common/sphinx: add realm flag so we can avoid legacy parsing.

For messages, we use the onion but payload lengths 0 and 1 aren't special.
Create a flag to disable that logic.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/onion.c

@@ -143,6 +143,7 @@ u8 *onion_final_hop(const tal_t *ctx,
 /* Returns true if valid, and fills in type. */
 static bool pull_payload_length(const u8 **cursor,
 				size_t *max,
+				bool has_realm,
 				enum onion_payload_type *type,
 				size_t *len)
 {
@@ -163,7 +164,7 @@ static bool pull_payload_length(const u8 **cursor,
 	 *   length. In this case the `hop_payload_length` is defined to be 32
 	 *   bytes.
 	 */
-	if (*len == 0) {
+	if (has_realm && *len == 0) {
 		if (type)
 			*type = ONION_V0_PAYLOAD;
 		assert(*cursor - start == 1);
@@ -176,10 +177,15 @@ static bool pull_payload_length(const u8 **cursor,
 	 *   case the `hop_payload_length` is equal to the numeric value of
 	 *   `length`.
 	 */
-	if (*len > 1) {
+	if (!has_realm || *len > 1) {
 		/* It's still invalid if it claims to be too long! */
-		if (*len > ROUTING_INFO_SIZE - HMAC_SIZE)
+		if (has_realm) {
-			return false;
+			if (*len > ROUTING_INFO_SIZE - HMAC_SIZE)
+				return false;
+		} else {
+			if (*len > *max)
+				return false;
+		}
 
 		if (type)
 			*type = ONION_TLV_PAYLOAD;
@@ -190,12 +196,12 @@ static bool pull_payload_length(const u8 **cursor,
 	return false;
 }
 
-size_t onion_payload_length(const u8 *raw_payload, size_t len,
+size_t onion_payload_length(const u8 *raw_payload, size_t len, bool has_realm,
 			    bool *valid,
 			    enum onion_payload_type *type)
 {
 	size_t max = len, payload_len;
-	*valid = pull_payload_length(&raw_payload, &max, type, &payload_len);
+	*valid = pull_payload_length(&raw_payload, &max, has_realm, type, &payload_len);
 
 	/* If it's not valid, copy the entire thing. */
 	if (!*valid)
@@ -214,7 +220,7 @@ struct onion_payload *onion_decode(const tal_t *ctx,
 	size_t max = tal_bytelen(cursor), len;
 	struct tlv_tlv_payload *tlv;
 
-	if (!pull_payload_length(&cursor, &max, &p->type, &len))
+	if (!pull_payload_length(&cursor, &max, true, &p->type, &len))
 		return tal_free(p);
 
 	switch (p->type) {

common/onion.h

@@ -39,6 +39,7 @@ u8 *onion_final_hop(const tal_t *ctx,
  * onion_payload_length: measure payload length in decrypted onion.
  * @raw_payload: payload to look at.
  * @len: length of @raw_payload in bytes.
+ * @has_realm: used for HTLCs, where first byte 0 is magical.
  * @valid: set to true if it is valid, false otherwise.
  * @type: if non-NULL, set to type of payload if *@valid is true.
  *
@@ -47,6 +48,7 @@ u8 *onion_final_hop(const tal_t *ctx,
  * the return value is @len (i.e. the entire payload).
  */
 size_t onion_payload_length(const u8 *raw_payload, size_t len,
+			    bool has_realm,
 			    bool *valid,
 			    enum onion_payload_type *type);
 

common/sphinx.c

@@ -563,7 +563,8 @@ struct route_step *process_onionpacket(
 	const struct onionpacket *msg,
 	const struct secret *shared_secret,
 	const u8 *assocdata,
-	const size_t assocdatalen
+	const size_t assocdatalen,
+	bool has_realm
 	)
 {
 	struct route_step *step = talz(ctx, struct route_step);
@@ -596,7 +597,7 @@ struct route_step *process_onionpacket(
 	if (!blind_group_element(&step->next->ephemeralkey, &msg->ephemeralkey, blind))
 		return tal_free(step);
 
-	payload_size = onion_payload_length(paddedheader, ROUTING_INFO_SIZE,
+	payload_size = onion_payload_length(paddedheader, ROUTING_INFO_SIZE, has_realm,
 					    &valid, NULL);
 
 	/* Can't decode?  Treat it as terminal. */

common/sphinx.h

@@ -133,13 +133,15 @@ bool onion_shared_secret(
  * @hoppayload: the per-hop payload destined for the processing node.
  * @assocdata: associated data to commit to in HMACs
  * @assocdatalen: length of the assocdata
+ * @has_realm: used for HTLCs, where first byte 0 is magical.
  */
 struct route_step *process_onionpacket(
 	const tal_t * ctx,
 	const struct onionpacket *packet,
 	const struct secret *shared_secret,
 	const u8 *assocdata,
-	const size_t assocdatalen
+	const size_t assocdatalen,
+	bool has_realm
 	);
 
 /**

devtools/onion.c

@@ -128,7 +128,7 @@ static struct route_step *decode_with_privkey(const tal_t *ctx, const u8 *onion,
 		errx(1, "Error creating shared secret.");
 
 	step = process_onionpacket(ctx, &packet, &shared_secret, assocdata,
-				   tal_bytelen(assocdata));
+				   tal_bytelen(assocdata), true);
 	return step;
 
 }
@@ -282,7 +282,7 @@ static void runtest(const char *filename)
 			errx(1, "Error serializing message.");
 		onion_payload_length(step->raw_payload,
 				     tal_bytelen(step->raw_payload),
-				     &valid, &type);
+				     true, &valid, &type);
 		assert(valid);
 		printf("  Type: %d\n", type);
 		printf("  Payload: %s\n", tal_hex(ctx, step->raw_payload));

lightningd/peer_htlcs.c

@@ -1108,7 +1108,7 @@ static bool peer_accepted_htlc(const tal_t *ctx,
 
 	rs = process_onionpacket(tmpctx, &op, hin->shared_secret,
 				 hin->payment_hash.u.u8,
-				 sizeof(hin->payment_hash));
+				 sizeof(hin->payment_hash), true);
 	if (!rs) {
 		*badonion = WIRE_INVALID_ONION_HMAC;
 		log_debug(channel->log,

wallet/test/run-wallet.c

@@ -550,7 +550,8 @@ struct route_step *process_onionpacket(
 	const struct onionpacket *packet UNNEEDED,
 	const struct secret *shared_secret UNNEEDED,
 	const u8 *assocdata UNNEEDED,
-	const size_t assocdatalen
+	const size_t assocdatalen UNNEEDED,
+	bool has_realm
 	)
 { fprintf(stderr, "process_onionpacket called!\n"); abort(); }
 /* Generated stub for serialize_onionpacket */