Advanced cracking
A slightly different kind of dongle cracking
by Dr. Fuhrball
4 October 1998
Courtesy of fravia's pages of reverse engineering
Well, Dr Fuhrball calls the investigation of a visual basic
target trough a pure software approach (dead listing and smartchecking)
'methode à la fravia', which is flattering yet inacceptable, since these methods are
known "depuis l'aube de la crackhumanité". Dr Fuhrball demonstrates
here how an hardware approach
("à la +ORC") can
be at times very useful in dongle cracking. Yet something puzzles me:
"Numega's smartcheck shows absolutely
nothing"... are you sure smartcheck's settings were right Dr Fuhrball? If so it would
be REALLY worth checking WHY smartcheck failed... (Matt, r you reading this?). And now enjoy this (advanced) dongle
reversing essay...
A slightly different kind of dongle cracking by Dr. Fuhrball
Todays target is an extremely expensive program with a highly limited
market. Its a tool for advanced modeling and simulation of a mechanical
device. The two pieces of software plus the data acquisition box cost
over $100,000 USD. A search of companys that would be in a position to
use such software came up with less than 100 world wide. The program
is not available on the net.
HINT: 4 wheels
It does however use a slight twist on a trick which makes it interesting
to explore.
This program is massive. 20 custom dll's written in C++, and 30 VB OCX's
29 of which are written in native compiled VB OCX's, and one of which
is compiled to P code.
Two days of soft-icing, wdasming basically led nowhere, because of an
interesting trick exposed later. After a weekend of tracing thru the
VB5 virtual machine, and looking at virtually everything, i finally
discovered 3 different places where the dongle code was called.
Two were in the C++ dll's which took about
10 minutes each. The OCX was an entirely different matter.
After spending these two days "methode à la fravia" I got tired and went
back to "Dr. Fuhrballs patented hardware method". This realized results
in under an hour.
Normally at home i would have used my personal logic analyzer, a
Tektronix 7d01F2.
But I was at work and had a better one. This time a Biomation K205.
This really nice antique has an additional property of being able
to run with completely clockless operation. Setting the jitter time to
20 nanoseconds, and running on just state changes gave a pretty picture
of exactly what was going on.
Oh, lookie, absolutely every time the dongle is accessed, absolutely the
same information is returned. There are alienation bits similar to the
microphar technique, but after printing out 3 different sets of patterns
and holding them up to the light shows the typical device.
One output data line, One output clock line, and one Input data line.
Sad really, one of these days i might actually find a dongle used in a
way thats gonna be really tough.
As an aside, after reading fravia's message board with the guy asking
about the Autocad Crack, I took a look at this, and less than 15 minutes
later had that one obliterated using the same technique below.
Notice: some of the code below has been slightly modified to force you
to actually learn something about how this works.
I decided to write a dongle emulator using a pic chip (www.microchip.com)
Numerous assemblers most of which are shareware or freeware are
available all over the net. You will need a pic programmer however, like
the one that parallax sells.
;PICC54 with 4mhz clock
;instructions take 1 microsecond
;fuses cp=off, wdte=enabled, osc=xt
;count the correct number of pulses ignoring any data
;then output the correct acknowledgement
;its amazing how many different dongles this variation
;on a theme works on
;equates
portb equ 6
w equ 0
count equ 8
pic54 equ 1FFH
org 0
start goto main
main movlw B'00000100'
tris portb
;now wait for SLCT = 1
L1 btfss portb,1
goto L1
;now wait for SLCT = 0
L2 btfsc portb,1
goto L2
;now count 84 clock times
movlw 84
movwf count
;wait for clock=0
L3 btfsc portb,2
goto L3
;wait for clock = 1
L4 btfss portb,2
goto L4
decfsz count,f
goto L3
; now funnel the correct data out
;wait for clock = 0
L4 btfsc portb,2
goto L4
; output databit 0
movlw 0
movwf portb
;wait for clock = 1
L5 btfss portb,2
goto L5
;wait for clock = 0
L14 btfsc portb,2
goto L14
; output databit 1
movlw 4
movwf portb
;wait for clock = 1
L15 btfss portb,2
goto L15
;wait for clock = 0
L24 btfsc portb,2
goto L24
; output databit 2
movlw 0
movwf portb
;wait for clock = 1
L25 btfss portb,2
goto L25
;wait for clock = 0
L34 btfsc portb,2
goto L4
; output databit 3
movlw 4
movwf portb
;wait for clock = 1
L35 btfss portb,2
goto L35
;wait for clock = 0
L44 btfsc portb,2
goto L44
; output databit 4
movlw 0
movwf portb
;wait for clock = 1
L45 btfss portb,2
goto L45
;wait for clock = 0
L54 btfsc portb,2
goto L54
; output databit 5
movlw 4
movwf portb
;wait for clock = 1
L55 btfss portb,2
goto L55
;wait for clock = 0
L64 btfsc portb,2
goto L64
; output databit 6
movlw 0
movwf portb
;wait for clock = 1
L65 btfss portb,2
goto L65
;wait for clock = 0
L74 btfsc portb,2
goto L74
; output databit 7
movlw 4
movwf portb
;wait for clock = 1
L75 btfss portb,2
goto L75
clrwdt
goto L1
org pic54
goto start
END
This works great, however its certainly not a "methode à la fravia" in
that we have not actually learned anything about cracking the software.
