W32Dasm ver. 8.7 the textfile-problem
(An hidden memory mover)

by TWD

(15 October 1997)

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Courtesy of fravia's page of reverse engineering

Well, poor Urbanik is under attack once more. I tell you one thing: THIS IS THE LAST ESSAY I WOULD LIKE TO PUBLISH ABOUT WDASM CRACKING. I feel we must leave to this good programmer the time to update his program (which needs it badly IMHO) instead of concentrating (uselessly) on protecting it. I know that some friends will not agree with me (first of all TWD himself, who writes:

Mr. Peter "Cool" Urbanik is a damned Micro$oft pussy as well 

(look at his "official" eMail-address: urbie@msn.com)

Yet I believe that we owe something to Urbanik (I paid my copy, for instance). Look. Our cracking essays are *NOT* his main problem. He knows perfectly well, as well as anybody else who cares looking for them, that THOUSAND copies of his Wdasm 8.9, complete and registered and fully functional, notwithstanding the "This is the Full Version 8.x Series of W32Dasm. It is not to be copied for distribution or downloaded as shareware" warning, are roaming the warez scene (actually pestering the whole Net... I believe you can find them on every major scene's page but mine :-). So our new essays represent a problem only because we are "tackling" the development of his protection schemes, driving him more and more on a tight protection path that does not allow any substantial amelioration of his software product, which, I repeat, is a GOOD (if in need of amelioration) product. By the way, I notice that our good TWD inserts here a series of nop inside the target's code, which is not a very good patching idea: +ORC has always warned us, yet many keep ignoring his warnings. In this case, Urbanik, a simple "wannabye punition" code, snapping on more than four patched nops, would have made havoc inside TWD's computer and given you much more satisfaction that your simple (yet interesting) "cloaking" scheme.

Back to our "deal"...
We will not publish any more reversing essays about Urbanik's targets (we'll obviously work on them and reverse any protection they may have, yet we will keep the results inside the +HCU)... Urbanik will add functionality that WE NEED to the next versions of his creature... (relocation calls identification, less cluttering through strings like "a conditional or unconditional" and so on, he knows perfectly what we need)... call this "a gentleman agreement"... the word of the pirates of ancient times (and ancient sees) was worth a lot ("parole de gentilhomme de fortune"), our word of travellers of the deep code sees is as much worth, I believe.

So this is the last essay I would like to publish on this target (if the rest of the +HCU agrees with me and +ORC does not order me to "stop caring too much for the commercial shareware lusers" :-)
Enjoy this reading: it's a good work by our new contributor TWD

w32dasm version 8.7

by TDW

this is the patch for textfile at w32dasm version 8.7. This one 

is a brand new and very tricky scheme done by Mr. Urbanik.



    this time we patch the textfile-problem of W32Dasm ver. 8.7 



I've read about it on fravia's page and thought that I wanted to have 

a go at thsi target. 

I downloaded version 8.7. at www.expages.com/pages/w32dsm/

You can also search for w32dsm87.zip, in this case you'll find 

protected targets and fully registered versions as well, download 

a protected one in order to follow this essay.



After unzipping it, I had a look at the essay of +Frog's Print

and I thought I could do it the same way. I just looked for the bytes 

and changed them. Well, with the counter this worked (I think so) but

I had a lot of problems with the temporary file. 



Yes, a temporary file is created (I can see it in my tmp-dir) but 

there is nothing inside it. I tried to change the flags of CreateFileA, 

this suggestion was made by +Frog's Print. 

Nothing (0 bytes). 

Then I had a look for the call to DeleteFileA. 

Nothing. Not used.

After this I set a breakpoint on the WriteFile-proc.

Guess what happened ! Nothing again. 

This must mean that Mr. Urbanik doesn't write anything to the 

opened file. Nice idea. The opened file is just a fake (in my 

opinion). 



But if we want a solution to this problem, we have to try...



First, I took a deeper look at the code where the fake-file is

created. The program tries to open a file until the handle of this 

file is not $FFFFFFFF. If we've got a legal handle, it leaves and 

stores the handle in [ebx+000000BF].



