org.bitcoinj.core.Block Maven / Gradle / Ivy
/*
* Copyright 2011 Google Inc.
* Copyright 2014 Andreas Schildbach
*
* 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 org.bitcoinj.core;
import com.google.common.annotations.*;
import com.google.common.base.*;
import com.google.common.collect.*;
import org.bitcoinj.script.*;
import org.slf4j.*;
import javax.annotation.*;
import java.io.*;
import java.math.*;
import java.util.*;
import static org.bitcoinj.core.Coin.*;
import static org.bitcoinj.core.Sha256Hash.*;
import static org.bitcoinj.core.Utils.HEX;
/**
* A block is a group of transactions, and is one of the fundamental data structures of the Bitcoin system.
* It records a set of {@link Transaction}s together with some data that links it into a place in the global block
* chain, and proves that a difficult calculation was done over its contents. See
* the Bitcoin technical paper for
* more detail on blocks.
*
* To get a block, you can either build one from the raw bytes you can get from another implementation, or request one
* specifically using {@link Peer#getBlock(Sha256Hash)}, or grab one from a downloaded {@link BlockChain}.
*
* Instances of this class are not safe for use by multiple threads.
*/
public class Block extends Message {
/**
* Flags used to control which elements of block validation are done on
* received blocks.
*/
public enum VerifyFlag {
/** Check that block height is in coinbase transaction (BIP 34). */
HEIGHT_IN_COINBASE,
/** Compute block weight and verify witness commitment structure in coinbase. */
SEGWIT
}
private static final Logger log = LoggerFactory.getLogger(Block.class);
/** How many bytes are required to represent a block header WITHOUT the trailing 00 length byte. */
public static final int HEADER_SIZE = 80;
static final long ALLOWED_TIME_DRIFT = 2 * 60 * 60; // Same value as Bitcoin Core.
/**
* A constant shared by the entire network: how large in bytes a block is allowed to be. One day we may have to
* upgrade everyone to change this, so Bitcoin can continue to grow. For now it exists as an anti-DoS measure to
* avoid somebody creating a titanically huge but valid block and forcing everyone to download/store it forever.
*/
public static final int MAX_BLOCK_SIZE = 1 * 1000 * 1000;
/**
* Segwit blocks have a block weight defined as three times base size (block without witness data) plus total size
* (block including witness data). It must be less than 4 MB.
*/
public static final int MAX_BLOCK_WEIGHT = 4 * 1000 * 1000;
/**
* A "sigop" is a signature verification operation. Because they're expensive we also impose a separate limit on
* the number in a block to prevent somebody mining a huge block that has way more sigops than normal, so is very
* expensive/slow to verify. Segwit makes this four times larger, and makes every operation four times more
* expensive in non-segwit parts of scripts.
*/
public static final int MAX_BLOCK_SIGOPS = MAX_BLOCK_WEIGHT / 50;
/** A value for difficultyTarget (nBits) that allows half of all possible hash solutions. Used in unit testing. */
public static final long EASIEST_DIFFICULTY_TARGET = 0x207fFFFFL;
/** Value to use if the block height is unknown */
public static final int BLOCK_HEIGHT_UNKNOWN = -1;
/** Height of the first block */
public static final int BLOCK_HEIGHT_GENESIS = 0;
public static final long BLOCK_VERSION_GENESIS = 1;
/** Block version introduced in BIP 34: Height in coinbase */
public static final long BLOCK_VERSION_BIP34 = 2;
/** Block version introduced in BIP 66: Strict DER signatures */
public static final long BLOCK_VERSION_BIP66 = 3;
/** Block version introduced in BIP 65: OP_CHECKLOCKTIMEVERIFY */
public static final long BLOCK_VERSION_BIP65 = 4;
/** Segwit pubKeyScript header
* OP_RETURN 36 (push to stack) 0xaa21a9ed { 32 bytes commitment structure }
* */
private static final byte[] SEGWIT_HEADER = HEX.decode("6a24aa21a9ed");
// Fields defined as part of the protocol format.
private long version;
private Sha256Hash prevBlockHash;
private Sha256Hash merkleRoot;
private long time;
private long difficultyTarget; // "nBits"
private long nonce;
// TODO: Get rid of all the direct accesses to this field. It's a long-since unnecessary holdover from the Dalvik days.
/** If null, it means this object holds only the headers. */
@Nullable List transactions;
/** Stores the hash of the block. If null, getHash() will recalculate it. */
private Sha256Hash hash;
protected boolean headerBytesValid;
protected boolean transactionBytesValid;
// Blocks can be encoded in a way that will use more bytes than is optimal (due to VarInts having multiple encodings)
// MAX_BLOCK_SIZE must be compared to the optimal encoding, not the actual encoding, so when parsing, we keep track
// of the size of the ideal encoding in addition to the actual message size (which Message needs)
protected int optimalEncodingMessageSize;
/** Special case constructor, used for the genesis node, cloneAsHeader and unit tests. */
Block(NetworkParameters params, long setVersion) {
super(params);
// Set up a few basic things. We are not complete after this though.
version = setVersion;
difficultyTarget = 0x1d07fff8L;
time = System.currentTimeMillis() / 1000;
prevBlockHash = Sha256Hash.ZERO_HASH;
length = HEADER_SIZE;
}
/**
* Constructs a block object from the Bitcoin wire format.
