Correct allowance budget checks for WebLN payments

src/app/screens/ConfirmPayment/index.tsx

@@ -17,6 +17,7 @@ import { useNavigationState } from "~/app/hooks/useNavigationState";
 import { USER_REJECTED_ERROR } from "~/common/constants";
 import api from "~/common/lib/api";
 import msg from "~/common/lib/msg";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 
 function ConfirmPayment() {
   const {
@@ -37,8 +38,7 @@ function ConfirmPayment() {
   const paymentRequest = navState.args?.paymentRequest as string;
   const invoice = lightningPayReq.decode(paymentRequest);
 
-  const amountSat =
-    invoice.satoshis || Number(invoice.millisatoshis) / 1000 || 0;
+  const amountSat = getPaymentRequestAmountSats(invoice) ?? 0;
 
   const navigate = useNavigate();
   const auth = useAccount();

src/app/screens/ConfirmPaymentAsync/index.tsx

@@ -15,6 +15,7 @@ import { useNavigationState } from "~/app/hooks/useNavigationState";
 import { USER_REJECTED_ERROR } from "~/common/constants";
 import api from "~/common/lib/api";
 import msg from "~/common/lib/msg";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 
 function ConfirmPaymentAsync() {
   const {
@@ -32,8 +33,7 @@ function ConfirmPaymentAsync() {
   const navState = useNavigationState();
   const paymentRequest = navState.args?.paymentRequest as string;
   const invoice = lightningPayReq.decode(paymentRequest);
-  const amountSat =
-    invoice.satoshis || Number(invoice.millisatoshis) / 1000 || 0;
+  const amountSat = getPaymentRequestAmountSats(invoice) ?? 0;
   const navigate = useNavigate();
 
   const [fiatAmount, setFiatAmount] = useState("");

src/common/utils/__tests__/paymentRequest.test.ts

@@ -0,0 +1,36 @@
+import lightningPayReq from "bolt11-signet";
+import { createPaymentRequest } from "~/fixtures/paymentRequests";
+
+import { getPaymentRequestAmountSats } from "../paymentRequest";
+
+function decode(millisatoshis?: number) {
+  return lightningPayReq.decode(createPaymentRequest(millisatoshis));
+}
+
+describe("getPaymentRequestAmountSats", () => {
+  test("returns the amount for whole-satoshi invoices", () => {
+    expect(getPaymentRequestAmountSats(decode(1_000_000))).toBe(1000);
+  });
+
+  // an invoice for a non-whole number of sats leaves `satoshis` unset; reading it
+  // directly reported a real amount as 0 and bypassed the allowance budget check
+  test("returns the amount for sub-satoshi precision invoices", () => {
+    expect(getPaymentRequestAmountSats(decode(1_000_500))).toBe(1001);
+    expect(getPaymentRequestAmountSats(decode(50_000_001))).toBe(50001);
+  });
+
+  test("rounds up so a payment is never under-reported", () => {
+    expect(getPaymentRequestAmountSats(decode(999))).toBe(1);
+    expect(getPaymentRequestAmountSats(decode(1))).toBe(1);
+  });
+
+  test("returns null for amountless invoices", () => {
+    expect(getPaymentRequestAmountSats(decode())).toBeNull();
+  });
+
+  // an explicit zero amount cannot be paid without the user supplying one, so
+  // it must not be treated as a 0 sat payment that fits any budget
+  test("returns null for invoices with an explicit zero amount", () => {
+    expect(getPaymentRequestAmountSats(decode(0))).toBeNull();
+  });
+});

