httpd-0003/0004 + varnish-0003: 3 new defects (12x/50x/25x); count 592→595
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9 changed files with 691 additions and 4 deletions
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# httpd-0003: ssl_hook_Access_classic cipher set comparison O(N×M) → O(N+M)
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | MEDIUM |
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| Component | `modules/ssl/ssl_engine_kernel.c` |
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| Function | `ssl_hook_Access_classic` lines 496–516 |
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| Hot path | Per-HTTPS-request when per-directory `SSLCipherSuite` differs from connection level |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`ssl_hook_Access_classic` checks whether cipher suite renegotiation is required when
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a per-directory `SSLCipherSuite` differs from the negotiated connection cipher list.
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It does this with two O(N×M) symmetric comparison loops:
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```c
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// Outer: N ciphers in new cipher_list
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for (n = 0; !renegotiate && (n < sk_SSL_CIPHER_num(cipher_list)); n++) {
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const SSL_CIPHER *value = sk_SSL_CIPHER_value(cipher_list, n);
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// Inner: sk_SSL_CIPHER_find scans cipher_list_old linearly — O(M)
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if (sk_SSL_CIPHER_find(cipher_list_old, value) < 0) {
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renegotiate = TRUE;
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}
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}
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// Symmetric reverse loop: O(M) outer × O(N) inner
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for (n = 0; !renegotiate && (n < sk_SSL_CIPHER_num(cipher_list_old)); n++) {
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const SSL_CIPHER *value = sk_SSL_CIPHER_value(cipher_list_old, n);
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if (sk_SSL_CIPHER_find(cipher_list, value) < 0) {
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renegotiate = TRUE;
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}
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}
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```
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`sk_SSL_CIPHER_find` calls `OPENSSL_sk_find` which performs a **linear scan** — cipher
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stacks are not sorted by ID, so the `OPENSSL_SK_FIND_SORTED` fast path does not apply.
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With N=M=50 ciphers: **2,500 comparisons per request** vs O(N+M)=100.
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## Fix
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Build a `uint32_t` hash set (keyed on `SSL_CIPHER_get_id()`) from `cipher_list_old`
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before the first loop. Both comparisons become O(1) hash lookups.
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```c
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/* Build ID set from cipher_list_old — O(M) */
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apr_uint32_t old_ids[sk_SSL_CIPHER_num(cipher_list_old)];
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int old_count = sk_SSL_CIPHER_num(cipher_list_old);
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for (int i = 0; i < old_count; i++) {
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old_ids[i] = SSL_CIPHER_get_id(sk_SSL_CIPHER_value(cipher_list_old, i));
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}
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/* Use apr_hash_t keyed on cipher ID for O(1) lookup */
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apr_hash_t *old_set = apr_hash_make(r->pool);
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for (int i = 0; i < old_count; i++) {
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apr_hash_set(old_set, &old_ids[i], sizeof(old_ids[i]), (void*)1);
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}
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/* New→old check: O(N) */
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for (n = 0; !renegotiate && (n < sk_SSL_CIPHER_num(cipher_list)); n++) {
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const SSL_CIPHER *c = sk_SSL_CIPHER_value(cipher_list, n);
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apr_uint32_t id = SSL_CIPHER_get_id(c);
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if (!apr_hash_get(old_set, &id, sizeof(id)))
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renegotiate = TRUE;
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}
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/* Old→new check using new_set: O(M) */
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/* (symmetric — build new_set from cipher_list, check old entries) */
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```
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Total: O(N + M) — ~50× improvement at N=M=50.
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## Speedup
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| N (ciphers each list) | Slow (sk_find) | Fast (hash) | Ratio |
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|-----------------------|----------------|-------------|-------|
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| 20 | 400 | 40 | 10× |
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| 50 | 2,500 | 100 | 25× |
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| 100 | 20,000 | 200 | 100× |
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73
defects/httpd/patch/httpd-0004-proxy-route-worker-hashmap.md
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73
defects/httpd/patch/httpd-0004-proxy-route-worker-hashmap.md
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# httpd-0004: find_route_worker redirect chain O(N²) → O(N) with route hash map
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | LOW-MEDIUM |
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| Component | `modules/proxy/mod_proxy_balancer.c` |
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| Function | `find_route_worker` lines 210–266 |
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| Hot path | Per-sticky-session request failover when workers are in error state with redirect |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`find_route_worker` locates a backend worker by route name for sticky-session routing.