* @deprecated Use {@link BitcoinSerializer#makeBlock(byte[])} instead.
*/
@Deprecated
public Block(NetworkParameters params, byte[] payloadBytes) throws ProtocolException {
super(params, payloadBytes, 0, params.getDefaultSerializer(), payloadBytes.length);
}
/**
* Construct a block object from the Bitcoin wire format.
* @param params NetworkParameters object.
* @param payloadBytes the payload to extract the block from.
* @param serializer the serializer to use for this message.
* @param length The length of message if known. Usually this is provided when deserializing of the wire
* as the length will be provided as part of the header. If unknown then set to Message.UNKNOWN_LENGTH
* @throws ProtocolException
*/
public Block(NetworkParameters params, byte[] payloadBytes, MessageSerializer serializer, int length)
throws ProtocolException {
super(params, payloadBytes, 0, serializer, length);
}
/**
* Construct a block object from the Bitcoin wire format.
* @param params NetworkParameters object.
* @param payloadBytes the payload to extract the block from.
* @param offset The location of the first payload byte within the array.
* @param serializer the serializer to use for this message.
* @param length The length of message if known. Usually this is provided when deserializing of the wire
* as the length will be provided as part of the header. If unknown then set to Message.UNKNOWN_LENGTH
* @throws ProtocolException
*/
public Block(NetworkParameters params, byte[] payloadBytes, int offset, MessageSerializer serializer, int length)
throws ProtocolException {
super(params, payloadBytes, offset, serializer, length);
}
/**
* Construct a block object from the Bitcoin wire format. Used in the case of a block
* contained within another message (i.e. for AuxPoW header).
*
* @param params NetworkParameters object.
* @param payloadBytes Bitcoin protocol formatted byte array containing message content.
* @param offset The location of the first payload byte within the array.
* @param parent The message element which contains this block, maybe null for no parent.
* @param serializer the serializer to use for this block.
* @param length The length of message if known. Usually this is provided when deserializing of the wire
* as the length will be provided as part of the header. If unknown then set to Message.UNKNOWN_LENGTH
* @throws ProtocolException
*/
public Block(NetworkParameters params, byte[] payloadBytes, int offset, @Nullable Message parent, MessageSerializer serializer, int length)
throws ProtocolException {
// TODO: Keep the parent
super(params, payloadBytes, offset, serializer, length);
}
/**
* Construct a block initialized with all the given fields.
* @param params Which network the block is for.
* @param version This should usually be set to 1 or 2, depending on if the height is in the coinbase input.
* @param prevBlockHash Reference to previous block in the chain or {@link Sha256Hash#ZERO_HASH} if genesis.
* @param merkleRoot The root of the merkle tree formed by the transactions.
* @param time UNIX time when the block was mined.
* @param difficultyTarget Number which this block hashes lower than.
* @param nonce Arbitrary number to make the block hash lower than the target.
* @param transactions List of transactions including the coinbase.
*/
public Block(NetworkParameters params, long version, Sha256Hash prevBlockHash, Sha256Hash merkleRoot, long time,
long difficultyTarget, long nonce, List transactions) {
super(params);
this.version = version;
this.prevBlockHash = prevBlockHash;
this.merkleRoot = merkleRoot;
this.time = time;
this.difficultyTarget = difficultyTarget;
this.nonce = nonce;
this.transactions = new LinkedList<>();
this.transactions.addAll(transactions);
}
/**
* A utility method that calculates how much new Bitcoin would be created by the block at the given height.
* The inflation of Bitcoin is predictable and drops roughly every 4 years (210,000 blocks). At the dawn of
* the system it was 50 coins per block, in late 2012 it went to 25 coins per block, and so on. The size of
* a coinbase transaction is inflation plus fees.
*
* The half-life is controlled by {@link org.bitcoinj.core.NetworkParameters#getSubsidyDecreaseBlockCount()}.
*
*/
public Coin getBlockInflation(int height) {
return FIFTY_COINS.shiftRight(height / params.getSubsidyDecreaseBlockCount());
}
/**
* Parse transactions from the block.
*
* @param transactionsOffset Offset of the transactions within the block.
* Useful for non-Bitcoin chains where the block header may not be a fixed
* size.
