Restore legacy onion (damn you lnd!)

common/sphinx.c

@@ -1,6 +1,7 @@
 #include "config.h"
 #include <assert.h>
 
+#include <ccan/array_size/array_size.h>
 #include <ccan/mem/mem.h>
 #include <common/onion_decode.h>
 #include <common/onionreply.h>
@@ -122,6 +123,33 @@ bool sphinx_add_hop_has_length(struct sphinx_path *path, const struct pubkey *pu
 	return true;
 }
 
+static u8 *make_v0_hop(const tal_t *ctx,
+		       const struct short_channel_id *scid,
+		       struct amount_msat forward, u32 outgoing_cltv)
+{
+	const u8 padding[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			      0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+	/* Prepend 0 byte for realm */
+	u8 *buf = tal_arrz(ctx, u8, 1);
+	towire_short_channel_id(&buf, *scid);
+	towire_amount_msat(&buf, forward);
+	towire_u32(&buf, outgoing_cltv);
+	towire(&buf, padding, ARRAY_SIZE(padding));
+	assert(tal_bytelen(buf) == 1 + 32);
+	return buf;
+}
+
+void sphinx_add_v0_hop(struct sphinx_path *path, const struct pubkey *pubkey,
+		       const struct short_channel_id *scid,
+		       struct amount_msat forward, u32 outgoing_cltv)
+{
+	struct sphinx_hop sp;
+
+	sp.raw_payload = make_v0_hop(path, scid, forward, outgoing_cltv);
+	sp.pubkey = *pubkey;
+	tal_arr_expand(&path->hops, sp);
+}
+
 void sphinx_add_hop(struct sphinx_path *path, const struct pubkey *pubkey,
 		    const u8 *payload TAKES)
 {
@@ -639,12 +667,55 @@ struct route_step *process_onionpacket(
 
 	/* Any of these could fail, falling thru with cursor == NULL */
 	payload_size = fromwire_bigsize(&cursor, &max);
-	/* FIXME: raw_payload *includes* the length, which is redundant and
-	 * means we can't just ust fromwire_tal_arrn. */
-	fromwire_pad(&cursor, &max, payload_size);
-	if (cursor != NULL)
-		step->raw_payload = tal_dup_arr(step, u8, paddedheader,
-						cursor - paddedheader, 0);
+
+	/* Legacy!  0 length payload means fixed 32 byte structure */
+	if (payload_size == 0 && max >= 32) {
+		struct tlv_payload *legacy = tlv_payload_new(tmpctx);
+		const u8 *legacy_cursor = cursor;
+		size_t legacy_max = 32;
+		u8 *onwire_tlv;
+
+		legacy->amt_to_forward = tal(legacy, u64);
+		legacy->outgoing_cltv_value = tal(legacy, u32);
+		legacy->short_channel_id = tal(legacy, struct short_channel_id);
+
+		/* BOLT-obsolete #4:
+		 * ## Legacy `hop_data` payload format
+		 *
+		 * The `hop_data` format is identified by a single `0x00`-byte
+		 * length, for backward compatibility.  Its payload is defined
+		 * as:
+		 *
+		 * 1. type: `hop_data` (for `realm` 0)
+		 * 2. data:
+		 *    * [`short_channel_id`:`short_channel_id`]
+		 *    * [`u64`:`amt_to_forward`]
+		 *    * [`u32`:`outgoing_cltv_value`]
+		 *    * [`12*byte`:`padding`]
+		 */
+		*legacy->short_channel_id = fromwire_short_channel_id(&legacy_cursor, &legacy_max);
+		*legacy->amt_to_forward = fromwire_u64(&legacy_cursor, &legacy_max);
+		*legacy->outgoing_cltv_value = fromwire_u32(&legacy_cursor, &legacy_max);
+
+		/* Re-linearize it as a modern TLV! */
+		onwire_tlv = tal_arr(tmpctx, u8, 0);
+		towire_tlv_payload(&onwire_tlv, legacy);
+
+		/* Length, then tlv */
+		step->raw_payload = tal_arr(step, u8, 0);
+		towire_bigsize(&step->raw_payload, tal_bytelen(onwire_tlv));
+		towire_u8_array(&step->raw_payload, onwire_tlv, tal_bytelen(onwire_tlv));
+
+		payload_size = 32;
+		fromwire_pad(&cursor, &max, payload_size);
+	} else {
+		/* FIXME: raw_payload *includes* the length, which is redundant and
+		 * means we can't just ust fromwire_tal_arrn. */
+		fromwire_pad(&cursor, &max, payload_size);
+		if (cursor != NULL)
+			step->raw_payload = tal_dup_arr(step, u8, paddedheader,
+							cursor - paddedheader, 0);
+	}
 	fromwire_hmac(&cursor, &max, &step->next->hmac);
 
