--- /dev/null
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+/* The use of the scoreboard in this module is based on a similar
+ * but simpler module, mod_antiloris by Kees Monshouwer, from
+ * ftp://ftp.monshouwer.eu/pub/linux/mod_antiloris/
+ * Note the FIXME that affects both modules.
+ *
+ * The major difference is that mod_antiloris checks the scoreboard
+ * on every request. This implies a per-request overhead that grows
+ * with the scoreboard, and gets very expensive on a big server.
+ * On the other hand, this module (mod_noloris) may be slower to
+ * react to a DoS attack, and in the case of a very small server
+ * it might be too late.
+ *
+ * Author's untested instinct: mod_antiloris will suit servers with
+ * Prefork MPM and low traffic. A server with a threaded MPM
+ * (or possibly a big prefork server with lots of memory) should
+ * raise MaxClients and use mod_noloris.
+ */
+
+#include "httpd.h"
+#include "http_config.h"
+#include "http_connection.h"
+#include "http_log.h"
+#include "mpm_common.h"
+#include "ap_mpm.h"
+#include "apr_hash.h"
+
+module AP_MODULE_DECLARE_DATA noloris_module;
+module AP_MODULE_DECLARE_DATA core_module;
+
+static unsigned int default_max_connections;
+static apr_hash_t *trusted;
+static apr_interval_time_t recheck_time;
+static apr_shm_t *shm;
+static apr_size_t shm_size;
+static int server_limit;
+static int thread_limit;
+
+static int noloris_conn(conn_rec *conn)
+{
+ /*** FIXME
+ * This is evil: we're assuming info that's private to the scoreboard
+ * We need to do that because there's no API to update the scoreboard
+ * on a connection, only with a request (or NULL to say not processing
+ * any request). We need a version of ap_update_child_status that
+ * accepts a conn_rec.
+ */
+ struct { int child_num; int thread_num; } *sbh = conn->sbh;
+
+ char *shm_rec;
+ worker_score *ws;
+ if (shm == NULL) {
+ return DECLINED; /* we're disabled */
+ }
+
+ /* check the IP is not banned */
+ shm_rec = apr_shm_baseaddr_get(shm);
+ if (strstr(shm_rec, conn->remote_ip)) {
+ apr_socket_t *csd = ap_get_module_config(conn->conn_config, &core_module);
+ ap_log_cerror(APLOG_MARK, APLOG_ERR, 0, conn,
+ "Dropping connection from banned IP %s", conn->remote_ip);
+ //ap_flush_conn(conn); /* just close it */
+ apr_socket_close(csd);
+
+ return DONE;
+ }
+
+ /* store this client IP for the monitor to pick up */
+ /* under traditional scoreboard, none of this happens until
+ * there's a request_rec. This is where we use the illegally-
+ * obtained private info from the scoreboard.
+ */
+
+ ws = &ap_scoreboard_image->servers[sbh->child_num][sbh->thread_num];
+ strcpy(ws->client, conn->remote_ip);
+
+ return DECLINED;
+}
+static int noloris_monitor(apr_pool_t *pool)
+{
+ static apr_hash_t *connections = NULL;
+ static apr_time_t last_check = 0;
+ static int *totals;
+
+ int i, j;
+ int *n;
+ int index = 0;
+ apr_hash_index_t *hi;
+ char *ip;
+ apr_time_t time_now;
+ char *shm_rec;
+ worker_score *ws;
+
+ /* do nothing if disabled */
+ if (shm == NULL) {
+ return 0;
+ }
+
+ /* skip check if it's not due yet */
+ time_now = apr_time_now();
+ if (time_now - last_check < recheck_time) {
+ return 0;
+ }
+ last_check = time_now;
+
+ /* alloc lots of stuff at start, so we don't leak memory per-call */
+ if (connections == NULL) {
+ connections = apr_hash_make(pool);
+ totals = apr_palloc(pool, server_limit*thread_limit);
+ ip = apr_palloc(pool, 18);
+ }
+
+ /* Get a per-client count of connections in READ state */
+ for (i = 0; i < server_limit; ++i) {
+ for (j = 0; j < thread_limit; ++j) {
+ ws = ap_get_scoreboard_worker(i, j);
+ if (ws->status == SERVER_BUSY_READ) {
+ n = apr_hash_get(connections, ws->client, APR_HASH_KEY_STRING);
+ if (n == NULL) {
+ n = totals + index++ ;
+ *n = 0;
+ }
+ ++*n;
+ apr_hash_set(connections, ws->client, APR_HASH_KEY_STRING, n);
+ }
+ }
+ }
+
+ /* reset shm before writing to it.