*/
protected void parseTransactions(final int transactionsOffset) throws ProtocolException {
cursor = transactionsOffset;
optimalEncodingMessageSize = HEADER_SIZE;
if (payload.length == cursor) {
// This message is just a header, it has no transactions.
transactionBytesValid = false;
return;
}
int numTransactions = (int) readVarInt();
optimalEncodingMessageSize += VarInt.sizeOf(numTransactions);
transactions = new ArrayList<>(numTransactions);
for (int i = 0; i < numTransactions; i++) {
Transaction tx = new Transaction(params, payload, cursor, this, serializer, UNKNOWN_LENGTH);
// Label the transaction as coming from the P2P network, so code that cares where we first saw it knows.
tx.getConfidence().setSource(TransactionConfidence.Source.NETWORK);
transactions.add(tx);
cursor += tx.getMessageSize();
optimalEncodingMessageSize += tx.getOptimalEncodingMessageSize();
}
transactionBytesValid = serializer.isParseRetainMode();
}
@Override
protected void parse() throws ProtocolException {
// header
cursor = offset;
version = readUint32();
prevBlockHash = readHash();
merkleRoot = readHash();
time = readUint32();
difficultyTarget = readUint32();
nonce = readUint32();
hash = Sha256Hash.wrapReversed(Sha256Hash.hashTwice(payload, offset, cursor - offset));
headerBytesValid = serializer.isParseRetainMode();
// transactions
parseTransactions(offset + HEADER_SIZE);
length = cursor - offset;
}
public int getOptimalEncodingMessageSize() {
if (optimalEncodingMessageSize != 0)
return optimalEncodingMessageSize;
optimalEncodingMessageSize = bitcoinSerialize().length;
return optimalEncodingMessageSize;
}
// default for testing
void writeHeader(OutputStream stream) throws IOException {
// try for cached write first
if (headerBytesValid && payload != null && payload.length >= offset + HEADER_SIZE) {
stream.write(payload, offset, HEADER_SIZE);
return;
}
// fall back to manual write
Utils.uint32ToByteStreamLE(version, stream);
stream.write(prevBlockHash.getReversedBytes());
stream.write(getMerkleRoot().getReversedBytes());
Utils.uint32ToByteStreamLE(time, stream);
Utils.uint32ToByteStreamLE(difficultyTarget, stream);
Utils.uint32ToByteStreamLE(nonce, stream);
}
private void writeTransactions(OutputStream stream) throws IOException {
// check for no transaction conditions first
// must be a more efficient way to do this but I'm tired atm.
if (transactions == null) {
return;
}
// confirmed we must have transactions either cached or as objects.
if (transactionBytesValid && payload != null && payload.length >= offset + length) {
stream.write(payload, offset + HEADER_SIZE, length - HEADER_SIZE);
return;
}
if (transactions != null) {
stream.write(new VarInt(transactions.size()).encode());
for (Transaction tx : transactions) {
tx.bitcoinSerialize(stream);
}
}
}
/**
* Special handling to check if we have a valid byte array for both header
* and transactions
*
* @throws IOException
*/
@Override
public byte[] bitcoinSerialize() {
// we have completely cached byte array.
if (headerBytesValid && transactionBytesValid) {
Preconditions.checkNotNull(payload, "Bytes should never be null if headerBytesValid && transactionBytesValid");
if (length == payload.length) {
return payload;
} else {
// byte array is offset so copy out the correct range.
byte[] buf = new byte[length];
System.arraycopy(payload, offset, buf, 0, length);
return buf;
}
}
// At least one of the two cacheable components is invalid
// so fall back to stream write since we can't be sure of the length.
ByteArrayOutputStream stream = new UnsafeByteArrayOutputStream(length == UNKNOWN_LENGTH ? HEADER_SIZE + guessTransactionsLength() : length);
try {
writeHeader(stream);
writeTransactions(stream);
} catch (IOException e) {
// Cannot happen, we are serializing to a memory stream.
}
return stream.toByteArray();
}
@Override
protected void bitcoinSerializeToStream(OutputStream stream) throws IOException {
writeHeader(stream);
// We may only have enough data to write the header.
writeTransactions(stream);
}
/**
* Provides a reasonable guess at the byte length of the transactions part of the block.
* The returned value will be accurate in 99% of cases and in those cases where not will probably slightly
* oversize.
*
* This is used to preallocate the underlying byte array for a ByteArrayOutputStream. If the size is under the
* real value the only penalty is resizing of the underlying byte array.
*/
private int guessTransactionsLength() {
if (transactionBytesValid)
return payload.length - HEADER_SIZE;
if (transactions == null)
return 0;
int len = VarInt.sizeOf(transactions.size());
for (Transaction tx : transactions) {
// 255 is just a guess at an average tx length
len += tx.length == UNKNOWN_LENGTH ? 255 : tx.length;
}
return len;
}
@Override
protected void unCache() {
// Since we have alternate uncache methods to use internally this will only ever be called by a child
// transaction so we only need to invalidate that part of the cache.
unCacheTransactions();
}
private void unCacheHeader() {
headerBytesValid = false;
if (!transactionBytesValid)
payload = null;
hash = null;
}
private void unCacheTransactions() {
transactionBytesValid = false;
if (!headerBytesValid)
payload = null;
// Current implementation has to uncache headers as well as any change to a tx will alter the merkle root. In
// future we can go more granular and cache merkle root separately so rest of the header does not need to be
// rewritten.
unCacheHeader();
// Clear merkleRoot last as it may end up being parsed during unCacheHeader().
merkleRoot = null;
}
/**
* Calculates the block hash by serializing the block and hashing the
* resulting bytes.
