wave11: 488/227 — ROS2/OpenCV/Open3D/metaflow/kubeflow/optuna/openssl/mbedtls/wolfssl + Kafka Streams/Pulsar

This commit is contained in:
russell@unturf.com 2026-03-27 17:31:52 -04:00
parent 6276aea2e5
commit 19333b378e
36 changed files with 4634 additions and 5 deletions

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# kafka-0006 — Kafka Streams DefaultTaskManager: ArrayList lockedTasks O(T×L) in hot scheduling loop
## Metadata
- **Project**: Apache Kafka
- **Component**: `streams/src/main/java/org/apache/kafka/streams/processor/internals/tasks/DefaultTaskManager.java`
- **CWE**: CWE-407 (Inefficient Algorithmic Complexity)
- **Severity**: MEDIUM
- **Complexity**: O(T × L) → O(T) where T = active tasks, L = locked tasks
- **Hot path**: `assignNextTask()` is called by every `TaskExecutor` thread on every scheduling cycle
## Location
```
streams/src/main/java/org/apache/kafka/streams/processor/internals/tasks/DefaultTaskManager.java
```
### Defective code — lockedTasks is ArrayList (line 62)
```java
// Line 62
private final List<TaskId> lockedTasks = new ArrayList<>();
```
### Defective code — O(T × L) in assignNextTask() (lines 105118)
```java
// Line 100: taskExecutors is also ArrayList — O(E) linear scan on every call
if (!taskExecutors.contains(executor)) {
throw new IllegalArgumentException("...");
}
// Lines 105118: for every active task, does O(L) linear scan of lockedTasks ArrayList
for (final StreamTask task : tasks.activeInitializedTasks()) {
if (!assignedTasks.containsKey(task.id()) &&
!lockedTasks.contains(task.id()) && // <-- O(L) ArrayList.contains per task
canProgress(task, time.milliseconds()) &&
!hasUncaughtException(task.id())
) {
assignedTasks.put(task.id(), executor);
return task;
}
}
```
Also at lines 131, 289 (same pattern in `awaitProcessableTasks`, `remove`).
## Fix
```java
// Change field declaration:
// BEFORE:
private final List<TaskId> lockedTasks = new ArrayList<>();
private final List<TaskExecutor> taskExecutors;
// AFTER:
private final Set<TaskId> lockedTasks = new HashSet<>();
private final List<TaskExecutor> taskExecutors; // small, bounded by numExecutors — OK
```
The `lockedTasks` field is used only for membership tests (`contains`) and bulk add/remove. A `HashSet<TaskId>` provides O(1) `contains` and `add`. The `taskExecutors` list is bounded by `numExecutors` (typically 14) so its linear scan is negligible; leave it as-is unless further optimization is desired.
All callers of `lockedTasks`:
- `lockTasks(Set<TaskId>)` — calls `lockedTasks.addAll(taskIds)` — works with HashSet
- `unlockTasks(Set<TaskId>)` — calls `lockedTasks.removeAll(taskIds)` — works with HashSet
- `lockedTasks.contains(task.id())` — O(1) with HashSet
- `lockedTasks.contains(taskId)` — O(1) with HashSet
No iterator order dependency exists — callers only test membership or add/remove sets.
## Complexity analysis
| Scenario | Before | After |
|----------|--------|-------|
| T active tasks, L locked tasks | O(T × L) | O(T) |
| T=1000 tasks, L=500 locked | 500,000 ops per scheduling cycle | 1,000 ops |
| Rebalancing with many locked tasks | Stalls executor threads | Minimal overhead |
## Notes
During rebalancing events, `lockTasks()` is called with a large set of task IDs to prevent task executors from processing them while partition reassignment occurs. At exactly this moment, the per-scheduling-cycle `assignNextTask()` loop pays the full O(T × L) cost on every executor thread wakeup.

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package unit;
import java.util.*;
/**
* kafka-0006: DefaultTaskManager lockedTasks ArrayList HashSet
*
* Demonstrates that ArrayList.contains() inside a task-scheduling loop is O(T×L)
* while HashSet.contains() is O(T).
*
* Compile: javac -d . KafkaStreamsDefaultTaskManagerTest.java
* Run: java unit.KafkaStreamsDefaultTaskManagerTest
*/
public class KafkaStreamsDefaultTaskManagerTest {
// Simulated TaskId (Integer wrapper for simplicity)
static class TaskId {
final int id;
TaskId(int id) { this.id = id; }
@Override public boolean equals(Object o) {
return o instanceof TaskId && ((TaskId) o).id == this.id;
}
@Override public int hashCode() { return Integer.hashCode(id); }
@Override public String toString() { return "Task-" + id; }
}
// --- SLOW: ArrayList lockedTasks (defective, mirrors DefaultTaskManager line 62) ---
static class DefectiveTaskManager {
private final List<TaskId> lockedTasks = new ArrayList<>();
private final List<TaskId> activeTasks;
DefectiveTaskManager(List<TaskId> activeTasks) {
this.activeTasks = activeTasks;
}
void lockTasks(Set<TaskId> ids) { lockedTasks.addAll(ids); }
// Returns count of assignable tasks mirrors assignNextTask() loop body
int countAssignable() {
int count = 0;
for (TaskId task : activeTasks) {
if (!lockedTasks.contains(task)) { // O(L) ArrayList scan
count++;
}
}
return count;
}
}
// --- FAST: HashSet lockedTasks (fixed) ---
static class FixedTaskManager {
private final Set<TaskId> lockedTasks = new HashSet<>();
private final List<TaskId> activeTasks;
FixedTaskManager(List<TaskId> activeTasks) {
this.activeTasks = activeTasks;
}
void lockTasks(Set<TaskId> ids) { lockedTasks.addAll(ids); }
int countAssignable() {
int count = 0;
for (TaskId task : activeTasks) {
if (!lockedTasks.contains(task)) { // O(1) HashSet lookup
count++;
}
}
return count;
}
}
static long bench(Runnable r, int iters) {
// warmup
for (int i = 0; i < 3; i++) r.run();
long t0 = System.nanoTime();
for (int i = 0; i < iters; i++) r.run();
return System.nanoTime() - t0;
}
public static void main(String[] args) {
System.out.println("kafka-0006: DefaultTaskManager lockedTasks ArrayList → HashSet");
System.out.println("=".repeat(65));
int[] sizes = {100, 500, 1000};
int iters = 500;
boolean allPass = true;
for (int n : sizes) {
// Build n active tasks, lock half
List<TaskId> active = new ArrayList<>();
Set<TaskId> toLock = new HashSet<>();
for (int i = 0; i < n; i++) {
TaskId t = new TaskId(i);
active.add(t);
if (i % 2 == 0) toLock.add(t);
}
DefectiveTaskManager slow = new DefectiveTaskManager(active);
slow.lockTasks(toLoad(toLoad(toLock)));
FixedTaskManager fast = new FixedTaskManager(active);
fast.lockTasks(toLoad(toLock));
// Correctness check
int slowResult = slow.countAssignable();
int fastResult = fast.countAssignable();
boolean correct = (slowResult == fastResult) && (slowResult == n / 2);
if (!correct) allPass = false;
long slowNs = bench(slow::countAssignable, iters);
long fastNs = bench(fast::countAssignable, iters);
double ratio = (double) slowNs / fastNs;
System.out.printf("N=%-5d slow=%7.2f ms fast=%7.2f ms ratio=%.1fx assignable=%d %s%n",
n,
slowNs / 1_000_000.0 / iters,
fastNs / 1_000_000.0 / iters,
ratio,
slowResult,
correct ? "PASS" : "FAIL(result mismatch)");
}
System.out.println("=".repeat(65));
System.out.println(allPass ? "ALL PASS" : "SOME FAILED");
if (!allPass) System.exit(1);
}
// Helper: copy set into set (simulate addAll contract)
static Set<TaskId> toLoad(Set<TaskId> s) { return s; }
}

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# kubeflow-0001 — O(T²×I) Pipeline Compiler: tasks_in_current_dag List membership in DAG compilation
**Severity:** HIGH
**Complexity:** O(T²×I) → O(T×I)
**CWE:** CWE-407 (Algorithmic Complexity)
## Affected File
| File | Lines | Notes |
|------|-------|-------|
| `sdk/python/kfp/compiler/pipeline_spec_builder.py` | 13831540 | Outer subgroup loop rebuilding list |
| `sdk/python/kfp/compiler/pipeline_spec_builder.py` | 91300 | `build_task_spec_for_task` — multiple O(T) `in` checks |
| `sdk/python/kfp/compiler/pipeline_spec_builder.py` | 11921260 | `build_task_spec_for_group` — O(T) `in` checks |
## Defective Code
### `pipeline_spec_builder.py` lines 13831395 (outer compilation loop)
```python
subgroups = group.groups + group.tasks
for subgroup in subgroups: # O(T) outer loop
...
tasks_in_current_dag = [ # ← REBUILT every iteration: O(T)
utils.sanitize_task_name(subgroup.name) for subgroup in subgroups
]
...
if isinstance(subgroup, pipeline_task.PipelineTask):
subgroup_task_spec = build_task_spec_for_task(
task=subgroup,
parent_component_inputs=...,
tasks_in_current_dag=tasks_in_current_dag, # List[str] passed in
)
```
### `pipeline_spec_builder.py` lines 194, 229, 293 (inside build_task_spec_for_task)
```python
for input_name, input_value in task.inputs.items(): # O(I) inputs per task
...
if input_value.task_name in tasks_in_current_dag: # ← O(T) scan of List[str]
...
if input_value.task_name in tasks_in_current_dag: # ← O(T) scan again
...
for channel in pipeline_channels:
if channel.task_name in tasks_in_current_dag: # ← O(T) scan again
```
**Defect:** `tasks_in_current_dag` is typed as `List[str]` (line 91 signature) and constructed
via list comprehension on every iteration of the outer `for subgroup in subgroups` loop — even
though the set of tasks in the DAG is fixed for the entire loop body.
Inside `build_task_spec_for_task`, each input channel performs an O(T) linear `in` search against
this list. With T tasks, I inputs per task, and 3 separate `in` checks per input branch:
- Total cost: O(T) rebuild × ignored (constant factor) + O(T) outer × O(I) inner × O(T) in-check
- **= O(T² × I)**
## Fix
1. Hoist the `tasks_in_current_dag` computation outside the loop (build once).
2. Change the type from `List[str]` to `Set[str]` for O(1) membership.
```python
# Build once, outside the loop
tasks_in_current_dag: Set[str] = {
utils.sanitize_task_name(sg.name) for sg in subgroups
}
for subgroup in subgroups:
...
# Pass the pre-built set — no more O(T) rebuild or O(T) in-check
if isinstance(subgroup, pipeline_task.PipelineTask):
subgroup_task_spec = build_task_spec_for_task(
task=subgroup,
parent_component_inputs=group_component_spec.input_definitions,
tasks_in_current_dag=tasks_in_current_dag, # now Set[str]
)
```
Update the function signatures:
```python
def build_task_spec_for_task(
task: pipeline_task.PipelineTask,
parent_component_inputs: pipeline_spec_pb2.ComponentInputsSpec,
tasks_in_current_dag: Set[str], # was List[str]
) -> pipeline_spec_pb2.PipelineTaskSpec:
```
The `in` checks at lines 194, 229, 293, 1235, 1247 now run in O(1) instead of O(T).
## Complexity
| Step | Before | After |
|------|--------|-------|
| Build `tasks_in_current_dag` | O(T) × T iterations = O(T²) | O(T) once |
| Each `in` check | O(T) | O(1) |
| Total compile cost per DAG | O(T² × I) | O(T × I) |
## Impact
Kubeflow Pipelines pipelines with hundreds of components (common in large ML training workflows,
feature engineering pipelines, and AutoML grids) pay quadratic cost during SDK compile time.
A pipeline with 200 tasks and 5 inputs each: 200² × 5 × 3 checks = 600,000 operations vs 3,000
with the fix — a 200× reduction.

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package unit;
import java.util.*;
/**
* kubeflow-0001 O(T²×I) pipeline DAG compilation in pipeline_spec_builder.py
*
* Simulates the defective pattern from:
* sdk/python/kfp/compiler/pipeline_spec_builder.py lines 13831540
*
* Defect:
* tasks_in_current_dag is a List[str] REBUILT inside the outer loop over T tasks,
* and then each task performs O(I) input lookups each doing O(T) list `in` check.
* Total: O(T) outer × O(I) inputs × O(T) in-check = O(T² × I).
*
* Fix:
* Build tasks_in_current_dag once as a Set[str] outside the loop.
* Each `in` check becomes O(1).
* Total: O(T × I).
*
* Op-count measures: number of string comparisons performed across all `in` checks.
*/
public class KubeflowTaskDagAlgorithm {
static void check(String desc, boolean cond) {
System.out.println((cond ? "PASS" : "FAIL") + ": " + desc);
if (!cond) throw new AssertionError("FAIL: " + desc);
}
// Simulates a PipelineTask with input channels that may reference other tasks
static class Task {
final String name;
final List<String> inputProducers; // task names that produce each input (may be null)
Task(String name, List<String> inputProducers) {
this.name = name;
this.inputProducers = inputProducers;
}
}
// Simulates build result: which inputs are "task outputs" vs "component inputs"
static class TaskSpec {
final Map<String, String> taskOutputInputs = new LinkedHashMap<>(); // input producer task
final Map<String, String> componentInputs = new LinkedHashMap<>(); // input component input
}
// Result carrying op-count
static class Result {
final List<TaskSpec> taskSpecs;
final long inChecks; // total string comparisons
Result(List<TaskSpec> specs, long checks) {
this.taskSpecs = specs;
this.inChecks = checks;
}
}
// -----------------------------------------------------------------------
// DEFECTIVE: List[str] rebuilt inside outer loop, O(T) in-check per input
// -----------------------------------------------------------------------
static long defectiveChecks;
static boolean listContains(List<String> list, String item) {
for (String s : list) {
defectiveChecks++;
if (s.equals(item)) return true;
}
return false;
}
static TaskSpec buildTaskSpecDefective(Task task, List<String> tasksInCurrentDag) {
TaskSpec spec = new TaskSpec();
for (String producer : task.inputProducers) {
if (producer == null) {
spec.componentInputs.put(task.name + "_null", "pipeline_input");
} else if (listContains(tasksInCurrentDag, producer)) {
spec.taskOutputInputs.put(task.name + "_from_" + producer, producer);
} else {
spec.componentInputs.put(task.name + "_from_" + producer, "outer_" + producer);
}
}
return spec;
}
static Result runDefective(List<Task> tasks) {
defectiveChecks = 0;
List<TaskSpec> specs = new ArrayList<>();
for (Task task : tasks) {
// DEFECTIVE: rebuilt on every iteration of the outer loop
List<String> tasksInCurrentDag = new ArrayList<>();
for (Task t : tasks) {
tasksInCurrentDag.add(t.name);
}
specs.add(buildTaskSpecDefective(task, tasksInCurrentDag));
}
return new Result(specs, defectiveChecks);
}
// -----------------------------------------------------------------------
// FIXED: Set[str] built once outside the loop, O(1) in-check per input
// -----------------------------------------------------------------------
static long fixedChecks;
static boolean setContains(Set<String> set, String item) {
fixedChecks++; // O(1) hash lookup counted as 1
return set.contains(item);
}
static TaskSpec buildTaskSpecFixed(Task task, Set<String> tasksInCurrentDag) {
TaskSpec spec = new TaskSpec();
for (String producer : task.inputProducers) {
if (producer == null) {
spec.componentInputs.put(task.name + "_null", "pipeline_input");
} else if (setContains(tasksInCurrentDag, producer)) {
spec.taskOutputInputs.put(task.name + "_from_" + producer, producer);
} else {
spec.componentInputs.put(task.name + "_from_" + producer, "outer_" + producer);
}
}
return spec;
}
static Result runFixed(List<Task> tasks) {
fixedChecks = 0;
List<TaskSpec> specs = new ArrayList<>();
// FIXED: built once outside the loop
Set<String> tasksInCurrentDag = new LinkedHashSet<>();
for (Task t : tasks) {
tasksInCurrentDag.add(t.name);
}
for (Task task : tasks) {
specs.add(buildTaskSpecFixed(task, tasksInCurrentDag));
}
return new Result(specs, fixedChecks);
}
// -----------------------------------------------------------------------
// Build test pipeline: T tasks, each with I inputs referencing earlier tasks
// -----------------------------------------------------------------------
static List<Task> buildPipeline(int T, int I) {
List<Task> tasks = new ArrayList<>();
for (int t = 0; t < T; t++) {
List<String> inputs = new ArrayList<>();
for (int i = 0; i < I; i++) {
if (t > 0) {
// reference a task within the same DAG
inputs.add("task" + (t - 1));
} else {
inputs.add(null); // pipeline-level input
}
}
tasks.add(new Task("task" + t, inputs));
}
return tasks;
}
// -----------------------------------------------------------------------
// Verify both produce identical specs
// -----------------------------------------------------------------------
static boolean specsEqual(List<TaskSpec> a, List<TaskSpec> b) {
if (a.size() != b.size()) return false;
for (int i = 0; i < a.size(); i++) {
if (!a.get(i).taskOutputInputs.equals(b.get(i).taskOutputInputs)) return false;
if (!a.get(i).componentInputs.equals(b.get(i).componentInputs)) return false;
}
return true;
}
public static void main(String[] args) {
System.out.println("=== kubeflow-0001: O(T²×I) tasks_in_current_dag List in pipeline compiler ===");
// ------ Test 1: correctness on small pipeline ------
{
List<Task> tasks = buildPipeline(5, 3);
Result def = runDefective(tasks);
Result fix = runFixed(tasks);
check("pipeline-5x3: same task specs (defective == fixed)", specsEqual(def.taskSpecs, fix.taskSpecs));
check("pipeline-5x3: fixed uses fewer checks", fix.inChecks <= def.inChecks);
}
// ------ Test 2: O(T²×I) vs O(T×I) scaling ------
{
int I = 5;
int T = 200;
List<Task> tasks = buildPipeline(T, I);
Result def = runDefective(tasks);
Result fix = runFixed(tasks);
long ratio = def.inChecks / Math.max(fix.inChecks, 1);
System.out.printf(" T=%d I=%d: defective checks=%d, fixed checks=%d, ratio=%dx%n",
T, I, def.inChecks, fix.inChecks, ratio);
// Defective: each of T tasks does I × O(T) checks = T² × I total
// Expected ~200² × 5 / 2 avg = ~100,000
check("T=200,I=5: defective checks > T*I*5 (quadratic evidence)",
def.inChecks > (long) T * I * 5);
// Fixed: T × I × 1 = 1000
// task0 has null producers so its I inputs are skipped before the set check;
// remaining T-1 tasks each do I checks (T-1)*I total (bounded by T*I)
check("T=200,I=5: fixed checks <= T*I (linear)",
fix.inChecks <= (long) T * I);
check("T=200,I=5: ratio >= 10x",
ratio >= 10);
check("T=200,I=5: same specs", specsEqual(def.taskSpecs, fix.taskSpecs));
}
// ------ Test 3: quadratic growth is clear ------
{
int I = 3;
List<Task> tasks100 = buildPipeline(100, I);
List<Task> tasks400 = buildPipeline(400, I);
Result def100 = runDefective(tasks100);
Result def400 = runDefective(tasks400);
double growthRatio = (double) def400.inChecks / Math.max(def100.inChecks, 1);
System.out.printf(" Defective: T=100 checks=%d, T=400 checks=%d, growth=%.1fx%n",
def100.inChecks, def400.inChecks, growthRatio);
check("quadratic growth: def400 > 4x def100 (O(T²) evidence)", growthRatio > 4.0);
Result fix100 = runFixed(tasks100);
Result fix400 = runFixed(tasks400);
double fixGrowth = (double) fix400.inChecks / Math.max(fix100.inChecks, 1);
System.out.printf(" Fixed: T=100 checks=%d, T=400 checks=%d, growth=%.1fx%n",
fix100.inChecks, fix400.inChecks, fixGrowth);
check("linear growth: fix400 ≈ 4x fix100 (O(T) evidence)",
fixGrowth >= 3.5 && fixGrowth <= 4.5);
}
// ------ Test 4: mixed producers (some inside, some outside DAG) ------
{
// Task t2 references task t0 (inside), task "external_task" (outside)
List<String> t0inputs = Arrays.asList((String)null);
List<String> t1inputs = Arrays.asList("task0");
List<String> t2inputs = Arrays.asList("task0", "task1", "external_task");
List<Task> tasks = Arrays.asList(
new Task("task0", t0inputs),
new Task("task1", t1inputs),
new Task("task2", t2inputs)
);
Result def = runDefective(tasks);
Result fix = runFixed(tasks);
check("mixed: same specs", specsEqual(def.taskSpecs, fix.taskSpecs));
// task2's "external_task" ref should be in componentInputs (not in DAG)
TaskSpec t2defSpec = def.taskSpecs.get(2);
check("mixed: external_task classified as component_input (defective)",
t2defSpec.componentInputs.containsKey("task2_from_external_task"));
check("mixed: external_task classified as component_input (fixed)",
fix.taskSpecs.get(2).componentInputs.containsKey("task2_from_external_task"));
}
System.out.println("All tests PASS.");
}
}

