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zebra: 5-MOAD scan; zebra-0001 CWE-407 ZIP-317 dep check O(T^2) Vec scan, 500x at T=1000

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russell@unturf.com 2026-04-03 18:04:48 -04:00
parent de09497fb3
commit 75987e9d31
3 changed files with 279 additions and 0 deletions
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121
defects/zebra-0001/patch/zebra-0001-zip317-dep-check-hashset.patch Normal file
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@ -0,0 +1,121 @@
# UNDF: UNDF-PENDING
--- a/zebra-rpc/src/methods/types/get_block_template/zip317.rs
+++ b/zebra-rpc/src/methods/types/get_block_template/zip317.rs
@@ -91,9 +91,11 @@ pub fn select_mempool_transactions(
// Setup the transaction lists.
let (mut conventional_fee_txs, mut low_fee_txs): (Vec<_>, Vec<_>) = independent_mempool_txs
.into_values()
.partition(VerifiedUnminedTx::pays_conventional_fee);
let mut selected_txs = Vec::new();
+ // HashSet of selected tx IDs for O(1) dependency satisfaction checks.
+ let mut selected_tx_ids: HashSet<transaction::Hash> = HashSet::new();
// Set up limit tracking
let mut remaining_block_bytes: usize = MAX_BLOCK_BYTES.try_into().expect("fits in memory");
@@ -108,7 +110,7 @@ pub fn select_mempool_transactions(
while let Some(tx_weights) = conventional_fee_tx_weights {
conventional_fee_tx_weights = checked_add_transaction_weighted_random(
&mut conventional_fee_txs,
&mut dependent_mempool_txs,
tx_weights,
&mut selected_txs,
+ &mut selected_tx_ids,
&mempool_tx_deps,
&mut remaining_block_bytes,
&mut remaining_block_sigops,
@@ -122,7 +124,7 @@ pub fn select_mempool_transactions(
while let Some(tx_weights) = low_fee_tx_weights {
low_fee_tx_weights = checked_add_transaction_weighted_random(
&mut low_fee_txs,
&mut dependent_mempool_txs,
tx_weights,
&mut selected_txs,
+ &mut selected_tx_ids,
&mempool_tx_deps,
&mut remaining_block_bytes,
&mut remaining_block_sigops,
@@ -210,20 +212,16 @@ fn dependencies_depth(
/// Checks if every item in `candidate_tx_deps` is present in `selected_txs`.
///
-/// Requires items in `selected_txs` to be unique to work correctly.
-fn has_direct_dependencies(
+/// Uses a pre-built `selected_tx_ids` HashSet for O(D) membership checks
+/// instead of scanning the entire Vec<SelectedMempoolTx> in O(S) per call.
+fn has_direct_dependencies(
candidate_tx_deps: Option<&HashSet<transaction::Hash>>,
- selected_txs: &Vec<SelectedMempoolTx>,
+ selected_tx_ids: &HashSet<transaction::Hash>,
) -> bool {
let Some(deps) = candidate_tx_deps else {
return true;
};
- if selected_txs.len() < deps.len() {
- return false;
- }
-
- let mut num_available_deps = 0;
- for tx in selected_txs {
- #[cfg(test)]
- let (_, tx) = tx;
- if deps.contains(&tx.transaction.id.mined_id()) {
- num_available_deps += 1;
- } else {
- continue;
- }
-
- if num_available_deps == deps.len() {
- return true;
- }
- }
-
- false
+ // O(D) where D = number of direct dependencies (typically 1-3).
+ // Previously O(S) where S = number of already-selected transactions.
+ deps.iter().all(|dep_id| selected_tx_ids.contains(dep_id))
}
/// Chooses a random transaction from `txs` using the weighted index `tx_weights`,
@@ -275,6 +273,7 @@ fn checked_add_transaction_weighted_random(
candidate_txs: &mut Vec<VerifiedUnminedTx>,
dependent_txs: &mut HashMap<transaction::Hash, VerifiedUnminedTx>,
tx_weights: WeightedIndex<f32>,
selected_txs: &mut Vec<SelectedMempoolTx>,
+ selected_tx_ids: &mut HashSet<transaction::Hash>,
mempool_tx_deps: &TransactionDependencies,
remaining_block_bytes: &mut usize,
remaining_block_sigops: &mut u32,
@@ -298,11 +297,14 @@ fn checked_add_transaction_weighted_random(
"all candidate transactions should be independent"
);
+ selected_tx_ids.insert(*selected_tx_id);
+
#[cfg(not(test))]
selected_txs.push(candidate_tx);
#[cfg(test)]
selected_txs.push((0, candidate_tx));
// Try adding any dependent transactions if all of their dependencies have been selected.
let mut current_level_dependents = mempool_tx_deps.direct_dependents(selected_tx_id);
@@ -314,7 +316,7 @@ fn checked_add_transaction_weighted_random(
// the selected txs, which come from the mempool. If the tx also spends in-chain outputs, it won't
// be added. This behavior is not specified by consensus rules and can be changed at any time,
// meaning that such txs could be added.
- if has_direct_dependencies(tx_dependencies.get(dependent_tx_id), selected_txs) {
+ if has_direct_dependencies(tx_dependencies.get(dependent_tx_id), selected_tx_ids) {
let Some(candidate_tx) = dependent_txs.remove(dependent_tx_id) else {
continue;
};
@@ -337,6 +339,8 @@ fn checked_add_transaction_weighted_random(
continue;
}
+ selected_tx_ids.insert(*dependent_tx_id);
+
#[cfg(not(test))]
selected_txs.push(candidate_tx);