src/shared/daemon_conf.c

@@ -190,6 +190,26 @@ static bool store_max_connections(int* slot, const char* value, const char* modu
   return true;
 }
 
+/* Parse a non-negative concurrency cap where 0 means unlimited/disabled
+ * (per-module `max connections`, `max connections per host`,
+ * `auth lockout threshold`).  Negative/garbage/oversized values are rejected. */
+static bool store_optional_cap(int* slot, const char* value, int max_value, const char* key,
+                               const char* module_name, char* err, size_t err_size) {
+  char* end = NULL;
+  errno = 0;
+  long n = strtol(value, &end, 10);
+  if (*value == '\0' || errno != 0 || *end != '\0' || n < 0 || n > max_value) {
+    if (module_name)
+      set_error(err, err_size, "module '%s': invalid '%s' '%s' (must be 0-%d)", module_name, key,
+                value, max_value);
+    else
+      set_error(err, err_size, "invalid '%s' '%s' (must be 0-%d)", key, value, max_value);
+    return false;
+  }
+  *slot = (int)n;
+  return true;
+}
+
 /* Parse an `auth failure delay` value: 0 (disabled) through the configured cap. */
 static bool store_auth_failure_delay(int* slot, const char* value, char* err, size_t err_size) {
   char* end = NULL;
@@ -227,6 +247,9 @@ DaemonConf* daemon_conf_create(void) {
   conf->global.port = DAEMON_CONF_DEFAULT_PORT;
   conf->global.max_connections = DAEMON_CONF_DEFAULT_MAX_CONNECTIONS;
   conf->global.auth_failure_delay_ms = DAEMON_CONF_DEFAULT_AUTH_FAILURE_DELAY_MS;
+  conf->global.max_connections_per_host = DAEMON_CONF_DEFAULT_MAX_CONNECTIONS_PER_HOST;
+  conf->global.auth_lockout_threshold = DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_THRESHOLD;
+  conf->global.auth_lockout_duration_sec = DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_DURATION_SEC;
   return conf;
 }
 
@@ -312,8 +335,20 @@ static bool apply_global_key(DaemonConf* conf, char* key, const char* value, boo
   }
   if (key_equals(key, "max connections"))
     return store_max_connections(&conf->global.max_connections, value, NULL, err, err_size);
+  if (key_equals(key, "max connections per host"))
+    return store_optional_cap(&conf->global.max_connections_per_host, value,
+                              DAEMON_CONF_MAX_CONCURRENCY_LIMIT, "max connections per host", NULL,
+                              err, err_size);
   if (key_equals(key, "auth failure delay"))
     return store_auth_failure_delay(&conf->global.auth_failure_delay_ms, value, err, err_size);
+  if (key_equals(key, "auth lockout threshold"))
+    return store_optional_cap(&conf->global.auth_lockout_threshold, value,
+                              DAEMON_CONF_MAX_CONCURRENCY_LIMIT, "auth lockout threshold", NULL,
+                              err, err_size);
+  if (key_equals(key, "auth lockout duration"))
+    return store_optional_cap(&conf->global.auth_lockout_duration_sec, value,
+                              DAEMON_CONF_MAX_AUTH_LOCKOUT_DURATION_SEC, "auth lockout duration",
+                              NULL, err, err_size);
   if (key_equals(key, "hosts allow"))
     return store_host_list(&conf->global.hosts_allow, &conf->global.hosts_allow_count, value,
                            "hosts allow", NULL, replace_hosts, err, err_size);
@@ -400,7 +435,8 @@ static bool apply_module_key(DaemonModule* module, char* key, char* value, char*
     return true;
   }
   if (key_equals(key, "max connections"))
-    return store_max_connections(&module->max_connections, value, module->name, err, err_size);
+    return store_optional_cap(&module->max_connections, value, DAEMON_CONF_MAX_CONCURRENCY_LIMIT,
+                              "max connections", module->name, err, err_size);
   if (key_equals(key, "hosts allow"))
     return store_host_list(&module->hosts_allow, &module->hosts_allow_count, value, "hosts allow",
                            false, module->name, err, err_size);
@@ -444,6 +480,11 @@ static int open_module(DaemonConf* conf, int* current_module, const char* name,
     set_error(err, err_size, "duplicate module '%s'", name);
     return -1;
   }
+  if (conf->module_count >= DAEMON_CONF_MAX_MODULES) {
+    set_error(err, err_size, "too many modules (limit %d); module '%s' rejected",
+              DAEMON_CONF_MAX_MODULES, name);
+    return -1;
+  }
   DaemonModule* grown =
       realloc(conf->modules, (size_t)(conf->module_count + 1) * sizeof(DaemonModule));
   if (!grown) {

