________________________________________________________________________ From the low-hanging-fruit-department F-prot generic evasion (TAR) ________________________________________________________________________ CHEAP Plug : ************ You are invited to participate in HACK.LU 2009, a small but concentrated luxemburgish security conference. More information : http://www.hack.lu CFP is open, sponsorship is still possible and warmly welcomed! ************ Release mode: Coordinated but limited disclosure. Ref : [TZO-33-2009] - F-prot TAR bypass / evasion WWW : http://blog.zoller.lu/2009/06/advisory-frisk-f-prot-evasion-tar.html Vendor : http://www.f-prot.com Status : Current version not patched, next engine version will be patched CVE : none provided Credit : Given in the History file OSVDB vendor entry: none [1] Security notification reaction rating : better than last time Notification to patch window : n+1 (no patch for current build) Disclosure Policy : http://blog.zoller.lu/2008/09/notification-and-disclosure-policy.html Affected products (all versions up to 4.5.0 which is not released yet) - F-PROT AVES (High: complete bypass of engine) - F-PROT Antivirus for Windows (unknown) - F-PROT Antivirus for Windows on Mail Servers : (High: complete bypass of engine) - F-PROT Antivirus for Exchange (High: complete bypass of engine) - F-PROT Antivirus for Linux x86 Mail Servers : (High: complete bypass of engine) - F-PROT Antivirus for Linux x86 File Servers : (High: complete bypass of engine) - F-PROT Antivirus for Solaris SPARC / Solaris x86 Mail Servers (High: complete bypass of engine) - F-PROT Milter - for example sendmail (High: complete bypass of engine) - F-PROT Antivirus for Linux on IBM zSeries (S/390) (High: complete bypass of engine) - F-Prot Antivirus for Linux x86 Workstations (unknown) OEM Partners affected : - Autentium (all versions) OEM Partners with unknown status : - Sendmail, Inc. - G-Data I. Background ~~~~~~~~~~~~~ Quote: "FRISK Software International, established in 1993, is one of the world's leading companies in antivirus research and product development. FRISK Software produces the hugely popular F-Prot Antivirus products range offering unrivalled heuristic detection capabilities. In addition to this, the F-Prot AVES managed online e-mail security service filters away the nuisance of spam e-mail as well as viruses, worms and other malware that increasingly clog up inboxes and threaten data security." II. Description ~~~~~~~~~~~~~~~ The parsing engine can be bypassed by a specially crafted and formated TAR archive. III. Impact ~~~~~~~~~~~ A general description of the impact and nature of AV Bypasses/evasions can be read at : http://blog.zoller.lu/2009/04/case-for-av-bypassesevasions.html The bug results in denying the engine the possibility to inspect code within TAR archives. There is no inspection of the content at all and hence the impossibility to detect malicious code. IV. Disclosure timeline ~~~~~~~~~~~~~~~~~~~~~~~~~ DD/MM/YYYY 28/04/2009 : Send proof of concept, description the terms under which I cooperate and the planned disclosure date. No reply 11/05/2009 : Resending PoC file asking to please reply 20/05/2009 : Frisk replies that it was unable to extract the PoC file with "tar" and hence see no bypass. 20/05/2009 : Inform Frisk that the PoC extracts fine with Winzip 22/05/2009 : Frisk send a lenghty e-mail re-discussing bypasses/evasions 22/05/2009 : I state that I will not discuss this topic any further, everything has been said and written multiple times. Either Frisk patches or they do not. 22/05/2009 : Frisk states that the changes to the parsing code are minor i.e not relying on the checksum. The patch will be included in the next releaes candidate 4.5.0 and credit will be given in the History file Comment: I give it some time to 4.5.0 to be released. 10/06/2009 : Ask Frisk if 4.5.0 has been released now no reply 14/06/2009 : Release of this advisory [1] F-prot is encouraged to leave their security contact details at http://osvdb.org/vendor/1/Frisk%20Software%20International to facilate communication and reduce lost reports.