Issues with elf file injection tutorial by pico

[0x00pf (pico)]

Hi @bramble,

Thanks for reading my tutorial hope you enjoyed it and find it somehow useful.

@bramble

However I’m unsure of what this command is supposed to be doing, and why?

r = v ^pat;

This is just a XOR that will be 0 whenever both values v and pat are equal. It is just a way to check if you have found the pattern you are looking for.

@bramble

because we patched the original entry point and the return address to point back to the original code for normal execution after our payload right? So is the return address pointing to the wrong location?

That is probably the case. The best way to find out is just to debug your patched program and see what is going on. Actually that’s the best way to fully understand this kind of stuff.

Go run the debugger, find the problem and fix it!

@bramble

apparently it only works when the elf is static

I’d used dynamic binaries while writing the tutorial, so, I believe the real reason behind this behaviour is something else… Verify your binaries are not PIE, for instance.

Take a look to this other thread

Segfaults With Polycrypt Tutorial

Had a question about this tutorial: I’ve tried double-checking the code several times. Even tried pulling it off this github to ensure I wasn’t missing anything: https://raw.githubusercontent.com/0x00pf/0x00sec_code/master/crypter/polycrypt.c Every time I try to run it I get the following though: $ ./polycrypt mprotect:: Cannot allocate memory Segmentation fault At first I thought this may be some security feature on my device that was preventing that. However, I was able to execute the…

Hope this helps