ESET NOD32 Antivirus DLL Hijacking

2015-12-21T00:00:00
ID PACKETSTORM:135022
Type packetstorm
Reporter Stefan Kanthak
Modified 2015-12-21T00:00:00

Description

                                        
                                            `Hi @ll,  
  
the executable installer [°] of ESET's NOD32 antivirus,  
eset_nod32_antivirus_live_installer_.exe, loads and executes  
(at least) the rogue/bogus/malicious Cabinet.dll and DbgHelp.dll  
eventually found in the directory it is started from ['] (the  
"application directory").  
  
For software downloaded with a web browser this is typically the  
"Downloads" directory: 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>  
and <http://seclists.org/fulldisclosure/2012/Aug/134>  
  
If Cabinet.dll or DbgHelp.dll get planted in the users "Downloads"  
directory per "drive-by download" (or "social engineering") this  
vulnerability becomes a remote code execution.  
  
Due to the application manifest embedded in the executable which  
specifies "requireAdministrator" the installer is started with  
administrative privileges ("protected" administrators are prompted  
for consent, unprivileged standard users are prompted for an  
administrator password); execution of Cabinet.dll or DbgHelp.dll  
then results in an escalation of privilege!  
  
  
Proof of concept/demonstration:  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
(verified on Windows XP, Windows Vista, Windows 7, Windows Server  
2008 [R2]; should work on newer versions too)  
  
1. visit <http://home.arcor.de/skanthak/sentinel.html>, download  
<http://home.arcor.de/skanthak/download/SENTINEL.DLL> and store  
it as Cabinet.dll in your "Downloads" directory, then copy it as  
DbgHelp.dll;  
  
2. download eset_nod32_antivirus_live_installer_.exe and store it in  
your "Downloads" directory;  
  
3. run eset_nod32_antivirus_live_installer_.exe from your "Downloads"  
directory;  
  
4. notice the message boxes displayed from the DLLs placed in step 1.  
  
PWNED!  
  
  
Unsuspecting users who follow the guidance on ESET's web site  
<http://www.eset.com/int/download/thank-you-eset-nod32-antivirus/file/13934/>  
  
| (1) Download the .exe file to your computer and double-click  
| it to start installation.  
  
are the typical victims!  
  
JFTR: I REALLY love (especially snakeoil) companies which don't  
protect or at least warn their customers from even the most  
trivial handling errors!  
  
  
See <http://seclists.org/fulldisclosure/2015/Nov/101> plus  
<http://home.arcor.de/skanthak/sentinel.html> and the still unfinished  
<http://home.arcor.de/skanthak/!execute.html> for more details and why  
executable installers (and self-extractors too) are bad.  
  
  
Mitigation(s):  
~~~~~~~~~~~~~~  
  
0. DON'T USE EXECUTABLE INSTALLERS [°]!  
  
If your favourite applications are not distributed in the native  
installer package format of the resp. target platform: ask^WURGE  
their vendors/developers to provide native installation packages.  
If they don't: dump these applications, stay away from such cruft!  
  
1. Turn off UAC's privilege elevation for standard users and installer  
detection for all users:  
  
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]  
"ConsentPromptBehaviorUser"=dword:00000000 ; Automatically deny elevation requests  
"EnableInstallerDetection"=dword:00000000  
  
See <https://technet.microsoft.com/en-us/library/dd835564.aspx#BKMK_RegistryKeys>  
  
2. NEVER execute files in UNSAFE directories (like "Downloads" and  
and "%TEMP%")!  
  
3. Deny execution (at least) in the "Downloads" directories and all  
"%TEMP%" directories and their subdirectories:  
  
* Add the NTFS ACE "(D;OIIO;WP;;;WD)" meaning "deny execution of  
files in this directory for everyone, inheritable to all files  
in all subdirectories" (use CACLS.EXE /S:<SDDL> for example);  
  
* Use "software restriction policies" resp. AppLocker.  
  
Consider to apply either/both to every "%USERPROFILE%" as well as  
"%ALLUSERSPROFILE%" alias %ProgramData%" and "%PUBLIC%": Windows  
doesn't place executables in these directories and beyond.  
  
See <http://home.arcor.de/skanthak/safer.html> as well as  
<http://mechbgon.com/srp/> plus  
<http://csrc.nist.gov/itsec/SP800-68r1.pdf>,  
<https://www.nsa.gov/ia/_files/os/win2k/application_whitelisting_using_srp.pdf>  
or <https://books.google.de/books?isbn=1437914926> and finally  
<http://www.asd.gov.au/infosec/top35mitigationstrategies.htm>!  
  
  
stay tuned  
Stefan Kanthak  
  
  
[°] Self-extracting archives and executable installers are flawed^W  
b(rainde)ad in concept and dangerous in practice.  
  
DON'T USE SUCH CRUFT!  
ALWAYS use the resp. target platforms native package and archive  
format.  
  
For Windows these are .INF (plus .CAB) and .MSI (plus .CAB),  
introduced 20 years ago (with Windows 95 and Windows NT4) resp.  
16 years ago (with Office 2000).  
  
Both .INF and .MSI are "opened" by programs residing in  
%SystemRoot%\System32\ which are therefore immune to this kind  
of "DLL and EXE Search Order Hijacking" attack.  
Since both .INF and .MSI access the contents of .CAB directly  
they eliminate the attack vector "unsafe temporary directory"  
too.  
  
['] A well-known and well-documented (trivial, easy to exploit and  
easy to avoid) vulnerability: see  
<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>  
  
  
Timeline:  
~~~~~~~~~  
  
2015-11-30 report sent to vendor  
  
NO answer, not even an acknowledgement of receipt  
  
2015-12-12 report resent to vendor  
  
NO answer, not even an acknowledgement of receipt  
  
2015-12-21 report published  
`