Plugin Development - KeePass
Author: Dominik Reichl
Description: KeePass is an open source password manager. Passwords can be stored in highly-encrypted databases, which can be unlocked with one master password or key file.
Keywords: KeePass, Password, Safe, Security, Database, Encryption, Secure, Manager, Open, Source, Free, Code, Key, Master, Disk, Dominik, Reichl

| # Plugin Development How to develop plugins for KeePass 2.x.

This documentation applies to KeePass 2.x plugins. 2.x plugins are fundamentally different from 1.x plugins. 1.x plugins cannot be loaded by KeePass 2.x.

- Requirements
- Step-by-Step Tutorial
- Common Operations
- Plugin Conventions
- Update Checking
- Can KeePass 2.x Plugins be written in Unmanaged C++?
- PLGX Files

## Requirements

Before you can start developing a KeePass plugin, you need the following prerequisites:

- Latest KeePass source code package. You can get it from the KeePass website.
- A C# 2.0 development IDE (Microsoft Visual Studio, SharpDevelop or any other IDE).

## Step-by-Step Tutorial

Start your favorite IDE and create a new C# Class Library project. In this tutorial the example plugin we're developing is called `SamplePlugin`. The first thing you need to do now is to add a reference to KeePass: go to the references dialog and select the `KeePass.exe` file. After you added the reference, the namespaces `KeePass` and `KeePassLib` should be available.

KeePass plugins all need to derive from a base KeePass plugin class (`Plugin` in the `KeePass.Plugins` namespace). By overriding methods of this class, you can customize the behaviour of your plugin.

A minimal plugin looks like this:

    using System;
    using System.Collections.Generic;

    using KeePass.Plugins;

    namespace SamplePlugin
    {
    	public sealed class SamplePluginExt : Plugin
    	{
    		private IPluginHost m_host = null;

    		public override bool Initialize(IPluginHost host)
    		{
    			m_host = host;
    			return true;
    		}
    	}
    }

You can find a fully documented and extended version of this simple plugin on the KeePass plugins web page.

This plugin does exactly nothing, but it shows some important conventions already, which must be followed by all plugins:

- The namespace must be named like the DLL file without extension. Our DLL file is named `SamplePlugin.dll`, therefore the namespace must be called `SamplePlugin`.
- The main plugin class (which KeePass will instantiate when it loads your plugin) must be called exactly the same as the namespace plus "Ext". In this case: "SamplePlugin" + "Ext" = "SamplePluginExt".
- The main plugin class must be derived from the `KeePass.Plugins.Plugin` base class.

The `Initialize` function is the most important one and you probably will always override it. In this function, you get an interface to the KeePass internals: an `IPluginHost` interface reference. By using this interface, you can access the KeePass main menu, the currently opened database, etc. The `Initialize` function is called immediately after KeePass loads your plugin. All initialization should be done in this function (not in the constructor of your plugin class!). If you successfully initialized everything, you must return `true`. If you return `false`, KeePass will immediately unload your plugin.

A second function that you will need very often is the `Terminate` function:

    public override void Terminate()
    {
    }

This function is called shortly before KeePass unloads your plugin. You cannot abort this process (it's just a notification and your last chance to clean up all used resources, etc.). Immediately after you return from this function, KeePass can unload your plugin. It is highly recommended to free all resources in this function (not in the destructor of your plugin class!).

We're almost done! We now need to tell KeePass that our file is a KeePass plugin. This is done by editing the Version Information Block of the file. Open the file version editing dialog (in Visual Studio 2005: right-click onto the project name - 'Properties' - button 'Assembly Information'). All fields can be assigned freely except the Product Name field (for more information see Plugin Conventions). This field must be set to `"KeePass Plugin"` (without the quotes).

That's it! Now try to compile your plugin and copy the resulting DLL file into the KeePass directory. If you start KeePass and go to the plugins dialog, you should see your plugin in the list of loaded plugins!

