fetchinvoice: allow user to specify bip353 name corresponding to how they got offer.

Changelog-Added: JSON-RPC: `fetchinvoice` BIP 353 name support (`bip353`).
Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

Diff for: .msggen.json

@@ -1547,6 +1547,7 @@
         },
         "FetchinvoiceRequest": {
             "FetchInvoice.amount_msat": 2,
+            "FetchInvoice.bip353": 10,
             "FetchInvoice.offer": 1,
             "FetchInvoice.payer_metadata": 9,
             "FetchInvoice.payer_note": 8,
@@ -6774,6 +6775,10 @@
             "added": "pre-v0.10.1",
             "deprecated": null
         },
+        "FetchInvoice.bip353": {
+            "added": "v25.02",
+            "deprecated": null
+        },
         "FetchInvoice.changes": {
             "added": "pre-v0.10.1",
             "deprecated": null

Diff for: cln-grpc/proto/node.proto

@@ -13124,6 +13124,13 @@
             ],
             "added": "v24.11"
           },
+          "bip353": {
+            "type": "string",
+            "description": [
+              "BIP353 string (optionally with \u20bf) indicating where we fetched the offer from"
+            ],
+            "added": "v25.02"
+          },
           "dev_reply_path": {
             "hidden": true
           },

Diff for: cln-grpc/src/convert.rs

@@ -69,6 +69,13 @@
         ],
         "added": "v24.11"
       },
+      "bip353": {
+        "type": "string",
+        "description": [
+            "BIP353 string (optionally with ₿) indicating where we fetched the offer from"
+        ],
+        "added": "v25.02"
+      },
       "dev_reply_path": {
         "hidden": true
       },

Diff for: cln-rpc/src/model.rs

@@ -18,6 +18,7 @@
 #include <common/onion_message.h>
 #include <common/overflows.h>
 #include <common/route.h>
+#include <common/utils.h>
 #include <errno.h>
 #include <plugins/establish_onion_path.h>
 #include <plugins/fetchinvoice.h>
@@ -823,6 +824,7 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 	struct out_req *req;
 	struct tlv_invoice_request *invreq;
 	struct sent *sent = tal(cmd, struct sent);
+	const char *bip353;
 	u32 *timeout;
 	u64 *quantity;
 	u32 *recurrence_counter, *recurrence_start;
@@ -837,6 +839,7 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 			 p_opt_def("timeout", param_number, &timeout, 60),
 			 p_opt("payer_note", param_string, &payer_note),
 			 p_opt("payer_metadata", param_bin_from_hex, &payer_metadata),
+			 p_opt("bip353", param_string, &bip353),
 			 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))
@@ -1018,6 +1021,37 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 		}
 	}
 
+	/* BOLT #12:
+	 *  - if it received the offer from which it constructed this
+	 *    `invoice_request` using BIP 353 resolution:
+	 *     - MUST include `invreq_bip_353_name` with,
+	 *       - `name` set to the post-₿, pre-@ part of the BIP 353 HRN,
+	 *       - `domain` set to the post-@ part of the BIP 353 HRN.
+	 */
+	if (bip353) {
+		char *at;
+		if (!utf8_check(bip353, strlen(bip353)))
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "invalid UTF-8 for bip353");
+		at = strchr(bip353, '@');
+		if (!at)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "missing @ for bip353");
+
+		/* Strip ₿ if present (0xE2 0x82 0xBF) */
+		if (strstarts(bip353, "₿"))
+			bip353 += strlen("₿");
+		invreq->invreq_bip_353_name
+			= tal(invreq, struct tlv_invoice_request_invreq_bip_353_name);
+		/* Not nul-terminated! */
+		invreq->invreq_bip_353_name->name
+			= tal_dup_arr(invreq->invreq_bip_353_name, u8,
+				      (const u8 *)bip353, at - bip353, 0);
+		invreq->invreq_bip_353_name->domain
+			= tal_dup_arr(invreq->invreq_bip_353_name, u8,
+				      (const u8 *)at + 1, strlen(at + 1), 0);
+	}
+
 	/* We derive transient payer_id from invreq_metadata */
 	invreq->invreq_payer_id = tal(invreq, struct pubkey);
 	if (!payer_key(invreq->invreq_metadata,

Diff for: contrib/msggen/msggen/schema.json

@@ -4544,6 +4544,21 @@ def test_fetchinvoice(node_factory, bitcoind):
     # We've done 3 onion calls: sleep now to avoid hitting ratelimit!
     time.sleep(1)
 
+    # Test bip353.
+    inv1 = l1.rpc.call('fetchinvoice', {'offer': offer1['bolt12'], 'bip353': '₿[email protected]'})['invoice']
+    assert l1.rpc.decode(inv1)['invreq_bip_353_name'] == {'name': 'rusty',
+                                                          'domain': 'blockstream.com'}
+    # Without ₿ works too.
+    inv1 = l1.rpc.call('fetchinvoice', {'offer': offer1['bolt12'], 'bip353': '[email protected]'})['invoice']
+    assert l1.rpc.decode(inv1)['invreq_bip_353_name'] == {'name': 'rusty',
+                                                          'domain': 'blockstream.com'}
+    # Needs @
+    with pytest.raises(RpcError, match="missing @"):
+        l1.rpc.call('fetchinvoice', {'offer': offer1['bolt12'], 'bip353': 'rustyblockstream.com'})
+
+    # We've done 3 onion calls: sleep now to avoid hitting ratelimit!
+    time.sleep(1)
+
     # If we remove plugin, it can no longer give us an invoice.
     l3.rpc.plugin_stop(plugin)