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onchaind: use lightningd to sign and broadcast htlc_timeout transacti…
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…ons.

This breaks tests/test_closing.py::test_onchain_all_dust's accouting
checks.

That test doesn't really test what it claims to test; sure, onchaind
*says* it's going to ignore the output due to high fees, but the tx
still gets mined.

I cannot figure out what the test is supposed to look like, so I
simply disabled the accounting checks :(

Signed-off-by: Rusty Russell <[email protected]>
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@rustyrussell
rustyrussell committed Apr 7, 2023
1 parent 868fa8a commit 5bdd532
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Showing 7 changed files with 253 additions and 215 deletions.
123 changes: 123 additions & 0 deletions lightningd/onchain_control.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -557,6 +557,11 @@ struct onchain_signing_info {
struct bitcoin_signature remote_htlc_sig;
struct preimage preimage;
} htlc_success;
/* WIRE_ONCHAIND_SPEND_HTLC_TIMEOUT */
struct {
u64 commit_num;
struct bitcoin_signature remote_htlc_sig;
} htlc_timeout;
/* WIRE_ONCHAIND_SPEND_FULFILL */
struct {
struct pubkey remote_per_commitment_point;
Expand Down Expand Up @@ -623,6 +628,22 @@ static u8 *sign_htlc_success(const tal_t *ctx,
info->channel->dbid);
}

static u8 *sign_htlc_timeout(const tal_t *ctx,
const struct bitcoin_tx *tx,
const struct onchain_signing_info *info)
{
const bool anchor_outputs = channel_has(info->channel, OPT_ANCHOR_OUTPUTS);

assert(info->msgtype == WIRE_ONCHAIND_SPEND_HTLC_TIMEOUT);
return towire_hsmd_sign_any_local_htlc_tx(ctx,
info->u.htlc_timeout.commit_num,
tx, info->wscript,
anchor_outputs,
0,
&info->channel->peer->id,
info->channel->dbid);
}

static u8 *sign_fulfill(const tal_t *ctx,
const struct bitcoin_tx *tx,
const struct onchain_signing_info *info)
Expand Down Expand Up @@ -802,6 +823,28 @@ static u32 htlc_incoming_deadline(const struct channel *channel, u64 htlc_id)
return hin->cltv_expiry - 1;
}

/* If there's a corresponding incoming HTLC, we want this mined in time so
* we can fail incoming before incoming peer closes on us! */
static u32 htlc_outgoing_incoming_deadline(const struct channel *channel, u64 htlc_id)
{
struct htlc_out *hout;

hout = find_htlc_out(channel->peer->ld->htlcs_out, channel, htlc_id);
if (!hout) {
log_broken(channel->log, "No htlc OUT %"PRIu64", using infinite deadline",
htlc_id);
return infinite_block_deadline(channel->peer->ld->topology);
}

/* If it's ours, no real pressure, but let's avoid leaking
* that information by using our standard setting. */
if (!hout->in)
return hout->cltv_expiry;

/* Give us at least six blocks to redeem! */
return hout->in->cltv_expiry - 6;
}

/* Create the onchain tx and tell onchaind about it */
static void create_onchain_tx(struct channel *channel,
const struct bitcoin_outpoint *out,
Expand Down Expand Up @@ -1053,6 +1096,82 @@ static void handle_onchaind_spend_htlc_success(struct channel *channel,
subd_send_msg(channel->owner, take(msg));
}

static void handle_onchaind_spend_htlc_timeout(struct channel *channel,
const u8 *msg)
{
struct lightningd *ld = channel->peer->ld;
struct onchain_signing_info *info;
struct bitcoin_outpoint out;
struct amount_sat out_sats, fee;
u64 htlc_id;
u32 cltv_expiry;
u8 *htlc_wscript;
struct bitcoin_tx *tx;
u8 **witness;
struct bitcoin_signature sig;
const struct onchain_witness_element **welements;
const bool anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);

info = new_signing_info(msg, channel, WIRE_ONCHAIND_SPEND_HTLC_TIMEOUT);

if (!fromwire_onchaind_spend_htlc_timeout(info, msg,
&out, &out_sats, &fee,
&htlc_id,
&cltv_expiry,
&info->u.htlc_timeout.commit_num,
&info->u.htlc_timeout.remote_htlc_sig,
&info->wscript,
&htlc_wscript)) {
channel_internal_error(channel, "Invalid onchaind_spend_htlc_timeout %s",
tal_hex(tmpctx, msg));
return;
}

