pytest: fix feerate check in test_peer_anchor_push
What the developer wrote
Authored by Rusty Russell
pytest: fix feerate check in test_peer_anchor_push
We didn't log when anchor transactions had short signatures,
which causes this test to not assert (did_short_sig):
```
total_feerate_perkw = total_fees / total_weight * 1000
> check_feerate([l3, l2], total_feerate_perkw, feerate)
tests/test_closing.py:4063:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
nodes = [<fixtures.LightningNode object at 0x7f0fb322bb20>, <fixtures.LightningNode object at 0x7f0fb1b5ead0>]
actual_feerate = 14006.105538595726, expected_feerate = 14000
def check_feerate(nodes, actual_feerate, expected_feerate):
# Feerate can't be lower.
assert actual_feerate > expected_feerate - 2
if actual_feerate >= expected_feerate + 2:
if any([did_short_sig(n) for n in nodes]):
return
# Use assert as it shows the actual values on failure
> assert actual_feerate < expected_feerate + 2
E AssertionError
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
What changed, and why it matters
This commit fixes a test-only logging issue. A developer warning flag (dev_warn_on_overgrind) was not logging when an anchor transaction signature was shorter than expected, causing a pytest test to fail its feerate assertion. The fix adds a log message so the test can detect the short signature and skip the strict feerate check. There is no production security vulnerability here.
No security action required. Treat as normal test reliability fix. If reviewing, confirm dev_warn_on_overgrind is a developer-only flag and not enabled in production builds.
Security signals we found
No cryptographic weakness introduced or fixed
No privilege boundary crossed
No input validation change
Test-only diagnostic logging change
Signature length check is informational only
Evidence from the diff
The change adds a conditional log in hsmd/libhsmd.c’s handle_sign_anchorspend() that emits a LOG_BROKEN message when dev_warn_on_overgrind is enabled and the produced anchor spend signature is shorter than 71 bytes. This log is consumed by the test helper did_short_sig() in tests/test_closing.py. Without the log, did_short_sig() returns false, so check_feerate() enforces the stricter upper bound and fails when the actual feerate is slightly above expected due to the smaller signature reducing transaction weight. The fix is purely diagnostic/test-infrastructure; the signature itself remains valid.
Changed components
hsmd/libhsmd.chandle_sign_anchorspend()tests/test_closing.py::test_peer_anchor_pushInspect captured patch +7 / −0
diff --git a/hsmd/libhsmd.c b/hsmd/libhsmd.c
index e4a14e4..dd23292 100644
--- a/hsmd/libhsmd.c
+++ b/hsmd/libhsmd.c
@@ -1820,6 +1820,13 @@ static u8 *handle_sign_anchorspend(struct hsmd_client *c, const u8 *msg_in)
fmt_pubkey(tmpctx, &local_funding_pubkey),
fmt_wally_psbt(tmpctx, psbt));
}
+ if (dev_warn_on_overgrind
+ && psbt->inputs[0].signatures.num_items == 1
+ && psbt->inputs[0].signatures.items[0].value_len < 71) {
+ hsmd_status_fmt(LOG_BROKEN, NULL,
+ "overgrind: short signature length %zu",
+ psbt->inputs[0].signatures.items[0].value_len);
+ }
return towire_hsmd_sign_anchorspend_reply(NULL, psbt);
}
Why this scored 17/100
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