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derive_basepoints: harden checking.

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I managed to crash the HSM by asking for point -1 (shachain_index has an
assert).  Fail in this case, instead.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2018-08-17 14:36:24 +09:30
committed by Christian Decker
parent 8340d8c070
commit 7f37fa3263
3 changed files with 24 additions and 8 deletions
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19
common/derive_basepoints.c
View File

@@ -51,26 +51,30 @@ bool derive_basepoints(const struct secret *seed,
return true;
}
void per_commit_secret(const struct sha256 *shaseed,
bool per_commit_secret(const struct sha256 *shaseed,
struct secret *commit_secret,
u64 per_commit_index)
{
struct sha256 s;
if (per_commit_index >= (1ULL << SHACHAIN_BITS))
return false;
shachain_from_seed(shaseed, shachain_index(per_commit_index), &s);
BUILD_ASSERT(sizeof(s) == sizeof(*commit_secret));
memcpy(commit_secret, &s, sizeof(s));
return true;
}
bool per_commit_point(const struct sha256 *shaseed,
struct pubkey *commit_point,
u64 per_commit_index)
{
struct sha256 per_commit_secret;
struct secret secret;
/* Derive new per-commitment-point. */
shachain_from_seed(shaseed, shachain_index(per_commit_index),
&per_commit_secret);
if (!per_commit_secret(shaseed, &secret, per_commit_index))
return false;
/* BOLT #3:
*
@@ -81,7 +85,7 @@ bool per_commit_point(const struct sha256 *shaseed,
*/
if (secp256k1_ec_pubkey_create(secp256k1_ctx,
&commit_point->pubkey,
per_commit_secret.u.u8) != 1)
secret.data) != 1)
return false;
return true;
@@ -235,6 +239,9 @@ bool shachain_get_secret(const struct shachain *shachain,
{
struct sha256 sha;
if (commit_num >= (1ULL << SHACHAIN_BITS))
return false;
if (!shachain_get_hash(shachain, shachain_index(commit_num), &sha))
return false;
BUILD_ASSERT(sizeof(*preimage) == sizeof(sha));

4
common/derive_basepoints.h
View File

@@ -112,8 +112,10 @@ bool derive_htlc_basepoint(const struct secret *seed,
* @shaseed: the sha256 seed
* @commit_secret: the returned per-commit secret.
* @per_commit_index: (in) which @commit_secret to return.
*
* Returns false if per_commit_index is invalid, or can't derive.
*/
void per_commit_secret(const struct sha256 *shaseed,
bool per_commit_secret(const struct sha256 *shaseed,
struct secret *commit_secret,
u64 per_commit_index);

9
hsmd/hsm.c
View File

@@ -628,7 +628,14 @@ handle_get_per_commitment_point(struct io_conn *conn, struct client *c)
if (n >= 2) {
old_secret = tal(tmpctx, struct secret);
per_commit_secret(&shaseed, old_secret, n - 2);
if (!per_commit_secret(&shaseed, old_secret, n - 2)) {
status_broken("Cannot derive secret %"PRIu64
" for client %s",
n - 1,
type_to_string(tmpctx,
struct pubkey, &c->id));
goto fail;
}
} else
old_secret = NULL;