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# mbedtls-0001: CWE-407 O(S×C) ALPN selection in mbedtls_ssl_parse_alpn_ext
## Severity: MEDIUM
## Location
`library/ssl_tls.c``mbedtls_ssl_parse_alpn_ext()`
## Description
`mbedtls_ssl_parse_alpn_ext()` selects a common ALPN protocol from the client's
`ClientHello` extension. The server has a NULL-terminated list of S configured
protocol names (`ssl->conf->alpn_list`); the client sends a length-prefixed
list of C protocol names.
The current implementation:
```c
/* outer: iterate every server-configured ALPN name (S entries) */
for (const char *const *alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
size_t const alpn_len = strlen(*alpn);
p = protocol_name_list;
/* inner: scan entire client list for each server entry */
while (p < protocol_name_list_end) {
protocol_name_len = *p++;
if (protocol_name_len == alpn_len &&
memcmp(p, *alpn, alpn_len) == 0) { /* O(L) per call */
ssl->alpn_chosen = *alpn;
return 0;
}
p += protocol_name_len;
}
}
```
Total work: O(S × C × L) where L = average protocol name length.
An attacker can send a ClientHello with C distinct ALPN names (the extension
length field allows up to 65535 bytes; at a minimum name length of 1 byte each
that is ~32767 names). Each triggers a full scan of the server's ALPN list.
## Complexity Before Fix
O(S × C × L) per handshake.
## Fix
Build a hash map of the client's ALPN list once (O(C×L)), then look up each
server-preferred entry in O(L) expected. Total: O((C + S) × L).
```c
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8401,6 +8401,10 @@ int mbedtls_ssl_parse_alpn_ext(mbedtls_ssl_context *ssl,
{
const unsigned char *p = buf;
size_t protocol_name_list_len;
+ /* Hash set: store (ptr, len) of each client name; 64-slot open-addressing */
+#define ALPN_HS 64
+ const unsigned char *hs_ptr[ALPN_HS];
+ uint8_t hs_len[ALPN_HS];
const unsigned char *protocol_name_list;
const unsigned char *protocol_name_list_end;
size_t protocol_name_len;
@@ -8441,15 +8445,30 @@ int mbedtls_ssl_parse_alpn_ext(mbedtls_ssl_context *ssl,
p += protocol_name_len;
}
- /* Use our order of preference */
- for (const char *const *alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
- size_t const alpn_len = strlen(*alpn);
- p = protocol_name_list;
- while (p < protocol_name_list_end) {
- protocol_name_len = *p++;
- if (protocol_name_len == alpn_len &&
- memcmp(p, *alpn, alpn_len) == 0) {
- ssl->alpn_chosen = *alpn;
- return 0;
- }
- p += protocol_name_len;
+ /* Build hash set of client-offered names (key = content, len pair) */
+ memset(hs_ptr, 0, sizeof(hs_ptr));
+ memset(hs_len, 0, sizeof(hs_len));
+ p = protocol_name_list;
+ while (p < protocol_name_list_end) {
+ protocol_name_len = *p++;
+ /* FNV-1a hash of content bytes */
+ uint32_t h = 2166136261u;
+ for (size_t k = 0; k < protocol_name_len; k++)
+ h = (h ^ p[k]) * 16777619u;
+ uint32_t slot = h & (ALPN_HS - 1);
+ while (hs_ptr[slot] != NULL &&
+ !(hs_len[slot] == protocol_name_len &&
+ memcmp(hs_ptr[slot], p, protocol_name_len) == 0))
+ slot = (slot + 1) & (ALPN_HS - 1);
+ hs_ptr[slot] = p;
+ hs_len[slot] = (uint8_t) protocol_name_len;
+ p += protocol_name_len;
+ }
+
+ /* Use our order of preference — now O(S) with O(1) lookup per entry */
+ for (const char *const *alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++) {
+ size_t const alpn_len = strlen(*alpn);
+ uint32_t h = 2166136261u;
+ for (size_t k = 0; k < alpn_len; k++)
+ h = (h ^ (unsigned char)(*alpn)[k]) * 16777619u;
+ uint32_t slot = h & (ALPN_HS - 1);
+ while (hs_ptr[slot] != NULL) {
+ if (hs_len[slot] == alpn_len &&
+ memcmp(hs_ptr[slot], *alpn, alpn_len) == 0) {
+ ssl->alpn_chosen = *alpn;
+ return 0;
+ }
+ slot = (slot + 1) & (ALPN_HS - 1);
}
}
+#undef ALPN_HS
```
## Overhead Removed
With S=10 server ALPN names and C=100 client ALPN names: ~1000 memcmp calls
→ ~110 (10× speedup). With C=1000: ~10000 → ~1010 (10× speedup, grows unbounded
with client-controlled C).
## References
- RFC 7301 §3.1 — ALPN extension format (client list is variable-length)
- CWE-407: Inefficient Algorithmic Complexity

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@ -0,0 +1,147 @@
# mbedtls-0002: CWE-407 O(S×C×D) cipher suite selection in ssl_tls12_server.c
## Severity: HIGH
## Location
`library/ssl_tls12_server.c``ssl_parse_client_hello()` cipher matching loop,
`ssl_ciphersuite_match()``mbedtls_ssl_ciphersuite_from_id()`
## Description
During TLS 1.2 server-side ClientHello processing, the server selects a cipher
suite via a nested loop structure:
```c
/* outer: each server-configured cipher suite (S entries) */
for (i = 0; ciphersuites[i] != 0; i++) {
/* inner: each client-offered cipher suite (C entries, 2 bytes each) */
for (j = 0, p = buf + ciph_offset + 2; j < ciph_len; j += 2, p += 2) {
if (MBEDTLS_GET_UINT16_BE(p, 0) != ciphersuites[i])
continue;
/* Called on match — itself O(D) */
if ((ret = ssl_ciphersuite_match(ssl, ciphersuites[i],
&ciphersuite_info)) != 0)
return ret;
}
}
```
`ssl_ciphersuite_match()` calls `mbedtls_ssl_ciphersuite_from_id(suite_id)`,
which performs an O(D) linear scan through the `ciphersuite_definitions[]` array
(D ≈ 70 entries in a typical build).
Total complexity: O(S × C × D) per handshake.
- S = server configured suites (typically 530)
- C = client-offered suites (TLS allows up to 32767 two-byte entries; limit by
ClientHello size of up to 16384 bytes → ≤ 8191 suites)
- D = entries in ciphersuite_definitions (≈ 70)
A client under attacker control can send 8191 cipher suite IDs, each requiring
a full inner scan. With S=20 and D=70, worst case: 20 × 8191 × 70 ≈ 11.5M
operations per handshake.
## Complexity Before Fix
O(S × C × D) per handshake.
## Fix — Two-part
**Part 1**: Replace `mbedtls_ssl_ciphersuite_from_id()` with O(1) lookup via a
precomputed id→index array (built once at startup or compile time).
**Part 2**: Build a hash set of client-offered cipher IDs before the loop.
`ciphersuites[i]` membership in the client set can then be checked in O(1).
Total: O(S + C + S) = O(S + C).
```c
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -1384,6 +1384,22 @@ have_ciphersuite_v2:
got_common_suite = 0;
ciphersuites = ssl->conf->ciphersuite_list;
ciphersuite_info = NULL;
+
+ /* Build hash set of client-offered IDs: 256-slot open-addressing */
+#define CIPH_HS 256
+ uint16_t cli_set[CIPH_HS];
+ memset(cli_set, 0, sizeof(cli_set));
+ {
+ const unsigned char *cp = buf + ciph_offset + 2;
+ for (int jj = 0; jj < (int)ciph_len; jj += 2, cp += 2) {
+ uint16_t cid = (uint16_t) MBEDTLS_GET_UINT16_BE(cp, 0);
+ if (cid == 0) cid = 0xFFFF; /* 0 reserved as empty marker */
+ uint32_t slot = ((uint32_t)cid * 40503u) >> 24; /* mod 256 */
+ while (cli_set[slot] != 0 && cli_set[slot] != cid)
+ slot = (slot + 1) & (CIPH_HS - 1);
+ cli_set[slot] = cid;
+ }
+ }
if (ssl->conf->respect_cli_pref == MBEDTLS_SSL_SRV_CIPHERSUITE_ORDER_CLIENT) {
- for (j = 0, p = buf + ciph_offset + 2; j < ciph_len; j += 2, p += 2) {
- for (i = 0; ciphersuites[i] != 0; i++) {
- if (MBEDTLS_GET_UINT16_BE(p, 0) != ciphersuites[i]) {
- continue;
- }
+ /* client-preference order: iterate client list once */
+ const unsigned char *cp = buf + ciph_offset + 2;
+ for (j = 0; j < (int)ciph_len; j += 2, cp += 2) {
+ uint16_t cid = (uint16_t) MBEDTLS_GET_UINT16_BE(cp, 0);
+ for (i = 0; ciphersuites[i] != 0; i++) {
+ if (ciphersuites[i] != cid)
+ continue;
got_common_suite = 1;
- if ((ret = ssl_ciphersuite_match(ssl, ciphersuites[i],
- &ciphersuite_info)) != 0) {
+ if ((ret = ssl_ciphersuite_match(ssl, cid,
+ &ciphersuite_info)) != 0)
return ret;
- }
- if (ciphersuite_info != NULL) {
+ if (ciphersuite_info != NULL)
goto have_ciphersuite;
- }
}
}
} else {
- for (i = 0; ciphersuites[i] != 0; i++) {
- for (j = 0, p = buf + ciph_offset + 2; j < ciph_len; j += 2, p += 2) {
- if (MBEDTLS_GET_UINT16_BE(p, 0) != ciphersuites[i]) {
- continue;
- }
+ /* server-preference order: iterate server list, O(1) client membership */
+ for (i = 0; ciphersuites[i] != 0; i++) {
+ uint16_t cid = (uint16_t) ciphersuites[i];
+ uint32_t slot = ((uint32_t)cid * 40503u) >> 24;
+ while (cli_set[slot] != 0 && cli_set[slot] != cid)
+ slot = (slot + 1) & (CIPH_HS - 1);
+ if (cli_set[slot] != cid)
+ continue;
got_common_suite = 1;
- if ((ret = ssl_ciphersuite_match(ssl, ciphersuites[i],
- &ciphersuite_info)) != 0) {
+ if ((ret = ssl_ciphersuite_match(ssl, cid,
+ &ciphersuite_info)) != 0)
return ret;
- }
- if (ciphersuite_info != NULL) {
+ if (ciphersuite_info != NULL)
goto have_ciphersuite;
- }
- }
}
}
+#undef CIPH_HS
```
## Overhead Removed
Server-preference mode (most common): O(S × C × D) → O(S + C).
With S=20, C=100, D=70: 140,000 ops → 120 (1167× speedup).
With S=20, C=8191 (max): 11.5M ops → 8211 (1400× speedup).
## References
- RFC 5246 §7.4.1.2 — ClientHello cipher_suites (variable length, client-controlled)
- CWE-407: Inefficient Algorithmic Complexity

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@ -0,0 +1,147 @@
package unit;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
/**
* mbedtls-0001 unit test
*
* Models the O(S×C) ALPN selection in mbedtls_ssl_parse_alpn_ext()
* and the O(S+C) fixed version using a hash map of client names.
*
* Compile: javac -d . MbedTlsAlpnParseTest.java
* Run: java unit.MbedTlsAlpnParseTest
*/
public class MbedTlsAlpnParseTest {
// ------------------------------------------------------------------ //
// Model the defective O(S × C) implementation //
// ------------------------------------------------------------------ //
static String defectiveSelect(String[] serverList, byte[][] clientNames) {
// outer: server preference order
for (String server : serverList) {
byte[] sb = server.getBytes(StandardCharsets.UTF_8);
// inner: full scan of client list with memcmp
for (byte[] client : clientNames) {
if (client.length == sb.length &&
java.util.Arrays.equals(client, sb)) {
return server;
}
}
}
return null;
}
// ------------------------------------------------------------------ //
// Model the fixed O(C + S) implementation using a hash set //
// ------------------------------------------------------------------ //
static String fixedSelect(String[] serverList, byte[][] clientNames) {
// Build hash set of client names O(C)
HashMap<String, Boolean> clientSet = new HashMap<>();
for (byte[] c : clientNames)
clientSet.put(new String(c, StandardCharsets.UTF_8), Boolean.TRUE);
// Iterate server list O(S), each lookup O(1)
for (String server : serverList) {
if (clientSet.containsKey(server))
return server;
}
return null;
}
// ------------------------------------------------------------------ //
// Counting versions //
// ------------------------------------------------------------------ //
static long[] ops = new long[2];
static String defectiveCounting(String[] serverList, byte[][] clientNames) {
for (String server : serverList) {
byte[] sb = server.getBytes(StandardCharsets.UTF_8);
for (byte[] client : clientNames) {
ops[0]++;
if (client.length == sb.length && java.util.Arrays.equals(client, sb))
return server;
}
}
return null;
}
static String fixedCounting(String[] serverList, byte[][] clientNames) {
HashMap<String, Boolean> clientSet = new HashMap<>();
for (byte[] c : clientNames) {
ops[1]++;
clientSet.put(new String(c, StandardCharsets.UTF_8), Boolean.TRUE);
}
for (String server : serverList) {
ops[1]++;
if (clientSet.containsKey(server))
return server;
}
return null;
}
static byte[] name(String s) { return s.getBytes(StandardCharsets.UTF_8); }
// ------------------------------------------------------------------ //
// Tests //
// ------------------------------------------------------------------ //
static int pass = 0, fail = 0;
static void check(String label, boolean cond) {
if (cond) { System.out.println(" PASS " + label); pass++; }
else { System.out.println(" FAIL " + label); fail++; }
}
public static void main(String[] args) {
System.out.println("=== mbedtls-0001: ALPN parse O(S×C) defect ===\n");
String[] serverList = {"h2", "http/1.1", "grpc"};
// Test 1: match on first server preference
byte[][] client1 = {name("h2"), name("http/1.0")};
check("defective: picks h2 (server pref)", "h2".equals(defectiveSelect(serverList, client1)));
check("fixed: picks h2 (server pref)", "h2".equals(fixedSelect(serverList, client1)));
// Test 2: match on second server preference
byte[][] client2 = {name("http/1.0"), name("http/1.1")};
check("defective: picks http/1.1", "http/1.1".equals(defectiveSelect(serverList, client2)));
check("fixed: picks http/1.1", "http/1.1".equals(fixedSelect(serverList, client2)));
// Test 3: no match
byte[][] client3 = {name("ftp"), name("smtp")};
check("defective: no match → null", defectiveSelect(serverList, client3) == null);
check("fixed: no match → null", fixedSelect(serverList, client3) == null);
// Test 4: server preference wins (h2 beats http/1.1 even if client listed it second)
byte[][] client4 = {name("http/1.1"), name("h2")};
check("defective: server-order preference",
"h2".equals(defectiveSelect(serverList, client4)));
check("fixed: server-order preference",
"h2".equals(fixedSelect(serverList, client4)));
// Test 5: complexity adversarial input
int S = 10;
int C = 500;
String[] bigServer = new String[S];
for (int i = 0; i < S; i++) bigServer[i] = "proto-server-" + i;
byte[][] bigClient = new byte[C][];
for (int i = 0; i < C - 1; i++) bigClient[i] = name("proto-client-" + i);
bigClient[C - 1] = name(bigServer[S - 1]); // match at last server position
ops[0] = 0; ops[1] = 0;
String rd = defectiveCounting(bigServer, bigClient);
String rf = fixedCounting(bigServer, bigClient);
System.out.println("\n Complexity comparison (S=" + S + ", C=" + C + "):");
System.out.println(" Defective ops: " + ops[0]);
System.out.println(" Fixed ops: " + ops[1]);
System.out.printf(" Speedup: %.1fx%n", (double) ops[0] / ops[1]);
check("defective and fixed agree", java.util.Objects.equals(rd, rf));
check("defective ops > 4x fixed ops", ops[0] > 4 * ops[1]);
System.out.println("\n--- " + (pass + fail) + " tests: " + pass + " passed, " + fail + " failed ---");
if (fail > 0) System.exit(1);
}
}

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@ -0,0 +1,182 @@
package unit;
import java.util.HashMap;
/**
* mbedtls-0002 unit test
*
* Models the O(S×C×D) cipher suite selection in ssl_tls12_server.c
* and the O(S+C) fixed version using a hash set of client-offered IDs.
*
* Compile: javac -d . MbedTlsCipherSelectTest.java
* Run: java unit.MbedTlsCipherSelectTest
*/
public class MbedTlsCipherSelectTest {
// Simulated ciphersuite_definitions table (D entries)
static final int[] CIPHER_DEFINITIONS;
static {
// Representative TLS 1.2 cipher suite IDs (a subset of the ~70 in mbedTLS)
CIPHER_DEFINITIONS = new int[]{
0xC02B, // TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
0xC02C, // TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
0xC02F, // TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
0xC030, // TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
0xCCA9, // TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
0xCCA8, // TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
0xC009, // TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
0xC013, // TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
0x002F, // TLS_RSA_WITH_AES_128_CBC_SHA
0x0035, // TLS_RSA_WITH_AES_256_CBC_SHA
0x003C, // TLS_RSA_WITH_AES_128_CBC_SHA256
0x003D, // TLS_RSA_WITH_AES_256_CBC_SHA256
0x009C, // TLS_RSA_WITH_AES_128_GCM_SHA256
0x009D, // TLS_RSA_WITH_AES_256_GCM_SHA384
0xC023, // TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
0xC024, // TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
};
}
// O(D) linear lookup mirrors mbedtls_ssl_ciphersuite_from_id
static boolean cipherDefinitionExists(int id) {
for (int def : CIPHER_DEFINITIONS) {
if (def == id) return true;
}
return false;
}
// ------------------------------------------------------------------ //
// DEFECTIVE: O(S × C × D) //
// server-preference mode (most common): for each server suite, //
// scan all client suites; on match, call ciphersuite_match (O(D)) //
// ------------------------------------------------------------------ //
static int defectiveSelect(int[] serverSuites, int[] clientSuites) {
for (int sid : serverSuites) {
for (int cid : clientSuites) {
if (cid == sid) {
// ssl_ciphersuite_match calls mbedtls_ssl_ciphersuite_from_id (O(D))
if (cipherDefinitionExists(sid))
return sid;
}
}
}
return -1;
}
// ------------------------------------------------------------------ //
// FIXED: O(S + C) hash set of client IDs, O(1) membership test //
// ------------------------------------------------------------------ //
static int fixedSelect(int[] serverSuites, int[] clientSuites) {
// Build hash set of client IDs O(C)
HashMap<Integer, Boolean> clientSet = new HashMap<>();
for (int cid : clientSuites) clientSet.put(cid, Boolean.TRUE);
// Iterate server list O(S), each lookup O(1)
for (int sid : serverSuites) {
if (clientSet.containsKey(sid)) {
// ciphersuite_match still needed, but only on actual matches
if (cipherDefinitionExists(sid))
return sid;
}
}
return -1;
}
// ------------------------------------------------------------------ //
// Counting versions //
// ------------------------------------------------------------------ //
static long[] ops = new long[2]; // [defective, fixed]
static int defectiveCounting(int[] server, int[] client) {
for (int sid : server) {
for (int cid : client) {
ops[0]++; // inner comparison
if (cid == sid) {
for (int def : CIPHER_DEFINITIONS) {
ops[0]++; // O(D) lookup
if (def == sid) return sid;
}
}
}
}
return -1;
}
static int fixedCounting(int[] server, int[] client) {
HashMap<Integer, Boolean> cs = new HashMap<>();
for (int cid : client) { ops[1]++; cs.put(cid, Boolean.TRUE); }
for (int sid : server) {
ops[1]++;
if (cs.containsKey(sid)) {
for (int def : CIPHER_DEFINITIONS) {
ops[1]++;
if (def == sid) return sid;
}
}
}
return -1;
}
static int pass = 0, fail = 0;
static void check(String label, boolean cond) {
if (cond) { System.out.println(" PASS " + label); pass++; }
else { System.out.println(" FAIL " + label); fail++; }
}
public static void main(String[] args) {
System.out.println("=== mbedtls-0002: TLS 1.2 cipher selection O(S×C×D) defect ===\n");
// Server prefers ECDHE-ECDSA-AES128-GCM, then ECDHE-RSA-AES128-GCM
int[] serverList = {0xC02B, 0xC02F, 0x002F};
// Test 1: first server suite matches
int[] client1 = {0xC02F, 0xC02B, 0x0000};
check("defective: picks server-preferred 0xC02B",
defectiveSelect(serverList, client1) == 0xC02B);
check("fixed: picks server-preferred 0xC02B",
fixedSelect(serverList, client1) == 0xC02B);
// Test 2: only second server suite matches
int[] client2 = {0xC02F, 0x0035};
check("defective: picks 0xC02F (second server entry)",
defectiveSelect(serverList, client2) == 0xC02F);
check("fixed: picks 0xC02F (second server entry)",
fixedSelect(serverList, client2) == 0xC02F);
// Test 3: no common suite
int[] client3 = {0x0004, 0x0005, 0x000A};
check("defective: no match → -1", defectiveSelect(serverList, client3) == -1);
check("fixed: no match → -1", fixedSelect(serverList, client3) == -1);
// Test 4: complexity adversarial large client list with no match
// (no-match is worst case: defective must scan all S*C combinations)
int S = 20;
int C = 300;
int D = CIPHER_DEFINITIONS.length;
int[] bigServer = new int[S];
for (int i = 0; i < S; i++)
bigServer[i] = 0x1000 + i; // server suites NOT in CIPHER_DEFINITIONS
// client sends C unknown IDs no match, full O(S*C) scan
int[] bigClient = new int[C];
for (int i = 0; i < C; i++) bigClient[i] = 0x9000 + i;
ops[0] = 0; ops[1] = 0;
int rd = defectiveCounting(bigServer, bigClient);
int rf = fixedCounting(bigServer, bigClient);
System.out.println("\n Complexity comparison (S=" + S + ", C=" + C + ", D=" + D + ", no-match):");
System.out.println(" Defective ops: " + ops[0] + " (expected ~" + ((long)S * C) + ")");
System.out.println(" Fixed ops: " + ops[1] + " (expected ~" + (S + C) + ")");
System.out.printf(" Speedup: %.1fx%n", (double) ops[0] / ops[1]);
check("defective and fixed agree on result (both -1)", rd == rf && rd == -1);
check("defective ops > 5x fixed ops (quadratic vs linear)",
ops[0] > 5 * ops[1]);
System.out.println("\n--- " + (pass + fail) + " tests: " + pass + " passed, " + fail + " failed ---");
if (fail > 0) System.exit(1);
}
}

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# metaflow-0001 — O(N²) Graph Traversal: list.remove() and list membership in _traverse_graph
**Severity:** HIGH
**Complexity:** O(N²) → O(N)
**CWE:** CWE-407 (Algorithmic Complexity)
## Affected File
| File | Lines | Notes |
|------|-------|-------|
| `metaflow/graph.py` | 300340 | `_traverse_graph` inner `traverse()` function |
## Defective Code
### `metaflow/graph.py` lines 300340
```python
def traverse(node, seen, split_parents, split_branches):
add_split_branch = False
try:
self.sorted_nodes.remove(node.name) # ← O(N) scan of list every call
except ValueError:
pass
self.sorted_nodes.append(node.name)
...
for n in node.out_funcs:
if n not in seen: # ← O(N) scan of list per edge
if n in self:
child = self[n]
child.in_funcs.add(node.name)
traverse(
child,
seen + [n], # ← new list allocation per recursion
split_parents,
split_branches + ([n] if add_split_branch else []),
)
```
**Two interlocking defects:**
1. `self.sorted_nodes.remove(node.name)` — O(N) linear scan of the growing `sorted_nodes` list,
called once per node visit. For a flow with N steps, this is O(N) scans × O(N) visits = **O(N²)**.
2. `if n not in seen``seen` is a Python list passed down through recursion. For a linear chain
of N steps, checking `n not in seen` at depth D costs O(D). Summed over all depths: O(N²).
Additionally, `seen + [n]` allocates a new list at every recursive call.
## Fix
Replace `sorted_nodes` (list) with a `dict` for O(1) membership/remove, and replace the `seen`
list with a `set`:
```python
def _traverse_graph(self):
sorted_nodes_set = {} # dict preserves insertion order in Python 3.7+
seen_set = set()
def traverse(node, split_parents, split_branches):
add_split_branch = False
# O(1) remove + append via ordered dict
sorted_nodes_set.pop(node.name, None)
sorted_nodes_set[node.name] = True
if node.type in ("split", "foreach"):
node.split_parents = split_parents
node.split_branches = split_branches
add_split_branch = True
split_parents = split_parents + [node.name]
elif node.type == "split-switch":
node.split_parents = split_parents
node.split_branches = split_branches
elif node.type == "join":
if split_parents:
self[split_parents[-1]].matching_join = node.name
node.split_parents = split_parents
node.split_branches = split_branches[:-1]
split_parents = split_parents[:-1]
split_branches = split_branches[:-1]
else:
node.split_parents = split_parents
node.split_branches = split_branches
for n in node.out_funcs:
if n not in seen_set: # O(1) set lookup
if n in self:
seen_set.add(n)
child = self[n]
child.in_funcs.add(node.name)
traverse(
child,
split_parents,
split_branches + ([n] if add_split_branch else []),
)
if "start" in self:
seen_set.add("start")
traverse(self["start"], [], [])
self.sorted_nodes = list(sorted_nodes_set.keys())
for node in self.nodes.values():
node.in_funcs = sorted(node.in_funcs)
```
## Complexity
| Metric | Before | After |
|--------|--------|-------|
| `sorted_nodes.remove` per node | O(N) | O(1) |
| `n not in seen` per edge | O(depth) | O(1) |
| `seen + [n]` allocation | O(depth) | eliminated |
| Total traverse | O(N²) | O(N + E) |
## Impact
Every `@step`-decorated Metaflow flow compiles its DAG at startup via `FlowGraph._traverse_graph`.
For flows with many steps (e.g. 500-step ML training pipelines), the quadratic traversal adds
measurable startup latency and proportionally worse latency in any system that repeatedly
re-parses flow definitions (live-reloading, CI validation pipelines).

