From 3d464a0bbce07710081cb5831e2d6ad0883df77c Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Mon, 25 Apr 2016 12:33:37 -0700
Subject: [PATCH] wallet: include input values during utxo selection and tx
 validation

When spending a segwit output, the wallet also needs the input value of
the previous output script. Therefore when selecting outputs the input
value is now returned. Additionally when validating newly signed
outputs the input value as also passed into `txscript.Engine`
---
 wallet/createtx.go | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/wallet/createtx.go b/wallet/createtx.go
index 27c600e..8c600dd 100644
--- a/wallet/createtx.go
+++ b/wallet/createtx.go
@@ -35,8 +35,11 @@ func makeInputSource(eligible []wtxmgr.Credit) txauthor.InputSource {
 	currentTotal := btcutil.Amount(0)
 	currentInputs := make([]*wire.TxIn, 0, len(eligible))
 	currentScripts := make([][]byte, 0, len(eligible))
+	currentInputValues := make([]btcutil.Amount, 0, len(eligible))
+
+	return func(target btcutil.Amount) (btcutil.Amount, []*wire.TxIn,
+		[]btcutil.Amount, [][]byte, error) {
 
-	return func(target btcutil.Amount) (btcutil.Amount, []*wire.TxIn, [][]byte, error) {
 		for currentTotal < target && len(eligible) != 0 {
 			nextCredit := &eligible[0]
 			eligible = eligible[1:]
@@ -44,8 +47,9 @@ func makeInputSource(eligible []wtxmgr.Credit) txauthor.InputSource {
 			currentTotal += nextCredit.Amount
 			currentInputs = append(currentInputs, nextInput)
 			currentScripts = append(currentScripts, nextCredit.PkScript)
+			currentInputValues = append(currentInputValues, nextCredit.Amount)
 		}
-		return currentTotal, currentInputs, currentScripts, nil
+		return currentTotal, currentInputs, currentInputValues, currentScripts, nil
 	}
 }
 
@@ -60,6 +64,7 @@ func (s secretSource) GetKey(addr btcutil.Address) (*btcec.PrivateKey, bool, err
 	if err != nil {
 		return nil, false, err
 	}
+
 	mpka, ok := ma.(waddrmgr.ManagedPubKeyAddress)
 	if !ok {
 		e := fmt.Errorf("managed address type for %v is `%T` but "+
@@ -78,6 +83,7 @@ func (s secretSource) GetScript(addr btcutil.Address) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	msa, ok := ma.(waddrmgr.ManagedScriptAddress)
 	if !ok {
 		e := fmt.Errorf("managed address type for %v is `%T` but "+
@@ -124,9 +130,11 @@ func (w *Wallet) txToOutputs(outputs []*wire.TxOut, account uint32, minconf int3
 		// the imported account, change addresses are created from account 0.
 		var changeAddr btcutil.Address
 		if account == waddrmgr.ImportedAddrAccount {
-			changeAddr, err = w.NewChangeAddress(0)
+			changeAddr, err = w.NewChangeAddress(0,
+				waddrmgr.WitnessPubKey)
 		} else {
-			changeAddr, err = w.NewChangeAddress(account)
+			changeAddr, err = w.NewChangeAddress(account,
+				waddrmgr.WitnessPubKey)
 		}
 		if err != nil {
 			return nil, err
@@ -151,7 +159,7 @@ func (w *Wallet) txToOutputs(outputs []*wire.TxOut, account uint32, minconf int3
 		return nil, err
 	}
 
-	err = validateMsgTx(tx.Tx, tx.PrevScripts)
+	err = validateMsgTx(tx.Tx, tx.PrevScripts, tx.PrevInputValues)
 	if err != nil {
 		return nil, err
 	}
@@ -221,10 +229,10 @@ func (w *Wallet) findEligibleOutputs(account uint32, minconf int32, bs *waddrmgr
 // validateMsgTx verifies transaction input scripts for tx.  All previous output
 // scripts from outputs redeemed by the transaction, in the same order they are
 // spent, must be passed in the prevScripts slice.
-func validateMsgTx(tx *wire.MsgTx, prevScripts [][]byte) error {
+func validateMsgTx(tx *wire.MsgTx, prevScripts [][]byte, inputValues []btcutil.Amount) error {
 	for i, prevScript := range prevScripts {
 		vm, err := txscript.NewEngine(prevScript, tx, i,
-			txscript.StandardVerifyFlags, nil, nil, 0)
+			txscript.StandardVerifyFlags, nil, nil, int64(inputValues[i]))
 		if err != nil {
 			return fmt.Errorf("cannot create script engine: %s", err)
 		}