src/common/utils/paymentRequest.ts

@@ -1,4 +1,21 @@
-import lightningPayReq from "bolt11-signet";
+import lightningPayReq, { PaymentRequestObject } from "bolt11-signet";
+
+// BOLT11 amounts are millisatoshi-precision, but `satoshis` is only set when the
+// invoice amount is a whole number of sats — an invoice for 1000.5 sat decodes to
+// `satoshis: undefined, millisatoshis: "1000500"`. Reading `satoshis` alone (or
+// `satoshis || 0`) therefore reads a real amount as 0, so read millisatoshis,
+// which is always set alongside it. Rounds up so we never under-report what is
+// being spent. Returns null for amountless invoices (no amount, or an explicit
+// zero amount), which cannot be checked against a budget.
+export function getPaymentRequestAmountSats(
+  paymentRequestDetails: PaymentRequestObject
+): number | null {
+  const millisatoshis = Number(paymentRequestDetails.millisatoshis);
+  if (!millisatoshis) {
+    return null;
+  }
+  return Math.ceil(millisatoshis / 1000);
+}
 
 export function getPaymentRequestDescription(paymentRequest: string): string {
   const decodedPaymentRequest = lightningPayReq.decode(paymentRequest);

src/extension/background-script/actions/webln/__tests__/sendPaymentOrPrompt.test.ts

@@ -0,0 +1,121 @@
+import utils from "~/common/lib/utils";
+import db from "~/extension/background-script/db";
+import { allowanceFixture } from "~/fixtures/allowances";
+import { createPaymentRequest } from "~/fixtures/paymentRequests";
+import type { DbAllowance, Message, Sender } from "~/types";
+
+import sendPayment from "../../ln/sendPayment";
+import { sendPaymentOrPrompt } from "../sendPaymentOrPrompt";
+
+jest.mock("~/common/lib/utils", () => ({
+  __esModule: true,
+  default: { openPrompt: jest.fn(() => Promise.resolve({ data: {} })) },
+}));
+
+jest.mock("../../ln/sendPayment", () => ({
+  __esModule: true,
+  default: jest.fn(() => Promise.resolve({ data: {} })),
+}));
+
+const mockAllowances: DbAllowance[] = allowanceFixture;
+
+// the allowance fixture for getalby.com has a remaining budget of 500 sats
+const sender: Sender = { origin: "https://getalby.com" };
+
+function message(millisatoshis?: number): Message {
+  return {
+    application: "LBE",
+    prompt: true,
+    action: "sendPaymentOrPrompt",
+    origin: { internal: true },
+    args: { paymentRequest: createPaymentRequest(millisatoshis) },
+  };
+}
+
+describe("sendPaymentOrPrompt", () => {
+  beforeAll(async () => {
+    await db.allowances.bulkAdd(mockAllowances);
+    await db.allowances.add({
+      ...mockAllowances[0],
+      id: 3,
+      host: "nostr-only.example",
+      enabledFor: ["nostr"],
+    });
+    // enabled for webln with budget to spare, only the `enabled` flag denies it
+    await db.allowances.add({
+      ...mockAllowances[0],
+      id: 4,
+      host: "disabled.example",
+      enabled: false,
+    });
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  test("pays without a prompt when the amount is within the budget", async () => {
+    await sendPaymentOrPrompt(message(100_000), sender);
+
+    expect(sendPayment).toHaveBeenCalled();
+    expect(utils.openPrompt).not.toHaveBeenCalled();
+  });
+
+  test("prompts when the amount exceeds the budget", async () => {
+    await sendPaymentOrPrompt(message(600_000), sender);
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+
+  // a sub-satoshi amount leaves `satoshis` unset on the decoded invoice. Reading
+  // it directly made this look like a 0 sat payment, so it cleared the budget
+  // check and was paid without any confirmation.
+  test("prompts for a sub-satoshi amount that exceeds the budget", async () => {
+    await sendPaymentOrPrompt(message(50_000_001), sender);
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+
+  test("pays without a prompt for a sub-satoshi amount within the budget", async () => {
+    await sendPaymentOrPrompt(message(100_500), sender);
+
+    expect(sendPayment).toHaveBeenCalled();
+    expect(utils.openPrompt).not.toHaveBeenCalled();
+  });
+
+  test("prompts for amountless invoices", async () => {
+    await sendPaymentOrPrompt(message(), sender);
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+
+  test("prompts when the allowance is disabled", async () => {
+    await sendPaymentOrPrompt(message(100_000), {
+      origin: "https://disabled.example",
+    });
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+
+  test("prompts when the allowance is not enabled for webln", async () => {
+    await sendPaymentOrPrompt(message(100_000), {
+      origin: "https://nostr-only.example",
+    });
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+
+  test("prompts when the host has no allowance", async () => {
+    await sendPaymentOrPrompt(message(50_000_001), {
+      origin: "https://example.com",
+    });
+
+    expect(utils.openPrompt).toHaveBeenCalled();
+    expect(sendPayment).not.toHaveBeenCalled();
+  });
+});

