From f972378140c3b1b3cbfa7736b3f271be63ecdc67 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Sat, 10 Sep 2016 13:48:36 -0700
Subject: [PATCH] lnwallet: modify CommitSpendTimeout to expect proper input
 sequence num and tx version

---
 lnwallet/script_utils.go      | 25 ++++++++++++-------------
 lnwallet/script_utils_test.go |  6 ++++--
 2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/lnwallet/script_utils.go b/lnwallet/script_utils.go
index 114e9b3b..e6e12e0f 100644
--- a/lnwallet/script_utils.go
+++ b/lnwallet/script_utils.go
@@ -594,21 +594,20 @@ func commitScriptUnencumbered(key *btcec.PublicKey) ([]byte, error) {
 
 // CommitSpendTimeout constructs a valid witness allowing the owner of a
 // particular commitment transaction to spend the output returning settled
-// funds back to themselves after an absolute block timeout.
+// funds back to themselves after a relative block timeout.  In order to
+// properly spend the transaction, the target input's sequence number should be
+// set accordingly based off of the target relative block timeout within the
+// redeem script.  Additionally, OP_CSV requires that the version of the
+// transaction spending a pkscript with OP_CSV within it *must* be >= 2.
 func CommitSpendTimeout(signer Signer, signDesc *SignDescriptor,
-	blockTimeout uint32, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
+	sweepTx *wire.MsgTx) (wire.TxWitness, error) {
 
-	inputIndex := signDesc.InputIndex
-
-	// In order to properly spend the transaction, we need to set the
-	// sequence number. We do this by convering the relative block delay
-	// into a sequence number value able to be interpeted by
-	// OP_CHECKSEQUENCEVERIFY.
-	sweepTx.TxIn[inputIndex].Sequence = lockTimeToSequence(false, blockTimeout)
-
-	// Additionally, OP_CSV requires that the version of the transaction
-	// spending a pkscript with OP_CSV within it *must* be >= 2.
-	sweepTx.Version = 2
+	// Ensure the transaction version supports the validation of sequence
+	// locks and CSV semantics.
+	if sweepTx.Version < 2 {
+		return nil, fmt.Errorf("version of passed transaction MUST "+
+			"be >= 2, not %v", sweepTx.Version)
+	}
 
 	// With the sequence number in place, we're now able to properly sign
 	// off on the sweep transaction.
diff --git a/lnwallet/script_utils_test.go b/lnwallet/script_utils_test.go
index 665a1ff4..3c6b6449 100644
--- a/lnwallet/script_utils_test.go
+++ b/lnwallet/script_utils_test.go
@@ -68,6 +68,7 @@ func TestCommitmentSpendValidation(t *testing.T) {
 		t.Fatalf("unable to create target output: %v")
 	}
 	sweepTx := wire.NewMsgTx()
+	sweepTx.Version = 2
 	sweepTx.AddTxIn(wire.NewTxIn(&wire.OutPoint{commitmentTx.TxSha(), 0}, nil, nil))
 	sweepTx.AddTxOut(&wire.TxOut{
 		PkScript: targetOutput,
@@ -79,6 +80,7 @@ func TestCommitmentSpendValidation(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unable to generate alice delay script: %v")
 	}
+	sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, csvTimeout)
 	signDesc := &SignDescriptor{
 		RedeemScript: delayScript,
 		SigHashes:    txscript.NewTxSigHashes(sweepTx),
@@ -89,14 +91,14 @@ func TestCommitmentSpendValidation(t *testing.T) {
 		InputIndex: 0,
 	}
 	aliceWitnessSpend, err := CommitSpendTimeout(aliceSelfOutputSigner,
-		signDesc, csvTimeout, sweepTx)
+		signDesc, sweepTx)
 	if err != nil {
 		t.Fatalf("unable to generate delay commit spend witness :%v")
 	}
 	sweepTx.TxIn[0].Witness = aliceWitnessSpend
 	vm, err := txscript.NewEngine(delayOutput.PkScript,
 		sweepTx, 0, txscript.StandardVerifyFlags, nil,
-		signDesc.SigHashes, int64(channelBalance))
+		nil, int64(channelBalance))
 	if err != nil {
 		t.Fatalf("unable to create engine: %v", err)
 	}