Add optional support to hide node pubkey with lnproxy

lnproxy.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var lnproxyClient = &http.Client{}
+
+func wrapInvoice(bolt11 string, msat, routing_msat int) (string, error) {
+	req, err := http.NewRequest("GET", fmt.Sprintf("%s/%s?routing_msat=%d", s.LnproxyURL, bolt11, routing_msat), nil)
+	if err != nil {
+		return "", err
+	}
+	resp, err := lnproxyClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	buf := new(strings.Builder)
+	_, err = io.Copy(buf, resp.Body)
+	if err != nil {
+		return "", err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("lnproxy error: %s", buf.String())
+	}
+	wbolt11 := strings.TrimSpace(buf.String())
+	a, h, err := extractInvoiceDetails([]byte(bolt11))
+	if err != nil {
+		return "", err
+	}
+	wa, wh, err := extractInvoiceDetails([]byte(wbolt11))
+	if err != nil {
+		return "", err
+	}
+	if bytes.Compare(h, wh) != 0 {
+		return "", fmt.Errorf("Wrapped payment hash does not match!")
+	}
+	if (a + routing_msat) != wa {
+		return "", fmt.Errorf("Wrapped routing budget too high!")
+	}
+	return wbolt11, nil
+}
+
+var CharSet = []byte("qpzry9x8gf2tvdw0s3jn54khce6mua7l")
+
+var validInvoice = regexp.MustCompile("^lnbc(?:[0-9]+[pnum])?1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]+$")
+
+func extractInvoiceDetails(invoice []byte) (int, []byte, error) {
+	invoice = bytes.ToLower(invoice)
+	pos := bytes.LastIndexByte(invoice, byte('1'))
+	if pos == -1 || !validInvoice.Match(invoice) {
+		return 0, nil, fmt.Errorf("Invalid invoice")
+	}
+
+	var msat int
+	var err error
+	if pos > 4 {
+		msat, err = strconv.Atoi(string(invoice[4 : pos-1]))
+		if err != nil {
+			return 0, nil, err
+		}
+		switch invoice[pos-1] {
+		case byte('p'):
+			msat = msat / 10
+		case byte('n'):
+			msat = msat * 100
+		case byte('u'):
+			msat = msat * 100_000
+		case byte('m'):
+			msat = msat * 100_000_000
+		}
+	}
+	for i := pos + 8; i < len(invoice); {
+		if bytes.Compare(invoice[i:i+3], []byte("pp5")) == 0 {
+			return msat, invoice[i+1+2 : i+1+2+52], nil
+		}
+		i += 3 + bytes.Index(CharSet, invoice[i+1:i+2])*32 + bytes.Index(CharSet, invoice[i+2:i+3])
+	}
+	return 0, nil, fmt.Errorf("No 'p' tag")
+}

lnurl.go

@@ -80,13 +80,27 @@ func handleLNURL(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
+		routing_msat := s.LnproxyRoutingBaseMsat + (s.LnproxyRoutingPpmMsat*msat)/1_000_000
+		if s.Lnproxy {
+			msat = msat - routing_msat
+		}
+
 		bolt11, err := makeInvoice(params, msat, nil)
 		if err != nil {
 			json.NewEncoder(w).Encode(
 				lnurl.ErrorResponse("failed to create invoice: " + err.Error()))
 			return
 		}
 
+		if s.Lnproxy {
+			bolt11, err = wrapInvoice(bolt11, msat, routing_msat)
+			if err != nil {
+				json.NewEncoder(w).Encode(
+					lnurl.ErrorResponse("failed to wrap invoice: " + err.Error()))
+				return
+			}
+		}
+
 		json.NewEncoder(w).Encode(lnurl.LNURLPayResponse2{
 			LNURLResponse: lnurl.LNURLResponse{Status: "OK"},
 			PR:            bolt11,

main.go

@@ -30,6 +30,11 @@ type Settings struct {
 
 	ForceMigrate bool   `envconfig:"FORCE_MIGRATE" required:"false" default:false`
 	TorProxyURL  string `envconfig:"TOR_PROXY_URL"`
+
+	Lnproxy                bool   `envconfig:"LNPROXY" default:"false"`
+	LnproxyURL             string `envconfig:"LNPROXY_URL" default:"https://lnproxy.org/api"`
+	LnproxyRoutingBaseMsat int    `envconfig:"LNPROXY_ROUTING_BASE_MSAT" default:"1000"`
+	LnproxyRoutingPpmMsat  int    `envconfig:"LNPROXY_ROUTING_PPM" default:"6000"`
 }
 
 var s Settings