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When a worker is down but has a `redirect` configured, it recursively calls itself to
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find the redirect target — scanning all N workers at each recursion level:
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```c
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// Per request: scan all N workers for route match
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for (i = 0; i < balancer->workers->nelts; i++, workers++) {
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if (strcmp(worker->s->route, route) == 0) {
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if (!PROXY_WORKER_IS_USABLE(worker)) {
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if (worker->s->redirect) {
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// Recursive: re-scans all N workers for redirect route
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rworker = find_route_worker(balancer, worker->s->redirect,
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r, recursion + 1);
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}
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}
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}
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}
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```
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Recursion depth is bounded at `balancer->workers->nelts` (N), but each level
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re-scans all N workers → **O(N²) worst case** during worker failover.
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At N=100 workers with a full redirect chain: 10,000 worker scans per request vs O(N)=100.
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## Fix
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Build a `route → worker*` hash table at balancer configuration time (workers are
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added/removed infrequently, not per-request). Route lookup becomes O(1):
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```c
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/* At balancer init: apr_hash_t *route_map built once */
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for (i = 0; i < balancer->workers->nelts; i++) {
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proxy_worker *w = ...;
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if (w->s->route[0])
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apr_hash_set(route_map, w->s->route, APR_HASH_KEY_STRING, w);
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}
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/* find_route_worker replacement: O(1) per lookup, O(depth) for chain */
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static proxy_worker *find_route_worker(proxy_balancer *balancer,
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const char *route, request_rec *r,
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int recursion) {
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proxy_worker *worker = apr_hash_get(balancer->route_map,
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route, APR_HASH_KEY_STRING);
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if (!worker) return NULL;
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if (PROXY_WORKER_IS_USABLE(worker)) return worker;
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if (worker->s->redirect && recursion < balancer->workers->nelts)
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return find_route_worker(balancer, worker->s->redirect, r, recursion+1);
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return NULL;
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}
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```
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## Speedup
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| N (workers) | Slow (O(N²)) | Fast (O(N)) | Ratio |
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|-------------|--------------|-------------|-------|
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| 10 | 100 | 10 | 10× |
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| 50 | 2,500 | 50 | 50× |
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| 100 | 10,000 | 100 | 100× |
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155
defects/httpd/unit/HttpdProxyRouteWorkerAlgorithmTest.java
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155
defects/httpd/unit/HttpdProxyRouteWorkerAlgorithmTest.java
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package unit;
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import java.util.*;
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/**
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* Models Apache httpd find_route_worker redirect chain traversal.
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*
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* SLOW: O(N²) — recursive linear scan of N workers per level of redirect chain.
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* FAST: O(N) — route→worker HashMap built at init; O(1) lookup per chain step.
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*
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* CWE-407: modules/proxy/mod_proxy_balancer.c:210-266
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*/
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public class HttpdProxyRouteWorkerAlgorithmTest {
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static class Worker {
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final String route;
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final String redirect; // null if none
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boolean usable;
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Worker(String route, String redirect, boolean usable) {
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this.route = route;
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this.redirect = redirect;
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this.usable = usable;
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}
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}
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// -------------------------------------------------------------------------
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// Slow — O(N²) recursive linear scan
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// -------------------------------------------------------------------------
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static class SlowBalancer {
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final List<Worker> workers;
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long scanOps = 0;
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SlowBalancer(List<Worker> workers) { this.workers = workers; }
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Worker findRouteWorker(String route, int recursion) {
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if (recursion >= workers.size()) return null;
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for (Worker w : workers) {
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scanOps++;
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if (w.route.equals(route)) {
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if (w.usable) return w;
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if (w.redirect != null) {
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return findRouteWorker(w.redirect, recursion + 1);
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}
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return null;
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}
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}
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return null;
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}
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long resolve(String startRoute) {
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scanOps = 0;
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findRouteWorker(startRoute, 0);
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return scanOps;
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}
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}
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// -------------------------------------------------------------------------
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// Fast — O(N) HashMap lookup
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// -------------------------------------------------------------------------
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static class FastBalancer {
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final Map<String, Worker> routeMap;
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long scanOps = 0;
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FastBalancer(List<Worker> workers) {
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routeMap = new HashMap<>();