src/shared/daemon_conf.h

@@ -52,11 +52,10 @@ typedef struct DaemonModule {
                         activities.  Without it the daemon refuses all of them. */
   char** auth_users; /* `auth users = a,b`; Wave B credential list */
   int auth_user_count;
-  /* `max connections = N` (optional per-module cap).  0 means "not set"
-   * (inherit the global cap).  Parsed, stored, and validated, but NOT enforced
-   * per-module: connections are counted in the accept-loop parent before the
-   * client's module is known, so only the global cap is enforced (see
-   * transport_tcp.c and the Daemon Mode notes in RSYNC_COMPAT.md). */
+  /* `max connections = N` (optional per-module cap).  0 means unlimited.  The
+   * per-connection child records the selected module in the shared registry
+   * (daemon_limits.c) once the config frame names it, so the cap is enforced
+   * across all forked children; the parent reclaims the slot on SIGCHLD. */
   int max_connections;
   char** hosts_allow; /* `hosts allow = a,b`; host access allow patterns */
   int hosts_allow_count;
@@ -74,6 +73,17 @@ typedef struct DaemonConfGlobals {
                                     DAEMON_CONF_DEFAULT_MAX_CONNECTIONS (100) */
   int auth_failure_delay_ms;     /* `auth failure delay`, milliseconds; default
                                     DAEMON_CONF_DEFAULT_AUTH_FAILURE_DELAY_MS */
+  int max_connections_per_host;  /* `max connections per host`, concurrent cap per
+                                    source IP; default
+                                    DAEMON_CONF_DEFAULT_MAX_CONNECTIONS_PER_HOST (0 =
+                                    unlimited) */
+  int auth_lockout_threshold;    /* `auth lockout threshold`, failed attempts from
+                                    one source before lockout; default
+                                    DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_THRESHOLD (0
+                                    disables) */
+  int auth_lockout_duration_sec; /* `auth lockout duration`, seconds; default
+                                    DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_DURATION_SEC
+                                    (0 disables) */
   char** hosts_allow;            /* `hosts allow`; global host access allow patterns */
   int hosts_allow_count;
   char** hosts_deny; /* `hosts deny`; global host access deny patterns */
@@ -92,11 +102,26 @@ typedef struct DaemonConf {
 #define DAEMON_CONF_DEFAULT_MAX_CONNECTIONS 100
 /* Default `auth failure delay` in milliseconds (0 disables the throttle). */
 #define DAEMON_CONF_DEFAULT_AUTH_FAILURE_DELAY_MS 500
+/* Default `max connections per host` (0 = unlimited). */
+#define DAEMON_CONF_DEFAULT_MAX_CONNECTIONS_PER_HOST 0
+/* Default cross-process auth lockout: 10 failed attempts from one source lock
+ * it out for 300 s (0 disables either knob). */
+#define DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_THRESHOLD 10
+#define DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_DURATION_SEC 300
+/* Upper bound on a `max connections per host` or `auth lockout threshold`
+ * value, so a typo cannot size the shared registry absurdly. */
+#define DAEMON_CONF_MAX_CONCURRENCY_LIMIT 1000000
+/* Upper bound on `auth lockout duration` (7 days). */
+#define DAEMON_CONF_MAX_AUTH_LOCKOUT_DURATION_SEC 604800
 /* Largest accepted `auth failure delay`, so a typo cannot pin a connection
  * child in nanosleep for an absurd time. */
 /* Bounded well below the socket I/O timeout so a failed-auth child cannot hold
  * a connection slot for long enough to amplify connection-cap exhaustion. */
 #define DAEMON_CONF_MAX_AUTH_FAILURE_DELAY_MS 5000
+/* Upper bound on the number of [module] sections, so the shared registry's
+ * per-module counter array stays fixed-size.  The parser rejects the next
+ * section past this bound. */
+#define DAEMON_CONF_MAX_MODULES 256
 /* Longest accepted config line (excluding the trailing newline).  Longer lines
  * are rejected rather than buffered unboundedly. */
 #define DAEMON_CONF_MAX_LINE 4096
@@ -129,8 +154,9 @@ bool daemon_module_name_valid(const char* name);
 /* Parse one --dparam=KEY=VALUE (or "--dparam KEY=VALUE") override string and
  * apply it to the global keys only.  Keys are case-insensitive and limited to
  * the global keys defined by the grammar (port, motd file, address,
- * max connections, auth failure delay, hosts allow, hosts deny).  Returns 0 on
- * success, -1 on error (err filled). */
+ * max connections, max connections per host, auth failure delay,
+ * auth lockout threshold, auth lockout duration, hosts allow, hosts deny).
+ * Returns 0 on success, -1 on error (err filled). */
 int daemon_conf_apply_dparam(DaemonConf* conf, const char* assignment, char* err, size_t err_size);
 
