fix(d5-daemon-core): cppcheck const-correctness, wire module length cap, daemonize chdir/umask, daemon confinement tests

- daemon_conf.c/server.c/test_daemon_conf.c: const-qualify parse/loop pointers;
  scope user_path static inside its block (clears the 9-wave-A cppcheck findings)
- config.c receive_daemon_module: reject invalid/over-long wire module names
  (> DAEMON_MAX_MODULE_NAME) with a clean STATUS_ERROR; client side already
  enforced via daemon_module_name_valid in config_parse_daemon_dest
- server.c daemonize: chdir(/) and umask(0) so module paths resolve from /
  and config-requested file modes are honored; PROTOCOL_VERSION stays 2.15.0
- test_daemon.py: confinement (read-only/unknown no-write anywhere), module-less
  and dot-dot destination refusal, real daemon_detach double-fork path

src/server/server.c

@@ -19,6 +19,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <errno.h>
+#include <sys/stat.h>
 #include <openssl/x509.h>
 
 static char* authorized_root;
@@ -459,9 +461,9 @@ static void print_server_usage(void) {
  * exists (or when HOME is set), otherwise /etc/fastsyncd.conf.  Returns a
  * pointer to a static buffer (never NULL). */
 static const char* default_daemon_config_path(void) {
-  static char user_path[PATH_MAX];
   const char* home = getenv("HOME");
   if (home && *home) {
+    static char user_path[PATH_MAX];
     int n = snprintf(user_path, sizeof(user_path), "%s/.config/fastsync/fastsyncd.conf", home);
     if (n > 0 && (size_t)n < sizeof(user_path) && access(user_path, R_OK) == 0)
       return user_path;
@@ -496,6 +498,12 @@ static bool daemonize(void) {
     if (devnull > STDERR_FILENO)
       close(devnull);
   }
+  /* Do not pin the launch CWD (module-relative 'path' entries would resolve
+   * against an unstable working directory) and drop the restrictive host umask
+   * so modules can create files/dirs with the modes the config requests. */
+  if (chdir("/") != 0)
+    log_message(LOG_LEVEL_WARNING, "daemon: chdir to / failed: %s", strerror(errno));
+  umask(0);
   return true;
 }
 

src/shared/config.c

@@ -1070,6 +1070,16 @@ static bool receive_daemon_module(int fd, Config* c) {
   char* module = receive_str(fd);
   if (!module)
     return false;
+  /* Guard against a hostile client flooding the log with an over-long module
+   * name: only an empty string (module-less) or a valid module name
+   * (bounded by DAEMON_MAX_MODULE_NAME) is accepted.  This is an input
+   * guard, not a wire-format change. */
+  if (*module != '\0' && !daemon_module_name_valid(module)) {
+    log_message(LOG_LEVEL_WARNING, "Daemon client sent an invalid or over-long module name");
+    free(module);
+    send_status(fd, STATUS_ERROR);
+    return false;
+  }
   if (*module != '\0') {
     c->module = module;
   } else {

src/shared/daemon_conf.c

@@ -122,7 +122,8 @@ static bool store_port(int* slot, const char* value, char* err, size_t err_size)
 
 /* Apply a global scalar key/value.  Keys are case-insensitive.  Returns false
  * (err filled) on an unknown key or an invalid value. */
-static bool apply_global_key(DaemonConf* conf, char* key, char* value, char* err, size_t err_size) {
+static bool apply_global_key(DaemonConf* conf, char* key, const char* value, char* err,
+                             size_t err_size) {
   if (key_equals(key, "port"))
     return store_port(&conf->global.port, value, err, err_size);
   if (key_equals(key, "motd file")) {
@@ -177,7 +178,7 @@ static bool apply_module_key(DaemonModule* module, char* key, char* value, char*
     }
     char* save = NULL;
     for (char* token = strtok_r(list, ",", &save); token; token = strtok_r(NULL, ",", &save)) {
-      char* user = trim_ws(token);
+      const char* user = trim_ws(token);
       if (*user == '\0')
         continue;
       char** grown =
@@ -341,7 +342,7 @@ DaemonConf* daemon_conf_load(const char* path, char* err, size_t err_size) {
       }
       *close = '\0';
       char* trailing = close + 1;
-      char* rest = trim_ws(trailing);
+      const char* rest = trim_ws(trailing);
       if (*rest != '\0') {
         set_error(err, err_size, "line %d: unexpected text after module header", line_no);
         ok = false;
@@ -425,7 +426,7 @@ int daemon_conf_apply_dparam(DaemonConf* conf, const char* assignment, char* err
   }
   *eq = '\0';
   char* key = trim_ws(copy);
-  char* value = trim_ws(eq + 1);
+  const char* value = trim_ws(eq + 1);
   if (*key == '\0') {
     free(copy);
     set_error(err, err_size, "--dparam '%s' has an empty key", assignment);