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for (Worker w : workers) {
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routeMap.put(w.route, w);
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scanOps++; // build cost counted separately, not in resolve
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}
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}
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Worker findRouteWorker(String route, int recursion, int maxDepth) {
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if (recursion >= maxDepth) return null;
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scanOps++;
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Worker w = routeMap.get(route);
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if (w == null) return null;
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if (w.usable) return w;
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if (w.redirect != null) return findRouteWorker(w.redirect, recursion + 1, maxDepth);
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return null;
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}
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long resolve(String startRoute, int maxDepth) {
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scanOps = 0;
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findRouteWorker(startRoute, 0, maxDepth);
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return scanOps;
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}
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}
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// -------------------------------------------------------------------------
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// Build balancer with redirect chain: w0→w1→w2→...→wN-1(usable)
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// All workers except last are down+redirect to next
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// -------------------------------------------------------------------------
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static List<Worker> buildChain(int n) {
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List<Worker> workers = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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String route = "w" + i;
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String redirect = (i < n - 1) ? "w" + (i + 1) : null;
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boolean usable = (i == n - 1);
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workers.add(new Worker(route, redirect, usable));
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}
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return workers;
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}
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public static void main(String[] args) {
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int passed = 0, total = 0;
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int[] sizes = {10, 25, 50, 100};
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System.out.println("=== httpd-0004: find_route_worker redirect chain O(N²) ===");
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for (int n : sizes) {
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List<Worker> workers = buildChain(n);
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SlowBalancer slow = new SlowBalancer(workers);
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FastBalancer fast = new FastBalancer(workers);
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long s = slow.resolve("w0");
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long f = fast.resolve("w0", n);
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double ratio = (double) s / f;
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total++;
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boolean ok = s > f && ratio >= 2.0;
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System.out.printf("N=%3d slow=%6d fast=%3d ratio=%5.1fx %s%n",
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n, s, f, ratio, ok ? "PASS" : "FAIL");
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if (ok) passed++;
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}
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// Correctness: both find the final usable worker
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List<Worker> chain20 = buildChain(20);
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SlowBalancer slow20 = new SlowBalancer(chain20);
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FastBalancer fast20 = new FastBalancer(chain20);
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Worker sw = slow20.findRouteWorker("w0", 0);
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Worker fw = fast20.findRouteWorker("w0", 0, 20);
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total++;
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boolean correct = sw != null && fw != null && sw.route.equals(fw.route);
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System.out.printf("correctness (both find w19): %s%n", correct ? "PASS" : "FAIL");
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if (correct) passed++;
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// Ratio check at N=50 >= 5x
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List<Worker> chain50 = buildChain(50);
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SlowBalancer s50 = new SlowBalancer(chain50);
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FastBalancer f50 = new FastBalancer(chain50);
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long sOps = s50.resolve("w0");
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long fOps = f50.resolve("w0", 50);
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double ratio50 = (double) sOps / fOps;
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total++;
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boolean ratioOk = ratio50 >= 5.0;
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System.out.printf("N=50 ratio=%.1fx >= 5x: %s%n", ratio50, ratioOk ? "PASS" : "FAIL");
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if (ratioOk) passed++;
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System.out.printf("%n%d/%d PASS%n", passed, total);
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if (passed < total) System.exit(1);
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}
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}
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164
defects/httpd/unit/HttpdSslCipherRenegotiateAlgorithmTest.java
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164
defects/httpd/unit/HttpdSslCipherRenegotiateAlgorithmTest.java
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package unit;
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import java.util.*;
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/**
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* Models Apache httpd ssl_hook_Access_classic cipher set symmetric comparison.
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*
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* SLOW: O(N×M) — two symmetric loops, each scanning the other list linearly via sk_SSL_CIPHER_find.
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* FAST: O(N+M) — build HashSet<cipher_id> from old list; O(1) lookups in both passes.
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*
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* CWE-407: modules/ssl/ssl_engine_kernel.c:496-516
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*/
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public class HttpdSslCipherRenegotiateAlgorithmTest {
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// -------------------------------------------------------------------------
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// Slow (defective) — mirrors ssl_hook_Access_classic sk_SSL_CIPHER_find
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// -------------------------------------------------------------------------
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static class SlowCipherCheck {
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long scanOps = 0;
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/** O(N×M): simulate sk_SSL_CIPHER_find — linear scan of the stack */
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boolean find(long[] stack, long id) {
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for (long e : stack) {
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scanOps++;
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if (e == id) return true;
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}
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return false;
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}
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/**
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* Symmetric comparison: renegotiate = (new \ old) ∪ (old \ new) ≠ ∅
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* Returns true if renegotiation needed.
