mirrors/core-lightning
1
0
Fork 0
mirror of https://github.com/ElementsProject/lightning.git synced 2025-01-19 05:44:12 +01:00
Code Issues Projects Releases Wiki Activity

lightningd: handle first case of onchaind handing a tx to us to create.

Browse Source 
We add code for the case of spending a (timelocked) to-us output of an
HTLC output, so lightningd can do it (rather than onchaind doing all
the work itself).

onchaind still needs to know whether we bothered to create the tx
(fees might have caused it to evaporate, so it should consider it
immediately resolved rather than waiting for it), and what the
witnesses were, and which parts of the witnesses were signatures (as
these parts might change, with RBF or in future, combining other txs).

The inputs (known to onchaind) and the witnesses (told by lightningd)
uniquely identify the spend for the purposes of onchaind.  In
particular, they definitely distinguish HTLC-timeout and HTLC-success
cases.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2023-04-06 09:03:24 +09:30
parent 87264540c3
commit 956e6c4055
3 changed files with 301 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

278
lightningd/onchain_control.c
View File

@ -1,11 +1,15 @@
#include "config.h"
#include <bitcoin/feerate.h>
#include <bitcoin/script.h>
#include <ccan/cast/cast.h>
#include <ccan/tal/str/str.h>
#include <common/key_derive.h>
#include <common/psbt_keypath.h>
#include <common/type_to_string.h>
#include <db/exec.h>
#include <errno.h>
#include <hsmd/capabilities.h>
#include <hsmd/hsmd_wiregen.h>
#include <inttypes.h>
#include <lightningd/chaintopology.h>
#include <lightningd/channel.h>
@ -18,6 +22,7 @@
#include <onchaind/onchaind_wiregen.h>
#include <wallet/txfilter.h>
#include <wally_bip32.h>
#include <wire/wire_sync.h>
/* We dump all the known preimages when onchaind starts up. */
static void onchaind_tell_fulfill(struct channel *channel)
@ -518,6 +523,274 @@ static void onchain_annotate_txin(struct channel *channel, const u8 *msg)
channel->dbid);
}
/* All onchaind-produced txs are actually of the same form: */
struct onchain_signing_info {
/* Fields common to every callback: */
struct channel *channel;
/* Minimum block */
u32 minblock;
/* Block we want this mined by */
u32 deadline_block;
/* Witness script for tx */
u8 *wscript;
/* Trailing element for witness stack */
const tal_t *stack_elem;
/* Tagged union (for sanity checking!) */
enum onchaind_wire msgtype;
union {
/* WIRE_ONCHAIND_SPEND_HTLC_TIMEDOUT */
struct {
u64 commit_num;
} htlc_timedout;
} u;
};
/* If we don't care / don't know */
static u32 infinite_block_deadline(const struct chain_topology *topo)
{
return get_block_height(topo) + 300;
}
static struct onchain_signing_info *new_signing_info(const tal_t *ctx,
struct channel *channel,
enum onchaind_wire msgtype)
{
struct onchain_signing_info *info = tal(ctx, struct onchain_signing_info);
info->channel = channel;
info->msgtype = msgtype;
return info;
}
static u8 *sign_tx_to_us(const tal_t *ctx,
const struct bitcoin_tx *tx,
const struct onchain_signing_info *info)
{
assert(info->msgtype == WIRE_ONCHAIND_SPEND_TO_US);
return towire_hsmd_sign_any_delayed_payment_to_us(ctx,
info->u.htlc_timedout.commit_num,
tx, info->wscript,
0,
&info->channel->peer->id,
info->channel->dbid);
}
/* Matches bitcoin_witness_sig_and_element! */
static const struct onchain_witness_element **
onchain_witness_sig_and_element(const tal_t *ctx, u8 **witness)
{
struct onchain_witness_element **welements;
welements = tal_arr(ctx, struct onchain_witness_element *,
tal_count(witness));
for (size_t i = 0; i < tal_count(welements); i++) {
welements[i] = tal(welements, struct onchain_witness_element);
/* See bitcoin_witness_sig_and_element */
welements[i]->is_signature = (i == 0);
welements[i]->witness = tal_dup_talarr(welements[i], u8,
witness[i]);
}
return cast_const2(const struct onchain_witness_element **, welements);
}
/* Always sets *welements, returns tx. Sets *worthwhile to false if
* it wasn't worthwhile at the given feerate (and it had to drop feerate).
* Returns NULL iff it called channel_internal_error().
*/
static struct bitcoin_tx *onchaind_tx(const tal_t *ctx,
struct channel *channel,
const struct bitcoin_outpoint *out,
struct amount_sat out_sats,
u32 to_self_delay,
u32 locktime,
u32 feerate,
u8 *(*sign)(const tal_t *ctx,
const struct bitcoin_tx *tx,
const struct onchain_signing_info *info),
const struct onchain_signing_info *info,
bool *worthwhile,
const struct onchain_witness_element ***welements)
{
struct bitcoin_tx *tx;
struct amount_sat fee, min_out, amt;
struct bitcoin_signature sig;
size_t weight;
u8 *msg;
u8 **witness;
struct pubkey final_key;
struct ext_key final_wallet_ext_key;
struct lightningd *ld = channel->peer->ld;
bip32_pubkey(ld, &final_key, channel->final_key_idx);
if (bip32_key_from_parent(ld->bip32_base,
channel->final_key_idx,
BIP32_FLAG_KEY_PUBLIC,
&final_wallet_ext_key) != WALLY_OK) {
channel_internal_error(channel,
"Could not derive final_wallet_ext_key %"PRIu64,
channel->final_key_idx);
return NULL;
}
tx = bitcoin_tx(ctx, chainparams, 1, 1, locktime);
