Courtesy of fravia's pages of reverse engineering
~
15 July 1998
Unprotecting unprotectors
or
how AccessData failed itself by relying on StopCopy
by Snooty, July 1998
Tools Needed
Filemon
Regmon
Winasm89
Hex Editor (I like Hexpert)
This is a lesson on fear and learning not to feel it (when it comes
to hacking, that is. You've got a Doberman behind you, run for your
life!) This is a story of how an average cracker took on the big
boys and won. It is also the story of how a company that created
some good DOS-based protection schemes relied on some expensive
third-party protection software and died trying.
Accessdata is a company out of Orem, Utah which specializes in
password cracking for many popular applications - Word, Excel,
WordPerfect, Paradox, Lotus, etc. They have been around since 1985
or so, and their stuff works well. You can reach them at
www.accessdata.com to pick up their most recent Win32 'demo'. This
is a fantastic piece of work (hereafter referred to as 'the target')
that has crackers for over 18 different applications with over 45
versions supported in all. It is the latest and greatest in
deprotection. Licenses are available for different 'modules' that
allow the user to crack specific applications. Note that this demo
is the second demo that Accessdata has distributed. The first one
was written completely for DOS, and was much harder to crack. It is
a great testpiece for crackers to sharpen their skills.
The primary protection on this proggie is a third-party wrapper
written by StopCopy, a commercial vendor. It uses a 'key disk' to
store license data and other random, secret files to lock the
original application. As we will see, there are some other
subroutines that test for code tampering, date changing, and license
altering. You can find out a lot about the program at
http://www.bbics.com/q&a.htm. Here are some intimidating quotes from
the page:
StopCopy is an easy to use, extremely powerful software protection
package which can effectively protect anyone's valuable software
investments. It remains virtually transparent to the honest end-user,
and is loaded with options. PC versions of StopCopy can reliably
defeat all SOFTWARE copiers executing on an IBM/Compatible computer.
Macintosh versions of StopCopy can reliably defeat all SOFTWARE
copiers executing on a Macintosh computer. It is the program of
choice for developers wishing to defeat all software copiers for a
very low price.
Q. What stops a hacker from simply removing the protection code?
A. All StopCopy Products employ extensive encryption and
checksumming routines. (Mommy!) Also, the developer can choose
to use multiple layering (???) , which will afford him even more
protection.
Ok, lets crack this nooge (pronounced knew-j as in 'jerk')
You start this proggie up and you get a splash screen, saying
"Verifying License Data". It obviously can't, then a second box
comes up demanding that you insert your license diskette. But, I
donít have one! So I must hit Cancel and go into demo mode. A third
box pops up saying that I can try it ,etc.,etc. but it will only
recover passwords of 10 characters. OK.
Now a thought for a long time. Was this nooge complete? That is,
was this proggie distributed in its entirety by a greedy software
vendor (with dollar signs for eyes), or were there subroutines on
this license diskette that were vital to the proper operation of the
program. Was StopCopy providing vital services, vital code I would
need to have, or was the key disk some kind of bullshit 'check for
good guy and his license files' crapola?
Run Filemon and Regmon. We see some files being accessed but they
look like the latter - some extremely complicated license files in
some 5000-bit encryption key that no one will ever break. BUT, no
access of vital .dlls or .exes of something like that. This nooge
was complete - how else could it recover the passwords except by
scanning all of them? I felt it at a deep level that I had it by the
balls.
Fire up Winasm8.9
Search through the strings embedded in the prog - we see such
interesting bits as "Law Enforcement Version","Your time has
Come","Operating in Demo Mode" (boo,hiss), and "This Program has been
Corrupted". OK, Let start with the last one, and use a regimented
approach to cracking the schemes one by one. Again, some thought.
Obviously we will need to fix the checksumming routine first, or all
of our efforts will be in vain. Start by finding the string "This
Program has been Corrupted"
This is the relevant code:
:00401D97 A154C05800 mov eax, dword ptr [0058C054]
:00401D9C E8F7570600 call 00467598
:00401DA1 E87AFEFFFF call 00401C20
:00401DA6 E895FDFFFF call 00401B40
:00401DAB 803D20B9500000 cmp byte ptr [0050B920], 00
:00401DB2 7527 jne 00401DDB < ---- check is here!
:00401DB4 6A30 push 00000030
* Possible StringData Ref from Data Obj ->"Corrupted Executable"
:00401DB6 B9E1044F00 mov ecx, 004F04E1
* Possible StringData Ref from Data Obj ->"This program has been
corrupted."
|
:00401DBB BA9F044F0 mov edx, 004F049F
:00401DC0 A108215900 mov eax, dword ptr [00592108]
:00401DC5 E8E6B50900 call 0049D3B0
:00401DCA 33C0 xor eax, eax
Change the 75 to 74 at 00401DB2. Incredibly, that one byte kills off
the so-called 'extensive' checksumming routines.
