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