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@ -0,0 +1,262 @@
package unit;
import java.util.*;
/**
* metaflow-0001 O(N²) graph traversal in FlowGraph._traverse_graph()
*
* Simulates the defective pattern from:
* metaflow/graph.py lines 300-340
*
* Defect 1: sorted_nodes.remove(node.name) is O(N) inside a DFS that visits N nodes O(N²)
* Defect 2: seen is a List, so `n not in seen` is O(depth) per edge O(N²) summed over all edges
*
* Fix 1: Use a LinkedHashMap (insertion-ordered map) for sorted_nodes O(1) remove/put
* Fix 2: Use a HashSet for seen O(1) membership test
*
* The op-count measures "list scans": how many elements were examined across all
* remove() and `contains()` calls. In the defective version this is O(N²);
* in the fixed version it is O(N + E).
*/
public class MetaflowGraphAlgorithm {
static void check(String desc, boolean cond) {
System.out.println((cond ? "PASS" : "FAIL") + ": " + desc);
if (!cond) throw new AssertionError("FAIL: " + desc);
}
// Simulates a DAGNode with successors
static class Node {
final String name;
final List<String> outFuncs = new ArrayList<>();
Node(String name) { this.name = name; }
void addEdge(String target) { outFuncs.add(target); }
}
// Result from traversal
static class Result {
final List<String> sortedNodes;
final long listScans;
Result(List<String> sortedNodes, long listScans) {
this.sortedNodes = sortedNodes;
this.listScans = listScans;
}
}
// -----------------------------------------------------------------------
// DEFECTIVE: sorted_nodes is an ArrayList, seen is a List
// -----------------------------------------------------------------------
static long defectiveScans;
static void traverseDefective(
String name,
Map<String, Node> nodes,
List<String> sortedNodes,
List<String> seen) {
// O(N) scan: remove from list
int sizeBefore = sortedNodes.size();
sortedNodes.remove(name);
defectiveScans += sizeBefore; // counted even if not found
sortedNodes.add(name);
for (String n : nodes.get(name).outFuncs) {
// O(depth) scan: check membership
defectiveScans += seen.size();
if (!seen.contains(n)) {
if (nodes.containsKey(n)) {
List<String> newSeen = new ArrayList<>(seen);
newSeen.add(n);
traverseDefective(n, nodes, sortedNodes, newSeen);
}
}
}
}
static Result runDefective(Map<String, Node> nodes, String start) {
defectiveScans = 0;
List<String> sortedNodes = new ArrayList<>();
List<String> seen = new ArrayList<>();
seen.add(start);
traverseDefective(start, nodes, sortedNodes, seen);
return new Result(sortedNodes, defectiveScans);
}
// -----------------------------------------------------------------------
// FIXED: sorted_nodes is a LinkedHashMap, seen is a HashSet
// -----------------------------------------------------------------------
static long fixedScans;
static void traverseFixed(
String name,
Map<String, Node> nodes,
LinkedHashMap<String, Boolean> sortedNodes,
Set<String> seen) {
// O(1) remove + put
sortedNodes.remove(name); // no scan needed
sortedNodes.put(name, true);
fixedScans += 1; // count the O(1) hash op
for (String n : nodes.get(name).outFuncs) {
// O(1) hash lookup
fixedScans += 1;
if (!seen.contains(n)) {
if (nodes.containsKey(n)) {
seen.add(n);
traverseFixed(n, nodes, sortedNodes, seen);
}
}
}
}
static Result runFixed(Map<String, Node> nodes, String start) {
fixedScans = 0;
LinkedHashMap<String, Boolean> sortedNodes = new LinkedHashMap<>();
Set<String> seen = new HashSet<>();
seen.add(start);
traverseFixed(start, nodes, sortedNodes, seen);
return new Result(new ArrayList<>(sortedNodes.keySet()), fixedScans);
}
// -----------------------------------------------------------------------
// Build a linear chain: start s1 s2 ... sN end
// -----------------------------------------------------------------------
static Map<String, Node> linearChain(int n) {
Map<String, Node> nodes = new LinkedHashMap<>();
Node start = new Node("start");
nodes.put("start", start);
String prev = "start";
for (int i = 1; i <= n; i++) {
String name = "step" + i;
Node node = new Node(name);
nodes.put(name, node);
nodes.get(prev).addEdge(name);
prev = name;
}
Node end = new Node("end");
nodes.put("end", end);
nodes.get(prev).addEdge("end");
return nodes;
}
// -----------------------------------------------------------------------
// Build a diamond DAG (wide split): start N parallel join end
// -----------------------------------------------------------------------
static Map<String, Node> diamondDAG(int n) {
Map<String, Node> nodes = new LinkedHashMap<>();
Node start = new Node("start");
nodes.put("start", start);
Node join = new Node("join");
nodes.put("join", join);
for (int i = 0; i < n; i++) {
String name = "branch" + i;
Node b = new Node(name);
nodes.put(name, b);
start.addEdge(name);
b.addEdge("join");
}
Node end = new Node("end");
nodes.put("end", end);
join.addEdge("end");
return nodes;
}
public static void main(String[] args) {
System.out.println("=== metaflow-0001: O(N²) graph traverse in FlowGraph._traverse_graph ===");
// ------ Test 1: correctness on small linear chain ------
{
Map<String, Node> nodes = linearChain(4);
Result def = runDefective(nodes, "start");
Result fix = runFixed(nodes, "start");
check("linear-4: defective produces correct topo order",
def.sortedNodes.equals(Arrays.asList("start","step1","step2","step3","step4","end")));
check("linear-4: fixed produces correct topo order",
fix.sortedNodes.equals(Arrays.asList("start","step1","step2","step3","step4","end")));
check("linear-4: fixed uses fewer scans",
fix.listScans <= def.listScans);
}
// ------ Test 2: O(N²) vs O(N) scaling on linear chain ------
{
int N = 200;
Map<String, Node> nodes = linearChain(N);
Result def200 = runDefective(nodes, "start");
Result fix200 = runFixed(nodes, "start");
// Defective: remove scans grow as 0+1+2+...+N N²/2; seen grows too
// Fixed: each op is O(1)
long ratio = def200.listScans / Math.max(fix200.listScans, 1);
System.out.printf(" N=%d: defective scans=%d, fixed scans=%d, ratio=%dx%n",
N, def200.listScans, fix200.listScans, ratio);
check("linear-200: defective scan count > 1000 (quadratic evidence)",
def200.listScans > 1_000);
check("linear-200: fixed scan count <= 2*(N+2) (linear)",
fix200.listScans <= 2L * (N + 2));
check("linear-200: ratio >= 10x",
ratio >= 10);
// Verify both produce same sorted order
check("linear-200: same sorted order",
def200.sortedNodes.equals(fix200.sortedNodes));
}
// ------ Test 3: diamond DAG correctness ------
{
int N = 50;
Map<String, Node> nodes = diamondDAG(N);
Result def = runDefective(nodes, "start");
Result fix = runFixed(nodes, "start");
// start must be first in both versions, all nodes visited, same count
check("diamond-50: start is first (defective)", def.sortedNodes.get(0).equals("start"));
check("diamond-50: start is first (fixed)", fix.sortedNodes.get(0).equals("start"));
// Both must contain all N+3 nodes: start, N branches, join, end
check("diamond-50: defective visits all nodes", def.sortedNodes.size() == N + 3);
check("diamond-50: fixed visits all nodes", fix.sortedNodes.size() == N + 3);
// join must appear before end in both (topological constraint)
int defJoinIdx = def.sortedNodes.indexOf("join");
int defEndIdx = def.sortedNodes.indexOf("end");
int fixJoinIdx = fix.sortedNodes.indexOf("join");
int fixEndIdx = fix.sortedNodes.indexOf("end");
check("diamond-50: join before end (defective)", defJoinIdx < defEndIdx);
check("diamond-50: join before end (fixed)", fixJoinIdx < fixEndIdx);
// all branches are present in fixed output
check("diamond-50: fixed contains branch0", fix.sortedNodes.contains("branch0"));
check("diamond-50: fixed contains branch" + (N-1), fix.sortedNodes.contains("branch" + (N-1)));
}
// ------ Test 4: large chain quadratic cost is clear ------
{
int N = 400;
Map<String, Node> small = linearChain(N / 4);
Map<String, Node> large = linearChain(N);
Result defSmall = runDefective(small, "start");
Result defLarge = runDefective(large, "start");
// Quadratic: scans should grow roughly 16× (4× nodes 16× scans)
double growthRatio = (double) defLarge.listScans / Math.max(defSmall.listScans, 1);
System.out.printf(" Defective: N=%d scans=%d, N=%d scans=%d, growth=%.1fx%n",
N/4, defSmall.listScans, N, defLarge.listScans, growthRatio);
check("quadratic growth: defLarge.scans > 4x defSmall.scans (O(N²) evidence)",
growthRatio > 4.0);
Result fixSmall = runFixed(small, "start");
Result fixLarge = runFixed(large, "start");
double fixGrowthRatio = (double) fixLarge.listScans / Math.max(fixSmall.listScans, 1);
System.out.printf(" Fixed: N=%d scans=%d, N=%d scans=%d, growth=%.1fx%n",
N/4, fixSmall.listScans, N, fixLarge.listScans, fixGrowthRatio);
check("linear growth: fixLarge.scans < 5x fixSmall.scans (O(N) evidence)",
fixGrowthRatio < 5.0);
}
System.out.println("All tests PASS.");
}
}

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# MLflow CWE-407 Scan — CLEAN
**Scan date:** 2026-03-27
**Verdict:** No CWE-407 defects found
**Severity:** N/A
## Scope
| Path | What was checked |
|------|-----------------|
| `mlflow/tracking/` | Experiment/run tracking, fluent API |
| `mlflow/store/tracking/file_store.py` | File-based tracking store, run search |
| `mlflow/store/tracking/sqlalchemy_store.py` | SQL tracking store, log_batch, tag ops |
| `mlflow/store/model_registry/` | Model registry stores |
| `mlflow/utils/search_utils.py` | SearchUtils.filter for runs/experiments |
| `mlflow/projects/_project_spec.py` | Project step dependency resolution |
## Analysis
**SearchUtils.filter** (`search_utils.py:763772`): Uses `run.data.tags.get(key)` and
`run.data.params.get(key)` — both are dict lookups, O(1). No list membership in inner loops.
**`_log_params`** (`sqlalchemy_store.py:1631`): Uses `existing_params = {p.key: p.value for p in run.params}`
(dict) before the loop — O(1) key check per param. The error-path at line 1616 does a linear
scan but only executes on IntegrityError (rare, not on the hot path).
**`record_logged_model`** (`sqlalchemy_store.py:1961`): `[t for t in run.tags if t.key == MLFLOW_LOGGED_MODELS]`
is O(T) over tags for a single call — not inside a loop, no quadratic composition.
**`_set_tags`** (`sqlalchemy_store.py:1762`): Uses `.in_([t.key for t in tags])` — SQL-level bulk
operation, not Python list membership in a loop.
**Projects** (`_project_spec.py`): Step dependency resolution uses dict-based parameter lookups,
no list membership inside loops.
## Conclusion
MLflow's hot paths use dicts, SQL set operations, and SQLAlchemy queries for all bulk lookups.
No CWE-407 (O(N) linear membership inside a loop) defects found.

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# open3d-0001: ValidatePoseGraphConnectivity — O(V²×E) std::find on component vector inside BFS×edge scan
## Location
`cpp/open3d/pipelines/registration/GlobalOptimization.cpp` lines 367404
Repository: https://github.com/isl-org/Open3D
## Severity
**HIGH** — Called twice during pose graph validation (for all edges, then certain edges only) before every global optimization run. With V nodes and E edges in the pose graph, the BFS expands V nodes, each scanning all E edges, and for each adjacent node does a O(V) `std::find` on `component`. Total: O(V²×E). For large 3D reconstruction datasets (thousands of frames/cameras), this is a significant pre-optimization bottleneck.
## Complexity
- Before: O(V² × E) — std::find on `component` (O(V)) called inside while-loop (V iters) × edge-scan (E iters)
- After: O(V × E) — O(1) unordered_set membership replaces the O(V) linear scan
## Defective Code
```cpp
// GlobalOptimization.cpp:367-404
static bool ValidatePoseGraphConnectivity(const PoseGraph &pose_graph,
bool ignore_uncertain_edges = false) {
size_t n_nodes = pose_graph.nodes_.size();
size_t n_edges = pose_graph.edges_.size();
std::vector<int> nodes_to_explore{};
std::vector<int> component{}; // membership tracked as a vector
if (n_nodes > 0) {
nodes_to_explore.push_back(0);
component.push_back(0);
}
while (!nodes_to_explore.empty()) {
int i = nodes_to_explore.back();
nodes_to_explore.pop_back();
for (size_t j = 0; j < n_edges; j++) {
const PoseGraphEdge &t = pose_graph.edges_[j];
if (ignore_uncertain_edges && t.uncertain_) continue;
int adjacent_node{-1};
if (t.source_node_id_ == i) adjacent_node = t.target_node_id_;
else if (t.target_node_id_ == i) adjacent_node = t.source_node_id_;
if (adjacent_node != -1) {
auto find_result = std::find(component.begin(), component.end(),
adjacent_node); // O(V) per call
if (find_result == component.end()) {
nodes_to_explore.push_back(adjacent_node);
component.push_back(adjacent_node);
}
}
}
}
return component.size() == n_nodes;
}
```
**Problem:** `component` is a `std::vector<int>`. The `std::find` membership check is O(V)
called for every edge of every explored node. BFS visits V nodes, each scanning E edges,
each doing O(V) find → O(V²×E) total.
## Fixed Code
```cpp
static bool ValidatePoseGraphConnectivity(const PoseGraph &pose_graph,
bool ignore_uncertain_edges = false) {
size_t n_nodes = pose_graph.nodes_.size();
size_t n_edges = pose_graph.edges_.size();
std::vector<int> nodes_to_explore{};
std::unordered_set<int> component_set; // O(1) membership
if (n_nodes > 0) {
nodes_to_explore.push_back(0);
component_set.insert(0);
}
while (!nodes_to_explore.empty()) {
int i = nodes_to_explore.back();
nodes_to_explore.pop_back();
for (size_t j = 0; j < n_edges; j++) {
const PoseGraphEdge &t = pose_graph.edges_[j];
if (ignore_uncertain_edges && t.uncertain_) continue;
int adjacent_node{-1};
if (t.source_node_id_ == i) adjacent_node = t.target_node_id_;
else if (t.target_node_id_ == i) adjacent_node = t.source_node_id_;
if (adjacent_node != -1) {
if (component_set.insert(adjacent_node).second) { // O(1)
nodes_to_explore.push_back(adjacent_node);
}
}
}
}
return component_set.size() == n_nodes;
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(V²×E) → O(V×E)

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# open3d-0002: RandomSampler::operator() — O(S²) std::find on samples vector inside rejection-sampling loop
## Location
`cpp/open3d/geometry/PointCloudSegmentation.cpp` lines 3146
Repository: https://github.com/isl-org/Open3D
## Severity
**MEDIUM** — Called `num_iterations` times (typically 1001000) during RANSAC plane segmentation. Each call uses rejection sampling with std::find on the growing `samples` vector. For a sample_size S, each call is O(S²) expected. The developer comment acknowledges "Well, this is slow." Total: O(num_iterations × S²). For ransac_n=3 (default), S=3 and impact is small, but for custom higher ransac_n values the overhead is measurable.
## Complexity
- Before: O(S²) per sample call — std::find on growing `samples` vector inside while loop
- After: O(S) per sample call — unordered_set for O(1) duplicate detection
## Defective Code
```cpp
// PointCloudSegmentation.cpp:31-46
std::vector<T> operator()(size_t sample_size) {
std::vector<T> samples;
samples.reserve(sample_size);
size_t valid_sample = 0;
while (valid_sample < sample_size) {
const size_t idx = utility::random::RandUint32() % total_size_;
// Well, this is slow. But typically the sample_size is small.
if (std::find(samples.begin(), samples.end(), idx) ==
samples.end()) {
samples.push_back(idx);
valid_sample++;
}
}
return samples;
}
```
**Problem:** `std::find` on `samples` is O(valid_sample) inside the while loop. As
`valid_sample` grows from 0 to `sample_size`, the total work is 0+1+2+...+(S-1) = O(S²).
Called `num_iterations` times, total is O(num_iterations × S²).
## Fixed Code
```cpp
std::vector<T> operator()(size_t sample_size) {
std::vector<T> samples;
samples.reserve(sample_size);
std::unordered_set<T> seen;
seen.reserve(sample_size);
while (samples.size() < sample_size) {
const size_t idx = utility::random::RandUint32() % total_size_;
if (seen.insert(idx).second) { // O(1) duplicate detection
samples.push_back(idx);
}
}
return samples;
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(S²) → O(S) per sample call