bitcoin_tx_add_input(tx, out, to_self_delay,
NULL, out_sats, NULL, info->wscript);
bitcoin_tx_add_output(
tx, scriptpubkey_p2wpkh(tmpctx, &final_key), NULL, out_sats);
psbt_add_keypath_to_last_output(tx, channel->final_key_idx, &final_wallet_ext_key);
/* Worst-case sig is 73 bytes */
weight = bitcoin_tx_weight(tx) + 1 + 3 + 73 + 0 + tal_count(info->wscript);
weight += elements_tx_overhead(chainparams, 1, 1);
fee = amount_tx_fee(feerate, weight);
/* Result is trivial? Spend with small feerate, but don't wait
* around for it as it might not confirm. */
if (!amount_sat_add(&min_out, channel->our_config.dust_limit, fee))
fatal("Cannot add dust_limit %s and fee %s",
type_to_string(tmpctx, struct amount_sat, &channel->our_config.dust_limit),
type_to_string(tmpctx, struct amount_sat, &fee));
if (amount_sat_less(out_sats, min_out)) {
/* FIXME: We should use SIGHASH_NONE so others can take it? */
fee = amount_tx_fee(feerate_floor(), weight);
*worthwhile = false;
} else
*worthwhile = true;
/* This can only happen if feerate_floor() is still too high; shouldn't
* happen! */
if (!amount_sat_sub(&amt, out_sats, fee)) {
amt = channel->our_config.dust_limit;
log_broken(channel->log, "TX can't afford minimal feerate"
"; setting output to %s",
type_to_string(tmpctx, struct amount_sat,
&amt));
*worthwhile = false;
}
bitcoin_tx_output_set_amount(tx, 0, amt);
bitcoin_tx_finalize(tx);
/* Now sign, and set witness */
msg = sign(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_sig_and_element(NULL, &sig, info->stack_elem,
tal_bytelen(info->stack_elem),
info->wscript);
*welements = onchain_witness_sig_and_element(ctx, witness);
bitcoin_tx_input_set_witness(tx, 0, take(witness));
return tx;
}
static bool consider_onchain_rebroadcast(struct channel *channel,
const struct bitcoin_tx **tx,
struct onchain_signing_info *info)
{
/* FIXME: Implement rbf! */
return true;
}
/* Create the onchain tx and tell onchaind about it */
static void create_onchain_tx(struct channel *channel,
const struct bitcoin_outpoint *out,
struct amount_sat out_sats,
u32 to_self_delay,
u32 locktime,
u32 initial_feerate,
u8 *(*sign)(const tal_t *ctx,
const struct bitcoin_tx *tx,
const struct onchain_signing_info *info),
struct onchain_signing_info *info STEALS,
const char *caller)
{
struct bitcoin_tx *tx;
const struct onchain_witness_element **welements;
bool worthwhile;
tx = onchaind_tx(tmpctx, channel,
out, out_sats, to_self_delay, locktime, initial_feerate,
sign, info, &worthwhile, &welements);
if (!tx)
return;
log_debug(channel->log, "Broadcast for onchaind tx %s%s",
type_to_string(tmpctx, struct bitcoin_tx, tx),
worthwhile ? "" : "(NOT WORTHWHILE, LOWBALL FEE!)");
broadcast_tx(channel->peer->ld->topology,
channel, take(tx), NULL, false, info->minblock,
NULL, consider_onchain_rebroadcast, take(info));
subd_send_msg(channel->owner,
take(towire_onchaind_spend_created(NULL,
worthwhile,
welements)));
}
static void handle_onchaind_spend_to_us(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;
u32 initial_feerate;
info = new_signing_info(msg, channel, WIRE_ONCHAIND_SPEND_TO_US);
/* BOLT #3:
* #### `to_local` Output
*...
* The output is spent by an input with `nSequence` field set to `to_self_delay` (which can only be valid after that duration has passed) and witness:
*
* <local_delayedsig> <>
*/
/* BOLT #3:
* ## HTLC-Timeout and HTLC-Success Transactions
*
* These HTLC transactions are almost identical, except the HTLC-timeout transaction is timelocked.
*...
* To spend this via penalty, the remote node uses a witness stack
* `<revocationsig> 1`, and to collect the output, the local node uses
* an input with nSequence `to_self_delay` and a witness stack
* `<local_delayedsig> 0`.
*/
info->stack_elem = NULL;
if (!fromwire_onchaind_spend_to_us(info, msg,
&out, &out_sats,
&info->minblock,
&info->u.htlc_timedout.commit_num,
&info->wscript)) {
channel_internal_error(channel, "Invalid onchaind_spend_to_us %s",
tal_hex(tmpctx, msg));
return;
}
/* FIXME: Be more sophisticated! */
initial_feerate = delayed_to_us_feerate(ld->topology);
if (!initial_feerate)
initial_feerate = tx_feerate(channel->last_tx);
/* No real deadline on this, it's just returning to our wallet. */
info->deadline_block = infinite_block_deadline(ld->topology);
create_onchain_tx(channel, &out, out_sats,
channel->channel_info.their_config.to_self_delay, 0,
initial_feerate, sign_tx_to_us, info,
__func__);
}
static unsigned int onchain_msg(struct subd *sd, const u8 *msg, const int *fds UNUSED)
{
enum onchaind_wire t = fromwire_peektype(msg);
@ -567,12 +840,17 @@ static unsigned int onchain_msg(struct subd *sd, const u8 *msg, const int *fds U
handle_onchain_log_coin_move(sd->channel, msg);
break;
case WIRE_ONCHAIND_SPEND_TO_US:
handle_onchaind_spend_to_us(sd->channel, msg);
break;
/* We send these, not receive them */
case WIRE_ONCHAIND_INIT:
case WIRE_ONCHAIND_SPENT:
case WIRE_ONCHAIND_DEPTH:
case WIRE_ONCHAIND_HTLCS:
case WIRE_ONCHAIND_KNOWN_PREIMAGE:
case WIRE_ONCHAIND_SPEND_CREATED:
case WIRE_ONCHAIND_DEV_MEMLEAK:
case WIRE_ONCHAIND_DEV_MEMLEAK_REPLY:
break;

