#!/usr/bin/env python
# Small IDA .dif patcher
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, e:
		print "Error: %s" % str(e)
		exit(1)

if __name__ == "__main__":
	main()