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hsm: Implement private key derivation needed for unilateral closes

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Signed-off-by: Christian Decker <decker.christian@gmail.com>
This commit is contained in:
Christian Decker
2018-01-02 16:34:08 +01:00
parent 3db4474465
commit 539c1485f2
2 changed files with 72 additions and 7 deletions
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1
hsmd/Makefile
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@@ -23,6 +23,7 @@ HSMD_COMMON_OBJS := \
common/bip32.o \
common/daemon_conn.o \
common/debug.o \
common/derive_basepoints.o \
common/funding_tx.o \
common/hash_u5.o \
common/io_debug.o \

78
hsmd/hsm.c
View File

@@ -15,9 +15,11 @@
#include <ccan/take/take.h>
#include <common/daemon_conn.h>
#include <common/debug.h>
#include <common/derive_basepoints.h>
#include <common/funding_tx.h>
#include <common/hash_u5.h>
#include <common/io_debug.h>
#include <common/key_derive.h>
#include <common/status.h>
#include <common/type_to_string.h>
#include <common/utils.h>
@@ -344,16 +346,27 @@ static struct io_plan *handle_client(struct io_conn *conn,
return io_close(conn);
}
/**
* hsm_peer_secret_base -- Derive the base secret seed for per-peer seeds
*
* This secret is shared by all channels/peers for the client. The
* per-peer seeds will be generated from it by mixing in the
* channel_id and the peer node_id.
*/
static void hsm_peer_secret_base(struct secret *peer_seed_base)
{
hkdf_sha256(peer_seed_base, sizeof(struct secret), NULL, 0,
&secretstuff.hsm_secret, sizeof(secretstuff.hsm_secret),
"peer seed", strlen("peer seed"));
}
static void send_init_response(struct daemon_conn *master)
{
struct pubkey node_id;
struct secret peer_seed;
u8 *msg;
hkdf_sha256(&peer_seed, sizeof(peer_seed), NULL, 0,
&secretstuff.hsm_secret,
sizeof(secretstuff.hsm_secret),
"peer seed", strlen("peer seed"));
hsm_peer_secret_base(&peer_seed);
node_key(NULL, &node_id);
msg = towire_hsm_init_reply(master, &node_id, &peer_seed,
@@ -533,6 +546,55 @@ static void pass_client_hsmfd(struct daemon_conn *master, const u8 *msg)
daemon_conn_send_fd(master, fds[1]);
}
static void derive_peer_seed(struct privkey *peer_seed, struct privkey *peer_seed_base,
const struct pubkey *peer_id, const u64 channel_id)
{
u8 input[PUBKEY_DER_LEN + sizeof(channel_id)];
char *info = "per-peer seed";
pubkey_to_der(input, peer_id);
memcpy(input + PUBKEY_DER_LEN, &channel_id, sizeof(channel_id));
hkdf_sha256(peer_seed, sizeof(*peer_seed),
input, sizeof(input),
peer_seed_base, sizeof(*peer_seed_base),
info, strlen(info));
}
static void hsm_unilateral_close_privkey(struct privkey *dst,
struct unilateral_close_info *info)
{
struct privkey peer_seed, peer_seed_base;
struct basepoints basepoints;
struct secrets secrets;
hsm_peer_secret_base(&peer_seed_base.secret);
derive_peer_seed(&peer_seed, &peer_seed_base, &info->peer_id, info->channel_id);
derive_basepoints(&peer_seed, NULL, &basepoints, &secrets, NULL);
derive_simple_privkey(&secrets.payment_basepoint_secret,
&basepoints.payment, &info->commitment_point,
dst);
}
/**
* hsm_key_for_utxo - generate the keypair matching the utxo
*/
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_trace("Unilateral close output, deriving secrets");
hsm_unilateral_close_privkey(privkey, utxo->close_info);
pubkey_from_privkey(privkey, pubkey);
status_trace("Derived public key %s from unilateral close", type_to_string(trc, struct pubkey, pubkey));
} else {
/* Simple case: just get derive via HD-derivation */
bitcoin_keypair(privkey, pubkey, utxo->keyindex);
}
}
/* Note that it's the main daemon that asks for the funding signature so it
* can broadcast it. */
static void sign_funding_tx(struct daemon_conn *master, const u8 *msg)
@@ -575,7 +637,8 @@ static void sign_funding_tx(struct daemon_conn *master, const u8 *msg)
u8 *subscript;
secp256k1_ecdsa_signature sig;
bitcoin_keypair(&inprivkey, &inkey, in->keyindex);
hsm_key_for_utxo(&inprivkey, &inkey, in);
if (in->is_p2sh)
subscript = bitcoin_redeem_p2sh_p2wpkh(tmpctx, &inkey);
else
@@ -649,8 +712,9 @@ static void sign_withdrawal_tx(struct daemon_conn *master, const u8 *msg)
u8 *subscript;
secp256k1_ecdsa_signature sig;
bitcoin_keypair(&inprivkey, &inkey, in->keyindex);
if (utxos[i]->is_p2sh)
hsm_key_for_utxo(&inprivkey, &inkey, in);
if (in->is_p2sh || in->close_info != NULL)
subscript = bitcoin_redeem_p2sh_p2wpkh(tmpctx, &inkey);
else
subscript = NULL;