// Signs the first input of the transaction which must spend the multisig contract.
private void signMultisigInput(
Transaction tx, Transaction.SigHash hashType, boolean anyoneCanPay) {
TransactionSignature signature =
tx.calculateSignature(0, serverKey, multisigScript, hashType, anyoneCanPay);
byte[] mySig = signature.encodeToBitcoin();
Script scriptSig =
ScriptBuilder.createMultiSigInputScriptBytes(ImmutableList.of(bestValueSignature, mySig));
tx.getInput(0).setScriptSig(scriptSig);
}
/**
* 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();
}
/**
* Called when the client provides us with a new signature and wishes to increment total payment
* by size. Verifies the provided signature and only updates values if everything checks out. If
* the new refundSize is not the lowest we have seen, it is simply ignored.
*
* @param refundSize How many satoshis of the original contract are refunded to the client (the
* rest are ours)
* @param signatureBytes The new signature spending the multi-sig contract to a new payment
* transaction
* @throws VerificationException If the signature does not verify or size is out of range (incl
* being rejected by the network as dust).
* @return true if there is more value left on the channel, false if it is now fully used up.
*/
public synchronized boolean incrementPayment(Coin refundSize, byte[] signatureBytes)
throws VerificationException, ValueOutOfRangeException, InsufficientMoneyException {
checkState(state == State.READY);
checkNotNull(refundSize);
checkNotNull(signatureBytes);
TransactionSignature signature = TransactionSignature.decodeFromBitcoin(signatureBytes, true);
// We allow snapping to zero for the payment amount because it's treated specially later, but
// not less than
// the dust level because that would prevent the transaction from being relayed/mined.
final boolean fullyUsedUp = refundSize.equals(Coin.ZERO);
if (refundSize.compareTo(clientOutput.getMinNonDustValue()) < 0 && !fullyUsedUp)
throw new ValueOutOfRangeException(
"Attempt to refund negative value or value too small to be accepted by the network");
Coin newValueToMe = totalValue.subtract(refundSize);
if (newValueToMe.signum() < 0)
throw new ValueOutOfRangeException("Attempt to refund more than the contract allows.");
if (newValueToMe.compareTo(bestValueToMe) < 0)
throw new ValueOutOfRangeException("Attempt to roll back payment on the channel.");
// Get the wallet's copy of the multisigContract (ie with confidence information), if this is
// null, the wallet
// was not connected to the peergroup when the contract was broadcast (which may cause issues
// down the road, and
// disables our double-spend check next)
Transaction walletContract = wallet.getTransaction(multisigContract.getHash());
checkNotNull(
walletContract,
"Wallet did not contain multisig contract {} after state was marked READY",
multisigContract.getHash());
// Note that we check for DEAD state here, but this test is essentially useless in production
// because we will
// miss most double-spends due to bloom filtering right now anyway. This will eventually fixed
// by network-wide
// double-spend notifications, so we just wait instead of attempting to add all dependant
// outpoints to our bloom
// filters (and probably missing lots of edge-cases).
if (walletContract.getConfidence().getConfidenceType()
== TransactionConfidence.ConfidenceType.DEAD) {
close();
throw new VerificationException("Multisig contract was double-spent");
}
Transaction.SigHash mode;
// If the client doesn't want anything back, they shouldn't sign any outputs at all.
if (fullyUsedUp) mode = Transaction.SigHash.NONE;
else mode = Transaction.SigHash.SINGLE;
if (signature.sigHashMode() != mode || !signature.anyoneCanPay())
throw new VerificationException(
"New payment signature was not signed with the right SIGHASH flags.");
Wallet.SendRequest req = makeUnsignedChannelContract(newValueToMe);
// Now check the signature is correct.
// Note that the client must sign with SIGHASH_{SINGLE/NONE} | SIGHASH_ANYONECANPAY to allow us
// to add additional
// inputs (in case we need to add significant fee, or something...) and any outputs we want to
// pay to.
Sha256Hash sighash = req.tx.hashForSignature(0, multisigScript, mode, true);
if (!clientKey.verify(sighash, signature))
throw new VerificationException("Signature does not verify on tx\n" + req.tx);
bestValueToMe = newValueToMe;
bestValueSignature = signatureBytes;
updateChannelInWallet();
return !fullyUsedUp;
}