From 6625c9a2cbb0c9bdf8b4d231cacb38c451dfdd5e Mon Sep 17 00:00:00 2001 From: Mike Hearn Date: Tue, 8 Oct 2013 11:49:53 +0200 Subject: [PATCH] Use earliest key time minus a week for setting fast catchup time and selecting a checkpoint. This handles clock drift both in the block headers and possibly wrong times in the users clock (broken timezone, etc). Resolves issue 460. --- .../bitcoin/core/CheckpointManager.java | 60 ++++++++++++------- .../com/google/bitcoin/core/PeerGroup.java | 11 +++- .../google/bitcoin/core/PeerGroupTest.java | 18 +++--- 3 files changed, 56 insertions(+), 33 deletions(-) diff --git a/core/src/main/java/com/google/bitcoin/core/CheckpointManager.java b/core/src/main/java/com/google/bitcoin/core/CheckpointManager.java index 91d5b626..c5369332 100644 --- a/core/src/main/java/com/google/bitcoin/core/CheckpointManager.java +++ b/core/src/main/java/com/google/bitcoin/core/CheckpointManager.java @@ -22,7 +22,10 @@ import com.google.bitcoin.store.FullPrunedBlockStore; import org.slf4j.Logger; import org.slf4j.LoggerFactory; -import java.io.*; +import java.io.BufferedInputStream; +import java.io.DataInputStream; +import java.io.IOException; +import java.io.InputStream; import java.nio.ByteBuffer; import java.security.DigestInputStream; import java.security.MessageDigest; @@ -34,22 +37,33 @@ import java.util.TreeMap; import static com.google.common.base.Preconditions.*; /** - *

Vends hard-coded {@link StoredBlock}s for blocks throughout the chain. Checkpoints serve several purposes:

+ *

Vends hard-coded {@link StoredBlock}s for blocks throughout the chain. Checkpoints serve two purposes:

*
    *
  1. They act as a safety mechanism against huge re-orgs that could rewrite large chunks of history, thus * constraining the block chain to be a consensus mechanism only for recent parts of the timeline.
    2. *
  2. They allow synchronization to the head of the chain for new wallets/users much faster than syncing all * headers from the genesis block.
    3. - *
  3. They mark each BIP30-violating block, which simplifies full verification logic quite significantly. BIP30 - * handles the case of blocks that contained duplicated coinbase transactions.
    4. *
* - *

Checkpoints are used by a {@link BlockChain} to initialize fresh {@link com.google.bitcoin.store.SPVBlockStore}s, - * and by {@link FullPrunedBlockChain} to prevent re-orgs beyond them.

+ *

Checkpoints are used by the SPV {@link BlockChain} to initialize fresh + * {@link com.google.bitcoin.store.SPVBlockStore}s. They are not used by fully validating mode, which instead has a + * different concept of checkpoints that are used to hard-code the validity of blocks that violate BIP30 (duplicate + * coinbase transactions). Those "checkpoints" can be found in NetworkParameters.

+ * + *

The file format consists of the string "CHECKPOINTS 1", followed by a uint32 containing the number of signatures + * to read. The value may not be larger than 256 (so it could have been a byte but isn't for historical reasons). + * If the number of signatures is larger than zero, each 65 byte ECDSA secp256k1 signature then follows. The signatures + * sign the hash of all bytes that follow the last signature.

+ * + *

After the signatures come an int32 containing the number of checkpoints in the file. Then each checkpoint follows + * one after the other. A checkpoint is 12 bytes for the total work done field, 4 bytes for the height, 80 bytes + * for the block header and then 1 zero byte at the end (i.e. number of transactions in the block: always zero).

*/ public class CheckpointManager { private static final Logger log = LoggerFactory.getLogger(CheckpointManager.class); + private static final int MAX_SIGNATURES = 256; + // Map of block header time to data. protected final TreeMap checkpoints = new TreeMap(); @@ -58,10 +72,11 @@ public class CheckpointManager { public CheckpointManager(NetworkParameters params, InputStream inputStream) throws IOException { this.params = checkNotNull(params); + checkNotNull(inputStream); DataInputStream dis = null; try { MessageDigest digest = MessageDigest.getInstance("SHA-256"); - DigestInputStream digestInputStream = new DigestInputStream(checkNotNull(inputStream), digest); + DigestInputStream digestInputStream = new DigestInputStream(inputStream, digest); dis = new DataInputStream(digestInputStream); digestInputStream.on(false); String magic = "CHECKPOINTS 1"; @@ -69,7 +84,7 @@ public class CheckpointManager { dis.readFully(header); if (!Arrays.equals(header, magic.getBytes("US-ASCII"))) throw new IOException("Header bytes did not match expected version"); - int numSignatures = dis.readInt(); + int numSignatures = checkPositionIndex(dis.readInt(), MAX_SIGNATURES, "Num signatures out of range"); for (int i = 0; i < numSignatures; i++) { byte[] sig = new byte[65]; dis.readFully(sig); @@ -104,18 +119,16 @@ public class CheckpointManager { * you would want to know the checkpoint before the earliest wallet birthday. */ public StoredBlock getCheckpointBefore(long time) { - checkArgument(time > params.getGenesisBlock().getTimeSeconds()); - // This is thread safe because the map never changes after creation. - Map.Entry entry = checkpoints.floorEntry(time); - if (entry == null) { - try { - Block genesis = params.getGenesisBlock().cloneAsHeader(); - return new StoredBlock(genesis, genesis.getWork(), 0); - } catch (VerificationException e) { - throw new RuntimeException(e); // Cannot happen. - } + try { + checkArgument(time > params.getGenesisBlock().getTimeSeconds()); + // This is thread safe because the map never changes after creation. + Map.Entry entry = checkpoints.floorEntry(time); + if (entry != null) return entry.getValue(); + Block genesis = params.getGenesisBlock().cloneAsHeader(); + return new StoredBlock(genesis, genesis.getWork(), 0); + } catch (VerificationException e) { + throw new RuntimeException(e); // Cannot happen. } - return entry.getValue(); } /** Returns the number of checkpoints that were loaded. */ @@ -129,15 +142,20 @@ public class CheckpointManager { } /** - * Convenience method that creates a CheckpointManager, loads the given data, gets the checkpoint for the given + *

