core-lightning/lightningd/onion_message.c

#include "config.h"
#include <ccan/mem/mem.h>
#include <common/blindedpath.h>
#include <common/json_command.h>
#include <common/json_helpers.h>
#include <common/json_tok.h>
#include <common/param.h>
#include <common/type_to_string.h>
#include <gossipd/gossipd_wiregen.h>
#include <lightningd/channel.h>
#include <lightningd/json.h>
#include <lightningd/onion_message.h>
#include <lightningd/peer_control.h>
#include <lightningd/plugin_hook.h>
#include <lightningd/subd.h>
#include <sodium/randombytes.h>

struct onion_message_hook_payload {
	/* Optional */
	struct pubkey *reply_blinding;
	struct onionmsg_path **reply_path;
	struct pubkey *reply_first_node;
	struct pubkey *our_alias;

	/* Exactly one of these is set! */
	struct tlv_onionmsg_payload *om;
	struct tlv_obs2_onionmsg_payload *obs2_om;
};

static void json_add_blindedpath(struct json_stream *stream,
				 const char *fieldname,
				 const struct pubkey *blinding,
				 const struct pubkey *first_node_id,
				 struct onionmsg_path **path)
{
	json_object_start(stream, fieldname);
	json_add_pubkey(stream, "blinding", blinding);
	json_add_pubkey(stream, "first_node_id", first_node_id);
	json_array_start(stream, "hops");
	for (size_t i = 0; i < tal_count(path); i++) {
		json_object_start(stream, NULL);
		json_add_pubkey(stream, "id", &path[i]->node_id);
		json_add_hex_talarr(stream, "encrypted_recipient_data",
				    path[i]->encrypted_recipient_data);
		json_object_end(stream);
	};
	json_array_end(stream);
	json_object_end(stream);
}

static void onion_message_serialize(struct onion_message_hook_payload *payload,
				    struct json_stream *stream,
				    struct plugin *plugin)
{
	json_object_start(stream, "onion_message");
	if (payload->our_alias)
		json_add_pubkey(stream, "our_alias", payload->our_alias);

	if (payload->reply_first_node) {
		json_add_blindedpath(stream, "reply_blindedpath",
				     payload->reply_blinding,
				     payload->reply_first_node,
				     payload->reply_path);
	}

	/* Common convenience fields */
	if (payload->obs2_om) {
		json_add_bool(stream, "obs2", true);
		if (payload->obs2_om->invoice_request)
			json_add_hex_talarr(stream, "invoice_request",
					    payload->obs2_om->invoice_request);
		if (payload->obs2_om->invoice)
			json_add_hex_talarr(stream, "invoice", payload->obs2_om->invoice);

		if (payload->obs2_om->invoice_error)
			json_add_hex_talarr(stream, "invoice_error",
					    payload->obs2_om->invoice_error);

		json_array_start(stream, "unknown_fields");
		for (size_t i = 0; i < tal_count(payload->obs2_om->fields); i++) {
			if (payload->obs2_om->fields[i].meta)
				continue;
			json_object_start(stream, NULL);
			json_add_u64(stream, "number", payload->obs2_om->fields[i].numtype);
			json_add_hex(stream, "value",
				     payload->obs2_om->fields[i].value,
				     payload->obs2_om->fields[i].length);
			json_object_end(stream);
		}
		json_array_end(stream);
	} else {
		json_add_bool(stream, "obs2", false);
		if (payload->om->invoice_request)
			json_add_hex_talarr(stream, "invoice_request",
					    payload->om->invoice_request);
		if (payload->om->invoice)
			json_add_hex_talarr(stream, "invoice", payload->om->invoice);

		if (payload->om->invoice_error)
			json_add_hex_talarr(stream, "invoice_error",
					    payload->om->invoice_error);

		json_array_start(stream, "unknown_fields");
		for (size_t i = 0; i < tal_count(payload->om->fields); i++) {
			if (payload->om->fields[i].meta)
				continue;
			json_object_start(stream, NULL);
			json_add_u64(stream, "number", payload->om->fields[i].numtype);
			json_add_hex(stream, "value",
				     payload->om->fields[i].value,
				     payload->om->fields[i].length);
			json_object_end(stream);
		}
		json_array_end(stream);
	}
	json_object_end(stream);
}

static void
onion_message_hook_cb(struct onion_message_hook_payload *payload STEALS)
{
	/* plugin_hook_continue checks the "result"; anything other than continue
	 * just stops. */
	tal_free(payload);
}