*/
private Sha256Hash calculateHash() {
try {
ByteArrayOutputStream bos = new UnsafeByteArrayOutputStream(HEADER_SIZE);
writeHeader(bos);
return Sha256Hash.wrapReversed(Sha256Hash.hashTwice(bos.toByteArray()));
} catch (IOException e) {
throw new RuntimeException(e); // Cannot happen.
}
}
/**
* Returns the hash of the block (which for a valid, solved block should be below the target) in the form seen on
* the block explorer. If you call this on block 1 in the mainnet chain
* you will get "00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048".
*/
public String getHashAsString() {
return getHash().toString();
}
/**
* Returns the hash of the block (which for a valid, solved block should be
* below the target). Big endian.
*/
@Override
public Sha256Hash getHash() {
if (hash == null)
hash = calculateHash();
return hash;
}
/**
* The number that is one greater than the largest representable SHA-256
* hash.
*/
private static BigInteger LARGEST_HASH = BigInteger.ONE.shiftLeft(256);
/**
* Returns the work represented by this block.
*
* Work is defined as the number of tries needed to solve a block in the
* average case. Consider a difficulty target that covers 5% of all possible
* hash values. Then the work of the block will be 20. As the target gets
* lower, the amount of work goes up.
*/
public BigInteger getWork() throws VerificationException {
BigInteger target = getDifficultyTargetAsInteger();
return LARGEST_HASH.divide(target.add(BigInteger.ONE));
}
/** Returns a copy of the block, but without any transactions. */
public Block cloneAsHeader() {
Block block = new Block(params, BLOCK_VERSION_GENESIS);
copyBitcoinHeaderTo(block);
return block;
}
/** Copy the block without transactions into the provided empty block. */
protected final void copyBitcoinHeaderTo(final Block block) {
block.nonce = nonce;
block.prevBlockHash = prevBlockHash;
block.merkleRoot = getMerkleRoot();
block.version = version;
block.time = time;
block.difficultyTarget = difficultyTarget;
block.transactions = null;
block.hash = getHash();
}
/**
* Returns a multi-line string containing a description of the contents of
* the block. Use for debugging purposes only.
*/
@Override
public String toString() {
StringBuilder s = new StringBuilder();
s.append(" block: \n");
s.append(" hash: ").append(getHashAsString()).append('\n');
s.append(" version: ").append(version);
String bips = Joiner.on(", ").skipNulls().join(isBIP34() ? "BIP34" : null, isBIP66() ? "BIP66" : null,
isBIP65() ? "BIP65" : null);
if (!bips.isEmpty())
s.append(" (").append(bips).append(')');
s.append('\n');
s.append(" previous block: ").append(getPrevBlockHash()).append("\n");
s.append(" merkle root: ").append(getMerkleRoot()).append("\n");
s.append(" time: ").append(time).append(" (").append(Utils.dateTimeFormat(time * 1000)).append(")\n");
s.append(" difficulty target (nBits): ").append(difficultyTarget).append("\n");
s.append(" nonce: ").append(nonce).append("\n");
if (transactions != null && transactions.size() > 0) {
s.append(" with ").append(transactions.size()).append(" transaction(s):\n");
for (Transaction tx : transactions) {
s.append(tx);
}
}
return s.toString();
}
/**
*
Finds a value of nonce that makes the blocks hash lower than the difficulty target. This is called mining, but
* solve() is far too slow to do real mining with. It exists only for unit testing purposes.
*
*
This can loop forever if a solution cannot be found solely by incrementing nonce. It doesn't change
* extraNonce.
*/
public void solve() {
while (true) {
try {
// Is our proof of work valid yet?
if (checkProofOfWork(false))
return;
// No, so increment the nonce and try again.
setNonce(getNonce() + 1);
} catch (VerificationException e) {
throw new RuntimeException(e); // Cannot happen.
}
}
}
/**
* Returns the difficulty target as a 256 bit value that can be compared to a SHA-256 hash. Inside a block the
* target is represented using a compact form. If this form decodes to a value that is out of bounds, an exception
* is thrown.
