patch hex patterns in file

patch_nops.py

#!/usr/bin/env python3

import re
import binascii
import sys
import time

if len(sys.argv) < 3:
	print("usage: %s <file> <hex pattern> [replace pattern (default all NOPs)]" %sys.argv[0])
	exit(1)

file = sys.argv[1]
data = open(file,'rb').read()

pattern = binascii.unhexlify(sys.argv[2].replace(' ','')) # get rid of spaces
# default replacement, all NOPs
replacement = b"\x90" * len(pattern)

if len(sys.argv) > 3:
	replacement = binascii.unhexlify(sys.argv[3])

print('pattern:',pattern)
print('replacement:', replacement)
found_index = data.find(pattern)
occurrences = 0
while found_index != -1:
	
	if found_index != -1:
		occurrences += 1
		print('found at', hex(found_index))
	found_index = data.find(pattern, found_index+1)

print("found",occurrences,"occurrences")

outfilename = file + "." + str(int(time.time())) + ".patched"

with open(outfilename, 'wb+') as f:
	f.write(data.replace(pattern, replacement))

print("done, written to", outfilename)