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libhsmd: Migrate handle_sign_withdrawal_tx

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Christian Decker 2021-04-22 12:42:51 +02:00 committed by Rusty Russell
parent e7007a7f36
commit 9aa4b5198d
3 changed files with 122 additions and 161 deletions
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161
hsmd/hsmd.c
View File

@ -500,37 +500,6 @@ static void populate_secretstuff(void)
"Can't derive bolt12 keypair");
}
/*~ Get the keys for this given BIP32 index: if privkey is NULL, we
* don't fill it in. */
static void bitcoin_key(struct privkey *privkey, struct pubkey *pubkey,
u32 index)
{
struct ext_key ext;
struct privkey unused_priv;
if (privkey == NULL)
privkey = &unused_priv;
if (index >= BIP32_INITIAL_HARDENED_CHILD)
status_failed(STATUS_FAIL_MASTER_IO,
"Index %u too great", index);
/*~ This uses libwally, which doesn't dovetail directly with
* libsecp256k1 even though it, too, uses it internally. */
if (bip32_key_from_parent(&secretstuff.bip32, index,
BIP32_FLAG_KEY_PRIVATE, &ext) != WALLY_OK)
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"BIP32 of %u failed", index);
/* libwally says: The private key with prefix byte 0; remove it
* for libsecp256k1. */
memcpy(privkey->secret.data, ext.priv_key+1, 32);
if (!secp256k1_ec_pubkey_create(secp256k1_ctx, &pubkey->pubkey,
privkey->secret.data))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"BIP32 pubkey %u create failed", index);
}
/*~ This encrypts the content of the secretstuff and stores it in hsm_secret,
* this is called instead of create_hsm() if `lightningd` is started with
* --encrypted-hsm.
@ -1263,132 +1232,6 @@ static struct io_plan *pass_client_hsmfd(struct io_conn *conn,
send_pending_client_fd, c);
}
/*~ For almost every wallet tx we use the BIP32 seed, but not for onchain
* unilateral closes from a peer: they (may) have an output to us using a
* public key based on the channel basepoints. It's a bit spammy to spend
* those immediately just to make the wallet simpler, and we didn't appreciate
* the problem when we designed the protocol for commitment transaction keys.
*
* So we store just enough about the channel it came from (which may be
* long-gone) to regenerate the keys here. That has the added advantage that
* the secrets themselves stay within the HSM. */
static void hsm_unilateral_close_privkey(struct privkey *dst,
struct unilateral_close_info *info)
{
struct secret channel_seed;
struct basepoints basepoints;
struct secrets secrets;
get_channel_seed(&info->peer_id, info->channel_id, &channel_seed);
derive_basepoints(&channel_seed, NULL, &basepoints, &secrets, NULL);
/* BOLT #3:
*
* If `option_static_remotekey` or `option_anchor_outputs` is
* negotiated, the `remotepubkey` is simply the remote node's
* `payment_basepoint`, otherwise it is calculated as above using the
* remote node's `payment_basepoint`.
*/
/* In our UTXO representation, this is indicated by a NULL
* commitment_point. */
if (!info->commitment_point)
dst->secret = secrets.payment_basepoint_secret;
else if (!derive_simple_privkey(&secrets.payment_basepoint_secret,
&basepoints.payment,
info->commitment_point,
dst)) {
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Deriving unilateral_close_privkey");
}
}
/* This gets the bitcoin private key needed to spend from our wallet */
