/*~ Welcome to the opening daemon: gateway to channels! * * This daemon handles a single peer. It's happy to trade gossip with the * peer until either lightningd asks it to fund a channel, or the peer itself * asks to fund a channel. Then it goes through with the channel opening * negotiations. It's important to note that until this negotiation is complete, * there's nothing permanent about the channel: lightningd will only have to * commit to the database once openingd succeeds. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* stdin == lightningd, 3 == peer, 4 == gossipd, 5 = gossip_store, 6 = hsmd */ #define REQ_FD STDIN_FILENO #define HSM_FD 6 #if DEVELOPER /* If --dev-force-tmp-channel-id is set, it ends up here */ static struct channel_id *dev_force_tmp_channel_id; #endif /* DEVELOPER */ /* Global state structure. This is only for the one specific peer and channel */ struct state { struct per_peer_state *pps; /* Features they offered */ u8 *their_features; /* Constraints on a channel they open. */ u32 minimum_depth; u32 min_feerate, max_feerate; struct amount_msat min_effective_htlc_capacity; /* Limits on what remote config we accept. */ u32 max_to_self_delay; /* These are the points lightningd told us to use when accepting or * opening a channel. */ struct basepoints our_points; struct pubkey our_funding_pubkey; /* Information we need between funding_start and funding_complete */ struct basepoints their_points; struct pubkey their_funding_pubkey; /* hsmd gives us our first per-commitment point, and peer tells us * theirs */ struct pubkey first_per_commitment_point[NUM_SIDES]; /* Initially temporary, then final channel id. */ struct channel_id channel_id; /* Funding and feerate: set by opening peer. */ struct amount_sat funding; struct amount_msat push_msat; u32 feerate_per_kw; struct bitcoin_txid funding_txid; u16 funding_txout; /* If non-NULL, this is the scriptpubkey we/they *must* close with */ u8 *upfront_shutdown_script[NUM_SIDES]; /* This is a cluster of fields in open_channel and accept_channel which * indicate the restrictions each side places on the channel. */ struct channel_config localconf, remoteconf; /* The channel structure, as defined in common/initial_channel.h. While * the structure has room for HTLCs, those routines are channeld-specific * as initial channels never have HTLCs. */ struct channel *channel; bool option_static_remotekey; bool option_anchor_outputs; struct feature_set *our_features; }; /*~ If we can't agree on parameters, we fail to open the channel. If we're * the opener, we need to tell lightningd, otherwise it never really notices. */ static void negotiation_aborted(struct state *state, bool am_opener, const char *why) { status_debug("aborted opening negotiation: %s", why); /*~ The "billboard" (exposed as "status" in the JSON listpeers RPC * call) is a transient per-channel area which indicates important * information about what is happening. It has a "permanent" area for * each state, which can be used to indicate what went wrong in that * state (such as here), and a single transient area for current * status. */ peer_billboard(true, why); /* If necessary, tell master that funding failed. */ if (am_opener) { u8 *msg = towire_openingd_funder_failed(NULL, why); wire_sync_write(REQ_FD, take(msg)); } /* Default is no shutdown_scriptpubkey: free any leftover ones. */ state->upfront_shutdown_script[LOCAL] = tal_free(state->upfront_shutdown_script[LOCAL]); state->upfront_shutdown_script[REMOTE] = tal_free(state->upfront_shutdown_script[REMOTE]); /*~ Reset state. We keep gossipping with them, even though this open * failed. */ memset(&state->channel_id, 0, sizeof(state->channel_id)); state->channel = tal_free(state->channel); } /*~ For negotiation failures: we tell them the parameter we didn't like. */ static void negotiation_failed(struct state *state, bool am_opener, const char *fmt, ...) { va_list ap; const char *errmsg; u8 *msg; va_start(ap, fmt); errmsg = tal_vfmt(tmpctx, fmt, ap); va_end(ap); msg = towire_errorfmt(NULL, &state->channel_id, "You gave bad parameters: %s", errmsg); sync_crypto_write(state->pps, take(msg)); negotiation_aborted(state, am_opener, errmsg); } /* We always set channel_reserve_satoshis to 1%, rounded down. */ static void set_reserve(struct state *state, const struct amount_sat dust_limit) { state->localconf.channel_reserve = amount_sat_div(state->funding, 100); /* BOLT #2: * * The sending node: *... * - MUST set `channel_reserve_satoshis` greater than or equal to * `dust_limit_satoshis` from the `open_channel` message. */ if (amount_sat_greater(dust_limit, state->localconf.channel_reserve)) state->localconf.channel_reserve = dust_limit; } /*~ Handle random messages we might get during opening negotiation, (eg. gossip) * returning the first non-handled one, or NULL if we aborted negotiation. */ static u8 *opening_negotiate_msg(const tal_t *ctx, struct state *state, bool am_opener) { /* This is an event loop of its own. That's generally considered poor * form, but we use it in a very limited way. */ for (;;) { u8 *msg; bool from_gossipd; char *err; bool warning; struct channel_id actual; /* The event loop is responsible for freeing tmpctx, so our * temporary allocations don't grow unbounded. */ clean_tmpctx(); /* This helper routine polls both the peer and gossipd. */ msg = peer_or_gossip_sync_read(ctx, state->pps, &from_gossipd); /* Use