BoxedApp Blog

.NET Applications: How to Hide Assemblies And Unmanaged DLLs

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• Author: Artem A. Razin
• June 11, 2008
• Category: .NET, examples, use cases

One interesting task I’ve heard from one of our first customers is hidding assemblies and unmanaged DLLs. The target language is C#. Let’s explore how to solve this task with BoxedApp SDK.

At the first, decide how to store an assembly. In this example, I keep an assembly in static array. To create C# code with such array, I use the following code:

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace ConvertBinToSharpCode
{
    class Program
    {
        static void Main(string[] args)
        {
            byte[] data = File.ReadAllBytes(args[0]);

            Console.Write("namespace BinData\n{\n\tpublic class Data1\n\t\t{\n\n\t\tpublic static byte[] data = \n{\n");

            foreach (byte b in data)
            {
                Console.Write(b.ToString() + ",");
            }

            Console.Write("};\n}\n}\n");
        }
    }
}

It takes one argument (path to an assembly) and outputs C# code, save it as data.cs, for example:

namespace BinData
{
	public class Data1
		{

		public static byte[] data = 
{
77,90,144,0,3,0 .......
}
}

Include it to the main solution.

Now, how to create a virtual file with assembly and fill it from the BinData.Data1.data:

static void CreateAssemblyInMemory(
   string strVirtualPath, 
   byte[] data)
{
   IntPtr hHandle =
      BoxedAppSDK.NativeMethods.BoxedAppSDK_CreateVirtualFile(
         strVirtualPath,
         BoxedAppSDK.NativeMethods.EFileAccess.GenericWrite,
         BoxedAppSDK.NativeMethods.EFileShare.Read,
         IntPtr.Zero,
         BoxedAppSDK.NativeMethods.ECreationDisposition.New,
         BoxedAppSDK.NativeMethods.EFileAttributes.Normal,
         IntPtr.Zero);
   CloseHandle(hHandle);

   using (FileStream VirtualFileStream = 
            new FileStream(strVirtualPath, FileMode.Open))
   {
      VirtualFileStream.Write(data, 0, (int)data.Length);
   }
}

Now how to create an assembly into memory:

CreateAssemblyInMemory(@"Z:\myclass.dll", BinData.Data1.data);

Assembly assembly = Assembly.LoadFrom(@"Z:\myclass.dll");
object o = assembly.CreateInstance("myclass.Class1");
o.GetType().GetMethod("SomeMethod").Invoke(o, null);

Another option, when your application uses some assembly and you would like to keep this assembly in memory. In this case, you write:

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        BoxedAppSDK.NativeMethods.BoxedAppSDK_Init();

        // Creates a virtual file with assembly
        // before using the assembly, in 
        // other words, the assembly is not 
        // loaded yet
        CreateAssemblyInMemory(
           Application.StartupPath + @"\\Assembly1.dll", 
           BinData.Data1.data);

        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        // The Form1 will be created, 
        // Form1 loads the assembly Assembly1.dll, 
        // BoxedApp SDK provides it from memory
        Application.Run(new Form1());

        BoxedAppSDK.NativeMethods.BoxedAppSDK_Exit();
   }
...
}

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