zpay32: add functional opt to error out on unknown feature bit

This commit adds two functional options to the zpay32.Decode function.
`WithKnownFeatureBits` allows the caller to overwrite the default set of
known feature bits used by the function.
`WithErrorOnUnknownFeatureBit` allows the caller to instruct the
function to error out if the invoice that is decoded contaijns unknown
feature bits. We then use this new error-out option from the
`rpcServer`'s `extractPaymentIntent` method.

rpcserver.go

@@ -5210,6 +5210,7 @@ func (r *rpcServer) extractPaymentIntent(rpcPayReq *rpcPaymentRequest) (rpcPayme
 	if rpcPayReq.PaymentRequest != "" {
 		payReq, err := zpay32.Decode(
 			rpcPayReq.PaymentRequest, r.cfg.ActiveNetParams.Params,
+			zpay32.WithErrorOnUnknownFeatureBit(),
 		)
 		if err != nil {
 			return payIntent, err

zpay32/decode.go

@@ -17,10 +17,53 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
+// DecodeOption is a type that can be used to supply functional options to the
+// Decode function.
+type DecodeOption func(*decodeOptions)
+
+// WithKnownFeatureBits is a functional option that overwrites the set of
+// known feature bits. If not set, then LND's lnwire.Features variable will be
+// used by default.
+func WithKnownFeatureBits(features map[lnwire.FeatureBit]string) DecodeOption {
+	return func(options *decodeOptions) {
+		options.knownFeatureBits = features
+	}
+}
+
+// WithErrorOnUnknownFeatureBit is a functional option that will cause the
+// Decode function to return an error if the decoded invoice contains an unknown
+// feature bit.
+func WithErrorOnUnknownFeatureBit() DecodeOption {
+	return func(options *decodeOptions) {
+		options.errorOnUnknownFeature = true
+	}
+}
+
+// decodeOptions holds the set of Decode options.
+type decodeOptions struct {
+	knownFeatureBits      map[lnwire.FeatureBit]string
+	errorOnUnknownFeature bool
+}
+
+// newDecodeOptions constructs the default decodeOptions struct.
+func newDecodeOptions() *decodeOptions {
+	return &decodeOptions{
+		knownFeatureBits:      lnwire.Features,
+		errorOnUnknownFeature: false,
+	}
+}
+
 // Decode parses the provided encoded invoice and returns a decoded Invoice if
 // it is valid by BOLT-0011 and matches the provided active network.
-func Decode(invoice string, net *chaincfg.Params) (*Invoice, error) {
-	decodedInvoice := Invoice{}
+func Decode(invoice string, net *chaincfg.Params, opts ...DecodeOption) (
+	*Invoice, error) {
+
+	options := newDecodeOptions()
+	for _, o := range opts {
+		o(options)
+	}
+
+	var decodedInvoice Invoice
 
 	// Before bech32 decoding the invoice, make sure that it is not too large.
 	// This is done as an anti-DoS measure since bech32 decoding is expensive.
@@ -134,7 +177,7 @@ func Decode(invoice string, net *chaincfg.Params) (*Invoice, error) {
 	// If no feature vector was decoded, populate an empty one.
 	if decodedInvoice.Features == nil {
 		decodedInvoice.Features = lnwire.NewFeatureVector(
-			nil, lnwire.Features,
+			nil, options.knownFeatureBits,
 		)
 	}
 
@@ -144,6 +187,24 @@ func Decode(invoice string, net *chaincfg.Params) (*Invoice, error) {
 		return nil, err
 	}
 