## Common Operations

Adding Menu Items:

Very often you want to add some menu items for your plugin. When clicked by the user, your plugin should get some notification. This can be done like follows. First of all you need to get a reference to the KeePass main menu or one of the special submenus (like Import, Tools, etc.). For this you can use the `IPluginHost` interface, which you received in the `Initialize` function. Then you can use standard tool strip operations to add a new menu item for your plugin. A very simple example, which adds a menu item to the Tools menu:

    private ToolStripSeparator m_tsSeparator = null;
    private ToolStripMenuItem m_tsmiMenuItem = null;

    public override bool Initialize(IPluginHost host)
    {
    	m_host = host;

    	// Get a reference to the 'Tools' menu item container
    	ToolStripItemCollection tsMenu = m_host.MainWindow.ToolsMenu.DropDownItems;

    	// Add a separator at the bottom
    	m_tsSeparator = new ToolStripSeparator();
    	tsMenu.Add(m_tsSeparator);

    	// Add menu item 'Do Something'
    	m_tsmiMenuItem = new ToolStripMenuItem();
    	m_tsmiMenuItem.Text = "Do Something";
    	m_tsmiMenuItem.Click += this.OnMenuDoSomething;
    	tsMenu.Add(m_tsmiMenuItem);
    }

    public override void Terminate()
    {
    	// Remove all of our menu items
    	ToolStripItemCollection tsMenu = m_host.MainWindow.ToolsMenu.DropDownItems;
    	m_tsmiMenuItem.Click -= this.OnMenuDoSomething;
    	tsMenu.Remove(m_tsmiMenuItem);
    	tsMenu.Remove(m_tsSeparator);
    }

    private void OnMenuDoSomething(object sender, EventArgs e)
    {
    	// Called when the menu item is clicked
    }

If you are working with tool strips, you of course have to add a reference to `System.Windows.Forms` of the .NET framework.

It is highly recommended that you unlink all event handlers and remove all menu items created by your plugin in the `Terminate` function (as shown in the example above). After the `Terminate` function has been called, everything should look like before loading your plugin.

In the example, we created a separator and one menu item. To this menu item an event handler for the `Click` event is attached. There's nothing special, this is all standard Windows.Forms code.

For examples of adding popup menus, see the SamplePlugin sample plugin (obtainable from the KeePass plugins page).

Adding Groups and Entries:

For this, see the sample plugin and the KeePassLib documentation.

## Plugin Conventions

File Version Information Block:

KeePass uses the file version information block to detect if a DLL file is a KeePass plugin and retrieves information from it to show in the plugins dialog. The fields are used as follows:

- Title: Should contain the full name of the plugin.
- Description: Should contain a short description (not more than 5 lines) of your plugin.
- Company: Should contain the author name of the plugin.
- Product Name: Must be set to `"KeePass Plugin"` (without the quotes).
- Copyright: Not used by KeePass; freely assignable by the plugin.
- Trademarks: Not used by KeePass; freely assignable by the plugin.
- Assembly Version: Should be set to the version of your plugin.
- File Version: Should be set to the version of your plugin. It is up to you how you are versioning your plugin builds, but it should be a scheme that allows version comparisons (by comparing the version components). Do not use asterisks for creating a version number at build time.
- GUID: Not used by KeePass; freely assignable by the plugin.

Namespace and Class Naming:

The namespace must be named like the DLL file without extension. For example, if the DLL file is named `SecretImporter.dll`, you must call the namespace `SecretImporter`.

The plugin class must be named like the namespace plus "Ext". For the SecretImporter plugin, this would be `SecretImporterExt`.

## Update Checking

The update check of KeePass ≥ 2.18 can also check for plugin updates. Update check support is optional; plugins don't have to support update checks.

In order to support update checks, plugin developers need to do the following:

- Provide version information file. When an end-user invokes an update check, KeePass downloads a version information file, which specifies the current version numbers of one or more plugins. Every plugin author hosts an own version information file. The format of the version information file is described in detail below.
- Let KeePass know. In order to be able to check the plugin's version, KeePass must know where your version information file is located. To let KeePass know, override the `UpdateUrl` string property of your plugin class (the one derived from `Plugin`) to return the full, absolute URL of your version information file. This should be an `http://` URL, but an `ftp://` URL is also acceptable.

