Re: Encoder PexFnstenvSub

[Pedro Drimel <pedrodrimel () gmail com>]

It is actually a badchars issue. I compared the output I had with the
one generated with 2.7 version and it's different. Probably, in the
past I had to deal with badchars but don't remember what I did.

Tried to run into my buffer the following:

string = 
("\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e"
"\x1f\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d"
"\x3e\x3f\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c"
"\x5d\x5e\x5f\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b"
"\x7c\x7d\x7e\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a"
"\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9"
"\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8"
"\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7"
"\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff")

Put a breakpoint into the memory address which performs a JMP ESP but
it didn't work, if I just put some NOPs or a calc.exe it works.

Thanks in advance.

Regards,

Pedro.

2009/11/23 HD Moore <hdm () metasploit com>:
> On Mon, 2009-11-23 at 12:18 -0200, Pedro Drimel wrote:
> > Hello everyone,
> >
> > I used to use metasploit:55555 to generate payloads however the
> > servers seems to be offline. I would like through command like
> > msfpayload the same encoder as "PexFnstenvSub", I think it is
> > x86/fnstenv_mov but didn't work as the another one.
> >
> > What is the encoder PexFnstenvSub?
>
> The metasploit:55555 server is just msfweb from Metasploit 2.7, you can
> download and run it yourself if you like, but there are really good
> reasons for it being offline:
>
>
> 1) The payloads do not work on newer versions of Windows
> 2) The payloads do not work with newer CPUs with NX support
> 3) The payloads have since been improved (reliability) and shrunk
>
> The supported way is msfpayload with msfencode, the "pexfnstenvsub"
> encode was not directly ported, but x86/fnstenv_mov is pretty close to
> it. In most cases you do not need to set the encoder, just set the bad
> character list in msfencode (-b '\x00'). If x86/fnstenv_mov is not
> working, please file a bug.
>
> -HD
>
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