Phoenix.Functionality.Settings.Encryption 3.2.0

Phoenix.Functionality.Settings

Contains assemblies that provide a common way for accessing application settings.

Table of content

[toc]

General principle

Settings should be represented as a simple poco class within an application, so that the program can access its defined properties. In the background, those settings are stored in some kind of hopefully persistent storage. This storage could be text files of different formats like the commonly used json files or a database. This settings library provides tools that handle the synchronization of stored settings with settings classes of an application.

Terminology

SettingsManager

The main implementation of an ISettingsManager is the generic SettingsManager<TSettingsData>. It is the starting point for ISettings handling with this library. Its generic argument TSettingsData defines the type of the data that is used to store the settings outside of the applications life cycle. After it has been created, it is the only class required to handle settings.

The SettingsManager<TSettingsData> internally utilizes a generic sink of type ISettingsSink<TSettingsData> and a generic serializer of type ISettingsSerializer<TSettingsData>. The generic argument is the same for each instance of the manager. For a simple (and probably common example) lets assume that this generic argument would be of type String. This means that the sink has the responsibility to retrieve or store the settings as a simple string, whereas the serializer has the responsibility to (de)serialize settings to or from a string. Where the string is stored or how the string is (de)serialized is up to the specific implementation that was used to build the manager.

Process flow

Loading

The SettingsManager requests the SettingsSink to load settings data from its storage system. It then passes that data to the SettingsSerializer so it is converted into an ISettings class.

Saving

The SettingsManager instructs the SettingsSerializer to convert an ISettings class into settings data. This data is then passed to the SettingsSink for storing it to its storage system.

Creation

The easiest way to build an SettingsManager<TSettingsData> is using the fluent syntax (also called builder pattern).

Here is the most basic example showing how to create a new manager. Obviously the respective sink, serializer and cache have to be created beforehand.

var settingsManager = SettingsManager<string>
	.Create()
	.AddSink(someSink)
	.AddSerializer(someSerializer)
	.AddCache(someCache)
	.Build()
	;

Since sinks, serializers and caches can provide their own fluent syntax, a more complete example could look like this:

using Phoenix.Functionality.Settings;
using Phoenix.Functionality.Settings.Cache;
using Phoenix.Functionality.Settings.Encryption;
using Phoenix.Functionality.Settings.Serializers.Json.Net;
using Phoenix.Functionality.Settings.Serializers.Json.Net.CustomConverters;
using Phoenix.Functionality.Settings.Sinks.File;

var fileExtension = ".json";
var baseDirectory = new DirectoryInfo(Path.Combine(Directory.GetCurrentDirectory(), ".settings"));
var settingsManager = SettingsManager<string>
	.Create()
	.UsingFileSink(fileExtension, baseDirectory)
	.UsingJsonSerializer()
		.WithFileInfoConverter(baseDirectory)
		.WithDirectoryInfoConverter(baseDirectory)
		.WithIpAddressConverter()
		.WithRegexConverter()
		.WithTimeSpanConverter()
		.WithVersionConverter()
		.WithEnumConverter(WriteOutValues.AsSuffix(start: "[", separator: ";", end: "]"))
		.WithDefaultSerializerOptions()
	.UsingWeakCache()
	.UsingEncryption()
	.Build()
	;

Settings

Settings are represented as classes implementing the empty ISettings interface. The purpose of that interface is a more straightforward way to identify settings throughout an application. It is also used for extension methods, that otherwise would have to extend the Object base class, which would be less ideal.

Events

To react on events that may occur while loading settings, separate interfaces forcing implementation of special callbacks are available. They must be added to the settings class additionally to the ISettings interface. Invoking those callbacks is the responsibility of the ISettingsManager. The default SettingsManager will do so.

Currently the following are available:

Attributes

For modifying certain behavior to or add more information to settings, the following attributes are available:

Saving settings

To make saving or reloading ISettings instances as easy as possible, some convenient extension methods are available. In order for those methods to properly function, it has to be known which ISettingsManager is responsible for handling the settings instance. To provide this manager, a method that is hidden from IntelliSense named SettingsExtensions.InitializeExtensionMethods must be invoked after the instance was created. When using the SettingsManager<TSettingsData>, it will automatically be called for each loaded settings instance.

• ISettings.Save

  This saves the current settings instance to the data store.

  var settings = settingsManager.Load<Settings>();
  settings.InitializeExtensionMethods(settingsManager); // Not neded if using SettingsManager<TSettingsData>
  settings.MyProperty = "Change";
  settings.Save();
  

• ISettings.Reload

  This reloads and returns the settings. Note that the original settings passed to the extension method will stay unchanged.

    var settings = settingsManager.Load<Settings>();
    settings.InitializeExtensionMethods(settingsManager); // Not neded if using SettingsManager<TSettingsData>
    var newSettings = settings.Reload();
  

Implementations of ISettingsSink

Specific implementations of ISettingsSinks are provided as separate NuGet packages. Currently the following are available.

Sinks.File

This sink uses the normal file system to store Isettings as file. The file name is created from the settings class and suffixed with a configurable extension. The name of the file itself can be changed by attributing the settings class with the SettingsFileNameAttribute (see Attributes).

