OllyDBG, managed to patch file, now can I automate this?

Question

In Olly I managed to patch the file to no longer compare for a specific flag. Is it possible to automate this?

Basically I changed a JNZ to a JZ.

Is there a way to could do the same thing with a hex editor?

The end goal would be to create a program to automate this patch.

Thanks.

Answer 1

Okay, I suppose you just want to create a program that patches the already existing file, so here's how I'd do it.

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First, you need the offset in the file. That means that offset 0 is the first byte, 1 is the second, etc, as opposed to the offset + base which you see in memory.

To get that offset, right click the instruction, and go to View > Executable file:

And you take the offset:

which is 0x16A7 in my case.

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Once you have the offset, you must code a program to patch the program. Here's a few ways: (I only tested the Python one, but the rest should work)

C++

#include <iostream>
#include <fstream>

int main() {
    std::ofstream f("file_to_patch.exe", std::ios::binary);
    // seek to the desired offset
    f.seekp(0x16A7);
    // \x74 to \xEB, for example (conditional short to unconditional short)
    const char bytes[] = "\xEB";
    f.write(bytes, sizeof(bytes));
    f.close();
    return 0;
}

C

#include <stdio.h>

int main(void) {
    FILE* f = fopen("to_patch.exe", "r+b"); // open
    fseek(f, 0, 0x16A7); // seek to the offset to patch
    fwrite((void*) "\xEB", 1, 1, f);
    fclose(f);
    return 0;
}

Python

In case you want to script it and don't wanna bother with C / C++, here's how you do it with Python:

f = open("to_patch", "r+b") # open in read/write binary
f.seek(0x16A7) # seek to the previously found offset
f.write(bytearray([0xEB])) # patch the jump
f.close()

Answer 2

If you want a patch tool you dont need to code it. Use dUP (diablo2oo2 Universal Patcher) or R!SC Process Patcher to easily create a .exe that patches your defined offsets with your defined values.

Answer 3

With OllyDBG2, there is an option for it : Edit > Copy to Executable