[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4FC91429.1050301@redhat.com>
Date: Fri, 01 Jun 2012 13:12:41 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: John Haxby <john.haxby@...cle.com>
Subject: Re: CVE Request -- kernel: tcp: drop SYN+FIN messages
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 06/01/2012 10:35 AM, John Haxby wrote:
> I am inclined to think that we should have a separate CVE for the
> kernel here. Unless I'm mistaken, a packet with SYN+FIN has no
> legitimate business being in the Internet any more than the old
> SYN+RST has. It's security hardening in that firewall rules to
> discard packets with odd combinations of flags are often deployed
> by people setting up "serious" firewalls but most machines out
> there, whether or not they have iptables set up, don't go to those
> lengths. Certainly none of the machines I have access to that have
> "out of the box" iptables configurations would appear to defend
> against SYN+FIN for open ports.
In my limited testing with iptables on RHEL 6.2 it appears that
- --state NEW works properly, and won't allow SYN+FIN to create
connections (I used hping3 and the SYN+FIN Packets were blocked).
So the default ruleset:
- -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
- -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j DROP
- -A INPUT -j REJECT --reject-with icmp-host-prohibited
should work, so you could do you clever --syn bits first and then have
that set to protect stuff from SYN+FIN.
- --
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/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=e4JD
-----END PGP SIGNATURE-----
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
