From d30aae43e69d682ae86f421d55e8670c7821c3dd Mon Sep 17 00:00:00 2001
From: "Johan T. Halseth" <johanth@gmail.com>
Date: Mon, 1 Feb 2021 14:21:09 +0100
Subject: [PATCH] input/size: add txSize test

Similar to what we do for witnesses, check that the HTLC weight
constants check out.

They actually do not, since the spec is off by one. We ensure we agree
with the spec.
---
 input/size_test.go | 166 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 166 insertions(+)

diff --git a/input/size_test.go b/input/size_test.go
index 2b397395..8008ac85 100644
--- a/input/size_test.go
+++ b/input/size_test.go
@@ -7,12 +7,16 @@ import (
 	"github.com/btcsuite/btcd/blockchain"
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/stretchr/testify/require"
 
+	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
+	"github.com/lightningnetwork/lnd/lnwallet"
 )
 
 const (
@@ -23,6 +27,8 @@ const (
 	// maxDERSignatureSize is the largest possible DER-encoded signature
 	// without the trailing sighash flag.
 	maxDERSignatureSize = 72
+
+	testAmt = btcutil.MaxSatoshi
 )
 
 var (
@@ -40,6 +46,11 @@ var (
 	testPrivkey, _ = btcec.PrivKeyFromBytes(btcec.S256(), make([]byte, 32))
 
 	testTx = wire.NewMsgTx(2)
+
+	testOutPoint = wire.OutPoint{
+		Hash:  chainhash.Hash{},
+		Index: 1,
+	}
 )
 
 // TestTxWeightEstimator tests that transaction weight estimates are calculated
@@ -845,3 +856,158 @@ func TestWitnessSizes(t *testing.T) {
 		})
 	}
 }
+
+// genTimeoutTx creates a signed HTLC second level timeout tx.
+func genTimeoutTx(chanType channeldb.ChannelType) (*wire.MsgTx, error) {
+	// Create the unsigned timeout tx.
+	timeoutTx, err := lnwallet.CreateHtlcTimeoutTx(
+		chanType, testOutPoint, testAmt, testCLTVExpiry,
+		testCSVDelay, testPubkey, testPubkey,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// In order to sign the transcation, generate the script for the output
+	// it spends.
+	witScript, err := input.SenderHTLCScript(
+		testPubkey, testPubkey, testPubkey, testHash160,
+		chanType.HasAnchors(),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	signDesc := &input.SignDescriptor{
+		WitnessScript: witScript,
+		KeyDesc: keychain.KeyDescriptor{
+			PubKey: testPubkey,
+		},
+	}
+
+	// Sign the timeout tx and add the witness.
+	sigHashType := lnwallet.HtlcSigHashType(chanType)
+	timeoutWitness, err := input.SenderHtlcSpendTimeout(
+		&maxDERSignature{}, sigHashType, &dummySigner{},
+		signDesc, timeoutTx,
+	)
+	if err != nil {
+		return nil, err
+	}
+	timeoutTx.TxIn[0].Witness = timeoutWitness
+
+	return timeoutTx, nil
+}
+
+// genSuccessTx creates a signed HTLC second level success tx.
+func genSuccessTx(chanType channeldb.ChannelType) (*wire.MsgTx, error) {
+	// Create the unisgned success tx.
+	successTx, err := lnwallet.CreateHtlcSuccessTx(
+		chanType, testOutPoint, testAmt, testCSVDelay,
+		testPubkey, testPubkey,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// In order to sign the transcation, generate the script for the output
+	// it spends.
+	witScript, err := input.ReceiverHTLCScript(
+		testCLTVExpiry, testPubkey, testPubkey,
+		testPubkey, testHash160, chanType.HasAnchors(),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	signDesc := &input.SignDescriptor{
+		WitnessScript: witScript,
+		KeyDesc: keychain.KeyDescriptor{
+			PubKey: testPubkey,
+		},
+	}
+
+	// Sign the success tx and add the witness.
+	sigHashType := lnwallet.HtlcSigHashType(channeldb.SingleFunderBit)
+	successWitness, err := input.ReceiverHtlcSpendRedeem(
+		&maxDERSignature{}, sigHashType, testPreimage,
+		&dummySigner{}, signDesc, successTx,
+	)
+	if err != nil {
+		return nil, err
+	}
+	successTx.TxIn[0].Witness = successWitness
+
+	return successTx, nil
+
+}
+
+type txSizeTest struct {
+	name      string
+	expWeight int64
+	genTx     func(t *testing.T) *wire.MsgTx
+}
+
+var txSizeTests = []txSizeTest{
+	{
+		name:      "htlc timeout regular ",
+		expWeight: input.HtlcTimeoutWeight,
+		genTx: func(t *testing.T) *wire.MsgTx {
+			tx, err := genTimeoutTx(channeldb.SingleFunderBit)
+			require.NoError(t, err)
+
+			return tx
+		},
+	},
+	{
+		name:      "htlc timeout confirmed",
+		expWeight: input.HtlcTimeoutWeightConfirmed,
+		genTx: func(t *testing.T) *wire.MsgTx {
+			tx, err := genTimeoutTx(channeldb.AnchorOutputsBit)
+			require.NoError(t, err)
+
+			return tx
+		},
+	},
+
+	{
+		name: "htlc success regular",
+		// The weight estimate from the spec is off by one, but it's
+		// okay since we overestimate the weight.
+		expWeight: input.HtlcSuccessWeight - 1,
+		genTx: func(t *testing.T) *wire.MsgTx {
+			tx, err := genSuccessTx(channeldb.SingleFunderBit)
+			require.NoError(t, err)
+
+			return tx
+		},
+	},
+	{
+		name: "htlc success confirmed",
+		// The weight estimate from the spec is off by one, but it's
+		// okay since we overestimate the weight.
+		expWeight: input.HtlcSuccessWeightConfirmed - 1,
+		genTx: func(t *testing.T) *wire.MsgTx {
+			tx, err := genSuccessTx(channeldb.AnchorOutputsBit)
+			require.NoError(t, err)
+
+			return tx
+		},
+	},
+}
+
+// TestWitnessSizes asserts the correctness of our magic tx size constants.
+func TestTxSizes(t *testing.T) {
+	for _, test := range txSizeTests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			tx := test.genTx(t)
+
+			weight := blockchain.GetTransactionWeight(btcutil.NewTx(tx))
+			if weight != test.expWeight {
+				t.Fatalf("size mismatch, want: %v, got: %v",
+					test.expWeight, weight)
+			}
+		})
+	}
+}