+	if options.errorOnUnknownFeature {
+		// Make sure that we understand all the required feature bits
+		// in the invoice.
+		unknownFeatureBits := decodedInvoice.Features.
+			UnknownRequiredFeatures()
+
+		if len(unknownFeatureBits) > 0 {
+			errStr := fmt.Sprintf("invoice contains " +
+				"unknown feature bits:")
+
+			for _, bit := range unknownFeatureBits {
+				errStr += fmt.Sprintf(" %d,", bit)
+			}
+
+			return nil, fmt.Errorf(strings.TrimRight(errStr, ","))
+		}
+	}
+
 	return &decodedInvoice, nil
 }
 

zpay32/invoice_test.go

@@ -191,6 +191,7 @@ func TestDecodeEncode(t *testing.T) {
 		encodedInvoice string
 		valid          bool
 		decodedInvoice func() *Invoice
+		decodeOpts     []DecodeOption
 		skipEncoding   bool
 		beforeEncoding func(*Invoice)
 	}{
@@ -758,6 +759,70 @@ func TestDecodeEncode(t *testing.T) {
 				i.Destination = nil
 			},
 		},
+		{
+			// Invoice with unknown feature bits but since the
+			// WithErrorOnUnknownFeatureBit option is not provided,
+			// it is not expected to error out.
+			encodedInvoice: "lnbc25m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5vdhkven9v5sxyetpdeessp5zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zygs9q4psqqqqqqqqqqqqqqqpqsqq40wa3khl49yue3zsgm26jrepqr2eghqlx86rttutve3ugd05em86nsefzh4pfurpd9ek9w2vp95zxqnfe2u7ckudyahsa52q66tgzcp6t2dyk",
+			valid:          true,
+			skipEncoding:   true,
+			decodedInvoice: func() *Invoice {
+				return &Invoice{
+					Net:         &chaincfg.MainNetParams,
+					MilliSat:    &testMillisat25mBTC,
+					Timestamp:   time.Unix(1496314658, 0),
+					PaymentHash: &testPaymentHash,
+					PaymentAddr: &specPaymentAddr,
+					Description: &testCoffeeBeans,
+					Destination: testPubKey,
+					Features: lnwire.NewFeatureVector(
+						lnwire.NewRawFeatureVector(
+							9, 15, 99, 100,
+						),
+						lnwire.Features,
+					),
+				}
+			},
+			decodeOpts: []DecodeOption{
+				WithKnownFeatureBits(map[lnwire.FeatureBit]string{
+					9:  "9",
+					15: "15",
+					99: "99",
+				}),
+			},
+		},
+		{
+			// Invoice with unknown feature bits with option set to
+			// error out on unknown feature bit.
+			encodedInvoice: "lnbc25m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5vdhkven9v5sxyetpdeessp5zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zygs9q4psqqqqqqqqqqqqqqqpqsqq40wa3khl49yue3zsgm26jrepqr2eghqlx86rttutve3ugd05em86nsefzh4pfurpd9ek9w2vp95zxqnfe2u7ckudyahsa52q66tgzcp6t2dyk",
+			valid:          false,
+			skipEncoding:   true,
+			decodedInvoice: func() *Invoice {
+				return &Invoice{
+					Net:         &chaincfg.MainNetParams,
+					MilliSat:    &testMillisat25mBTC,
+					Timestamp:   time.Unix(1496314658, 0),
+					PaymentHash: &testPaymentHash,
+					PaymentAddr: &specPaymentAddr,
+					Description: &testCoffeeBeans,
+					Destination: testPubKey,
+					Features: lnwire.NewFeatureVector(
+						lnwire.NewRawFeatureVector(
+							9, 15, 99, 100,
+						),
+						lnwire.Features,
+					),
+				}
+			},
+			decodeOpts: []DecodeOption{
+				WithKnownFeatureBits(map[lnwire.FeatureBit]string{
+					9:  "9",
+					15: "15",
+					99: "99",
+				}),
+				WithErrorOnUnknownFeatureBit(),
+			},
+		},
 	}
 
 	for i, test := range tests {
@@ -773,7 +838,9 @@ func TestDecodeEncode(t *testing.T) {
 				net = decodedInvoice.Net
 			}
 
-			invoice, err := Decode(test.encodedInvoice, net)
+			invoice, err := Decode(
+				test.encodedInvoice, net, test.decodeOpts...,
+			)
 			if !test.valid {
 				require.Error(t, err)
 			} else {