From 10f333b041f04f5042b0910c0d6366b1f40f13e7 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 26 Feb 2025 17:27:01 +1030
Subject: [PATCH] devtools/bolt12-cli: fix interpretation of blindedpay,
 amounts.

The old blindedpay fields would have an entry per hop, but that was changed
to a single per-path entry.  The devtools hadn't caught up.

Similarly, it didn't like descriptionless offer fields in invreqs and invoices.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 devtools/bolt12-cli.c | 40 ++++++++++++++++++++++++----------------
 tests/test_misc.py    | 10 ++++++++++
 2 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/devtools/bolt12-cli.c b/devtools/bolt12-cli.c
index 69f6a67ca..1965dfc98 100644
--- a/devtools/bolt12-cli.c
+++ b/devtools/bolt12-cli.c
@@ -266,8 +266,6 @@ static bool print_blindedpaths(const char *fieldname,
 			       struct blinded_path **paths,
 			       struct blinded_payinfo **blindedpay)
 {
-	size_t bp_idx = 0;
-
 	for (size_t i = 0; i < tal_count(paths); i++) {
 		struct blinded_path_hop **p = paths[i]->path;
 		printf("%s %zu/%zu: first_path_key %s ",
@@ -282,22 +280,24 @@ static bool print_blindedpaths(const char *fieldname,
 			       fmt_pubkey(tmpctx,
 					      &p[j]->blinded_node_id),
 			       tal_hex(tmpctx, p[j]->encrypted_recipient_data));
-			if (blindedpay) {
-				if (bp_idx < tal_count(blindedpay))
-					printf("fee=%u/%u,cltv=%u,features=%s",
-					       blindedpay[bp_idx]->fee_base_msat,
-					       blindedpay[bp_idx]->fee_proportional_millionths,
-					       blindedpay[bp_idx]->cltv_expiry_delta,
-					       tal_hex(tmpctx,
-						       blindedpay[bp_idx]->features));
-				bp_idx++;
-			}
+		}
+		if (i < tal_count(blindedpay)) {
+			printf(" blindedpay: fee=%u/%u,cltv=%u,features=%s",
+			       blindedpay[i]->fee_base_msat,
+			       blindedpay[i]->fee_proportional_millionths,
+			       blindedpay[i]->cltv_expiry_delta,
+			       tal_hex(tmpctx, blindedpay[i]->features));
 		}
 		printf("\n");
 	}
-	if (blindedpay && tal_count(blindedpay) != bp_idx) {
+	/* BOLT #12:
+	 *   - MUST reject the invoice if `invoice_blindedpay` does not
+	 *     contain exactly one `blinded_payinfo` per
+	 *     `invoice_paths`.`blinded_path`.
+	 */
+	if (blindedpay && tal_count(blindedpay) != tal_count(paths)) {
 		fprintf(stderr, "Expected %zu blindedpay fields, got %zu\n",
-			bp_idx, tal_count(blindedpay));
+			tal_count(paths), tal_count(blindedpay));
 		return false;
 	}
 	return true;
@@ -893,7 +893,11 @@ int main(int argc, char *argv[])
 			well_formed &= print_offer_amount(invreq->offer_chains,
 							  invreq->offer_currency,
 							  *invreq->offer_amount);
-		if (must_have(invreq, offer_description))
+		if (invreq->offer_amount && !invreq->offer_description) {
+			fprintf(stderr, "Missing offer_description (with offer_amount)\n");
+			well_formed = false;
+		}
+		if (invreq->offer_description)
 			well_formed &= print_utf8("offer_description", invreq->offer_description);
 		if (invreq->offer_features)
 			print_features("offer_features", invreq->offer_features);
@@ -971,7 +975,11 @@ int main(int argc, char *argv[])
 			well_formed &= print_offer_amount(invoice->offer_chains,
 							  invoice->offer_currency,
 							  *invoice->offer_amount);
-		if (must_have(invoice, offer_description))
+		if (invoice->offer_amount && !invoice->offer_description) {
+			fprintf(stderr, "Missing offer_description (with offer_amount)\n");
+			well_formed = false;
+		}
+		if (invoice->offer_description)
 			well_formed &= print_utf8("offer_description", invoice->offer_description);
 		if (invoice->offer_features)
 			print_features("offer_features", invoice->offer_features);
diff --git a/tests/test_misc.py b/tests/test_misc.py
index b8e26ff05..d21c5cff7 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -4680,3 +4680,13 @@ def test_listaddresses(node_factory):
     # start and limit from future
     addresses = l1.rpc.listaddresses(start=21, limit=5)["addresses"]
     assert len(addresses) == 0
+
+
+def test_bolt12_invoice_decode(node_factory):
+    """Test decode of a real invoice."""
+    l1 = node_factory.get_node()
+
+    inv = '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'
+
+    assert l1.rpc.decode(inv)['valid'] is True
+    subprocess.run(["devtools/bolt12-cli", "decode", inv], check=True)