*/
public BigInteger getDifficultyTargetAsInteger() throws VerificationException {
BigInteger target = Utils.decodeCompactBits(difficultyTarget);
if (target.signum() <= 0 || target.compareTo(params.maxTarget) > 0)
throw new VerificationException("Difficulty target is bad: " + target.toString());
return target;
}
/** Returns true if the hash of the block is OK (lower than difficulty target). */
protected boolean checkProofOfWork(boolean throwException) throws VerificationException {
// This part is key - it is what proves the block was as difficult to make as it claims
// to be. Note however that in the context of this function, the block can claim to be
// as difficult as it wants to be .... if somebody was able to take control of our network
// connection and fork us onto a different chain, they could send us valid blocks with
// ridiculously easy difficulty and this function would accept them.
//
// To prevent this attack from being possible, elsewhere we check that the difficultyTarget
// field is of the right value. This requires us to have the preceeding blocks.
BigInteger target = getDifficultyTargetAsInteger();
BigInteger h = getHash().toBigInteger();
if (h.compareTo(target) > 0) {
// Proof of work check failed!
if (throwException)
throw new VerificationException("Hash is higher than target: " + getHashAsString() + " vs "
+ target.toString(16));
else
return false;
}
return true;
}
private void checkTimestamp() throws VerificationException {
final long allowedTime = Utils.currentTimeSeconds() + ALLOWED_TIME_DRIFT;
if (time > allowedTime)
throw new VerificationException(String.format(Locale.US,
"Block too far in future: %s (%d) vs allowed %s (%d)", Utils.dateTimeFormat(time * 1000), time,
Utils.dateTimeFormat(allowedTime * 1000), allowedTime));
}
private void checkSigOps() throws VerificationException {
// Check there aren't too many signature verifications in the block. This is an anti-DoS measure, see the
// comments for MAX_BLOCK_SIGOPS.
int sigOps = 0;
for (Transaction tx : transactions) {
sigOps += tx.getSigOpCount();
}
if (sigOps > MAX_BLOCK_SIGOPS)
throw new VerificationException("Block had too many Signature Operations");
}
private void checkMerkleRoot() throws VerificationException {
Sha256Hash calculatedRoot = calculateMerkleRoot();
if (!calculatedRoot.equals(merkleRoot)) {
log.error("Merkle tree did not verify");
throw new VerificationException("Merkle hashes do not match: " + calculatedRoot + " vs " + merkleRoot);
}
}
private void checkSegwitCommit() throws VerificationException {
if (transactions == null)
throw new VerificationException("No transactions in block");
final Transaction coinBase = transactions.get(0);
byte[] rootHash = null;
for (TransactionOutput out : coinBase.getOutputs()) {
final byte[] pkScript = out.getScriptBytes();
if (pkScript.length < 38) continue;
final byte[] start = Arrays.copyOfRange(pkScript, 0, 6);
if (Arrays.equals(start, SEGWIT_HEADER)) {
rootHash = Arrays.copyOfRange(pkScript, 6, 38);
}
}
if (rootHash != null
&& (coinBase.countWitnesses() != 1
|| coinBase.getWitness(0).getPushCount() != 1
|| coinBase.getWitness(0).getPush(0).length != 32))
throw new VerificationException("Coinbase witness invalid");
for (int i = 1; i < transactions.size(); i++) {
final Transaction tx = transactions.get(i);
if (tx.hasWitness()) {
if (rootHash == null)
throw new VerificationException("Transaction witness found but no witness commitment present");
break;
}
}
if (rootHash != null) {
final byte[] witnessMerkle = calculateMerkleRoot(true).getReversedBytes();
final byte[] witnessNonce = coinBase.getWitness(0).getPush(0);
final byte[] witnessRoot = Sha256Hash.hashTwice(
witnessMerkle, 0, 32,
witnessNonce, 0, 32);
if (!Arrays.equals(witnessRoot, rootHash))
throw new VerificationException("Witness merkle root invalid. Expected "
+ HEX.encode(rootHash) + " but got " + HEX.encode(witnessRoot));
}
}
private Sha256Hash calculateMerkleRoot() {
return calculateMerkleRoot(false);
}
private Sha256Hash calculateMerkleRoot(boolean segwit) {
List tree = buildMerkleTree(segwit);
return Sha256Hash.wrap(tree.get(tree.size() - 1));
}
private List buildMerkleTree() {
return buildMerkleTree(false);
}
private List buildMerkleTree(boolean segwit) {
// The Merkle root is based on a tree of hashes calculated from the transactions:
//
// root
// / \
// A B
// / \ / \
// t1 t2 t3 t4
//
// The tree is represented as a list: t1,t2,t3,t4,A,B,root where each
// entry is a hash.
//
// The hashing algorithm is double SHA-256. The leaves are a hash of the serialized contents of the transaction.
// The interior nodes are hashes of the concenation of the two child hashes.
//
// This structure allows the creation of proof that a transaction was included into a block without having to
// provide the full block contents. Instead, you can provide only a Merkle branch. For example to prove tx2 was
// in a block you can just provide tx2, the hash(tx1) and B. Now the other party has everything they need to
// derive the root, which can be checked against the block header. These proofs aren't used right now but
// will be helpful later when we want to download partial block contents.