/* Two hooks, because it's critical we only accept blinding if we expect that
 * exact blinding key.  Otherwise, we can be probed using old blinded paths. */
REGISTER_PLUGIN_HOOK(onion_message_blinded,
		     plugin_hook_continue,
		     onion_message_hook_cb,
		     onion_message_serialize,
		     struct onion_message_hook_payload *);

REGISTER_PLUGIN_HOOK(onion_message_ourpath,
		     plugin_hook_continue,
		     onion_message_hook_cb,
		     onion_message_serialize,
		     struct onion_message_hook_payload *);

void handle_onionmsg_to_us(struct lightningd *ld, const u8 *msg)
{
	struct onion_message_hook_payload *payload;
	u8 *submsg;
	struct secret *self_id;
	bool obs2;
	size_t submsglen;
	const u8 *subptr;

	payload = tal(tmpctx, struct onion_message_hook_payload);
	payload->our_alias = tal(payload, struct pubkey);

	if (!fromwire_gossipd_got_onionmsg_to_us(payload, msg,
						 &obs2,
						 payload->our_alias,
						 &self_id,
						 &payload->reply_blinding,
						 &payload->reply_first_node,
						 &payload->reply_path,
						 &submsg)) {
		log_broken(ld->log, "bad got_onionmsg_tous: %s",
			   tal_hex(tmpctx, msg));
		return;
	}

#if DEVELOPER
	if (!obs2 && ld->dev_ignore_modern_onion)
		return;
	if (obs2 && ld->dev_ignore_obsolete_onion)
		return;
#endif

	/* If there's no self_id, or it's not correct, ignore alias: alias
	 * means we created the path it's using. */
	if (!self_id || !secret_eq_consttime(self_id, &ld->onion_reply_secret))
		payload->our_alias = tal_free(payload->our_alias);
	tal_free(self_id);

	submsglen = tal_bytelen(submsg);
	subptr = submsg;
	if (obs2) {
		payload->om = NULL;
		payload->obs2_om = tlv_obs2_onionmsg_payload_new(payload);
		if (!fromwire_obs2_onionmsg_payload(&subptr,
						    &submsglen, payload->obs2_om)) {
			log_broken(ld->log, "bad got_onionmsg_tous obs2 om: %s",
				   tal_hex(tmpctx, msg));
			return;
		}
	} else {
		payload->obs2_om = NULL;
		payload->om = tlv_onionmsg_payload_new(payload);
		if (!fromwire_onionmsg_payload(&subptr, &submsglen, payload->om)) {
			log_broken(ld->log, "bad got_onionmsg_tous om: %s",
				   tal_hex(tmpctx, msg));
			return;
		}
	}
	tal_free(submsg);

	/* Make sure gossipd gets this right. */
	if (payload->reply_path
	    && (!payload->reply_blinding || !payload->reply_first_node)) {
		log_broken(ld->log,
			   "No reply blinding/first_node, ignoring reply path");
		payload->reply_path = tal_free(payload->reply_path);
	}

	log_debug(ld->log, "Got onionmsg%s%s",
		  payload->our_alias ? " via-ourpath": "",
		  payload->reply_path ? " reply_path": "");

	/* We'll free this on return */
	tal_steal(ld, payload);
	if (payload->our_alias)
		plugin_hook_call_onion_message_ourpath(ld, payload);
	else
		plugin_hook_call_onion_message_blinded(ld, payload);
}

struct onion_hop {
	struct pubkey node;
	u8 *tlv;
};

static struct command_result *param_onion_hops(struct command *cmd,
					       const char *name,
					       const char *buffer,
					       const jsmntok_t *tok,
					       struct onion_hop **hops)
{
	size_t i;
	const jsmntok_t *t;

	if (tok->type != JSMN_ARRAY || tok->size == 0)
		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
				    "%s must be an (non-empty) array", name);

