Jump to content
Tuts 4 You
Sign in to follow this  
Extreme Coders

[crackme] Find the flag by extremecoders

Recommended Posts

Extreme Coders

This is a CTF style challenge. 


 




Objective  : You need to find the flag which will print the good boy message

Rules      : Everything is allowed

 

Have fun!



 


Virustotal scan


findtheflag.rar

Edited by Extreme Coders (see edit history)
  • Like 4

Share this post


Link to post
Extreme Coders

@GIV: Good Work. :)


 


A little hint if someone else is interested in finding the actual flag. It consists of exactly 30 printable ascii characters.


  • Like 1

Share this post


Link to post
GIV

They can do a simple compare of my patched file with original file. Is just a byte patch.


Is a xor and a compare operation and a simple jump to pass the bad boy message.


 


I have searched in memory the bad boy string, put a hwbp on access on the first letter then when it was triggered i looked in the call stack to see from where it was accessed and forward using the stack i have reached the actual check routine.


I have no patience to recompose the original string just i have put a compare to be equal (EAX=0) and so the program jumps always to good boy.


Edited by GIV (see edit history)

Share this post


Link to post
SmilingWolf

The thing is, in an actual CTF you'd need the string. C'mon yer ol' lad, put a little extra effort in this, at least it is not the usual "überpacked" .NET file, too much of that sith has been posted here in the last year...

Edited by SmilingWolf (see edit history)
  • Like 2

Share this post


Link to post
kao

flag{Y0u_s0lved_that_r1ght!!!}



 


EDIT: I enjoyed it so much that I think it deserves a small writeup. Coming up in few hours.. :)


Edited by kao (see edit history)
  • Like 11

Share this post


Link to post
Extreme Coders

That was quick. I am literally out of words.


 


You actually deserve a prize for this. :)


Share this post


Link to post
Jasi2169

Where there is no hope there is KAO ;)

oh not to forget tonyweb ;)

Edited by Jasi2169 (see edit history)

Share this post


Link to post
Extreme Coders

@Gyrus: Excellent work.  :thumbs:


Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
×
×
  • Create New...