Re: [secdir] Routing loop attacks using IPv6 tunnels

"Templin, Fred L" <Fred.L.Templin@boeing.com> Fri, 28 August 2009 20:23 UTC

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From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
To: "Gabi Nakibly" <gnakibly@yahoo.com>, "v6ops" <v6ops@ops.ietf.org>
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Subject: Re: [secdir] Routing loop attacks using IPv6 tunnels
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Gabi,

Thanks for your continued correspondence, and see below:

> -----Original Message-----
> From: Gabi Nakibly [mailto:gnakibly@yahoo.com]
> Sent: Friday, August 28, 2009 12:02 PM
> To: Templin, Fred L; v6ops
> Cc: ipv6@ietf.org; secdir@ietf.org
> Subject: Re: Routing loop attacks using IPv6 tunnels
> 
> Fred,
> A quick summary of our discussion up until now: the best mitigation of most of these attacks is
> indeed the proto-41 and ingress filtering on the border of the ISATAP site. If it is indeed
> implemented. I assume that not all sites deploy such filtering for lack of awareness or since the
> proto-41 filtering may break other tunnels the site may employ. However, I do not have hard evidence
> on this. I would be happy if others on the list will refute or justify this assumption.
> 
> If this assumption is (even partially) correct than I think that the ISATAP router should defend
> itself.

If there is operational assurance of filtering, then I think there
is no problem. For the other cases, I am beginning to come around
to your opinion.

> Moreover, as I mention below the proo-41 filtering is not effective in case of attack
> #3 and the attacker is internal to the site.

I'll speak more on this below.

> So IMHO the best way is the mitigations I suggested and
> that you illustrated below in pseudo-code.

OK.

> See further comments inline.
> 
> Gabi
> 
> ----- Original Message ----
> > From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
> > To: Gabi Nakibly <gnakibly@yahoo.com>om>; v6ops <v6ops@ops.ietf.org>
> > Cc: ipv6@ietf.org; secdir@ietf.org
> > Sent: Monday, August 24, 2009 10:04:34 PM
> > Subject: RE: Routing loop attacks using IPv6 tunnels
> >
> > Gabi,
> >
> > > -----Original Message-----
> > > From: Gabi Nakibly [mailto:gnakibly@yahoo.com]
> > > Sent: Monday, August 24, 2009 4:44 AM
> > > To: Templin, Fred L; v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Subject: Re: Routing loop attacks using IPv6 tunnels
> > >
> > > Fred,
> > > I initially very much liked your suggestion regarding the check of the
> > neighbor cache before
> > > forwarding a packet into the tunnel. It truly addresses the root cause of the
> > problem ans is simple
> > > enough to implement. However, I realized that an attacker can send a
> > spoofed RS to the ISATAP router
> > > as if it came from the 6to4 relay. The router would then send a RA to it and
> > consequently change its
> > > neighbor cache. So it seems that this defense does not add much. Wouldn't you
> > agree?
> >
> > I agree that my proposed mitigation is only useful when there
> > is assurance of a coherent neighbor cache in the ISATAP router.
> > That would be true in the case in which the ISATAP router is
> > located within a site protected by border routers that perform
> > ip-proto-41 and ingress filtering, and in which there is no
> > untraceable IPv4 source address spoofing. So AFAICT, my proposed
> > mitigation is still necessary for preventing attack #3 when
> > ISATAP routers A and B are on separate ISATAP links within
> > the same site-internal IPv4 routing region.
> >
> 
> This is only true when the attacker is outside the site and proto-41 filtering is employed. If the
> attacker is internal to the site then the proto-41 filtering will not help and the neighbor cache can
> be poisoned.

Since the ISATAP checks require that the IPv6 source embed the
IPv4 source and/or the IPv4 source is a PRL router, you must be
speaking here about IPv4 source address spoofing from within the
site. For sites that allow intra-site source address spoofing,
I think much more serious problems could manifest themselves
that would be completely unrelated to ISATAP. I believe you
will also find other automatic tunneling protocols besides
ISATAP that operate under an assumption of no intra-site IPv4
source address spoofing. 

