#!/usr/bin/env python

# Small IDA .dif patcher - https://stalkr.net/files/ida/idadif.py

import re
from sys import argv,exit

def patch(file, dif, revert=False):
	code = open(file,'rb').read()
	dif = open(dif,'r').read()
	m = re.findall('([0-9a-fA-F]+): ([0-9a-fA-F]+) ([0-9a-fA-F]+)', dif)
	for offset,orig,new in m:
		o, orig, new = int(offset,16), orig.decode('hex'), new.decode('hex')
		if revert:
			if code[o]==new:
				code = code[:o]+orig+code[o+1:]
			else:
				raise Exception("patched byte at %s is not %02X" % (offset, ord(new)))
		else:
			if code[o]==orig:
				code = code[:o]+new+code[o+1:]
			else:
				raise Exception("original byte at %s is not %02X" % (offset, ord(orig)))
	open(file,'wb').write(code)

def main():
	if len(argv)<3:
		print("Usage: %s <binary> <IDA.dif file> [revert]" % (argv[0]))
		print("Applies given IDA .dif file to patch binary; use revert to revert patch.")
		exit(0)

	file, dif, revert = argv[1], argv[2], False
	if len(argv)>3:
		revert = True
		print("Reverting patch %r on file %r" % (dif, file))
	else:
		print("Patching file %r with %r" % (file, dif))

	try:
		patch(file, dif, revert)
		print("Done")
	except Exception as e:
		print("Error: %s" % str(e))
		exit(1)

if __name__ == "__main__":
	main()