OK, now that we know whats going on, we can go back into reversing and
modify the DK12wn32.dll code thats the dongle driver.
Here is a code snippet:
Exported fn(): FindDK12 - Ord:0008h
:200012DD 55 push ebp
:200012DE 8BEC mov ebp, esp
:200012E0 83EC0C sub esp, 0000000C
:200012E3 53 push ebx
:200012E4 56 push esi
:200012E5 57 push edi
:200012E6 33C0 xor eax, eax
:200012E8 66A114300020 mov ax, word ptr [20003014]
:200012EE 8945F4 mov dword ptr [ebp-0C], eax
:200012F1 E9A0000000 jmp 20001396
* Referenced by a Jump at Address:2000139A(C)
|
:200012F6 6AFF push FFFFFFFF
:200012F8 A18C500020 mov eax, dword ptr [2000508C]
:200012FD 50 push eax
* Reference To: KERNEL32.WaitForSingleObject, Ord:026Ah
|
:200012FE FF15D8600020 Call dword ptr [200060D8]
:20001304 8B4508 mov eax, dword ptr [ebp+08]
:20001307 50 push eax
:20001308 E80B080000 call 20001B18
:2000130D 83C404 add esp, 00000004
:20001310 668945F8 mov word ptr [ebp-08], ax
:20001314 6A00 push 00000000
:20001316 6A01 push 00000001
:20001318 A18C500020 mov eax, dword ptr [2000508C]
:2000131D 50 push eax
I think you all know what to do with the first few lines of the
routine to always return the right return code. But once again
its not the "methode à la fravia"
Back to this annoying OCX.
(I do not need to show the two dll's, as they are trivial)
This OCX is compiled to VB5 p code. Numega's smartcheck shows absolutely
nothing. W32dsm89 is also of no use, it generates garbage. Softice
is of some use, but traveling thru the VB5 virtual machine is tons of
fun.
I started writing a VB5 p code discompiler. And kept adding to it as
i encountered p codes that i did not know. Someday I may actually
complete this with all the p codes, then publish it. Its a true mess
at the moment which is why i will not publish it now.
Anyway back to the OCX. With the dongle installed, debugging thru the
mess continued to get VB5 on errors. Without the dongle installed there are
no VB5 on errors, but the code does not run. To make a long story short
here is some pseudo code that shows the trick.
ON ERROR GOTO continuetoprocess
mound of initialization and setup code here
Call the 32 bit dongle code, which calls the dongle vxd
in particular we are looking for a dongle with developer id = XXXXXXX
the return code is 0 for not installed, or 1,2,3 for the device
found on port LPT1,2,3
A=FINDK12(XXXXXX, , ,...)
B=A-1
C=100.0/B
B=B-1
C=100.0/B
B=B-1
C=100.0/B
print out the fact that the dongle was not found!
goto YOULOOSE
continuetoprocess:
Therefore: if error code is floating point divide by zero then
we must have found the dongle!
(this is a little bogus, but is REALLY how the code works.)
Cute little trick. What this shows is that the statement
IF Visual Basic THEN cracked at once
is not necessarily true!
Next I will write an OCX using the above tricks and a few more
to show that cracking VB based protection schemes can be much
tougher than you might think.
But its time for me to have some down time to listen to my new
Wilson speakers.
Advanced cracking
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