> > > I completely agree with your observation on the non-feasibility of
> > verifying that the
> > > destination ISATAP address does not include a local IPv4 address since the
> > ISATAP address may include
> > > a private IPv4 address. On the other hand, a check on public IPv4 addresses is
> > acceptable. If the
> > > check would be done only on ISATAP addresses that include public IPv4
> > addresses then this will
> > > eliminate the attacks in which the two victims reside at different sites. Note
> > that if attack #3 is
> > > launched on two ISATAP routers having private addresses at two different sites
> > then the attack will
> > > not work anyway since one router can not send a direct IPv4 packet to the
> > other. In addition,
> > > to mitigate attacks in which the other victim is a 6to4 relay (such as attack
> > #1) then a check would
> > > have to be done on a 6to4 address, i.e. the destination address must not be
> > "2002:> > the ISATAP router>::*". In this case the IPv4 address must be public,
> > according to
> > >  the 6to4 spec.
> > >
> > > As you also noted there is another problem with this check since the string
> > "200::5EFE" is not unique
> > > to ISATAP links. On the other hand, it seems that the probability to encounter
> > a non-malicious packet
> > > with a destination address having an IID that equals "200:5EFE:> IPv4 address>" is
> > > pretty slim.
> > >
> > > This check is definitely not a perfect solution, and I sure hope that someone
> > will come up with a
> > > better one for mitigating the routing loops. However, I would be happy if
> > there is some kind of other
> > > mitigation measures besides packet filtering (proto-41 and ingress) by other
> > nodes (which does not
> > > necessarily exist).
> >
> > You seem to be envisioning a scenario of ISATAP router operation
> > with public IPv4 addresses and outside of any site border routers
> > that perform ingress filtering and ip-proto-41 filtering. That has
> > traditionally been seen as the domain of 6to4, but I am happy to
> > discuss the possibility of what I called the "inside-out ISATAP
> > model" in a list message long ago (which AFAICT is the scenario
> > you are alluding to).
> >
> 
> Well, I am referring to any ISATAP deployment with public IPv4 addresses and no proto-41 filtering. I
> imagine that in practice there are such deployments which are not the "inside-out ISATAP model" .
> However, I must admit that I do not rely here on hard evidence.
> 
> > So, if the public IPv4 Internet were considered as one gigantic
> > "site" and we wanted to do ISATAP on that site, it would be nice
> > to divide the site into multiple logical partitions, with each
> > partition identified by a PRL name and a unique set of IPv6
> > prefixes. But then, we have the scenario you are describing in
> > which we can't trust the integrity of the ISATAP router's
> > neighbor cache due to the possibility for untraceable IPv4
> > source address spoofing such that the neighbor cache check
> > mitigation can be subverted.
> >
> > This means that if we want to support the inside-out ISATAP
> > model then the routing loops could be mitigated either by
> > 1) implementing the destination address checks you are
> > suggesting, or 2) by not allowing ISATAP router interfaces
> > that are not behind filtering border routers to advertise
> > non-link-local on-link IPv6 prefixes and/or forward packets
> > from non-link-local prefixes in the first place.
> >
> > If we took the easy way out and did 2), then the entire
> > IPv4 Internet would look like one gigantic ISATAP link that
> > only did IPv6 link-local. So, nodes could ping6 each others'
> > ISATAP link-local addresses but that's about it.
> >
> > If we took the more ambitious route and allowed ISATAP to
> > flourish fully within the global IPv4 Internet, then we
> > would essentially be deprecating 6to4 - so it isn't
> > surprising that your address checks mostly involve 6to4
> > suppression. Assuming this, if I read your attack scenarios
> > 1 through 3 correctly then scenarios 1 and 3 are mitigated
> > by a receive-side check and scenario 2 is mitigated by a
> > send-side check. In particular, the pseudo-code would be:
> >
> >   isatap_rcv() {
> >     ...
> >     if (dst == "2002:<my_ipv4_addr>::*")
> >       drop_pkt(); /* attack #1 mitigation */
> >
> >     if (dst == "*::0200:5efe:<my_ipv4_addr>")
> >     drop_pkt(); /* attack #3 mitigation */
> >     ...
> >   }
> >
> 
> Correct (with the correction you sent after this email).

OK.
 
