sesman: accept full path for DefaultWindowManager

Solves: #1143

Also, this idea is inspired by Fedora's patch [1]. Some distro wants to
put all scripts in libexec directory due to SELinux. This enables
distros to put such scripts anywhere.

[1] https://src.fedoraproject.org/cgit/rpms/xrdp.git/tree/xrdp-0.9.6-scripts-libexec.patch?id=02f845c1b8cea781313cf3e9efcd6d7d50341824

sesman/config.c

@@ -115,7 +115,7 @@ config_read_globals(int file, struct config_sesman *cf, struct list *param_n,
     cf->listen_port[0] = '\0';
     cf->enable_user_wm = 0;
     cf->user_wm[0] = '\0';
-    cf->default_wm[0] = '\0';
+    cf->default_wm = 0;
     cf->auth_file_path = 0;
 
     file_read_section(file, SESMAN_CFG_GLOBALS, param_n, param_v);
@@ -126,7 +126,7 @@ config_read_globals(int file, struct config_sesman *cf, struct list *param_n,
 
         if (0 == g_strcasecmp(buf, SESMAN_CFG_DEFWM))
         {
-            g_strncpy(cf->default_wm, (char *)list_get_item(param_v, i), 31);
+            cf->default_wm = g_strdup((char *)list_get_item(param_v, i));
         }
         else if (0 == g_strcasecmp(buf, SESMAN_CFG_USERWM))
         {
@@ -166,9 +166,24 @@ config_read_globals(int file, struct config_sesman *cf, struct list *param_n,
         cf->enable_user_wm = 0;
     }
 
-    if ('\0' == cf->default_wm[0])
+    if (cf->default_wm == 0)
     {
-        g_strncpy(cf->default_wm, "startwm.sh", 11);
+        cf->default_wm = g_strdup("startwm.sh");
+    }
+    else if (g_strlen(cf->default_wm) == 0)
+    {
+        g_free(cf->default_wm);
+        cf->default_wm = g_strdup("startwm.sh");
+    }
+
+    /* if default_wm doesn't begin with '/', it's a relative path from XRDP_CFG_PATH */
+    if (cf->default_wm[0] != '/')
+    {
+        buf = (char *)g_malloc(1024, 0);
+        g_sprintf(buf, "%s/%s", XRDP_CFG_PATH, g_cfg->default_wm);
+        g_free(g_cfg->default_wm);
+        g_cfg->default_wm = g_strdup(buf);
+        g_free(buf);
     }
 
     return 0;
@@ -530,6 +545,7 @@ config_dump(struct config_sesman *config)
 void
 config_free(struct config_sesman *cs)
 {
+    g_free(cs->default_wm);
     g_free(cs->auth_file_path);
     list_delete(cs->rdp_params);
     list_delete(cs->vnc_params);

sesman/config.h

@@ -198,7 +198,7 @@ struct config_sesman
    * @var default_wm
    * @brief Default window manager
    */
-  char default_wm[32];
+  char *default_wm;
   /**
    * @var user_wm
    * @brief Default window manager

sesman/session.c

@@ -575,8 +575,7 @@ session_start_fork(tbus data, tui8 type, struct SCP_CONNECTION *c,
                 }
                 /* if we're here something happened to g_execlp3
                    so we try running the default window manager */
-                g_sprintf(text, "%s/%s", XRDP_CFG_PATH, g_cfg->default_wm);
-                g_execlp3(text, g_cfg->default_wm, 0);
+                g_execlp3(g_cfg->default_wm, g_cfg->default_wm, 0);
 
                 log_message(LOG_LEVEL_ALWAYS, "error starting default "
                              "wm for user %s - pid %d", s->username, g_getpid());