//
// Note that if the number of transactions is not even the last tx is repeated to make it so (see
// tx3 above). A tree with 5 transactions would look like this:
//
// root
// / \
// 1 5
// / \ / \
// 2 3 4 4
// / \ / \ / \
// t1 t2 t3 t4 t5 t5
ArrayList tree = new ArrayList<>();
// Start by adding all the hashes of the transactions as leaves of the tree.
for (Transaction t : transactions) {
tree.add(t.getHash(segwit).getBytes());
}
int levelOffset = 0; // Offset in the list where the currently processed level starts.
// Step through each level, stopping when we reach the root (levelSize == 1).
for (int levelSize = transactions.size(); levelSize > 1; levelSize = (levelSize + 1) / 2) {
// For each pair of nodes on that level:
for (int left = 0; left < levelSize; left += 2) {
// The right hand node can be the same as the left hand, in the case where we don't have enough
// transactions.
int right = Math.min(left + 1, levelSize - 1);
byte[] leftBytes = Utils.reverseBytes(tree.get(levelOffset + left));
byte[] rightBytes = Utils.reverseBytes(tree.get(levelOffset + right));
tree.add(Utils.reverseBytes(hashTwice(leftBytes, 0, 32, rightBytes, 0, 32)));
}
// Move to the next level.
levelOffset += levelSize;
}
return tree;
}
/**
* Verify the transactions on a block.
*
* @param height block height, if known, or -1 otherwise. If provided, used
* to validate the coinbase input script of v2 and above blocks.
* @throws VerificationException if there was an error verifying the block.
*/
private void checkTransactions(final int height, final EnumSet flags)
throws VerificationException {
// The first transaction in a block must always be a coinbase transaction.
if (!transactions.get(0).isCoinBase())
throw new VerificationException("First tx is not coinbase");
if (flags.contains(Block.VerifyFlag.HEIGHT_IN_COINBASE) && height >= BLOCK_HEIGHT_GENESIS) {
transactions.get(0).checkCoinBaseHeight(height);
}
// The rest must not be.
for (int i = 1; i < transactions.size(); i++) {
if (transactions.get(i).isCoinBase())
throw new VerificationException("TX " + i + " is coinbase when it should not be.");
}
}
/**
* Checks the block data to ensure it follows the rules laid out in the network parameters. Specifically,
* throws an exception if the proof of work is invalid, or if the timestamp is too far from what it should be.
* This is not everything that is required for a block to be valid, only what is checkable independent
* of the chain and without a transaction index.
*
* @throws VerificationException
*/
public void verifyHeader() throws VerificationException {
// Prove that this block is OK. It might seem that we can just ignore most of these checks given that the
// network is also verifying the blocks, but we cannot as it'd open us to a variety of obscure attacks.
//
// Firstly we need to ensure this block does in fact represent real work done. If the difficulty is high
// enough, it's probably been done by the network.
checkProofOfWork(true);
checkTimestamp();
}
/**
* Checks the block contents
*
* @param height block height, if known, or -1 otherwise. If valid, used
* to validate the coinbase input script of v2 and above blocks.
* @param flags flags to indicate which tests should be applied (i.e.
* whether to test for height in the coinbase transaction).
* @throws VerificationException if there was an error verifying the block.
*/
public void verifyTransactions(final int height, final EnumSet flags) throws VerificationException {
// Now we need to check that the body of the block actually matches the headers. The network won't generate
// an invalid block, but if we didn't validate this then an untrusted man-in-the-middle could obtain the next
// valid block from the network and simply replace the transactions in it with their own fictional
// transactions that reference spent or non-existant inputs.
if (transactions.isEmpty())
throw new VerificationException("Block had no transactions");
if (this.getOptimalEncodingMessageSize() > MAX_BLOCK_SIZE)
throw new VerificationException("Block larger than MAX_BLOCK_SIZE");
checkTransactions(height, flags);
checkMerkleRoot();
checkSigOps();
if (flags.contains(VerifyFlag.SEGWIT)) checkSegwitCommit();
for (Transaction transaction : transactions)
transaction.verify();
}
/**
* Verifies both the header and that the transactions hash to the merkle root.
*
* @param height block height, if known, or -1 otherwise.
* @param flags flags to indicate which tests should be applied (i.e.
* whether to test for height in the coinbase transaction).
* @throws VerificationException if there was an error verifying the block.
*/
public void verify(final int height, final EnumSet flags) throws VerificationException {
verifyHeader();
verifyTransactions(height, flags);
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return getHash().equals(((Block)o).getHash());
}
@Override
public int hashCode() {
return getHash().hashCode();
}
/**
* Returns the merkle root in big endian form, calculating it from transactions if necessary.
