> 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 Tüxen [mailto:michael.tue...@lurchi.franken.de] 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 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 = sizeof(*p_random) + random_len + sizeof(*chunks) + 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 false > if peer SCTP does not require any chunk to be authenticated (this > 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 != NULL) { > ..... > } > > I think the calculated keylen should be something like this : > > keylen = sizeof(*p_random) + random_len + sizeof(*hmacs) + hmacs_len; > > if (chunks != NULL) { > keylen += sizeof(*chunks) + num_chunks } > > This problem results in authenticated packets sent from peer SCTP to > be discarded. > > The problem does not occurs if peer SCTP is modified to send an empty > Chunk List Parameter, (eg num_chunks = 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-unsubscr...@freebsd.org" > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
