invoice: Check duplicate preimage when explicitly sprcified.

Reported-by: @mcudev

lightningd/invoice.c

@@ -297,6 +297,16 @@ static void json_invoice(struct command *cmd,
 	/* Generate preimage hash. */
 	sha256(&rhash, r.r, sizeof(r.r));
 
+	/* Check duplicate preimage if explicitly specified.
+	 * We do not check when it is randomly generated, since
+	 * the probability of that matching is very low.
+	 */
+	if (preimagetok &&
+	    wallet_invoice_find_by_rhash(cmd->ld->wallet, &invoice, &rhash)) {
+		command_fail(cmd, "preimage already used");
+		return;
+	}
+
 	/* Construct bolt11 string. */
 	b11 = new_bolt11(cmd, msatoshi_val);
 	b11->chain = get_chainparams(cmd->ld);

tests/test_lightningd.py

@@ -462,6 +462,12 @@ def test_invoice_preimage(self):
         payment_preimage = payment['payment_preimage']
         assert invoice_preimage == payment_preimage
 
+        # Creating a new invoice with same preimage should error.
+        self.assertRaisesRegex(ValueError,
+                               "preimage already used",
+                               l2.rpc.invoice, 123456, 'inv2', '?',
+                               None, None, invoice_preimage)
+
     def test_invoice(self):
         l1 = self.node_factory.get_node()
         l2 = self.node_factory.get_node()

wallet/invoices.c

@@ -347,6 +347,27 @@ bool invoices_find_by_label(struct invoices *invoices,
 	}
 }
 
+bool invoices_find_by_rhash(struct invoices *invoices,
+			    struct invoice *pinvoice,
+			    const struct sha256 *rhash)
+{
+	sqlite3_stmt *stmt;
+
+	stmt = db_prepare(invoices->db,
+			  "SELECT id"
+			  "  FROM invoices"
+			  " WHERE payment_hash = ?;");
+	sqlite3_bind_blob(stmt, 1, rhash, sizeof(*rhash), SQLITE_TRANSIENT);
+	if (sqlite3_step(stmt) == SQLITE_ROW) {
+		pinvoice->id = sqlite3_column_int64(stmt, 0);
+		sqlite3_finalize(stmt);
+		return true;
+	} else {
+		sqlite3_finalize(stmt);
+		return false;
+	}
+}
+
 bool invoices_find_unpaid(struct invoices *invoices,
 			  struct invoice *pinvoice,
 			  const struct sha256 *rhash)

wallet/invoices.h

@@ -76,6 +76,21 @@ bool invoices_find_by_label(struct invoices *invoices,
 			    struct invoice *pinvoice,
 			    const struct json_escaped *label);
 
+/**
+ * invoices_find_by_rhash - Search for an invoice by
+ * payment_hash
+ *
+ * @invoices - the invoice handler.
+ * @pinvoice - pointer to location to load found invoice in.
+ * @rhash - the payment_hash to search for.
+ *
+ * Returns false if no invoice with that rhash exists.
+ * Returns true if found.
+ */
+bool invoices_find_by_rhash(struct invoices *invoices,
+			    struct invoice *pinvoice,
+			    const struct sha256 *rhash);
+
 /**
  * invoices_find_unpaid - Search for an unpaid, unexpired invoice by
  * payment_hash

wallet/test/run-wallet.c

@@ -136,6 +136,11 @@ bool invoices_find_by_label(struct invoices *invoices UNNEEDED,
 			    struct invoice *pinvoice UNNEEDED,
 			    const struct json_escaped *label UNNEEDED)
 { fprintf(stderr, "invoices_find_by_label called!\n"); abort(); }
+/* Generated stub for invoices_find_by_rhash */
+bool invoices_find_by_rhash(struct invoices *invoices UNNEEDED,
+			    struct invoice *pinvoice UNNEEDED,
+			    const struct sha256 *rhash UNNEEDED)
+{ fprintf(stderr, "invoices_find_by_rhash called!\n"); abort(); }
 /* Generated stub for invoices_find_unpaid */
 bool invoices_find_unpaid(struct invoices *invoices UNNEEDED,
 			  struct invoice *pinvoice UNNEEDED,

wallet/wallet.c

@@ -1386,6 +1386,12 @@ bool wallet_invoice_find_by_label(struct wallet *wallet,
 {
 	return invoices_find_by_label(wallet->invoices, pinvoice, label);
 }
+bool wallet_invoice_find_by_rhash(struct wallet *wallet,
+				  struct invoice *pinvoice,
+				  const struct sha256 *rhash)
+{
+	return invoices_find_by_rhash(wallet->invoices, pinvoice, rhash);
+}
 bool wallet_invoice_find_unpaid(struct wallet *wallet,
 				struct invoice *pinvoice,
 				const struct sha256 *rhash)

wallet/wallet.h

@@ -510,6 +510,20 @@ bool wallet_invoice_find_by_label(struct wallet *wallet,
 				  struct invoice *pinvoice,
 				  const struct json_escaped *label);
 
+/**
+ * wallet_invoice_find_by_rhash - Search for an invoice by payment_hash
+ *
+ * @wallet - the wallet to search.
+ * @pinvoice - pointer to location to load found invoice in.
+ * @rhash - the payment_hash to search for.
+ *
+ * Returns false if no invoice with that rhash exists.
+ * Returns true if found.
+ */
+bool wallet_invoice_find_by_rhash(struct wallet *wallet,
+				  struct invoice *pinvoice,
+				  const struct sha256 *rhash);
+
 /**
  * wallet_invoice_find_unpaid - Search for an unpaid, unexpired invoice by
  * payment_hash