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#include "watchtower.h"
#include <bitcoin/feerate.h>
#include <bitcoin/script.h>
#include <bitcoin/signature.h>
#include <bitcoin/tx.h>
#include <common/htlc_tx.h>
#include <common/key_derive.h>
#include <common/keyset.h>
#include <common/status.h>
#include <common/type_to_string.h>
#include <hsmd/gen_hsm_wire.h>
#include <wire/wire_sync.h>
static const u8 ONE = 0x1;
const struct bitcoin_tx *
penalty_tx_create(const tal_t *ctx,
const struct channel *channel,
u32 penalty_feerate,
u8 *final_scriptpubkey,
const struct secret *revocation_preimage,
const struct bitcoin_txid *commitment_txid,
s16 to_them_outnum, struct amount_sat to_them_sats,
int hsm_fd)
{
u8 *wscript;
struct bitcoin_tx *tx;
struct keyset keyset;
size_t weight;
u8 *msg;
struct amount_sat fee, min_out, amt;
struct bitcoin_signature sig;
u32 locktime = 0;
bool option_static_remotekey = channel->option_static_remotekey;
u8 **witness;
u32 remote_to_self_delay = channel->config[REMOTE].to_self_delay;
const struct amount_sat dust_limit = channel->config[LOCAL].dust_limit;
BUILD_ASSERT(sizeof(struct secret) == sizeof(*revocation_preimage));
const struct secret remote_per_commitment_secret = *revocation_preimage;
struct pubkey remote_per_commitment_point;
const struct basepoints *basepoints = channel->basepoints;
if (to_them_outnum == -1 ||
amount_sat_less_eq(to_them_sats, dust_limit)) {
status_debug(
"Cannot create penalty transaction because there "
"is no non-dust to_them output in the commitment.");
return NULL;
}
if (!pubkey_from_secret(&remote_per_commitment_secret, &remote_per_commitment_point))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Failed derive from per_commitment_secret %s",
type_to_string(tmpctx, struct secret,
&remote_per_commitment_secret));
if (!derive_keyset(&remote_per_commitment_point,
&basepoints[REMOTE],
&basepoints[LOCAL],
option_static_remotekey,
&keyset))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Failed deriving keyset");
wscript = bitcoin_wscript_to_local(tmpctx, remote_to_self_delay,
&keyset.self_revocation_key,
&keyset.self_delayed_payment_key);
tx = bitcoin_tx(ctx, chainparams, 1, 1, locktime);
bitcoin_tx_add_input(tx, commitment_txid, to_them_outnum, 0xFFFFFFFF,
NULL, to_them_sats, NULL, wscript);
bitcoin_tx_add_output(tx, final_scriptpubkey, NULL, to_them_sats);
/* Worst-case sig is 73 bytes */
weight = bitcoin_tx_weight(tx) + 1 + 3 + 73 + 0 + tal_count(wscript);
weight = elements_add_overhead(weight, 1, 1);
fee = amount_tx_fee(penalty_feerate, weight);
if (!amount_sat_add(&min_out, dust_limit, fee))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Cannot add dust_limit %s and fee %s",
type_to_string(tmpctx, struct amount_sat, &dust_limit),
type_to_string(tmpctx, struct amount_sat, &fee));
if (amount_sat_less(to_them_sats, min_out)) {
/* FIXME: We should use SIGHASH_NONE so others can take it */
fee = amount_tx_fee(feerate_floor(), weight);
}
/* This can only happen if feerate_floor() is still too high; shouldn't
* happen! */
if (!amount_sat_sub(&amt, to_them_sats, fee)) {
amt = dust_limit;
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"TX can't afford minimal feerate"
"; setting output to %s",
type_to_string(tmpctx, struct amount_sat, &amt));
}
bitcoin_tx_output_set_amount(tx, 0, amt);
bitcoin_tx_finalize(tx);
u8 *hsm_sign_msg =
towire_hsm_sign_penalty_to_us(ctx, &remote_per_commitment_secret,
tx, wscript);
if (!wire_sync_write(hsm_fd, take(hsm_sign_msg)))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Writing sign request to hsm");
msg = wire_sync_read(tmpctx, hsm_fd);
if (!msg || !fromwire_hsm_sign_tx_reply(msg, &sig))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Reading sign_tx_reply: %s", tal_hex(tmpctx, msg));
witness = bitcoin_witness_sig_and_element(tx, &sig, &ONE, sizeof(ONE),
wscript);
bitcoin_tx_input_set_witness(tx, 0, take(witness));
return tx;
}