AuxPoW.MERGED_MINING_HEADER.length; byteIdx++) {
+            newBytes[newBytes.length - 4 + byteIdx] = AuxPoW.MERGED_MINING_HEADER[byteIdx];
+        }
+        in.setScriptBytes(newBytes);
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Multiple merged mining headers in coinbase");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that the chain merkle branch is missing from the coinbase
+     * transaction. The chain merkle branch is used to prove that the block was
+     * mined for chain or chains including this one (i.e. random proof of work
+     * cannot be taken from any merged-mined blockchain and reused).
+     */
+    @Test
+    public void shouldRejectIfCoinbaseMissingChainMerkleRoot() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        in.getScriptBytes()[8] = 0; // Break the first byte of the chain merkle root
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW missing chain merkle root in parent coinbase");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that the chain merkle branch is not immediately after the
+     * merged mine header in the coinbase transaction (this is considered an
+     * attempt to confuse the parser).
+     */
+    @Test
+    public void shouldRejectIfChainMerkleRootNotAfterHeader() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        final byte[] newBytes = Arrays.copyOf(in.getScriptBytes(), in.getScriptBytes().length + 1);
+        // Copy every byte after the merged-mine header forward one byte. We
+        // have to do this from the end of the array backwards to avoid overwriting
+        // the next byte to copy.
+        for (int byteIdx = newBytes.length - 1; byteIdx > 8; byteIdx--) {
+            newBytes[byteIdx] = newBytes[byteIdx - 1];
+        }
+        newBytes[8] = (byte) 0xff;
+        in.setScriptBytes(newBytes);
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Merged mining header is not just before chain merkle root");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that the chain merkle branch is not immediately after the
+     * merged mine header in the coinbase transaction (this is considered an
+     * attempt to confuse the parser).
+     */
+    @Test
+    public void shouldRejectIfScriptBytesTooShort() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        final byte[] newBytes = Arrays.copyOf(in.getScriptBytes(), in.getScriptBytes().length - 12);
+        in.setScriptBytes(newBytes);
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW missing chain merkle tree size and nonce in parent coinbase");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Catch the case that the chain merkle branch size in the coinbase transaction
+     * does not match the size of the merkle brach in the AuxPoW header.
+     */
+    @Test
+    public void shouldRejectIfCoinbaseMerkleBranchSizeMismatch() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        in.getScriptBytes()[40] = 3; // Break the merkle branch length
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW merkle branch size does not match parent coinbase");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * In order to ensure that the same work is not submitted more than once,
+     * confirm that the merkle branch index is correct for our chain ID.
+     */
+    @Test
+    public void shouldRejectIfNonceIncorrect() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        // This will also break the difficulty check, but as that doesn't occur
+        // until the end, we can get away with it.
+        final TransactionInput in = auxpow.getCoinbase().getInput(0);
+        in.getScriptBytes()[44] = (byte) 0xff; // Break the nonce value
+        updateMerkleRootToMatchCoinbase(auxpow);
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Aux POW wrong index");
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x1b06f8f0), true);
+    }
+
+    /**
+     * Having validated the AuxPoW header, the last check is that the block hash
+     * meets the target difficulty.
+     */
+    @Test
+    public void shouldRejectHashAboveTarget() throws Exception {
+        final byte[] auxpowAsBytes = getBytes(getClass().getResourceAsStream("auxpow_header.bin"));
+        final AuxPoW auxpow = new AuxPoW(params, auxpowAsBytes, (ChildMessage) null, params.getDefaultSerializer());
+
+        expectedEx.expect(org.bitcoinj.core.VerificationException.class);
+        expectedEx.expectMessage("Hash is higher than target: a22a9b01671d639fa6389f62ecf8ce69204c8ed41d5f1a745e0c5ba7116d5b4c vs 0");
+        
+        auxpow.checkProofOfWork(new Sha256Hash("0c836b86991631d34a8a68054e2f62db919b39d1ee43c27ab3344d6aa82fa609"),
+            Utils.decodeCompactBits(0x00), true);
+    }
+
+    /**
+     * Fix up the merkle root of the parent block header to match the
+     * coinbase transaction.
+     */
+    private void updateMerkleRootToMatchCoinbase(final AuxPoW auxpow) {
+        final Transaction coinbase = auxpow.getCoinbase();
+
+        final Sha256Hash revisedCoinbaseHash = coinbase.getHash();
+        // The coinbase hash is the single leaf node in the merkle tree,
+        // so to get the root we need to hash it with itself.
+        // Note that bytes are reversed for hashing
+        final byte[] revisedMerkleRootBytes = doubleDigestTwoBuffers(
+                reverseBytes(revisedCoinbaseHash.getBytes()), 0, 32,
+                reverseBytes(revisedCoinbaseHash.getBytes()), 0, 32);
+        final Sha256Hash revisedMerkleRoot = new Sha256Hash(reverseBytes(revisedMerkleRootBytes));
+        auxpow.getParentBlockHeader().setMerkleRoot(revisedMerkleRoot);
+        auxpow.setCoinbaseBranch(new MerkleBranch(params, auxpow,
+                Collections.singletonList(revisedCoinbaseHash), MERKLE_ROOT_COINBASE_INDEX));
+    }
 }