Convenience method that creates a CheckpointManager, loads the given data, gets the checkpoint for the given * time, then inserts it into the store and sets that to be the chain head. Useful when you have just created - * a new store from scratch and want to use configure it all in one go. + * a new store from scratch and want to use configure it all in one go.

+ * + *

Note that time is adjusted backwards by a week to account for possible clock drift in the block headers.

*/ public static void checkpoint(NetworkParameters params, InputStream checkpoints, BlockStore store, long time) throws IOException, BlockStoreException { checkNotNull(params); checkNotNull(store); checkArgument(!(store instanceof FullPrunedBlockStore), "You cannot use checkpointing with a full store."); + + time -= 86400 * 7; + BufferedInputStream stream = new BufferedInputStream(checkpoints); CheckpointManager manager = new CheckpointManager(params, stream); StoredBlock checkpoint = manager.getCheckpointBefore(time); diff --git a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java index de228ad6..d39afc1a 100644 --- a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java +++ b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java @@ -678,10 +678,10 @@ public class PeerGroup extends AbstractIdleService implements TransactionBroadca // Fully verifying mode doesn't use this optimization (it can't as it needs to see all transactions). if (chain != null && chain.shouldVerifyTransactions()) return; - long earliestKeyTime = Long.MAX_VALUE; + long earliestKeyTimeSecs = Long.MAX_VALUE; int elements = 0; for (PeerFilterProvider p : peerFilterProviders) { - earliestKeyTime = Math.min(earliestKeyTime, p.getEarliestKeyCreationTime()); + earliestKeyTimeSecs = Math.min(earliestKeyTimeSecs, p.getEarliestKeyCreationTime()); elements += p.getBloomFilterElementCount(); } @@ -704,8 +704,13 @@ public class PeerGroup extends AbstractIdleService implements TransactionBroadca } } } + // Now adjust the earliest key time backwards by a week to handle the case of clock drift. This can occur + // both in block header timestamps and if the users clock was out of sync when the key was first created + // (to within a small amount of tolerance). + earliestKeyTimeSecs -= 86400 * 7; + // Do this last so that bloomFilter is already set when it gets called. - setFastCatchupTimeSecs(earliestKeyTime); + setFastCatchupTimeSecs(earliestKeyTimeSecs); } finally { lock.unlock(); } diff --git a/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java b/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java index a6167e6e..d9bd531e 100644 --- a/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java +++ b/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java @@ -28,7 +28,6 @@ import org.junit.Test; import java.math.BigInteger; import java.net.InetSocketAddress; -import java.util.Date; import java.util.HashSet; import java.util.Set; import java.util.concurrent.Semaphore; @@ -336,23 +335,24 @@ public class PeerGroupTest extends TestWithPeerGroup { @Test public void testWalletCatchupTime() throws Exception { - // Check the fast catchup time was initialized to something around the current runtime. The wallet was - // already added to the peer in setup. - long time = new Date().getTime() / 1000; - assertTrue(peerGroup.getFastCatchupTimeSecs() > time - 10000); + // Check the fast catchup time was initialized to something around the current runtime minus a week. + // The wallet was already added to the peer in setup. + final int WEEK = 86400 * 7; + final long now = Utils.now().getTime() / 1000; + assertTrue(peerGroup.getFastCatchupTimeSecs() > now - WEEK - 10000); Wallet w2 = new Wallet(params); ECKey key1 = new ECKey(); - key1.setCreationTimeSeconds(time - 86400); // One day ago. + key1.setCreationTimeSeconds(now - 86400); // One day ago. w2.addKey(key1); peerGroup.addWallet(w2); Threading.waitForUserCode(); - assertEquals(peerGroup.getFastCatchupTimeSecs(), time - 86400); + assertEquals(peerGroup.getFastCatchupTimeSecs(), now - 86400 - WEEK); // Adding a key to the wallet should update the fast catchup time. ECKey key2 = new ECKey(); - key2.setCreationTimeSeconds(time - 100000); + key2.setCreationTimeSeconds(now - 100000); w2.addKey(key2); Threading.waitForUserCode(); - assertEquals(peerGroup.getFastCatchupTimeSecs(), time - 100000); + assertEquals(peerGroup.getFastCatchupTimeSecs(), now - WEEK - 100000); } @Test