> >   isatap_xmt() {
> >     ...
> >     if (dst == "*::0200:5efe:192.88.99.1")
> >       drop_pkt(); /* attack #2 mitigation */
> >     ...
> >   }
> 
> This will not necessarily work, since the 6to4 relay may have a unicast address the ISATAP router may
> not be aware of. The best way to mitigate attack #2 is by the 6to4 relay with a check similar to that
> of attack #2 above. IMO, the second best way, as Remi suggested on another thread, is for the ISATAP
> router to drop the packet if (src  == 2002:<my_ipv4_addr>::*"). However, this check is useful only
> when the 6to4 relay validates that the IPv6 source address corresponds to the IPv4 one (this is
> in accordance with the 6to4 spec, however it does not always get implemented). If this is not true
> then the attacker does not have to send the attack packet with such an address.

Keeping with the philosophy of the ISATAP router defending itself,
I believe it would be best to take Remi's suggestion and lay any
complications at the doorstep of the 6to4 relay if it fails to
adhere to the spec.

Thanks - Fred
fred.l.templin@boeing.com

> > Does the above look right to you? And is this everything,
> > or are there other scenarios we need to consider?
> >
> 
> 
> > Thanks - Fred
> > fred.l.templin@boeing.com
> >
> > >
> > > Gabi
> > >
> > > ----- Original Message ----
> > > From: "Templin, Fred L"
> > > To: Gabi Nakibly ; v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Sent: Wednesday, August 19, 2009 6:16:18 PM
> > > Subject: RE: Routing loop attacks using IPv6 tunnels
> > >
> > > Hi Gabi,
> > >
> > > I'm sorry to have to keep turning this into plaintext,
> > > but annotation is difficult otherwise. See below for
> > > my responses (==>):
> > >
> > > ________________________________________
> > > From: Gabi Nakibly [mailto:gnakibly@yahoo.com]
> > > Sent: Wednesday, August 19, 2009 1:49 AM
> > > To: Templin, Fred L; v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Subject: Re: Routing loop attacks using IPv6 tunnels
> > >
> > > Fred,
> > > See my comments inline ().
> > >
> > > ________________________________________
> > > From: "Templin, Fred L"
> > > To: Gabi Nakibly ; v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Sent: Tuesday, August 18, 2009 6:48:45 PM
> > > Subject: RE: Routing loop attacks using IPv6 tunnels
> > >
> > > Gabi,
> > >
> > > ________________________________________
> > > From: Gabi Nakibly [mailto:gnakibly@yahoo.com]
> > > Sent: Tuesday, August 18, 2009 3:29 AM
> > > To: Templin, Fred L; v6ops
> > > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > > Subject: Re: Routing loop attacks using IPv6 tunnels
> > > >
> > > > Indeed the ISATAP interface of the ISATAP router is meant
> > > > to be an enterprise-interior (note that it is still assumed
> > > > that the associated IPv4 address is non-private). As we
> > > > explicitly note in the paper, the first three attacks will
> > > > be mitigated if proper protocol-41 filtering is deployed on
> > > > the site's border. However, note that RFC5214 does not mandate
> > > > or require this filtering.
> > >
> > > The RFC5214 Security Considerations makes clear the
> > > consequences of not implementing IPv4 ingress filtering
> > > and ip-protocol-41 filtering (i.e., a possible spooing
> > > attack in which spurious ip-protocol-41 packets are
> > > injected into an ISATAP link from outside). RFC5214
> > > Section 6.2 additionally requires that an ISATAP interface's
> > > locator set MUST NOT span multiple sites. This means that the
> > > ISATAP interface must not decapsulate nor source ip-proto-41
> > > packets within multiple sites, where the enterprise interior
> > > is site #1 and the global Internet is site #2. ip-protocol-41
> > > filtering is the way in which the ISATAP interface is
> > > restricted to a single site.
> > >
> > > Now let me see that I understand Section 6.2 correctly. In
> > > attack #2, for example, I assume the ISATAP router has two
> > > physical interfaces. A site-internal IPv4 interface with an
> > > address IPisatap and a site-external IPv6 interface. I also
> > > assume that there is another border router which connects the
> > > site to the IPv4 Internet. The ISATAP router has an ISATAP
> > > interface with a single locator: (IPisatap, site-internal
> > > interface). When the ISATAP router gets an IPv6 via its
> > > external interface it will encapsulate the packet accordingly
> > > and forward it through the internal IPv4 interface. If the
> > > encapsulated packet is destined to a node outside the site
