invoice: hack in merkle of invoice as "payment_secret" (EXPERIMENTAL_…

…FEATURES)

This lets actually pay the invoice that fetchinvoice returns.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/invoice.c

@@ -135,6 +135,31 @@ static void invoice_secret(const struct preimage *payment_preimage,
 	memcpy(payment_secret->data, secret.u.u8, sizeof(secret.u.u8));
 }
 
+#if EXPERIMENTAL_FEATURES
+/* FIXME: This is a hack.  The real secret should be a signature of some
+ * onion key, using the payer_id */
+static void invoice_secret_bolt12(struct lightningd *ld,
+				  const char *invstring,
+				  struct secret *payment_secret)
+{
+	char *fail;
+	struct tlv_invoice *inv;
+	struct sha256 merkle;
+
+	inv = invoice_decode(tmpctx, invstring, strlen(invstring),
+			     NULL, NULL, &fail);
+	if (!inv) {
+		log_broken(ld->log, "Unable to decode our invoice %s",
+			   invstring);
+		return;
+	}
+
+	merkle_tlv(inv->fields, &merkle);
+	BUILD_ASSERT(sizeof(*payment_secret) == sizeof(merkle));
+	memcpy(payment_secret, &merkle, sizeof(merkle));
+}
+#endif /* EXPERIMENTAL_FEATURES */
+
 struct invoice_payment_hook_payload {
 	struct lightningd *ld;
 	/* Set to NULL if it is deleted while waiting for plugin */
@@ -348,6 +373,11 @@ invoice_check_payment(const tal_t *ctx,
 	if (payment_secret) {
 		struct secret expected;
 
+#if EXPERIMENTAL_FEATURES
+		if (details->invstring && strstarts(details->invstring, "lni1"))
+			invoice_secret_bolt12(ld, details->invstring, &expected);
+		else
+#endif /* EXPERIMENTAL_FEATURES */
 		invoice_secret(&details->r, &expected);
 		if (!secret_eq_consttime(payment_secret, &expected)) {
 			log_debug(ld->log, "Attept to pay %s with wrong secret",

lightningd/test/run-invoice-select-inchan.c

@@ -760,6 +760,13 @@ struct tlv_invoice *invoice_decode_nosig(const tal_t *ctx UNNEEDED,
 /* Generated stub for invoice_encode */
 char *invoice_encode(const tal_t *ctx UNNEEDED, const struct tlv_invoice *bolt12_tlv UNNEEDED)
 { fprintf(stderr, "invoice_encode called!\n"); abort(); }
+/* Generated stub for invoice_decode */
+struct tlv_invoice *invoice_decode(const tal_t *ctx UNNEEDED,
+				   const char *b12 UNNEEDED, size_t b12len UNNEEDED,
+				   const struct feature_set *our_features UNNEEDED,
+				   const struct chainparams *must_be_chain UNNEEDED,
+				   char **fail UNNEEDED)
+{ fprintf(stderr, "invoice_decode called!\n"); abort(); }
 #endif
 
 static void add_candidate(struct routehint_candidate **candidates, int n,

tests/test_pay.py

@@ -3856,6 +3856,8 @@ def test_fetchinvoice(node_factory, bitcoind):
     inv1 = l1.rpc.call('fetchinvoice', {'offer': offer})
     inv2 = l1.rpc.call('fetchinvoice', {'offer': offer})
     assert inv1 != inv2
+    l1.rpc.pay(inv1['invoice'])
+    l1.rpc.pay(inv2['invoice'])
 
     # Single-use invoice can be fetched multiple times, only paid once.
     offer = l3.rpc.call('offer', {'amount': '1msat',
@@ -3866,3 +3868,34 @@ def test_fetchinvoice(node_factory, bitcoind):
     inv1 = l1.rpc.call('fetchinvoice', {'offer': offer})
     inv2 = l1.rpc.call('fetchinvoice', {'offer': offer})
     assert inv1 != inv2
+
+    l1.rpc.pay(inv1['invoice'])
+
+    # FIXME: We don't report failure yet.
+#    # We can't pay the other one now.
+#    with pytest.raises(RpcError, match='???'):
+#        l1.rpc.pay(inv2['invoice'])
+#
+#    # We can't reuse the offer, either.
+#    with pytest.raises(RpcError, match='???'):
+#        l1.rpc.call('fetchinvoice', {'offer': offer})
+
+    # Recurring offer.
+    offer = l2.rpc.call('offer', {'amount': '1msat',
+                                  'description': 'recurring test',
+                                  'recurrence': '1minutes'})['bolt12']
+    print(offer)
+
+    ret = l1.rpc.call('fetchinvoice', {'offer': offer,
+                                       'recurrence_counter': 0,
+                                       'recurrence_label': 'test recurrence'})
+    print(ret)
+
+    l1.rpc.pay(ret['invoice'], label='test recurrence')
+
+    ret = l1.rpc.call('fetchinvoice', {'offer': offer,
+                                       'recurrence_counter': 1,
+                                       'recurrence_label': 'test recurrence'})
+    print(ret)
+
+    l1.rpc.pay(ret['invoice'], label='test recurrence')