ESET NOD32 Antivirus DLL Hijacking
Posted on 23 December 2015
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_MACHINESOFTWAREMicrosoftWindowsCurrentVersionPoliciesSystem] "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