standard helper for gossip msgs (forwards, if it's an * error, exits). */ if (from_gossipd) { handle_gossip_msg(state->pps, take(msg)); continue; } /* Some messages go straight to gossipd. */ if (is_msg_for_gossipd(msg)) { gossip_rcvd_filter_add(state->pps->grf, msg); wire_sync_write(state->pps->gossip_fd, take(msg)); continue; } /* BOLT #1: * * A receiving node: * - upon receiving a message of _odd_, unknown type: * - MUST ignore the received message. */ if (is_unknown_msg_discardable(msg)) continue; /* Might be a timestamp filter request: handle. */ if (handle_timestamp_filter(state->pps, msg)) continue; /* A helper which decodes an error. */ if (is_peer_error(tmpctx, msg, &state->channel_id, &err, &warning)) { /* BOLT #1: * * - if no existing channel is referred to by the * message: * - MUST ignore the message. */ /* In this case, is_peer_error returns true, but sets * err to NULL */ if (!err) { tal_free(msg); continue; } negotiation_aborted(state, am_opener, tal_fmt(tmpctx, "They sent %s", err)); /* Return NULL so caller knows to stop negotiating. */ return NULL; } /*~ We do not support multiple "live" channels, though the * protocol has a "channel_id" field in all non-gossip messages * so it's possible. Our one-process-one-channel mechanism * keeps things simple: if we wanted to change this, we would * probably be best with another daemon to de-multiplex them; * this could be connectd itself, in fact. */ if (is_wrong_channel(msg, &state->channel_id, &actual)) { status_debug("Rejecting %s for unknown channel_id %s", peer_wire_name(fromwire_peektype(msg)), type_to_string(tmpctx, struct channel_id, &actual)); sync_crypto_write(state->pps, take(towire_errorfmt(NULL, &actual, "Multiple channels" " unsupported"))); tal_free(msg); continue; } /* If we get here, it's an interesting message. */ return msg; } } static bool setup_channel_funder(struct state *state) { /*~ For symmetry, we calculate our own reserve even though lightningd * could do it for the we-are-funding case. */ set_reserve(state, state->localconf.dust_limit); /*~ Grab a random ID until the funding tx is created (we can't do that * until we know their funding_pubkey) */ temporary_channel_id(&state->channel_id); #if DEVELOPER /* --dev-force-tmp-channel-id specified */ if (dev_force_tmp_channel_id) state->channel_id = *dev_force_tmp_channel_id; #endif /* BOLT #2: * * The sending node: *... * - if both nodes advertised `option_support_large_channel`: * - MAY set `funding_satoshis` greater than or equal to 2^24 satoshi. * - otherwise: * - MUST set `funding_satoshis` to less than 2^24 satoshi. */ if (!feature_negotiated(state->our_features, state->their_features, OPT_LARGE_CHANNELS) && amount_sat_greater(state->funding, chainparams->max_funding)) { status_failed(STATUS_FAIL_MASTER_IO, "funding_satoshis must be < %s, not %s", type_to_string(tmpctx, struct amount_sat, &chainparams->max_funding), type_to_string(tmpctx, struct amount_sat, &state->funding)); return false; } return true; } static void set_remote_upfront_shutdown(struct state *state, u8 *shutdown_scriptpubkey STEALS) { bool anysegwit = feature_negotiated(state->our_features, state->their_features, OPT_SHUTDOWN_ANYSEGWIT); /* BOLT #2: * * - MUST include `upfront_shutdown_script` with either a valid * `shutdown_scriptpubkey` as required by `shutdown` `scriptpubkey`, * or a zero-length `shutdown_scriptpubkey` (ie. `0x0000`). */ /* We turn empty into NULL. */ if (tal_bytelen(shutdown_scriptpubkey) == 0) shutdown_scriptpubkey = tal_free(shutdown_scriptpubkey); state->upfront_shutdown_script[REMOTE] = tal_steal(state, shutdown_scriptpubkey); if (shutdown_scriptpubkey && !valid_shutdown_scriptpubkey(shutdown_scriptpubkey, anysegwit)) peer_failed_err(state->pps, &state->channel_id, "Unacceptable upfront_shutdown_script %s", tal_hex(tmpctx, shutdown_scriptpubkey)); } /* We start the 'open a channel' negotation with the supplied peer, but * stop when we get to the part where we need the funding txid */ static u8 *funder_channel_start(struct state *state, u8 channel_flags) { u8 *msg; u8 *funding_output_script; struct channel_id id_in; struct tlv_open_channel_tlvs *open_tlvs; struct tlv_accept_channel_tlvs *accept_tlvs; char *err_reason; if (!setup_channel_funder(state)) return NULL; if (!state->upfront_shutdown_script[LOCAL]) state->upfront_shutdown_script[LOCAL] = no_upfront_shutdown_script(state, state->our_features, state->their_features); open_tlvs = tlv_open_channel_tlvs_new(tmpctx); open_tlvs->upfront_shutdown_script = state->upfront_shutdown_script[LOCAL]; msg = towire_open_channel(NULL, &chainparams->genesis_blockhash, &state->channel_id, state->funding, state->push_msat, state->localconf.dust_limit, state->localconf.max_htlc_value_in_flight, state->localconf.channel_reserve, state->localconf.htlc_minimum, state->feerate_per_kw, state->localconf.to_self_delay, state->localconf.max_accepted_htlcs, &state->our_funding_pubkey, &state->our_points.revocation, &state->our_points.payment, &state->our_points.delayed_payment, &state->our_points.htlc, &state->first_per_commitment_point[LOCAL], channel_flags, open_tlvs); sync_crypto_write(state->pps, take(msg)); /* This is usually a very transient state... */ peer_billboard(false, "Funding channel start: offered, now waiting for accept_channel"); /* ... since their reply should be immediate. */ msg = opening_negotiate_msg(tmpctx, state, true); if (!msg) return NULL; /* BOLT #2: * * The receiving node MUST fail the channel if: *... * - `funding_pubkey`, `revocation_basepoint`, `htlc_basepoint`, * `payment_basepoint`, or `delayed_payment_basepoint` are not * valid secp256k1 pubkeys in compressed format. */ accept_tlvs = tlv_accept_channel_tlvs_new(tmpctx); if (!fromwire_accept_channel(msg, &id_in, &state->remoteconf.dust_limit, &state->remoteconf.max_htlc_value_in_flight, &state->remoteconf.channel_reserve, &state->remoteconf.htlc_minimum, &state->minimum_depth, &state->remoteconf.to_self_delay, &state->remoteconf.max_accepted_htlcs, &state->their_funding_pubkey, &state->their_points.revocation, &state->their_points.payment, &state->their_points.delayed_payment, &state->their_points.htlc, &state->first_per_commitment_point[REMOTE], accept_tlvs)) { peer_failed_err(state->pps, &state->channel_id, "Parsing accept_channel %s", tal_hex(msg, msg)); } set_remote_upfront_shutdown(state, accept_tlvs->upfront_shutdown_script); /* BOLT #2: * * The `temporary_channel_id` MUST be the same as the * `temporary_channel_id` in the `open_channel` message. */ if (!channel_id_eq(&id_in, &state->channel_id)) /* In this case we exit, since we don't know what's going on. */ peer_failed_err(state->pps, &id_in, "accept_channel ids don't match: sent %s got %s", type_to_string(msg, struct channel_id, &id_in), type_to_string(msg, struct channel_id, &state->channel_id)); if (amount_sat_greater(state->remoteconf.dust_limit, state->localconf.channel_reserve)) { negotiation_failed(state, true, "dust limit %s" " would be above our reserve %s", type_to_string(tmpctx, struct amount_sat, &state->remoteconf.dust_limit), type_to_string(tmpctx, struct amount_sat, &state->localconf.channel_reserve)); return NULL; } if (!check_config_bounds(tmpctx, state->funding, state->feerate_per_kw, state->max_to_self_delay, state->min_effective_htlc_capacity, &state->remoteconf, &state->localconf, true, state->option_anchor_outputs, &err_reason)) { negotiation_failed(state, true, "%s", err_reason); return NULL; } funding_output_script = scriptpubkey_p2wsh(tmpctx, bitcoin_redeem_2of2(tmpctx, &state->our_funding_pubkey, &state->their_funding_pubkey)); /* Update the billboard with our infos */ peer_billboard(false, "Funding channel start: awaiting funding_txid with output to %s", tal_hex(tmpctx, funding_output_script)); return towire_openingd_funder_start_reply(state, funding_output_script, feature_negotiated( state->our_features, state->their_features, OPT_UPFRONT_SHUTDOWN_SCRIPT)); } static bool funder_finalize_channel_setup(struct state *state, struct amount_msat local_msat, struct bitcoin_signature *sig, struct bitcoin_tx **tx, struct penalty_base **pbase) { u8 *msg; struct channel_id id_in; const u8 *wscript; struct channel_id cid; char *err_reason; struct wally_tx_output *direct_outputs[NUM_SIDES]; /*~ Now we can initialize the `struct channel`. This represents * the current channel state and is how we can generate the current * commitment transaction. * * The routines to support `struct channel` are split into a common * part (common/initial_channel) which doesn't support HTLCs and is * enough for us here, and the complete channel support required by * `channeld` which lives in channeld/full_channel. */ derive_channel_id(&cid, &state->funding_txid, state->funding_txout); state->channel = new_initial_channel(state, &cid, &state->funding_txid, state->funding_txout, state->minimum_depth, NULL, 0, /* No channel lease */ state->funding, local_msat, take(new_fee_states(NULL, LOCAL, &state->feerate_per_kw)), &state->localconf, &state->remoteconf, &state->our_points, &state->their_points, &state->our_funding_pubkey, &state->their_funding_pubkey, state->option_static_remotekey, state->option_anchor_outputs, /* Opener is local */ LOCAL); /* We were supposed to do enough checks above, but just in case, * new_initial_channel will fail to create absurd channels */ if (!state->channel) peer_failed_err(state->pps, &state->channel_id, "could not create channel with given config"); /* BOLT #2: * * ### The `funding_created` Message * * This message describes the outpoint which the funder has created * for the initial commitment transactions. After receiving the * peer's signature, via `funding_signed`, it will broadcast the funding * transaction. */ /* This gives us their first commitment transaction. */ *tx = initial_channel_tx(state, &wscript, state->channel, &state->first_per_commitment_point[REMOTE], REMOTE, direct_outputs, &err_reason); if (!*tx) { /* This should not happen: we should never create channels we * can't afford the fees for after reserve. */ negotiation_failed(state, true, "Could not meet their fees and reserve: %s", err_reason); goto fail; } if (direct_outputs[LOCAL]) *pbase = penalty_base_new(state, 0, *tx, direct_outputs[LOCAL]); else *pbase = NULL; /* We ask the HSM to sign their commitment transaction for us: it knows * our funding key, it just needs the remote funding key to create the * witness script. It also needs the amount of the funding output, * as segwit signatures commit to that as well, even though it doesn't * explicitly appear in the transaction itself. */ msg = towire_hsmd_sign_remote_commitment_tx(NULL, *tx, &state->channel->funding_pubkey[REMOTE], &state->first_per_commitment_point[REMOTE], state->channel->option_static_remotekey); wire_sync_write(HSM_FD, take(msg)); msg = wire_sync_read(tmpctx, HSM_FD); if (!fromwire_hsmd_sign_tx_reply(msg, sig)) status_failed(STATUS_FAIL_HSM_IO, "Bad sign_tx_reply %s", tal_hex(tmpctx, msg)); /* You can tell this has been a problem before, since there's a debug * message here: */ status_debug("signature %s on tx %s using key %s", type_to_string(tmpctx, struct bitcoin_signature, sig), type_to_string(tmpctx, struct bitcoin_tx, *tx), type_to_string(tmpctx, struct pubkey, &state->our_funding_pubkey)); /* Now we give our peer the signature for their first commitment * transaction. */ msg = towire_funding_created(state, &state->channel_id, &state->funding_txid, state->funding_txout, &sig->s); sync_crypto_write(state->pps, msg); /* BOLT #2: * * ### The `funding_signed` Message * * This message gives the funder the signature it needs for the first * commitment transaction, so it can broadcast the transaction knowing * that funds can be redeemed, if need be. */ peer_billboard(false, "Funding channel: create first tx, now waiting for their signature"); /* Now they send us their signature for that first commitment * transaction. */ msg = opening_negotiate_msg(tmpctx, state, true); if (!msg) goto fail; sig->sighash_type = SIGHASH_ALL; if (!fromwire_funding_signed(msg, &id_in, &sig->s)) peer_failed_err(state->pps, &state->channel_id, "Parsing funding_signed: %s", tal_hex(msg, msg)); /* BOLT #2: * * This message introduces the `channel_id` to identify the channel. * It's derived from the funding transaction by combining the * `funding_txid` and the `funding_output_index`, using big-endian * exclusive-OR (i.e. `funding_output_index` alters the last 2 * bytes). */ /*~ Back in Milan, we chose to allow multiple channels between peers in * the protocol. I insisted that we multiplex these over the same * socket, and (even though I didn't plan on implementing it anytime * soon) that we put it into the first version of the protocol * because it would be painful to add in later. * * My logic seemed sound: we treat new connections as an implication * that the old connection has disconnected, which happens more often * than you'd hope on modern networks. However, supporting multiple * channels via multiple connections would be far easier for us to * support with our (introduced-since) separate daemon model. * * Let this be a lesson: beware premature specification, even if you * suspect "we'll need it later!". */ state->channel_id = cid; if (!channel_id_eq(&id_in, &state->channel_id)) peer_failed_err(state->pps, &id_in, "funding_signed ids don't match: expected %s got %s", type_to_string(msg, struct channel_id, &state->channel_id), type_to_string(msg, struct channel_id, &id_in)); /* BOLT #2: * * The recipient: * - if `signature` is incorrect OR non-compliant with LOW-S-standard rule...: * - MUST fail the channel */ /* So we create *our* initial commitment transaction, and check the * signature they sent against that. */ *tx = initial_channel_tx(state, &wscript, state->channel, &state->first_per_commitment_point[LOCAL], LOCAL, direct_outputs, &err_reason); if (!*tx) { negotiation_failed(state, true, "Could not meet our fees and reserve: %s", err_reason); goto fail; } if (!check_tx_sig(*tx, 0, NULL, wscript, &state->their_funding_pubkey, sig)) { peer_failed_err(state->pps, &state->channel_id, "Bad signature %s on tx %s using key %s", type_to_string(tmpctx, struct bitcoin_signature, sig), type_to_string(tmpctx, struct bitcoin_tx, *tx), type_to_string(tmpctx, struct pubkey, &state->their_funding_pubkey)); } /* We save their sig to our first commitment tx */ if (!psbt_input_set_signature((*tx)->psbt, 0, &state->their_funding_pubkey, sig)) status_failed(STATUS_FAIL_INTERNAL_ERROR, "Unable to set signature internally"); peer_billboard(false, "Funding channel: opening negotiation succeeded"); return true; fail: tal_free(wscript); return false; } static u8 *funder_channel_complete(struct state *state) { /* Remote commitment tx */ struct bitcoin_tx *tx; struct bitcoin_signature sig; struct amount_msat local_msat; struct penalty_base *pbase; /* Update the billboard about what we're doing*/ peer_billboard(false, "Funding channel con't: continuing with funding_txid %s", type_to_string(tmpctx, struct bitcoin_txid, &state->funding_txid)); /* We recalculate the local_msat from cached values; should * succeed because we checked it earlier */ if (!amount_sat_sub_msat(&local_msat, state->funding, state->push_msat)) status_failed(STATUS_FAIL_INTERNAL_ERROR, "push_msat %s > funding %s?", type_to_string(tmpctx, struct amount_msat, &state->push_msat), type_to_string(tmpctx, struct amount_sat, &state->funding)); if (!funder_finalize_channel_setup(state, local_msat, &sig, &tx, &pbase)) return NULL; return towire_openingd_funder_reply(state, &state->remoteconf, tx, pbase, &sig, state->pps, &state->their_points.revocation, &state->their_points.payment, &state->their_points.htlc, &state->their_points.delayed_payment, &state->first_per_commitment_point[REMOTE], state->minimum_depth, &state->their_funding_pubkey, &state->funding_txid, state->funding_txout, state->feerate_per_kw, state->localconf.channel_reserve, state->upfront_shutdown_script[REMOTE]); } /*~ The peer sent us an `open_channel`, that means we're the fundee. */ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg) { struct channel_id id_in; struct