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package unit;
import java.util.*;
/**
* Unit test for open3d-0001: ValidatePoseGraphConnectivity O(V²×E) O(V×E)
*
* Simulates Open3D GlobalOptimization.cpp connectivity BFS:
* Defective: std::find on component vector inside while-loop × edge scan
* Fixed: unordered_set membership O(1) replaces the O(V) linear scan
*
* Compile: javac -d . PoseGraphConnectivityAlgorithm.java
* Run: java -ea unit.PoseGraphConnectivityAlgorithm
*/
public class PoseGraphConnectivityAlgorithm {
static class PoseGraphEdge {
final int source;
final int target;
final boolean uncertain;
PoseGraphEdge(int src, int tgt, boolean uncertain) {
source = src; target = tgt; this.uncertain = uncertain;
}
}
static class PoseGraph {
final int nNodes;
final List<PoseGraphEdge> edges;
PoseGraph(int nNodes, List<PoseGraphEdge> edges) {
this.nNodes = nNodes; this.edges = edges;
}
}
// defective implementation
static boolean defectiveValidateConnectivity(PoseGraph pg, boolean ignoreUncertain) {
int nNodes = pg.nNodes;
if (nNodes == 0) return true;
List<Integer> toExplore = new ArrayList<>();
List<Integer> component = new ArrayList<>(); // O(V) membership
toExplore.add(0);
component.add(0);
while (!toExplore.isEmpty()) {
int i = toExplore.remove(toExplore.size() - 1);
for (PoseGraphEdge e : pg.edges) {
if (ignoreUncertain && e.uncertain) continue;
int adj = -1;
if (e.source == i) adj = e.target;
else if (e.target == i) adj = e.source;
if (adj != -1) {
// O(V) linear scan inside while-loop × edge-scan
boolean found = false;
for (int c : component) if (c == adj) { found = true; break; }
if (!found) {
toExplore.add(adj);
component.add(adj);
}
}
}
}
return component.size() == nNodes;
}
// fixed implementation
static boolean fixedValidateConnectivity(PoseGraph pg, boolean ignoreUncertain) {
int nNodes = pg.nNodes;
if (nNodes == 0) return true;
List<Integer> toExplore = new ArrayList<>();
Set<Integer> componentSet = new HashSet<>(); // O(1) membership
toExplore.add(0);
componentSet.add(0);
while (!toExplore.isEmpty()) {
int i = toExplore.remove(toExplore.size() - 1);
for (PoseGraphEdge e : pg.edges) {
if (ignoreUncertain && e.uncertain) continue;
int adj = -1;
if (e.source == i) adj = e.target;
else if (e.target == i) adj = e.source;
if (adj != -1) {
if (componentSet.add(adj)) { // O(1) insert+dedup
toExplore.add(adj);
}
}
}
}
return componentSet.size() == nNodes;
}
// graph builders
/** Linear chain: 0-1-2-...-n-1 */
static PoseGraph buildChain(int n) {
List<PoseGraphEdge> edges = new ArrayList<>();
for (int i = 0; i < n - 1; i++) edges.add(new PoseGraphEdge(i, i + 1, false));
return new PoseGraph(n, edges);
}
/** Complete graph: all pairs connected */
static PoseGraph buildComplete(int n) {
List<PoseGraphEdge> edges = new ArrayList<>();
for (int i = 0; i < n; i++)
for (int j = i + 1; j < n; j++) edges.add(new PoseGraphEdge(i, j, false));
return new PoseGraph(n, edges);
}
/** Disconnected: two isolated cliques */
static PoseGraph buildDisconnected(int n) {
List<PoseGraphEdge> edges = new ArrayList<>();
int half = n / 2;
for (int i = 0; i < half - 1; i++) edges.add(new PoseGraphEdge(i, i + 1, false));
for (int i = half; i < n - 1; i++) edges.add(new PoseGraphEdge(i, i + 1, false));
return new PoseGraph(n, edges);
}
/** Certain-edge-only graph: some edges marked uncertain */
static PoseGraph buildMixed(int n, double uncertainFraction) {
List<PoseGraphEdge> edges = new ArrayList<>();
// Build a chain where every other edge is uncertain
for (int i = 0; i < n - 1; i++) {
boolean uncertain = (i % 2 == 1);
edges.add(new PoseGraphEdge(i, i + 1, uncertain));
}
return new PoseGraph(n, edges);
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
public static void main(String[] args) {
// Test 1: empty graph connected (vacuously)
{
PoseGraph pg = new PoseGraph(0, Collections.emptyList());
assertTrue("empty-defective", defectiveValidateConnectivity(pg, false));
assertTrue("empty-fixed", fixedValidateConnectivity(pg, false));
}
// Test 2: single node connected
{
PoseGraph pg = new PoseGraph(1, Collections.emptyList());
assertTrue("single-node-defective", defectiveValidateConnectivity(pg, false));
assertTrue("single-node-fixed", fixedValidateConnectivity(pg, false));
}
// Test 3: chain of 5 connected
{
PoseGraph pg = buildChain(5);
assertTrue("chain5-defective", defectiveValidateConnectivity(pg, false));
assertTrue("chain5-fixed", fixedValidateConnectivity(pg, false));
}
// Test 4: complete graph of 6 connected
{
PoseGraph pg = buildComplete(6);
assertTrue("complete6-defective", defectiveValidateConnectivity(pg, false));
assertTrue("complete6-fixed", fixedValidateConnectivity(pg, false));
}
// Test 5: disconnected not connected
{
PoseGraph pg = buildDisconnected(6);
assertTrue("disconnected6-defective", !defectiveValidateConnectivity(pg, false));
assertTrue("disconnected6-fixed", !fixedValidateConnectivity(pg, false));
}
// Test 6: mixed uncertain edges chain connected via uncertain edges only
{
// 4 nodes: 0--1(certain) 1--2(uncertain) 2--3(certain)
List<PoseGraphEdge> edges = Arrays.asList(
new PoseGraphEdge(0, 1, false),
new PoseGraphEdge(1, 2, true),
new PoseGraphEdge(2, 3, false));
PoseGraph pg = new PoseGraph(4, edges);
// Ignoring uncertain: 0-1 certain, 2-3 certain, but 1-2 uncertain not connected
assertTrue("uncertain-ignore-defective", !defectiveValidateConnectivity(pg, true));
assertTrue("uncertain-ignore-fixed", !fixedValidateConnectivity(pg, true));
// Not ignoring uncertain: all connected
assertTrue("uncertain-include-defective", defectiveValidateConnectivity(pg, false));
assertTrue("uncertain-include-fixed", fixedValidateConnectivity(pg, false));
}
// Test 7: both implementations agree on random graph
{
Random rng = new Random(42);
int V = 30, extraEdges = 60;
List<PoseGraphEdge> edges = new ArrayList<>();
for (int i = 0; i < V - 1; i++) edges.add(new PoseGraphEdge(i, i + 1, false));
for (int i = 0; i < extraEdges; i++) {
int a = rng.nextInt(V), b = rng.nextInt(V);
edges.add(new PoseGraphEdge(a, b, rng.nextBoolean()));
}
PoseGraph pg = new PoseGraph(V, edges);
boolean d = defectiveValidateConnectivity(pg, false);
boolean f = fixedValidateConnectivity(pg, false);
assertTrue("random-graph-agree", d == f);
assertTrue("random-graph-connected", f); // chain ensures connectivity
}
// Test 8: performance component membership check isolated at V=1000
// Builds a large component list, then simulates the find-or-add operation
{
int V = 2000;
// Simulate: component grows to V, each element checked V times = O(V²)
long t0 = System.nanoTime();
for (int r = 0; r < 10; r++) {
List<Integer> component = new ArrayList<>(V);
for (int i = 0; i < V; i++) {
// defective: linear scan to check if i already in component
boolean found = false;
for (int c : component) if (c == i) { found = true; break; }
if (!found) component.add(i);
}
}
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
for (int r = 0; r < 10; r++) {
Set<Integer> componentSet = new HashSet<>(V * 2);
List<Integer> componentList = new ArrayList<>(V);
for (int i = 0; i < V; i++) {
// fixed: O(1) set insert
if (componentSet.add(i)) componentList.add(i);
}
}
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf component-dedup V=%d: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
V, tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-speedup", ratio > 5.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

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package unit;
import java.util.*;
/**
* Unit test for open3d-0002: RandomSampler::operator() O(S²) O(S)
*
* Simulates Open3D PointCloudSegmentation.cpp RandomSampler:
* Defective: std::find on growing samples vector inside rejection-sampling while loop
* Fixed: unordered_set for O(1) duplicate detection
*
* Compile: javac -d . RansacSamplerAlgorithm.java
* Run: java -ea unit.RansacSamplerAlgorithm
*/
public class RansacSamplerAlgorithm {
// defective implementation
/** Returns sampleSize unique indices in [0, totalSize), using O(S²) rejection sampling */
static List<Integer> defectiveSample(int totalSize, int sampleSize, Random rng) {
List<Integer> samples = new ArrayList<>(sampleSize);
while (samples.size() < sampleSize) {
int idx = rng.nextInt(totalSize);
// O(valid_sample) linear scan same as std::find in Open3D
boolean found = false;
for (int s : samples) if (s == idx) { found = true; break; }
if (!found) samples.add(idx);
}
return samples;
}
// fixed implementation
/** Returns sampleSize unique indices in [0, totalSize), using O(S) set-based sampling */
static List<Integer> fixedSample(int totalSize, int sampleSize, Random rng) {
List<Integer> samples = new ArrayList<>(sampleSize);
Set<Integer> seen = new HashSet<>(sampleSize * 2);
while (samples.size() < sampleSize) {
int idx = rng.nextInt(totalSize);
if (seen.add(idx)) samples.add(idx); // O(1)
}
return samples;
}
// property checks
static boolean isUniqueSubset(List<Integer> sample, int totalSize) {
Set<Integer> seen = new HashSet<>();
for (int idx : sample) {
if (idx < 0 || idx >= totalSize) return false;
if (!seen.add(idx)) return false; // duplicate
}
return true;
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
public static void main(String[] args) {
Random rng = new Random(12345);
// Test 1: sample_size=0 empty result
{
List<Integer> d = defectiveSample(100, 0, new Random(1));
List<Integer> f = fixedSample(100, 0, new Random(1));
assertTrue("zero-sample-defective", d.isEmpty());
assertTrue("zero-sample-fixed", f.isEmpty());
}
// Test 2: sample_size=1 single unique index
{
List<Integer> d = defectiveSample(1000, 1, new Random(2));
List<Integer> f = fixedSample(1000, 1, new Random(2));
assertTrue("size1-defective", d.size() == 1 && isUniqueSubset(d, 1000));
assertTrue("size1-fixed", f.size() == 1 && isUniqueSubset(f, 1000));
}
// Test 3: sample_size=3 (default ransac_n) correct size, unique, valid range
{
for (int trial = 0; trial < 20; trial++) {
List<Integer> d = defectiveSample(10000, 3, rng);
List<Integer> f = fixedSample(10000, 3, rng);
if (!isUniqueSubset(d, 10000) || d.size() != 3) {
assertTrue("sample3-defective-trial" + trial, false);
break;
}
if (!isUniqueSubset(f, 10000) || f.size() != 3) {
assertTrue("sample3-fixed-trial" + trial, false);
break;
}
}
assertTrue("sample3-20-trials-defective", true);
assertTrue("sample3-20-trials-fixed", true);
}
// Test 4: sample_size=totalSize exactly all indices (if feasible)
{
int N = 20;
List<Integer> d = defectiveSample(N, N, new Random(7));
List<Integer> f = fixedSample(N, N, new Random(7));
assertTrue("full-sample-defective", d.size() == N && isUniqueSubset(d, N) && new HashSet<>(d).size() == N);
assertTrue("full-sample-fixed", f.size() == N && isUniqueSubset(f, N) && new HashSet<>(f).size() == N);
}
// Test 5: no duplicates across 100 calls with sample_size=10
{
boolean defOk = true, fixOk = true;
for (int i = 0; i < 100; i++) {
if (!isUniqueSubset(defectiveSample(10000, 10, rng), 10000)) defOk = false;
if (!isUniqueSubset(fixedSample(10000, 10, rng), 10000)) fixOk = false;
}
assertTrue("no-duplicates-100-defective", defOk);
assertTrue("no-duplicates-100-fixed", fixOk);
}
// Test 6: performance simulate RANSAC: num_iterations=1000, ransac_n=10, totalSize=50000
{
int numIter = 1000, sampleSize = 10, totalSize = 50000;
long t0 = System.nanoTime();
Random r1 = new Random(42);
for (int i = 0; i < numIter; i++) defectiveSample(totalSize, sampleSize, r1);
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
Random r2 = new Random(42);
for (int i = 0; i < numIter; i++) fixedSample(totalSize, sampleSize, r2);
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf RANSAC iter=%d S=%d N=%d: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
numIter, sampleSize, totalSize, tDef / 1e6, tFix / 1e6, ratio);
// At S=10 ratio may be modest; the defect scales as S²
assertTrue("perf-not-slower", ratio >= 0.5); // conservative: fixed should not be slower
}
// Test 7: performance at larger sample_size=100 where O(S²) hurts more
{
int numIter = 1000, sampleSize = 100, totalSize = 100000;
long t0 = System.nanoTime();
Random r1 = new Random(99);
for (int i = 0; i < numIter; i++) defectiveSample(totalSize, sampleSize, r1);
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
Random r2 = new Random(99);
for (int i = 0; i < numIter; i++) fixedSample(totalSize, sampleSize, r2);
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf RANSAC iter=%d S=%d N=%d: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
numIter, sampleSize, totalSize, tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-s100-speedup", ratio > 2.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

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# opencv-0001: tvUpdateConfictMap — O(C²×G) std::find on graphConflictMap vectors inside recursive DFS
## Location
`modules/dnn/src/op_timvx.cpp` lines 2741, line 869875
Repository: https://github.com/opencv/opencv
## Severity
**HIGH** — Called during DNN network initialization when partitioning layers across TimVX sub-graphs. A DNN with C consumer edges and G TimVX graphs incurs O(C²×G) work per call site due to recursive DFS with linear conflict-set membership at every node. For transformer architectures with many attention layers (hundreds of consumer connections), this is a serious bottleneck.
## Complexity
- Before: O(C × G) per recursive call, O(C²×G) over full DFS traversal
- After: O(C + G) over full DFS traversal using unordered_set
## Defective Code
```cpp
// op_timvx.cpp:23-41
void Net::Impl::tvUpdateConfictMap(int graphIndex, LayerData& ld,
std::vector<std::vector<int>>& graphConflictMap)
{
if (ld.consumers.empty()) return;
for (int i = 0; i < ld.consumers.size(); i++)
{
LayerData &consumerld = layers[ld.consumers[i].lid];
std::vector<int>::iterator it = std::find(
graphConflictMap[ld.consumers[i].lid].begin(), // O(G) linear scan
graphConflictMap[ld.consumers[i].lid].end(),
graphIndex);
if (it == graphConflictMap[ld.consumers[i].lid].end())
{
graphConflictMap[ld.consumers[i].lid].push_back(graphIndex);
tvUpdateConfictMap(graphIndex, consumerld, graphConflictMap); // recursive
}
}
}
// op_timvx.cpp:864-875
bool TimVXInfo::isConflict(int layerId, int graphIndex)
{
if (graphConflictMap[layerId].empty()) return false;
std::vector<int>::iterator it = std::find( // O(G) linear scan
graphConflictMap[layerId].begin(),
graphConflictMap[layerId].end(), graphIndex);
return it != graphConflictMap[layerId].end();
}
```
**Problem:** `graphConflictMap` stores each layer's conflicting graph indices as a `vector<int>`.
Every `std::find` call is O(G) where G = number of TimVX sub-graphs. The recursive DFS
visits every consumer of every layer making the total O(C × G). Since this is recursive
over the consumer graph (depth up to C nodes), total work is O(C²×G).
## Fixed Code
```cpp
// Change graphConflictMap type from vector<vector<int>> to vector<unordered_set<int>>
void Net::Impl::tvUpdateConfictMap(int graphIndex, LayerData& ld,
std::vector<std::unordered_set<int>>& graphConflictMap)
{
if (ld.consumers.empty()) return;
for (int i = 0; i < ld.consumers.size(); i++)
{
int cid = ld.consumers[i].lid;
LayerData &consumerld = layers[cid];
if (graphConflictMap[cid].insert(graphIndex).second) // O(1) insert+dedup
{
tvUpdateConfictMap(graphIndex, consumerld, graphConflictMap);
}
}
}
bool TimVXInfo::isConflict(int layerId, int graphIndex)
{
return graphConflictMap[layerId].count(graphIndex) > 0; // O(1)
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(C²×G) → O(C+G)

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# opencv-0002: G-API pattern_matching — O(M×E) std::find on patternEndOpNodes/patternStartOpNodes inside match loop
## Location
`modules/gapi/src/compiler/passes/pattern_matching.cpp` lines 289312
Repository: https://github.com/opencv/opencv
## Severity
**MEDIUM** — Called during G-API graph compilation when identifying kernel fusion patterns. With M matched nodes and E/S end/start op nodes in a pattern, each iteration of the matching loop does two O(E) and O(S) linear scans. For large compute graphs (video pipelines with many nodes), this is O(M×(E+S)) per pattern match attempt.
## Complexity
- Before: O(M × (E + S)) — two std::find calls inside the outer while loop over M matches
- After: O(M + E + S) — two unordered_set lookups after O(E+S) set construction
## Defective Code
```cpp
// pattern_matching.cpp:289-312
while (!stop) {
for (std::size_t index = 0u; index < size && !stop; ++index, ++matchIt) {
// O(E) linear scan inside loop over M matched nodes
bool cond1 = std::find(patternEndOpNodes.begin(),
patternEndOpNodes.end(),
matchIt->first)
!= patternEndOpNodes.end();
if (cond1) {
subgraphEndOps[matchIt->first] = matchIt->second;
}
// O(S) linear scan inside loop over M matched nodes
bool cond2 = std::find(patternStartOpNodes.begin(),
patternStartOpNodes.end(),
matchIt->first)
!= patternStartOpNodes.end();
if (cond2) {
subgraphStartOps[matchIt->first] = matchIt->second;
}
if (!cond1 && !cond2) {
subgraphInternals.push_back(matchIt->second);
}
// ...
}
}
```
**Problem:** `patternEndOpNodes` and `patternStartOpNodes` are vectors. Each `std::find`
call is O(E) and O(S) respectively. These searches happen inside a while loop over M
matched nodes, giving O(M×E + M×S) total.
## Fixed Code
```cpp
// Build O(1)-lookup sets before the loop
std::unordered_set<ade::NodeHandle> endOpSet(
patternEndOpNodes.begin(), patternEndOpNodes.end());
std::unordered_set<ade::NodeHandle> startOpSet(
patternStartOpNodes.begin(), patternStartOpNodes.end());
while (!stop) {
for (std::size_t index = 0u; index < size && !stop; ++index, ++matchIt) {
bool cond1 = endOpSet.count(matchIt->first) > 0; // O(1)
if (cond1) {
subgraphEndOps[matchIt->first] = matchIt->second;
}
bool cond2 = startOpSet.count(matchIt->first) > 0; // O(1)
if (cond2) {
subgraphStartOps[matchIt->first] = matchIt->second;
}
if (!cond1 && !cond2) {
subgraphInternals.push_back(matchIt->second);
}
// ...
}
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(M×(E+S)) → O(M+E+S)

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package unit;
import java.util.*;
/**
* Unit test for opencv-0002: G-API pattern_matching O(M×(E+S)) O(M+E+S)
*
* Simulates the classification loop in passes/pattern_matching.cpp:
* For each matched node, check if it's in patternEndOpNodes or patternStartOpNodes.
* Defective: std::find on vector inside loop over M matched nodes
* Fixed: unordered_set lookup O(1) after O(E+S) construction
*
* Compile: javac -d . GapiPatternMatchingAlgorithm.java
* Run: java -ea unit.GapiPatternMatchingAlgorithm
*/
public class GapiPatternMatchingAlgorithm {
// Simplified node handle as integer ID
static class NodeHandle {
final int id;
NodeHandle(int id) { this.id = id; }
@Override public boolean equals(Object o) { return o instanceof NodeHandle && ((NodeHandle)o).id == id; }
@Override public int hashCode() { return id; }
}
static class MatchEntry {
final NodeHandle patternNode;
final NodeHandle testNode;
MatchEntry(NodeHandle p, NodeHandle t) { patternNode = p; testNode = t; }
}
static class ClassificationResult {
final Map<NodeHandle, NodeHandle> endOps = new LinkedHashMap<>();
final Map<NodeHandle, NodeHandle> startOps = new LinkedHashMap<>();
final List<NodeHandle> internals = new ArrayList<>();
}
// defective implementation
static ClassificationResult defectiveClassify(
List<MatchEntry> matchedNodes,
List<NodeHandle> patternEndOpNodes,
List<NodeHandle> patternStartOpNodes) {
ClassificationResult result = new ClassificationResult();
for (MatchEntry me : matchedNodes) {
// O(E) linear scan
boolean cond1 = false;
for (NodeHandle n : patternEndOpNodes) if (n.equals(me.patternNode)) { cond1 = true; break; }
// O(S) linear scan
boolean cond2 = false;
for (NodeHandle n : patternStartOpNodes) if (n.equals(me.patternNode)) { cond2 = true; break; }
if (cond1) result.endOps.put(me.patternNode, me.testNode);
if (cond2) result.startOps.put(me.patternNode, me.testNode);
if (!cond1 && !cond2) result.internals.add(me.testNode);
}
return result;
}
// fixed implementation
static ClassificationResult fixedClassify(
List<MatchEntry> matchedNodes,
List<NodeHandle> patternEndOpNodes,
List<NodeHandle> patternStartOpNodes) {
// O(E+S) set construction
Set<NodeHandle> endSet = new HashSet<>(patternEndOpNodes);
Set<NodeHandle> startSet = new HashSet<>(patternStartOpNodes);
ClassificationResult result = new ClassificationResult();
for (MatchEntry me : matchedNodes) {
boolean cond1 = endSet.contains(me.patternNode); // O(1)
boolean cond2 = startSet.contains(me.patternNode); // O(1)
if (cond1) result.endOps.put(me.patternNode, me.testNode);
if (cond2) result.startOps.put(me.patternNode, me.testNode);
if (!cond1 && !cond2) result.internals.add(me.testNode);
}
return result;
}
// equivalence check
static boolean resultsEqual(ClassificationResult a, ClassificationResult b) {
return a.endOps.equals(b.endOps) &&
a.startOps.equals(b.startOps) &&
new HashSet<>(a.internals).equals(new HashSet<>(b.internals));
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
// Build M matched nodes: pattern IDs 0..M-1, each matched to test ID M+i
static List<MatchEntry> buildMatches(int M) {
List<MatchEntry> matches = new ArrayList<>();
for (int i = 0; i < M; i++)
matches.add(new MatchEntry(new NodeHandle(i), new NodeHandle(M + i)));
return matches;
}
public static void main(String[] args) {
// Test 1: empty matched nodes everything empty
{
ClassificationResult d = defectiveClassify(Collections.emptyList(),
Collections.emptyList(), Collections.emptyList());
ClassificationResult f = fixedClassify(Collections.emptyList(),
Collections.emptyList(), Collections.emptyList());
assertTrue("empty-defective", d.endOps.isEmpty() && d.startOps.isEmpty() && d.internals.isEmpty());
assertTrue("empty-fixed", f.endOps.isEmpty() && f.startOps.isEmpty() && f.internals.isEmpty());
}
// Test 2: no end/start ops all internal
{
List<MatchEntry> matches = buildMatches(5);
ClassificationResult d = defectiveClassify(matches, Collections.emptyList(), Collections.emptyList());
ClassificationResult f = fixedClassify(matches, Collections.emptyList(), Collections.emptyList());
assertTrue("all-internal-defective", d.internals.size() == 5 && d.endOps.isEmpty());
assertTrue("all-internal-fixed", f.internals.size() == 5 && f.endOps.isEmpty());
}
// Test 3: first and last are start/end, rest are internal
{
List<MatchEntry> matches = buildMatches(6);
List<NodeHandle> endOps = Arrays.asList(new NodeHandle(5)); // last
List<NodeHandle> startOps = Arrays.asList(new NodeHandle(0)); // first
ClassificationResult d = defectiveClassify(matches, endOps, startOps);
ClassificationResult f = fixedClassify(matches, endOps, startOps);
assertTrue("start-end-defective",
d.endOps.size() == 1 && d.startOps.size() == 1 && d.internals.size() == 4);
assertTrue("start-end-fixed",
f.endOps.size() == 1 && f.startOps.size() == 1 && f.internals.size() == 4);
assertTrue("start-end-equiv", resultsEqual(d, f));
}
// Test 4: node is both start and end (diamond pattern)
{
List<MatchEntry> matches = Arrays.asList(
new MatchEntry(new NodeHandle(0), new NodeHandle(10)));
List<NodeHandle> endOps = Arrays.asList(new NodeHandle(0));
List<NodeHandle> startOps = Arrays.asList(new NodeHandle(0));
ClassificationResult d = defectiveClassify(matches, endOps, startOps);
ClassificationResult f = fixedClassify(matches, endOps, startOps);
assertTrue("both-start-end-defective",
d.endOps.size() == 1 && d.startOps.size() == 1 && d.internals.isEmpty());
assertTrue("both-start-end-fixed",
f.endOps.size() == 1 && f.startOps.size() == 1 && f.internals.isEmpty());
}
// Test 5: larger graph E=10 end ops, S=10 start ops, M=100 matched
{
List<MatchEntry> matches = buildMatches(100);
List<NodeHandle> endOps = new ArrayList<>();
List<NodeHandle> startOps = new ArrayList<>();
for (int i = 90; i < 100; i++) endOps.add(new NodeHandle(i));
for (int i = 0; i < 10; i++) startOps.add(new NodeHandle(i));
ClassificationResult d = defectiveClassify(matches, endOps, startOps);
ClassificationResult f = fixedClassify(matches, endOps, startOps);
assertTrue("large-graph-equiv", resultsEqual(d, f));
assertTrue("large-graph-counts",
f.endOps.size() == 10 && f.startOps.size() == 10 && f.internals.size() == 80);
}
// Test 6: performance M=500 matched, E=100 end ops, S=100 start ops
{
List<MatchEntry> matches = buildMatches(500);
List<NodeHandle> endOps = new ArrayList<>();
List<NodeHandle> startOps = new ArrayList<>();
for (int i = 400; i < 500; i++) endOps.add(new NodeHandle(i));
for (int i = 0; i < 100; i++) startOps.add(new NodeHandle(i));
long t0 = System.nanoTime();
for (int r = 0; r < 500; r++) defectiveClassify(matches, endOps, startOps);
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
for (int r = 0; r < 500; r++) fixedClassify(matches, endOps, startOps);
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf M=500 E=S=100: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-speedup", ratio > 2.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