	*hops = tal_arr(cmd, struct onion_hop, tok->size);
	json_for_each_arr(i, t, tok) {
		const char *err;

		err = json_scan(cmd, buffer, t, "{id:%,tlv:%}",
				JSON_SCAN(json_to_pubkey, &(*hops)[i].node),
				JSON_SCAN_TAL(tmpctx, json_tok_bin_from_hex,
					      &(*hops)[i].tlv));
		if (err)
			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
					    "%s[%zu]: %s", name, i, err);
	}
	return NULL;
}

static struct command_result *json_sendonionmessage2(struct command *cmd,
						     const char *buffer,
						     const jsmntok_t *obj UNNEEDED,
						     const jsmntok_t *params,
						     bool obs2)
{
	struct onion_hop *hops;
	struct node_id *first_id;
	struct pubkey *blinding;
	struct sphinx_path *sphinx_path;
	struct onionpacket *op;
	struct secret *path_secrets;
	size_t onion_size;

	if (!param(cmd, buffer, params,
		   p_req("first_id", param_node_id, &first_id),
		   p_req("blinding", param_pubkey, &blinding),
		   p_req("hops", param_onion_hops, &hops),
		   NULL))
		return command_param_failed();

	if (!feature_offered(cmd->ld->our_features->bits[NODE_ANNOUNCE_FEATURE],
			     OPT_ONION_MESSAGES))
		return command_fail(cmd, LIGHTNINGD,
				    "experimental-onion-messages not enabled");

	/* Sanity check first; gossipd doesn't bother telling us if peer
	 * can't be reached. */
	if (!peer_by_id(cmd->ld, first_id))
		return command_fail(cmd, LIGHTNINGD, "Unknown first peer");

	/* Create an onion which encodes this. */
	sphinx_path = sphinx_path_new(cmd, NULL);
	for (size_t i = 0; i < tal_count(hops); i++)
		sphinx_add_modern_hop(sphinx_path, &hops[i].node, hops[i].tlv);

	/* BOLT-onion-message #4:
	 * - SHOULD set `len` to 1366 or 32834.
	 */
	if (sphinx_path_payloads_size(sphinx_path) <= ROUTING_INFO_SIZE)
		onion_size = ROUTING_INFO_SIZE;
	else
		onion_size = 32768;

	op = create_onionpacket(tmpctx, sphinx_path, onion_size, &path_secrets);
	if (!op)
		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
				    "Creating onion failed (tlvs too long?)");

	subd_send_msg(cmd->ld->gossip,
		      take(towire_gossipd_send_onionmsg(NULL, obs2, first_id,
					serialize_onionpacket(tmpctx, op),
					blinding)));

	return command_success(cmd, json_stream_success(cmd));
}

static struct command_result *json_sendonionmessage(struct command *cmd,
						    const char *buffer,
						    const jsmntok_t *obj,
						    const jsmntok_t *params)
{
	return json_sendonionmessage2(cmd, buffer, obj, params, false);
}

static struct command_result *json_sendobs2onionmessage(struct command *cmd,
							const char *buffer,
							const jsmntok_t *obj,
							const jsmntok_t *params)
{
	return json_sendonionmessage2(cmd, buffer, obj, params, true);
}

static const struct json_command sendonionmessage_command = {
	"sendonionmessage",
	"utility",
	json_sendonionmessage,
	"Send message to {first_id}, using {blinding}, encoded over {hops} (id, tlv)"
};
AUTODATA(json_command, &sendonionmessage_command);

static const struct json_command sendobs2onionmessage_command = {
	"sendobs2onionmessage",
	"utility",
	json_sendobs2onionmessage,
	"Send obsolete message to {first_id}, using {blinding}, encoded over {hops} (id, tlv)"
};
AUTODATA(json_command, &sendobs2onionmessage_command);

static struct command_result *param_pubkeys(struct command *cmd,
					    const char *name,
					    const char *buffer,
					    const jsmntok_t *tok,
					    struct pubkey **pubkeys)
{
	size_t i;
	const jsmntok_t *t;

	if (tok->type != JSMN_ARRAY || tok->size == 0)
		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
				    "%s must be an (non-empty) array", name);

