From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH net] net: sctp: fix ipv6 ipsec encryption bug in sctp_v6_xmit Date: Tue, 10 Sep 2013 14:58:37 -0400 Message-ID: <522F6BDD.3050309@gmail.com> References: <1378836316-17503-1-git-send-email-dborkman@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-sctp@vger.kernel.org, adobriyan@gmail.com, Steffen Klassert , Hannes Frederic Sowa To: Daniel Borkmann Return-path: Received: from mail-ie0-f182.google.com ([209.85.223.182]:54721 "EHLO mail-ie0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750901Ab3IJS6n (ORCPT ); Tue, 10 Sep 2013 14:58:43 -0400 In-Reply-To: <1378836316-17503-1-git-send-email-dborkman@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 09/10/2013 02:05 PM, Daniel Borkmann wrote: > Alan Chester reported an issue with IPv6 on SCTP that IPsec traffic is not > being encrypted, whereas on IPv4 it is. Setting up an AH + ESP transport > does not seem to have the desired effect: > > SCTP + IPv4: > > 22:14:20.809645 IP (tos 0x2,ECT(0), ttl 64, id 0, offset 0, flags [DF], proto AH (51), length 116) > 192.168.0.2 > 192.168.0.5: AH(spi=0x00000042,sumlen=16,seq=0x1): ESP(spi=0x00000044,seq=0x1), length 72 > 22:14:20.813270 IP (tos 0x2,ECT(0), ttl 64, id 0, offset 0, flags [DF], proto AH (51), length 340) > 192.168.0.5 > 192.168.0.2: AH(spi=0x00000043,sumlen=16,seq=0x1): > > SCTP + IPv6: > > 22:31:19.215029 IP6 (class 0x02, hlim 64, next-header SCTP (132) payload length: 364) > fe80::222:15ff:fe87:7fc.3333 > fe80::92e6:baff:fe0d:5a54.36767: sctp > 1) [INIT ACK] [init tag: 747759530] [rwnd: 62464] [OS: 10] [MIS: 10] > > Moreover, Alan says: > > This problem was seen with both Racoon and Racoon2. Other people have seen > this with OpenSwan. When IPsec is configured to encrypt all upper layer > protocols the SCTP connection does not initialize. After using Wireshark to > follow packets, this is because the SCTP packet leaves Box A unencrypted and > Box B believes all upper layer protocols are to be encrypted so it drops > this packet, causing the SCTP connection to fail to initialize. When IPsec > is configured to encrypt just SCTP, the SCTP packets are observed unencrypted. > > In fact, using `socat sctp6-listen:3333 -` on one end and transferring "plaintext" > string on the other end, results in cleartext on the wire where SCTP eventually > does not report any errors, thus in the latter case that Alan reports, the > non-paranoid user might think he's communicating over an encrypted transport on > SCTP although he's not (tcpdump ... -X): > > ... > 0x0030: 5d70 8e1a 0003 001a 177d eb6c 0000 0000 ]p.......}.l.... > 0x0040: 0000 0000 706c 6169 6e74 6578 740a 0000 ....plaintext... > > Only in /proc/net/xfrm_stat we can see XfrmInTmplMismatch increasing on the > receiver side. Initial follow-up analysis from Alan's bug report was done by > Alexey Dobriyan. > > SCTP has its own implementation of sctp_v6_xmit() not calling inet6_csk_xmit(). > This has the implication that it probably never really got updated along with > changes in inet6_csk_xmit() and therefore does not seem to invoke xfrm handlers. > SCTP's IPv4 xmit however, properly calls ip_queue_xmit() to do the work. Hence, > lets do the same for IPv6 and invoke inet6_csk_xmit() [it does the same work > for us we do here manually anyway]; result is that we do not