Retrieve CLR DLL from SQL Server

Question

Is it possible to rebuild or retrieve a VB CLR dll file which you've imported into SQL some time ago? I've gotten to the point where I was able to find the contents of this DLL by doing:

SELECT * FROM sys.assembly_files

but I don't how if it's possible to rebuild the dll with the contents found there.

Any help would be very appreciated :)

Answer 1

I finally figured it out. I've added a new assembly which handles the creation of the DLL:

CREATE ASSEMBLY [SqlServerProject1]
AUTHORIZATION [dbo]
FROM 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WITH PERMISSION_SET = UNSAFE;

After that I add my procedure to consume it:

CREATE PROCEDURE [dbo].[sspSaveAssemblyToDisk]
@pAssemblyname NVARCHAR (4000), @pFilename NVARCHAR (4000)
AS EXTERNAL NAME [SqlServerProject1].[SqlServerProject1.StoredProcedures].[sspSaveAssemblyToDisk]

And then I run my procedure and give it the path to save my file and the name of the assembly:

exec sspSaveAssemblyToDisk 'MyAssemblyName','C:\Assemblies\MyAssembly.dll'

Make sure you have writing rights to the location you're saving your file, and there you go!

Answer 2

There is a very good example here. The following code comes from the link provided.

DECLARE @IMG_PATH VARBINARY(MAX)
DECLARE @ObjectToken INT

SELECT @IMG_PATH = content FROM sys.assembly_files WHERE assembly_id = 65536

EXEC sp_OACreate 'ADODB.Stream', @ObjectToken OUTPUT
        EXEC sp_OASetProperty @ObjectToken, 'Type', 1
        EXEC sp_OAMethod @ObjectToken, 'Open'
        EXEC sp_OAMethod @ObjectToken, 'Write', NULL, @IMG_PATH
        EXEC sp_OAMethod @ObjectToken, 'SaveToFile', NULL, 'D:\SqlServerProject1.dll', 2
        EXEC sp_OAMethod @ObjectToken, 'Close'
        EXEC sp_OADestroy @ObjectToken

I should imagine .NET Reflector will be your friend in reverse-engineering the DLL once extracted, but I have no idea if it's encrypted in any way.

Answer 3

I ended up doing this.

I got the create script for the CLR assembly for which I want to generate the dll.

CREATE ASSEMBLY [asmClr]
AUTHORIZATION [dbo]
FROM [some_hex_value] //hex value removed for brevity
WITH PERMISSION_SET = UNSAFE;

I converted the hex value (some_hex_value) to bytes using C# after removing the starting "0x" string. There are LINQ examples on SO too for converting hex to bytes.

byte[] StringToByteArray(string hex)
{
    var bytes = new byte[hex.Length / 2]; // 2 hex chars = 1 byte
    for (int i = 0; i < bytes.Length; i++)
    {
        string bytehex = hex.Substring(2*i, 2);
        byte b = Byte.Parse(bytehex, NumberStyles.HexNumber);
        bytes[i] = b;
    }
    return bytes;
}

I wrote the bytes to the file system.

File.WriteAllBytes(@"D:\clr.dll", bytes);

I used ILSpy to look into the dll source.