razzia's tutorial for vb cracking Filed under ( HACKING CRACKING MAC OS WINDOWS LINUX NETWORK PASSWORD )

razzia's tutorial for vb cracking

Introduction

    Lately more and more programs come out that are programmed in VB.
    Since VB programs are still unknown material for most crackers they
    ignore them and label it as 'uncrackable'. In this document i will
    show you that that is not true for text based protections
    (serials/reg#'s).

    For tools we will need only soft-ice and in one case hiew.
    Further-more i assume that the reader is somewhat familiar with
    cracking. For absolutely beginners i recommend the great tutorials
    made by +orc and ed!son's good windows tutorial. But i will try my
    best to make the text understandable for everyone who has a litle
    knownledge about cracking.

Getting ourselves prepared

    Before i start bombing you with asm listings lets take a moment to
    think about what we are dealing with.
    We are dealing with exe's that dont have code themselves but instead
    they make calls to a library with standard functions.
    What does this mean? It means that this is a big disadventage to
    protect programs written in VB. Why? Do you think that the writers of
    the VB dll made 10 different functions that you can use to compare 2
    strings? No, ofcourse not. They made the dll to be as efficient as
    possible, as small as possible.

    So therefore a good guess is that there will be only 1 or 2 places in
    the dll where it can compare two strings. And that turns out to be the
    case as you will see if you finish reading this document.

    Does the litle lamp already begin to glow in your head ? ;--)
    Wouldnt it be great if we knew where in the dll 2 strings get
    compared? Yes, it would be great. It would reduce VB cracking to a
    boring job of setting a single breakpoint at the right place. Continue
    reading for the details.

Strategy

    Before we continue it would be wise to set out a strategy (like its
    the case with every other case of cracking).

    Lets think about the protection ...
    You enter a string of text , you hit enter or press 'OK' or whatever.
    Then windows gives the data you entered to the VB dll. The VB dll then
    does whatever it needs to know if that data is right or wrong. And you
    get a msg saying you entered a good/wrong code.
    So what would be the weak link in the chain? The answer is where
    windows gives the data you entered to the VB dll. Thats our entry
    point. We can make softice break there. And then we are at the source
    of the protection-chain. With the aid of breakpoints we can then
    monitor what happens with our text.

    I think that we now have enough background information to crack a
    first example.

Case 1 : The Collector v2.1

    The collector is an utility for creating and maintaining your
    image/photo collection. Not bad for a VB program.

    More info about this program :

       Name       : The Collector v2.1
       Where      : http://intranet.ca/~logic/collectr.html
       Size       : collectr.exe = 246.047 bytes
       Protection : serial
       DLL        : uses VB3 dll

    I find it easier to explain things in steps. So therefor i will split
    the cracking process in smaller chunks :

    Step 1 : Run The Collector - right at startup it will ask you for a
    serial #

    Step 2 : Enter a dummy serial like '9876543210'. Now press control-d
    to enter softice. In softice enter 'bpx hmemcpy' to place a breakpoint
    on the hmemcpy function of the kernel.

    Intermezzo : What is hmemcpy ?
    Windows uses hmemcpy alot in operations concerning strings. In this
    case it will be used to copy the buffer with the text we entered to
    the memory space of the VB dll. Remember when i said that we were
    gonna break when windows gave the string we entered to the VB dll?)

    Step 3 : Leave softice with control-d. And press 'OK". This will make
    softice break right at the beginning of hmemcpy.

    Step 4 : Now we will continue with tracing further into the hmemcpy
    function to find out where the string we entered will be stored. Keep
    pressing F10 untill you see this :

    JMP   9E9F
    PUSH  ECX           ;these lines copy the
    SHR   ECX,02        ;string at ds:si to es:di
    REPZ  MOVSD
    POP   ECX
    AND   ECX,03
    REPZ  MOVSB
    XOR   DX,DX

    Step 5: Right before REPZ MOVSD do a 'ed si'. You will the text you
    entered, in my case its shows '0987654321'. Do a 'ed es:di' and you
    will see nothing (yet). But if you press F10 and get passed the REPZ
    MOVSB you will see the text getting copied to this new location where
    the VB dll can access it.

    Step 6: Now we know where the text is located. Lets review our
    strategy here. Our plan was to find out where the VB dll kept our
    serial, then put a breakpoint on that memory location and find out
    with what it got compared. So, lets set a bpr (breakpoint on range) at
    the location with our string. Since the REPZ MOVS(D/B) instructions
    increased the pointer in di (it now points to the end of our string)
    we do 'bpr es:di-8 es:di-1 rw'. Dont hit enter yet - read step 7
    first.