Creation via fluent syntax is supported.

var settingsManager = SettingsManager<string>
	.Create()
	// -->
	.UsingFileSink(fileExtension, baseDirectory)
	// <--
	.AddSerializer(...)
	.AddCache(...)
	.Build()
	;

Implementations of ISettingsSerializer

Specific implementations of ISettingsSerializers are provided as separate NuGet packages. Currently the following are available.

Serializers.Json.Net

This serializer converts to and from the common JSON format. Serialization and deserialization is leveraged to System.Text.Json.

Creation via fluent syntax is supported.

var settingsManager = SettingsManager<string>
	.Create()
	.AddSink(...)
	// -->
	.UsingJsonSerializer()
		.WithFileInfoConverter()
		.WithDirectoryInfoConverter()
		.WithIpAddressConverter()
		.WithRegexConverter()
		.WithTimeSpanConverter()
		.WithVersionConverter()
		.WithEnumConverter(WriteOutValues.AsSuffix(start: "[", separator: ";", end: "]"))
		.WithDefaultSerializerOptions()
	// <--
	.AddCache(...)
	.Build()
	;

Custom Converters

The package provides special converters that allow for some common types to be used directly within settings classes.

File- and DirectoryInfoConverter

Those converters support relative path if a base directory has been specified when creating the converters. If settings are loaded and saved, the converter checks if the path of any FileInfo or DirectoryInfo property could be expressed as a path relative to the specified base directory.

[!NOTE] Relative path are only supported with up to three parent folders (e.g ../../.../MyFolder/Some.file). Other files will be saved as absolute path.

IpAddressConverter

RegexConverter

TimeSpanConverter

The string representation of a TimeSpan is in milliseconds.

VersionConverter

EnumConverter

Contrary to Microsofts JsonStringEnumConverter this converter can optionally be configured via different IWriteOutOptions, to add the values of an enumeration to the serialized settings data.

The following write-out options are available and applied to below example:

class MySettings : ISettings
{
	public MyEnum First { get; init; } = MyEnum.Default;
	public MyEnum Second { get; init; } = MyEnum.Default;
}

• Write-out as suffix to the property value

  Will add the enumeration values with configurable start, end and separator as a suffix to the value.

  var converter = new EnumConverter(WriteOutValues.AsSuffix(start: "[", separator: ";", end: "]"));
  var serializer = new JsonSettingsSerializer(converter);
  var settingsData = serializer.Serialize(settings);
  

  {
    "first": "Entry1 [Default;Entry1;Entry2]",
    "second": "Entry2 [Default;Entry1;Entry2]"
  }
  

Implementations of ISettingsCache

Each ISettingsManager should have an internal cache, so that loading the same settings class multiple times, will always return the same instance. The following simple cache classes are available. Each of them implements the ISettingsCacheinterface.

NoSettingsCache

This variant obviously does not cache anything. It is the default cache used by SettingsManager<TSettingsData> if not specified otherwise.

SettingsCache

This cache stores references to all loaded ISetting instances.

WeakSettingsCache

This cache stores all loaded ISettings instances as WeakReference. This allows those instances to be collected by the garbage collector.

Encryption

[!WARNING] Please note, that this is not a cryptographic centered assembly. Therefore you should probably not try and use it to save your Bitcoin mnemonic.

[!NOTE] Encryption is based on AesManaged. The key and vector used to create the symmetric encryptor can be specified with an overload of the ApplyEncryption extension method.

Some information stored in setting files (like database connection strings) may contain sensitive data and should therefore be encrypted. This can be achieved via the special EncryptSettingsManager . It is a decorator for any other ISettingsManager and handles de- or encryption of properties attributed with the EncryptAttribute.

[!NOTE] Currently only String or Object properties supported. Those can also be wrapped inside arrays or lists.

To use the EncryptSettingsManager simply call the extension method ApplyEncryption on any other ISettingsManager instance.

var settingsManager = new SettingsManager().ApplyEncryption();

It also provides support for the builder pattern of the SettingsManager<TSettingsData>.

var settingsManager = SettingsManager<string>
	.Create()
	.AddSink(...)
	.AddSerializer(...)
	.AddCache(...)
#if !DEBUG
	// -->
	.UsingEncryption()
	// <--
#endif
	.Build()
	;

When loading settings, the EncryptSettingsManager traverses all properties of the corresponding settings instance searching for the EncryptAttribute to decrypt their values, so accessing them from code will always return meaningful data. The EncryptSettingsManager handles nested properties as well as certain collection types and recursively traverses them as well.

[!IMPORTANT] To only recursively traverse user-created types the EncryptSettingsManager must distingusih those types from the .NET build-in types. To make this possible (especially within apps that are published as single-file executable) the manager will not traverse into types that come from assemblies whose name starts with System.

• The EncryptForceFollowAttribute can be used in cases where this may be undesirable, to force the EncryptSettingsManager to traverse the attributed property nevertheless.
• The EncryptDoNotFollowAttribute on the other side will instruct the manager to not traverse the attributed property.

[!WARNING] Encryption is automatically applied when a settings instance is loaded. This means, that loading encrypts the value in the source of the settings. It is therefore recommended to only use encryption in release builds via a preprocessor directives.

Authors

• Felix Leistner: v1.x - v3.x