 	/* BOLT #4:

common/sphinx.h

@@ -216,6 +216,13 @@ bool sphinx_add_hop_has_length(struct sphinx_path *path, const struct pubkey *pu
 void sphinx_add_hop(struct sphinx_path *path, const struct pubkey *pubkey,
 		    const u8 *payload TAKES);
 
+/**
+ * Do not use, function is cursed.
+ */
+void sphinx_add_v0_hop(struct sphinx_path *path, const struct pubkey *pubkey,
+		       const struct short_channel_id *scid,
+		       struct amount_msat forward, u32 outgoing_cltv);
+
 /**
  * Compute the size of the serialized payloads.
  */

common/test/run-sphinx-xor_cipher_stream.c

@@ -108,9 +108,15 @@ void subkey_from_hmac(const char *prefix UNNEEDED,
 		      const struct secret *base UNNEEDED,
 		      struct secret *key UNNEEDED)
 { fprintf(stderr, "subkey_from_hmac called!\n"); abort(); }
+/* Generated stub for tlv_payload_new */
+struct tlv_payload *tlv_payload_new(const tal_t *ctx UNNEEDED)
+{ fprintf(stderr, "tlv_payload_new called!\n"); abort(); }
 /* Generated stub for towire */
 void towire(u8 **pptr UNNEEDED, const void *data UNNEEDED, size_t len UNNEEDED)
 { fprintf(stderr, "towire called!\n"); abort(); }
+/* Generated stub for towire_amount_msat */
+void towire_amount_msat(u8 **pptr UNNEEDED, const struct amount_msat msat UNNEEDED)
+{ fprintf(stderr, "towire_amount_msat called!\n"); abort(); }
 /* Generated stub for towire_bigsize */
 void towire_bigsize(u8 **pptr UNNEEDED, const bigsize_t val UNNEEDED)
 { fprintf(stderr, "towire_bigsize called!\n"); abort(); }
@@ -130,6 +136,9 @@ void towire_secp256k1_ecdsa_signature(u8 **pptr UNNEEDED,
 /* Generated stub for towire_sha256 */
 void towire_sha256(u8 **pptr UNNEEDED, const struct sha256 *sha256 UNNEEDED)
 { fprintf(stderr, "towire_sha256 called!\n"); abort(); }
+/* Generated stub for towire_tlv_payload */
+void towire_tlv_payload(u8 **pptr UNNEEDED, const struct tlv_payload *record UNNEEDED)
+{ fprintf(stderr, "towire_tlv_payload called!\n"); abort(); }
 /* Generated stub for towire_u16 */
 void towire_u16(u8 **pptr UNNEEDED, u16 v UNNEEDED)
 { fprintf(stderr, "towire_u16 called!\n"); abort(); }

lightningd/pay.c

@@ -1150,7 +1150,8 @@ send_payment(struct lightningd *ld,
 	     const char *description TAKES,
 	     const struct sha256 *local_invreq_id,
 	     const struct secret *payment_secret,
-	     const u8 *payment_metadata)
+	     const u8 *payment_metadata,
+	     bool dev_legacy_hop)
 {
 	unsigned int base_expiry;
 	struct onionpacket *packet;
@@ -1177,6 +1178,14 @@ send_payment(struct lightningd *ld,
 		ret = pubkey_from_node_id(&pubkey, &ids[i]);
 		assert(ret);
 