    Step 7: Before you hit enter i will tell you what to expect. Softice
    will break everywhere where that block of memory with the string is
    read or written to.

    For example you will break inside the function strlen where the lenght
    of the string is calculated.
    And you will break where the string is copied to another place in
    memory (for example with REPZ MOVSW). When this happens place a new
    bpr at the new location with the string.
    It will also break when the string or part of it gets deleted. If not
    the whole string gets deleted do not remove the corresponding bpr.
    Only remove it when the complete string gets written over by something
    else.
    Also you will break again in hmemcpy. Hmemcpy will read another echo
    of the string in the dll's memory. Place a bpr there too.
    And finally you will break at the part of the code that does the
    comparing (the instruction you will see is REPZ CMPSB).

    When i reached that part of code i had 4 breakpoints set. One
    breakpoint for hmemcpy and 3 bpr's on 3 echos of the string (or parts
    of it).

    Step 8: Now we found the code where the VB3 dll does comparing we can
    place a breakpoint there and disable the other breakpoints. We wont
    need them anymore. We found the place where things get compared in
    VB3. What you see is this :

    : 8BCA         mov cx, dx
    : F3A6         repz cmpsb  ;<- here the strings in ds:si and es:di
    : 7401         je 8CB6     ;   are being compared
    : 9F           lahf
    : 92           xchg ax,dx
    : 8D5E08       lea bx, [bp+08]
    : E80E06       call 92CB

    Just before the REPZ CMPSB if you do a 'ed si' and a 'ed es:di', you
    will see what is compared with what. In this case the second and third
    character of the string we entered gets comared with 'V8'. So if you
    restart the program and enter 0V87654321 it will register.

    Step 9: We are not finished yet. The contrary is true, the important
    part is what we do now. Next time we meet a VB3 program we want to
    place a breakpoint at the location with the code above and read out
    the right serial.

    How do we do that ? Lets try it real quick with The Collector.
  * Start The Collector and enter a dummy serial.
  * Enter softice and place a breakpoint on hmemcpy.
  * Leave softice and press 'OK', this will put you back in softice.
  * Now, get out of the kernel and and get in the code of VBRUN300 (press
    F11 and F10 untill you get there)
  * Now do a search for the pattern :
    8B,CA,F3,A6,74,01,9f,92,8D,5E,08,E8,0E,06
    :s 0 l ffffffffff 8B,CA,F3,A6,74,01,9f,92,8D,5E,08,E8,0E,06
  * Place a breakpoint at the adress that gets returned
    :bpx 
  * press F5 and you will land in the middle of the above comparing code.
  * Only thing left to do is check out the pointers in es:di and ds:si

Case 2 : Minimize Magic 1.2.4

    Minimize Magic is an utility that you can use to minimize your
    programs to the traybar.

    More info about this program:

       Name       : Minimize Magic 1.2.4
       Where      : http://www.genesoft.demon.co.uk/
       Size       : minimagic.exe =  159.744 bytes
       Protection : password based on key
       DLL        : uses VB4 dll

    To crack this program you can do the same as we did with The
    Collector. Starting with hmemcpy working your way to the code that
    compares the string you entered. Important thing to know is that the
    VB4 dll always converts strings to the WideChar format before it does
    anything with them. So instead of using hmemcpy you can set a
    breakpoint on MultiByteToWideChar to break. Check your windows API
    reference to learn more about this function.

    I have done all the hard work for you and found the VB4 dll code that
    compares two strings (in WideChar format !).

    Heres the listing :

    : 56            push esi
    : 57            push edi
    : 8B7C2410      mov edi, [esp + 10]
    : 8B74240C      mov esi, [esp + 0C]
    : 8B4C2414      mov ecx, [esp + 14]
    : 33C0          xor eax, eax
    : F366A7        repz cmpsw  ;<-- here the (WideChar) strings at ds:esi
    : 7405          je 0F79B362 ;    and es:edi get compared
    : 1BC0          sbb eax, eax
    : 83D8FF        sbb eax, FFFFFFFF
    : 5F            pop edi
    : 5E            pop esi
    : C20C00        ret 000C

    Now we know enough of the VB4 dll to crack Minimize Magic:

    Step 1: Start Minimize Magic and chose Register from the menus. You
    will be asked for a Name and a Password. Enter a name and a dummy
    password. Dont press 'OK' yet, continue with next step.

