Is there a Visual Basic 6 decompiler?

ghz 7months ago ⋅ 88 views

I lost the source code from one project I did on the company I'm working for and haven't been able to find a Visual Basic 6 decompiler; does that even exists?

I only have the EXE that I've rescued from a user's machine.

Answers

Unfortunately, there isn't a straightforward decompiler for Visual Basic 6 (VB6) executables that can fully reconstruct the original source code. VB6 applications are compiled into native machine code, which makes the decompilation process challenging. However, there are some tools and methods that can help you partially recover code or understand the structure of the executable:

Tools for Partial Recovery and Analysis

  1. VB Decompiler

    • VB Decompiler is a commercial tool that can decompile Visual Basic 5.0 and 6.0 programs. It can recover some parts of the source code, such as forms, procedures, and some code, but it won't be able to give you the exact original code due to the nature of compiled executables.
    • Website: VB Decompiler

  2. Hex Editors and Disassemblers

    • Tools like Hex Workshop or Hiew can be used to inspect the binary structure of the executable.
    • IDA Pro or OllyDbg are disassemblers that can help you analyze the machine code, though this requires advanced knowledge of assembly language and the VB6 runtime.

  3. Resource Extractors

    • Tools like Resource Hacker can extract embedded resources, such as forms and string tables, which can give you some insight into the user interface and text used in the application.
    • Website: Resource Hacker

Steps to Attempt Recovery

  1. Using VB Decompiler:

    • Download and install VB Decompiler.
    • Open your EXE file with VB Decompiler.
    • The tool will analyze the executable and display recoverable code, forms, and controls.
    • Save the decompiled data. Note that the recovered code might need manual correction and reorganization.

  2. Extracting Resources:

    • Open the EXE file with Resource Hacker.
    • Navigate through the different resource sections to extract forms, images, icons, and string tables.
    • Save the resources for reference or reuse in rebuilding the application.

  3. Analyzing with Disassemblers:

    • Load the EXE file into a disassembler like IDA Pro.
    • Analyze the assembly code to understand the logic of the program.
    • This step is complex and may not be practical for most VB6 applications unless you have experience with assembly language.

Rebuilding the Application

Once you have recovered as much as possible using the above tools, you can start rebuilding the application:

  1. Recreate Forms and Controls:

    • Use the extracted forms and controls to rebuild the user interface in VB6.

  2. Rewrite the Code:

    • Use the decompiled code as a reference to rewrite the business logic.
    • Pay attention to any API calls or external dependencies that need to be addressed.

  3. Testing and Validation:

    • Thoroughly test the rebuilt application to ensure it functions as expected.
    • Compare the behavior with the original executable to identify and fix any discrepancies.

While these methods can help you recover some parts of your VB6 application, it's unlikely that you will get a perfect reconstruction of the original source code. It's always a good practice to maintain proper backups and version control to prevent such situations in the future.

#VB6