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core-lightning/common/key_derive.c
Rusty Russell 4ffda340d3 check: make sure all files outside contrib/ include "config.h" first. 
And turn "" includes into full-path (which makes it easier to put
config.h first, and finds some cases check-includes.sh missed
previously).

config.h sets _GNU_SOURCE which really needs to be done before any
'#includes': we mainly got away with it with glibc, but other platforms
like Alpine may have stricter requirements.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2021-12-06 10:05:39 +10:30

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#include "config.h"
#include <bitcoin/privkey.h>
#include <bitcoin/pubkey.h>
#include <common/key_derive.h>
#include <common/utils.h>
#include <wally_bip32.h>
/* BOLT #3:
*
* ### `localpubkey`, `local_htlcpubkey`, `remote_htlcpubkey`, `local_delayedpubkey`, and `remote_delayedpubkey` Derivation
*
* These pubkeys are simply generated by addition from their base points:
*
* pubkey = basepoint + SHA256(per_commitment_point || basepoint) * G
*
* The `localpubkey` uses the local node's `payment_basepoint`;
* The `remotepubkey` uses the remote node's `payment_basepoint`;
* the `local_htlcpubkey` uses the local node's `htlc_basepoint`;
* the `remote_htlcpubkey` uses the remote node's `htlc_basepoint`;
* the `local_delayedpubkey` uses the local node's `delayed_payment_basepoint`;
* and the `remote_delayedpubkey` uses the remote node's `delayed_payment_basepoint`.
*...
* If `option_static_remotekey` or `option_anchors` 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`.
*/
bool derive_simple_key(const struct pubkey *basepoint,
const struct pubkey *per_commitment_point,
struct pubkey *key)
{
struct sha256 sha;
unsigned char der_keys[PUBKEY_CMPR_LEN * 2];
pubkey_to_der(der_keys, per_commitment_point);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, basepoint);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(per_commitment_point || basepoint)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n",
tal_hexstr(tmpctx, &sha, sizeof(sha)));
#endif
*key = *basepoint;
if (secp256k1_ec_pubkey_tweak_add(secp256k1_ctx,
&key->pubkey, sha.u.u8) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# + basepoint (0x%s)\n",
type_to_string(tmpctx, struct pubkey, basepoint));
printf("# = 0x%s\n",
type_to_string(tmpctx, struct pubkey, key));
#endif
return true;
}
/* BOLT #3:
*
* The corresponding private keys can be similarly derived, if the basepoint
* secrets are known (i.e. the private keys corresponding to `localpubkey`,
* `local_htlcpubkey`, and `local_delayedpubkey` only):
*
* privkey = basepoint_secret + SHA256(per_commitment_point || basepoint)
*/
bool derive_simple_privkey(const struct secret *base_secret,
const struct pubkey *basepoint,
const struct pubkey *per_commitment_point,
struct privkey *key)
{
struct sha256 sha;
unsigned char der_keys[PUBKEY_CMPR_LEN * 2];
pubkey_to_der(der_keys, per_commitment_point);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, basepoint);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(per_commitment_point || basepoint)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n", tal_hexstr(tmpctx, &sha, sizeof(sha)));
#endif
key->secret = *base_secret;
if (secp256k1_ec_privkey_tweak_add(secp256k1_ctx, key->secret.data,
sha.u.u8) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# + basepoint_secret (0x%s)\n",
tal_hexstr(tmpctx, base_secret, sizeof(*base_secret)));
printf("# = 0x%s\n",
tal_hexstr(tmpctx, key, sizeof(*key)));
#endif
return true;
}
/* BOLT #3:
*
* The `revocationpubkey` is a blinded key: when the local node wishes to
* create a new commitment for the remote node, it uses its own
* `revocation_basepoint` and the remote node's `per_commitment_point` to
* derive a new `revocationpubkey` for the commitment. After the remote node
* reveals the `per_commitment_secret` used (thereby revoking that
* commitment), the local node can then derive the `revocationprivkey`, as it
* now knows the two secrets necessary to derive the key
* (`revocation_basepoint_secret` and `per_commitment_secret`).
