My first OS X crackme is finally ready, after a long wait and some unnecessary teasing. Ready means that it is good enough to be released and hopefully give you some trouble to reverse and crack it. I still have many more ideas to implement and some areas could be more polished – it was time to take an executive decision and freeze the code. There are some assumptions (economists love this term) due to the crackme nature – if it was an application more fun games could be played. I hope I haven’t missed any simple hole/bug. It’s not an easy task to build something that you are constantly cracking and thinking about ways to defeat it. I haven’t cracked it myself but I have a few neat ideas on how to approach it. The real interest is to read and learn about your approaches and solutions.

This crackme started as a PoC for some tricks I found while working on a project. The original idea was to create something to demonstrate the issues but it got out of control and evolved into a crackme (I hate to lose and love a good challenge!). Two issues were sort of disclosed during an interview with the fruity company since my interest with overflows is almost 0. The impact of this is that the crackme is certified to run on OS X 10.6.8 up to 10.7.2. Newer Lion releases is a question mark. It is 32 bit only and has no ASLR, due to coding time restrictions. As a matter of fact, I started the PoC with ASLR support, which poses no big problems to the concepts behind this crackme.
The code does nothing malicious or destructive so it’s safe to run! It is only hostile to your reversing efforts.

The challenge is to find the valid name/key pair and keygen it if you wish so. Use the -h argument for help. The crackme will accept the name and key via command line parameters, to make your life easier. Run with no parameters for the usual crackme questions. I will disclose details as soon a solution is sent to me by mail or comment. If you wish to remain anonymous or keep the solution private just tell me.

Probably forgetting about some stuff so this post might be updated soon.

There are two or three little things taken from other people and proper credit will be given in due time.

This should be an advanced crackme with some unusual stuff in OS X (at least for me). I hope you enjoy reversing it and learn/develop some new tricks.
Hint: it is quite amusing that Apple doesn’t follow its own specifications 😉.

Have fun,

SHA256(fg_crackme_nr1.gz)= 9116e336f3979c1c68e63bec2868d193b6ccbf031e3521bdcdb7e14034c3c636