Date: Wed, 28 Jun 2017 17:25:35 +0200
From: "Stefan Kanthak" <stefan.kanthak@...go.de>
To: <fulldisclosure@...lists.org>
Cc: bugtraq@...urityfocus.com
Subject: [FD] Executable installers are vulnerable^WEVIL (case 52):
	escalation of privilege with Microsoft's .NET Framework installers

Hi @ll,

the executable installers for .NET Framework 4.7 (released about
2 months ago)

* NDP47-KB3186500-Web.exe,
  Microsoft .NET Framework 4.7 (Web Installer) for Windows 7 SP1 etc.,
  available from <https://www.microsoft.com/en-us/download/details.aspx?id=55170>,

* NDP47-KB3186497-x86-x64-AllOS-ENU.exe,
  Microsoft .NET Framework 4.7 (Offline Installer) for Windows 7 SP1 etc.,
  available from <https://www.microsoft.com/en-us/download/details.aspx?id=55167>,

* NDP47-KB3186497-x86-x64-AllOS-DEU.exe,
  Microsoft .NET Framework 4.7 Sprachpaket (Offlineinstaller) für Windows 7 SP1 etc,
  available from <https://www.microsoft.com/de-de/download/details.aspx?id=55169>,

* NDP47-DevPack-KB3186612-ENU.exe,
  Microsoft .NET Framework 4.7 Developer Pack and Language Packs for Windows 7 SP1 etc.,
  available from <https://www.microsoft.com/en-US/download/details.aspx?id=55168>,

are vulnerable: they allow arbitrary code execution via DLL hijacking,
resulting in escalation of privilege.

On a fully patched Windows 7 SP1 (which has a market share around 50%)
NDP47-KB3186500-Web.exe, NDP47-KB3186497-x86-x64-AllOS-ENU.exe and
ALL language packs NDP47-KB3186497-x86-x64-AllOS-???.exe load at
least the following DLLs from their application directory (typically
%USERPROFILE%\Downloads\) instead Windows' system directory
%SystemRoot%\System32\ and execute their DllMain() routine:
    Cabinet.dll, Version.dll, CryptDll.dll, CryptSP.dll, NTMARTA.dll,
    UXTheme.dll, DWMAPI.dll

NDP47-DevPack-KB3186612-ENU.exe loads least the following DLLs from its
application directory (typically %USERPROFILE%\Downloads\) instead
Windows' system directory %SystemRoot%\System32\ and executes their
DllMain() routine:
    Cabinet.dll, MSI.dll, Version.dll, SPP.dll, VSSAPI.dll, ATL.dll,
    VSSTrace.dll, NTMARTA.dll, UXTheme.dll, DWMAPI.dll, CryptSP.dll,
    RPCRTRemote.dll


See <https://cwe.mitre.org/data/definitions/426.html>,
<https://cwe.mitre.org/data/definitions/427.html>
<https://capec.mitre.org/data/definitions/471.html>,
<https://technet.microsoft.com/en-us/library/2269637.aspx>,
<https://msdn.microsoft.com/en-us/library/ff919712.aspx> and
<https://msdn.microsoft.com/en-us/library/ms682586.aspx> for this
well-known beginner's error.


See <https://insights.sei.cmu.edu/cert/2008/09/carpet-bombing-and-directory-poisoning.html>,
<http://blog.acrossecurity.com/2012/02/downloads-folder-binary-planting.html>,
<http://seclists.org/fulldisclosure/2012/Aug/134> and
<http://blogs.technet.com/b/srd/archive/2014/05/13/load-library-safely.aspx>
for more information.

JFTR: it's a shame that these installers, built 2017-04-22, still
      show this 20+ year old beginner's error!


For NDP47-KB3186500-Web.exe and NDP47-KB3186497-x86-x64-AllOS-???.exe
this results thanks to their embedded application manifest which
specifies "requireAdministrator" in escalation of privilege.

NDP47-DevPack-KB3186612-ENU.exe achieves the escalation of privilege
with a call of itself via "RunAs".




Proof of concept/demonstration:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. download <https://skanthak.homepage.t-online.de/download/SENTINEL.DLL>
   and save it as UXTheme.dll in your "Downloads" directory;

2. copy the downloaded UXTheme.dll as Version.dll, Cabinet.dll etc.
   (see the list of DLL names above);

3. download
   <https://download.microsoft.com/download/A/E/A/AEAE0F3F-96E9-4711-AADA-5E35EF902306/NDP47-KB3186500-Web.exe>,
   <https://download.microsoft.com/download/D/D/3/DD35CC25-6E9C-484B-A746-C5BE0C923290/NDP47-KB3186497-x86-x64-AllOS-ENU.exe>,
   <https://download.microsoft.com/download/8/3/8/838A8A52-67BA-4F1C-BA95-FABBA994352C/NDP47-KB3186497-x86-x64-AllOS-DEU.exe>,
   ...,
   <https://download.microsoft.com/download/A/1/D/A1D07600-6915-4CB8-A931-9A980EF47BB7/NDP47-DevPack-KB3186612-ENU.exe>,
   and save them in your "Downloads" directory;

4. run the downloaded NDP47-*.exe and notice the message boxes displayed
   from the DLLs: PWNED!


Mitigation & detection:
~~~~~~~~~~~~~~~~~~~~~~~

* NEVER run executable installers from your "Downloads" directory;

* dump/avoid executable installers, use *.MSI instead!

* stay FAR away from software written by sloppy coders who don't
  know their target platform, and ignore their own companies
  guidelines/recommendations!

* see <https://support.microsoft.com/en-us/kb/2533623>,
  <https://technet.microsoft.com/en-us/security/2269637> and
  <https://blogs.technet.com/b/srd/archive/2014/05/13/load-library-safely.aspx>

* also see <https://skanthak.homepage.t-online.de/verifier.html>
  and <https://skanthak.homepage.t-online.de/!execute.html>

* dump .NET Framework alltogether!


stay tuned
Stefan Kanthak


Timeline:
~~~~~~~~~

2017-06-13    vulnerability report sent to vendor

2017-06-13    reply from vendor:
              "MSRC case 39179 opened"

2017-06-21    reply from vendor:
              "We have investigated the issue and determined it does not
               warrant an explicit fix for down level products. [...]
               Loading binaries from the application directory is a by
               design functionality of the Windows library search order
               process."

2017-06-21    OUCH!
              The "application directory" can be removed from the library
              search path since Windows Vista and the update KB2533623!
              See <https://msdn.microsoft.com/en-us/library/hh310515.aspx>
              or <https://msdn.microsoft.com/en-us/library/ms684179.aspx>.
              Which DLLs do the installers need or expect to load from
              their "application directory"?

2017-06-28    no reply from vendor since 7 days, report published


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