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channeld: make per_commit_point and per_commit_secret handling clearer.

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All the +1 and -1 in the existing combination routine were confusing.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2017-06-20 15:39:03 +09:30
parent 9497cbe73b
commit 90284af249
3 changed files with 45 additions and 28 deletions
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22
lightningd/channel/channel.c
View File

@@ -583,11 +583,10 @@ static struct io_plan *send_revocation(struct io_conn *conn, struct peer *peer)
u8 *msg;
peer->old_per_commit[LOCAL] = peer->current_per_commit[LOCAL];
if (!next_per_commit_point(&peer->shaseed, &old_commit_secret,
&peer->current_per_commit[LOCAL],
peer->commit_index[LOCAL]))
status_failed(WIRE_CHANNEL_CRYPTO_FAILED,
"Deriving next commit_point");
/* Get N-1th secret. */
per_commit_secret(&peer->shaseed, &old_commit_secret,
peer->commit_index[LOCAL] - 1);
pubkey_from_privkey((struct privkey *)&old_commit_secret, &test);
if (!pubkey_eq(&test, &oldpoint))
@@ -596,7 +595,12 @@ static struct io_plan *send_revocation(struct io_conn *conn, struct peer *peer)
tal_hexstr(trc, &old_commit_secret,
sizeof(old_commit_secret)));
peer->commit_index[LOCAL]++;
/* Send N+1th point. */
if (!per_commit_point(&peer->shaseed,
&peer->current_per_commit[LOCAL],
++peer->commit_index[LOCAL]))
status_failed(WIRE_CHANNEL_CRYPTO_FAILED,
"Deriving next commit_point");
/* If this queues more changes on the other end, send commit. */
if (channel_sending_revoke_and_ack(peer->channel)) {
@@ -1348,9 +1352,9 @@ static void handle_funding_locked(struct peer *peer, const u8 *msg)
&peer->short_channel_ids[LOCAL]))
status_failed(WIRE_CHANNEL_BAD_COMMAND, "%s", tal_hex(msg, msg));
next_per_commit_point(&peer->shaseed, NULL,
&peer->current_per_commit[LOCAL],
peer->commit_index[LOCAL]++);
per_commit_point(&peer->shaseed,
&peer->current_per_commit[LOCAL],
++peer->commit_index[LOCAL]);
msg = towire_funding_locked(peer,
&peer->channel_id,

27
lightningd/derive_basepoints.c
View File

@@ -68,23 +68,22 @@ bool derive_basepoints(const struct privkey *seed,
return true;
}
bool next_per_commit_point(const struct sha256 *shaseed,
struct sha256 *old_commit_secret,
struct pubkey *per_commit_point,
u64 per_commit_index)
void per_commit_secret(const struct sha256 *shaseed,
struct sha256 *commit_secret,
u64 per_commit_index)
{
shachain_from_seed(shaseed, shachain_index(per_commit_index),
commit_secret);
}
bool per_commit_point(const struct sha256 *shaseed,
struct pubkey *commit_point,
u64 per_commit_index)
{
struct sha256 per_commit_secret;
/* Get old secret. */
if (per_commit_index > 0)
shachain_from_seed(shaseed, shachain_index(per_commit_index - 1),
old_commit_secret);
else
assert(old_commit_secret == NULL);
/* Derive new per-commitment-point. */
shachain_from_seed(shaseed, shachain_index(per_commit_index + 1),
shachain_from_seed(shaseed, shachain_index(per_commit_index),
&per_commit_secret);
/* BOLT #3:
@@ -94,7 +93,7 @@ bool next_per_commit_point(const struct sha256 *shaseed,
* per_commitment_point = per_commitment_secret * G
*/
if (secp256k1_ec_pubkey_create(secp256k1_ctx,
&per_commit_point->pubkey,
&commit_point->pubkey,
per_commit_secret.u.u8) != 1)
return false;

24
lightningd/derive_basepoints.h
View File

@@ -37,11 +37,25 @@ bool derive_basepoints(const struct privkey *seed,
struct pubkey *per_commit_point,
u64 per_commit_index);
/* Give up secret for index-1, and generate per-commitment point for N+1. */
bool next_per_commit_point(const struct sha256 *shaseed,
struct sha256 *old_commit_secret,
struct pubkey *per_commit_point,
u64 per_commit_index);
/**
* per_commit_secret - get a secret for this index.
* @shaseed: the sha256 seed
* @commit_secret: the returned per-commit secret.
* @per_commit_index: (in) which @commit_secret to return.
*/
void per_commit_secret(const struct sha256 *shaseed,
struct sha256 *commit_secret,
u64 per_commit_index);
/**
* per_commit_point - get the per-commit-point for this index.
* @shaseed: the sha256 seed
* @commit_point: the returned per-commit point.
* @per_commit_index: (in) which @commit_point to return.
*/
bool per_commit_point(const struct sha256 *shaseed,
struct pubkey *commit_point,
u64 per_commit_index);
/* BOLT #3:
*