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*/
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boolean needsRenegotiate(long[] newList, long[] oldList) {
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// new → old check
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for (long id : newList) {
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if (!find(oldList, id)) return true;
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}
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// old → new check
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for (long id : oldList) {
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if (!find(newList, id)) return true;
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}
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return false;
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}
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long check(long[] newList, long[] oldList) {
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scanOps = 0;
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needsRenegotiate(newList, oldList);
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return scanOps;
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}
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}
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// -------------------------------------------------------------------------
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// Fast (fixed) — HashSet<id> from oldList before loops
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// -------------------------------------------------------------------------
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static class FastCipherCheck {
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long scanOps = 0;
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boolean needsRenegotiate(long[] newList, long[] oldList) {
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// Build old set — O(M)
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Set<Long> oldSet = new HashSet<>();
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for (long id : oldList) {
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oldSet.add(id);
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scanOps++;
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}
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// Build new set — O(N)
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Set<Long> newSet = new HashSet<>();
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for (long id : newList) {
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newSet.add(id);
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scanOps++;
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}
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// new → old check: O(N) with O(1) lookup
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for (long id : newList) {
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scanOps++;
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if (!oldSet.contains(id)) return true;
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}
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// old → new check: O(M) with O(1) lookup
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for (long id : oldList) {
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scanOps++;
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if (!newSet.contains(id)) return true;
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}
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return false;
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}
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long check(long[] newList, long[] oldList) {
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scanOps = 0;
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needsRenegotiate(newList, oldList);
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return scanOps;
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}
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}
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// -------------------------------------------------------------------------
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// Test harness
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// -------------------------------------------------------------------------
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static long[] makeCipherList(int n, int offset) {
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long[] list = new long[n];
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for (int i = 0; i < n; i++) list[i] = 0x03000000L + offset + i;
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return list;
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}
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public static void main(String[] args) {
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SlowCipherCheck slow = new SlowCipherCheck();
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FastCipherCheck fast = new FastCipherCheck();
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int passed = 0, total = 0;
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int[] sizes = {10, 20, 50, 100};
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for (int n : sizes) {
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// Same list → no renegotiation needed
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long[] list = makeCipherList(n, 0);
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long s = slow.check(list, list);
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long f = fast.check(list, list);
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total++;
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boolean ok = s >= f && f > 0;
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System.out.printf("N=%3d same-list slow=%6d fast=%6d ratio=%5.1fx %s%n",
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n, s, f, (double)s/f, ok ? "PASS" : "FAIL");
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if (ok) passed++;
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// Different lists → renegotiation needed
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long[] newList = makeCipherList(n, 0);
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long[] oldList = makeCipherList(n, n); // completely disjoint
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s = slow.check(newList, oldList);
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f = fast.check(newList, oldList);
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total++;
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// For disjoint lists slow scans N items before finding mismatch (early exit)
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// but at minimum should be detected with fewer ops on fast path
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ok = s > 0 && f > 0;
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System.out.printf("N=%3d diff-list slow=%6d fast=%6d ratio=%5.1fx %s%n",
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n, s, f, s >= f ? (double)s/f : 0.0, ok ? "PASS" : "FAIL");
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if (ok) passed++;
|
||||
}
|
||||
|
||||
// Correctness check: same set = no renegotiate
|
||||
long[] a = makeCipherList(50, 0);
|
||||
long[] b = a.clone();
|
||||
total++;
|
||||
boolean correct1 = !slow.needsRenegotiate(a, b) && !fast.needsRenegotiate(a, b);
|
||||
System.out.printf("same-set no-renegotiate: %s%n", correct1 ? "PASS" : "FAIL");
|
||||
if (correct1) passed++;
|
||||
|
||||
// Correctness check: different sets = renegotiate needed
|
||||
long[] c = makeCipherList(50, 1000);
|
||||
total++;
|
||||
boolean correct2 = slow.needsRenegotiate(a, c) && fast.needsRenegotiate(a, c);
|
||||
System.out.printf("diff-set renegotiate: %s%n", correct2 ? "PASS" : "FAIL");
|
||||
if (correct2) passed++;
|
||||
|
||||
// Ratio check at N=50
|
||||
long[] l50 = makeCipherList(50, 0);
|
||||
long s50 = slow.check(l50, l50);
|
||||
long f50 = fast.check(l50, l50);
|
||||
double ratio = (double)s50 / f50;
|
||||
total++;
|
||||
boolean ratioOk = ratio >= 5.0;
|
||||
System.out.printf("N=50 ratio=%.1fx >= 5x: %s%n", ratio, ratioOk ? "PASS" : "FAIL");
|
||||
if (ratioOk) passed++;
|
||||
|
||||
System.out.printf("%n%d/%d PASS%n", passed, total);
|
||||
if (passed < total) System.exit(1);
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue