Implement (experimental!) fetch of bolt11 invoices from (simple) offers

common/features.c

@@ -144,6 +144,8 @@ static const struct feature_style feature_styles[] = {
 	  .copy_style = { [INIT_FEATURE] = FEATURE_REPRESENT,
 			  [NODE_ANNOUNCE_FEATURE] = FEATURE_REPRESENT,
 			  [CHANNEL_FEATURE] = FEATURE_DONT_REPRESENT} },
+	{ OPT_BOLT11_REQUEST,
+	  .copy_style = { [BOLT12_OFFER_FEATURE] = FEATURE_REPRESENT } },
 };
 
 struct dependency {

common/features.h

@@ -157,4 +157,9 @@ struct feature_set *feature_set_dup(const tal_t *ctx,
 
 #define OPT_SHUTDOWN_WRONG_FUNDING		104
 
+/* BOLT-fetch-bolt11 #9:
+ * | 2/3 | `option_bolt11_request` | Invoice request for a bolt11 invoice | 2 | | [BOLT #12][bolt12-bolt11-req] |
+ */
+#define OPT_BOLT11_REQUEST			2
+
 #endif /* LIGHTNING_COMMON_FEATURES_H */

contrib/msggen/msggen/schema.json

@@ -13907,6 +13907,13 @@
             ],
             "added": "v25.02"
           },
+          "bolt11": {
+            "type": "boolean",
+            "description": [
+              "Indicates we should fetch a bolt11 invoice instead (EXPERIMENTAL)"
+            ],
+            "added": "v26.09"
+          },
           "dev_reply_path": {
             "hidden": true
           },
@@ -13925,7 +13932,7 @@
           "invoice": {
             "type": "string",
             "description": [
-              "The BOLT12 invoice we fetched."
+              "The BOLT12 invoice we fetched (or BOLT11 if `bolt11` parameter was set)."
             ]
           },
           "changes": {
@@ -41740,6 +41747,13 @@
                   "BOLT #12 `invoice` payload."
                 ]
               },
+              "bolt11_invoice": {
+                "type": "string",
+                "added": "v26.09",
+                "description": [
+                  "BOLT #11 invoice payload."
+                ]
+              },
               "invoice_error": {
                 "type": "hex",
                 "description": [
@@ -41925,6 +41939,13 @@
                   "BOLT #12 `invoice` payload."
                 ]
               },
+              "bolt11_invoice": {
+                "type": "string",
+                "added": "v26.09",
+                "description": [
+                  "BOLT #11 invoice payload."
+                ]
+              },
               "invoice_error": {
                 "type": "hex",
                 "description": [

contrib/pyln-client/pyln/client/lightning.py

@@ -752,7 +752,7 @@ def feerates(self, style, urgent=None, normal=None, slow=None):
 
     def fetchinvoice(self, offer, amount_msat=None, quantity=None, recurrence_counter=None,
                      recurrence_start=None, recurrence_label=None, timeout=None, payer_note=None,
-                     payer_metadata=None, bip353=None):
+                     payer_metadata=None, bip353=None, bolt11=None):
         """
         Fetch an invoice for an offer.
         """
@@ -767,6 +767,7 @@ def fetchinvoice(self, offer, amount_msat=None, quantity=None, recurrence_counte
             "payer_note": payer_note,
             "payer_metadata": payer_metadata,
             "bip353": bip353,
+            "bolt11": bolt11,
         }
         return self.call("fetchinvoice", payload)
 

doc/schemas/fetchinvoice.json

@@ -76,6 +76,13 @@
         ],
         "added": "v25.02"
       },
+      "bolt11": {
+        "type": "boolean",
+        "description": [
+          "Indicates we should fetch a bolt11 invoice instead (EXPERIMENTAL)"
+        ],
+        "added": "v26.09"
+      },
       "dev_reply_path": {
         "hidden": true
       },
@@ -94,7 +101,7 @@
       "invoice": {
         "type": "string",
         "description": [
-          "The BOLT12 invoice we fetched."
+          "The BOLT12 invoice we fetched (or BOLT11 if `bolt11` parameter was set)."
         ]
       },
       "changes": {

doc/schemas/hook/onion_message_recv.json

@@ -113,6 +113,13 @@
               "BOLT #12 `invoice` payload."
             ]
           },
+          "bolt11_invoice": {
+            "type": "string",
+            "added": "v26.09",
+            "description": [
+              "BOLT #11 invoice payload."
+            ]
+          },
           "invoice_error": {
             "type": "hex",
             "description": [

doc/schemas/hook/onion_message_recv_secret.json

@@ -127,6 +127,13 @@
               "BOLT #12 `invoice` payload."
             ]
           },
+          "bolt11_invoice": {
+            "type": "string",
+            "added": "v26.09",
+            "description": [
+              "BOLT #11 invoice payload."
+            ]
+          },
           "invoice_error": {
             "type": "hex",
             "description": [

lightningd/invoice.c

@@ -1125,7 +1125,6 @@ static struct command_result *json_invoice(struct command *cmd,
 	struct jsonrpc_request *req;
 	struct plugin *plugin;
 	bool *hashonly;
-	const size_t inv_max_label_len = 128;
 	const jsmntok_t *dev_routes;
 
 	info = tal(cmd, struct invoice_info);
@@ -1151,11 +1150,6 @@ static struct command_result *json_invoice(struct command *cmd,
 		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 				    "dev-routes requires --developer");
 
-	if (strlen(info->label->s) > inv_max_label_len) {
-		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
-				    "Label '%s' over %zu bytes", info->label->s, inv_max_label_len);
-	}
-
 	if (strlen(desc_val) > BOLT11_FIELD_BYTE_LIMIT && !*hashonly) {
 		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 				    "Description greater than %d bytes "

lightningd/onion_message.c

@@ -59,6 +59,11 @@ static void onion_message_serialize(struct onion_message_hook_payload *payload,
 	if (payload->om->invoice)
 		json_add_hex_talarr(stream, "invoice", payload->om->invoice);
 
+	if (payload->om->bolt11_invoice)
+		json_add_stringn(stream, "bolt11_invoice",
+				 payload->om->bolt11_invoice,
+				 tal_bytelen(payload->om->bolt11_invoice));
+
 	if (payload->om->invoice_error)
 		json_add_hex_talarr(stream, "invoice_error",
 				    payload->om->invoice_error);

plugins/fetchinvoice.c

@@ -171,7 +171,12 @@ static struct command_result *handle_invreq_response(struct command *cmd,
 	u64 *expected_amount;
 	const struct recurrence *recurrence;
 
-	invtok = json_get_member(buf, om, "invoice");
+	/* Handle bolt11 case separately */
+	if (sent->invreq->invreq_bolt11) {
+		invtok = json_get_member(buf, om, "bolt11_invoice");
+	} else {
+		invtok = json_get_member(buf, om, "invoice");
+	}
 	if (!invtok) {
 		plugin_log(cmd->plugin, LOG_UNUSUAL,
 			   "Neither invoice nor invoice_request_failed in reply %.*s",
@@ -185,6 +190,27 @@ static struct command_result *handle_invreq_response(struct command *cmd,
 		return command_hook_success(cmd);
 	}
 
+	if (sent->invreq->invreq_bolt11) {
+		const char *bolt11, *err;
+
+		/* Sanity check that they sent us a valid reply */
+		bolt11 = json_strdup(tmpctx, buf, invtok);
+		if (!bolt11_decode(tmpctx, bolt11,
+				   plugin_feature_set(cmd->plugin),
+				   NULL,
+				   chainparams,
+				   &err)) {
+			badfield = tal_fmt(tmpctx, "invoice: %s", err);
+			goto badinv;
+		}
+		out = jsonrpc_stream_success(sent->cmd);
+		json_add_string(out, "invoice", bolt11);
+		json_object_start(out, "changes");
+		json_object_end(out);
+		discard_result(command_finished(sent->cmd, out));
+		return command_hook_success(cmd);
+	}
+
 	invbin = json_tok_bin_from_hex(cmd, buf, invtok);
 	cursor = invbin;
 	len = tal_bytelen(invbin);
@@ -929,6 +955,7 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 	u32 *timeout;
 	u64 *quantity;
 	u32 *recurrence_counter, *recurrence_start;
+	bool *bolt11;
 