:00457D2E E876480000      call 0045C5A9                <-- Open the file

:00457D33 83C408          add esp, 00000008 

:00457D36 8983BF000000    mov dword ptr [ebx+BF], eax  <--- and store the handle 



Now lets look where the handle is used. We set a BPM on ebx+bf.



SoftIce pops up in a region like that.



:00456744 FFB3BF000000    push dword ptr [ebx+000000BF]      <--The handle

:0045674A 8D9360534900    lea edx, dword ptr [ebx+00495360]

:00456750 52              push edx                           <--A string

:00456751 53              push ebx                           <--Memory position

:00456752 E820610000      call 0045C877                      <--???



When we step inside the call, there is a lot of code but one part

is very interesting.



:0045C9E3 8B8B32F00100   mov ecx, [ebx+0001F032]  <--start position of all strings

:0045C9E9 03C8           add ecx, eax                   in memory

:0045C9EB 8BBB2EF00100   mov edi, [ebx+0001F02E]  <--length of strings written

:0045C9F1 03CF           add ecx, edi                   to memory

:0045C9F3 51             push ecx             <--ecx+edi = position where to 

:0045C9F4 8B0C06         mov ecx, [esi + eax]           store the string in esi

:0045C9F7 5F             pop edi

:0045C9F8 890F           mov [edi], ecx

:0045C9FA 83C004         add eax, 00000004

:0045C9FD 3BD0           cmp edx, eax         <--edx = length of the string (esi)

:0045C9FF 77E2           ja 0045C9E3               

:0045CA01 3BD0           cmp edx, eax

:0045CA03 761C           jbe 0045CA21            

:0045CA05 8B8B32F00100   mov ecx, [ebx+0001F032]

:0045CA0B 03C8           add ecx, eax

:0045CA0D 8BBB2EF00100   mov edi, [ebx+0001F02E]

:0045CA13 03CF           add ecx, edi

:0045CA15 51             push ecx

:0045CA16 8A0C06         mov cl , [esi + eax]

:0045CA19 5F             pop edi

:0045CA1A 880F           mov [edi], cl 

:0045CA1C 40             inc eax

:0045CA1D 3BD0           cmp edx, eax

:0045CA1F 77E4           ja 0045CA05

:0045CA21 01832EF00100   add dword ptr [ebx+0001F02E], eax





This piece of code moves a string with the length "edx" from "esi" to 

"ecx". Urbanik moves the string to it's position in memory after

having completed it. And this without any lstrcpy, etc. This part of code 

is essential. You can try to nop it out, or jump over it. Nothing 

will appear after it disassembled enough.



This code stores the string only in memory, but why should it

need the handle of tmp-file. Maybe Mr.Urbanik changed only the contents 

of this procedure and not the parameters, because he did not wanted to 

change the source-code at thousand positions.



Now we can start to change the code...



First we have to change the creation-proc, because we want a 

visible, unhidden file, which will not overwrite any other 

existing files.





:0045C657 6A00          push 00000000                     <-- no template

:0045C659 6880000000    push 00000080                     <-- normal flags

:0045C65E 6A01          push 00000001                     <-- no overwrite

:0045C660 90            nop

:0045C661 90            nop

:0045C662 90            nop

:0045C663 90            nop                               <-- nopping dangerously

:0045C664 90            nop                                   along

:0045C665 90            nop

:0045C666 90            nop

:0045C667 8D93404F4900  lea edx, dword ptr [ebx+00494F40]

:0045C66D 52            push edx                          <--the security struc

:0045C66E 6A00          push 00000000                     <--share - mode

:0045C670 68000000C0    push C0000000                     <--read and write

:0045C675 8D8BC0524900  lea ecx, dword ptr [ebx+004952C0]

:0045C67B 51            push ecx                          <--the filename



* Reference To: KERNEL32.CreateFileA, Ord:0000h

                                  |

:0045C67C E8BBC30100              Call 00478A3C





After we changed the opening-proc, we can proceed with the storing-proc.

If you look above, you can see that Mr. Urbanik uses a very strange

method to move his string in memory. We can do the same in a much easier 

way, using less bytes.