Phase 2 - Lets kill off the time check by the numbers. Search for
the string "Your Time was Come". Youll find it along with a long
harangue about expiration, order the target, etc.etc,etc. Heres the
snippet:
Referenced by a Jump at Address:004056DC(C)
:00405A94 E82A650900 call 0049BFC3
:00405A99 DD9D60FFFFFF fstp qword ptr [ebp+FFFFFF60]
:00405A9F 8D8560FFFFFF lea eax, dword ptr [ebp+FFFFFF60]
:00405AA5 E836360000 call 004090E0
:00405AAA 3B056CB55200 cmp eax, dword ptr [0052B56C]
:00405AB0 7435 jle 00405AE7 < ---- check is here!
:00405AB2 6A41 push 00000041
* Possible StringData Ref from Data Obj ->"Your Time Has Come"
:00405AB4 B9B34D4F00 mov ecx, 004F4DB3
* Possible StringData Ref from Data Obj ->"This program has expired. You "
->"may click 'Cancel' to attempt "
->"to run it with a license diskette "
->"if you have received one. Otherwise, "
->"click 'OK' to exit the program. "
->" Contact AccessData for details."
Change the 7E to EB and thats the end of the 'extensive' time expiry
protection!
Phase 3 - Lets kill off the demo nag screen by the numbers. Search
the String refs for 'You are About to enter Demo Mode".
* Referenced by a Jump at Addresses:00405B1A(C), :00405BF0(U), :00405C40(U),
:00405D11(C), :00405D44(U) :00405D73(U)
:00405DA2 E82E160200 call 004273D5 < ---- and a suspicious little bastard here!
:00405DA7 84C0 test al, al
:00405DA9 7422 je 00405DCD
:00405DAB 8B0D08215900 mov ecx, dword ptr [00592108]
:00405DB1 80797C00 cmp byte ptr [ecx+7C], 00
:00405DB5 7516 jne 00405DCD < ---- Demo Nag Screen here!
:00405DB7 6A00 push 00000000
* Possible StringData Ref from Data Obj ->"You are about to enter Demo Mode."
:00405DB9 B9B2524F00 mov ecx, 004F52B2
* Possible StringData Ref from Data Obj ->"The Password Recovery Toolkit "
->"demo can recover passwords created "
->"in applications such as WordPerfect"
:00405DBE BA9E4F4F00 mov edx, 004F4F9E
:00405DC3 A108215900 mov eax, dword ptr [00592108]
:00405DC8 E8E3750900 call 0049D3B0
By this time I was breathing pretty easy - StopCopy is a fucking
Joke! Also I thought I had finally split this nooge with one final
edit - after all, it jumps the demo mode. So I Change the 74 to EB
- and nothing happens. A dark pall was cast onto the scene - I felt
a nameless presence, and I knew its name was "Multiple Checks" This
snippet of code was referenced by six different other calls, and I
knew that tracing them down would be a hassle, a snarly maze of irets
and calls twisting in and back on themselves. Long thinky.
I was at the starting point, and I knew the finish too - it was after
the window opened up and everything was loaded, waiting for the user
to do something. I figured that all the security choices would have
already been made by this point, so the solution lay in finding a
reference point in the middle to guide by. Perhaps by working from a
known middle location I could connect the dots and find the path.
Search through the string refs, always the string refs, until I find
one that I like - "Law Enforcement Version". This I like - this must
be on the right path. Lets look at it:
* Possible StringData Ref from Data Obj ->"C:\"
:00407B39 BA8F534F00 mov edx, 004F538F
:00407B3E 8D45FC lea eax, dword ptr [ebp-04]
:00407B41 E81A670600 call 0046E260
:00407B46 FF45D8 inc [ebp-28]
:00407B49 8B10 mov edx, dword ptr [eax]
:00407B4B 8B4DB8 mov ecx, dword ptr [ebp-48]
:00407B4E 8B819C020000 mov eax, dword ptr [ecx+0000029C]
:00407B54 E8C7860D00 call 004E0220
:00407B59 FF4DD8 dec [ebp-28]
:00407B5C 8D45FC lea eax, dword ptr [ebp-04]
:00407B5F BA02000000 mov edx, 00000002
:00407B64 E857690600 call 0046E4C0
:00407B69 E802DBFFFF call 00405670
:00407B6E A154C05800 mov eax, dword ptr [0058C054]
:00407B73 E8E0020700 call 00477E58
:00407B78 8B1554C05800 mov edx, dword ptr [0058C054]
:00407B7E 8955F8 mov dword ptr [ebp-08], edx
:00407B81 837DF800 cmp dword ptr [ebp-08], 00000000
:00407B85 7419 je 00407BA0
:00407B87 66C745CC2000 mov [ebp-34], 0020
:00407B8D BA03000000 mov edx, 00000003
:00407B92 8B45F8 mov eax, dword ptr [ebp-08]
:00407B95 8B08 mov ecx, dword ptr [eax]
:00407B97 FF51FC call [ecx-04]
:00407B9A 66C745CC1400 mov [ebp-34], 0014
* Referenced by a Jump at Address: 00407B85(U)
|
