Date: Fri, 30 Jan 2009 01:37:49 +0000 From: "Muggeridge, Matt" <Matt.Muggeridge@hp.com> To: =?iso-8859-1?Q?=27Michael_T=FCxen=27?= <Michael.Tuexen@lurchi.franken.de>, Yann WANWANSCAPPEL <yann.wanwanscappel@free.fr> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: RE: SCTP, possible bug in peer authentication key Message-ID: <DAE8EEF9700DC84CB97414D6CF6FCA713E79BEC1EF@GVW1160EXB.americas.hpqcorp.net> In-Reply-To: <A36412A3-53FA-4738-A875-8DFB78C8FE58@lurchi.franken.de> References: <4980B747.7070400@free.fr> <A36412A3-53FA-4738-A875-8DFB78C8FE58@lurchi.franken.de>
next in thread | previous in thread | raw e-mail | index | archive | help
> I think I found a bug in the SCTP authentication code, in > sctp_load_addresses_from_init() in sctp_pcb.c I noticed the same calculation appears in sctp_auth.c:sctp_auth_get_cookie_= params(). Does this fix also need to be applied there? Cheers, Matt. -----Original Message----- From: Michael T=FCxen [mailto:Michael.Tuexen@lurchi.franken.de]=20 Sent: Thursday, 29 January 2009 6:23 PM To: Yann WANWANSCAPPEL Cc: freebsd-net@freebsd.org Subject: Re: SCTP, possible bug in peer authentication key Hi Yann, very good catch! You are right. I have committed your patch to Randalls repository, so it will show up in t= he 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) + num_chunks= =20 > + > sizeof(*hmacs) + hmacs_len; > > The keylen calculation assumes the Chunk List Parameter (CHUNKS)=20 > vl-param was present in the received INIT packet, which can be false=20 > if peer SCTP does not require any chunk to be authenticated (this=20 > typically occurs if peer does not support ASCONF). > >> From 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 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 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) + hmacs_len; > > if (chunks !=3D NULL) { > keylen +=3D sizeof(*chunks) + num_chunks } > > This problem results in authenticated packets sent from peer SCTP to=20 > be discarded. > > The problem does not occurs if peer SCTP is modified to send an empty=20 > 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" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?DAE8EEF9700DC84CB97414D6CF6FCA713E79BEC1EF>