/**
* Called when the client provides the multi-sig contract. Checks that the previously-provided
* refund transaction spends this transaction (because we will use it as a base to create payment
* transactions) as well as output value and form (ie it is a 2-of-2 multisig to the correct
* keys).
*
* @param multisigContract The provided multisig contract. Do not mutate this object after this
* call.
* @return A future which completes when the provided multisig contract successfully broadcasts,
* or throws if the broadcast fails for some reason Note that if the network simply rejects
* the transaction, this future will never complete, a timeout should be used.
* @throws VerificationException If the provided multisig contract is not well-formed or does not
* meet previously-specified parameters
*/
public synchronized ListenableFuture<PaymentChannelServerState> provideMultiSigContract(
final Transaction multisigContract) throws VerificationException {
checkNotNull(multisigContract);
checkState(state == State.WAITING_FOR_MULTISIG_CONTRACT);
try {
multisigContract.verify();
this.multisigContract = multisigContract;
this.multisigScript = multisigContract.getOutput(0).getScriptPubKey();
// Check that multisigContract's first output is a 2-of-2 multisig to the correct pubkeys in
// the correct order
final Script expectedScript =
ScriptBuilder.createMultiSigOutputScript(2, Lists.newArrayList(clientKey, serverKey));
if (!Arrays.equals(multisigScript.getProgram(), expectedScript.getProgram()))
throw new VerificationException(
"Multisig contract's first output was not a standard 2-of-2 multisig to client and server in that order.");
this.totalValue = multisigContract.getOutput(0).getValue();
if (this.totalValue.signum() <= 0)
throw new VerificationException(
"Not accepting an attempt to open a contract with zero value.");
} catch (VerificationException e) {
// We couldn't parse the multisig transaction or its output.
log.error("Provided multisig contract did not verify: {}", multisigContract.toString());
throw e;
}
log.info("Broadcasting multisig contract: {}", multisigContract);
state = State.WAITING_FOR_MULTISIG_ACCEPTANCE;
final SettableFuture<PaymentChannelServerState> future = SettableFuture.create();
Futures.addCallback(
broadcaster.broadcastTransaction(multisigContract).future(),
new FutureCallback<Transaction>() {
@Override
public void onSuccess(Transaction transaction) {
log.info(
"Successfully broadcast multisig contract {}. Channel now open.",
transaction.getHashAsString());
try {
// Manually add the multisigContract to the wallet, overriding the isRelevant checks
// so we can track
// it and check for double-spends later
wallet.receivePending(multisigContract, null, true);
} catch (VerificationException e) {
throw new RuntimeException(
e); // Cannot happen, we already called multisigContract.verify()
}
state = State.READY;
future.set(PaymentChannelServerState.this);
}
@Override
public void onFailure(Throwable throwable) {
// Couldn't broadcast the transaction for some reason.
log.error("Broadcast multisig contract failed", throwable);
state = State.ERROR;
future.setException(throwable);
}
});
return future;
}
/**
* When the servers signature for the refund transaction is received, call this to verify it and
* sign the complete refund ourselves.
*
* <p>If this does not throw an exception, we are secure against the loss of funds and can safely
* provide the server with the multi-sig contract to lock in the agreement. In this case, both the
* multisig contract and the refund transaction are automatically committed to wallet so that it
* can handle broadcasting the refund transaction at the appropriate time if necessary.
*/
public synchronized void provideRefundSignature(byte[] theirSignature)
throws VerificationException {
checkNotNull(theirSignature);
checkState(state == State.WAITING_FOR_SIGNED_REFUND);
TransactionSignature theirSig = TransactionSignature.decodeFromBitcoin(theirSignature, true);
if (theirSig.sigHashMode() != Transaction.SigHash.NONE || !theirSig.anyoneCanPay())
throw new VerificationException("Refund signature was not SIGHASH_NONE|SIGHASH_ANYONECANPAY");
// Sign the refund transaction ourselves.
final TransactionOutput multisigContractOutput = multisigContract.getOutput(0);
try {
multisigScript = multisigContractOutput.getScriptPubKey();
} catch (ScriptException e) {
throw new RuntimeException(e); // Cannot happen: we built this ourselves.
}
TransactionSignature ourSignature =
refundTx.calculateSignature(0, myKey, multisigScript, Transaction.SigHash.ALL, false);
// Insert the signatures.
