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[masm] ReadProcessMemory error

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zart
Master Cheater

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Joined: 20 Aug 2007
Posts: 351
Location: russia

Posted: Sat Sep 15, 2007 7:44 pm Post subject: [masm] ReadProcessMemory error

Ok here is a snippet from a masm program I was toying with;

Code:

.if process == NULL
   ; throw error not finding process
.else
   invoke VirtualProtectEx,process,theoffsettopatch,100,PAGE_EXECUTE_READWRITE,ADDR OldProtected
   .if eax == 0
      ; error unprotecting memory
   .else
      invoke ReadProcessMemory,process,theoffsettopatch,ADDR TheReadValue,SIZEOF TheReadValue,0
      invoke GetLastError
      invoke wsprintf,ADDR outBuffer,ADDR decimalformat,eax
      invoke MessageBox, NULL, addr outBuffer, addr caption, MB_OK
   .endif
.endif

Well I can get the process fine - and the VirtualProtectEx appears to be working fine. The ReadProcessMemory is failing with error code 5. This is an access restriction error...

Hopefully someone can point me in the right direction with this one, I'm probably just doing something dumb. Is the VirtualProtectEx not working as I am expecting it to be? Or is my ReadProcessMemory bad...
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appalsap
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Joined: 27 Apr 2006
Posts: 6753
Location: Pakistan

Posted: Sat Sep 15, 2007 7:49 pm Post subject:

Did you open the process with PROCESS_VM_READ and PROCESS_VM_OPERATION rights?

zart
Master Cheater

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Joined: 20 Aug 2007
Posts: 351
Location: russia

Posted: Sat Sep 15, 2007 7:51 pm Post subject:

appalsap wrote:

Did you open the process with PROCESS_VM_READ and PROCESS_VM_OPERATION rights?

DOH!

Figured it would be something simple like that... I was opening it with PROCESS_VM_WRITE OR PROCESS_VM_OPERATION...

Thanks app Very Happy

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zart
Master Cheater

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Joined: 20 Aug 2007
Posts: 351
Location: russia

Posted: Sat Sep 15, 2007 8:01 pm Post subject:

x0r wrote:

Well all the parameters for VirtualProtectEx & ReadProcessMemory seem to be correct so I'm just going on the process identifier (handle) being wrong, why? It makes no sense for VirtualProtectEx to pass and not ReadProcessMemory when they both seem to have valid parameters. So maybe you accidentally entered the PID instead of getting correct access to the process (OpenProcess) then using the returned handle.

EDIT: Damn, appalsap beat me Sad

Thanks xor - thats actually what I had thought to start off with and that's why I was stumped. Of course I just wasn't looking at the obvious.
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