Update project structure and build process

libwallet/sphinx/sphinx.go

@@ -0,0 +1,66 @@
+package sphinx
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/btcsuite/btcd/btcec"
+	"github.com/btcsuite/btcd/chaincfg"
+	lndsphinx "github.com/lightningnetwork/lightning-onion"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+// Validate checks that the onion blob is valid and matches the invoice parameters.
+// Pass 0 as amount to skip amount validation.
+func Validate(
+	onionBlob []byte,
+	paymentHash []byte,
+	paymentSecret []byte,
+	nodeKey *btcec.PrivateKey,
+	expiry uint32,
+	amount lnwire.MilliSatoshi,
+	net *chaincfg.Params,
+) error {
+	router := lndsphinx.NewRouter(nodeKey, net, lndsphinx.NewMemoryReplayLog())
+	if err := router.Start(); err != nil {
+		return fmt.Errorf("could not start router for validating onion blob: %w", err)
+	}
+	onionProcessor := hop.NewOnionProcessor(router)
+	onionProcessor.Start()
+	iterator, code := onionProcessor.DecodeHopIterator(
+		bytes.NewReader(onionBlob),
+		paymentHash,
+		expiry,
+	)
+	if code != lnwire.CodeNone {
+		return fmt.Errorf("failed decode sphinx due to %v", code.String())
+	}
+	payload, err := iterator.HopPayload()
+	if err != nil {
+		return err
+	}
+
+	amountToForward := payload.ForwardingInfo().AmountToForward
+	if amount != 0 && amountToForward > amount {
+		return fmt.Errorf(
+			"sphinx payment amount does not match (%v != %v)", amount, amountToForward,
+		)
+	}
+
+	// Validate payment secret if it exists
+	if payload.MPP != nil {
+		paymentAddr := payload.MPP.PaymentAddr()
+		total := payload.MultiPath().TotalMsat()
+
+		if !bytes.Equal(paymentAddr[:], paymentSecret) {
+			return errors.New("sphinx payment secret does not match")
+		}
+
+		if amountToForward < total {
+			return fmt.Errorf("payment is multipart. forwarded amt = %v, total amt = %v", amountToForward, total)
+		}
+	}
+	return nil
+}