I386 ascii shellcode

[TwoUnderscorez]

I've written a module based on the Riley "Caezar" Eller's technique to bypass data filters, for buffer overflow exploits, on Intel x86 platforms.
http://julianor.tripod.com/bc/bypass-msb.txt
The algorithm to calculate the subtractions for warping around eax is based on https://github.com/VincentDary/PolyAsciiShellGen

[heapcrash]

It looks like your change to changelog.md modifies a lot of lines it shouldn't. Can you fix this? (git checkout origin/master -- CHANGELOG.md then add your change again)

[TwoUnderscorez]

Sorry, my bad. I guess my IDE's auto-formatting kicked in and I've just not noticed. Hopefully it's good now.

[TwoUnderscorez]

I did not realize you still support Python 2, so now that's fixed.

[zachriggle]

I would prefer we also have an ELF.from_bytes().process() test that actually runs some shellcode to ensure that it works. e.g.

>>> sc = shellcraft.echo("Hello world") + shellcraft.exit()
>>> ascii = ascii_shellcode(asm(sc))
>>> ELF.from_bytes(ascii).process().recvall()
b"Hello world"

[TwoUnderscorez]

Added doctest.
Since the shellcode is executing from the code segment and is being unpacked onto the stack, I had to add a jmp esp to the end of the unpacker.
(Usually, the unpacker also runs on the stack, and when eip bumps into esp the unpacked shellcode starts executing).

[Arusekk]

FYI we also have a run_shellcode shortcut somewhere (with a similar debug_shellcode to aid development) that accepts bytes and returns a running process tube, just as above.

[Arusekk]

This code must be moved under pwnlib.encoders.i386.

[TwoUnderscorez]

@Arusekk moved under pwnlib.encoders.i386.

[Arusekk]

Ooofff. That's some great stuff! But I would like it better if it changed a bit. Here you have my MASSIVE review you will find helpful.

[TwoUnderscorez]

Thanks for taking the time to review my code! I'll fix all the cosmetic / pack / bytearray stuff soon. As for python 2 <-> 3 compatible code, It'll probably take me a little longer since I'm less familiar with writing backwords compatible code.

[Arusekk]

Don't worry, it is here all about using bytearray and avoiding ord / chr and consrtucts that are obsolete or too fresh