src/extension/background-script/actions/webln/sendPaymentOrPrompt.ts

@@ -1,6 +1,7 @@
 import lightningPayReq from "bolt11-signet";
 import utils from "~/common/lib/utils";
 import { getHostFromSender } from "~/common/utils/helpers";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 import { Message, Sender } from "~/types";
 
 import db from "../../db";
@@ -18,7 +19,11 @@ const sendPaymentOrPrompt = async (message: Message, sender: Sender) => {
   }
 
   const paymentRequestDetails = lightningPayReq.decode(paymentRequest);
-  if (await checkAllowance(host, paymentRequestDetails.satoshis || 0)) {
+  const amountInSats = getPaymentRequestAmountSats(paymentRequestDetails);
+
+  // amountless invoices carry no amount to check against the budget, so they
+  // always require explicit confirmation
+  if (amountInSats !== null && (await checkAllowance(host, amountInSats))) {
     return sendPaymentWithAllowance(message);
   } else {
     return payWithPrompt(message);
@@ -31,7 +36,14 @@ async function checkAllowance(host: string, amount: number) {
     .equalsIgnoreCase(host)
     .first();
 
-  return allowance && allowance.remainingBudget > amount; // check that the budget is higher than the amount. amount can be 0
+  const enabledFor = new Set(allowance?.enabledFor);
+
+  return (
+    allowance &&
+    allowance.enabled &&
+    enabledFor.has("webln") &&
+    allowance.remainingBudget > amount // check that the budget is higher than the amount
+  );
 }
 
 async function sendPaymentWithAllowance(message: Message) {

src/extension/background-script/connectors/eclair.ts

@@ -107,7 +107,7 @@ class Eclair implements Connector {
         preimage: paymentPreimage,
         paymentHash,
         route: {
-          total_amt: Math.floor(recipientAmount / 1000),
+          total_amt: Math.ceil(recipientAmount / 1000),
           total_fees: Math.floor(status.feesPaid / 1000),
         },
       },

src/extension/background-script/connectors/galoy.ts

@@ -1,7 +1,10 @@
 import axios, { AxiosRequestConfig } from "axios";
 import lightningPayReq from "bolt11-signet";
 import { ACCOUNT_CURRENCIES, CURRENCIES } from "~/common/constants";
-import { getPaymentRequestDescription } from "~/common/utils/paymentRequest";
+import {
+  getPaymentRequestAmountSats,
+  getPaymentRequestDescription,
+} from "~/common/utils/paymentRequest";
 import { getCurrencyRateWithCache } from "~/extension/background-script/actions/cache/getCurrencyRate";
 import { Account } from "~/types";
 import Connector, {
@@ -378,7 +381,8 @@ class Galoy implements Connector {
     };
 
     const paymentRequestDetails = lightningPayReq.decode(args.paymentRequest);
-    const amountInSats = paymentRequestDetails.satoshis || 0;
+    const amountInSats =
+      getPaymentRequestAmountSats(paymentRequestDetails) ?? 0;
     const paymentHash = paymentRequestDetails.tagsObject.payment_hash || "";
 
     return this.request(query).then(({ data, errors }) => {

src/extension/background-script/connectors/lnbits.ts

@@ -1,6 +1,7 @@
 import lightningPayReq from "bolt11-signet";
 import Hex from "crypto-js/enc-hex";
 import sha256 from "crypto-js/sha256";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 import HashKeySigner from "~/common/utils/signer";
 import { Account } from "~/types";
 
@@ -175,7 +176,8 @@ class LnBits implements Connector {
 
   sendPayment(args: SendPaymentArgs): Promise<SendPaymentResponse> {
     const paymentRequestDetails = lightningPayReq.decode(args.paymentRequest);
-    const amountInSats = paymentRequestDetails.satoshis || 0;
+    const amountInSats =
+      getPaymentRequestAmountSats(paymentRequestDetails) ?? 0;
     return this.request("POST", "/api/v1/payments", this.config.adminkey, {
       bolt11: args.paymentRequest,
       out: true,

src/extension/background-script/connectors/lnc.ts

@@ -289,8 +289,12 @@ class Lnc implements Connector {
         preimage: utils.base64ToHex(data.paymentPreimage.toString()),
         paymentHash: utils.base64ToHex(data.paymentHash.toString()),
         route: {
-          total_amt: parseInt(data.paymentRoute?.totalAmtMsat ?? "0") / 1000,
-          total_fees: parseInt(data.paymentRoute?.totalFeesMsat ?? "0") / 1000,
+          total_amt: Math.ceil(
+            parseInt(data.paymentRoute?.totalAmtMsat ?? "0") / 1000
+          ),
+          total_fees: Math.ceil(
+            parseInt(data.paymentRoute?.totalFeesMsat ?? "0") / 1000
+          ),
         },
       },
     };
@@ -334,8 +338,12 @@ class Lnc implements Connector {
         preimage: utils.base64ToHex(data.paymentPreimage.toString()),
         paymentHash: utils.base64ToHex(data.paymentHash.toString()),
         route: {
-          total_amt: parseInt(data.paymentRoute?.totalAmtMsat ?? "0") / 1000,
-          total_fees: parseInt(data.paymentRoute?.totalFeesMsat ?? "0") / 1000,
+          total_amt: Math.ceil(
+            parseInt(data.paymentRoute?.totalAmtMsat ?? "0") / 1000
+          ),
+          total_fees: Math.ceil(
+            parseInt(data.paymentRoute?.totalFeesMsat ?? "0") / 1000
+          ),
         },
       },
     };

src/extension/background-script/connectors/lndhub.ts

@@ -5,6 +5,7 @@ import Base64 from "crypto-js/enc-base64";
 import Hex from "crypto-js/enc-hex";
 import hmacSHA256 from "crypto-js/hmac-sha256";
 import sha256 from "crypto-js/sha256";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 import HashKeySigner from "~/common/utils/signer";
 import { Account } from "~/types";
 
@@ -257,7 +258,8 @@ export default class LndHub implements Connector {
     // lnbits needs to fix this and return proper route information with a total amount and fees
     if (!data.payment_route) {
       const paymentRequestDetails = lightningPayReq.decode(args.paymentRequest);
-      const amountInSats = paymentRequestDetails.satoshis || 0;
+      const amountInSats =
+        getPaymentRequestAmountSats(paymentRequestDetails) ?? 0;
       data.payment_route = { total_amt: amountInSats, total_fees: 0 };
     }
     return {

src/extension/background-script/connectors/nwc.ts

@@ -4,6 +4,7 @@ import Base64 from "crypto-js/enc-base64";
 import Hex from "crypto-js/enc-hex";
 import UTF8 from "crypto-js/enc-utf8";
 import SHA256 from "crypto-js/sha256";
+import { getPaymentRequestAmountSats } from "~/common/utils/paymentRequest";
 import { Account } from "~/types";
 import Connector, {
   CheckPaymentArgs,
@@ -158,7 +159,7 @@ class NWCConnector implements Connector {
         paymentHash,
         route: {
           // TODO: how to get amount paid for zero-amount invoices?
-          total_amt: Math.floor(parseInt(invoice.millisatoshis || "0") / 1000),
+          total_amt: getPaymentRequestAmountSats(invoice) ?? 0,
           // TODO: How to get fees?
           total_fees: 0,
         },