Allow funding errors in `full_stack_target` fuzzer
What the developer wrote
Authored by Matt Corallo
Allow funding errors in `full_stack_target` fuzzer
When a channel gets replaced before we can fund it, its possible
now (due to RNG output repetition) to hit the "trying to fund
channel before its ready to be funded" error in the
`full_stack_target` fuzzer.
Thus, we now simply ignore errors when funding.
What changed, and why it matters
This commit changes a fuzz test (a randomized testing harness) so it no longer crashes when it tries to fund a channel that isn't ready to be funded. The change only affects test code, not the real Lightning node software that users run. It is a test-hardening fix, not a security patch for a vulnerability in production code.
No production action required. Reviewers may want to confirm that ignoring all funding errors in the fuzzer does not mask a real invariant violation in the underlying ChannelManager, but the commit message gives a plausible rationale.
Security signals we found
Change is confined to fuzz test code (fuzz/src/full_stack.rs)
Removal of a panic path in a test harness
No modification to production channel funding logic
Commit message frames the change as fuzzer behavior adjustment, not security fix
Evidence from the diff
The diff modifies fuzz/src/full_stack.rs. Previously, batch_funding_transaction_generated() errors were inspected: ChannelUnavailable was tolerated, but any other APIError caused a panic. After the change, all funding errors are silently ignored, and pending_funding_signatures is only populated when funding succeeds. The commit message explains the panic could be triggered legitimately when a channel is replaced before funding due to repeated RNG outputs in fuzzing. This is a fuzzer robustness change; the production channelmanager behavior is unchanged.
Changed components
fuzz/src/full_stack.rs test harnessInspect captured patch +7 / −13
diff --git a/fuzz/src/full_stack.rs b/fuzz/src/full_stack.rs
index 3a5a549..88e68e5 100644
--- a/fuzz/src/full_stack.rs
+++ b/fuzz/src/full_stack.rs
@@ -857,21 +857,15 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger>) {
}
if tx.version.0 <= 0xff && !channels.is_empty() {
let chans = channels.iter().map(|(a, b)| (a, b)).collect::<Vec<_>>();
- if let Err(e) =
- channelmanager.batch_funding_transaction_generated(&chans, tx.clone())
- {
- // It's possible the channel has been closed in the mean time, but any other
- // failure may be a bug.
- if let APIError::ChannelUnavailable { .. } = e {
- } else {
- panic!();
+ let res =
+ channelmanager.batch_funding_transaction_generated(&chans, tx.clone());
+ if res.is_ok() {
+ let funding_txid = tx.compute_txid();
+ for idx in 0..tx.output.len() {
+ let outpoint = OutPoint { txid: funding_txid, index: idx as u16 };
+ pending_funding_signatures.insert(outpoint, tx.clone());
}
}
- let funding_txid = tx.compute_txid();
- for idx in 0..tx.output.len() {
- let outpoint = OutPoint { txid: funding_txid, index: idx as u16 };
- pending_funding_signatures.insert(outpoint, tx.clone());
- }
}
},
11 => {
Why this scored 18/100
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