PEDiffGen

A simple PE subtraction utility.

PEDiffGen.exe <pe1> <pe2> <output>

The above command generates the result of pe1 - pe2 in memory (as in, matching up with virtual addresses). This can be applied onto an in-memory image easily:

  for (size_t i = 0; i < diff_size; i += 0x1000)
  {
    const auto curr = diff + i;
    const auto chunk_size = std::min((size_t)(diff_size - i), (size_t)0x1000);
    if (std::all_of(curr, curr + chunk_size, [](uint8_t c) { return !!c; }))
      continue;
    uint8_t page[0x1000];
    std::transform(curr, curr + chunk_size, dll_base + i, page, [](uint8_t a, uint8_t b) { return a + b; });
    unprotect_memcpy(dll_base + i, page, chunk_size);
  }

It is recommended that you compress the subtraction result as most of it is zeros. After compression, this should produce one of the smallest possible footprints compared to other diffing methods.

License

PEDiffGen - A PE file subtraction tool
Copyright (C) 2021  namazso <[email protected]>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.