[help] wsprintf

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tutenhamon

Joined: 16 Jan 2010
Posts: 27
Location: Polska (Poland)

tutenhamon 17 Sep 2011, 12:32

Code:

format pe console

include 'INCLUDE\win32ax.inc'

.code
  start:
        invoke  CreateFile, "plik", GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL
        mov [Handle], eax
   invoke  GetSystemTime, lpSystemTime
 invoke  wsprintf, buf, "%i %i %i", [lpSystemTime.wDay], [lpSystemTime.wMonth], [lpSystemTime.wYear]
       invoke  WriteFile, [Handle], buf, eax, edx, NULL ; crashes at the moment
    invoke  CloseHandle, [Handle]
       invoke  ExitProcess, NULL

.data
      lpSystemTime SYSTEMTIME
     Handle  dd 0
        buf rb 256
.end start

why WriteFile was suspended?

Last edited by tutenhamon on 23 Sep 2011, 10:09; edited 1 time in total

17 Sep 2011, 12:32

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Sep 2011, 12:37

because of EDX.

Quote:

lpNumberOfBytesWritten [out, optional]
A pointer to the variable that receives the number of bytes written when using a synchronous hFile parameter. WriteFile sets this value to zero before doing any work or error checking. Use NULL for this parameter if this is an asynchronous operation to avoid potentially erroneous results.

It's pointer.

try:

Code:

invoke  WriteFile, [Handle], buf, eax, wbytes, NULL
wbytes dd ?

also, read this:

Quote:

This parameter can be NULL only when the lpOverlapped parameter is not NULL.

You can also reserve some space and point EDX to it.

17 Sep 2011, 12:37

tutenhamon

Joined: 16 Jan 2010
Posts: 27
Location: Polska (Poland)

tutenhamon 17 Sep 2011, 13:05

its 2 another problems
if i wrote

Code:

invoke   WriteFile, [Handle], buf, eax, d, NULL
d dd 0

Code:

invoke       ExitProcess, NULL

was crashes
and file "plik" was contain

Code:

589841 865732571 -536840879

it is not today date

17 Sep 2011, 13:05

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20516
Location: In your JS exploiting you and your system

revolution 17 Sep 2011, 13:17

The offsets wDay, wMonth and wYear are word values. You need to zero the high portion of the dword before passing to wsprintf.

Code:

;...
movzx eax,[lpSystemTime.wDay]
movzx ecx,[lpSystemTime.wMonth]
movzx edx,[lpSystemTime.wYear]
cinvoke  wsprintf, buf, "%u %u %u", eax, ecx, edx

BTW: wsprintf is a cdecl function. Use cinvoke instead of invoke.

17 Sep 2011, 13:17

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Sep 2011, 13:40

here's working example.

Code:

format pe console

include 'win32ax.inc'

.code 
  start: 
        invoke  CreateFile, "plik", GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL
        mov [Handle], eax 
        invoke  GetSystemTime, lpSystemTime 
        cinvoke  wsprintf, buf, "%u %u %u",dword[lpSystemTime.wDay],dword[lpSystemTime.wMonth],dword[lpSystemTime.wYear]
        invoke  WriteFile, [Handle], buf, eax, d, NULL ; crashes at the moment
        invoke  CloseHandle, [Handle] 
        invoke  ExitProcess, NULL 

.data 
        lpSystemTime SYSTEMTIME 
        Handle  dd 0 
        buf rb 256
        d dd ?
.end start

For me, DWORD values are not causing any fault so, if something will went wrong, use revolution's method. Wink

P.S you have lost stack control when was pushing word values in stack. That was the problem.

P.P.S %i = signed and %u = unsigned.
Time value can't be signed right ? Wink

17 Sep 2011, 13:40

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20516
Location: In your JS exploiting you and your system

revolution 17 Sep 2011, 14:09

Code:

dword[lpSystemTime.wDay],dword[lpSystemTime.wMonth],dword[lpSystemTime.wYear]

... is wrong because you are pushing two word values to make a single dword value. The high portion of the dword will be some other word value from the lpSystemTime structure.

17 Sep 2011, 14:09

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Sep 2011, 15:02

revolution
You're right. I don't knew that they were WORD sizes following each other.. Smile

17 Sep 2011, 15:02

tutenhamon

Joined: 16 Jan 2010
Posts: 27
Location: Polska (Poland)

tutenhamon 23 Sep 2011, 09:47

Thanks

last question:
about '\n' in 2st parameter of wsprintf function?

"%u %u %u\n" gives '23 9 2011\n'

\n eqe 10,13

23 Sep 2011, 09:47

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 23 Sep 2011, 10:23

tutenhamon
try:

Code:

frmt db "%u %u %u",0x0d,0x0a ;0x0d,0x0a = \r\n
...
cinvoke wsprint,buf,frmt,...

>eqe
you mean EQU ?

23 Sep 2011, 10:23

tutenhamon

Joined: 16 Jan 2010
Posts: 27
Location: Polska (Poland)

tutenhamon 23 Sep 2011, 10:51

<"%u %u %u",0x0d,0x0a> as parameter ?

it's works
but is another way?

Overflowz wrote:

>eqe
you mean EQU ?

yes

23 Sep 2011, 10:51

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 23 Sep 2011, 11:15

You're welcome.
about "%u %u %u 0x0d,0x0a" will point you to false positive, because \r\n is defined as variable, not character.
<"..",0x0d,0x0a> will work fine.

23 Sep 2011, 11:15

tutenhamon

Joined: 16 Jan 2010
Posts: 27
Location: Polska (Poland)

tutenhamon 23 Sep 2011, 11:36

\r\n implement to FASM preprocesor or INCLUDE files ?
it's suggestion

23 Sep 2011, 11:36

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