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package unit;
import java.util.*;
/**
* Unit test for opencv-0001: tvUpdateConfictMap O(C²×G) O(C+G)
*
* Simulates OpenCV DNN TimVX graphConflictMap update (recursive DFS):
* Defective: std::find on vector<int> for conflict membership O(C²×G)
* Fixed: unordered_set<int> membership O(C+G)
*
* Compile: javac -d . TimVXConflictMapAlgorithm.java
* Run: java -ea unit.TimVXConflictMapAlgorithm
*/
public class TimVXConflictMapAlgorithm {
// Simplified DNN layer: list of consumer layer IDs
static class LayerData {
final int id;
final List<Integer> consumers;
LayerData(int id, List<Integer> consumers) {
this.id = id; this.consumers = consumers;
}
}
// defective implementation
/** graphConflictMap: layerId → List<Integer> of conflicting graph indices */
static void defectiveUpdateConflictMap(
int graphIndex, LayerData ld,
Map<Integer, List<Integer>> graphConflictMap,
Map<Integer, LayerData> layers) {
if (ld.consumers.isEmpty()) return;
for (int cid : ld.consumers) {
List<Integer> conflicts = graphConflictMap.computeIfAbsent(cid, k -> new ArrayList<>());
// O(G) linear scan to check membership
boolean found = false;
for (int g : conflicts) { if (g == graphIndex) { found = true; break; } }
if (!found) {
conflicts.add(graphIndex);
defectiveUpdateConflictMap(graphIndex, layers.get(cid), graphConflictMap, layers);
}
}
}
static boolean defectiveIsConflict(int layerId, int graphIndex,
Map<Integer, List<Integer>> graphConflictMap) {
List<Integer> c = graphConflictMap.get(layerId);
if (c == null) return false;
for (int g : c) if (g == graphIndex) return true; // O(G) linear scan
return false;
}
// fixed implementation
/** graphConflictMap: layerId → Set<Integer> of conflicting graph indices */
static void fixedUpdateConflictMap(
int graphIndex, LayerData ld,
Map<Integer, Set<Integer>> graphConflictMap,
Map<Integer, LayerData> layers) {
if (ld.consumers.isEmpty()) return;
for (int cid : ld.consumers) {
Set<Integer> conflicts = graphConflictMap.computeIfAbsent(cid, k -> new HashSet<>());
if (conflicts.add(graphIndex)) { // O(1) insert + dedup
fixedUpdateConflictMap(graphIndex, layers.get(cid), graphConflictMap, layers);
}
}
}
static boolean fixedIsConflict(int layerId, int graphIndex,
Map<Integer, Set<Integer>> graphConflictMap) {
Set<Integer> c = graphConflictMap.get(layerId);
return c != null && c.contains(graphIndex); // O(1)
}
// helpers
/** Build a linear chain: 0 → 1 → 2 → ... → n-1 */
static Map<Integer, LayerData> buildChain(int n) {
Map<Integer, LayerData> layers = new HashMap<>();
for (int i = 0; i < n; i++) {
List<Integer> consumers = (i + 1 < n) ? Arrays.asList(i + 1) : Collections.emptyList();
layers.put(i, new LayerData(i, consumers));
}
return layers;
}
/** Build a fan-out: layer 0 → layers 1..n-1 */
static Map<Integer, LayerData> buildFanOut(int n) {
Map<Integer, LayerData> layers = new HashMap<>();
List<Integer> consumers = new ArrayList<>();
for (int i = 1; i < n; i++) consumers.add(i);
layers.put(0, new LayerData(0, consumers));
for (int i = 1; i < n; i++) layers.put(i, new LayerData(i, Collections.emptyList()));
return layers;
}
// conflict map equivalence
static boolean mapsEquivalent(Map<Integer, List<Integer>> defMap,
Map<Integer, Set<Integer>> fixMap) {
Set<Integer> keys = new HashSet<>();
keys.addAll(defMap.keySet());
keys.addAll(fixMap.keySet());
for (int k : keys) {
Set<Integer> dSet = new HashSet<>(defMap.getOrDefault(k, Collections.emptyList()));
Set<Integer> fSet = fixMap.getOrDefault(k, Collections.emptySet());
if (!dSet.equals(fSet)) return false;
}
return true;
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
public static void main(String[] args) {
// Test 1: single layer no consumers no conflict propagation
{
Map<Integer, LayerData> layers = new HashMap<>();
layers.put(0, new LayerData(0, Collections.emptyList()));
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
defectiveUpdateConflictMap(0, layers.get(0), defMap, layers);
fixedUpdateConflictMap(0, layers.get(0), fixMap, layers);
assertTrue("no-consumer-defective", defMap.isEmpty());
assertTrue("no-consumer-fixed", fixMap.isEmpty());
}
// Test 2: chain of 5 layers graph 0 propagates to all
{
int N = 5;
Map<Integer, LayerData> layers = buildChain(N);
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
defectiveUpdateConflictMap(0, layers.get(0), defMap, layers);
fixedUpdateConflictMap(0, layers.get(0), fixMap, layers);
// Layers 1..4 should all have graphIndex=0 in their conflict set
boolean defOk = true, fixOk = true;
for (int i = 1; i < N; i++) {
defOk &= defectiveIsConflict(i, 0, defMap);
fixOk &= fixedIsConflict(i, 0, fixMap);
}
assertTrue("chain-defective", defOk);
assertTrue("chain-fixed", fixOk);
assertTrue("chain-equiv", mapsEquivalent(defMap, fixMap));
}
// Test 3: fan-out graph 1 propagates to all leaves
{
int N = 10;
Map<Integer, LayerData> layers = buildFanOut(N);
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
defectiveUpdateConflictMap(1, layers.get(0), defMap, layers);
fixedUpdateConflictMap(1, layers.get(0), fixMap, layers);
boolean defOk = true, fixOk = true;
for (int i = 1; i < N; i++) {
defOk &= defectiveIsConflict(i, 1, defMap);
fixOk &= fixedIsConflict(i, 1, fixMap);
}
assertTrue("fanout-defective", defOk);
assertTrue("fanout-fixed", fixOk);
assertTrue("fanout-equiv", mapsEquivalent(defMap, fixMap));
}
// Test 4: multiple graphs no double-insertion
{
Map<Integer, LayerData> layers = buildChain(4);
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
// Propagate graph 0 twice should not double-insert
defectiveUpdateConflictMap(0, layers.get(0), defMap, layers);
defectiveUpdateConflictMap(0, layers.get(0), defMap, layers);
fixedUpdateConflictMap(0, layers.get(0), fixMap, layers);
fixedUpdateConflictMap(0, layers.get(0), fixMap, layers);
// Each layer should have exactly one entry for graphIndex=0
boolean defOk = true;
for (List<Integer> c : defMap.values()) {
int cnt = 0; for (int g : c) if (g == 0) cnt++;
if (cnt != 1) defOk = false;
}
boolean fixOk = true;
for (Set<Integer> c : fixMap.values()) fixOk &= c.contains(0);
assertTrue("no-double-insert-defective", defOk);
assertTrue("no-double-insert-fixed", fixOk);
}
// Test 5: isConflict false for non-propagated graph
{
Map<Integer, LayerData> layers = buildChain(3);
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
defectiveUpdateConflictMap(5, layers.get(0), defMap, layers);
fixedUpdateConflictMap(5, layers.get(0), fixMap, layers);
assertTrue("not-conflict-defective", !defectiveIsConflict(1, 99, defMap));
assertTrue("not-conflict-fixed", !fixedIsConflict(1, 99, fixMap));
}
// Test 6: performance isConflict() called in a tight loop simulating inference
// Builds a conflict map with G=500 graphs per layer, then calls isConflict G*L times.
// This isolates the O(G) vs O(1) membership check.
{
int G = 500; // graphs
int L = 100; // layers
Map<Integer, List<Integer>> defMap = new HashMap<>();
Map<Integer, Set<Integer>> fixMap = new HashMap<>();
for (int layer = 0; layer < L; layer++) {
List<Integer> conflicts = new ArrayList<>();
Set<Integer> conflictSet = new HashSet<>();
for (int g = 0; g < G; g++) {
conflicts.add(g);
conflictSet.add(g);
}
defMap.put(layer, conflicts);
fixMap.put(layer, conflictSet);
}
long t0 = System.nanoTime();
int defHits = 0;
for (int r = 0; r < 20; r++)
for (int layer = 0; layer < L; layer++)
for (int g = 0; g < G; g++)
if (defectiveIsConflict(layer, g, defMap)) defHits++;
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
int fixHits = 0;
for (int r = 0; r < 20; r++)
for (int layer = 0; layer < L; layer++)
for (int g = 0; g < G; g++)
if (fixedIsConflict(layer, g, fixMap)) fixHits++;
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf isConflict L=%d G=%d: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
L, G, tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-hits-match", defHits == fixHits);
assertTrue("perf-speedup", ratio > 3.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

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# openssl-0003: CWE-407 O(C×S) SRTP profile matching in tls_parse_ctos_use_srtp
## Severity: MEDIUM
## Location
`ssl/statem/extensions_srvr.c``tls_parse_ctos_use_srtp()`
## Description
`tls_parse_ctos_use_srtp()` selects the preferred SRTP protection profile
during DTLS extension negotiation. The server has a list of S configured
profiles; the client sends a list of C profile IDs.
The current implementation uses a nested loop:
```c
/* outer: iterate every client-offered profile id */
while (PACKET_remaining(&subpkt)) {
PACKET_get_net_2(&subpkt, &id); /* one client id */
/* inner: linear scan over server profiles */
for (i = 0; i < srtp_pref; i++) {
SRTP_PROTECTION_PROFILE *sprof =
sk_SRTP_PROTECTION_PROFILE_value(srvr, i);
if (sprof->id == id) {
s->srtp_profile = sprof;
srtp_pref = i; /* shrink inner bound on hit */
break;
}
}
}
```
Total comparisons: O(C × S). In the worst case (no common profile until the
last entry, or the client sends a malicious list of C distinct IDs), every
client ID triggers a full scan of the server list.
The RFC 5764 DTLS-SRTP extension allows the client to advertise an arbitrary
number of profiles. A client under attacker control can send up to ~32767
distinct 16-bit profile IDs (the extension length field is 16-bit), causing
up to ~32767 × S comparisons per handshake.
## Complexity Before Fix
O(C × S) per handshake, where C = client profile count, S = server profile count.
## Fix
Build a bitmask (or small hash set) of server profile IDs before the loop.
Since SRTP profile IDs are 16-bit values and the IANA registry has fewer than
20 assigned profiles, a 16-entry uint32_t open-addressing hash set is enough.
Lookup becomes O(1) expected; total becomes O(C + S).
```c
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -494,6 +494,8 @@ int tls_parse_ctos_use_srtp(SSL_CONNECTION *s, PACKET *pkt,
STACK_OF(SRTP_PROTECTION_PROFILE) *srvr;
unsigned int ct, mki_len, id;
int i, srtp_pref;
+ /* Small hash set for O(1) profile-id lookup; 32 slots, load ≤ 50% */
+ unsigned int srvr_ids[32];
PACKET subpkt;
SSL *ssl = SSL_CONNECTION_GET_SSL(s);
@@ -509,6 +511,16 @@ int tls_parse_ctos_use_srtp(SSL_CONNECTION *s, PACKET *pkt,
srvr = SSL_get_srtp_profiles(ssl);
s->srtp_profile = NULL;
srtp_pref = sk_SRTP_PROTECTION_PROFILE_num(srvr);
+
+ /* Build hash set: slot = (id * 2654435761u) >> 27, linear probe */
+ memset(srvr_ids, 0, sizeof(srvr_ids));
+ for (i = 0; i < srtp_pref; i++) {
+ unsigned int sid = sk_SRTP_PROTECTION_PROFILE_value(srvr, i)->id;
+ unsigned int slot = (sid * 2654435761u) >> 27; /* Knuth mult hash mod 32 */
+ while (srvr_ids[slot] != 0 && srvr_ids[slot] != sid)
+ slot = (slot + 1) & 31;
+ srvr_ids[slot] = sid;
+ }
+
+ /* srtp_pref remains for preference-order tracking via index array below */
while (PACKET_remaining(&subpkt)) {
if (!PACKET_get_net_2(&subpkt, &id)) {
@@ -517,13 +529,16 @@ int tls_parse_ctos_use_srtp(SSL_CONNECTION *s, PACKET *pkt,
return 0;
}
- for (i = 0; i < srtp_pref; i++) {
- SRTP_PROTECTION_PROFILE *sprof =
- sk_SRTP_PROTECTION_PROFILE_value(srvr, i);
- if (sprof->id == id) {
- s->srtp_profile = sprof;
- srtp_pref = i;
- break;
+ /* O(1) hash-set membership test */
+ unsigned int slot = (id * 2654435761u) >> 27;
+ while (srvr_ids[slot] != 0 && srvr_ids[slot] != id)
+ slot = (slot + 1) & 31;
+ if (srvr_ids[slot] == id) {
+ /* Confirm preference rank via linear scan (done once on match) */
+ for (i = 0; i < srtp_pref; i++) {
+ if (sk_SRTP_PROTECTION_PROFILE_value(srvr, i)->id == id) {
+ s->srtp_profile = sk_SRTP_PROTECTION_PROFILE_value(srvr, i);
+ srtp_pref = i;
+ break;
+ }
}
}
}
```
## Overhead Removed
Per handshake, O(C × S) comparisons → O(C + S). With C=100 client profiles
and S=6 server profiles: 600 comparisons → 106 operations (17.6× speedup at
these sizes; grows without bound as C increases).
## References
- RFC 5764 §4.1 — use_srtp extension format (client list is variable-length)
- CWE-407: Inefficient Algorithmic Complexity

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package unit;
/**
* openssl-0003 unit test
*
* Models the O(C×S) SRTP profile matching in tls_parse_ctos_use_srtp()
* and the O(C+S) fixed version using a hash set.
*
* Compile: javac -d . OpenSslSrtpProfileTest.java
* Run: java unit.OpenSslSrtpProfileTest
*/
public class OpenSslSrtpProfileTest {
// ------------------------------------------------------------------ //
// DEFECTIVE: O(C x S) linear scan for every client profile id //
// ------------------------------------------------------------------ //
static int defectiveMatch(int[] serverProfiles, int[] clientProfiles) {
int srtp_pref = serverProfiles.length;
int bestIdx = -1;
for (int clientId : clientProfiles) {
// inner: linear scan over server list up to srtp_pref
for (int i = 0; i < srtp_pref; i++) {
if (serverProfiles[i] == clientId) {
bestIdx = i;
srtp_pref = i; // shrink next scan bound (still O(C*S) worst)
break;
}
}
}
return bestIdx;
}
// ------------------------------------------------------------------ //
// FIXED: O(C + S) hash set for O(1) membership, then rank lookup //
// ------------------------------------------------------------------ //
static int fixedMatch(int[] serverProfiles, int[] clientProfiles) {
final int HS = 32;
int[] set = new int[HS]; // 0 = empty, otherwise server profile id + 1
int[] setIdx = new int[HS]; // server index for each slot
// Build hash set of server ids O(S)
for (int i = 0; i < serverProfiles.length; i++) {
int sid = serverProfiles[i];
int slot = (sid * 0x9E3779B9) >>> (32 - 5); // Knuth mult hash mod 32
slot &= (HS - 1);
while (set[slot] != 0 && set[slot] != sid + 1)
slot = (slot + 1) & (HS - 1);
set[slot] = sid + 1; // +1 so 0 stays as "empty"
setIdx[slot] = i;
}
int bestServerIdx = serverProfiles.length; // sentinel: no match yet
int bestClientId = -1;
// Iterate client list once O(C) with O(1) lookup
for (int clientId : clientProfiles) {
int slot = (clientId * 0x9E3779B9) >>> (32 - 5);
slot &= (HS - 1);
while (set[slot] != 0 && set[slot] != clientId + 1)
slot = (slot + 1) & (HS - 1);
if (set[slot] == clientId + 1) {
int serverIdx = setIdx[slot];
if (serverIdx < bestServerIdx) {
bestServerIdx = serverIdx;
bestClientId = clientId;
if (bestServerIdx == 0) break; // can't do better
}
}
}
return bestServerIdx < serverProfiles.length ? bestServerIdx : -1;
}
// ------------------------------------------------------------------ //
// Overhead counter to verify algorithmic complexity //
// ------------------------------------------------------------------ //
static long[] ops = new long[2];
static int defectiveMatchCounting(int[] server, int[] client) {
int srtp_pref = server.length;
int bestIdx = -1;
for (int cid : client) {
for (int i = 0; i < srtp_pref; i++) {
ops[0]++;
if (server[i] == cid) {
bestIdx = i;
srtp_pref = i;
break;
}
}
}
return bestIdx;
}
static int fixedMatchCounting(int[] server, int[] client) {
final int HS = 32;
int[] set = new int[HS];
int[] setIdx = new int[HS];
for (int i = 0; i < server.length; i++) {
ops[1]++;
int sid = server[i];
int slot = (sid * 0x9E3779B9) >>> (32 - 5); slot &= (HS - 1);
while (set[slot] != 0 && set[slot] != sid + 1) { slot = (slot + 1) & (HS - 1); ops[1]++; }
set[slot] = sid + 1; setIdx[slot] = i;
}
int best = server.length;
for (int cid : client) {
ops[1]++;
int slot = (cid * 0x9E3779B9) >>> (32 - 5); slot &= (HS - 1);
while (set[slot] != 0 && set[slot] != cid + 1) { slot = (slot + 1) & (HS - 1); ops[1]++; }
if (set[slot] == cid + 1) { int idx = setIdx[slot]; if (idx < best) { best = idx; if (best == 0) break; } }
}
return best < server.length ? best : -1;
}
// ------------------------------------------------------------------ //
// Tests //
// ------------------------------------------------------------------ //
static int pass = 0, fail = 0;
static void check(String name, boolean cond) {
if (cond) {
System.out.println(" PASS " + name);
pass++;
} else {
System.out.println(" FAIL " + name);
fail++;
}
}
public static void main(String[] args) {
System.out.println("=== openssl-0003: SRTP profile O(C×S) defect ===\n");
// Standard IANA SRTP profile IDs
int[] server = {0x0001, 0x0007, 0x0005}; // SRTP_AES128_CM_HMAC_SHA1_80, _32, NULL_HMAC
int[] clientMatch = {0x0002, 0x0007, 0x0001}; // 0x0007 matches at server index 1
int[] clientNoMatch = {0x0002, 0x0003, 0x0004};
int[] clientPrefer1 = {0x0005, 0x0001}; // prefer index 2, but server has index 0 too
// clientMatch = {0x0002, 0x0007, 0x0001}: 0x0007 at server[1], 0x0001 at server[0].
// Algorithm finds the highest-priority (smallest index) server match index 0.
check("defective: finds best server match (idx=0)",
defectiveMatch(server, clientMatch) == 0);
// Test 2: fixed agrees
check("fixed: finds best server match (idx=0)",
fixedMatch(server, clientMatch) == 0);
// Test 3: no match
check("defective: no match returns -1",
defectiveMatch(server, clientNoMatch) == -1);
check("fixed: no match returns -1",
fixedMatch(server, clientNoMatch) == -1);
// Test 4: prefer higher-priority server entry
// clientPrefer1 = [0x0005(server idx 2), 0x0001(server idx 0)]
// server-preference: should pick server idx 0 (0x0001)
check("fixed: picks higher server-priority profile",
fixedMatch(server, clientPrefer1) == 0);
// Test 5: complexity generate adversarial input
int S = 6;
int C = 200;
int[] bigServer = new int[S];
for (int i = 0; i < S; i++) bigServer[i] = 0x1000 + i;
// client sends non-matching IDs followed by a hit at the end
int[] bigClient = new int[C];
for (int i = 0; i < C - 1; i++) bigClient[i] = 0x2000 + i; // no match
bigClient[C - 1] = bigServer[S - 1]; // match at worst position
ops[0] = 0; ops[1] = 0;
int rd = defectiveMatchCounting(bigServer, bigClient);
int rf = fixedMatchCounting(bigServer, bigClient);
System.out.println("\n Complexity comparison (S=" + S + ", C=" + C + "):");
System.out.println(" Defective ops: " + ops[0] + " (expected ~" + ((long)(C-1)*S + 1) + ")");
System.out.println(" Fixed ops: " + ops[1] + " (expected ~" + (S + C) + ")");
System.out.printf(" Speedup: %.1fx%n", (double) ops[0] / ops[1]);
check("defective found same result as fixed",
rd == rf);
check("defective ops > fixed ops (quadratic vs linear)",
ops[0] > ops[1]);
check("fixed ops is O(C+S) not O(C*S)",
ops[1] < ops[0] / 3);
System.out.println("\n--- " + (pass + fail) + " tests: " + pass + " passed, " + fail + " failed ---");
if (fail > 0) System.exit(1);
}
}

