Date: Fri, 01 Jun 2012 09:36:09 +0100 From: John Haxby <john.haxby@...cle.com> To: Kurt Seifried <kseifried@...hat.com> CC: oss-security@...ts.openwall.com Subject: Re: CVE Request -- kernel: tcp: drop SYN+FIN messages -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 31/05/12 18:44, Kurt Seifried wrote: > To clarify: CVE-2012-2663 is for the --syn processing flaw of SYN+FIN > packets in iptables (user space tools). c > Also if people could test their firewalls to make sure this still > doesn't affect other operating systems that would probably be a good idea. It's not clear to me why you would want to allow SYN+FIN at all. So far as I have been able to discover t is only used for T/TCP which was obsoleted in May 2011 by RFC6247 which said this: > 4. Security Considerations > > As mentioned in [RFC4614], the TCP Extensions for Transactions > (T/TCP) [RFC1379][RFC1644] are reported to have security issues > [DEVIVO]. RFC4614 has this to say: > RFC 1379 I "Extending TCP for Transactions -- Concepts" (November > 1992): found defective > > See RFC 1644. > > RFC 1644 E "T/TCP -- TCP Extensions for Transactions Functional > Specification" (July 1994): found defective > > The inventors of TCP believed that cached connection state could > have been used to eliminate TCP's 3-way handshake, to support > two-packet request/response exchanges. RFCs 1379 [RFC1379] and > 1644 [RFC1644] show that this is far from simple. Furthermore, > T/TCP floundered on the ease of denial-of-service attacks that can > result. One idea pioneered by T/TCP lives on in RFC 2140, in the > sharing of state across connections. I'm not averse to this being an iptables problem, I just wondered why that is the case given the reasons for making T/TCP historic. jch -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iF4EAREIAAYFAk/IfvkACgkQRQu7fpQvo8h47wEAjQCY/RBRWng2hNe446T862+K TczzjV2WpkBeQ3DE/5cBAIiBL0y4fdBkojnGTRyWuDuN4Tl8L+SH98aNWT0mPtXo =hEGv -----END PGP SIGNATURE-----
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