Date: Sun, 5 Sep 2010 21:47:00 -0700 From: Valient Gough <valient@...il.com> To: oss-security <oss-security@...ts.openwall.com> Cc: "Steven M. Christey" <coley@...us.mitre.org>, Micha Riser <micha@...world.org> Subject: Re: CVE Request -- EncFS / fuse-encfs [three ids] -- Multiple Vulnerabilities in EncFS On Sep 5, 2010, at 11:33 AM, Jan Lieskovsky wrote: > Hello Steve, vendors, > > Micha Riser reported: > [A] http://archives.neohapsis.com/archives/fulldisclosure/2010-08/0316.html > > three security flaws in EncFS encrypted filesystem (more from [A]): > > "A security analysis of EncFS has revealed multiple vulnerabilities: > (1) Only 32 bit of file IV used > (2) Watermarking attack > (3) Last block with single byte is insecure" > > References: > [B] http://www.arg0.net/encfs > [C] http://bugs.gentoo.org/show_bug.cgi?id=335938 > [D] http://archives.neohapsis.com/archives/fulldisclosure/2010-08/att-0316/watermark-attack-encfs.tar.gz > [E] https://bugzilla.redhat.com/show_bug.cgi?id=630460 > > > Solutions / patches information: > ================================ > > * for issue (1) -- seems it wasn't fixed / isn't possible to > fix without breaking backward compatibility. More from [B]: > > "The old IV setup is kept for backwards compatibility." > > * for issue (2) -- EncFS upstream has released a fix for the issue: > [F] http://code.google.com/p/encfs/source/detail?r=59 > > Valient, could you please confirm, the above referenced [F] patch, > is the correct one to address the watermarking attack issue? > > * for issue (3) -- not sure about patch status (included in [F] too?) > Jan, Yes, the patch referenced in [F], specifically changes to SSL_Cipher.cpp, were made in response to issues (1) & (2). These are not backward compatible, and so only apply to new filesystems. Issue (3) is not directly addressed. A workaround is to enable per-block MAC headers, or per-block random bytes. A patch going into 1.7.2 allows per-block random bytes to be configured independently of MAC headers. It would be possible to change the default settings such that per-block random bytes are always used. Adding new encryption modes is not planned for encfs 1.x. regards, Valient
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