2
onchaind/onchaind.c
View File

@ -2178,6 +2178,7 @@ static void wait_for_resolved(struct tracked_output **outs)
/* Unexpected messages */
case WIRE_ONCHAIND_INIT:
case WIRE_ONCHAIND_HTLCS:
case WIRE_ONCHAIND_SPEND_CREATED:
/* We send these, not receive! */
case WIRE_ONCHAIND_INIT_REPLY:
@ -2192,6 +2193,7 @@ static void wait_for_resolved(struct tracked_output **outs)
case WIRE_ONCHAIND_ANNOTATE_TXOUT:
case WIRE_ONCHAIND_ANNOTATE_TXIN:
case WIRE_ONCHAIND_NOTIFY_COIN_MVT:
case WIRE_ONCHAIND_SPEND_TO_US:
break;
}
master_badmsg(-1, msg);

21
onchaind/onchaind_wire.csv
View File

@ -139,3 +139,24 @@ msgdata,onchaind_annotate_txin,type,enum wallet_tx_type,
msgtype,onchaind_notify_coin_mvt,5037
msgdata,onchaind_notify_coin_mvt,mvt,chain_coin_mvt,
# We tell lightningd to create, sign and broadcast this tx:
msgtype,onchaind_spend_to_us,5040
msgdata,onchaind_spend_to_us,outpoint,bitcoin_outpoint,
msgdata,onchaind_spend_to_us,outpoint_amount,amount_sat,
msgdata,onchaind_spend_to_us,minblock,u32,
msgdata,onchaind_spend_to_us,commit_num,u64,
msgdata,onchaind_spend_to_us,wscript_len,u32,
msgdata,onchaind_spend_to_us,wscript,u8,wscript_len
subtype,onchain_witness_element
subtypedata,onchain_witness_element,is_signature,bool,
subtypedata,onchain_witness_element,len,u32,
subtypedata,onchain_witness_element,witness,u8,len
# lightningd replies; if it considers it uneconomic, it tells onchaind
# so it doesn't wait forever!
msgtype,onchaind_spend_created,5140
msgdata,onchaind_spend_created,expect_to_succeed,bool,
msgdata,onchaind_spend_created,num_witnesses,u32,
msgdata,onchaind_spend_created,witness,onchain_witness_element,num_witnesses

1 #include <bitcoin/tx_parts.h>
139 msgdata,onchaind_spend_created,expect_to_succeed,bool,
140 msgdata,onchaind_spend_created,num_witnesses,u32,
141 msgdata,onchaind_spend_created,witness,onchain_witness_element,num_witnesses
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162