[IronPython] Cast to a method pointer using CTYPES

Curt Hagenlocher curt at hagenlocher.org
Thu Feb 10 17:24:16 CET 2011


Strange that a search would find nothing. Try searching for VirtualProtect
instead -- that's what you'd need to mark a block of memory as executable,
and you'd use it in conjunction with VirtualAlloc.
On Thu, Feb 10, 2011 at 8:17 AM, Andrew Evans <evans.d.andrew at gmail.com>wrote:

> Mind showing showing me an example of using VirtualAlloc?
>
> Thanks for your help
>
> Quick Google Search reveals nothing Nothing to me on VirtualAlloc
>
> *cheers
>
>
>
> On Wed, Feb 9, 2011 at 12:37 PM, Dino Viehland <dinov at microsoft.com>wrote:
>
>>  So you want to generate the assembly in memory and then execute it?  I
>> think you want something like:
>>
>>
>>
>> import array
>>
>> myCode = array.array('b',
>> "\x31\xc0\x31\xdb\x31\xc9\x31\xd2\x51\x68\x6c\x6c\x20\x20\x68\x33")
>>
>> buffer = myCode.buffer_info()[0]
>>
>>
>>
>> from ctypes import *
>>
>> my_callback = CFUNCTYPE(c_int)
>>
>>
>>
>> my_callback(buffer)()
>>
>>
>>
>> This creates an array from your code, and then gets the address of that
>> array.  Then it creates a callback type which just returns an int, and then
>> it creates an instance of that callback type using the address of the code
>> and calls that instance (which then causes an access violation when I run
>> this).
>>
>>
>>
>> If you’re on a machine w/ the NX bit you may need to call VirtualAlloc and
>> copy the bytes to the allocated executable memory rather than using a
>> buffer.
>>
>>
>>
>> *From:* users-bounces at lists.ironpython.com [mailto:
>> users-bounces at lists.ironpython.com] *On Behalf Of *Andrew Evans
>> *Sent:* Wednesday, February 09, 2011 12:23 PM
>> *To:* Discussion of IronPython
>> *Subject:* Re: [IronPython] Cast to a method pointer using CTYPES
>>
>>
>>
>> Hey thank you for the fast reply :-)
>>
>> I am working on building a security framework in Python for exploit
>> development as a part time hobby. But I am missing something key to what I
>> am doing. I am having a hard time understanding it as well.
>>
>> from ctypes import *
>>
>> myCode = ("\x31\xc0\x31\xdb\x31\xc9\x31\xd2"
>>     "\x51\x68\x6c\x6c\x20\x20\x68\x33") #example hex not full for post
>> don't want to put up red flags
>>
>> my_callback = CFUNCTYPE(c_int, c_void_p,
>>                         POINTER(myCode),
>>                         POINTER(c_int32), c_void_p)
>>
>> print type(my_callback)
>>
>> this returns <type '_ctypes.PyCFuncPtrType'> which is what I want I
>> assume.
>>
>> but when I run this code nothing happens. Maybe in how I am running it
>> just by adding my_callback to the source. Any idea what I am doing wrong.
>>
>> *cheers in advance if you can help
>>
>> If not I understand
>>
>>
>> _______________________________________________
>> Users mailing list
>> Users at lists.ironpython.com
>> http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
>>
>>
>
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