core-lightning/connectd/onion_message.c

/*~ This contains all the code to handle onion messages. */
#include "config.h"
#include <ccan/cast/cast.h>
#include <ccan/tal/str/str.h>
#include <common/blindedpath.h>
#include <common/blinding.h>
#include <common/daemon_conn.h>
#include <common/ecdh_hsmd.h>
#include <common/features.h>
#include <common/onion_message_parse.h>
#include <common/sphinx.h>
#include <common/status.h>
#include <common/wire_error.h>
#include <connectd/connectd.h>
#include <connectd/connectd_wiregen.h>
#include <connectd/multiplex.h>
#include <connectd/onion_message.h>
#include <wire/peer_wire.h>

void onionmsg_req(struct daemon *daemon, const u8 *msg)
{
	struct node_id id;
	u8 *onionmsg;
	struct pubkey path_key;
	struct peer *peer;

	if (!fromwire_connectd_send_onionmsg(msg, msg, &id, &onionmsg, &path_key))
		master_badmsg(WIRE_CONNECTD_SEND_ONIONMSG, msg);

	/* Even though lightningd checks for valid ids, there's a race
	 * where it might vanish before we read this command. */
	peer = peer_htable_get(daemon->peers, &id);
	if (peer) {
		u8 *omsg = towire_onion_message(NULL, &path_key, onionmsg);
		inject_peer_msg(peer, take(omsg));
	}
}

static const char *handle_onion(const tal_t *ctx,
				struct daemon *daemon,
				const struct pubkey *path_key,
				const u8 *onion)
{
	u8 *next_onion_msg;
	struct sciddir_or_pubkey next_node;
	struct tlv_onionmsg_tlv *final_om;
	struct pubkey final_alias;
	struct secret *final_path_id;
	const char *err;

	err = onion_message_parse(tmpctx, onion, path_key,
				  &daemon->mykey,
				  &next_onion_msg, &next_node,
				  &final_om, &final_alias, &final_path_id);
	if (err) {
		return tal_steal(ctx, err);
	}

	if (final_om) {
		u8 *omsg;

		/* We re-marshall here by policy, before handing to lightningd */
		omsg = tal_arr(tmpctx, u8, 0);
		towire_tlvstream_raw(&omsg, final_om->fields);
		daemon_conn_send(daemon->master,
				 take(towire_connectd_got_onionmsg_to_us(NULL,
							final_path_id,
							final_om->reply_path,
							omsg)));
	} else {
		struct node_id next_node_id;
		struct peer *next_peer;

		assert(next_onion_msg);

		/* BOLT-offers #4:
		 * - if it is not the final node according to the onion encryption:
		 *...
		 *    - if `next_node_id` is present:
		 *      - the *next peer* is the peer with that node id.
		 *   - otherwise, if `short_channel_id` is present and corresponds to an announced short_channel_id or a local alias for a channel:
		 *      - the *next peer* is the peer at the other end of that channel.
		 *   - otherwise:
		 *      - MUST ignore the message.
		 *   - SHOULD forward the message using `onion_message` to the *next peer*.
		 */
		/* Since an alias is legal here, we can't simply lookup in gossmap. */
		if (!next_node.is_pubkey) {
			struct scid_to_node_id *scid_to_node_id;

			scid_to_node_id = scid_htable_get(daemon->scid_htable, next_node.scidd.scid);
			if (!scid_to_node_id) {
				return tal_fmt(ctx, "onion msg: unknown next scid %s",
					       fmt_short_channel_id(tmpctx, next_node.scidd.scid));
			}
			next_node_id = scid_to_node_id->node_id;
		} else {
			node_id_from_pubkey(&next_node_id, &next_node.pubkey);
		}

		next_peer = peer_htable_get(daemon->peers, &next_node_id);
		if (!next_peer) {
			return tal_fmt(ctx, "onion msg: unknown next peer %s",
				       fmt_sciddir_or_pubkey(tmpctx, &next_node));
		}
		inject_peer_msg(next_peer, take(next_onion_msg));
	}
	return NULL;
}


/* Peer sends an onion msg, or (if peer NULL) lightningd injects one. */
void handle_onion_message(struct daemon *daemon,
			  struct peer *peer, const u8 *msg)
{
	struct pubkey path_key;
	u8 *onion;
	u64 msec;
	struct timemono now = time_mono();

	/* Ignore unless explicitly turned on. */
	if (!feature_offered(daemon->our_features->bits[NODE_ANNOUNCE_FEATURE],
			     OPT_ONION_MESSAGES))
		return;

	/* Adjust tokens if they're entitled to more */
	msec = time_to_msec(timemono_between(now, peer->onionmsg_last_incoming));
	peer->onionmsg_incoming_tokens += msec;
	if (peer->onionmsg_incoming_tokens > ONION_MSG_TOKENS_MAX)
		peer->onionmsg_incoming_tokens = ONION_MSG_TOKENS_MAX;
	peer->onionmsg_last_incoming = now;

	/* No tokens left?  Limit it */
	if (peer->onionmsg_incoming_tokens < ONION_MSG_MSEC) {
		/* Warn once, for debugging */
		if (!peer->onionmsg_limit_warned) {
			inject_peer_msg(peer,
					take(towire_warningfmt(NULL, NULL,
							       "Ratelimited onion_message: exceeded one per %umsec",
							       ONION_MSG_MSEC)));
			peer->onionmsg_limit_warned = true;
		}
		return;
	}
	peer->onionmsg_incoming_tokens -= ONION_MSG_MSEC;

	if (!fromwire_onion_message(msg, msg, &path_key, &onion)) {
		inject_peer_msg(peer,
				take(towire_warningfmt(NULL, NULL,
						       "Bad onion_message")));
		return;
	}

	handle_onion(tmpctx, daemon, &path_key, onion);
}

void inject_onionmsg_req(struct daemon *daemon, const u8 *msg)
{
	u8 *onionmsg;
	struct pubkey path_key;
	const char *err;

	if (!fromwire_connectd_inject_onionmsg(msg, msg, &path_key, &onionmsg))
		master_badmsg(WIRE_CONNECTD_INJECT_ONIONMSG, msg);

	err = handle_onion(tmpctx, daemon, &path_key, onionmsg);
	daemon_conn_send(daemon->master,
			 take(towire_connectd_inject_onionmsg_reply(NULL, err ? err : "")));
}