Date: Thu, 31 Jan 2008 13:15:12 +0100 (CET) From: Ingo Flaschberger <if@xip.at> To: Andre Oppermann <andre@freebsd.org> Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, "Bruce M. Simpson" <bms@FreeBSD.org>, freebsd-net@freebsd.org Subject: Re: tcp-md5 check for incomming connection Message-ID: <alpine.LFD.1.00.0801311311010.4705@filebunker.xip.at> In-Reply-To: <47A19CC2.4070609@freebsd.org> References: <alpine.LFD.1.00.0801291905020.17757@filebunker.xip.at> <479FF09B.4050705@FreeBSD.org> <20080130083105.S36482@maildrop.int.zabbadoz.net> <alpine.LFD.1.00.0801310106400.723@filebunker.xip.at> <47A19CC2.4070609@freebsd.org>
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Dear Andre, >> 2) linux method: >> Look for CONFIG_TCP_MD5SIG in linux-2.6.24/net/ipv4/tcp_ipv4.c >> (sorry no weblink..) >> They check and block md5-packets early in tcp_v4_do_rcv. >> afinet.c -> tcp_v4_rcv -> tcp_v4_do_rcv >> -> for Freebsd: place some logic early in tcp_input function >> and call a new function to check md5. > > IMHO calling a special function that does the check (like in tcp_output) > is the way to go. This function should be run as late as possible after > the other segment validity checks to prevent easy cpu exhaustion attacks > with packets that only get the port numbers right. > > In tcp_new there is a natural place to perform the check. tcp_input will > show up this weekend. This doesn't prevent your work on the current code > at all as tcp_new won't show up in -current for a long time and when it > does it will not get MFC'd. Ok. I will do the first patch for freebsd 6.2 (as my system uses it) and do the a port to current (and I thing 6.3 too). Regardding Bruce: I would prefer to implement md5 via the old setkey api as I also have todo my daily business. >> 3) Bruce extended method: >> http://lists.freebsd.org/pipermail/freebsd-net/2004-April/003761.html >> Use his code and add at severall places in tcp_input function >> similar checks. >> >> Options: >> *) enable disable it via sysctl >> *) count total, good and bad packets via sysctl > > This belongs into struct tcpstat, not a new sysctl. Ok. With which tool can this counters be read? Should I add the on/off feature? Via which tool? Kind regards, Ingo
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