basepoints theirs; struct pubkey their_funding_pubkey; struct bitcoin_signature theirsig, sig; struct bitcoin_tx *local_commit, *remote_commit; struct bitcoin_blkid chain_hash; u8 *msg; const u8 *wscript; u8 channel_flags; char* err_reason; struct wally_tx_output *direct_outputs[NUM_SIDES]; struct penalty_base *pbase; struct tlv_accept_channel_tlvs *accept_tlvs; struct tlv_open_channel_tlvs *open_tlvs = tlv_open_channel_tlvs_new(tmpctx); /* BOLT #2: * * The receiving node MUST fail the channel if: *... * - `funding_pubkey`, `revocation_basepoint`, `htlc_basepoint`, * `payment_basepoint`, or `delayed_payment_basepoint` are not valid * secp256k1 pubkeys in compressed format. */ if (!fromwire_open_channel(open_channel_msg, &chain_hash, &state->channel_id, &state->funding, &state->push_msat, &state->remoteconf.dust_limit, &state->remoteconf.max_htlc_value_in_flight, &state->remoteconf.channel_reserve, &state->remoteconf.htlc_minimum, &state->feerate_per_kw, &state->remoteconf.to_self_delay, &state->remoteconf.max_accepted_htlcs, &their_funding_pubkey, &theirs.revocation, &theirs.payment, &theirs.delayed_payment, &theirs.htlc, &state->first_per_commitment_point[REMOTE], &channel_flags, open_tlvs)) peer_failed_err(state->pps, &state->channel_id, "Parsing open_channel %s", tal_hex(tmpctx, open_channel_msg)); set_remote_upfront_shutdown(state, open_tlvs->upfront_shutdown_script); /* BOLT #2: * * The receiving node MUST fail the channel if: * - the `chain_hash` value is set to a hash of a chain * that is unknown to the receiver. */ if (!bitcoin_blkid_eq(&chain_hash, &chainparams->genesis_blockhash)) { negotiation_failed(state, false, "Unknown chain-hash %s", type_to_string(tmpctx, struct bitcoin_blkid, &chain_hash)); return NULL; } /* BOLT #2: * * The receiving node MUST fail the channel if: *... * - `funding_satoshis` is greater than or equal to 2^24 and the receiver does not support * `option_support_large_channel`. */ /* We choose to require *negotiation*, not just support! */ if (!feature_negotiated(state->our_features, state->their_features, OPT_LARGE_CHANNELS) && amount_sat_greater(state->funding, chainparams->max_funding)) { negotiation_failed(state, false, "funding_satoshis %s too large", type_to_string(tmpctx, struct amount_sat, &state->funding)); return NULL; } /* BOLT #2: * * The receiving node MUST fail the channel if: * ... * - `push_msat` is greater than `funding_satoshis` * 1000. */ if (amount_msat_greater_sat(state->push_msat, state->funding)) { peer_failed_err(state->pps, &state->channel_id, "Their push_msat %s" " would be too large for funding_satoshis %s", type_to_string(tmpctx, struct amount_msat, &state->push_msat), type_to_string(tmpctx, struct amount_sat, &state->funding)); return NULL; } /* BOLT #2: * * The receiving node MUST fail the channel if: *... * - it considers `feerate_per_kw` too small for timely processing or * unreasonably large. */ if (state->feerate_per_kw < state->min_feerate) { negotiation_failed(state, false, "feerate_per_kw %u below minimum %u", state->feerate_per_kw, state->min_feerate); return NULL; } if (state->feerate_per_kw > state->max_feerate) { negotiation_failed(state, false, "feerate_per_kw %u above maximum %u", state->feerate_per_kw, state->max_feerate); return NULL; } /* This reserves 1% of the channel (rounded up) */ set_reserve(state, state->remoteconf.dust_limit); /* BOLT #2: * * The sender: *... * - MUST set `channel_reserve_satoshis` greater than or equal to * `dust_limit_satoshis` from the `open_channel` message. * - MUST set `dust_limit_satoshis` less than or equal to * `channel_reserve_satoshis` from the `open_channel` message. */ if (amount_sat_greater(state->remoteconf.dust_limit, state->localconf.channel_reserve)) { negotiation_failed(state, false, "Our channel reserve %s" " would be below their dust %s", type_to_string(tmpctx, struct amount_sat, &state->localconf.channel_reserve), type_to_string(tmpctx, struct amount_sat, &state->remoteconf.dust_limit)); return NULL; } if (amount_sat_greater(state->localconf.dust_limit, state->remoteconf.channel_reserve)) { negotiation_failed(state, false, "Our dust limit %s" " would be above their reserve %s", type_to_string(tmpctx, struct amount_sat, &state->localconf.dust_limit), type_to_string(tmpctx, struct amount_sat, &state->remoteconf.channel_reserve)); return NULL; } /* These checks are the same whether we're opener or accepter... */ if (!check_config_bounds(tmpctx, state->funding, state->feerate_per_kw, state->max_to_self_delay, state->min_effective_htlc_capacity, &state->remoteconf, &state->localconf, false, state->option_anchor_outputs, &err_reason)) { negotiation_failed(state, false, "%s", err_reason); return NULL; } /* Check with lightningd that we can accept this? In particular, * if we have an existing channel, we don't support it. */ msg = towire_openingd_got_offer(NULL, state->funding, state->push_msat, state->remoteconf.dust_limit, state->remoteconf.max_htlc_value_in_flight, state->remoteconf.channel_reserve, state->remoteconf.htlc_minimum, state->feerate_per_kw, state->remoteconf.to_self_delay, state->remoteconf.max_accepted_htlcs, channel_flags, state->upfront_shutdown_script[REMOTE]); wire_sync_write(REQ_FD, take(msg)); msg = wire_sync_read(tmpctx, REQ_FD); /* We don't allocate off tmpctx, because that's freed inside * opening_negotiate_msg */ if (!fromwire_openingd_got_offer_reply(state, msg, &err_reason, &state->upfront_shutdown_script[LOCAL])) master_badmsg(WIRE_OPENINGD_GOT_OFFER_REPLY, msg); /* If they give us a reason to reject, do so. */ if (err_reason) { u8 *errmsg = towire_errorfmt(NULL, &state->channel_id, "%s", err_reason); sync_crypto_write(state->pps, take(errmsg)); tal_free(err_reason); return NULL; } if (!state->upfront_shutdown_script[LOCAL]) state->upfront_shutdown_script[LOCAL] = no_upfront_shutdown_script(state, state->our_features, state->their_features); /* OK, we accept! */ accept_tlvs = tlv_accept_channel_tlvs_new(tmpctx); accept_tlvs->upfront_shutdown_script = state->upfront_shutdown_script[LOCAL]; msg = towire_accept_channel(NULL, &state->channel_id, state->localconf.dust_limit, state->localconf.max_htlc_value_in_flight, state->localconf.channel_reserve, state->localconf.htlc_minimum, state->minimum_depth, state->localconf.to_self_delay, state->localconf.max_accepted_htlcs, &state->our_funding_pubkey, &state->our_points.revocation, &state->our_points.payment, &state->our_points.delayed_payment, &state->our_points.htlc, &state->first_per_commitment_point[LOCAL], accept_tlvs); sync_crypto_write(state->pps, take(msg)); peer_billboard(false, "Incoming channel: accepted, now waiting for them to create funding tx"); /* This is a loop which handles gossip until we get a non-gossip msg */ msg = opening_negotiate_msg(tmpctx, state, false); if (!msg) return NULL; /* The message should be "funding_created" which tells us what funding * tx they generated; the sighash type is implied, so we set it here. */ theirsig.sighash_type = SIGHASH_ALL; if (!fromwire_funding_created(msg, &id_in, &state->funding_txid, &state->funding_txout, &theirsig.s)) peer_failed_err(state->pps, &state->channel_id, "Parsing funding_created"); /* BOLT #2: * * The `temporary_channel_id` MUST be the same as the * `temporary_channel_id` in the `open_channel` message. */ if (!channel_id_eq(&id_in, &state->channel_id)) peer_failed_err(state->pps, &id_in, "funding_created ids don't match: sent %s got %s", type_to_string(msg, struct channel_id, &state->channel_id), type_to_string(msg, struct channel_id, &id_in)); /* Now we can create the channel structure. */ state->channel = new_initial_channel(state, &state->channel_id, &state->funding_txid, state->funding_txout, state->minimum_depth, NULL, 0, /* No channel lease */ state->funding, state->push_msat, take(new_fee_states(NULL, REMOTE, &state->feerate_per_kw)), &state->localconf, &state->remoteconf, &state->our_points, &theirs, &state->our_funding_pubkey, &their_funding_pubkey, state->option_static_remotekey, state->option_anchor_outputs, REMOTE); /* We don't expect this to fail, but it does do some additional * internal sanity checks. */ if (!state->channel) peer_failed_err(state->pps, &state->channel_id, "We could not create channel with given config"); /* BOLT #2: * * The recipient: * - if `signature` is incorrect OR non-compliant with LOW-S-standard * rule...: * - MUST fail the channel. */ local_commit = initial_channel_tx(state, &wscript, state->channel, &state->first_per_commitment_point[LOCAL], LOCAL, NULL, &err_reason); /* This shouldn't happen either, AFAICT. */ if (!local_commit) { negotiation_failed(state, false, "Could not meet our fees and reserve: %s", err_reason); return NULL; } if (!check_tx_sig(local_commit, 0, NULL, wscript, &their_funding_pubkey, &theirsig)) { /* BOLT #1: * * ### The `error` Message *... * - when failure was caused by an invalid signature check: * - SHOULD include the raw, hex-encoded transaction in reply * to a `funding_created`, `funding_signed`, * `closing_signed`, or `commitment_signed` message. */ /*~ This verbosity is not only useful for our own testing, but * a courtesy to other implementaters whose brains may be so * twisted by coding in Go, Scala and Rust that they can no * longer read C code. */ peer_failed_err(state->pps, &state->channel_id, "Bad signature %s on tx %s using key %s", type_to_string(tmpctx, struct bitcoin_signature, &theirsig), type_to_string(tmpctx, struct bitcoin_tx, local_commit), type_to_string(tmpctx, struct pubkey, &their_funding_pubkey)); } /* BOLT #2: * * This message introduces the `channel_id` to identify the * channel. It's derived from the funding transaction by combining the * `funding_txid` and the `funding_output_index`, using big-endian * exclusive-OR (i.e. `funding_output_index` alters the last 2 bytes). */ derive_channel_id(&state->channel_id, &state->funding_txid, state->funding_txout); /*~ We generate the `funding_signed` message here, since we have all * the data and it's only applicable in the fundee case. * * FIXME: Perhaps we should have channeld generate this, so we * can't possibly send before channel committed to disk? */ /* BOLT #2: * * ### The `funding_signed` Message * * This message gives the funder the signature it needs for the first * commitment transaction, so it can broadcast the transaction knowing * that funds can be redeemed, if need be. */ remote_commit = initial_channel_tx(state, &wscript, state->channel, &state->first_per_commitment_point[REMOTE], REMOTE, direct_outputs, &err_reason); if (!remote_commit) { negotiation_failed(state, false, "Could not meet their fees and reserve: %s", err_reason); return NULL; } /* Make HSM sign it */ msg = towire_hsmd_sign_remote_commitment_tx(NULL, remote_commit, &state->channel->funding_pubkey[REMOTE], &state->first_per_commitment_point[REMOTE], state->channel->option_static_remotekey); wire_sync_write(HSM_FD, take(msg)); msg = wire_sync_read(tmpctx, HSM_FD); if (!fromwire_hsmd_sign_tx_reply(msg, &sig)) status_failed(STATUS_FAIL_HSM_IO, "Bad sign_tx_reply %s", tal_hex(tmpctx, msg)); /* We don't send this ourselves: channeld does, because master needs * to save state to disk before doing so. */ assert(sig.sighash_type == SIGHASH_ALL); msg = towire_funding_signed(state, &state->channel_id, &sig.s); if (direct_outputs[LOCAL] != NULL) pbase = penalty_base_new(tmpctx, 0, remote_commit, direct_outputs[LOCAL]); else pbase = NULL; return towire_openingd_fundee(state, &state->remoteconf, local_commit, pbase, &theirsig, state->pps, &theirs.revocation, &theirs.payment, &theirs.htlc, &theirs.delayed_payment, &state->first_per_commitment_point[REMOTE], &their_funding_pubkey, &state->funding_txid, state->funding_txout, state->funding, state->push_msat, channel_flags, state->feerate_per_kw, msg, state->localconf.channel_reserve, state->upfront_shutdown_script[LOCAL], state->upfront_shutdown_script[REMOTE]); } /*~ Standard "peer sent a message, handle it" demuxer. Though it really only * handles one message, we use the standard form as principle of least * surprise. */ static u8 *handle_peer_in(struct state *state) { u8 *msg = sync_crypto_read(tmpctx, state->pps); enum peer_wire t = fromwire_peektype(msg); struct channel_id channel_id; bool extracted; if (t == WIRE_OPEN_CHANNEL) return fundee_channel(state, msg); /* Handle custommsgs */ enum peer_wire type = fromwire_peektype(msg); if (type % 2 == 1 && !peer_wire_is_defined(type)) { /* The message is not part of the messages we know how to * handle. Assuming this is a custommsg, we just forward it to the * master. */ wire_sync_write(REQ_FD, take(towire_custommsg_in(NULL, msg))); return NULL; } /* Handles standard cases, and legal unknown ones. */ if (handle_peer_gossip_or_error(state->pps, &state->channel_id, false, msg)) return NULL; extracted = extract_channel_id(msg, &channel_id); /* Reestablish on some now-closed channel? Be nice. */ if (extracted && fromwire_peektype(msg) == WIRE_CHANNEL_REESTABLISH) { return towire_openingd_got_reestablish(NULL, &channel_id, msg, state->pps); } sync_crypto_write(state->pps, take(towire_warningfmt(NULL, extracted ? &channel_id : NULL, "Unexpected message %s: %s", peer_wire_name(t), tal_hex(tmpctx, msg)))); /* FIXME: We don't actually want master to try to send an * error, since peer is transient. This is a hack. */ status_broken("Unexpected message %s", peer_wire_name(t)); peer_failed_connection_lost(); } /*~ If we see the gossip_fd readable, we read a whole message. Sure, we might * block, but we trust gossipd. */ static void handle_gossip_in(struct state *state) { u8 *msg = wire_sync_read(NULL, state->pps->gossip_fd); if (!msg) status_failed(STATUS_FAIL_GOSSIP_IO, "Reading gossip: %s", strerror(errno)); handle_gossip_msg(state->pps, take(msg)); } /* Memory leak detection is DEVELOPER-only because we go to great lengths to * record the backtrace when allocations occur: without that, the leak * detection tends to be useless for diagnosing where the leak came from, but * it has significant overhead. */ #if DEVELOPER static void handle_dev_memleak(struct state *state, const u8 *msg) { struct htable *memtable; bool found_leak; /* Populate a hash table with all our allocations (except msg, which * is in use right now). */ memtable = memleak_find_allocations(tmpctx, msg, msg); /* Now delete state and things it has pointers to. */ memleak_remove_region(memtable, state, sizeof(*state)); /* If there's anything left, dump it to logs, and return true. */ found_leak = dump_memleak(memtable); wire_sync_write(REQ_FD, take(towire_openingd_dev_memleak_reply(NULL, found_leak))); } #endif /* DEVELOPER */ /* We were told to send a custommsg to the peer by `lightningd`. All the * verification is done on the side of `lightningd` so we should be good to * just forward it here. */ static void openingd_send_custommsg(struct state *state, const u8 *msg) { u8 *inner; if (!fromwire_custommsg_out(tmpctx, msg, &inner)) master_badmsg(WIRE_CUSTOMMSG_OUT, msg); sync_crypto_write(state->pps, take(inner)); } /* Standard lightningd-fd-is-ready-to-read demux code. Again, we could hang * here, but if we can't trust our parent, who can we trust? */ static u8 *handle_master_in(struct state *state) { u8 *msg = wire_sync_read(tmpctx, REQ_FD); enum openingd_wire t = fromwire_peektype(msg); u8 channel_flags; struct bitcoin_txid funding_txid; u16 funding_txout; switch (t) { case WIRE_OPENINGD_FUNDER_START: if (!fromwire_openingd_funder_start(state, msg, &state->funding, &state->push_msat, &state->upfront_shutdown_script[LOCAL], &state->feerate_per_kw, &channel_flags)) master_badmsg(WIRE_OPENINGD_FUNDER_START, msg); msg = funder_channel_start(state, channel_flags); /* We want to keep openingd alive, since we're not done yet */ if (msg) wire_sync_write(REQ_FD, take(msg)); return NULL; case WIRE_OPENINGD_FUNDER_COMPLETE: if (!fromwire_openingd_funder_complete(msg, &funding_txid, &funding_txout)) master_badmsg(WIRE_OPENINGD_FUNDER_COMPLETE, msg); state->funding_txid = funding_txid; state->funding_txout = funding_txout; return funder_channel_complete(state); case WIRE_OPENINGD_FUNDER_CANCEL: /* We're aborting this, simple */ if (!fromwire_openingd_funder_cancel(msg)) master_badmsg(WIRE_OPENINGD_FUNDER_CANCEL, msg); msg = towire_errorfmt(NULL, &state->channel_id, "Channel open canceled by us"); sync_crypto_write(state->pps, take(msg)); negotiation_aborted(state, true, "Channel open canceled by RPC"); return NULL; case WIRE_OPENINGD_DEV_MEMLEAK: #if DEVELOPER handle_dev_memleak(state, msg); return NULL; #endif case WIRE_OPENINGD_DEV_MEMLEAK_REPLY: case WIRE_OPENINGD_INIT: case WIRE_OPENINGD_FUNDER_REPLY: case WIRE_OPENINGD_FUNDER_START_REPLY: case WIRE_OPENINGD_FUNDEE: case WIRE_OPENINGD_FUNDER_FAILED: case WIRE_OPENINGD_GOT_OFFER: case WIRE_OPENINGD_GOT_OFFER_REPLY: case WIRE_OPENINGD_GOT_REESTABLISH: break; } /* Now handle common messages. */ switch ((enum common_wire)t) { case WIRE_CUSTOMMSG_OUT: openingd_send_custommsg(state, msg); return NULL; /* We send these. */ case WIRE_CUSTOMMSG_IN: break; } status_failed(STATUS_FAIL_MASTER_IO, "Unknown msg %s", tal_hex(tmpctx, msg)); } static void try_read_gossip_store(struct state *state) { u8 *msg = gossip_store_next(tmpctx, state->pps); if (msg) sync_crypto_write(state->pps, take(msg)); } int main(int argc, char *argv[]) { setup_locale(); u8 *msg; struct pollfd pollfd[3]; struct state *state = tal(NULL, struct state); struct secret *none; struct channel_id *force_tmp_channel_id; subdaemon_setup(argc, argv); /*~ This makes status_failed, status_debug etc work synchronously by * writing to REQ_FD */ status_setup_sync(REQ_FD); /*~ The very first thing we read from lightningd is our init msg */ msg = wire_sync_read(tmpctx, REQ_FD); if (!fromwire_openingd_init(state, msg, &chainparams, &state->our_features, &state->localconf, &state->max_to_self_delay, &state->min_effective_htlc_capacity, &state->pps, &state->our_points, &state->our_funding_pubkey, &state->minimum_depth, &state->min_feerate, &state->max_feerate, &state->their_features, &state->option_static_remotekey, &state->option_anchor_outputs, &force_tmp_channel_id, &dev_fast_gossip)) master_badmsg(WIRE_OPENINGD_INIT, msg); #if DEVELOPER dev_force_tmp_channel_id = force_tmp_channel_id; #endif /* 3 == peer, 4 == gossipd, 5 = gossip_store, 6 = hsmd */ per_peer_state_set_fds(state->pps, 3, 4, 5); /*~ Initially we're not associated with a channel, but * handle_peer_gossip_or_error compares this. */ memset(&state->channel_id, 0, sizeof(state->channel_id)); state->channel = NULL; /*~ We set these to NULL, meaning no requirements on shutdown */ state->upfront_shutdown_script[LOCAL] = state->upfront_shutdown_script[REMOTE] = NULL; /*~ We need an initial per-commitment point whether we're funding or * they are, and lightningd has reserved a unique dbid for us already, * so we might as well get the hsm daemon to generate it now. */ wire_sync_write(HSM_FD, take(towire_hsmd_get_per_commitment_point(NULL, 0))); msg = wire_sync_read(tmpctx, HSM_FD); if (!fromwire_hsmd_get_per_commitment_point_reply(tmpctx, msg, &state->first_per_commitment_point[LOCAL], &none)) status_failed(STATUS_FAIL_HSM_IO, "Bad get_per_commitment_point_reply %s", tal_hex(tmpctx, msg)); /*~ The HSM gives us the N-2'th per-commitment secret when we get the * N'th per-commitment point. But since N=0, it won't give us one. */ assert(none == NULL); /*~ Turns out this is useful for testing, to make sure we're ready. */ status_debug("Handed peer, entering loop"); /*~ We manually run a little poll() loop here. With only three fds */ pollfd[0].fd = REQ_FD; pollfd[0].events = POLLIN; pollfd[1].fd = state->pps->gossip_fd; pollfd[1].events = POLLIN; pollfd[2].fd = state->pps->peer_fd; pollfd[2].events = POLLIN; /* We exit when we get a conclusion to write to lightningd: either * opening_funder_reply or opening_fundee. */ msg = NULL; while (!msg) { int t; struct timerel trel; if (time_to_next_gossip(state->pps, &trel)) t = time_to_msec(trel); else t = -1; /*~ If we get a signal which aborts the poll() call, valgrind * complains about revents being uninitialized. I'm not sure * that's correct, but it's easy to be sure. */ pollfd[0].revents = pollfd[1].revents = pollfd[2].revents = 0; poll(pollfd, ARRAY_SIZE(pollfd), t); /* Subtle: handle_master_in can do its own poll loop, so * don't try to service more than one fd per loop. */ /* First priority: messages from lightningd. */ if (pollfd[0].revents & POLLIN) msg = handle_master_in(state); /* Second priority: messages from peer. */ else if (pollfd[2].revents & POLLIN) msg = handle_peer_in(state); /* Last priority: chit-chat from gossipd. */ else if (pollfd[1].revents & POLLIN) handle_gossip_in(state); else try_read_gossip_store(state); /* Since we're the top-level event loop, we clean up */ clean_tmpctx(); } /*~ Write message and hand back the peer fd and gossipd fd. This also * means that if the peer or gossipd wrote us any messages we didn't * read yet, it will simply be read by the next daemon. */ wire_sync_write(REQ_FD, msg); per_peer_state_fdpass_send(REQ_FD, state->pps); status_debug("Sent %s with fds", openingd_wire_name(fromwire_peektype(msg))); /* This frees the entire tal tree. */ tal_free(state); /* This frees up everything else. */ daemon_shutdown(); return 0; } /*~ Note that there are no other source files in openingd: it really is a fairly * straight-line daemon. * * From here the channel is established: lightningd hands the peer off to * channeld/channeld.c which runs the normal channel routine for this peer. */