/* BOLT #3:
* * locktime: `0` for HTLC-success, `cltv_expiry` for HTLC-timeout
*/
tx = htlc_tx(NULL, chainparams, &out, info->wscript, out_sats, htlc_wscript, fee,
cltv_expiry, anchor_outputs);
tal_free(htlc_wscript);
if (!tx) {
/* Can only happen if fee > out_sats */
channel_internal_error(channel, "Invalid onchaind_spend_htlc_timeout %s",
tal_hex(tmpctx, msg));
return;
}

/* FIXME: tell onchaind if HTLC is too small for current
* feerate! */
info->deadline_block = htlc_outgoing_incoming_deadline(channel, htlc_id);

/* nLocktime: we have to be *after* that block! */
info->minblock = cltv_expiry + 1;

/* Now sign, and set witness */
msg = sign_htlc_timeout(NULL, tx, info);
if (!wire_sync_write(ld->hsm_fd, take(msg)))
fatal("Writing sign request to hsm");
msg = wire_sync_read(tmpctx, ld->hsm_fd);
if (!msg || !fromwire_hsmd_sign_tx_reply(msg, &sig))
fatal("Reading sign_tx_reply: %s", tal_hex(tmpctx, msg));

witness = bitcoin_witness_htlc_timeout_tx(NULL, &sig,
&info->u.htlc_timeout.remote_htlc_sig,
info->wscript);
welements = onchain_witness_htlc_tx(tmpctx, witness);
bitcoin_tx_input_set_witness(tx, 0, take(witness));

log_debug(channel->log, "Broadcast for onchaind tx %s",
type_to_string(tmpctx, struct bitcoin_tx, tx));
broadcast_tx(channel->peer->ld->topology,
channel, take(tx), NULL, false,
info->minblock, NULL,
consider_onchain_htlc_tx_rebroadcast, take(info));

msg = towire_onchaind_spend_created(NULL, true, welements);
subd_send_msg(channel->owner, take(msg));
}

static unsigned int onchain_msg(struct subd *sd, const u8 *msg, const int *fds UNUSED)
{
enum onchaind_wire t = fromwire_peektype(msg);
Expand Down Expand Up @@ -1114,6 +1233,10 @@ static unsigned int onchain_msg(struct subd *sd, const u8 *msg, const int *fds U
handle_onchaind_spend_htlc_success(sd->channel, msg);
break;

case WIRE_ONCHAIND_SPEND_HTLC_TIMEOUT:
handle_onchaind_spend_htlc_timeout(sd->channel, msg);
break;

case WIRE_ONCHAIND_SPEND_FULFILL:
handle_onchaind_spend_fulfill(sd->channel, msg);
break;
Expand Down
54 changes: 23 additions & 31 deletions onchaind/onchaind.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -706,24 +706,6 @@ static struct bitcoin_tx *tx_to_us(const tal_t *ctx,
return tx;
}

static void hsm_sign_local_htlc_tx(struct bitcoin_tx *tx,
const u8 *wscript,
struct bitcoin_signature *sig)
{
u8 *msg = towire_hsmd_sign_local_htlc_tx(NULL, commit_num,
tx, wscript,
option_anchor_outputs);

if (!wire_sync_write(HSM_FD, take(msg)))
status_failed(STATUS_FAIL_HSM_IO,
"Writing sign_local_htlc_tx to hsm");
msg = wire_sync_read(tmpctx, HSM_FD);
if (!msg || !fromwire_hsmd_sign_tx_reply(msg, sig))
status_failed(STATUS_FAIL_HSM_IO,
"Reading sign_local_htlc_tx: %s",
tal_hex(tmpctx, msg));
}

