From owner-freebsd-net@FreeBSD.ORG Thu Jan 29 18:34:18 2009 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6418A1065670 for ; Thu, 29 Jan 2009 18:34:18 +0000 (UTC) (envelope-from Michael.Tuexen@lurchi.franken.de) Received: from mail-n.franken.de (drew.ipv6.franken.de [IPv6:2001:638:a02:a001:20e:cff:fe4a:feaa]) by mx1.freebsd.org (Postfix) with ESMTP id BCAD48FC2C for ; Thu, 29 Jan 2009 18:34:17 +0000 (UTC) (envelope-from Michael.Tuexen@lurchi.franken.de) Received: from [IPv6:2002:508f:f424::21e:52ff:fe71:c926] (unknown [IPv6:2002:508f:f424:0:21e:52ff:fe71:c926]) by mail-n.franken.de (Postfix) with ESMTP id DF07B1C0B462F; Thu, 29 Jan 2009 19:34:15 +0100 (CET) Message-Id: <47807A97-0CD3-4E7A-A659-00139086B97F@lurchi.franken.de> From: =?ISO-8859-1?Q?Michael_T=FCxen?= To: Peter Lei In-Reply-To: <0EEEB325-C7AF-468F-9374-EFED1BD3B3E4@ieee.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed; delsp=yes Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Apple Message framework v930.3) Date: Thu, 29 Jan 2009 19:34:14 +0100 References: <4980B747.7070400@free.fr> <0EEEB325-C7AF-468F-9374-EFED1BD3B3E4@ieee.org> X-Mailer: Apple Mail (2.930.3) Cc: freebsd-net@freebsd.org, Yann WANWANSCAPPEL Subject: Re: SCTP, possible bug in peer authentication key X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Jan 2009 18:34:19 -0000 Hi Peter, good catch! Best regards Michael On Jan 29, 2009, at 6:29 PM, Peter Lei wrote: > There's a corresponding change that is needed for pulling the auth =20 > info > out of the cookie for the other direction (i.e. server side =20 > handling). I've > committed that into the SCTP project repo, and should also get in with > Randall's next commit. > > --peter > > On Jan 29, 2009, at 2:23 AM, Michael T=FCxen wrote: > >> Hi Yann, >> >> very good catch! You are right. >> >> I have committed your patch to Randalls repository, so it will >> show up in the FreeBSD sources soon (next time he syncs them)... >> >> Best regards >> Michael >> >> On Jan 28, 2009, at 8:51 PM, Yann WANWANSCAPPEL wrote: >> >>> Hi all, >>> >>> I think I found a bug in the SCTP authentication code, in >>> sctp_load_addresses_from_init() in sctp_pcb.c >>> >>> keylen =3D sizeof(*p_random) + random_len + sizeof(*chunks) + =20 >>> num_chunks + >>> sizeof(*hmacs) + hmacs_len; >>> >>> The keylen calculation assumes the Chunk List Parameter (CHUNKS) >>> vl-param was present in the received INIT packet, which can be =20 >>> false if >>> peer SCTP does not require any chunk to be authenticated (this =20 >>> typically >>> occurs if peer does not support ASCONF). >>> >>>> =46rom RFC 4895, 6.1 >>> >>> * An SCTP endpoint has a list of chunks it only accepts if they are >>> * received in an authenticated way. This list is included in the =20= >>> INIT >>> * and INIT-ACK, and MAY be omitted if it is empty. Since this list >>> * does not change during the lifetime of the SCTP endpoint there =20 >>> is no >>> * problem in case of INIT collision. >>> >>> This case is properly handled later in the build of the key >>> >>> /* append in the AUTH chunks */ >>> if (chunks !=3D NULL) { >>> ..... >>> } >>> >>> I think the calculated keylen should be something like this : >>> >>> keylen =3D sizeof(*p_random) + random_len + sizeof(*hmacs) + =20 >>> hmacs_len; >>> >>> if (chunks !=3D NULL) { >>> keylen +=3D sizeof(*chunks) + num_chunks >>> } >>> >>> This problem results in authenticated packets sent from peer SCTP =20= >>> to be >>> discarded. >>> >>> The problem does not occurs if peer SCTP is modified to send an =20 >>> empty >>> Chunk List Parameter, (eg num_chunks =3D 0 in the decoding). >>> >>> Br, >>> Yann >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> _______________________________________________ >>> freebsd-net@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-net >>> To unsubscribe, send any mail to = "freebsd-net-unsubscribe@freebsd.org=20 >>> " >>> >> >> _______________________________________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to "freebsd-net-=20 >> unsubscribe@freebsd.org" >