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Reverse Code Engineering RCE CD +sandman 2000
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tutor9.txt
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2000-05-25
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81 lines
Terminal Cilla's
Tutorial#9
[Target Infos:]
[Name :] CrackMe 5
[Author:] nOp3x
[Type :] Time-Trial
[Where :] http://crackmes.cjb.net
[Needed Tools:]
SoftIce
WinDasm
[Our Aim:]
Finding the valid time-period
-----------------------------------------------------------------------------
Hi Reader.
I'm sorry for all grammatical and orthographic errors.
I assume that you already configured your SoftIce/WinDasm and
that you are basicly down with them - otherwise stop reading
and take a "SoftIce/WinDasm4Newbies - Tutorial".
Still here?
Ok, let's go!
TheEssay: (happy 1997)
---------
1.
While starting the target, we noticed the messagebox, which
informed that the trial-period has ended. The same string
will also be found in the main-program.
So, we must find a breakpoint which breaks on
GetTime-accesses. I set it on 'GetLocalTime' because
it is used very often for such protection-schemes.
Ok, now let's start the crackme and Sice will break
in the moment. We are in the code of the 'GetLocalTime-function',
just press 2 times F12 and we get into the calendar;=)
--------------What-year-do-we-have-?---------------
* Reference To: cw3220._getdate, Ord:0000h
|
:0040108A E83F040000 Call 004014CE
:0040108F 59 pop ecx -> we land here
:00401090 817DF8CD070000 cmp dword ptr [ebp-08], 000007CD
//ohh, what's that? The result of the GetTime function is
compared with something. 7CD in hex means 1997 in dec.
Take a short look at the eax register: for me it says
7CF, which's 1999 in dec. Get the clue?
//
:00401097 7F0F jg 004010A8 ->is current year
greater as 1997
than expire-msg
----------------------------------------------------
We can do a clock-rollback to check that.
Set the year on 1997 and run the crackme again...
...our job is done!
Thx4Readin'
-----------------------------------------------------------------------------
-=I'm still a newbie - So I can only get better!=-
(c) Terminal Cilla (mai 1999)
Peace&Respects 2: BJanes,Lazarus, Torn@do, nOp3x
klefz, Sanhedrin,rubor and all crackme-coders
and tutorial-writers.
Special thx2 'duelist' for beeing a good friend and
'Eternal Bliss' for hosting my cMz.
________________________
| Be sure to visit: |
| http://crackmez.cjb.net|
| & |
| http://crackmes.cjb.net|
|________________________|