------------------------------------------------------------------------ Title : False-negatives in several Vulnerability Assessment tools Released : April 7th 2003 Location : http://www.exaprobe.com/labs/advisories/esa-2003-0407.html ------------------------------------------------------------------------ General overview ================ Numerous Vulnerability Assessment (VA) tools are available for security engineers, pen-testers and network administrators. Their results are mostly trusted by users since they don't have time nor competences to validate that output. More and more softwares are currently implementing some banners and error messages that depend on the language. Especially for commercial softwares, like Microsoft SQL Server or the Windows operating system. Some VA tools don't integrate this localization feature and so generate false-negatives. It can thus lead to a false sense of security. Some exploit work on the English as well as on some non-English versions, it then constitutes a security breach. We chose to demonstrate those security exposures on Microsoft SQL Server with the "SQL Server blank password" vulnerability. Please note that this is not the only issue : - Some problems were found when VA tools began to detect the IIS/Unicode vulnerability, like the unicoder.pl script of HD Moore, which is looking for the localizable string "Directory of" [1]. - The admin account on Windows operating systems depends on the localization. On English-speaking versions, the name is "Administrator", whereas on French version (for example), it is "Administrateur". This leads to issues on brute-force attacks. A pratical example ================== Introduction ============ Microsoft SQL Server is a perfect choice to test VA tools about localization issues because it is widely deployed, it depends on the localization and it is vulnerable to some well-known security flaws. Testing conditions ================== First, we set up default installations of Microsoft SQL Server 2000 on Win2K SP3, in the following languages : - English - French - German - Japan The "sa" admin account was set with a blank password. We tested every VA tools from our panel on the English version looking for the vulnerability CAN-2000-1209 ("MS-SQL blank password"). Products which found this breach were then tested on the other languages. Tested VA tools =============== - ISS Database Scanner - Vigilante SecureScan NX - eEye Retina Network Scanner - eEye Spida Scanner (dedicated to find blank "sa" accounts) - Nessus - Sensepost senseql Untested (or untestable) VA tools ================================= - ISS Security Scanner (doesn't do this check) - Symantec NetRecon (doesn't do this check) - NetIQ (doesn't do this check) - GFI LANGuard (unreliable results) Results ======= +----------------------+-----------------+------------------+ | VA Tool | English version | Others languages | +----------------------+-----------------+------------------+ | ISS Database Scanner | OK | OK | +----------------------+-----------------+------------------+ | Vigilante Secure NX | OK | False-negative | +----------------------+-----------------+------------------+ | eEye Retina Scanner | OK | False-negative | +----------------------+-----------------+------------------+ | eEye Spida Scanner | OK | False-negative | +----------------------+-----------------+------------------+ | Nessus | OK | False-negative | +----------------------+-----------------+------------------+ | Sensepost senseql | OK | False-negative | +----------------------+-----------------+------------------+ Notes about the above results ============================= - The eEye Retina Scanner was tested on this point some time ago. Amazingly, it used to detect this vulnerability on non-English versions of Microsoft SQL Server. - Informal discussions with nCircle developpers conclude that their VA tool shouldn't be affected by this problem. - The exploit code nammed SQLpoke [2] (used in the Worm.SQLSpida.A malware [3]) succeeds to compromize every localized Microsoft SQL server. This implementation operates at the application level. Editors status ============== - Vigilante Secure NX : Work in progress on the editor side ... - eEye Retina Scanner : Work in progress on the editor side ... - Nessus : We provided the Nessus team with some patches which were integrated to the related plugins - Sensepost senseql : A new release is available at [4] Conclusion ========== In our opinion, it's now up to VA tools editors to take into account the localization issues when developping pattern matching signatures. Of course, security engineers and consultants should review every scan reports for false-positives. They should also run several tools in order to better detect false-negatives. A good way to avoid these problems would be to check vulnerabilies at an application level, like the SQLpoke exploit code. Credits ======= Nicolas Gregoire, security engineer - initial discovery of the MS-SQL localization bug - testing and redaction Philippe Conchonnet, security consultant - testing of Windows-based VA tools Christophe Briguet, technical manager - review of the document References ========== [1] : http://packetstormsecurity.org/NT/scanners/Sqlpoke.zip [2] : http://lists.insecure.org/lists/pen-test/2001/Jun/0128.html [3] : http://www.avp.ch/avpve/worms/sqlspida.stm [4] : http://www.exaprobe.com/labs/downloads/tools/senseql-1.1.tgz -- Nicolas Gregoire ----- Consultant en Sécurité des Systèmes d'Information ngregoireat_private ------[ ExaProbe ]------ http://www.exaprobe.com/ PGP KeyID:CA61B44F FingerPrint:1CC647FF1A55664BA2D2AFDACA6A21DACA61B44F top spam and e-mail risk at the gateway. 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