 /* Host access-control matching (pure; no I/O).  `daemon_host_pattern_match`

tests/test_daemon_conf.c

@@ -33,6 +33,11 @@ static void test_daemon_conf_create_defaults() {
   EXPECT_NULL(conf->global.address);
   EXPECT_EQ_INT(conf->global.max_connections, DAEMON_CONF_DEFAULT_MAX_CONNECTIONS);
   EXPECT_EQ_INT(conf->global.auth_failure_delay_ms, DAEMON_CONF_DEFAULT_AUTH_FAILURE_DELAY_MS);
+  EXPECT_EQ_INT(conf->global.max_connections_per_host,
+                DAEMON_CONF_DEFAULT_MAX_CONNECTIONS_PER_HOST);
+  EXPECT_EQ_INT(conf->global.auth_lockout_threshold, DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_THRESHOLD);
+  EXPECT_EQ_INT(conf->global.auth_lockout_duration_sec,
+                DAEMON_CONF_DEFAULT_AUTH_LOCKOUT_DURATION_SEC);
   EXPECT_EQ_INT(conf->global.hosts_allow_count, 0);
   EXPECT_EQ_INT(conf->global.hosts_deny_count, 0);
   EXPECT_EQ_INT(conf->module_count, 0);
@@ -316,6 +321,12 @@ static void test_daemon_conf_dparam_override() {
 
   EXPECT_EQ_INT(daemon_conf_apply_dparam(conf, "max connections=7", err, sizeof(err)), 0);
   EXPECT_EQ_INT(conf->global.max_connections, 7);
+  EXPECT_EQ_INT(daemon_conf_apply_dparam(conf, "max connections per host=3", err, sizeof(err)), 0);
+  EXPECT_EQ_INT(conf->global.max_connections_per_host, 3);
+  EXPECT_EQ_INT(daemon_conf_apply_dparam(conf, "auth lockout threshold=5", err, sizeof(err)), 0);
+  EXPECT_EQ_INT(conf->global.auth_lockout_threshold, 5);
+  EXPECT_EQ_INT(daemon_conf_apply_dparam(conf, "auth lockout duration=120", err, sizeof(err)), 0);
+  EXPECT_EQ_INT(conf->global.auth_lockout_duration_sec, 120);
   EXPECT_EQ_INT(daemon_conf_apply_dparam(conf, "AUTH FAILURE DELAY=1500", err, sizeof(err)), 0);
   EXPECT_EQ_INT(conf->global.auth_failure_delay_ms, 1500);
   EXPECT_EQ_INT(
@@ -390,6 +401,9 @@ static void test_daemon_conf_limits_and_hosts_parse() {
   char err[256];
   EXPECT_EQ_INT(write_conf("max connections = 25\n"
                            "auth failure delay = 0\n"
+                           "max connections per host = 4\n"
+                           "auth lockout threshold = 3\n"
+                           "auth lockout duration = 60\n"
                            "hosts allow = 10.0.0.0/8, 192.168.1.0/24\n"
                            "hosts deny = 192.168.0.1 2001:db8::/32\n"
                            "\n"
@@ -405,6 +419,9 @@ static void test_daemon_conf_limits_and_hosts_parse() {
   EXPECT_NOT_NULL(conf);
   EXPECT_EQ_INT(conf->global.max_connections, 25);
   EXPECT_EQ_INT(conf->global.auth_failure_delay_ms, 0);
+  EXPECT_EQ_INT(conf->global.max_connections_per_host, 4);
+  EXPECT_EQ_INT(conf->global.auth_lockout_threshold, 3);
+  EXPECT_EQ_INT(conf->global.auth_lockout_duration_sec, 60);
   EXPECT_EQ_INT(conf->global.hosts_allow_count, 2);
   EXPECT_EQ_STR(conf->global.hosts_allow[0], "10.0.0.0/8");
   EXPECT_EQ_STR(conf->global.hosts_allow[1], "192.168.1.0/24");
@@ -422,6 +439,9 @@ static void test_daemon_conf_limits_and_hosts_parse() {
       "max connections = 0\n",           "max connections = -1\n",
       "max connections = abc\n",         "auth failure delay = -1\n",
       "auth failure delay = 70000\n",    "auth failure delay = soon\n",
+      "max connections per host = -1\n", "max connections per host = lots\n",
+      "auth lockout threshold = -2\n",   "auth lockout threshold = many\n",
+      "auth lockout duration = -1\n",    "auth lockout duration = forever\n",
       "hosts allow = 10.0.0.0/99\n",     "hosts deny = 2001:db8::/129\n",
       "hosts allow = *.example.com\n",   "hosts deny = not-an-ip\n",
   };
@@ -434,7 +454,8 @@ static void test_daemon_conf_limits_and_hosts_parse() {
 