    Step 2: Enter softice and place a breakpoint on hmemcpy. Leave softice
    and press 'OK'. You will land in softice.

    Step 3: Press F11 and F10 untill you are out of the kernel and in the
    code of the VB40032.dll. Now we will search for the pattern of the
    code above. Do 's 0 l fffffffff
    56,57,8b,7c,24,10,8b,74,24,0c,8b,4c,24,14' and place a breakpoint at
    the adress that gets returned.

    Step 4: Press F5 to leave softice, but you will immediately break
    again, right at the beginning of the above code. Here the password you
    entered will be compared to the correct password. Trace untill right
    before the REPZ CMPSW and do 'ed es:edi', this will show the password
    you entered. If you do 'ed esi' you will see the correct password.
    (the strings will be in WideChar format - for example you could see A
    T G H D E H D. That means your password is ATGHDEHD)

    Ok, now you found a working password that will work only for the
    version on your computer. If you give that password to somebody else,
    the program wont accept it. The password is calculated from a Key that
    is different on each computer. This key could be randomly generated at
    setup or based on the info on your hd. Whichever one it is, it will be
    hard to find out how its generated or where it is stored.

    So how can we make a general crack ?

    We could use the 'Magic Window' trick here. We will 'reprogram' the
    VB40032.dll to show the correct password.

    The original code in the VB40032.dll looks like this :

    :0F79B348 56         push esi
    :0F79B349 57         push edi
    :0F79B34A 8B7C2410   mov edi, [esp + 10] ; es:edi -> pw you entered
    :0F79B34E 8B74240C   mov esi, [esp + 0C] ; esi -> correct pw
    :0F79B352 8B4C2414   mov ecx, [esp + 14]
    :0F79B356 33C0       xor eax, eax
    :0F79B358 F366A7     repz cmpsw          ; compare them
    :0F79B35B 7405       je 0F79B362
    :0F79B35D 1BC0       sbb eax, eax
    :0F79B35F 83D8FF     sbb eax, FFFFFFFF
    :0F79B362 5F         pop edi
    :0F79B363 5E         pop esi
    :0F79B364 C20C00     ret 000C            ; end of this function
    :0F79B367 57         push edi            ; the code below this adress
    :0F79B368 8B7C2408   mov edi, [esp + 08] ; is not important, but we
    :0F79B36C 8B4C2410   mov ecx, [esp + 10] ; will need its space
    :0F79B370 8B44240C   mov eax, [esp + 0C]
    :0F79B374 0BE4       or esp, esp
    :0F79B376 F266AF     repnz scasw
    :0F79B379 B800000000 mov eax, 00000000
    :0F79B37E 7503       jne 0F79B383
    :0F79B380 8D47FE     lea eax, [edi-02]
    :0F79B383 5F         pop edi
    :0F79B384 C20C00     ret 000C

    The code is located at offset 7a748 in the vb40032.dll file. So, to
    make a general crack make a patch that turns the above code into:

    :0F79B348 56           push esi
    :0F79B349 57           push edi
    :0F79B34a 8B7C2410     mov edi, [esp + 10] ;es:edi --> text you enter
    :0F79B34E 8B74240C     mov esi, [esp + 0C] ;esi --> correct pw
    :0F79B352 813F70006300 cmp dword ptr [edi], 00630070 ;edi -> 'PC" ?
    :0F79B358 7527         jne 0F79B381                  ;if not - leave
    :0F79B35A 803E00       cmp byte ptr [esi], 00   |<- these lines
    :0F79B35D 7410         je 0F79B36F              |   put spaces
    :0F79B35F 83C601       add esi, 00000001        |   between the chars
    :0F79B362 C60620       mov byte ptr [esi], 20   |
    :0F79B365 EB03         jmp 0F79B36A             |<--skip the ret
    :0F79B367 C20C00       ret 000C            ;<-- this to prevent crash
    :0F79B36A 83C601       add esi, 00000001        |
    :0F79B36D EBEB         jmp 0F79B35A             |<- back to the start
    :0F79B36F 8B3DDCC47B0F mov edi, [0F7BC4DC]      *<-- these lines
    :0F79B375 8B74240C     mov esi, [esp + 0C]      *    call the
    :0F79B379 6A00         push 00000000            *    MessageBoxA
    :0F79B37B 56           push esi                 *    function to show
    :0F79B37C 56           push esi                 *    the correct
    :0F79B37D 6A00         push 00000000            *    password
    :0F79B37F FFD7         call edi                 *
    :0F79B381 5F           pop edi
    :0F79B382 5E           pop esi
    :0F79B383 90           nop
    :0F79B384 C20C00       ret 000C

    Comments:

    We used the space of two routines, so to prevent a crash we have to
    put a RET function at the beginning of the (original) second function
    (see line 0F79B367).

