Merge pull request #70 from bjornoj/master

 loop+loopout: validate hash of swap invoice

Author: joostjager

loopout.go

@@ -86,12 +86,12 @@ func newLoopOutSwap(globalCtx context.Context, cfg *swapConfig,
 		return nil, fmt.Errorf("cannot initiate swap: %v", err)
 	}
 
-	err = validateLoopOutContract(cfg.lnd, currentHeight, request, swapResp)
+	err = validateLoopOutContract(cfg.lnd, currentHeight, request, swapHash, swapResp)
 	if err != nil {
 		return nil, err
 	}
 
-	// Instantie a struct that contains all required data to start the swap.
+	// Instantiate a struct that contains all required data to start the swap.
 	initiationTime := time.Now()
 
 	contract := loopdb.LoopOutContract{
@@ -660,21 +660,26 @@ func (s *loopOutSwap) sweep(ctx context.Context,
 // validateLoopOutContract validates the contract parameters against our
 // request.
 func validateLoopOutContract(lnd *lndclient.LndServices,
-	height int32,
-	request *OutRequest,
+	height int32, request *OutRequest, swapHash lntypes.Hash,
 	response *newLoopOutResponse) error {
 
 	// Check invoice amounts.
 	chainParams := lnd.ChainParams
 
-	swapInvoiceAmt, err := swap.GetInvoiceAmt(
+	swapInvoiceHash, swapInvoiceAmt, err := swap.DecodeInvoice(
 		chainParams, response.swapInvoice,
 	)
 	if err != nil {
 		return err
 	}
 
-	prepayInvoiceAmt, err := swap.GetInvoiceAmt(
+	if swapInvoiceHash != swapHash {
+		return fmt.Errorf(
+			"cannot initiate swap, swap invoice hash %v not equal generated swap hash %v",
+			swapInvoiceHash, swapHash)
+	}
+
+	_, prepayInvoiceAmt, err := swap.DecodeInvoice(
 		chainParams, response.prepayInvoice,
 	)
 	if err != nil {

swap/fees.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/zpay32"
 )
 
@@ -26,21 +27,24 @@ func FeeRateAsPercentage(feeRate int64) float64 {
 	return float64(feeRate) / (FeeRateTotalParts / 100)
 }
 
-// GetInvoiceAmt gets the invoice amount. It requires an amount to be
-// specified.
-func GetInvoiceAmt(params *chaincfg.Params,
-	payReq string) (btcutil.Amount, error) {
+// DecodeInvoice gets the hash and the amount of an invoice.
+// It requires an amount to be specified.
+func DecodeInvoice(params *chaincfg.Params,
+	payReq string) (lntypes.Hash, btcutil.Amount, error) {
 
 	swapPayReq, err := zpay32.Decode(
 		payReq, params,
 	)
 	if err != nil {
-		return 0, err
+		return lntypes.Hash{}, 0, err
 	}
 
 	if swapPayReq.MilliSat == nil {
-		return 0, errors.New("no amount in invoice")
+		return lntypes.Hash{}, 0, errors.New("no amount in invoice")
 	}
 
-	return swapPayReq.MilliSat.ToSatoshis(), nil
+	var hash lntypes.Hash
+	copy(hash[:], swapPayReq.PaymentHash[:])
+
+	return hash, swapPayReq.MilliSat.ToSatoshis(), nil
 }