bolt11: update ctlv expiry, always write it.

As per lightning/bolts#785

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: protocol: bolt11 invoices always include CLTV fields (see lightning-rfc#785)

Author: rustyrussell

Makefile

@@ -24,7 +24,7 @@ CCANDIR := ccan
 
 # Where we keep the BOLT RFCs
 BOLTDIR := ../lightning-rfc/
-BOLTVERSION := 886bf7a430db706b483b7b02d64a82bf175c0b46
+BOLTVERSION := b4132ff24025742ad8e175d52b68380520e9f0b7
 
 -include config.vars
 

common/bolt11.c

@@ -248,9 +248,8 @@ static char *decode_x(struct bolt11 *b11,
 /* BOLT #11:
  *
  * `c` (24): `data_length` variable.  `min_final_cltv_expiry` to use for the
- * last HTLC in the route. Default is 9 if not specified.
+ * last HTLC in the route. Default is 18 if not specified.
  */
-#define DEFAULT_C 9
 static char *decode_c(struct bolt11 *b11,
 		      struct hash_u5 *hu5,
 		      u5 **data, size_t *data_len,
@@ -536,7 +535,11 @@ struct bolt11 *new_bolt11(const tal_t *ctx,
 	b11->msat = NULL;
 	b11->expiry = DEFAULT_X;
 	b11->features = tal_arr(b11, u8, 0);
-	b11->min_final_cltv_expiry = DEFAULT_C;
+	/* BOLT #11:
+	 *   - if the `c` field (`min_final_cltv_expiry`) is not provided:
+	 *     - MUST use an expiry delta of at least 18 when making the payment
+	 */
+	b11->min_final_cltv_expiry = 18;
 	b11->payment_secret = NULL;
 
 	if (msat)
@@ -861,8 +864,8 @@ static void push_field(u5 **data, char type, const void *src, size_t nbits)
  *
  * - if `x` is included:
  *   - SHOULD use the minimum `data_length` possible.
+ * - MUST include one `c` field (`min_final_cltv_expiry`).
  *...
- *  - if `c` is included:
  *   - SHOULD use the minimum `data_length` possible.
  */
 static void push_varlen_field(u5 **data, char type, u64 val)
@@ -1095,8 +1098,10 @@ char *bolt11_encode_(const tal_t *ctx,
 	if (b11->expiry != DEFAULT_X)
 		encode_x(&data, b11->expiry);
 
-	if (b11->min_final_cltv_expiry != DEFAULT_C)
-		encode_c(&data, b11->min_final_cltv_expiry);
+	/* BOLT #11:
+	 *   - MUST include one `c` field (`min_final_cltv_expiry`).
+	 */
+	encode_c(&data, b11->min_final_cltv_expiry);
 
 	if (b11->payment_secret)
 		encode_s(&data, b11->payment_secret);

common/test/run-bolt11.c

@@ -119,6 +119,10 @@ static void test_b11(const char *b11str,
 	}
 	assert(!expect_extra);
 
+	/* FIXME: Spec changed to require c fields, but test vectors don't! */
+	if (b11->min_final_cltv_expiry == 18)
+		return;
+
 	/* Re-encode to check */
 	reproduce = bolt11_encode(tmpctx, b11, false, test_sign, NULL);
 	for (size_t i = 0; i < strlen(reproduce); i++) {
@@ -294,7 +298,7 @@ int main(void)
 			strlen("850aeaf5f69670e8889936fc2e0cff3ceb0c3b5eab8f04ae57767118db673a91"),
 			&b11->payment_hash, sizeof(b11->payment_hash)))
 		abort();
-	b11->min_final_cltv_expiry = 9;
+	b11->min_final_cltv_expiry = 18;
 	b11->receiver_id = node;
 	b11->description = "Payment request with multipart support";
 	b11->expiry = 28800;
@@ -454,7 +458,7 @@ int main(void)
 	/* This one can be encoded, but not decoded */
 	set_feature_bit(&b11->features, 100);
 	badstr = bolt11_encode(tmpctx, b11, false, test_sign, NULL);
-	assert(streq(badstr, "lnbc25m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5vdhkven9v5sxyetpdeessp5zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zygs9q4psqqqqqqqqqqqqqqqpqsqq40wa3khl49yue3zsgm26jrepqr2eghqlx86rttutve3ugd05em86nsefzh4pfurpd9ek9w2vp95zxqnfe2u7ckudyahsa52q66tgzcp6t2dyk"));
+	assert(streq(badstr, "lnbc25m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5vdhkven9v5sxyetpdeescqpjsp5zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zygs9q4psqqqqqqqqqqqqqqqpqsq0hxcz4sktfhmyqsedyuf79vyhah4kv3ruth2hrpvd8tnsceqwj592r4a6w5x2vh5cr4jadanl6qu8lqs8ggxr0pax8mdlwjm2hyyg7gpe7cxue"));
 	/* Empty set of allowed bits, ensures this fails! */
 	fset = tal(tmpctx, struct feature_set);
 	fset->bits[BOLT11_FEATURE] = tal_arr(fset, u8, 0);

tests/test_invoices.py

@@ -584,7 +584,7 @@ def test_decode_unknown(node_factory):
     assert b11['description'] == 'Payment request with multipart support'
     assert b11['expiry'] == 28800
     assert b11['payee'] == '02330d13587b67a85c0a36ea001c4dba14bcd48dda8988f7303275b040bffb6abd'
-    assert b11['min_final_cltv_expiry'] == 9
+    assert b11['min_final_cltv_expiry'] == 18
     extra = only_one(b11['extra'])
     assert extra['tag'] == 'v'
     assert extra['data'] == 'dp68gup69uhnzwfj9cejuvf3xshrwde68qcrswf0d46kcarfwpshyaplw3skw0tdw4k8g6tsv9e8g'