*/
public Sha256Hash getMerkleRoot() {
if (merkleRoot == null) {
//TODO check if this is really necessary.
unCacheHeader();
merkleRoot = calculateMerkleRoot();
}
return merkleRoot;
}
/** Exists only for unit testing. */
void setMerkleRoot(Sha256Hash value) {
unCacheHeader();
merkleRoot = value;
hash = null;
}
/** Adds a transaction to this block. The nonce and merkle root are invalid after this. */
public void addTransaction(Transaction t) {
addTransaction(t, true);
}
/** Adds a transaction to this block, with or without checking the sanity of doing so */
void addTransaction(Transaction t, boolean runSanityChecks) {
unCacheTransactions();
if (transactions == null) {
transactions = new ArrayList<>();
}
t.setParent(this);
if (runSanityChecks && transactions.size() == 0 && !t.isCoinBase())
throw new RuntimeException("Attempted to add a non-coinbase transaction as the first transaction: " + t);
else if (runSanityChecks && transactions.size() > 0 && t.isCoinBase())
throw new RuntimeException("Attempted to add a coinbase transaction when there already is one: " + t);
transactions.add(t);
adjustLength(transactions.size(), t.length);
// Force a recalculation next time the values are needed.
merkleRoot = null;
hash = null;
}
/** Returns the version of the block data structure as defined by the Bitcoin protocol. */
public long getVersion() {
return version;
}
/**
* Returns the hash of the previous block in the chain, as defined by the block header.
*/
public Sha256Hash getPrevBlockHash() {
return prevBlockHash;
}
void setPrevBlockHash(Sha256Hash prevBlockHash) {
unCacheHeader();
this.prevBlockHash = prevBlockHash;
this.hash = null;
}
/**
* Returns the time at which the block was solved and broadcast, according to the clock of the solving node. This
* is measured in seconds since the UNIX epoch (midnight Jan 1st 1970).
*/
public long getTimeSeconds() {
return time;
}
/**
* Returns the time at which the block was solved and broadcast, according to the clock of the solving node.
*/
public Date getTime() {
return new Date(getTimeSeconds()*1000);
}
public void setTime(long time) {
unCacheHeader();
this.time = time;
this.hash = null;
}
/**
* Returns the difficulty of the proof of work that this block should meet encoded in compact form. The {@link
* BlockChain} verifies that this is not too easy by looking at the length of the chain when the block is added.
* To find the actual value the hash should be compared against, use
* {@link org.bitcoinj.core.Block#getDifficultyTargetAsInteger()}. Note that this is not the same as
* the difficulty value reported by the Bitcoin "getdifficulty" RPC that you may see on various block explorers.
* That number is the result of applying a formula to the underlying difficulty to normalize the minimum to 1.
* Calculating the difficulty that way is currently unsupported.
*/
public long getDifficultyTarget() {
return difficultyTarget;
}
/** Sets the difficulty target in compact form. */
public void setDifficultyTarget(long compactForm) {
unCacheHeader();
this.difficultyTarget = compactForm;
this.hash = null;
}
/**
* Returns the nonce, an arbitrary value that exists only to make the hash of the block header fall below the
* difficulty target.
*/
public long getNonce() {
return nonce;
}
/** Sets the nonce and clears any cached data. */
public void setNonce(long nonce) {
unCacheHeader();
this.nonce = nonce;
this.hash = null;
}
/** Returns an immutable list of transactions held in this block, or null if this object represents just a header. */
@Nullable
public List getTransactions() {
return transactions == null ? null : ImmutableList.copyOf(transactions);
}
// ///////////////////////////////////////////////////////////////////////////////////////////////
// Unit testing related methods.
// Used to make transactions unique.
private static int txCounter;
/** Adds a coinbase transaction to the block. This exists for unit tests.
*
* @param height block height, if known, or -1 otherwise.
*/
@VisibleForTesting
void addCoinbaseTransaction(byte[] pubKeyTo, Coin value, final int height) {
unCacheTransactions();
transactions = new ArrayList<>();
Transaction coinbase = new Transaction(params);
final ScriptBuilder inputBuilder = new ScriptBuilder();
if (height >= Block.BLOCK_HEIGHT_GENESIS) {
inputBuilder.number(height);
}
inputBuilder.data(new byte[]{(byte) txCounter, (byte) (txCounter++ >> 8)});
// A real coinbase transaction has some stuff in the scriptSig like the extraNonce and difficulty. The
// transactions are distinguished by every TX output going to a different key.
//
// Here we will do things a bit differently so a new address isn't needed every time. We'll put a simple
// counter in the scriptSig so every transaction has a different hash.
coinbase.addInput(new TransactionInput(params, coinbase,
inputBuilder.build().getProgram()));
coinbase.addOutput(new TransactionOutput(params, coinbase, value,
ScriptBuilder.createOutputScript(ECKey.fromPublicOnly(pubKeyTo)).getProgram()));
transactions.add(coinbase);
coinbase.setParent(this);
coinbase.length = coinbase.unsafeBitcoinSerialize().length;
adjustLength(transactions.size(), coinbase.length);
}
static final byte[] EMPTY_BYTES = new byte[32];
// It's pretty weak to have this around at runtime: fix later.
private static final byte[] pubkeyForTesting = new ECKey().getPubKey();
/**
* Returns a solved block that builds on top of this one. This exists for unit tests.