 	if (!param_check(cmd, buffer, params,
 			 p_req("offer", param_offer, &sent->offer),
@@ -941,6 +968,7 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 			 p_opt("payer_note", param_string, &payer_note),
 			 p_opt("payer_metadata", param_bin_from_hex, &payer_metadata),
 			 p_opt("bip353", param_bip353, &bip353),
+			 p_opt_def("bolt11", param_bool, &bolt11, false),
 			 p_opt("dev_path_use_scidd", param_dev_scidd, &sent->dev_path_use_scidd),
 			 p_opt("dev_reply_path", param_dev_reply_path, &sent->dev_reply_path),
 		   NULL))
@@ -1148,6 +1176,13 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 							strlen(payer_note),
 							0);
 
+	if (*bolt11) {
+		if (!feature_offered(invreq->offer_features, OPT_BOLT11_REQUEST))
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "Cannot request bolt11: offer does not implement it");
+		invreq->invreq_bolt11 = tal(invreq, struct tlv_invoice_request_invreq_bolt11);
+	}
+
 	/* If only checking, we're done now */
 	if (command_check_only(cmd))
 		return command_check_done(cmd);

plugins/offers_invreq_hook.c

@@ -224,9 +224,12 @@ static struct command_result *createinvoice_error(struct command *cmd,
 		      JSON_SCAN(json_to_u32, &code),
 		      JSON_SCAN_TAL(tmpctx, json_strdup, &status)) == NULL
 	    && code == INVOICE_LABEL_ALREADY_EXISTS) {
-		if (streq(status, "unpaid"))
-			return createinvoice_done(cmd, method, buf,
-						  json_get_member(buf, err, "data"), ir);
+		if (streq(status, "unpaid")) {
+			const jsmntok_t *data = json_get_member(buf, err, "data");
+			if (!json_get_member(buf, data, "bolt12"))
+				return fail_invreq(cmd, ir, "invoice previously requested as a bolt11");
+			return createinvoice_done(cmd, method, buf, data, ir);
+		}
 		if (streq(status, "expired"))
 			return fail_invreq(cmd, ir, "invoice expired (cancelled?)");
 	}
@@ -823,6 +826,78 @@ static struct command_result *convert_currency(struct command *cmd,
 	return send_outreq(req);
 }
 
+static struct command_result *bolt11_invoice_done(struct command *cmd,
+						  const char *method,
+						  const char *buf,
+						  const jsmntok_t *result,
+						  struct invreq *ir)
+{
+	struct tlv_onionmsg_tlv *payload;
+	const jsmntok_t *t = json_get_member(buf, result, "bolt11");
+
+	/* In case it was a bolt12 last time! */
+	if (!t)
+		return fail_invreq(cmd, ir, "invoice previously requested as a bolt12");
+
+	payload = tlv_onionmsg_tlv_new(tmpctx);
+	/* Not nul-terminated! */
+	payload->bolt11_invoice = tal_dup_arr(payload, char,
+					      buf + t->start,
+					      t->end - t->start,
+					      0);
+	return send_onion_reply(cmd, ir->reply_path, payload);
+}
+
+static struct command_result *bolt11_listinvoices_done(struct command *cmd,
+						       const char *method,
+						       const char *buf,
+						       const jsmntok_t *result,
+						       struct invreq *ir)
+{
+	const jsmntok_t *arr = json_get_member(buf, result, "invoices"), *inv, *status;
+
+	if (arr->size == 0)
+		return fail_internalerr(cmd, ir, "Listing invoices gave no invoice?");
+
+	inv = arr + 1;
+	status = json_get_member(buf, inv, "status");
+	if (!json_tok_streq(buf, status, "unpaid")) {
+		return fail_invreq(cmd, ir, "Invoice %.*s",
+				   status->end - status->start,
+				   buf + status->start);
+	}
+
+	/* If we hand it the first entry, it's exactly like we just generated it */
+	return bolt11_invoice_done(cmd, method, buf, inv, ir);
+}
+
+/* This can fail because they've already asked for it */
+static struct command_result *bolt11_invoice_error(struct command *cmd,
+						   const char *method,
+						   const char *buf,
+						   const jsmntok_t *err,
+						   struct invreq *ir)
+{
+	struct out_req *req;
+	u32 code;
+	if (json_scan(tmpctx, buf, err,
+		      "{code:%}",
+		      JSON_SCAN(json_to_u32, &code)) != NULL
+	    || code != INVOICE_LABEL_ALREADY_EXISTS) {
+		return fail_internalerr(cmd, ir,
+					"Bad invoice error %.*s",
+					json_tok_full_len(err),
+					json_tok_full(buf, err));
+	}
+
+	req = jsonrpc_request_start(cmd, "listinvoices",
+				    bolt11_listinvoices_done,
+				    error,
+				    ir);
+	json_add_label(req->js, &ir->offer_id, ir->invreq->invreq_payer_id, 0);
+	return send_outreq(req);
+}
+
 static struct command_result *listoffers_done(struct command *cmd,
 					      const char *method,
 					      const char *buf,
@@ -1043,6 +1118,46 @@ static struct command_result *listoffers_done(struct command *cmd,
 			return err;
 	}
 
+	/* BOLT-fetch-bolt11 #12:
+	 * - if `invreq_bolt11` is present:
+	 *   - if `offer_features` does not contain `option_bolt11_request`:
+	 *     - MUST reject the invoice request.
+	 *   - if `invreq_quantity` is present:
+	 *     - MUST reject the invoice request.
+	 * - SHOULD create a BOLT 11 invoice and place it in the
+	 *   `bolt11_invoice` field of a response `onionmsg_tlv`, sent using
+	 *   the `onionmsg_tlv` `reply_path`.
+	 */
+	if (ir->invreq->invreq_bolt11) {
+		struct out_req *req;
+		if (!feature_offered(ir->invreq->offer_features, OPT_BOLT11_REQUEST))
+			return fail_invreq(cmd, ir, "This offer is not bolt11 compatible");
+		if (ir->invreq->invreq_quantity)
+			return fail_invreq(cmd, ir, "Cannot have quantity with bolt11");
+		if (ir->invreq->offer_amount) {
+			if (ir->invreq->invreq_amount
+			    && *ir->invreq->offer_amount != *ir->invreq->invreq_amount)
+				return fail_invreq(cmd, ir, "Requested amount %s != offer amount %s",
+						   fmt_amount_msat(tmpctx, amount_msat(*ir->invreq->invreq_amount)),
+						   fmt_amount_msat(tmpctx, amount_msat(*ir->invreq->offer_amount)));
+			amt = amount_msat(*ir->invreq->offer_amount);
+		} else {
+			if (!ir->invreq->invreq_amount)
+				return fail_invreq(cmd, ir, "Missing invreq_amount");
+			amt = amount_msat(*ir->invreq->invreq_amount);
+		}
+		req = jsonrpc_request_start(cmd, "invoice",
+					    bolt11_invoice_done,
+					    bolt11_invoice_error,
+					    ir);
+		json_add_amount_msat(req->js, "amount_msat", amt);
+		json_add_label(req->js, &ir->offer_id, ir->invreq->invreq_payer_id, 0);
+		json_add_stringn(req->js, "description",
+				 ir->invreq->offer_description,
+				 tal_bytelen(ir->invreq->offer_description));
+		return send_outreq(req);
+	}
+
 	/* BOLT #12:
 	 * A writer of an invoice:
 	 *...