+ * We're only dealing with approx. counts, so we ignore the race condition
+ * with our prospective readers
+ */
+ shm_rec = apr_shm_baseaddr_get(shm);
+ memset(shm_rec, NULL, shm_size);
+
+ /* Now check the hash for clients with too many connections in READ state */
+ for (hi = apr_hash_first(NULL, connections); hi; hi = apr_hash_next(hi)) {
+ apr_hash_this(hi, (const void**) &ip, NULL, (void**)&n);
+ if (*n >= default_max_connections) {
+ /* if this isn't a trusted proxy, we mark it as bad */
+ if (!apr_hash_get(trusted, ip, APR_HASH_KEY_STRING)) {
+ ap_log_error(APLOG_MARK, APLOG_WARNING, 0, 0,
+ "noloris: banning %s with %d connections in READ state",
+ ip, *n);
+ strcpy(shm_rec++, " "); /* space == separator */
+ strcpy(shm_rec, ip);
+ shm_rec += strlen(ip);
+ }
+ }
+ }
+ apr_hash_clear(connections);
+ return 0;
+}
+static int noloris_post(apr_pool_t *pconf, apr_pool_t *ptmp, apr_pool_t *plog,
+ server_rec *s)
+{
+ apr_status_t rv;
+ int max_bans = thread_limit * server_limit / default_max_connections;
+ shm_size = 18 * max_bans;
+
+ rv = apr_shm_create(&shm, shm_size, NULL, pconf);
+ if (rv != APR_SUCCESS) {
+ ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s,
+ "Failed to create shm segment; mod_noloris disabled");
+ apr_hash_clear(trusted);
+ shm = NULL;
+ }
+ return 0;
+}
+static int noloris_pre(apr_pool_t *pconf, apr_pool_t *ptmp, apr_pool_t *plog)
+{
+ ap_mpm_query(AP_MPMQ_HARD_LIMIT_THREADS, &thread_limit);
+ ap_mpm_query(AP_MPMQ_HARD_LIMIT_DAEMONS, &server_limit);
+
+ /* set up default config stuff here */
+ trusted = apr_hash_make(pconf);
+ default_max_connections = 50;
+ recheck_time = apr_time_from_sec(10);
+ return 0;
+}
+static void noloris_hooks(apr_pool_t *p)
+{
+ ap_hook_process_connection(noloris_conn, NULL, NULL, APR_HOOK_FIRST);
+ ap_hook_pre_config(noloris_pre, NULL, NULL, APR_HOOK_MIDDLE);
+ ap_hook_post_config(noloris_post, NULL, NULL, APR_HOOK_MIDDLE);
+ ap_hook_monitor(noloris_monitor, NULL, NULL, APR_HOOK_MIDDLE);
+}
+static const char *noloris_trusted(cmd_parms *cmd, void *cfg, const char *val)
+{
+ const char* err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+ if (!err) {
+ apr_hash_set(trusted, val, APR_HASH_KEY_STRING, &noloris_module);
+ }
+ return err;
+}
+static const char *noloris_recheck(cmd_parms *cmd, void *cfg, const char *val)
+{
+ const char* err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+ if (!err) {
+ recheck_time = apr_time_from_sec(atoi(val));
+ }
+ return err;
+}
+static const char *noloris_max_conn(cmd_parms *cmd, void *cfg, const char *val)
+{
+ const char* err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+ if (!err) {
+ default_max_connections = atoi(val);
+ }
+ return err;
+}
+static const command_rec noloris_cmds[] = {
+ AP_INIT_ITERATE("TrustedProxy", noloris_trusted, NULL, RSRC_CONF,
+ "IP addresses from which to allow unlimited connections"),
+ AP_INIT_TAKE1("ClientRecheckTime", noloris_recheck, NULL, RSRC_CONF,
+ "Time interval for rechecking client connection tables"),
+ AP_INIT_TAKE1("MaxClientConnections", noloris_max_conn, NULL, RSRC_CONF,
+ "Max connections in READ state to permit from an untrusted client"),
+ {NULL}
+};
+module AP_MODULE_DECLARE_DATA noloris_module = {
+ STANDARD20_MODULE_STUFF,
+ NULL,
+ NULL,
+ NULL,
+ NULL,
+ noloris_cmds,
+ noloris_hooks
+};
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