7a5ec82f84
Correctness batch from MARKETPLACE_FLOW_AUDIT.md: - canBuy is disabled when the seller requires escrow (item.escrow === 'required'), so a direct Buy-with-sats cannot bypass it. - ask-seller (31872) is available on an active listing, not only once sold, so a buyer who paid off-app is no longer at a dead end. - payment receipts (lib/receipts.ts) are scoped to the payer's pubkey, so a stale or foreign receipt cannot be attached to a trade by another account viewing the same listing.
106 lines
4 KiB
TypeScript
106 lines
4 KiB
TypeScript
/**
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* Payment receipts — the one part of a trade that can be **cryptographically
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* verified** without a server.
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*
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* A Lightning wallet returns the **preimage** after it pays an invoice. Anyone
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* can then check `sha256(preimage) === payment_hash` (decoded from the bolt11).
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* Published as `["proof","lnpreimage", <preimage>, <payment_hash>]` on a `31871`,
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* it turns "trust me, I paid" into a fact.
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*
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* ⚠️ What it does NOT prove: that goods were delivered. It proves the invoice
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* was paid — real sats, real cost. That's exactly what makes it a strong
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* anti-sybil signal: faking a trade costs money instead of nothing.
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*
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* ⚠️ Applies to **money legs only**. A pure hardware barter has no invoice, so
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* it has no preimage — it stays an *attestation* (see the swap **deposit** idea
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* in NIP.md). Never promote a barter to "verified".
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*/
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import { sha256 } from '@noble/hashes/sha2.js';
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import { bytesToHex, hexToBytes } from '@noble/hashes/utils.js';
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import { getPaymentHashFromBolt11 } from '@/lib/bolt11';
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export interface PaymentReceipt {
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invoice: string;
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/** The wallet's preimage, when the rail returns one (NWC / WebLN / melt). */
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preimage?: string;
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/** Payment hash decoded from the invoice (the commitment we verify against). */
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paymentHash?: string;
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}
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const HEX64 = /^[0-9a-f]{64}$/;
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/** `sha256(preimage) === payment_hash`? — pure, synchronous, trustless. */
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export function verifyPreimage(preimageHex: string, paymentHashHex: string): boolean {
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try {
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const expected = paymentHashHex.trim().toLowerCase();
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if (!HEX64.test(expected)) return false;
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const hash = bytesToHex(sha256(hexToBytes(preimageHex.trim().toLowerCase())));
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return hash === expected;
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} catch {
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return false;
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}
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}
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/** Build a receipt from a paid invoice + the wallet's preimage (if any). */
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export function buildReceipt(invoice: string, preimage?: string): PaymentReceipt {
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return {
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invoice,
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preimage: preimage?.trim() || undefined,
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paymentHash: getPaymentHashFromBolt11(invoice) ?? undefined,
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};
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}
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/** Verify a `["proof","lnpreimage", preimage, payment_hash]` proof tag. */
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export function verifyReceiptProof(preimage?: string, paymentHash?: string): boolean {
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if (!preimage || !paymentHash) return false;
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return verifyPreimage(preimage, paymentHash);
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}
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/**
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* A just-made receipt is held device-locally between the PAY step and the
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* later CONFIRM step (which may be a different component/session), then attached
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* to the `31871` and cleared. localStorage — never published on its own.
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*/
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const STORAGE_KEY = 'skatespots:payment-receipts-v1';
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/** A trade can carry two receipts: the payment and (for barter) a deposit. */
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export type ReceiptSlot = 'payment' | 'deposit';
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function loadAll(): Record<string, PaymentReceipt> {
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try {
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return JSON.parse(localStorage.getItem(STORAGE_KEY) ?? '{}') as Record<string, PaymentReceipt>;
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} catch {
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return {};
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}
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}
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function keyFor(coord: string, slot: ReceiptSlot, owner: string): string {
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const base = slot === 'deposit' ? `${coord}#deposit` : coord;
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// Scope to the payer: a receipt must never be attached to a trade by a
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// different account that happens to view the same listing.
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return owner ? `${owner}|${base}` : base;
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}
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export function saveReceipt(coord: string, receipt: PaymentReceipt, slot: ReceiptSlot = 'payment', owner = ''): void {
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try {
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const all = loadAll();
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all[keyFor(coord, slot, owner)] = receipt;
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localStorage.setItem(STORAGE_KEY, JSON.stringify(all));
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} catch {
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/* storage unavailable — the receipt just isn't carried forward */
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}
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}
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export function getReceipt(coord: string, slot: ReceiptSlot = 'payment', owner = ''): PaymentReceipt | undefined {
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return loadAll()[keyFor(coord, slot, owner)];
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}
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export function clearReceipt(coord: string, slot: ReceiptSlot = 'payment', owner = ''): void {
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try {
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const all = loadAll();
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delete all[keyFor(coord, slot, owner)];
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localStorage.setItem(STORAGE_KEY, JSON.stringify(all));
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} catch {
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/* ignore */
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}
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}
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