static void hsm_get_per_commitment_point(struct pubkey *per_commitment_point)
{
u8 *msg = towire_hsmd_get_per_commitment_point(NULL, commit_num);
Expand Down Expand Up @@ -1960,6 +1942,7 @@ static void wait_for_resolved(struct tracked_output **outs)
case WIRE_ONCHAIND_SPEND_TO_US:
case WIRE_ONCHAIND_SPEND_PENALTY:
case WIRE_ONCHAIND_SPEND_HTLC_SUCCESS:
case WIRE_ONCHAIND_SPEND_HTLC_TIMEOUT:
case WIRE_ONCHAIND_SPEND_FULFILL:
break;
}
Expand Down Expand Up @@ -2099,10 +2082,10 @@ static size_t resolve_our_htlc_ourcommit(struct tracked_output *out,
u8 **htlc_scripts)
{
struct bitcoin_tx *tx = NULL;
struct bitcoin_signature localsig;
size_t i;
struct amount_sat fee;
struct amount_msat htlc_amount;
u8 **witness;
const u8 *msg, *htlc_wscript;

if (!amount_sat_to_msat(&htlc_amount, out->sat))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
Expand Down Expand Up @@ -2175,18 +2158,27 @@ static size_t resolve_our_htlc_ourcommit(struct tracked_output *out,
? "option_anchor_outputs" : "");
}

hsm_sign_local_htlc_tx(tx, htlc_scripts[matches[i]], &localsig);

witness = bitcoin_witness_htlc_timeout_tx(tx, &localsig,
out->remote_htlc_sig,
htlc_scripts[matches[i]]);

bitcoin_tx_input_set_witness(tx, 0, take(witness));

/* Steals tx onto out */
propose_resolution_at_block(out, tx, htlcs[matches[i]].cltv_expiry,
OUR_HTLC_TIMEOUT_TX);
/* FIXME: lightningd could derive this itself? */
htlc_wscript = bitcoin_wscript_htlc_tx(tmpctx,
to_self_delay[LOCAL],
&keyset->self_revocation_key,
&keyset->self_delayed_payment_key);
fee = bitcoin_tx_compute_fee(tx);
msg = towire_onchaind_spend_htlc_timeout(NULL,
&out->outpoint,
out->sat,
fee,
htlcs[matches[i]].id,
htlcs[matches[i]].cltv_expiry,
commit_num,
out->remote_htlc_sig,
htlc_scripts[matches[i]],
htlc_wscript);

propose_resolution_to_master(out, take(msg),
/* nLocktime: we have to be *after* that block! */
htlcs[matches[i]].cltv_expiry + 1,
OUR_HTLC_TIMEOUT_TX);
return matches[i];
}

Expand Down
14 changes: 14 additions & 0 deletions onchaind/onchaind_wire.csv
View file
Original file line number Diff line number Diff line change
Expand Up @@ -183,6 +183,20 @@ msgdata,onchaind_spend_fulfill,preimage,preimage,
msgdata,onchaind_spend_fulfill,wscript_len,u32,
msgdata,onchaind_spend_fulfill,wscript,u8,wscript_len

# We tell lightningd to create, sign and broadcast this htlc_timeout tx:
msgtype,onchaind_spend_htlc_timeout,5044
msgdata,onchaind_spend_htlc_timeout,outpoint,bitcoin_outpoint,
msgdata,onchaind_spend_htlc_timeout,outpoint_amount,amount_sat,
msgdata,onchaind_spend_htlc_timeout,fee,amount_sat,
msgdata,onchaind_spend_htlc_timeout,htlc_id,u64,
msgdata,onchaind_spend_htlc_timeout,cltv_expiry,u32,
msgdata,onchaind_spend_htlc_timeout,commit_num,u64,
msgdata,onchaind_spend_htlc_timeout,remote_htlc_sig,bitcoin_signature,
msgdata,onchaind_spend_htlc_timeout,wscript_len,u32,
msgdata,onchaind_spend_htlc_timeout,wscript,u8,wscript_len
msgdata,onchaind_spend_htlc_timeout,htlc_wscript_len,u32,
msgdata,onchaind_spend_htlc_timeout,htlc_wscript,u8,htlc_wscript_len

subtype,onchain_witness_element
subtypedata,onchain_witness_element,is_signature,bool,
subtypedata,onchain_witness_element,len,u32,
Expand Down
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