Added basic checks to ensure configured directories in lms.conf exist, fixes #828

INSTALL.md

@@ -45,7 +45,7 @@ __Optional dependencies__:
 
 __Notes__:
 * `libstb-dev` can be replaced by `libgraphicsmagick++1-dev` (the latter will likely use more RAM)
-You also need _Wt4_, which is not packaged on _Debian_. See [installation instructions](https://www.webtoolkit.eu/wt/doc/reference/html/InstallationUnix.html).</br>
+You also need _Wt4_, which is not packaged on _Debian_. See [installation instructions](https://www.webtoolkit.eu/wt/doc/reference/html/InstallationUnix.html).
 ### Build
 Get the latest stable release and build it:
 ```sh
@@ -99,9 +99,9 @@ systemctl restart lms
 # Deployment
 __Note__: don't forget to give the _lms_ user read access to the music directory you want to scan.
 ## Configuration
-_LMS_ uses a configuration file, installed by default in `/etc/lms.conf`. It is recommended to edit this file and change relevant settings (listen address, listen port, working directory, Subsonic API activation, deployment path, ...).
+_LMS_ uses a configuration file installed by default at `/etc/lms.conf`. It is recommended to edit this file and adjust the relevant settings like the working directory, Wt resources path, listen address, listen port, etc.
-All other settings are set using the web interface (user management, scan settings, transcode settings, ...).
+All other settings are configured through the web interface (user management, scan settings, transcode settings, etc.).
-If a setting is not present in the configuration file, a hardcoded default value is used (the same as in the [default configuration file](conf/lms.conf))
+If a setting is not present in the configuration file, a hardcoded default value is used (the same as in the [default configuration file](conf/lms.conf)).
 ## Authentication backends
 You can define which authentication backend to be used thanks to the `authentication-backend` option:
 * `internal` (default): _LMS_ uses an internal database to store users and their associated passwords (salted and hashed using [Bcrypt](https://en.wikipedia.org/wiki/Bcrypt)). Only the admin user can create, edit or remove other users.

src/lms/main.cpp

@@ -17,6 +17,7 @@
  * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <filesystem>
 #include <thread>
 
 #include <Wt/WApplication.h>
@@ -110,19 +111,58 @@ namespace lms
             throw core::LmsException{ "Invalid config value for 'jukebox-audio-backend'" };
         }
 
-        std::vector<std::string> generateWtConfig(std::string execPath)
+        std::error_code checkDirectoryAccessible(const std::filesystem::path& dir)
+        {
+            std::error_code ec;
+
+            const std::filesystem::file_status status{ std::filesystem::status(dir, ec) };
+            if (ec)
+                return ec;
+
+            if (status.type() != std::filesystem::file_type::directory)
+                return std::make_error_code(std::errc::not_a_directory);
+
+            const std::filesystem::directory_iterator it{ dir, ec };
+            if (ec)
+                return ec;
+
+            if (it != std::filesystem::directory_iterator{})
+            {
+                it->status(ec);
+                if (ec)
+                    return ec;
+            }
+
+            return {};
+        }
+
+        std::vector<std::string> generateWtConfig(const std::string& execPath)
         {
             core::IConfig& config{ *core::Service<core::IConfig>::get() };
 
             std::vector<std::string> args;
 
-            const std::filesystem::path wtConfigPath{ config.getPath("working-dir", "/var/lms") / "wt_config.xml" };
+            const std::filesystem::path workingDirectoryPath{ config.getPath("working-dir", "/var/lms") };
+            const std::filesystem::path wtConfigPath{ workingDirectoryPath / "wt_config.xml" };
             const std::filesystem::path wtResourcesPath{ config.getPath("wt-resources", "/usr/share/Wt/resources") };
+            const std::filesystem::path appRootPath{ config.getString("approot", "/usr/share/lms/approot") };
+
+            auto checkDirectoryExists{ [](const std::filesystem::path& directory, std::string_view settingName) {
+                std::string error;
+
+                const std::error_code ec{ checkDirectoryAccessible(directory) };
+                if (ec)
+                    throw core::LmsException{ "Cannot access directory '" + directory.string() + "' specified in setting '" + std::string{ settingName } + "': " + ec.message() };
+            } };
+
+            checkDirectoryExists(workingDirectoryPath, "working-dir");
+            checkDirectoryExists(wtResourcesPath, "wt-resources");
+            checkDirectoryExists(appRootPath, "approot");
 
             args.push_back(execPath);
             args.push_back("--config=" + wtConfigPath.string());
             args.push_back("--docroot=" + std::string{ config.getString("docroot", "/usr/share/lms/docroot/;/resources,/css,/images,/js,/favicon.ico") });
-            args.push_back("--approot=" + std::string{ config.getString("approot", "/usr/share/lms/approot") });
+            args.push_back("--approot=" + appRootPath.string());
             args.push_back("--deploy-path=" + std::string{ config.getString("deploy-path", "/") });
             if (!wtResourcesPath.empty())
                 args.push_back("--resources-dir=" + wtResourcesPath.string());