    This part of the VB4 dll code is not only used to check the passwords.
    It is used by other parts of the program as well. Therefor we need to
    do something so that only something will be shown when we are dealing
    with a password comparison. That is what the code at line 0F79B352 is
    about. It checks to see if EDI points to the text "PC". So we can use
    that to trigger the crack. To trigger the crack, "PC" has to be
    entered for password when registering.

    The lines marked with | are there to put spaces between chars of the
    string. Originally there would be a string of WideChar format. That
    means that in memory there will be zero's between the chars. And the
    function we will use to show the text (MessageBoxA) translates a 0 to
    end of string. So only 1 letter would be shown if we dont replace the
    zeros with spaces.

    The lines marked with * are there to call the function MessageBoxA to
    show the correct password. I ripped those commands from the VB4 dll.
    Placed a breakpoint on MessageBoxA to see how VB4 called it.

    Well thats it for Minimize Magic. To make a general crack, a patch
    could be written that patches the VB4 dll at offset 7a748 with the
    above code. To use such a crack minimagic.exe and the vb40032.dll
    should be placed in a temp dir and the patch run there. Then start
    minimize.exe from that temp dir, and use 'PC' for password. And voila,
    a window will pop up with the correct password. Once the correct pw is
    known, the temp files should be deleted and the password can be used
    in the original Minimize Magic.

Case 3 : Sub Station Alpha 2.02

    Most of the VB4 programs can be cracked with the method described in
    case 2, but i have encountered 2 programs which used a different
    method of comparing. One of those programs is Sub Station Alpha 2.02.
    It uses a protection that first converts a number you enter to its hex
    value and then compares it with the correct number. Lets start to
    crack Sub Station Alpha and things will get clearer.

    Info about this program:

    Name       : Sub Station Alpha 2.02
    Where      : http://www.genesoft.demon.co.uk/
    Size       : SUBSTN32.EXE = 629.248 bytes
    Protection : password based on user name
    DLL        : uses VB4 dll

    Earlier i mentioned that VB4 converts strings to the widechar format
    before it does aything with them. Therefor we will use this function
    as an entry point. Again we will do it step by step ;--)

    Step 1: Start Sub Station Alpha and chose register from the menus.
    Enter a name and a dummy registration key.

    Step 2: Enter softice and place a breakpoint on MultiByteToWideChar
    (with 'bpx MultiByteToWideChar')

    Step 3: Now, leave softice and press "Register".

    Step 4: Softice will break at the beginning of MultiByteToWideChar,
    press F11 to get out of it. You will see :

    :FF1500C27B0F call [KERNEL32!MultiByteToWideChar]
    :8BD8         mov ebx, eax
    :83FEFF       cmp esi, FFFFFFFF
    :7501         jne 0F738BCF
    :4B           dec ebx
    :53           push ebx
    :6A00         push 00
    :FF1518C97B0F call dword ptr [0F7BC918]
    :8BE8         mov ebp, eax
    :85ED         test ebp, ebp
    :0F845B260100 jz 0F74B23D
    :43           inc ebx
    :53           push ebx
    :55           push ebp
    :56           push esi
    :57           push edi
    :6A00         push 00
    :6A00         push 00
    :FF1500C27B0F call [KERNEL32!MultiByteToWideChar]
    :8BC5         mov eax, ebp       ;<-- do 'ed ebp' here
    :5D           pop ebp
    :5F           pop edi
    :5E           pop esi

    The important place is right after the second call to
    MultiByte-ToWideChar. Disable the first bp on MultiByteToWideChar and
    place a new bp right after the second call to that function (on the
    line with MOV EAX,EBP). On that line EBP will contain a pointer to a
    string in WideChar format that was processed. It doesnt have to be the
    string of the registration key. Therefor we will edit that breakpoint
    so that it will only break when it is processing the registration key.

