From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH net] net: sctp: inherit auth_capable on INIT collisions Date: Sat, 19 Jul 2014 01:03:20 +0200 Message-ID: <53C9A7B8.1020504@redhat.com> References: <1405620319-2021-1-git-send-email-dborkman@redhat.com> <53C93157.1050002@gmail.com> <53C972BE.5090700@redhat.com> <53C998DE.2030805@gmail.com> <53C99BEF.1010203@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, jgunthorpe@obsidianresearch.com, netdev@vger.kernel.org, linux-sctp@vger.kernel.org To: Vlad Yasevich Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58762 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762484AbaGRXDc (ORCPT ); Fri, 18 Jul 2014 19:03:32 -0400 In-Reply-To: <53C99BEF.1010203@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 07/19/2014 12:13 AM, Daniel Borkmann wrote: > On 07/18/2014 11:59 PM, Vlad Yasevich wrote: >> On 07/18/2014 03:17 PM, Daniel Borkmann wrote: >>> On 07/18/2014 04:38 PM, Vlad Yasevich wrote: >>> ... >>>> Why is the original value of asoc->peer.auth_capable = 0? >>>> In case of collision, asoc is the old association that >>>> existed on the system. That association was created as part of >>>> sending the INIT. If it is processing a duplicate COOKIE-ECHO >>>> as you say, then it has already processed the INIT-ACK and >>>> should have determined that the peer is auth capable. >>>> >>>> Thus the capability of the new and the old associations should >>>> be same if we are in fact processing case B (collision). What I can see is the following that leads to this situation: 1) asoc A sends the INIT, goes from CLOSED into COOKIE_WAIT 2) asoc B receives it, calls into sctp_sf_do_5_1B_init() where it actually creates asoc B, responds with INIT_ACK, goes from CLOSED into COOKIE_WAIT 3) asoc A receives INIT, thus collision, calls into sctp_sf_do_5_2_1_siminit() 3.1) asoc A calls into sctp_sf_do_unexpected_init(), creates a temp asoc, does sctp_process_init() on the temp asoc (auth_cap=1, random etc set), replies w/ temp asoc with INIT_ACK 4) asoc B gets INIT_ACK, calls sctp_sf_do_5_1C_ack (and thus SCTP_PEER_INIT via interpreter), sees auth_cap=1, stores random etc; asoc B transitions from COOKIE_WAIT into COOKIE_ECHOED 5) asoc A calls into sctp_sf_do_5_2_4_dupcook(), does the tietag compare, finds action B, creates temp asoc calls sctp_process_init() on it sees auth_cap=1, random etc; then we call into sctp_assoc_update() and migrate all params; what I see there is that random, chunks, hmac migrate from NULL each to the new values stored in the temp asoc (and thus we'd need auth_cap as well to be correct); after that, I see that asoc A goes from COOKIE_WAIT into ESTABLISHED (which seems to be in accordance to the RFC: "The endpoint should stay in or enter the ESTABLISHED state but it MUST ...") 6) later on, asoc B goes from COOKIE_ECHOED into ESTABLISHED So that led me to the resolution of transferring 'caps' over via sctp_assoc_update(). In that case, asoc A transitions from 0 -> 1 as previous 'caps' haven't been stored in the actual asoc. It stayed so far always in a temp asoc that we threw away after a reply. >>>> If not, then something else if wrong and my guess is that all >>>> other capabilities would be wrong too. >>> >>> I agree that they might likely also be flawed. >>> >>> Ok, let me dig further. >> >> So I think I know why case D ends up not authenticating the COOKIE-ACK. >> Most likely the reason is the following statement: >> repl = sctp_make_cookie_ack(new_asoc, chunk); >> >> Note that we use new_asoc, instead of current asoc. > > Thanks, I will give it a try. > > Btw, noticed also that when we have AUTH + COOKIE_ECHO collisions, > we don't seem to handle them properly either. The normal case works > fine, but in case of a collision both sides seem to use wrong RANDOM > etc params, and thus discard the handshake due to bad signature. > >> Not sure why case B is dumping core yet. > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html