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Bloom filtering: check for malformed Merkle trees. Resolves issue 593. Thanks to Pieter Wiulle.

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This commit is contained in:
Mike Hearn 2014-11-24 13:59:42 +01:00
parent dfc9d3c924
commit bd986f35f1
2 changed files with 32 additions and 9 deletions
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20
core/src/main/java/org/bitcoinj/core/PartialMerkleTree.java
View File

@ -185,14 +185,14 @@ public class PartialMerkleTree extends Message {
private Sha256Hash recursiveExtractHashes(int height, int pos, ValuesUsed used, List<Sha256Hash> matchedHashes) throws VerificationException {
if (used.bitsUsed >= matchedChildBits.length*8) {
// overflowed the bits array - failure
throw new VerificationException("CPartialMerkleTree overflowed its bits array");
throw new VerificationException("PartialMerkleTree overflowed its bits array");
}
boolean parentOfMatch = checkBitLE(matchedChildBits, used.bitsUsed++);
if (height == 0 || !parentOfMatch) {
// if at height 0, or nothing interesting below, use stored hash and do not descend
if (used.hashesUsed >= hashes.size()) {
// overflowed the hash array - failure
throw new VerificationException("CPartialMerkleTree overflowed its hash array");
throw new VerificationException("PartialMerkleTree overflowed its hash array");
}
Sha256Hash hash = hashes.get(used.hashesUsed++);
if (height == 0 && parentOfMatch) // in case of height 0, we have a matched txid
@ -201,10 +201,13 @@ public class PartialMerkleTree extends Message {
} else {
// otherwise, descend into the subtrees to extract matched txids and hashes
byte[] left = recursiveExtractHashes(height - 1, pos * 2, used, matchedHashes).getBytes(), right;
if (pos * 2 + 1 < getTreeWidth(transactionCount, height-1))
if (pos * 2 + 1 < getTreeWidth(transactionCount, height-1)) {
right = recursiveExtractHashes(height - 1, pos * 2 + 1, used, matchedHashes).getBytes();
else
if (Arrays.equals(right, left))
throw new VerificationException("Invalid merkle tree with duplicated left/right branches");
} else {
right = left;
}
// and combine them before returning
return combineLeftRight(left, right);
}
@ -223,13 +226,12 @@ public class PartialMerkleTree extends Message {
* The returned root should be checked against the
* merkle root contained in the block header for security.
*
* @param matchedHashes A list which will contain the matched txn (will be cleared)
* Required to be a LinkedHashSet in order to retain order or transactions in the block
* @param matchedHashesOut A list which will contain the matched txn (will be cleared).
* @return the merkle root of this merkle tree
* @throws ProtocolException if this partial merkle tree is invalid
*/
public Sha256Hash getTxnHashAndMerkleRoot(List<Sha256Hash> matchedHashes) throws VerificationException {
matchedHashes.clear();
public Sha256Hash getTxnHashAndMerkleRoot(List<Sha256Hash> matchedHashesOut) throws VerificationException {
matchedHashesOut.clear();
// An empty set will not work
if (transactionCount == 0)
@ -249,7 +251,7 @@ public class PartialMerkleTree extends Message {
height++;
// traverse the partial tree
ValuesUsed used = new ValuesUsed();
Sha256Hash merkleRoot = recursiveExtractHashes(height, 0, used, matchedHashes);
Sha256Hash merkleRoot = recursiveExtractHashes(height, 0, used, matchedHashesOut);
// verify that all bits were consumed (except for the padding caused by serializing it as a byte sequence)
if ((used.bitsUsed+7)/8 != matchedChildBits.length ||
// verify that all hashes were consumed

21
core/src/test/java/org/bitcoinj/core/FilteredBlockAndPartialMerkleTreeTests.java
View File

@ -17,6 +17,7 @@
package org.bitcoinj.core;
import com.google.common.collect.Lists;
import org.bitcoinj.core.TransactionConfidence.ConfidenceType;
import org.bitcoinj.params.UnitTestParams;
import org.bitcoinj.store.MemoryBlockStore;
@ -88,6 +89,26 @@ public class FilteredBlockAndPartialMerkleTreeTests extends TestWithPeerGroup {
assertTrue(txns.contains(tx2.getHash()));
}
private Sha256Hash numAsHash(int num) {
byte[] bits = new byte[32];
bits[0] = (byte) num;
return new Sha256Hash(bits);
}
@Test(expected = VerificationException.class)
public void merkleTreeMalleability() throws Exception {
List<Sha256Hash> hashes = Lists.newArrayList();
for (byte i = 1; i <= 10; i++) hashes.add(numAsHash(i));
hashes.add(numAsHash(9));
hashes.add(numAsHash(10));
byte[] includeBits = new byte[2];
Utils.setBitLE(includeBits, 9);
Utils.setBitLE(includeBits, 10);
PartialMerkleTree pmt = PartialMerkleTree.buildFromLeaves(params, includeBits, hashes);
List<Sha256Hash> matchedHashes = Lists.newArrayList();
pmt.getTxnHashAndMerkleRoot(matchedHashes);
}
@Test
public void serializeDownloadBlockWithWallet() throws Exception {
unitTestParams = UnitTestParams.get();