How to decompress a Fody.Costura packed assembly

Question

A friend of mine gave me the challenge to decompress an assembly that was packed with Fody.Costura. The assembly has a dll dependency that was embedded as a resource. I tried to extract this .zip resource with dotPeek and decompress it with this code here

public static void Decompress(string path)
{
    using (var stream = File.OpenRead(path))
    using (var compressStream = new DeflateStream(stream, CompressionMode.Decompress))
    {
        compressStream.Seek(0, SeekOrigin.Begin);
        var fs = File.Create(path + ".decompressed");
        compressStream.CopyTo(fs);
        fs.Close();
    }
}

This works when it comes to extracting the .zip but the result is quite unuseful

Is there a suitable solution to decompress this packed dll?

Answer 1

The code that Costura uses to decompress those resources is here.

https://github.com/Fody/Costura/blob/master/src/Costura.Template/Common.cs

static void CopyTo(Stream source, Stream destination)
{
    var array = new byte[81920];
    int count;
    while ((count = source.Read(array, 0, array.Length)) != 0)
    {
        destination.Write(array, 0, count);
    }
}

static Stream LoadStream(string fullname)
{
    var executingAssembly = Assembly.GetExecutingAssembly();

    if (fullname.EndsWith(".zip"))
    {
        using (var stream = executingAssembly.GetManifestResourceStream(fullname))
        using (var compressStream = new DeflateStream(stream, CompressionMode.Decompress))
        {
            var memStream = new MemoryStream();
            CopyTo(compressStream, memStream);
            memStream.Position = 0;
            return memStream;
        }
    }

    return executingAssembly.GetManifestResourceStream(fullname);
}