genpatch

genpatch is IDA plugin that generates a python script for patching binary from Patched Byte on IDA Pro. genpatch is confirmed to work on IDA Pro 7.4 and above

Motivation

During reverse engineering, we often apply the same patch to another binary. For example, when applying patch for bypassing SSL pinning. Launching IDA Pro just to patch is cumbersome, but patching from the CUI is more convenient, it's easy to share with others who are not familiar with IDA Pro.

Installation

Copy file genpatch.py, patch_script_template.txt to IDA Plugin folder, then restart IDA Pro to use genpatch.

On Windows, the folder is at C:\Program Files\IDA 8.x\plugins
On MacOS, the folder is at /Applications/IDA Pro 8.x/idaq.app/Contents/MacOS/plugins
On Linux, the folder may be at /opt/IDA/plugins/

How to Use

Generate Patch Script

After applying the patch using IDA Pro, click Edit -> Plugins -> genpatch button.

If patch script is successfully generated, a dialog similar to following appears:

A Patch script is generated in the directory where the binary read on IDA Pro is located. The name of the Patch script will be the binary you are reading with the suffix _patch.py. For example, if the binary name is a.out, the patch script name will be a.out_patch.py.

Run the generated patch script

Specify the path to the binary you wish to patch as a command line argument.

$ python foo_patch.py <target_binary_path>

Patching Script Example

#!/usr/bin/env python
# coding: UTF-8

import binascii
import os
import re
import sys

target_path = sys.argv[1]
target_data = None
with open(target_path, 'rb') as target_file:
    target_data = binascii.hexlify(target_file.read()).decode('utf-8')

# address: 0x100000ecb
# function name: __text: _main
# comment: Keypatch modified this from:   jz loc_100000EF6 Keypatch padded NOP to next boundary: 4 bytes
matches = re.findall('0f8425000000', target_data)
if len(matches) == 1:
    target_data = target_data.replace('0f8425000000', '752990909090')
else:
    print("Patch pattern isn't unique")
    sys.exit()

result_path = f'{target_path}_patched'
with open(result_path, 'wb') as result_file:
    if sys.version_info[0] >= 3:
        result_file.write(bytes.fromhex(target_data))
    else:
        result_file.write(target_data.decode('hex'))

print("Successfully generated patched binary to '%s'" % result_path)

License

MIT License

sterrasec/genpatch