SumatraPDF 3.1.2 DLL Hijacking
Posted on 09 February 2017
Hi @ll, the executable installer [deg] and the "portable" version of SumatraPDF 3.1.2 (available from <https://www.sumatrapdfreader.org/download-free-pdf-viewer.html>) are vulnerable to DLL hijacking [']: The executable installers SumatraPDF-3.1.2-install.exe and SumatraPDF-3.1.2-64-install.exe load and execute (tested on a fully patched Windows 7 SP1) at least Version.dll, OLEACC.dll, CryptBase.dll, NTMARTA.dll, LinkInfo.dll, NTSHRUI.dll, NetUtils.dll, SrvCli.dll, CSCAPI.dll, SLC.dll, PropSys.dll from the directory they are started from (the "application directory") instead Windows "system directory", resulting in arbitrary code execution. For software downloaded with a web browser the "application directory" is typically the user's "Downloads" directory: see <http://seclists.org/fulldisclosure/2015/Nov/101> and <http://seclists.org/fulldisclosure/2015/Dec/86> plus <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> Due to an application manifest embedded in the executable installer which specifies "requireAdministrator" it will be started with administrative privileges ("protected" administrators are prompted for consent, unprivileged standard users are prompted for an administrator password), resulting in an escalation of privilege! If (one of) the DLLs named above get(s) planted in the users "Downloads" directory, for example per "drive-by download", this vulnerability becomes a remote code execution WITH escalation of privilege. Proof of concept/demonstration: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1. visit <https://skanthak.homepage.t-online.de/sentinel.html>, download <https://skanthak.homepage.t-online.de/skanthak/download/SENTINEL.DLL> and save it as Version.dll in your "Downloads" directory, then copy it as OLEACC.dll, CryptBase.dll, NTMARTA.dll, LinkInfo.dll, NTSHRUI.dll, NetUtils.dll, SrvCli.dll, CSCAPI.dll, SLC.dll and PropSys.dll; 2. visit <https://www.sumatrapdfreader.org/free-pdf-reader.html>, download <https://kjkpub.s3.amazonaws.com/sumatrapdf/rel/SumatraPDF-3.1.2-install.exe> and save it in your "Downloads" directory; 3. execute SumatraPDF-3.1.2-install.exe from your "Downloads" directory; 4. notice the message boxes displayed from the DLLs placed in step 1: PWNED! The "portable" SumatraPDF.exe version 3.1.2 loads and executes at least (tested on a fully patched Windows 7 SP1) WinSpool.drv, MSImg32.dll, Version.dll, OLEAcc.dll, WindowsCodecs.dll, AppHelp.dll, SrvCli.dll, CSCAPI.dll, SLC.dll, MSFTEdit.dll, MSLS31.dll, NTMARTA.dll, XMLLite.dll, LinkInfo.dll, CryptSp.dll, RPCRTRemote.dll, ShDocVw.dll, IEFrame.dll, MPR.dll, SAMCli.dll, SAMLib.dll, WksCli.dll, NetUtils.dll and WinMM.dll from its "application directory" (which is typically writable by the user) instead Windows' "system directory", resulting in arbitrary code execution. Mitigation(s): ~~~~~~~~~~~~~~ 0. DON'T USE EXECUTABLE INSTALLERS [deg]! DON'T USE PORTABLE APPLICATIONS! 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 <https://skanthak.homepage.t-online.de/SAFER.html> as well as <http://www.mechbgon.com/srp/index.html>. stay tuned Stefan Kanthak [deg] Self-extracting archives and executable installers are flawed^W b(rainde)ad in concept and dangerous in practice: see <https://skanthak.homepage.t-online.de/!execute.html> ['] A well-known (trivial, easy to exploit and easy to avoid) and well-documented vulnerability: 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> Timeline: ~~~~~~~~~ 2017-01-21 sent vulnerability report regarding the installer to author NO ANSWER, not even an acknowledgement of receipt 2017-01-24 sent vulnerability report regarding the "portable" version to author NO ANSWER, not even an acknowledgement of receipt 2017-01-28 resent first vulnerability report to author NO ANSWER, not even an acknowledgement of receipt 2017-01-31 resent second vulnerability report to author NO ANSWER, not even an acknowledgement of receipt 2017-02-07 report published