> > > then the only thing that stops it is a proto-41 filtering
> > > at the other border router of the site. Did I get this right?
> > >
> > >
> > > ==> In this case, yes - the ip-proto-41 filtering is at a
> > > ==> border router. I know of at least one major enterprise
> > > ==> network that does this.
> > >
> > > > It is only mentioned as a possible mitigation against
> > > > incoming spurious protocol-41 packets. In addition,
> > > > Section 10 of RFC5214 only mentions ingress not egress
> > > > filtering. Hence it will not stop attack #2.
> > >
> > > We are now talking about ip-proto-41 filtering; not ingress
> > > filtering. ip-proto-41 filtering is in both directions. It
> > > prevents ip-proto-41 packets from entering the enterprise
> > > interior ISATAP site from the Internet and prevents
> > > ip-proto-41 packets from entering the Internet ISATAP
> > > site from the enterprise interior. Else the ISATAP
> > > interface would span multiple sites.
> > >
> > > Besides, "ingress" filtering is not about packets coming
> > > from the Internet into the end site, but rather it is
> > > about packets leaving the end site and going out into
> > > the Internet. RFC2827 (BCP38) documents ingress filtering.
> > >
> > > OK. I see what you are saying here.
> > >
> > >
> > > ==> OK.
> > >
> > > > In addition,
> > > > as mentioned, protocol-41 filtering is not helpful when
> > > > attack #3 is launched on two routers that reside in the
> > > > same site. Note that it may be possible for the attack
> > > > packet to be sourced from outside the site unless proper
> > > > filtering of incoming IPv6 packets is deployed. If the
> > > > attacker resides in the site, usually ingress filtering
> > > > will not be helpful since it is deployed in general on
> > > > the site's border.
> > >
> > > Here, we have the ISATAP router in both cases sourcing a
> > > packet from a foreign prefix.
> > >
> > > Well, I do not see how this is correct. In attacks #1 and #3 the ISATAP router
> > sources (actually
> > > forwards) an IPv6 packet with a source address having the corresponding prefix
> > of the ISATAP tunnel.
> > > In attacks #2 and #3 the ISATAP router sources and IPv4 packet with its own
> > IPv4 address as the
> > > source address.
> > >
> > >
> > > ==> There were a number of errors in what I said in my last
> > > ==> message, so let me see if I can get it right here:
> > > ==>
> > > ==> In attacks #1 and #2 there are two cases to consider. Case
> > > ==> 1 in which a border router separates the 6to4 relay from the
> > > ==> ISATAP router, and case 2 in which no border router separates
> > > ==> the 6to4 relay from the ISATAP router.
> > > ==>
> > > ==> In attack #1, we have an IPv6 packet with a local source
> > > ==> address entering the site from the outside. IPv6 ingress
> > > ==> filtering at the site border router should prevent the
> > > ==> packet from entering the site in the first place. If the
> > > ==> 6to4 relay router is outside the site then ip-proto-41
> > > ==> filtering at the border router will block the attack in
> > > ==> the first place anyway. If the relay router is *inside*
> > > ==> the site, then the IPv6 ingress filtering is the lone
> > > ==> mitigation. The end result is that the 6to4 relay should
> > > ==> really be positioned outside of the site's border routers;
> > > ==> otherwise, it could be spoofed into thinking that the
> > > ==> ISATAP router is a 6to4 router and not an ISATAP router.
> > > ==>
> > > ==> In attack #2, we have an IPv6 packet with a foreign source
> > > ==> address being forwarded by the ISATAP router to a 6to4
> > > ==> relay, but I mis-spoke when I said that this would be a
> > > ==> case of the ISATAP router forwarding a packet with a foreign
> > > ==> source address out of the ISATAP link. For all the ISATAP
> > > ==> router knows, the 6to4 relay is just an ordinary host on
> > > ==> the ISATAP link, so the ISATAP router actually believes it
> > > ==> is forwarding the packet *into* the ISATAP link (not out of
> > > ==> it). But as in attack #1, the attack is blocked by ip-proto-41
> > > ==> filtering at the border router between the ISATAP router and
> > > ==> the 6to4 relay. If there is no border router between the ISATAP
> > > ==> router and the 6to4 relay, then we have an identical instance
> > > ==> to attack #3 which I will discuss below. But, the best
> > > ==> operational practice would again be to have the 6to4 relay
> > > ==> oriented outside of a border router that filters ip-proto-41.
> > > ==>