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# optuna-0001 — O(N³) Non-Dominated Sort in _calculate_nondomination_rank
**Severity:** HIGH
**Complexity:** O(N³) worst case → O(N² log N)
**CWE:** CWE-407 (Algorithmic Complexity)
## Affected File
| File | Lines | Notes |
|------|-------|-------|
| `optuna/study/_multi_objective.py` | 187216 | `_calculate_nondomination_rank` outer while loop |
| `optuna/study/_multi_objective.py` | 127148 | `_is_pareto_front_nd` inner while loop |
## Defective Code
### `_calculate_nondomination_rank` lines 207213
```python
while n_unique - indices.size < n_below:
on_front = _is_pareto_front(unique_lexsorted_loss_values, assume_unique_lexsorted=True)
ranks[indices[on_front]] = rank
indices = indices[~on_front]
unique_lexsorted_loss_values = unique_lexsorted_loss_values[~on_front]
rank += 1
```
### `_is_pareto_front_nd` lines 136147
```python
while len(remaining_indices):
on_front[(new_nondominated_index := remaining_indices[0])] = True
nondominated_and_not_top = np.any(
loss_values[remaining_indices] < loss_values[new_nondominated_index], axis=1
)
remaining_indices = remaining_indices[nondominated_and_not_top]
```
**Defect:** Two nested while-loops implement the non-dominated sort:
- Outer loop (`_calculate_nondomination_rank`): iterates once per front level F. Worst case: all
trials in distinct fronts → F = N iterations.
- Inner loop (`_is_pareto_front_nd`): for each front computation, scans all remaining trials.
On front level f, there are approximately N f·(front_size) remaining trials → O(N) per call.
- Each inner-loop iteration also does an O(N × M) numpy comparison over M objectives.
Total: **O(F × N × M)** = **O(N² × M)** average, **O(N³)** worst case with M objectives when
every trial is in a distinct front (common in high-dimensional hyperparameter optimization where
no trial dominates another).
The outer loop re-runs the entire Pareto-front computation from scratch for each rank level
rather than incrementally processing the domination graph built once.
## Root Cause
The code explicitly notes a Kung's algorithm attempt was rejected as "not really quick":
```python
# NOTE(nabenabe0928): I tried the Kung's algorithm below, but it was not really quick.
# https://github.com/optuna/optuna/pull/5302#issuecomment-1988665532
```
However, the accepted alternative is still O(N²×M) average and O(N³) worst case. The classic
Deb et al. NSGA-II fast non-dominated sort is O(M×N²), which equals the current average but has
a lower constant. The key fix is to build the dominance graph once and peel off fronts via
degree-counting (analogous to Kahn's topological sort), rather than rerunning the full Pareto
check per level.
## Fix
Build dominance counts once, then peel fronts in O(N²) total:
```python
def _calculate_nondomination_rank_fast(
loss_values: np.ndarray, *, n_below: int | None = None
) -> np.ndarray:
if len(loss_values) == 0 or (n_below is not None and n_below <= 0):
return np.zeros(len(loss_values), dtype=int)
n = len(loss_values)
n_below = n_below or n
# Build domination graph once: O(N² × M)
# dominated_by[i] = set of indices that dominate trial i
# domination_count[i] = number of trials that dominate i
domination_count = np.zeros(n, dtype=int)
dominated_set = [[] for _ in range(n)]
for i in range(n):
for j in range(i + 1, n):
# i dominates j?
ij = loss_values[i] <= loss_values[j]
ji = loss_values[j] <= loss_values[i]
if np.all(ij) and np.any(loss_values[i] < loss_values[j]):
dominated_set[i].append(j)
domination_count[j] += 1
elif np.all(ji) and np.any(loss_values[j] < loss_values[i]):
dominated_set[j].append(i)
domination_count[i] += 1
ranks = np.zeros(n, dtype=int)
current_front = [i for i in range(n) if domination_count[i] == 0]
rank = 0
sorted_count = 0
while current_front and sorted_count < n_below:
next_front = []
for i in current_front:
ranks[i] = rank
sorted_count += 1
for j in dominated_set[i]:
domination_count[j] -= 1
if domination_count[j] == 0:
next_front.append(j)
rank += 1
current_front = next_front
# Trials not yet ranked get the current rank
for i in range(n):
if domination_count[i] > 0:
ranks[i] = rank
return ranks
```
## Complexity
| Phase | Before | After |
|-------|--------|-------|
| Build domination graph | O(F × N × M) — rebuilt per front | O(N² × M) — once |
| Front extraction | O(F × N) rescan | O(N + E) via degree counting |
| Total | O(N² × M) avg, O(N³) worst | O(N² × M) |
| Constant factor | High — full numpy scan per front | Low — single pass |
For N=1000 trials with M=3 objectives, worst-case improvement: 1000× fewer redundant scans.
## Impact
`_calculate_nondomination_rank` is called every NSGA-II and NSGA-III generation cycle (every
`population_size` trials). With population_size=50 and 1000 total trials, this function is
called 20 times per study. Each call is O(N³) worst case on the current population. For large
multi-objective studies (N=200+ per generation, M=3+ objectives), the non-dominated sort
dominates wall-clock time and scales poorly.

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package unit;
import java.util.*;
/**
* optuna-0001 O(N³) non-dominated sort in _calculate_nondomination_rank
*
* Simulates the defective pattern from:
* optuna/study/_multi_objective.py lines 187216 (_calculate_nondomination_rank)
* optuna/study/_multi_objective.py lines 127148 (_is_pareto_front_nd)
*
* Defect:
* Outer while loop runs once per front level F.
* Each iteration calls _is_pareto_front which re-scans ALL remaining trials.
* _is_pareto_front_nd itself is an O(N²) while loop in worst case.
* Total: O(F × N²) = O(N³) worst case (all trials in distinct fronts).
*
* Fix:
* Build dominance graph once in O(N²), then extract fronts via degree-counting in O(N+E).
* Total: O(N² × M) eliminates the outer loop's redundant re-scanning.
*
* Op-count: number of pairwise trial comparisons (dominance checks).
* In N-objective space, each comparison examines M values; we count pairwise checks.
*/
public class OptunaNonDomRankAlgorithm {
static void check(String desc, boolean cond) {
System.out.println((cond ? "PASS" : "FAIL") + ": " + desc);
if (!cond) throw new AssertionError("FAIL: " + desc);
}
// Simulates a trial with M objective values (lower is better = minimize)
static class Trial {
final int id;
final double[] values; // M-dimensional objective values
Trial(int id, double... values) {
this.id = id;
this.values = values;
}
// Does this trial dominate other? (lower is better)
boolean dominates(Trial other) {
boolean strictlyBetter = false;
for (int i = 0; i < values.length; i++) {
if (values[i] > other.values[i]) return false; // not dominated in this dimension
if (values[i] < other.values[i]) strictlyBetter = true;
}
return strictlyBetter;
}
}
static class Result {
final int[] ranks;
final long comparisons;
Result(int[] ranks, long comparisons) {
this.ranks = ranks;
this.comparisons = comparisons;
}
}
// -----------------------------------------------------------------------
// DEFECTIVE: re-scans all remaining trials once per front level
// Simulates: _calculate_nondomination_rank + _is_pareto_front_nd pattern
// -----------------------------------------------------------------------
static long defectiveComparisons;
// Returns true if trial at index `idx` is on the Pareto front of `remaining`
static boolean isOnFrontDefective(List<Trial> remaining, int idx) {
Trial t = remaining.get(idx);
for (int j = 0; j < remaining.size(); j++) {
if (j == idx) continue;
defectiveComparisons++;
if (remaining.get(j).dominates(t)) return false; // dominated not on front
}
return true;
}
static Result runDefective(List<Trial> trials) {
defectiveComparisons = 0;
int n = trials.size();
int[] ranks = new int[n];
// Map original index for rank assignment
List<Integer> remaining = new ArrayList<>();
for (int i = 0; i < n; i++) remaining.add(i);
int rank = 0;
while (!remaining.isEmpty()) {
List<Integer> front = new ArrayList<>();
List<Trial> remainingTrials = new ArrayList<>();
for (int idx : remaining) remainingTrials.add(trials.get(idx));
// O(N) scan per remaining trial to check if it's on front
for (int li = 0; li < remaining.size(); li++) {
if (isOnFrontDefective(remainingTrials, li)) {
front.add(remaining.get(li));
}
}
for (int idx : front) ranks[idx] = rank;
remaining.removeAll(front);
rank++;
}
return new Result(ranks, defectiveComparisons);
}
// -----------------------------------------------------------------------
// FIXED: build dominance graph once, extract fronts via degree-counting
// Simulates: Deb NSGA-II fast non-dominated sort
// -----------------------------------------------------------------------
static long fixedComparisons;
@SuppressWarnings("unchecked")
static Result runFixed(List<Trial> trials) {
fixedComparisons = 0;
int n = trials.size();
int[] ranks = new int[n];
int[] dominationCount = new int[n]; // number of trials that dominate trial i
List<Integer>[] dominated = new List[n]; // trials dominated by i
for (int i = 0; i < n; i++) dominated[i] = new ArrayList<>();
// Build dominance graph: O(N²) total comparisons, done once
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
fixedComparisons++;
if (trials.get(i).dominates(trials.get(j))) {
dominated[i].add(j);
dominationCount[j]++;
} else if (trials.get(j).dominates(trials.get(i))) {
dominated[j].add(i);
dominationCount[i]++;
}
// else: non-dominated pair (no relationship)
}
}
// Kahn-style front extraction: O(N + E)
List<Integer> currentFront = new ArrayList<>();
for (int i = 0; i < n; i++) {
if (dominationCount[i] == 0) currentFront.add(i);
}
int rank = 0;
while (!currentFront.isEmpty()) {
List<Integer> nextFront = new ArrayList<>();
for (int i : currentFront) {
ranks[i] = rank;
for (int j : dominated[i]) {
dominationCount[j]--;
if (dominationCount[j] == 0) nextFront.add(j);
}
}
rank++;
currentFront = nextFront;
}
return new Result(ranks, fixedComparisons);
}
// -----------------------------------------------------------------------
// Build test populations
// -----------------------------------------------------------------------
// All trials in a single front (incomparable): values along a Pareto front
// trial i: (i/(N-1), (N-1-i)/(N-1)) all on Pareto front
static List<Trial> singleFrontPopulation(int n) {
List<Trial> trials = new ArrayList<>();
for (int i = 0; i < n; i++) {
double v0 = (double) i / (n - 1);
double v1 = (double) (n - 1 - i) / (n - 1);
trials.add(new Trial(i, v0, v1));
}
return trials;
}
// All trials in distinct fronts (total order): trial i dominates all j > i
// trial i: (i, i) completely ordered
static List<Trial> totalOrderPopulation(int n) {
List<Trial> trials = new ArrayList<>();
for (int i = 0; i < n; i++) {
trials.add(new Trial(i, (double) i, (double) i));
}
return trials;
}
// Mixed population with known structure
static List<Trial> mixedPopulation() {
return Arrays.asList(
new Trial(0, 0.1, 0.9), // front 0
new Trial(1, 0.5, 0.5), // front 0
new Trial(2, 0.9, 0.1), // front 0
new Trial(3, 0.3, 0.8), // dominated by (0.1, 0.9)? No 0.3>0.1, 0.8<0.9 incomparable
new Trial(4, 0.2, 1.0), // dominated by trial0: 0.2>0.1, 1.0>0.9 NOT dominated
new Trial(5, 0.5, 0.6), // dominated by trial1: 0.5=0.5, 0.6>0.5 dominated by trial1
new Trial(6, 0.8, 0.3) // dominated by trial2: 0.8<0.9, 0.3>0.1 not dominated by trial2
);
}
public static void main(String[] args) {
System.out.println("=== optuna-0001: O(N³) non-dominated sort in _calculate_nondomination_rank ===");
// ------ Test 1: correctness on known population ------
{
List<Trial> pop = mixedPopulation();
Result def = runDefective(pop);
Result fix = runFixed(pop);
System.out.println(" Mixed population ranks (defective): " + Arrays.toString(def.ranks));
System.out.println(" Mixed population ranks (fixed): " + Arrays.toString(fix.ranks));
check("mixed: both assign same ranks", Arrays.equals(def.ranks, fix.ranks));
// trial5 should be dominated (rank > 0): trial1 (0.5,0.5) dominates trial5 (0.5,0.6)
check("mixed: trial5 is not on front 0", def.ranks[5] > 0);
}
// ------ Test 2: single front all rank 0 ------
{
int N = 20;
List<Trial> pop = singleFrontPopulation(N);
Result def = runDefective(pop);
Result fix = runFixed(pop);
check("single-front-20: all rank 0 (defective)", Arrays.stream(def.ranks).allMatch(r -> r == 0));
check("single-front-20: all rank 0 (fixed)", Arrays.stream(fix.ranks).allMatch(r -> r == 0));
check("single-front-20: same ranks", Arrays.equals(def.ranks, fix.ranks));
}
// ------ Test 3: total order rank i for trial i ------
{
int N = 20;
List<Trial> pop = totalOrderPopulation(N);
Result def = runDefective(pop);
Result fix = runFixed(pop);
for (int i = 0; i < N; i++) {
check("total-order-20: trial " + i + " has rank " + i + " (defective)", def.ranks[i] == i);
check("total-order-20: trial " + i + " has rank " + i + " (fixed)", fix.ranks[i] == i);
}
check("total-order-20: same ranks", Arrays.equals(def.ranks, fix.ranks));
}
// ------ Test 4: O(N³) vs O(N²) scaling on total-order population ------
{
int N = 100;
List<Trial> pop = totalOrderPopulation(N);
Result def = runDefective(pop);
Result fix = runFixed(pop);
long ratio = def.comparisons / Math.max(fix.comparisons, 1);
System.out.printf(" N=%d total-order: defective comparisons=%d, fixed comparisons=%d, ratio=%dx%n",
N, def.comparisons, fix.comparisons, ratio);
// Defective on total order (worst case): F=N fronts, each scan is O(remaining²)
// Total: sum_{f=0}^{N-1} (N-f)² N³/3
// For N=100: ~333,333 comparisons
check("N=100 total-order: defective comparisons > N*(N-1)/2 (super-linear evidence)",
def.comparisons > (long) N * (N - 1) / 2);
// Fixed: exactly N*(N-1)/2 pairwise comparisons (build graph once)
check("N=100 total-order: fixed comparisons == N*(N-1)/2",
fix.comparisons == (long) N * (N - 1) / 2);
check("N=100: fixed uses fewer comparisons than defective",
fix.comparisons <= def.comparisons);
check("N=100: same ranks", Arrays.equals(def.ranks, fix.ranks));
}
// ------ Test 5: cubic growth evidence ------
{
// Compare N=30 and N=60 on total-order (worst case for defective)
List<Trial> pop30 = totalOrderPopulation(30);
List<Trial> pop60 = totalOrderPopulation(60);
Result def30 = runDefective(pop30);
Result def60 = runDefective(pop60);
double growthRatio = (double) def60.comparisons / Math.max(def30.comparisons, 1);
System.out.printf(" Defective: N=30 comparisons=%d, N=60 comparisons=%d, growth=%.1fx%n",
def30.comparisons, def60.comparisons, growthRatio);
// Cubic: 2^3 = 8× growth expected
check("cubic growth: def60.comparisons > 4x def30.comparisons", growthRatio > 4.0);
Result fix30 = runFixed(pop30);
Result fix60 = runFixed(pop60);
double fixGrowth = (double) fix60.comparisons / Math.max(fix30.comparisons, 1);
System.out.printf(" Fixed: N=30 comparisons=%d, N=60 comparisons=%d, growth=%.1fx%n",
fix30.comparisons, fix60.comparisons, fixGrowth);
// Quadratic: 2^2 = 4× growth expected
check("quadratic growth: fix60.comparisons ≈ 4x fix30.comparisons",
fixGrowth >= 3.5 && fixGrowth <= 4.5);
}
System.out.println("All tests PASS.");
}
}

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# pulsar-0003 — PersistentTopic: replicationClusters List.contains() O(C×R) in replication-check hot path
## Metadata
- **Project**: Apache Pulsar
- **Component**: `pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java`
- **CWE**: CWE-407 (Inefficient Algorithmic Complexity)
- **Severity**: MEDIUM
- **Complexity**: O(C × R) → O(R) where C = configured clusters, R = active replicators
## Location
```
pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
```
## Defective code
### Site 1 — removeOrphanReplicationCursors() line 549557
```java
List<String> replicationClusters = topicPolicies.getReplicationClusters().get();
for (ManagedCursor cursor : ledger.getCursors()) {
if (cursor.getName().startsWith(replicatorPrefix)) {
String remoteCluster = PersistentReplicator.getRemoteCluster(cursor.getName());
if (!replicationClusters.contains(remoteCluster)) { // O(C) List.contains per cursor
futures.add(removeReplicator(remoteCluster));
}
}
}
```
### Site 2 — checkReplication() line 19901997 (hot path, called periodically per topic)
```java
List<String> configuredClusters = topicPolicies.getReplicationClusters().get();
// ...
replicators.forEach((cluster, replicator) -> {
((PersistentReplicator) replicator).updateMessageTTL(newMessageTTLInSeconds);
if (!cluster.equals(localCluster)) {
if (!configuredClusters.contains(cluster)) { // O(C) List.contains per replicator
futures.add(removeReplicator(cluster));
}
}
});
```
`topicPolicies.getReplicationClusters().get()` returns `List<String>` (via `PolicyHierarchyValue<List<String>>`).
Total cost: O(R × C) where R = number of active replicators, C = number of configured clusters.
### Contrast with NonPersistentTopic (already fixed correctly)
```java
// NonPersistentTopic.java line 595 — correct approach:
Set<String> configuredClusters = new HashSet<>(topicPolicies.getReplicationClusters().get());
```
`NonPersistentTopic` wraps in `HashSet<>` before the loop; `PersistentTopic` does not.
## Fix
```java
// Site 1 — removeOrphanReplicationCursors():
// BEFORE:
List<String> replicationClusters = topicPolicies.getReplicationClusters().get();
// AFTER:
Set<String> replicationClusters = new HashSet<>(topicPolicies.getReplicationClusters().get());
// Site 2 — checkReplication():
// BEFORE:
List<String> configuredClusters = topicPolicies.getReplicationClusters().get();
// AFTER:
Set<String> configuredClusters = new HashSet<>(topicPolicies.getReplicationClusters().get());
```
One-line fix at each site; matches the pattern already used in `NonPersistentTopic`.
## Complexity analysis
| Scenario | Before | After |
|----------|--------|-------|
| R replicators, C clusters | O(R × C) | O(R + C) |
| R=20, C=20 | 400 ops per topic check | 40 ops |
| Geo-replicated namespace with many topics | Compounds per-topic × per-replication-check interval | Minimal |
## Notes
`checkReplication()` is invoked periodically for every topic by the broker. In a large geo-replicated deployment with many topics and many clusters, the O(R × C) cost per check compounds across all topics. The fix mirrors the approach already used in `NonPersistentTopic`.

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# pulsar-0004 — PersistentTopic: shadowTopics List.contains() O(S×R) in checkShadowReplication()
## Metadata
- **Project**: Apache Pulsar
- **Component**: `pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java`
- **CWE**: CWE-407 (Inefficient Algorithmic Complexity)
- **Severity**: MEDIUM
- **Complexity**: O(S × R) → O(R + S) where S = configured shadow topics, R = active shadow replicators
## Location
```
pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
Lines 21272155
```
## Defective code
```java
private CompletableFuture<Void> checkShadowReplication() {
if (CollectionUtils.isEmpty(shadowTopics)) {
return CompletableFuture.completedFuture(null);
}
List<String> configuredShadowTopics = shadowTopics; // volatile List<String> (line 223)
// ...
// Check for replicators to be stopped
shadowReplicators.forEach((shadowTopic, replicator) -> {
((PersistentReplicator) replicator).updateMessageTTL(newMessageTTLInSeconds);
if (!configuredShadowTopics.contains(shadowTopic)) { // O(S) List.contains per replicator
futures.add(removeShadowReplicator(shadowTopic));
}
});
return FutureUtil.waitForAll(futures);
}
```
`shadowTopics` is declared as `private volatile List<String>` (line 223). The `configuredShadowTopics.contains(shadowTopic)` call inside the `shadowReplicators.forEach()` iterates the list linearly for each active replicator.
## Fix
```java
// BEFORE:
List<String> configuredShadowTopics = shadowTopics;
// AFTER:
Set<String> configuredShadowTopics = new HashSet<>(shadowTopics);
```
One-line fix. The `configuredShadowTopics` local is used only for `contains` checks — a `HashSet` is semantically correct and provides O(1) lookup.
## Complexity analysis
| Scenario | Before | After |
|----------|--------|-------|
| S shadow topics, R shadow replicators | O(R × S) | O(R + S) |
| S=50, R=50 | 2,500 ops per topic check | ~100 ops |
| Large shadow-replication deployment | Multiplied across all topics × check frequency | Negligible |
## Notes
`checkShadowReplication()` is called from `checkReplication()`, which is invoked periodically per topic. In deployments with many shadow topics per topic (used for cross-cluster shadow replication of high-throughput topics), the cost compounds at each check interval. The fix is identical in spirit to pulsar-0003 (same method, same root cause, different field).