Script scriptSig = ScriptBuilder.createMultiSigInputScript(ourSignature, theirSig);
log.info("Refund scriptSig: {}", scriptSig);
log.info("Multi-sig contract scriptPubKey: {}", multisigScript);
TransactionInput refundInput = refundTx.getInput(0);
refundInput.setScriptSig(scriptSig);
refundInput.verify(multisigContractOutput);
state = State.SAVE_STATE_IN_WALLET;
}
// Create a payment transaction with valueToMe going back to us
private synchronized Wallet.SendRequest makeUnsignedChannelContract(Coin valueToMe) {
Transaction tx = new Transaction(wallet.getParams());
if (!totalValue.subtract(valueToMe).equals(Coin.ZERO)) {
clientOutput.setValue(totalValue.subtract(valueToMe));
tx.addOutput(clientOutput);
}
tx.addInput(multisigContract.getOutput(0));
return Wallet.SendRequest.forTx(tx);
}
/** Returns true if the tx is a valid settlement transaction. */
public synchronized boolean isSettlementTransaction(Transaction tx) {
try {
tx.verify();
tx.getInput(0).verify(multisigContract.getOutput(0));
return true;
} catch (VerificationException e) {
return false;
}
}
PaymentChannelClientState(StoredClientChannel storedClientChannel, Wallet wallet)
throws VerificationException {
// The PaymentChannelClientConnection handles storedClientChannel.active and ensures we aren't
// resuming channels
this.wallet = checkNotNull(wallet);
this.multisigContract = checkNotNull(storedClientChannel.contract);
this.multisigScript = multisigContract.getOutput(0).getScriptPubKey();
this.refundTx = checkNotNull(storedClientChannel.refund);
this.refundFees = checkNotNull(storedClientChannel.refundFees);
this.expiryTime = refundTx.getLockTime();
this.myKey = checkNotNull(storedClientChannel.myKey);
this.serverMultisigKey = null;
this.totalValue = multisigContract.getOutput(0).getValue();
this.valueToMe = checkNotNull(storedClientChannel.valueToMe);
this.storedChannel = storedClientChannel;
this.state = State.READY;
initWalletListeners();
}
private synchronized Transaction makeUnsignedChannelContract(Coin valueToMe)
throws ValueOutOfRangeException {
Transaction tx = new Transaction(wallet.getParams());
tx.addInput(multisigContract.getOutput(0));
// Our output always comes first.
// TODO: We should drop myKey in favor of output key + multisig key separation
// (as its always obvious who the client is based on T2 output order)
tx.addOutput(valueToMe, myKey.toAddress(wallet.getParams()));
return tx;
}
PaymentChannelServerState(
StoredServerChannel storedServerChannel, Wallet wallet, TransactionBroadcaster broadcaster)
throws VerificationException {
synchronized (storedServerChannel) {
this.wallet = checkNotNull(wallet);
this.broadcaster = checkNotNull(broadcaster);
this.multisigContract = checkNotNull(storedServerChannel.contract);
this.multisigScript = multisigContract.getOutput(0).getScriptPubKey();
this.clientKey = ECKey.fromPublicOnly(multisigScript.getChunks().get(1).data);
this.clientOutput = checkNotNull(storedServerChannel.clientOutput);
this.refundTransactionUnlockTimeSecs = storedServerChannel.refundTransactionUnlockTimeSecs;
this.serverKey = checkNotNull(storedServerChannel.myKey);
this.totalValue = multisigContract.getOutput(0).getValue();
this.bestValueToMe = checkNotNull(storedServerChannel.bestValueToMe);
this.bestValueSignature = storedServerChannel.bestValueSignature;
checkArgument(bestValueToMe.equals(Coin.ZERO) || bestValueSignature != null);
this.storedServerChannel = storedServerChannel;
storedServerChannel.state = this;
this.state = State.READY;
}
}
/**
* Called when the client provides the refund transaction. The refund transaction must have one
* input from the multisig contract (that we don't have yet) and one output that the client
* creates to themselves. This object will later be modified when we start getting paid.
*
* @param refundTx The refund transaction, this object will be mutated when payment is
* incremented.
* @param clientMultiSigPubKey The client's pubkey which is required for the multisig output
* @return Our signature that makes the refund transaction valid
* @throws VerificationException If the transaction isnt valid or did not meet the requirements of
* a refund transaction.
*/
public synchronized byte[] provideRefundTransaction(
Transaction refundTx, byte[] clientMultiSigPubKey) throws VerificationException {
checkNotNull(refundTx);
checkNotNull(clientMultiSigPubKey);
checkState(state == State.WAITING_FOR_REFUND_TRANSACTION);
log.info("Provided with refund transaction: {}", refundTx);
// Do a few very basic syntax sanity checks.
refundTx.verify();
// Verify that the refund transaction has a single input (that we can fill to sign the multisig
// output).
if (refundTx.getInputs().size() != 1)
throw new VerificationException("Refund transaction does not have exactly one input");
// Verify that the refund transaction has a time lock on it and a sequence number of zero.
if (refundTx.getInput(0).getSequenceNumber() != 0)
throw new VerificationException("Refund transaction's input's sequence number is non-0");
if (refundTx.getLockTime() < minExpireTime)
throw new VerificationException("Refund transaction has a lock time too soon");
// Verify the transaction has one output (we don't care about its contents, its up to the
// client)
// Note that because we sign with SIGHASH_NONE|SIGHASH_ANYOENCANPAY the client can later add
// more outputs and
// inputs, but we will need only one output later to create the paying transactions
if (refundTx.getOutputs().size() != 1)
throw new VerificationException("Refund transaction does not have exactly one output");
refundTransactionUnlockTimeSecs = refundTx.getLockTime();
// Sign the refund tx with the scriptPubKey and return the signature. We don't have the spending
// transaction
// so do the steps individually.
clientKey = ECKey.fromPublicOnly(clientMultiSigPubKey);
Script multisigPubKey =
ScriptBuilder.createMultiSigOutputScript(2, ImmutableList.of(clientKey, serverKey));
// We are really only signing the fact that the transaction has a proper lock time and don't
// care about anything
// else, so we sign SIGHASH_NONE and SIGHASH_ANYONECANPAY.
TransactionSignature sig =
refundTx.calculateSignature(0, serverKey, multisigPubKey, Transaction.SigHash.NONE, true);
log.info("Signed refund transaction.");
this.clientOutput = refundTx.getOutput(0);
state = State.WAITING_FOR_MULTISIG_CONTRACT;
return sig.encodeToBitcoin();
}