Author:
ttlhacker

Language:
Assembler

Upload:
8:03 PM 10/12/2018

Download

Platform
Unix/linux etc.

Difficulty:
3.0

Quality:
4.0

Arch:
x86-64

Description

x86_64 linux binary (tested on debian 9 and ubuntu 18.04, should run on any distro). Takes one command line argument and outputs "OK!" if it's correct, "Wrong" if it's not. Partially written in C, actual verification routine is assembly. Don't patch the binary, of course - find the correct input. SHA256: 134b53b78fe74d477bf381ebfd965f92d270f8314886518d451ec3aca29156fa hell86

• Comments
• Solutions

s4r on 2:39 PM 10/17/2018: After a quick check this one seems interesting :) Gonna try it when I'll have time

s4r on 12:50 AM 10/20/2018: Done ! Really cool crackme :) I used Dynamorio for instrumentation (in order to look at VM registers). Sha256(flag) = 8fbc397464bcf802e4091e42aff95ded2999e7041b187058cbe2b8818edad777

ttlhacker on 11:22 AM 10/20/2018: Awesome, thanks a lot! :) Another possible way to solve this would've been to write a disassembler for the thing, I guess. By the way, how shoud I best upload its source, now that I forgot to include it in the original upload?

s4r on 6:10 PM 10/21/2018: I've added the source code in the zip file. The password for the source code is the flag which validate the crackme ! Good luck :)

ttlhacker on 3:59 PM 12/14/2018: Amazing write-up, 4aca7f6c! Very nice!

4aca7f6c on 7:26 PM 12/15/2018: Thanks, ttlhacker! This has been one of my favorites so far!

x0r19x91 on 2:46 PM 01/13/2019: Great Challenge !

jeffli6789 on 12:36 PM 05/11/2020: nice one, thx!

jeffli6789 on 12:49 PM 05/11/2020: I wrote a static disassembler for this. Not too hard but takes some time

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