    How can we do that? Well, the MultiByteToWideChar function returns the
    lenght of the string it processed plus 1 in EAX. So we will add a
    conditional statement on the breakpoint. Do 'bl' to find out what the
    number is of that breakpoint. Then do 'bpe #' and add 'if al==' to the
    breakpoint. For example, if you entered '212121', lenghtOfKeyString
    would be 6 :--).

    Step 5: Now we will let the program run with F5. When softice breaks
    do a 'ed edp' and see the WideChar form of the key you entered. We
    place a bpr on the block of memory containing the string and we
    continue (F5). What will happen is this. Softice will break on several
    places. Whats important is that it will break in the code of OLEAUT32.
    When that happens trace a litle further to see whats going on. The
    first few times you will get out of the OLEAUT32 very quickly. But
    eventually you will see this code :

    ( listing from OLEAUT32.DLL)
    :6534B6B3 395C240C cmp [esp + 0C], ebx     ;  this is a loop that
    :6534B6B7 7E14     jle 6534B6CD            ;  goes trough all
    :6534B6B9 33C9     xor ecx, ecx            ;  the chars of a
    :6534B6BB 8D0492   lea eax, [edx + 4*edx]  ;  string, in the end
    :6534B6BE 8A0E     mov cl , [esi]          ;  edx will have the
    :6534B6C0 46       inc esi                 ;  hex value of the string
    :6534B6C1 4F       dec edi
    :6534B6C2 FF4C240C dec [esp + 0C]
    :6534B6C6 8D1441   lea edx, [ecx + 2*eax]
    :6534B6C9 85FF     test edi, edi
    :6534B6CB 7FE6     jg 6534B6B3
    :6534B6CD 85FF     test edi, edi
    :6534B6CF 7F4A     jg 6534B71B
      .............
      .............
    :6534B6F2 8910     mov [eax], edx          ;  edx is saved
    :6534B6F4 33C0     xor eax, eax
    :6534B6F6 83C424   add esp, 00000024
    :6534B6F9 C21000   ret 0010

    Step 6: We saw that the key is transformed into its hex value, and
    saved to a place in memory. If you monitor this memory location, you
    will end up here in the VB4 dll that compares it with another value:

    :0F7A2CE1 5A             pop edx             ; load edx
    :0F7A2CE2 58             pop eax             ; load eax
    :0F7A2CE3 2BC2           sub eax, edx        ; subtract them
    :0F7A2CE5 83F801         cmp eax, 00000001
    :0F7A2CE8 1BC0           sbb eax, eax
    :0F7A2CEA 50             push eax
    :0F7A2CEB 0FB706         movzx word ptr eax, [esi]
    :0F7A2CEE 83C602         add esi, 00000002
    :0F7A2CF1 FF2445F4997B0F jmp dword ptr [2*eax + 0F7B99F4]
    :0F7A2CF8 E8BB000000     call 0F7A2DB8

    We see that EDX and EAX get loaded from the stack, and then
    substracted. This is just an indirect way of comparing those two
    values. If you check out the contents of EAX and EDX, you will see
    that one has the number you entered and the other one will have the
    correct registration number.

    Step 7: Now we found this location its wise to note the hex values of
    the code, so you can find it back quickly when you suspect that
    another VB4 program uses this protection.

Final notes

    Well, with the above 3 techniques i have been able to crack quite some
    VB3/4 programs that used a text based protection. Sometimes when you
    set a breakpoint at the comparing routine, softice will not break. Try
    then to enter strings with a different length. Because the program
    could be checking the length of the string you enter before it
    compares the string itself. And other programs first isolate chars
    from the string you enter and then compare those isolated chars, but
    again they get compared at the locations stated in the examples above.

    With VB5 programs i havent much experience, i only cracked one of
    them. It was called Hitlist Pro v3.0. By patching the VB5 dll, I could
    remove its 30 day timelimit just like it was a regular program. Of
    course, the VB5 dll had to be placed in the Hitlist Pro main dir, this
    to prevent other VB5 programs using the patched DLL.

    Thats it folks, you may contact me (if you know how ;--) on irc with
    feedback and questions.

    Big greets to : tHATDUDE, madmax!, cH, Teraphy, KillerBee,j0b,
    StarDogg Champion,aCP,rANDOM and all the others i forgot.

    Special greets and thanks to +ORC, fravia and gthorne and rest of +HCU

                                                            razzia [pc97]
                                                           date: 05-08-97