   /* The same strictness applies inside a module section. */
   const char* bad_module[] = {
-      "[m]\npath = /x\nmax connections = 0\n",
+      "[m]\npath = /x\nmax connections = -1\n",
+      "[m]\npath = /x\nmax connections = abc\n",
       "[m]\npath = /x\nhosts allow = 10.0.0.0/40\n",
       "[m]\npath = /x\nhosts deny = 999.1.1.1/8\n",
   };
@@ -446,6 +467,14 @@ static void test_daemon_conf_limits_and_hosts_parse() {
     EXPECT_TRUE(strstr(err, "invalid") != NULL);
   }
 
+  /* Module `max connections = 0` is now valid and means unlimited. */
+  EXPECT_EQ_INT(write_conf("[m]\npath = /x\nmax connections = 0\n", &path), 0);
+  conf = daemon_conf_load(path, err, sizeof(err));
+  free(path);
+  EXPECT_NOT_NULL(conf);
+  EXPECT_EQ_INT(conf->modules[0].max_connections, 0);
+  daemon_conf_free(conf);
+
   /* An empty hosts list is not an error (no patterns are added). */
   EXPECT_EQ_INT(write_conf("hosts allow = \n[m]\npath = /x\n", &path), 0);
   conf = daemon_conf_load(path, err, sizeof(err));
@@ -509,6 +538,27 @@ static void test_daemon_module_name_valid() {
   }
 }
 
+static void test_daemon_conf_module_count_capped() {
+  size_t cap = DAEMON_CONF_MAX_MODULES;
+  size_t len = (cap + 8) * 32;
+  char* body = malloc(len);
+  EXPECT_NOT_NULL(body);
+  body[0] = '\0';
+  for (size_t i = 0; i < cap + 1; i++) {
+    char line[48];
+    snprintf(line, sizeof(line), "[m%zu]\npath = /x\n", i);
+    strcat(body, line);
+  }
+  char* path;
+  EXPECT_EQ_INT(write_conf(body, &path), 0);
+  free(body);
+  char err[256];
+  const DaemonConf* conf = daemon_conf_load(path, err, sizeof(err));
+  free(path);
+  EXPECT_NULL(conf);
+  EXPECT_TRUE(strstr(err, "too many modules") != NULL);
+}
+
 void test_daemon_conf() {
   test_daemon_conf_create_defaults();
   test_daemon_conf_full_parse();
@@ -525,6 +575,7 @@ void test_daemon_conf() {
   test_daemon_conf_dparam_override();
   test_daemon_conf_auth_users_validated();
   test_daemon_conf_limits_and_hosts_parse();
+  test_daemon_conf_module_count_capped();
   test_daemon_hosts_allowed();
   test_daemon_module_name_valid();
 }