crates.io · zaino-state
zaino-state has a Non-Finalized State Reorg — No Cycle Detection or Depth Limit
NonFinalizedState::handle_reorg is a recursive, unbounded async function that traverses parent blocks until it finds a common ancestor on the main chain. It has no recursion depth limit and no cycle detection. A malicious or buggy validator can serve a block whose previous_block_hash points back to itself (or forms a cycle with other blocks), causing handle_reorg to infinite-loop, consuming 100% CPU and never making sync progress. Additionally, update() contains an .expect("empty snapshot impossible") that panics if the non-finalized snapshot becomes empty after trimming finalized blocks.
Location: packages/zaino-state/src/chain_index/non_finalised_state.rs:443-489
async fn handle_reorg(
&self,
working_snapshot: &mut NonfinalizedBlockCacheSnapshot,
block: &impl Block,
) -> Result<IndexedBlock, SyncError> {
let prev_block = match working_snapshot
.get_block_by_hash_bytes_in_serialized_order(block.prev_hash_bytes_serialized_order())
.cloned()
{
Some(prev_block) => {
if !working_snapshot
.heights_to_hashes
.values()
.any(|hash| hash == prev_block.hash())
{
Box::pin(self.handle_reorg(working_snapshot, &prev_block)).await? // <-- LINE 459
} else {
prev_block
}
}
None => {
let prev_block = self
.source
.get_block(HashOrHeight::Hash(
zebra_chain::block::Hash::from_bytes_in_serialized_order(
block.prev_hash_bytes_serialized_order(),
),
))
.await
.map_err(|e| { ... })?
.ok_or(SyncError::ValidatorConnectionError(...))?;
Box::pin(self.handle_reorg(working_snapshot, &*prev_block)).await? // <-- LINE 483
}
};
let indexed_block = block.to_indexed_block(&prev_block, self).await?;
working_snapshot.add_block_new_chaintip(indexed_block.clone());
Ok(indexed_block)
}
Infinite loop via self-referencing block:
B where B.prev_hash == B.hash.handle_reorg is called with B.get_block_by_hash_bytes_in_serialized_order(B.prev_hash) finds B itself in working_snapshot.blocks.B.hash in working_snapshot.heights_to_hashes? If B is a new chaintip not yet on the main chain, no.prev_block = B (the exact same block).Box::pin future each iteration, consuming heap memory and CPU.Stack exhaustion via deep reorg:
A deep reorg of >1000 blocks would recurse >1000 times. Each async recursion creates a new Box::pin future on the heap. While this won't exhaust the native stack immediately, it will allocate unbounded heap memory and CPU time, effectively DoS-ing the sync task.
.expect("empty snapshot impossible") panic:
Location: packages/zaino-state/src/chain_index/non_finalised_state.rs:543-548
new_snapshot.remove_finalized_blocks(finalized_height);
let best_block = &new_snapshot
.blocks
.values()
.max_by_key(|block| block.chainwork())
.cloned()
.expect("empty snapshot impossible"); // <-- LINE 548
If finalized_height is greater than or equal to all blocks in new_snapshot.blocks, remove_finalized_blocks retains only blocks at or above that height. If none exist, new_snapshot.blocks becomes empty. The .expect() then panics. While the comment claims this is "impossible," defensive programming dictates it is reachable under corruption or edge-case sync conditions.
header.previous_block_hash == block.hash().NonFinalizedState::sync enters handle_reorg and infinite-loops.SyncError::ReorgFailure if exceeded:const MAX_REORG_DEPTH: usize = 1000;
HashSet<BlockHash> during traversal to detect cycles and abort with an error..expect("empty snapshot impossible") with a proper Err(UpdateError::DatabaseHole) or similar error return.handle_reorg, starving the async runtime and stalling response serving.Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.