static void hsm_key_for_utxo(struct privkey *privkey, struct pubkey *pubkey,
const struct utxo *utxo)
{
if (utxo->close_info != NULL) {
/* This is a their_unilateral_close/to-us output, so
* we need to derive the secret the long way */
status_debug("Unilateral close output, deriving secrets");
hsm_unilateral_close_privkey(privkey, utxo->close_info);
pubkey_from_privkey(privkey, pubkey);
status_debug("Derived public key %s from unilateral close",
type_to_string(tmpctx, struct pubkey, pubkey));
} else {
/* Simple case: just get derive via HD-derivation */
bitcoin_key(privkey, pubkey, utxo->keyindex);
}
}
/* Find our inputs by the pubkey associated with the inputs, and
* add a partial sig for each */
static void sign_our_inputs(struct utxo **utxos, struct wally_psbt *psbt)
{
for (size_t i = 0; i < tal_count(utxos); i++) {
struct utxo *utxo = utxos[i];
for (size_t j = 0; j < psbt->num_inputs; j++) {
struct privkey privkey;
struct pubkey pubkey;
if (!wally_tx_input_spends(&psbt->tx->inputs[j],
&utxo->txid, utxo->outnum))
continue;
hsm_key_for_utxo(&privkey, &pubkey, utxo);
/* This line is basically the entire reason we have
* to iterate through to match the psbt input
* to the UTXO -- otherwise we would just
* call wally_psbt_sign for every utxo privkey
* and be done with it. We can't do that though
* because any UTXO that's derived from channel_info
* requires the HSM to find the pubkey, and we
* skip doing that until now as a bit of a reduction
* of complexity in the calling code */
psbt_input_add_pubkey(psbt, j, &pubkey);
/* It's actually a P2WSH in this case. */
if (utxo->close_info && utxo->close_info->option_anchor_outputs) {
const u8 *wscript = anchor_to_remote_redeem(tmpctx, &pubkey);
psbt_input_set_witscript(psbt, j, wscript);
psbt_input_set_wit_utxo(psbt, j,
scriptpubkey_p2wsh(psbt, wscript),
utxo->amount);
}
tal_wally_start();
if (wally_psbt_sign(psbt, privkey.secret.data,
sizeof(privkey.secret.data),
EC_FLAG_GRIND_R) != WALLY_OK)
status_broken("Received wally_err attempting to "
"sign utxo with key %s. PSBT: %s",
type_to_string(tmpctx, struct pubkey,
&pubkey),
type_to_string(tmpctx, struct wally_psbt,
psbt));
tal_wally_end(psbt);
}
}
}
/*~ lightningd asks us to sign a withdrawal; same as above but in theory
* we can do more to check the previous case is valid. */
static struct io_plan *handle_sign_withdrawal_tx(struct io_conn *conn,
struct client *c,
const u8 *msg_in)
{
struct utxo **utxos;
struct wally_psbt *psbt;
if (!fromwire_hsmd_sign_withdrawal(tmpctx, msg_in,
&utxos, &psbt))
return bad_req(conn, c, msg_in);
sign_our_inputs(utxos, psbt);
return req_reply(conn, c,
take(towire_hsmd_sign_withdrawal_reply(NULL, psbt)));
}
#if DEVELOPER
static struct io_plan *handle_memleak(struct io_conn *conn,
struct client *c,
@ -1485,9 +1328,6 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
case WIRE_HSMD_CLIENT_HSMFD:
return pass_client_hsmfd(conn, c, c->msg_in);
case WIRE_HSMD_SIGN_WITHDRAWAL:
return handle_sign_withdrawal_tx(conn, c, c->msg_in);
case WIRE_HSMD_SIGN_COMMITMENT_TX:
return handle_sign_commitment_tx(conn, c, c->msg_in);
@ -1513,6 +1353,7 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
return handle_sign_mutual_close_tx(conn, c, c->msg_in);
case WIRE_HSMD_GET_PER_COMMITMENT_POINT:
case WIRE_HSMD_SIGN_WITHDRAWAL:
case WIRE_HSMD_GET_CHANNEL_BASEPOINTS:
case WIRE_HSMD_SIGN_INVOICE:
case WIRE_HSMD_SIGN_MESSAGE:

120
hsmd/libhsmd.c
View File

@ -3,6 +3,7 @@
#include <common/bolt12_merkle.h>
#include <common/hash_u5.h>
#include <common/key_derive.h>
#include <common/type_to_string.h>
#include <hsmd/capabilities.h>
#include <hsmd/libhsmd.h>
#include <wire/peer_wire.h>
@ -300,6 +301,106 @@ static void hsm_unilateral_close_privkey(struct privkey *dst,
}
}
/*~ Get the keys for this given BIP32 index: if privkey is NULL, we
* don't fill it in. */
static void bitcoin_key(struct privkey *privkey, struct pubkey *pubkey,
u32 index)
{
struct ext_key ext;
struct privkey unused_priv;
if (privkey == NULL)
privkey = &unused_priv;
if (index >= BIP32_INITIAL_HARDENED_CHILD)
hsmd_status_failed(STATUS_FAIL_MASTER_IO, "Index %u too great",
index);
/*~ This uses libwally, which doesn't dovetail directly with
* libsecp256k1 even though it, too, uses it internally. */
if (bip32_key_from_parent(&secretstuff.bip32, index,
BIP32_FLAG_KEY_PRIVATE, &ext) != WALLY_OK)
hsmd_status_failed(STATUS_FAIL_INTERNAL_ERROR,
"BIP32 of %u failed", index);
/* libwally says: The private key with prefix byte 0; remove it
* for libsecp256k1. */
memcpy(privkey->secret.data, ext.priv_key+1, 32);
if (!secp256k1_ec_pubkey_create(secp256k1_ctx, &pubkey->pubkey,
privkey->secret.data))
hsmd_status_failed(STATUS_FAIL_INTERNAL_ERROR,
"BIP32 pubkey %u create failed", index);
}
/* This gets the bitcoin private key needed to spend from our wallet */
static void hsm_key_for_utxo(struct privkey *privkey, struct pubkey *pubkey,
const struct utxo *utxo)
{
if (utxo->close_info != NULL) {
/* This is a their_unilateral_close/to-us output, so
* we need to derive the secret the long way */
hsmd_status_debug("Unilateral close output, deriving secrets");
hsm_unilateral_close_privkey(privkey, utxo->close_info);
pubkey_from_privkey(privkey, pubkey);
hsmd_status_debug("Derived public key %s from unilateral close",
type_to_string(tmpctx, struct pubkey, pubkey));
} else {
/* Simple case: just get derive via HD-derivation */
bitcoin_key(privkey, pubkey, utxo->keyindex);
}
}
/* Find our inputs by the pubkey associated with the inputs, and
* add a partial sig for each */
static void sign_our_inputs(struct utxo **utxos, struct wally_psbt *psbt)
{
for (size_t i = 0; i < tal_count(utxos); i++) {
struct utxo *utxo = utxos[i];
for (size_t j = 0; j < psbt->num_inputs; j++) {
struct privkey privkey;
struct pubkey pubkey;
if (!wally_tx_input_spends(&psbt->tx->inputs[j],
&utxo->txid, utxo->outnum))
continue;
hsm_key_for_utxo(&privkey, &pubkey, utxo);
/* This line is basically the entire reason we have
* to iterate through to match the psbt input
* to the UTXO -- otherwise we would just
* call wally_psbt_sign for every utxo privkey
* and be done with it. We can't do that though
* because any UTXO that's derived from channel_info
* requires the HSM to find the pubkey, and we
* skip doing that until now as a bit of a reduction
* of complexity in the calling code */
psbt_input_add_pubkey(psbt, j, &pubkey);
/* It's actually a P2WSH in this case. */
if (utxo->close_info && utxo->close_info->option_anchor_outputs) {
const u8 *wscript = anchor_to_remote_redeem(tmpctx, &pubkey);
psbt_input_set_witscript(psbt, j, wscript);
psbt_input_set_wit_utxo(psbt, j,
scriptpubkey_p2wsh(psbt, wscript),
utxo->amount);
}
tal_wally_start();
if (wally_psbt_sign(psbt, privkey.secret.data,
sizeof(privkey.secret.data),
EC_FLAG_GRIND_R) != WALLY_OK)
hsmd_status_broken(
"Received wally_err attempting to "
"sign utxo with key %s. PSBT: %s",
type_to_string(tmpctx, struct pubkey,
&pubkey),
type_to_string(tmpctx, struct wally_psbt,
psbt));
tal_wally_end(psbt);
}
}
}
/*~ lightningd asks us to sign a message. I tweeted the spec
* in https://twitter.com/rusty_twit/status/1182102005914800128:
*
@ -761,6 +862,22 @@ static u8 *handle_get_per_commitment_point(struct hsmd_client *c, const u8 *msg_
NULL, &per_commitment_point, old_secret);
}
/*~ lightningd asks us to sign a withdrawal; same as above but in theory
* we can do more to check the previous case is valid. */
static u8 *handle_sign_withdrawal_tx(struct hsmd_client *c, const u8 *msg_in)
{
struct utxo **utxos;
struct wally_psbt *psbt;
if (!fromwire_hsmd_sign_withdrawal(tmpctx, msg_in,
&utxos, &psbt))
return hsmd_status_malformed_request(c, msg_in);
sign_our_inputs(utxos, psbt);
return towire_hsmd_sign_withdrawal_reply(NULL, psbt);
}
u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
const u8 *msg)
{
@ -787,7 +904,6 @@ u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
switch (t) {
case WIRE_HSMD_INIT:
case WIRE_HSMD_CLIENT_HSMFD:
case WIRE_HSMD_SIGN_WITHDRAWAL:
case WIRE_HSMD_SIGN_COMMITMENT_TX:
case WIRE_HSMD_SIGN_DELAYED_PAYMENT_TO_US:
case WIRE_HSMD_SIGN_REMOTE_HTLC_TO_US:
@ -821,6 +937,8 @@ u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
return handle_channel_update_sig(client, msg);
case WIRE_HSMD_GET_PER_COMMITMENT_POINT:
return handle_get_per_commitment_point(client, msg);
case WIRE_HSMD_SIGN_WITHDRAWAL:
return handle_sign_withdrawal_tx(client, msg);
case WIRE_HSMD_DEV_MEMLEAK:
case WIRE_HSMD_ECDH_RESP:

2
hsmd/libhsmd.h
View File

@ -70,6 +70,8 @@ void hsmd_status_fmt(enum log_level level,
#define hsmd_status_debug(...) \
hsmd_status_fmt(LOG_DBG, NULL, __VA_ARGS__)
#define hsmd_status_broken(...) \
hsmd_status_fmt(LOG_BROKEN, NULL, __VA_ARGS__)
void hsmd_status_failed(enum status_failreason code,
const char *fmt, ...) PRINTF_FMT(2,3);