have any > XfrmInTmplMismatch increase plus on the wire with this patch it now looks like: > > SCTP + IPv6: > > 08:17:47.074080 IP6 2620:52:0:102f:7a2b:cbff:fe27:1b0a > 2620:52:0:102f:213:72ff:fe32:7eba: > AH(spi=0x00005fb4,seq=0x1): ESP(spi=0x00005fb5,seq=0x1), length 72 > 08:17:47.074264 IP6 2620:52:0:102f:213:72ff:fe32:7eba > 2620:52:0:102f:7a2b:cbff:fe27:1b0a: > AH(spi=0x00003d54,seq=0x1): ESP(spi=0x00003d55,seq=0x1), length 296 > > This fixes Kernel Bugzilla 24412. This security issue seems to be present since > 2.6.18 kernels. Lets just hope some big passive adversary in the wild didn't have > its fun with that. lksctp-tools IPv6 regression test suite passes as well with > this patch. > > Reported-by: Alan Chester > Reported-by: Alexey Dobriyan > Signed-off-by: Daniel Borkmann > Cc: Steffen Klassert > Cc: Hannes Frederic Sowa > --- > net/sctp/ipv6.c | 34 ++++++++-------------------------- > 1 file changed, 8 insertions(+), 26 deletions(-) > > diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c > index da613ce..74ba5ee 100644 > --- a/net/sctp/ipv6.c > +++ b/net/sctp/ipv6.c > @@ -69,6 +69,7 @@ > #include > #include > #include > +#include > #include > #include > > @@ -209,39 +210,20 @@ static int sctp_v6_xmit(struct sk_buff *skb, struct sctp_transport *transport) > { > struct sock *sk = skb->sk; > struct ipv6_pinfo *np = inet6_sk(sk); > - struct flowi6 fl6; > > - memset(&fl6, 0, sizeof(fl6)); > - > - fl6.flowi6_proto = sk->sk_protocol; > - > - /* Fill in the dest address from the route entry passed with the skb > - * and the source address from the transport. > - */ > - fl6.daddr = transport->ipaddr.v6.sin6_addr; > - fl6.saddr = transport->saddr.v6.sin6_addr; > - > - fl6.flowlabel = np->flow_label; > - IP6_ECN_flow_xmit(sk, fl6.flowlabel); > - if (ipv6_addr_type(&fl6.saddr) & IPV6_ADDR_LINKLOCAL) > - fl6.flowi6_oif = transport->saddr.v6.sin6_scope_id; > - else > - fl6.flowi6_oif = sk->sk_bound_dev_if; > - > - if (np->opt && np->opt->srcrt) { > - struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt; > - fl6.daddr = *rt0->addr; > - } > + /* This needs to explicitly done as we can have different transports. */ > + np->daddr = transport->ipaddr.v6.sin6_addr; > + np->saddr = transport->saddr.v6.sin6_addr; > > pr_debug("%s: skb:%p, len:%d, src:%pI6 dst:%pI6\n", __func__, skb, > - skb->len, &fl6.saddr, &fl6.daddr); > - > - SCTP_INC_STATS(sock_net(sk), SCTP_MIB_OUTSCTPPACKS); > + skb->len, &np->saddr, &np->daddr); > > if (!(transport->param_flags & SPP_PMTUD_ENABLE)) > skb->local_df = 1; > > - return ip6_xmit(sk, skb, &fl6, np->opt, np->tclass); > + SCTP_INC_STATS(sock_net(sk), SCTP_MIB_OUTSCTPPACKS); > + > + return inet6_csk_xmit(skb, NULL); > } > > /* Returns the dst cache entry for the given source and destination ip > I don't think this is actually the correct thing to do. 1) Every transmit has a possibility of changing np and thus changing the result of getsockname() and getpeername() 2) You will end up with a route lookup on every packet since np->dst_cookie is not set properly. I wonder if it would solve things if you simply pass the flowi cached in the transport to ip6_xmit(). If not, then probably sctp_v6_get_dst() needs to be updated to find the correct route, so then it can be cached in the transport along with the flowi and used on output. -vlad -vlad -vlad