Plugin developers have to update their version information file each time they release new versions of their plugins.

Version information file format.

- The file is a simple text file. It must be encoded using UTF-8 without a byte order mark (KeePass ≥ 2.21 supports UTF-8 BOMs in version information files, however for compatibility with KeePass < 2.21 it is recommended not to use a BOM). All line endings are supported.
- The first line of the file must start with a separator character of your choice. The separator character may be any character, but it must not appear within plugin names and versions. Suggested is '`:`'.
- Each of the following lines specifies a plugin name and its currently available version, separated by the separator character that was specified in the header line.
- As plugin name, the value of the 'Title' field in the version information block of the plugin must be specified. For managed plugins, this is the value specified using the `AssemblyTitle` assembly attribute.
- As version number, the value of the file version in the version information block of the plugin must be specified. For managed plugins, this is the value specified using the `AssemblyFileVersion` assembly attribute. Trailing `.0` may be removed (e.g. specify `1.3` instead of `1.3.0.0`).
- The file must end with a line containing only the separator character.
- You may optionally compress your version information file using GZip (note this is not the same as Zip). The file name must then end with "`.gz`".

Example. Let's assume you're developing two plugins: MyPlugin1 (version 1.5) and MyPlugin2 (version 1.13.2.17). Then your version information file could look as follows:

    :
    MyPlugin1:1.5
    MyPlugin2:1.13.2.17
    :

If you've developed multiple plugins, it is recommended to create one version information file, list all your plugins in this file and specify the URL of the file in all your plugins. When KeePass checks for updates, it'll download your version information file only once. This reduces network traffic and is faster than downloading a version information file for every plugin separately.

## Can KeePass 2.x Plugins be written in Unmanaged C++?

Yes and no. You can write the complete logic of your plugin in unmanaged C++ (native Win32 APIs can be used). Anyway you must provide a managed interface to your plugin, i.e. you must export a managed class derived from the `Plugin` base class as described in the step-by-step tutorial.

Also, managed C++ will be required to modify the KeePass internals (i.e. entries, groups, main window, ...).

For an example how to use unmanaged APIs in a managed C++ plugin assembly, see the SamplePluginCpp sample plugin (obtainable from the KeePass plugins page).

## PLGX Files

PLGX is an optional plugin file format for KeePass ≥ 2.09. Instead of compiling your plugin to a DLL assembly, the plugin source code files can be packed into a PLGX file and KeePass will compile the plugin itself when loading it. The advantage of this approach is that plugins don't need to be recompiled by the plugin developers for each KeePass release anymore (as KeePass compiles the plugin itself, the generated plugin assembly references the current, correct KeePass assembly). Instead of shipping a plugin DLL assembly, you ship the PLGX.

For users, nothing changes. Instead of putting the plugin DLL assembly into the KeePass application directory, the PLGX file needs to be put there.

KeePass ≥ 2.14 also loads older plugin DLLs. However, an API within KeePass might have changed and .NET detects this when the plugin tries to call/access the method/class, not at loading time. This means that an incompatibility is detected relatively late and might crash KeePass. In contrast, when using the PLGX format, an incompatibility is detected immediately at loading time: if there is a problem, the compile process will just fail and KeePass can present an informative plugin incompatibility message to the user. Therefore, it is recommended that plugin developers create/ship PLGX files, not DLLs.

Creating PLGX files. PLGX files can be created from plugin sources by calling `KeePass.exe` with the `--plgx-create` command line parameter. If you additionally pass a path to the plugin sources directory (without terminating separator), KeePass will use this one; otherwise it'll show a folder browser dialog to allow you selecting the directory. If you want to pass the directory location using the command line, make sure that you're specifying a full, absolute path -- relative paths will not work.

In order to keep the size of the PLGX file small, it is recommended that you clean up the plugin sources directory before compiling the PLGX. Remove all unnecessary binary files (files in the `bin` and `obj` directory); especially, delete any plugin assembly DLL that you compiled yourself. Temporary files by the IDE (like `.suo` and `.user` files) can also be deleted.