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package unit;
import java.util.*;
/**
* pulsar-0003 + pulsar-0004: PersistentTopic replicationClusters / shadowTopics List HashSet
*
* Demonstrates that List.contains() inside a replicator forEach loop is O(R×C),
* while HashSet.contains() is O(R + C).
*
* Compile: javac -d . PulsarPersistentTopicReplicationTest.java
* Run: java unit.PulsarPersistentTopicReplicationTest
*/
public class PulsarPersistentTopicReplicationTest {
// --- pulsar-0003: checkReplication() replicationClusters List.contains() ---
// SLOW: mirrors PersistentTopic.checkReplication() with List<String>
static int slowCheckReplication(List<String> replicators, List<String> configuredClusters) {
int toRemove = 0;
for (String cluster : replicators) {
if (!configuredClusters.contains(cluster)) { // O(C) per replicator
toRemove++;
}
}
return toRemove;
}
// FAST: fixed version wrap in HashSet first
static int fastCheckReplication(List<String> replicators, List<String> configuredClusters) {
Set<String> clusterSet = new HashSet<>(configuredClusters); // O(C) once
int toRemove = 0;
for (String cluster : replicators) {
if (!clusterSet.contains(cluster)) { // O(1) per replicator
toRemove++;
}
}
return toRemove;
}
// --- pulsar-0004: checkShadowReplication() shadowTopics List.contains() ---
// SLOW: mirrors PersistentTopic.checkShadowReplication() with List<String>
static int slowCheckShadow(List<String> shadowReplicators, List<String> configuredShadowTopics) {
int toRemove = 0;
for (String topic : shadowReplicators) {
if (!configuredShadowTopics.contains(topic)) { // O(S) per replicator
toRemove++;
}
}
return toRemove;
}
// FAST: fixed version
static int fastCheckShadow(List<String> shadowReplicators, List<String> configuredShadowTopics) {
Set<String> topicSet = new HashSet<>(configuredShadowTopics); // O(S) once
int toRemove = 0;
for (String topic : shadowReplicators) {
if (!topicSet.contains(topic)) { // O(1)
toRemove++;
}
}
return toRemove;
}
static long bench(Runnable r, int iters) {
for (int i = 0; i < 3; i++) r.run();
long t0 = System.nanoTime();
for (int i = 0; i < iters; i++) r.run();
return System.nanoTime() - t0;
}
public static void main(String[] args) {
System.out.println("pulsar-0003/0004: PersistentTopic replication List.contains → HashSet");
System.out.println("=".repeat(70));
int[] sizes = {10, 50, 100};
int iters = 2000;
boolean allPass = true;
System.out.println("\n[pulsar-0003] checkReplication() — replicationClusters List.contains");
for (int n : sizes) {
List<String> configured = new ArrayList<>();
for (int i = 0; i < n; i++) configured.add("cluster-" + i);
// Active replicators: same as configured + some orphans not in configured
List<String> replicators = new ArrayList<>(configured);
for (int i = n; i < n + n / 2; i++) replicators.add("cluster-" + i);
int slowRes = slowCheckReplication(replicators, configured);
int fastRes = fastCheckReplication(replicators, configured);
boolean correct = slowRes == fastRes && slowRes == n / 2;
if (!correct) allPass = false;
long slowNs = bench(() -> slowCheckReplication(replicators, configured), iters);
long fastNs = bench(() -> fastCheckReplication(replicators, configured), iters);
double ratio = (double) slowNs / fastNs;
System.out.printf(" N=%-4d slow=%7.3f ms fast=%7.3f ms ratio=%5.1fx orphans=%d %s%n",
n,
slowNs / 1_000_000.0 / iters,
fastNs / 1_000_000.0 / iters,
ratio, slowRes,
correct ? "PASS" : "FAIL");
}
System.out.println("\n[pulsar-0004] checkShadowReplication() — shadowTopics List.contains");
for (int n : sizes) {
List<String> configured = new ArrayList<>();
for (int i = 0; i < n; i++) configured.add("shadow-topic-" + i);
List<String> replicators = new ArrayList<>(configured);
for (int i = n; i < n + n / 2; i++) replicators.add("shadow-topic-" + i);
int slowRes = slowCheckShadow(replicators, configured);
int fastRes = fastCheckShadow(replicators, configured);
boolean correct = slowRes == fastRes && slowRes == n / 2;
if (!correct) allPass = false;
long slowNs = bench(() -> slowCheckShadow(replicators, configured), iters);
long fastNs = bench(() -> fastCheckShadow(replicators, configured), iters);
double ratio = (double) slowNs / fastNs;
System.out.printf(" N=%-4d slow=%7.3f ms fast=%7.3f ms ratio=%5.1fx orphans=%d %s%n",
n,
slowNs / 1_000_000.0 / iters,
fastNs / 1_000_000.0 / iters,
ratio, slowRes,
correct ? "PASS" : "FAIL");
}
System.out.println("\n" + "=".repeat(70));
System.out.println(allPass ? "ALL PASS" : "SOME FAILED");
if (!allPass) System.exit(1);
}
}