	*pubkeys = tal_arr(cmd, struct pubkey, tok->size);
	json_for_each_arr(i, t, tok) {
		if (!json_to_pubkey(buffer, t, &(*pubkeys)[i]))
			return command_fail_badparam(cmd, name, buffer, t,
						     "should be a compressed pubkey");
	}
	return NULL;
}

static struct command_result *json_blindedpath(struct command *cmd,
					       const char *buffer,
					       const jsmntok_t *obj UNNEEDED,
					       const jsmntok_t *params)
{
	struct pubkey *ids;
	struct onionmsg_path **path;
	struct privkey first_blinding, blinding_iter;
	struct pubkey first_blinding_pubkey, first_node, me;
	size_t nhops;
	struct json_stream *response;

	if (!param(cmd, buffer, params,
		   p_req("ids", param_pubkeys, &ids),
		   NULL))
		return command_param_failed();

	nhops = tal_count(ids);

	/* Final id should be us! */
	if (!pubkey_from_node_id(&me, &cmd->ld->id))
		fatal("My id %s is invalid?",
		      type_to_string(tmpctx, struct node_id, &cmd->ld->id));

	first_node = ids[0];
	if (!pubkey_eq(&ids[nhops-1], &me))
		return command_fail(cmd, LIGHTNINGD,
				    "Final of ids must be this node (%s), not %s",
				    type_to_string(tmpctx, struct pubkey, &me),
				    type_to_string(tmpctx, struct pubkey,
						   &ids[nhops-1]));

	randombytes_buf(&first_blinding, sizeof(first_blinding));
	if (!pubkey_from_privkey(&first_blinding, &first_blinding_pubkey))
		/* Should not happen! */
		return command_fail(cmd, LIGHTNINGD,
				    "Could not convert blinding to pubkey!");

	/* We convert ids into aliases as we go. */
	path = tal_arr(cmd, struct onionmsg_path *, nhops);

	blinding_iter = first_blinding;
	for (size_t i = 0; i < nhops - 1; i++) {
		path[i] = tal(path, struct onionmsg_path);
		path[i]->encrypted_recipient_data = create_enctlv(path[i],
						     &blinding_iter,
						     &ids[i],
						     &ids[i+1],
						     /* FIXME: Pad? */
						     0,
						     NULL,
						     &blinding_iter,
						     &path[i]->node_id);
	}

	/* FIXME: Add padding! */
	path[nhops-1] = tal(path, struct onionmsg_path);
	path[nhops-1]->encrypted_recipient_data = create_final_enctlv(path[nhops-1],
							 &blinding_iter,
							 &ids[nhops-1],
							 /* FIXME: Pad? */
							 0,
							 &cmd->ld->onion_reply_secret,
							 &path[nhops-1]->node_id);

	response = json_stream_success(cmd);
	json_add_blindedpath(response, "blindedpath",
			     &first_blinding_pubkey, &first_node, path);

	/* Now create obsolete one! */
	blinding_iter = first_blinding;
	for (size_t i = 0; i < nhops - 1; i++) {
		path[i] = tal(path, struct onionmsg_path);
		path[i]->encrypted_recipient_data = create_obs2_enctlv(path[i],
						     &blinding_iter,
						     &ids[i],
						     &ids[i+1],
						     /* FIXME: Pad? */
						     0,
						     NULL,
						     &blinding_iter,
						     &path[i]->node_id);
	}

	/* FIXME: Add padding! */
	path[nhops-1] = tal(path, struct onionmsg_path);
	path[nhops-1]->encrypted_recipient_data = create_obs2_final_enctlv(path[nhops-1],
							 &blinding_iter,
							 &ids[nhops-1],
							 /* FIXME: Pad? */
							 0,
							 &cmd->ld->onion_reply_secret,
							 &path[nhops-1]->node_id);
	json_add_blindedpath(response, "obs2blindedpath",
			     &first_blinding_pubkey, &first_node, path);
	return command_success(cmd, response);
}

static const struct json_command blindedpath_command = {
	"blindedpath",
	"utility",
	json_blindedpath,
	"Create blinded path to us along {ids} (pubkey array ending in our id)"
};
AUTODATA(json_command, &blindedpath_command);