:0045C9F1 03CF            add ecx, edi

:0045C9F3 56              push esi                          <--push source

:0045C9F4 51              push ecx                          <--push destination

:0045C9F5 E8EAA8B1BF      call BFF772E4                     <--call lstrcpy

:0045C9FA 33C0            xor eax, eax

:0045C9FC 668B832B645400  mov ax, word ptr [ebx+0054642B]   <--append a linefeed

:0045CA03 890416          mov dword ptr [esi+edx], eax          to the string

:0045CA06 8BC2            mov eax, edx

:0045CA08 0502000000      add eax, 00000002

:0045CA0D 50              push eax                          <--push # of bytes

:0045CA0E 56              push esi                          <--push source-string

:0045CA0F FFB3BF000000    push dword ptr [ebx+000000BF]     <--push file-handle

:0045CA15 E8CE03B4BF      call BFF9CDE8                     <--call _hwrite

:0045CA1A 2D02000000      sub eax, 00000002                 <--|

:0045CA1F 90              nop                                  |-- The number of 

:0045CA20 90              nop                                  |   bytes must be 

:0045CA21 01832EF00100    add dword ptr [ebx+0001F02E], eax <--|   in eax !!!



Let's explain the code above. First we store the string "esi" at "ecx"

using lstrcpy instead of the ugly code. Then we append a linefeed (0D +

0A) to our string, which we want to write to the file. 

We have to increase "eax" by two because we want the two linefeed-bytes 

written to disk too. 

Now push all this cram and call _hwrite. In "eax" is the number of bytes 

written to disk. At line "0045ca21" the length of the string is added to 

the number of previously written/stored bytes. That means that we have

to decrease "eax" by two. This saves two bytes of memory for each line.

Two nops are making the patch perfect.



But there is another position where the handle of the tmp-file is

pushed. This one is only an example but the one that you will find must 

look similar. This proc is used to store empty lines in memory. 

In the tmp-file we do not need them but it is much easier to read if we 

have them.



:00415E04 FFB3BF000000            push dword ptr [ebx+000000BF]

:00415E0A 53                      push ebx

:00415E0B E8426C0400              call 0045CA52



Hmm, strange... Only the handle and the memory - position are pushed.



If we have deep look inside the procedure we find this code :



:0045CAE5 8B9301505400      mov edx, [ebx+00545001]

:0045CAEB 85D2              test edx, edx

:0045CAED 7520              jne 0045CB0F             <-- The god guy is allowed

:0045CAEF 8B8B32F00100      mov ecx, [ebx+0001F032]     ;to jump to the WriteFile

:0045CAF5 8B832EF00100      mov eax, [ebx+0001F02E]

:0045CAFB 668B932B645400    mov dx, [ebx+0054642B]

:0045CB02 66891401          mov [ecx + eax], dx

:0045CB06 83832EF0010002    add dword ptr [ebx+0001F02E], 00000002

:0045CB0D EB1D              jmp 0045CB2C             <--The bad guy not !!!

:0045CB0F 6A00              push 00000000

:0045CB11 8D4DFC            lea ecx, [ebp-04]

:0045CB14 51                push ecx

:0045CB15 6A02              push 00000002

:0045CB17 8D832B645400      lea eax, [ebx+0054642B]

:0045CB1D 50                push eax

:0045CB1E FF750C            push [ebp+0C]



* Reference To: KERNEL32.WriteFile, Ord:0000h



:0045CB21 E838BE0100              Call 0047895E

:0045CB26 898307881100            mov [ebx+00118807], eax



I don't know why, but here we got the possibility to re-use some code.

If the "jne" is changed to a "jmp" the empty line is written to file.



:0045CAE5 8B9301505400            mov edx, dword ptr [ebx+00545001]

:0045CAEB 85D2                    test edx, edx

:0045CAED EB20                    jmp 0045CB0F          <--Yes, jump always





Now we have changed all the important things. You can change the

extension of the tmp-file from .tmp to .txt by searching for "w32dsm" 

in the exe-file.



The cracking of the counter is not as essential as the saving of

the textfile. I tried the suggestion of Frog's Print. Maybe it worked. 

But if not you can also use a good program, like UltraEdit32

 to browse through the textfile.



That's all ...



    TWD





    mailto:twd.rulez@gmx.net



(c) by TWD in 1997 

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