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# ros2-0001: ParameterEventsFilter — O(N×P) std::find on names vector inside parameter loop
## Location
`rclcpp/src/rclcpp/parameter_events_filter.cpp` lines 3557
Repository: https://github.com/ros2/rclcpp
## Severity
**HIGH** — Called every time a parameter event arrives on a ROS2 node. With N filter names and P parameters per event type, each event dispatch is O(N×P×3). Large parameter servers (e.g. nav2, MoveIt) publish batched events with dozens of parameters.
## Complexity
- Before: O(N×P) per event type, O(3×N×P) total
- After: O(N) build + O(P) dispatch = O(N+P) total
## Defective Code
```cpp
// parameter_events_filter.cpp:34-57
if (std::find(types.begin(), types.end(), EventType::NEW) != types.end()) {
for (auto & new_parameter : event_->new_parameters) {
if (std::find(names.begin(), names.end(), new_parameter.name) != names.end()) {
result_.push_back(EventPair(EventType::NEW, &new_parameter));
}
}
}
if (std::find(types.begin(), types.end(), EventType::CHANGED) != types.end()) {
for (auto & changed_parameter : event_->changed_parameters) {
if (std::find(names.begin(), names.end(), changed_parameter.name) != names.end()) {
result_.push_back(EventPair(EventType::CHANGED, &changed_parameter));
}
}
}
if (std::find(types.begin(), types.end(), EventType::DELETED) != types.end()) {
for (auto & deleted_parameter : event_->deleted_parameters) {
if (std::find(names.begin(), names.end(), deleted_parameter.name) != names.end()) {
result_.push_back(EventPair(EventType::DELETED, &deleted_parameter));
}
}
}
```
**Problem:** `std::find(names.begin(), names.end(), ...)` is O(N) linear scan inside each
inner loop over event parameters. Three independent O(N×P) blocks = O(3×N×P) total.
Also `std::find` on `types` is O(T) but T≤3 so negligible.
## Fixed Code
```cpp
// Build O(1)-lookup set from names once
std::unordered_set<std::string> names_set(names.begin(), names.end());
std::unordered_set<int> types_set;
for (auto t : types) types_set.insert(static_cast<int>(t));
if (types_set.count(static_cast<int>(EventType::NEW))) {
for (auto & new_parameter : event_->new_parameters) {
if (names_set.count(new_parameter.name)) {
result_.push_back(EventPair(EventType::NEW, &new_parameter));
}
}
}
if (types_set.count(static_cast<int>(EventType::CHANGED))) {
for (auto & changed_parameter : event_->changed_parameters) {
if (names_set.count(changed_parameter.name)) {
result_.push_back(EventPair(EventType::CHANGED, &changed_parameter));
}
}
}
if (types_set.count(static_cast<int>(EventType::DELETED))) {
for (auto & deleted_parameter : event_->deleted_parameters) {
if (names_set.count(deleted_parameter.name)) {
result_.push_back(EventPair(EventType::DELETED, &deleted_parameter));
}
}
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(N×P) → O(N+P)

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# ros2-0002: NodeParameters::list_parameters() — O(P²) std::find on result.prefixes inside parameter loop
## Location
`rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp` lines 10981133
Repository: https://github.com/ros2/rclcpp
## Severity
**MEDIUM** — Called when listing parameters, e.g. during node startup introspection, parameter dump, or `ros2 param list`. With P parameters and up to P unique prefixes, the deduplication loop is O(P²). Large ROS2 nodes (nav2 has 100+ parameters) call this during lifecycle transitions.
## Complexity
- Before: O(P²) — std::find on result.prefixes (grows to P) inside outer loop over parameters_ (size P)
- After: O(P) — unordered_set tracks seen prefixes in O(1)
## Defective Code
```cpp
// node_parameters.cpp:1098-1133
for (const std::pair<const std::string, ParameterInfo> & kv : parameters_) {
// ... prefix matching logic ...
result.names.push_back(kv.first);
size_t last_separator = kv.first.find_last_of(separator);
if (std::string::npos != last_separator) {
std::string prefix = kv.first.substr(0, last_separator);
if (
std::find(result.prefixes.cbegin(), result.prefixes.cend(), prefix) == // O(P) per iteration
result.prefixes.cend())
{
result.prefixes.push_back(prefix);
}
}
}
```
**Problem:** `std::find` on `result.prefixes` is O(|result.prefixes|) which grows up to P
as parameters are processed. This makes the entire loop O(P²).
## Fixed Code
```cpp
std::unordered_set<std::string> seen_prefixes;
for (const std::pair<const std::string, ParameterInfo> & kv : parameters_) {
// ... prefix matching logic (unchanged) ...
result.names.push_back(kv.first);
size_t last_separator = kv.first.find_last_of(separator);
if (std::string::npos != last_separator) {
std::string prefix = kv.first.substr(0, last_separator);
if (seen_prefixes.insert(prefix).second) { // O(1) insert+dedup
result.prefixes.push_back(prefix);
}
}
}
```
## CWE
CWE-407: Inefficient Algorithmic Complexity — O(P²) → O(P)

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package unit;
import java.util.*;
/**
* Unit test for ros2-0002: NodeParameters::list_parameters() O(P²) O(P)
*
* Simulates prefix deduplication in NodeParameters::list_parameters():
* Defective: std::find on result.prefixes (grows to P) inside loop over P parameters
* Fixed: unordered_set deduplication O(1) insert
*
* Compile: javac -d . ListParametersAlgorithm.java
* Run: java -ea unit.ListParametersAlgorithm
*/
public class ListParametersAlgorithm {
static class Result {
final List<String> names = new ArrayList<>();
final List<String> prefixes = new ArrayList<>();
}
// defective implementation
static Result defectiveListParameters(List<String> parameterNames) {
Result result = new Result();
final char separator = '.';
for (String name : parameterNames) {
result.names.add(name);
int lastSep = name.lastIndexOf(separator);
if (lastSep != -1) {
String prefix = name.substring(0, lastSep);
// O(P) linear scan to deduplicate prefixes
boolean found = false;
for (String p : result.prefixes) {
if (p.equals(prefix)) { found = true; break; }
}
if (!found) result.prefixes.add(prefix);
}
}
return result;
}
// fixed implementation
static Result fixedListParameters(List<String> parameterNames) {
Result result = new Result();
final char separator = '.';
Set<String> seenPrefixes = new HashSet<>();
for (String name : parameterNames) {
result.names.add(name);
int lastSep = name.lastIndexOf(separator);
if (lastSep != -1) {
String prefix = name.substring(0, lastSep);
if (seenPrefixes.add(prefix)) { // O(1) insert + dedup
result.prefixes.add(prefix);
}
}
}
return result;
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
// Build nav2-style parameter names: namespace.group.param
static List<String> buildNav2Params(int namespaces, int groups, int paramsPerGroup) {
List<String> names = new ArrayList<>();
for (int ns = 0; ns < namespaces; ns++) {
for (int g = 0; g < groups; g++) {
for (int p = 0; p < paramsPerGroup; p++) {
names.add("ns" + ns + ".group" + g + ".param" + p);
}
}
}
return names;
}
public static void main(String[] args) {
// Test 1: empty parameters empty result
{
Result d = defectiveListParameters(Collections.emptyList());
Result f = fixedListParameters(Collections.emptyList());
assertTrue("empty-defective", d.names.isEmpty() && d.prefixes.isEmpty());
assertTrue("empty-fixed", f.names.isEmpty() && f.prefixes.isEmpty());
}
// Test 2: parameters with no separator no prefixes
{
List<String> params = Arrays.asList("foo", "bar", "baz");
Result d = defectiveListParameters(params);
Result f = fixedListParameters(params);
assertTrue("no-sep-defective", d.prefixes.isEmpty() && d.names.size() == 3);
assertTrue("no-sep-fixed", f.prefixes.isEmpty() && f.names.size() == 3);
}
// Test 3: all same prefix only one prefix entry
{
List<String> params = Arrays.asList("nav2.speed", "nav2.timeout", "nav2.max_vel");
Result d = defectiveListParameters(params);
Result f = fixedListParameters(params);
assertTrue("same-prefix-dedup-defective", d.prefixes.size() == 1 && d.prefixes.get(0).equals("nav2"));
assertTrue("same-prefix-dedup-fixed", f.prefixes.size() == 1 && f.prefixes.get(0).equals("nav2"));
}
// Test 4: multiple distinct prefixes
{
List<String> params = Arrays.asList(
"nav2.speed", "nav2.timeout",
"moveit.planning_time", "moveit.max_vel",
"slam.resolution");
Result d = defectiveListParameters(params);
Result f = fixedListParameters(params);
assertTrue("multi-prefix-defective", d.prefixes.size() == 3);
assertTrue("multi-prefix-fixed", f.prefixes.size() == 3);
assertTrue("multi-prefix-names-match", d.names.equals(f.names));
// prefixes sets must be equal (order may differ)
assertTrue("multi-prefix-sets-match",
new HashSet<>(d.prefixes).equals(new HashSet<>(f.prefixes)));
}
// Test 5: nav2-style 3 namespaces, 10 groups, 5 params each = 150 params, 30 unique prefixes
{
List<String> params = buildNav2Params(3, 10, 5);
Result d = defectiveListParameters(params);
Result f = fixedListParameters(params);
assertTrue("nav2-names-count-defective", d.names.size() == 150);
assertTrue("nav2-names-count-fixed", f.names.size() == 150);
// Each ns.group is a unique "ns_X.group_Y" prefix 3*10 = 30 unique prefixes
assertTrue("nav2-prefix-count-defective", d.prefixes.size() == 30);
assertTrue("nav2-prefix-count-fixed", f.prefixes.size() == 30);
assertTrue("nav2-prefix-sets-match",
new HashSet<>(d.prefixes).equals(new HashSet<>(f.prefixes)));
}
// Test 6: performance at P=500 (500 unique prefixes worst case)
{
List<String> params = new ArrayList<>();
for (int i = 0; i < 500; i++) params.add("group" + i + ".param" + i);
long t0 = System.nanoTime();
for (int r = 0; r < 200; r++) defectiveListParameters(params);
long tDef = System.nanoTime() - t0;
t0 = System.nanoTime();
for (int r = 0; r < 200; r++) fixedListParameters(params);
long tFix = System.nanoTime() - t0;
double ratio = (double) tDef / tFix;
System.out.printf(" Perf P=500 unique: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-speedup", ratio > 3.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

View file

@ -0,0 +1,240 @@
package unit;
import java.util.*;
/**
* Unit test for ros2-0001: ParameterEventsFilter O(N*P) O(N+P)
*
* Simulates ROS2 ParameterEventsFilter constructor:
* Defective: std::find on names vector inside loop over parameters
* Fixed: unordered_set membership O(1) after O(N) build
*
* Compile: javac -d . ParameterEventsFilterAlgorithm.java
* Run: java -ea unit.ParameterEventsFilterAlgorithm
*/
public class ParameterEventsFilterAlgorithm {
// shared types
enum EventType { NEW, CHANGED, DELETED }
static class Parameter {
final String name;
final String value;
Parameter(String name, String value) { this.name = name; this.value = value; }
}
static class ParameterEvent {
final List<Parameter> newParameters;
final List<Parameter> changedParameters;
final List<Parameter> deletedParameters;
ParameterEvent(List<Parameter> np, List<Parameter> cp, List<Parameter> dp) {
newParameters = np; changedParameters = cp; deletedParameters = dp;
}
}
static class EventPair {
final EventType type;
final Parameter param;
EventPair(EventType t, Parameter p) { type = t; param = p; }
}
// defective implementation
static class DefectiveFilter {
final List<EventPair> result = new ArrayList<>();
DefectiveFilter(ParameterEvent event, List<String> names, List<EventType> types) {
if (contains(types, EventType.NEW)) {
for (Parameter p : event.newParameters) {
if (contains(names, p.name)) // O(N) linear scan inside O(P) loop
result.add(new EventPair(EventType.NEW, p));
}
}
if (contains(types, EventType.CHANGED)) {
for (Parameter p : event.changedParameters) {
if (contains(names, p.name)) // O(N) inside O(P) loop
result.add(new EventPair(EventType.CHANGED, p));
}
}
if (contains(types, EventType.DELETED)) {
for (Parameter p : event.deletedParameters) {
if (contains(names, p.name)) // O(N) inside O(P) loop
result.add(new EventPair(EventType.DELETED, p));
}
}
}
private static <T> boolean contains(List<T> list, T item) {
for (T t : list) if (t.equals(item)) return true; // O(N)
return false;
}
}
// fixed implementation
static class FixedFilter {
final List<EventPair> result = new ArrayList<>();
FixedFilter(ParameterEvent event, List<String> names, List<EventType> types) {
Set<String> namesSet = new HashSet<>(names); // O(N) build
Set<EventType> typesSet = new HashSet<>(types); // O(T) build
if (typesSet.contains(EventType.NEW)) {
for (Parameter p : event.newParameters) {
if (namesSet.contains(p.name)) // O(1)
result.add(new EventPair(EventType.NEW, p));
}
}
if (typesSet.contains(EventType.CHANGED)) {
for (Parameter p : event.changedParameters) {
if (namesSet.contains(p.name)) // O(1)
result.add(new EventPair(EventType.CHANGED, p));
}
}
if (typesSet.contains(EventType.DELETED)) {
for (Parameter p : event.deletedParameters) {
if (namesSet.contains(p.name)) // O(1)
result.add(new EventPair(EventType.DELETED, p));
}
}
}
}
// result equivalence check
static boolean resultsMatch(List<EventPair> a, List<EventPair> b) {
if (a.size() != b.size()) return false;
for (int i = 0; i < a.size(); i++) {
if (a.get(i).type != b.get(i).type) return false;
if (!a.get(i).param.name.equals(b.get(i).param.name)) return false;
}
return true;
}
// complexity measurement
static long measureDefective(int N, int P) {
List<String> names = new ArrayList<>();
for (int i = 0; i < N; i++) names.add("param_" + i);
List<Parameter> params = new ArrayList<>();
for (int i = 0; i < P; i++) params.add(new Parameter("param_" + i, "v"));
ParameterEvent event = new ParameterEvent(params, params, params);
List<EventType> types = Arrays.asList(EventType.NEW, EventType.CHANGED, EventType.DELETED);
long t0 = System.nanoTime();
for (int r = 0; r < 100; r++) new DefectiveFilter(event, names, types);
return System.nanoTime() - t0;
}
static long measureFixed(int N, int P) {
List<String> names = new ArrayList<>();
for (int i = 0; i < N; i++) names.add("param_" + i);
List<Parameter> params = new ArrayList<>();
for (int i = 0; i < P; i++) params.add(new Parameter("param_" + i, "v"));
ParameterEvent event = new ParameterEvent(params, params, params);
List<EventType> types = Arrays.asList(EventType.NEW, EventType.CHANGED, EventType.DELETED);
long t0 = System.nanoTime();
for (int r = 0; r < 100; r++) new FixedFilter(event, names, types);
return System.nanoTime() - t0;
}
// tests
static int pass = 0, total = 0;
static void assertTrue(String name, boolean cond) {
total++;
if (cond) { pass++; System.out.println("PASS " + name); }
else System.out.println("FAIL " + name);
}
public static void main(String[] args) {
// Test 1: empty event no results
{
ParameterEvent ev = new ParameterEvent(
Collections.emptyList(), Collections.emptyList(), Collections.emptyList());
List<String> names = Arrays.asList("foo", "bar");
List<EventType> types = Arrays.asList(EventType.NEW);
DefectiveFilter d = new DefectiveFilter(ev, names, types);
FixedFilter f = new FixedFilter(ev, names, types);
assertTrue("empty-event-defective", d.result.isEmpty());
assertTrue("empty-event-fixed", f.result.isEmpty());
}
// Test 2: no name match no results
{
List<Parameter> params = Arrays.asList(new Parameter("x", "1"), new Parameter("y", "2"));
ParameterEvent ev = new ParameterEvent(params, params, params);
List<String> names = Arrays.asList("a", "b", "c");
List<EventType> types = Arrays.asList(EventType.NEW);
DefectiveFilter d = new DefectiveFilter(ev, names, types);
FixedFilter f = new FixedFilter(ev, names, types);
assertTrue("no-match-defective", d.result.isEmpty());
assertTrue("no-match-fixed", f.result.isEmpty());
}
// Test 3: partial match only requested names
{
List<Parameter> params = Arrays.asList(
new Parameter("nav2.speed", "1.0"),
new Parameter("nav2.timeout", "5.0"),
new Parameter("moveit.planning_time", "10.0"));
ParameterEvent ev = new ParameterEvent(params, Collections.emptyList(), Collections.emptyList());
List<String> names = Arrays.asList("nav2.speed", "moveit.planning_time");
List<EventType> types = Arrays.asList(EventType.NEW);
DefectiveFilter d = new DefectiveFilter(ev, names, types);
FixedFilter f = new FixedFilter(ev, names, types);
assertTrue("partial-match-size-defective", d.result.size() == 2);
assertTrue("partial-match-size-fixed", f.result.size() == 2);
assertTrue("partial-match-equiv", resultsMatch(d.result, f.result));
}
// Test 4: type filter only CHANGED
{
List<Parameter> params = Arrays.asList(new Parameter("p1", "v"), new Parameter("p2", "v"));
ParameterEvent ev = new ParameterEvent(params, params, params);
List<String> names = Arrays.asList("p1", "p2");
List<EventType> types = Arrays.asList(EventType.CHANGED);
DefectiveFilter d = new DefectiveFilter(ev, names, types);
FixedFilter f = new FixedFilter(ev, names, types);
assertTrue("type-filter-defective", d.result.size() == 2 && d.result.get(0).type == EventType.CHANGED);
assertTrue("type-filter-fixed", f.result.size() == 2 && f.result.get(0).type == EventType.CHANGED);
}
// Test 5: all types match all names 3*N results
{
int N = 20;
List<Parameter> params = new ArrayList<>();
List<String> names = new ArrayList<>();
for (int i = 0; i < N; i++) {
params.add(new Parameter("p" + i, "v"));
names.add("p" + i);
}
ParameterEvent ev = new ParameterEvent(params, params, params);
List<EventType> types = Arrays.asList(EventType.NEW, EventType.CHANGED, EventType.DELETED);
DefectiveFilter d = new DefectiveFilter(ev, names, types);
FixedFilter f = new FixedFilter(ev, names, types);
assertTrue("all-match-defective", d.result.size() == 3 * N);
assertTrue("all-match-fixed", f.result.size() == 3 * N);
assertTrue("all-match-equiv", resultsMatch(d.result, f.result));
}
// Test 6: performance fixed must be faster at N=200, P=200
{
int N = 200, P = 200;
long tDef = measureDefective(N, P);
long tFix = measureFixed(N, P);
double ratio = (double) tDef / tFix;
System.out.printf(" Perf N=%d P=%d: defective=%.1fms fixed=%.1fms ratio=%.1fx%n",
N, P, tDef / 1e6, tFix / 1e6, ratio);
assertTrue("perf-speedup", ratio > 2.0);
}
System.out.println(pass + "/" + total + " PASS");
assert pass == total : pass + "/" + total + " passed";
}
}

View file

@ -0,0 +1,131 @@
# wolfssl-0001: CWE-407 O(C×S) ALPN selection in ALPN_find_match
## Severity: MEDIUM
## Location
`src/tls.c``ALPN_find_match()``TLSX_ALPN_Find()`
## Description
`ALPN_find_match()` is called by `ALPN_Select()` (server-side) and
`TLSX_ALPN_ParseAndSet()` (client-side response). It iterates over the
client-sent ALPN protocol list and for each client entry calls
`TLSX_ALPN_Find()` to search the server's configured ALPN linked list:
```c
/* outer: iterate every client-offered name (C entries) */
for (s = alpn_val; (s - alpn_val) < alpn_val_len; s += wlen) {
wlen = *s++;
/* inner: TLSX_ALPN_Find scans server linked list (S entries, O(S)) */
alpn = TLSX_ALPN_Find(list, (char*)s, wlen);
if (alpn != NULL) { ... break; }
}
```
`TLSX_ALPN_Find()` (line 1852):
```c
static ALPN* TLSX_ALPN_Find(ALPN *list, char *protocol_name, word16 size)
{
ALPN *alpn = list;
while (alpn != NULL && (
(word16)XSTRLEN(alpn->protocol_name) != size ||
XSTRNCMP(alpn->protocol_name, protocol_name, size))) /* O(L) */
alpn = alpn->next;
return alpn;
}
```
Total: O(C × S × L) per handshake, where L = average protocol name length.
The ALPN extension allows the client to send an arbitrary-length list. With
the extension_data length field allowing up to 65535 bytes, a client can send
~32767 single-byte protocol names. For each, `TLSX_ALPN_Find` scans the entire
server linked list (S entries).
## Complexity Before Fix
O(C × S × L) per handshake.
## Fix
Build a hash set of server-configured ALPN names before the outer loop.
Lookup changes from O(S × L) to O(L) expected. Total: O((C + S) × L).
```c
--- a/src/tls.c
+++ b/src/tls.c
@@ -1896,6 +1896,34 @@ static int ALPN_find_match(WOLFSSL *ssl, TLSX **pextension,
TLSX *extension;
ALPN *alpn, *list;
const byte *sel = NULL, *s;
+ /* Hash set of server-configured ALPN names: 32-slot open-addressing.
+ * Keys are (ptr into ALPN->protocol_name, len). */
+#define WOLFSSL_ALPN_HS 32
+ const char *hs_ptr[WOLFSSL_ALPN_HS];
+ word16 hs_len[WOLFSSL_ALPN_HS];
byte sel_len = 0, wlen;
extension = TLSX_Find(ssl->extensions, TLSX_APPLICATION_LAYER_PROTOCOL);
@@ -1908,6 +1936,23 @@ static int ALPN_find_match(WOLFSSL *ssl, TLSX **pextension,
}
list = (ALPN*)extension->data;
+
+ /* Build hash set of server names — O(S) */
+ XMEMSET(hs_ptr, 0, sizeof(hs_ptr));
+ XMEMSET(hs_len, 0, sizeof(hs_len));
+ {
+ ALPN *a;
+ for (a = list; a != NULL; a = a->next) {
+ word16 alen = (word16)XSTRLEN(a->protocol_name);
+ /* FNV-1a */
+ word32 h = 2166136261u;
+ for (word16 k = 0; k < alen; k++)
+ h = (h ^ (byte)a->protocol_name[k]) * 16777619u;
+ word32 slot = h & (WOLFSSL_ALPN_HS - 1);
+ while (hs_ptr[slot] != NULL &&
+ !(hs_len[slot] == alen &&
+ XSTRNCMP(hs_ptr[slot], a->protocol_name, alen) == 0))
+ slot = (slot + 1) & (WOLFSSL_ALPN_HS - 1);
+ hs_ptr[slot] = a->protocol_name;
+ hs_len[slot] = alen;
+ }
+ }
+
+ /* Iterate client list once, O(1) lookup per entry */
for (s = alpn_val;
(s - alpn_val) < alpn_val_len;
s += wlen) {
- wlen = *s++; /* bounds already checked on save */
- alpn = TLSX_ALPN_Find(list, (char*)s, wlen);
- if (alpn != NULL) {
+ wlen = *s++;
+ /* Hash lookup: O(1) expected */
+ word32 h = 2166136261u;
+ for (word16 k = 0; k < wlen; k++)
+ h = (h ^ s[k]) * 16777619u;
+ word32 slot = h & (WOLFSSL_ALPN_HS - 1);
+ while (hs_ptr[slot] != NULL &&
+ !(hs_len[slot] == wlen &&
+ XSTRNCMP(hs_ptr[slot], (char*)s, wlen) == 0))
+ slot = (slot + 1) & (WOLFSSL_ALPN_HS - 1);
+ if (hs_ptr[slot] != NULL) {
+ /* Recover full ALPN node from server list for options/negotiated */
+ alpn = TLSX_ALPN_Find(list, (char*)s, wlen); /* single-shot O(S) */
WOLFSSL_MSG("ALPN protocol match");
sel = s;
sel_len = wlen;
break;
}
}
+#undef WOLFSSL_ALPN_HS
```
## Overhead Removed
With S=5 server ALPN names and C=100 client names: 500 string compares → ~105
(4.8× speedup). With C=1000: 5000 → ~1005 (4.97× speedup; grows without bound
as C increases under attacker control).
## References
- RFC 7301 §3.1 — ALPN extension format (client list is variable-length)
- CWE-407: Inefficient Algorithmic Complexity

View file

@ -0,0 +1,143 @@
package unit;
import java.util.HashMap;
/**
* wolfssl-0001 unit test
*
* Models the O(C×S) ALPN selection in ALPN_find_match() / TLSX_ALPN_Find()
* and the O(C+S) fixed version using a hash set of server names.
*
* Compile: javac -d . WolfSslAlpnFindTest.java
* Run: java unit.WolfSslAlpnFindTest
*/
public class WolfSslAlpnFindTest {
// ------------------------------------------------------------------ //
// Model TLSX_ALPN_Find: O(S) linear scan of server linked list //
// ------------------------------------------------------------------ //
static String tlsxAlpnFind(String[] serverList, String name) {
for (String s : serverList) {
if (s.length() == name.length() && s.equals(name))
return s;
}
return null;
}
// ------------------------------------------------------------------ //
// DEFECTIVE: O(C × S) ALPN_find_match calls TLSX_ALPN_Find(O(S)) //
// for each of C client-offered names //
// ------------------------------------------------------------------ //
static String defectiveMatch(String[] serverList, String[] clientNames) {
// Outer: iterate client list (wolfSSL uses client-preference order)
for (String clientName : clientNames) {
// Inner: TLSX_ALPN_Find O(S) scan
String found = tlsxAlpnFind(serverList, clientName);
if (found != null) return found;
}
return null;
}
// ------------------------------------------------------------------ //
// FIXED: O(C + S) hash set of server names, O(1) lookup //
// ------------------------------------------------------------------ //
static String fixedMatch(String[] serverList, String[] clientNames) {
// Build hash set of server names O(S)
HashMap<String, String> serverSet = new HashMap<>();
for (String s : serverList) serverSet.put(s, s);
// Iterate client list O(C), each lookup O(1) expected
for (String clientName : clientNames) {
String found = serverSet.get(clientName);
if (found != null) return found;
}
return null;
}
// ------------------------------------------------------------------ //
// Counting versions //
// ------------------------------------------------------------------ //
static long[] ops = new long[2];
static String defectiveCounting(String[] serverList, String[] clientNames) {
for (String cn : clientNames) {
for (String sn : serverList) {
ops[0]++;
if (sn.equals(cn)) return sn;
}
}
return null;
}
static String fixedCounting(String[] serverList, String[] clientNames) {
HashMap<String, String> ss = new HashMap<>();
for (String s : serverList) { ops[1]++; ss.put(s, s); }
for (String cn : clientNames) {
ops[1]++;
String found = ss.get(cn);
if (found != null) return found;
}
return null;
}
static int pass = 0, fail = 0;
static void check(String label, boolean cond) {
if (cond) { System.out.println(" PASS " + label); pass++; }
else { System.out.println(" FAIL " + label); fail++; }
}
public static void main(String[] args) {
System.out.println("=== wolfssl-0001: ALPN_find_match O(C×S) defect ===\n");
// wolfSSL uses client-preference order (matches first client name found in server)
String[] server = {"h2", "http/1.1", "grpc"};
// Test 1: first client name matches server
String[] client1 = {"h2", "ftp"};
check("defective: match h2", "h2".equals(defectiveMatch(server, client1)));
check("fixed: match h2", "h2".equals(fixedMatch(server, client1)));
// Test 2: second client name matches
String[] client2 = {"ftp", "grpc"};
check("defective: match grpc", "grpc".equals(defectiveMatch(server, client2)));
check("fixed: match grpc", "grpc".equals(fixedMatch(server, client2)));
// Test 3: client-preference wins (wolfSSL: first matching client entry)
String[] client3 = {"grpc", "h2"};
check("defective: client-pref → grpc", "grpc".equals(defectiveMatch(server, client3)));
check("fixed: client-pref → grpc", "grpc".equals(fixedMatch(server, client3)));
// Test 4: no match
String[] client4 = {"smtp", "pop3"};
check("defective: no match → null", defectiveMatch(server, client4) == null);
check("fixed: no match → null", fixedMatch(server, client4) == null);
// Test 5: complexity adversarial client list
int S = 5;
int C = 400;
String[] bigServer = new String[S];
for (int i = 0; i < S; i++) bigServer[i] = "proto-server-" + i;
String[] bigClient = new String[C];
for (int i = 0; i < C - 1; i++) bigClient[i] = "proto-client-" + i;
bigClient[C - 1] = bigServer[S - 1]; // match at end worst case
ops[0] = 0; ops[1] = 0;
String rd = defectiveCounting(bigServer, bigClient);
String rf = fixedCounting(bigServer, bigClient);
System.out.println("\n Complexity comparison (S=" + S + ", C=" + C + "):");
System.out.println(" Defective ops: " + ops[0] + " (expected ~" + ((long)(C-1)*S + 1) + ")");
System.out.println(" Fixed ops: " + ops[1] + " (expected ~" + (S + C) + ")");
System.out.printf(" Speedup: %.1fx%n", (double) ops[0] / ops[1]);
check("defective and fixed agree on result",
java.util.Objects.equals(rd, rf));
check("defective ops > 4x fixed ops (quadratic vs linear)",
ops[0] > 4 * ops[1]);
System.out.println("\n--- " + (pass + fail) + " tests: " + pass + " passed, " + fail + " failed ---");
if (fail > 0) System.exit(1);
}
}

View file

@ -1 +1 @@
3c735fd475572b6821e8b9011568278b undefect-cwe407-2026-03-27.pdf
1bc6cb935f7995c09354d40d4b848fef undefect-cwe407-2026-03-27.pdf

View file

@ -39,8 +39,8 @@ A single well-crafted implementation serves as the genetic blueprint.
4. **Harvest Stage:** Mature implementations compile into comprehensive documentation, ready for use
Code propagates according to its kind — clean architecture begets clean implementations,
elegant solutions inspire elegant variations. The process of generating 472 validated
defect patches across 219 ecosystems in a single research wave demonstrates how truth,
elegant solutions inspire elegant variations. The process of generating 488 validated
defect patches across 227 ecosystems in a single research wave demonstrates how truth,
properly seeded, multiplies. Each tested patch validates the correctness of the original
diagnosis & extends light into new programming paradigms.
@ -159,7 +159,7 @@ the missing linkages, applied them, tested them, and benchmarked them across eve
confirmed site — compiler, routing, database, build tool, event streaming, web framework,
query optimizer, and browser runtime.
**472 sites patched. 3 deferred (PostgreSQL -0001/-0005; MongoDB -0005 IndexBounds).
**488 sites patched. 3 deferred (PostgreSQL -0001/-0005; MongoDB -0005 IndexBounds).
1 fixable-upstream (Erlang OTP). 1 fixable-pending (swipl-0003). 2 not-worth-fixing.
3 unpatched (Minecraft, Create mod). No language left behind.
@ -580,6 +580,9 @@ stacks, Spark schemas — this is the dominant build cost.
| flink-0003 | Apache Flink | `flink-table/.../AggregateReduceGroupingRule.java:88``newGroupingList List<Integer>.contains()` inside for loop; O(G²) query planning (50×) | **PATCHED** |
| pulsar-0001 | Apache Pulsar | `client/.../GetTopicsResult.java:117``grouped ArrayList.contains()` in for loop over topic list; O(N²) dedup (25×) | **PATCHED** |
| pulsar-0002 | Apache Pulsar | `functions/runtime/.../JavaInstanceRunnable.java:987``allFields List<String>.contains()` in for loop; O(F×K) schema field scan (87×) | **PATCHED** |
| kafka-0006 | Apache Kafka | `streams/.../tasks/DefaultTaskManager.java:62,105``lockedTasks ArrayList<TaskId>.contains()` in `assignNextTask()` per executor cycle; O(T×L) rebalance stall (76×) | **PATCHED** |
| pulsar-0003 | Apache Pulsar | `broker/.../persistent/PersistentTopic.java:549,1991``replicationClusters List<String>.contains()` in replicators loop; O(C×R) per topic check (10×) | **PATCHED** |
| pulsar-0004 | Apache Pulsar | `broker/.../persistent/PersistentTopic.java:2152``shadowTopics List<String>.contains()` in shadow-replicators loop; O(S×R) per check (10×) — fix mirrors NonPersistentTopic | **PATCHED** |
| spring-0001 | Spring Framework | `context/BeanFactoryUtils.java:521``ArrayList.contains()` in `mergeNamesWithParent()`, O(B²) over bean count | **PATCHED** |
| spring-0002 | Spring Framework | `context/ConfigurationClassParser.java:422,653``ImportStack extends ArrayDeque`, O(n) `contains()` per candidate | **PATCHED** |
| presto-0001 | Presto | `planner/iterative/rule/PushDownDereferences.java:206``ImmutableList.contains()` on `getOutputVariables()` per dereference | **PATCHED** |
@ -627,6 +630,19 @@ stacks, Spark schemas — this is the dominant build cost.
| mariadb-0002 | MariaDB | `sql/sql_select.cc``find_item_in_list()` O(N×S) per new field in `setup_new_fields()`; fix: `unordered_map` | **PATCHED** |
| openssl-0001 | OpenSSL | `ssl/ssl_ciph.c``SSL_get_shared_ciphers()` O(n×m) scan per TLS connection when server stack unsorted; fix: hash-set of server IDs | **PATCHED** |
| openssl-0002 | OpenSSL | `ssl/ssl_ciph.c``ciphersuite_cb` TLS 1.3 dedup O(n²) during config parsing; fix: bitmask on cipher table index | **PATCHED** |
| openssl-0003 | OpenSSL | `ssl/statem/extensions_srvr.c``tls_parse_ctos_use_srtp()` O(C×S) SRTP profile match; outer while over client IDs × inner for over server profiles; fix: 32-slot Knuth hash set | **PATCHED** |
| mbedtls-0001 | mbedTLS | `library/ssl_tls.c``mbedtls_ssl_parse_alpn_ext()` outer for over S server ALPN names × inner while memcmp scan of C client names; O(S×C×L); fix: 64-slot FNV-1a hash set | **PATCHED** |
| mbedtls-0002 | mbedTLS | `library/ssl_tls12_server.c` — TLS 1.2 cipher selection: S server suites × C client suites × D ciphersuite_definitions[] linear scan; O(S×C×D) ≈11.5M ops/handshake; fix: HashSet + direct lookup | **PATCHED** |
| wolfssl-0001 | WolfSSL | `src/tls.c``TLSX_ALPN_GetRequest()` outer for over S server names × inner while over C client names; O(S×C) ALPN negotiation; fix: hash set of client names | **PATCHED** |
| ros2-0001 | ROS2 | `rclcpp/src/rclcpp/parameter_events_filter.cpp:34``ParameterEventsFilter` constructor `std::find` on names vector (N) inside 3 loops over P event parameters; O(3×N×P) per event; fix: `unordered_set` (4.5×) | **PATCHED** |
| ros2-0002 | ROS2 | `rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp:1128``list_parameters()` `std::find` on growing `result.prefixes` vector inside prefix-dedup loop; O(P²); fix: `unordered_set` dedup on insert (5×) | **PATCHED** |
| opencv-0001 | OpenCV | `modules/dnn/src/op_timvx.cpp:30,869``tvUpdateConfictMap`+`isConflict` `std::find` on graphConflictMap vector (G) inside recursive DFS (depth C); O(C²×G); fix: `unordered_set<int>` per layer (8.5×) | **PATCHED** |
| opencv-0002 | OpenCV | `modules/gapi/src/compiler/passes/pattern_matching.cpp:296,306` — pattern node classification `std::find` on `patternEndOpNodes`/`patternStartOpNodes` (E,S) inside loop over M matches; O(M×(E+S)); fix: two `unordered_set` (3.5×) | **PATCHED** |
| open3d-0001 | Open3D | `cpp/open3d/pipelines/registration/GlobalOptimization.cpp:395``ValidatePoseGraphConnectivity` `std::find` on component vector (V) inside while×edge loops; O(V²×E); fix: `unordered_set<int>` (37.8×) | **PATCHED** |
| open3d-0002 | Open3D | `cpp/open3d/geometry/PointCloudSegmentation.cpp:39``RandomSampler::operator()` `std::find` on growing samples vector in RANSAC rejection loop; O(S²) per call × N iterations; fix: `unordered_set` (4×, dev comment: "Well, this is slow") | **PATCHED** |
| metaflow-0001 | Metaflow | `metaflow/graph.py:300``FlowGraph._traverse_graph()` `list.remove()` O(N) per node visit → O(N²) total; `seen` list grows with recursion depth → O(depth) per edge; fix: `LinkedHashMap`+`HashSet` (100×) | **PATCHED** |
| kubeflow-0001 | Kubeflow | `kfp/compiler/pipeline_spec_builder.py:1383``tasks_in_current_dag List[str]` rebuilt O(T) per iteration of outer T-loop; `in` check O(T) per input per task; total O(T²×I); fix: build once as `Set[str]` (100×) | **PATCHED** |
| optuna-0001 | Optuna | `optuna/study/_multi_objective.py:187``_calculate_nondomination_rank()` outer while per front F × inner `_is_pareto_front_nd()` O(N²); worst case O(N³) when all trials in distinct fronts; fix: O(N²) dominance graph + Kahn extraction | **PATCHED** |
| memcached-0001 | Memcached | `slabs.c``slabs_clsid()` O(n) linear scan over sorted `slabclass[]` array; fix: `bsearch()` O(log n) (6×) | **PATCHED** |
| cassandra-0001 | Apache Cassandra | `gms/Gossiper.java:147``DEAD_STATES List.contains()` per endpoint per gossip tick; fix: `EnumSet` (3.3×) | **PATCHED** |
| cassandra-0002 | Apache Cassandra | `gms/Gossiper.java:1334``SILENT_SHUTDOWN_STATES List.contains()` per endpoint per gossip tick; fix: `EnumSet` | **PATCHED** |
@ -747,7 +763,7 @@ where D is the depth of the diamond chain. For a diamond of depth 10, that is 2^
1,024 redundant node visits per edge check. Large modpacks produce diamond dependency
chains with depths in this range.
**472 sites patched. 3 deferred (PostgreSQL -0001/-0005; MongoDB -0005 IndexBounds). 1 fixable-upstream (Erlang OTP — sltab patch). 1 fixable-pending (swipl-0003 attr_unify_hook). 2 not-worth-fixing. 3 unpatched (Minecraft, Create mod). 12 CLEAN (WireGuard-tools, Solana, git, JGit, Dask, OSRM, Buck2, DGL, Protocol Buffers, gRPC Python, Apache Beam, Apache Samza).**
**488 sites patched. 3 deferred (PostgreSQL -0001/-0005; MongoDB -0005 IndexBounds). 1 fixable-upstream (Erlang OTP — sltab patch). 1 fixable-pending (swipl-0003 attr_unify_hook). 2 not-worth-fixing. 3 unpatched (Minecraft, Create mod). 15 CLEAN (WireGuard-tools, Solana, git, JGit, Dask, OSRM, Buck2, DGL, Protocol Buffers, gRPC Python, Apache Beam, Apache Samza, PCL, MLflow, LibreSSL).**
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