Member Avatar for personx1212

hi , i have been searching for a way to modify .exe files using python, to make changes to the exe (inject user code), i found examples using other languages, but how can i do this using python? i know it is possible to alter the exe file because i used a tool to password-protect the exe file, and it embeds the password prompt code to the exe it self and the exe size changes after this, so there must be away...

thanks for your help....

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The size change noted by usually means the protector added data or a small loader stub (not simple in-place editing). 's pointer toward a Python debugger/disassembler is on the right track: inspect the file first to see whether it contains a wrapper/stub, added PE section(s), or just modified resources.

Common approaches when modifying a Windows .exe from Python:

  • Append a loader stub or add a new PE section and change the AddressOfEntryPoint so the stub runs first, then transfers control to the original code.
  • Patch code in-place (overwrite instructions or install a trampoline), which requires fixing relocations and imports.
  • Edit resources (dialogs, strings, icons) using Windows resource APIs, which is simpler and less risky if only UI elements are required.

Practical workflow:

  1. Back up the original and work in a VM.
  2. Confirm file type (MZ/PE headers) and locate the Entry Point and section table with a disassembler/debugger. Use the debugger to trace the stub behavior and find where payloads are stored.
  3. Use a PE-aware library to make edits (add section, update SizeOfImage, adjust AddressOfEntryPoint, rebuild relocations and imports). If only small byte patches are needed, calculate file offsets from RVAs correctly (account for FileAlignment/SectionAlignment).
  4. Test repeatedly; expect signed binaries or anti-tamper to fail after modification.

Minimal Python examples (detection and a simple append):

with open('program.exe', 'rb') as f:
    if f.read(2) == b'MZ':
        print('Likely PE file')

with open('program.exe', 'ab') as f:
    f.write(b'\\x00\\x01\\x02')  # append arbitrary payload (toy example)

Notes and cautions: modifying executables breaks digital signatures, can trigger anti-tamper checks, and may violate licenses. Work on copies, test in isolated environments, and prefer PE libraries (pefile, LIEF) or resource APIs rather than blind byte edits.

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Member Avatar for jcao219

This is a debugger/disassembler written in Python:

Member Avatar for personx1212

thanks.

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