Reverse engineering dll and reuploading directly to server

Question

I was given a task to edit an existing website however the client has no access to the source code anymore so I accessed what I could on the Virtual Machine. However, the only files I could get from the VM are the front-end files. I need to change something in the controllers so I was looking at reverse engineering the project DLL.

Is it possible to just decompile the current dll, create a new project, copy everything, compile a new working dll and just reupload the dll file to the server? From my experience as a programmer, dlls are given a GUID identifier that gets compiled with the solution when it is deployed. I think recreating the project will assign a different GUID for the new DLL. Will this be alright when it is uploaded to the server?

Any help and clarification is appreciated. Thanks.

Answer 1

Yes, the reuploaded DLL should be fine

But, in the case of strongly named assemblies anything that references that DLL won't be too happy. In which case; you'll need to do the same process with those and link against your new project. Which you'll probably want to do anyway so you aren't trapped by their behavior.

IIS itself won't care; it's just looking for an assembly with the entrypoint.

Answer 2

Here's an answer to a similar question: How do I decompile a .dll file?

It's more of a maybe... Try it and see if it works. You will need to know what framework and assemblies are tied into the library and what language it's programmed in.

Answer 3

Yes, rebuilding the DLL from scratch will work unless the "uploading" process has certain particularities we're unaware of (such as assigning GUIDs to DLLs).

In reality, however, depending on the language used automatic decompilation may not be so straightforward, and doing it manually is a complex and difficult task, so I would approach that task with caution.