[solved] Odd issue with 64-bit MSVCRT printf invocation

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Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 27 Mar 2017, 06:27

I've got a heisenbug on my hands. The following works on my Win7 machine and my debugger without problems, but fails on Win10.

Code:

format PE64 console
entry start

    include "win64a.inc"

section '.text' code readable executable
    
    start:
        invoke printf, msg_helloWorld
        invoke ExitProcess, 0
        
    msg_test db "Test", 0x0D, 0x0A, 0
    
section '.data' data readable

    msg_helloWorld db "Hello world!", 0x0D, 0x0A, 0
    
section '.idata' import data readable writeable

    library kernel32,'KERNEL32.DLL',\
            msvcrt, 'MSVCRT.DLL'
    
    include 'api/kernel32.inc'
    
    import  msvcrt,\
            printf, 'printf'

Any ideas? inb4 Windows 10? More like WinBLOWS 10 am I rite???

27 Mar 2017, 06:27

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20423
Location: In your JS exploiting you and your system

revolution 27 Mar 2017, 06:38

What do you mean by "fails on Win10"? Crashes? Prints something else? Prints nothing? Infinite loop? Can't start? Can't debug?

27 Mar 2017, 06:38

Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 27 Mar 2017, 06:44

revolution wrote:

What do you mean by "fails on Win10"? Crashes? Prints something else? Prints nothing? Infinite loop? Can't start? Can't debug?

It crashes and burns. "ConsoleTest.exe has stopped working."

27 Mar 2017, 06:44

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20423
Location: In your JS exploiting you and your system

revolution 27 Mar 2017, 06:50

Probably because the stack is misaligned.

Try inserting this after the start label:

Code:

and rsp,-16

27 Mar 2017, 06:50

Trinitek

Joined: 06 Nov 2011
Posts: 257

Trinitek 27 Mar 2017, 06:55

Stupid stack alignments. Thanks a bunch.

27 Mar 2017, 06:55

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