*
* The `per_commitment_point` is generated using elliptic-curve multiplication:
*
* per_commitment_point = per_commitment_secret * G
*
* And this is used to derive the revocation pubkey from the remote node's
* `revocation_basepoint`:
*
* revocationpubkey = revocation_basepoint * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_point * SHA256(per_commitment_point || revocation_basepoint)
*/
bool derive_revocation_key(const struct pubkey *basepoint,
const struct pubkey *per_commitment_point,
struct pubkey *key)
{
struct sha256 sha;
unsigned char der_keys[PUBKEY_CMPR_LEN * 2];
secp256k1_pubkey add[2];
const secp256k1_pubkey *args[2];
pubkey_to_der(der_keys, basepoint);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, per_commitment_point);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(revocation_basepoint || per_commitment_point)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
#endif
add[0] = basepoint->pubkey;
if (secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx, &add[0], sha.u.u8) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# x revocation_basepoint = 0x%s\n",
type_to_string(tmpctx, secp256k1_pubkey, &add[0]));
#endif
pubkey_to_der(der_keys, per_commitment_point);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, basepoint);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(per_commitment_point || revocation_basepoint)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
#endif
add[1] = per_commitment_point->pubkey;
if (secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx, &add[1], sha.u.u8) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# x per_commitment_point = 0x%s\n",
type_to_string(tmpctx, secp256k1_pubkey, &add[1]));
#endif
args[0] = &add[0];
args[1] = &add[1];
if (secp256k1_ec_pubkey_combine(secp256k1_ctx, &key->pubkey, args, 2)
!= 1)
return false;
#ifdef SUPERVERBOSE
printf("# 0x%s + 0x%s => 0x%s\n",
type_to_string(tmpctx, secp256k1_pubkey, args[0]),
type_to_string(tmpctx, secp256k1_pubkey, args[1]),
type_to_string(tmpctx, struct pubkey, key));
#endif
return true;
}
/* BOLT #3:
*
* The corresponding private key can be derived once the `per_commitment_secret`
* is known:
*
* revocationprivkey = revocation_basepoint_secret * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_secret * SHA256(per_commitment_point || revocation_basepoint)
*/
bool derive_revocation_privkey(const struct secret *base_secret,
const struct secret *per_commitment_secret,
const struct pubkey *basepoint,
const struct pubkey *per_commitment_point,
struct privkey *key)
{
struct sha256 sha;
unsigned char der_keys[PUBKEY_CMPR_LEN * 2];
struct secret part2;
pubkey_to_der(der_keys, basepoint);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, per_commitment_point);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(revocation_basepoint || per_commitment_point)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
#endif
key->secret = *base_secret;
if (secp256k1_ec_privkey_tweak_mul(secp256k1_ctx, key->secret.data,
sha.u.u8)
!= 1)
return false;
#ifdef SUPERVERBOSE
printf("# * revocation_basepoint_secret (0x%s)",
tal_hexstr(tmpctx, base_secret, sizeof(*base_secret))),
printf("# = 0x%s\n", tal_hexstr(tmpctx, key, sizeof(*key))),
#endif
pubkey_to_der(der_keys, per_commitment_point);
pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, basepoint);
sha256(&sha, der_keys, sizeof(der_keys));
#ifdef SUPERVERBOSE
printf("# SHA256(per_commitment_point || revocation_basepoint)\n");
printf("# => SHA256(0x%s || 0x%s)\n",
tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN),
tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN));
printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
#endif
part2 = *per_commitment_secret;
if (secp256k1_ec_privkey_tweak_mul(secp256k1_ctx, part2.data,
sha.u.u8) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# * per_commitment_secret (0x%s)",
tal_hexstr(tmpctx, per_commitment_secret,
sizeof(*per_commitment_secret))),
printf("# = 0x%s\n", tal_hexstr(tmpctx, &part2, sizeof(part2)));
#endif
if (secp256k1_ec_privkey_tweak_add(secp256k1_ctx, key->secret.data,
part2.data) != 1)
return false;
#ifdef SUPERVERBOSE
printf("# => 0x%s\n", tal_hexstr(tmpctx, key, sizeof(*key)));
#endif
return true;
}
bool bip32_pubkey(const struct ext_key *bip32_base,
struct pubkey *pubkey, u32 index)
{
const uint32_t flags = BIP32_FLAG_KEY_PUBLIC | BIP32_FLAG_SKIP_HASH;
struct ext_key ext;
if (index >= BIP32_INITIAL_HARDENED_CHILD)
return false;
if (bip32_key_from_parent(bip32_base, index, flags, &ext) != WALLY_OK)
return false;
if (!secp256k1_ec_pubkey_parse(secp256k1_ctx, &pubkey->pubkey,
ext.pub_key, sizeof(ext.pub_key)))
return false;
return true;
}
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