+		if (dev_legacy_hop && i == n_hops - 2) {
+			sphinx_add_v0_hop(path, &pubkey,
+					  &route[i + 1].scid,
+					  route[i + 1].amount,
+					  base_expiry + route[i + 1].delay);
+			continue;
+		}
+
 		sphinx_add_hop_has_length(path, &pubkey,
 			       take(onion_nonfinal_hop(NULL,
 					&route[i + 1].scid,
@@ -1506,6 +1515,7 @@ static struct command_result *json_sendpay(struct command *cmd,
 	struct secret *payment_secret;
 	struct sha256 *local_invreq_id;
 	u8 *payment_metadata;
+	bool *dev_legacy_hop;
 
 	if (!param_check(cmd, buffer, params,
 			 p_req("route", param_route_hops, &route),
@@ -1520,6 +1530,7 @@ static struct command_result *json_sendpay(struct command *cmd,
 			 p_opt("groupid", param_u64, &group),
 			 p_opt("payment_metadata", param_bin_from_hex, &payment_metadata),
 			 p_opt("description", param_string, &description),
+			 p_opt_dev("dev_legacy_hop", param_bool, &dev_legacy_hop, false),
 		   NULL))
 		return command_param_failed();
 
@@ -1582,7 +1593,7 @@ static struct command_result *json_sendpay(struct command *cmd,
 			    final_amount,
 			    msat ? *msat : final_amount,
 			    label, invstring, description, local_invreq_id,
-			    payment_secret, payment_metadata);
+			    payment_secret, payment_metadata, *dev_legacy_hop);
 }
 
 static const struct json_command sendpay_command = {

tests/test_pay.py

@@ -5661,3 +5661,31 @@ def test_pay_while_opening_channel(node_factory, bitcoind, executor):
     assert only_one(l1.rpc.listpeerchannels(l3.info['id'])['channels'])['state'] == 'OPENINGD'
     inv = l2.rpc.invoice(10000, "inv", "inv")
     l1.rpc.pay(inv['bolt11'])
+
+
+def test_pay_legacy_forward(node_factory, bitcoind, executor):
+    """We removed legacy in 22.11, and LND will still send them for
+    route hints!  See
+    https://github.com/lightningnetwork/lnd/issues/8785
+
+    """
+    l1, l2, l3 = node_factory.line_graph(3, fundamount=10**6, wait_for_announce=True)
+
+    inv = l3.rpc.invoice(1000, "inv", "inv")
+
+    chanid12 = only_one(l1.rpc.listpeerchannels(l2.info['id'])['channels'])['short_channel_id']
+    chanid23 = only_one(l2.rpc.listpeerchannels(l3.info['id'])['channels'])['short_channel_id']
+    route = [{'amount_msat': 1011,
+              'id': l2.info['id'],
+              'delay': 20,
+              'channel': chanid12},
+             {'amount_msat': 1000,
+              'id': l3.info['id'],
+              'delay': 10,
+              'channel': chanid23}]
+
+    l1.rpc.call("sendpay", payload={'route': route,
+                                    'payment_hash': inv['payment_hash'],
+                                    'payment_secret': inv['payment_secret'],
+                                    'dev_legacy_hop': True})
+    l1.rpc.waitsendpay(inv['payment_hash'])

wallet/test/run-wallet.c

@@ -932,6 +932,11 @@ u8 *serialize_onionpacket(
 bool sphinx_add_hop_has_length(struct sphinx_path *path UNNEEDED, const struct pubkey *pubkey UNNEEDED,
 			       const u8 *payload TAKES UNNEEDED)
 { fprintf(stderr, "sphinx_add_hop_has_length called!\n"); abort(); }
+/* Generated stub for sphinx_add_v0_hop */
+void sphinx_add_v0_hop(struct sphinx_path *path UNNEEDED, const struct pubkey *pubkey UNNEEDED,
+		       const struct short_channel_id *scid UNNEEDED,
+		       struct amount_msat forward UNNEEDED, u32 outgoing_cltv UNNEEDED)
+{ fprintf(stderr, "sphinx_add_v0_hop called!\n"); abort(); }
 /* Generated stub for sphinx_path_new */
 struct sphinx_path *sphinx_path_new(const tal_t *ctx UNNEEDED,
 				    const u8 *associated_data UNNEEDED)