PLGX features:

- Extensible, object-oriented file format.
- Compression support (data files are compressed using GZip).
- `.csproj` support. KeePass retrieves all information required for compiling the plugin assembly from the `.csproj` file in the plugin sources.
- Embedded resources support.
- Referenced .NET assemblies support. References information is read from the `.csproj` file.
- Referenced custom assemblies support. Third-party assemblies required by the plugin (references to DLLs) are supported, provided that the third-party assembly is located in the plugin source code directory (or any subdirectory of it).
- ResX support. `.resx` files are automatically compiled to binary `.resources` files.
- .NET 3.5 support (if the default compiler, which is the one of .NET 2.0, can't compile the code, KeePass tries using the .NET 3.5 compiler).
- PLGX cache. PLGX files are compiled once and the generated assembly is stored in a cache. For all following KeePass starts, no compiling is required.
- PLGX cache maintenance. The size of the PLGX cache can be seen in the KeePass plugins dialog. Here, the cache can also be marked to be cleared (it will be cleared when KeePass is started the next time). An option to automatically delete old files from the cache is supported and enabled by default.

PLGX limitations:

- Currently only C# is supported (not Visual Basic or any other .NET language).
- Linked resources (in different assemblies) are unsupported.
- Dependencies on other projects are unsupported (reorganize your project to use custom assembly references instead).

Defining prerequisites. You can optionally specify a minimum KeePass version, a minimum installed .NET Framework, an operating system and the minimum size of a pointer (x86 vs. x64) using the `--plgx-prereq-kp:`, `--plgx-prereq-net:`, `--plgx-prereq-os:` and `--plgx-prereq-ptr:` command line options. If one of the plugin prerequisites isn't met, KeePass shows a detailed error message to the end-user (instead of a generic plugin incompatibility message). Build example:
`KeePass.exe --plgx-create C:\YourPluginDir --plgx-prereq-kp:2.09 --plgx-prereq-net:3.5`

Valid operating system values are `Windows` and `Unix`. When running on an unknown operating system, KeePass defaults to Windows. Pointer sizes (checking for x86 vs. x64) are specified in bytes; for example, to only allow running on x64, you specify `--plgx-prereq-ptr:8`.

Build commands. Optionally you can specify pre-build and post-build commands using `--plgx-build-pre:` and `--plgx-build-post:`. These commands are embedded in the PLGX file and executed when compiling the plugin on the end-user's system.

In the build commands, the placeholder `{PLGX_TEMP_DIR}` specifies the temporary directory (including a terminating separator), to which the files were extracted. In the post-build command, `{PLGX_CACHE_DIR}` is replaced by the cache directory of the plugin (including a terminating separator), into which the generated assembly was stored.

These build commands can for example be used to copy additional files into the cache directory. Example:
`KeePass.exe --plgx-create C:\YourPluginDir --plgx-build-post:"cmd /c COPY """{PLGX_TEMP_DIR}MyFile.txt""" """{PLGX_CACHE_DIR}MyFile.txt""""`

In order to specify a quote character on the command line, it has to be encoded using three quotes (this is Windows standard, see MSDN: `SHELLEXECUTEINFO`). So, the command line above will actually embed the post-build command `cmd /c COPY "{PLGX_TEMP_DIR}MyFile.txt" "{PLGX_CACHE_DIR}MyFile.txt"` into the PLGX, which is correct. It is highly recommended to surround paths including PLGX placeholders using quotes, otherwise the command will not run correctly if the path contains a space character (which happens very often).

If you need to run multiple commands, write them into a batch file and execute it (with `cmd`). If you need to perform more complex build tasks, write an own building executable and run it using the build commands (typically it is useful to pass the directory locations as arguments to your building executable), for example:
`KeePass.exe --plgx-create C:\YourPluginDir --plgx-build-post:"{PLGX_TEMP_DIR}MyBuild.exe {PLGX_TEMP_DIR} {PLGX_CACHE_DIR}"`