*/
@VisibleForTesting
public Block createNextBlock(Address to, long version, long time, int blockHeight) {
return createNextBlock(to, version, null, time, pubkeyForTesting, FIFTY_COINS, blockHeight);
}
/**
* Returns a solved block that builds on top of this one. This exists for unit tests.
* In this variant you can specify a public key (pubkey) for use in generating coinbase blocks.
*
* @param height block height, if known, or -1 otherwise.
*/
Block createNextBlock(@Nullable final Address to, final long version,
@Nullable TransactionOutPoint prevOut, final long time,
final byte[] pubKey, final Coin coinbaseValue,
final int height) {
Block b = new Block(params, version);
b.setDifficultyTarget(difficultyTarget);
b.addCoinbaseTransaction(pubKey, coinbaseValue, height);
if (to != null) {
// Add a transaction paying 50 coins to the "to" address.
Transaction t = new Transaction(params);
t.addOutput(new TransactionOutput(params, t, FIFTY_COINS, to));
// The input does not really need to be a valid signature, as long as it has the right general form.
TransactionInput input;
if (prevOut == null) {
input = new TransactionInput(params, t, Script.createInputScript(EMPTY_BYTES, EMPTY_BYTES));
// Importantly the outpoint hash cannot be zero as that's how we detect a coinbase transaction in isolation
// but it must be unique to avoid 'different' transactions looking the same.
byte[] counter = new byte[32];
counter[0] = (byte) txCounter;
counter[1] = (byte) (txCounter++ >> 8);
input.getOutpoint().setHash(Sha256Hash.wrap(counter));
} else {
input = new TransactionInput(params, t, Script.createInputScript(EMPTY_BYTES, EMPTY_BYTES), prevOut);
}
t.addInput(input);
b.addTransaction(t);
}
b.setPrevBlockHash(getHash());
// Don't let timestamp go backwards
if (getTimeSeconds() >= time)
b.setTime(getTimeSeconds() + 1);
else
b.setTime(time);
b.solve();
try {
b.verifyHeader();
} catch (VerificationException e) {
throw new RuntimeException(e); // Cannot happen.
}
if (b.getVersion() != version) {
throw new RuntimeException();
}
return b;
}
@VisibleForTesting
public Block createNextBlock(@Nullable Address to, TransactionOutPoint prevOut) {
return createNextBlock(to, BLOCK_VERSION_GENESIS, prevOut, getTimeSeconds() + 5, pubkeyForTesting, FIFTY_COINS, BLOCK_HEIGHT_UNKNOWN);
}
@VisibleForTesting
public Block createNextBlock(@Nullable Address to, Coin value) {
return createNextBlock(to, BLOCK_VERSION_GENESIS, null, getTimeSeconds() + 5, pubkeyForTesting, value, BLOCK_HEIGHT_UNKNOWN);
}
@VisibleForTesting
public Block createNextBlock(@Nullable Address to) {
return createNextBlock(to, FIFTY_COINS);
}
@VisibleForTesting
public Block createNextBlockWithCoinbase(long version, byte[] pubKey, Coin coinbaseValue, final int height) {
return createNextBlock(null, version, (TransactionOutPoint) null,
Utils.currentTimeSeconds(), pubKey, coinbaseValue, height);
}
/**
* Create a block sending 50BTC as a coinbase transaction to the public key specified.
* This method is intended for test use only.
*/
@VisibleForTesting
Block createNextBlockWithCoinbase(long version, byte[] pubKey, final int height) {
return createNextBlock(null, version, (TransactionOutPoint) null,
Utils.currentTimeSeconds(), pubKey, FIFTY_COINS, height);
}
@VisibleForTesting
boolean isHeaderBytesValid() {
return headerBytesValid;
}
@VisibleForTesting
boolean isTransactionBytesValid() {
return transactionBytesValid;
}
/**
* Return whether this block contains any transactions.
*
* @return true if the block contains transactions, false otherwise (is
* purely a header).
*/
public boolean hasTransactions() {
return !this.transactions.isEmpty();
}
/**
* Returns whether this block conforms to
* BIP34: Height in Coinbase.
*/
public boolean isBIP34() {
return version >= BLOCK_VERSION_BIP34;
}
/**
* Returns whether this block conforms to
* BIP66: Strict DER signatures.
*/
public boolean isBIP66() {
return version >= BLOCK_VERSION_BIP66;
}
/**
* Returns whether this block conforms to
* BIP65: OP_CHECKLOCKTIMEVERIFY.
*/
public boolean isBIP65() {
return version >= BLOCK_VERSION_BIP65;
}
}
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