:00407BA0 803DF88A580000 cmp byte ptr [00588AF8], 00
:00407BA7 0F8482000000 je 00407C2F
:00407BAD 66C745CC2C00 mov [ebp-34], 002C
:00407BB3 8D45F4 lea eax, dword ptr [ebp-0C]
:00407BB6 E8E5A9FFFF call 004025A0
:00407BBB 8BD0 mov edx, eax
:00407BBD FF45D8 inc [ebp-28]
:00407BC0 8B45B8 mov eax, dword ptr [ebp-48]
:00407BC3 E89CF50500 call 00467164
:00407BC8 8D55F4 lea edx, dword ptr [ebp-0C]
:00407BCB 52 push edx
:00407BCC 8D45EC lea eax, dword ptr [ebp-14]
:00407BCF E8CCA9FFFF call 004025A0
:00407BD4 50 push eax
:00407BD5 FF45D8 inc [ebp-28]
* Possible StringData Ref from Data Obj ->" - Law Enforcement Version"
|
:00407BD8 BA93534F00 mov edx, 004F5393
:00407BDD 8D45F0 lea eax, dword ptr [ebp-10]
:00407BE0 E87B660600 call 0046E260
:00407BE5 FF45D8 inc [ebp-28]
:00407BE8 8D55F0 lea edx, dword ptr [ebp-10]
:00407BEB 59 pop ecx
:00407BEC 58 pop eax
:00407BED E825690600 call 0046E517
:00407BF2 8D55EC lea edx, dword ptr [ebp-14]
:00407BF5 8B12 mov edx, dword ptr [edx]
:00407BF7 8B45B8 mov eax, dword ptr [ebp-48]
:00407BFA E895F50500 call 00467194
:00407BFF FF4DD8 dec [ebp-28]
:00407C02 8D45EC lea eax, dword ptr [ebp-14]
:00407C05 BA02000000 mov edx, 00000002
:00407C0A E8B1680600 call 0046E4C0
:00407C0F FF4DD8 dec [ebp-28]
:00407C12 8D45F0 lea eax, dword ptr [ebp-10]
:00407C15 BA02000000 mov edx, 00000002
:00407C1A E8A1680600 call 0046E4C0
:00407C1F FF4DD8 dec [ebp-28]
:00407C22 8D45F4 lea eax, dword ptr [ebp-0C]
:00407C25 BA02000000 mov edx, 00000002
:00407C2A E891680600 call 0046E4C0
Scanning upwards from the string ref, we see an unconditional call
from 00407B85, And the best part of all is itís the only one. So
change the 74 to EB at 00407B85. Now at 00407BA7, we have another
conditonal - lets change that one too (from 84 to 85) to streamline
this baby right into the Law Enforcement Version string. I try it
again and it still is not fully functional, although it does say Law
Enforcement Version now. But it still only cracks ten character
passwords. I take a gamble - I know 10 is 0xA and this is a 32-bit
app (the dlls scream it at you), so a stupid protectionist will
compare the password to 0000000A. I search the file and there are
about twenty of them, but one lets off a stinky aroma:
:00430D44 50 push eax
:00430D45 E87759FFFF call 004266C1
:00430D4A 59 pop ecx
:00430D4B 84C0 test al, al
:00430D4D 0F8552010000 jne 00430EA5
:00430D53 837D840A cmp dword ptr [ebp-7C], 0000000A <--- Stinky!
:00430D57 0F8448010000 je 00430EA5
:00430D5D FF7580 push [ebp-80]
:00430D60 8B5508 mov edx, dword ptr [ebp+08]
:00430D63 FFB23C020000 push dword ptr [edx+0000023C]
:00430D69 E85256FEFF call 004163C0
:00430D6E 83C408 add esp, 00000008
:00430D71 0FBEC8 movsx ecx, al
:00430D74 83F94E cmp ecx, 0000004E
:00430D77 7536 jne 00430DAF
:00430D79 66C745984400 mov [ebp-68], 0044
* Possible StringData Ref from Data Obj ->"<No Password>"
|
:00430D7F BAE5245200 mov edx, 005224E5
:00430D84 8D45E8 lea eax, dword ptr [ebp-18]
:00430D87 E8D4D40300 call 0046E260
:00430D8C FF45A4 inc [ebp-5C]
Here we have a compare sandwiched between to calls to the bugger off
routine, right it the middle of the password verification algorithm.
I start (and finish) with this one - change the top jump from 85 to
84.
Now it works!
Several final points:
1. I was intimidated by this program because it had professional
protection. There was no need to be. On the contrary, the original
schemes written by Accessdata is DOS took me about one week each to
crack the proggies one by one.
2. There are of course several types of protection in this scheme -
checksumming, time expiry, the stopcopy stuff, and the ten-character
password check. None of these were hard to beat, but they required a
regimented approach to beat the entire system. By concentrating on a
single step, the journey was finally completed, but none of the steps
were hard.
Finally, I had to change my style three times. I started out
following string references to kill of the checksumming and time
expiry. Then I worked from the middle, transposing from the string
references to call tracing. Finally, I used a little Zen to find the
0000000A connection. As Lee said, be like the water.
Snooty
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