> > > ==> Short summary is that in attack #1, the 6to4 relay thinks it
> > > ==> is talking to a 6to4 router and not an ISATAP router. In
> > > ==> attack #2, the ISATAP router thinks it is talking to a
> > > ==> simple host on the link and not a 6to4 relay. In both cases,
> > > ==> the attacks are mitigated when there is an ip-proto-41
> > > ==> filtering border router between the ISATAP router and the
> > > ==> 6to4 relay. Oftentimes, the "border router" will be a two-
> > > ==> interface router that implements 6to4 on a site-external
> > > ==> IPv4 interface and implements ISATAP on a site-internal
> > > ==> IPv4 interface and performs ip-proto-41 filtering on packets
> > > ==> from outside the site with an IPv4 destination corresponding
> > > ==> to the ISATAP interface. I will discuss attack #3 below:
> > >
> > > This attack is mitigated by
> > > IPv6 ingress filtering which is an IPv6 security consideration
> > > and not an ISATAP nor IPv4 security consideration. BCP
> > > recommendations for network ingress filtering are documented
> > > in RFC2827 and it is expected that IPv6 routers that configure
> > > ISATAP interfaces will implement IPv6 ingress filtering
> > > according to the BCP.
> > >
> > > So If my last comment is correct than I do not see how ingress filtering would
> > help here. The only
> > > case where ingress filtering can help is in case of attack #3 when the routers
> > reside at the same
> > > site. In that case if the attack packet (packet 0) is sent from outside the
> > site then ingress
> > > filtering on the border of the site will drop the packet.
> > >
> > >
> > > ==> Correct about the IPv6 ingress filtering at the border,
> > > ==> but as with attack #2 my error in the previous message
> > > ==> was in thinking the ISATAP router A was forwarding the
> > > ==> packet *out* of the ISATAP link when in fact from the
> > > ==> ISATAP router's perspective it is forwarding the packet
> > > ==> to a simple host *inside* of the link.
> > > ==>
> > > ==> The problem here is that the ISATAP router is blindly
> > > ==> forwarding a packet to a node that it assumes is a simple
> > > ==> host on the ISATAP link without first verifying that the
> > > ==> node has demonstrated a willingness to participate as a
> > > ==> host on the link. As you have pointed out, this can lead
> > > ==> to strange scenarios when the anonymous node is a tunnel
> > > ==> router of some sort that does not participate in the
> > > ==> ISATAP link.
> > > ==>
> > > ==> It would not generally be possible for the ISATAP router
> > > ==> to check whether the IPv6 destination address is an ISATAP
> > > ==> address that embeds one of its own IPv4 addresses, because
> > > ==> when IPv4 private addresses are used the same IPv4 address
> > > ==> can (and often does) occur in multiple sites. So for example,
> > > ==> if the ISATAP router configures an IPv4 address 10.0.0.1
> > > ==> and is asked to forward an IPv6 packet with ISATAP
> > > ==> destination address 2001:DB8::0:5EFE:10.0.0.1 where the
> > > ==> IPv6 prefix is foreign, the router can't very well drop the
> > > ==> packet as this would block legitimate communications. It
> > > ==> is also not generally possible to check whether a foreign
> > > ==> link is an ISATAP link by looking for the magic token
> > > ==> "0:5EFE" as that token only has significance for ISATAP
> > > ==> links and not other link types.
> > > ==>
> > > ==> Instead, the mitigation I think makes the most sense is
> > > ==> for the ISATAP router to first verify that the node which
> > > ==> it assumes to be a simple ISATAP host has demonstrated a
> > > ==> willingness to participate in the link. That can be done
> > > ==> by having the ISATAP router first check the neighbor cache
> > > ==> when it has a packet to send to verify that there is a
> > > ==> cached entry corresponding to the destination. For nodes
> > > ==> that are willing ISATAP hosts on the link, there would
> > > ==> have been a neighbor cache entry created when the node
> > > ==> sends a Router Solicitation to the ISATAP router for the
> > > ==> purpose of discovering default router lifetimes and on-
> > > ==> link prefixes. So, the simple mitigations is for the ISATAP
> > > ==> router to forward the packet only if there is a pre-existing
> > > ==> neighbor cache entry and drop the packet otherwise. This
> > > ==> implies that the router should keep neighbor cache entires
> > > ==> for the duration of the minimum lifetime of the prefixes
> > > ==> it advertises in its Router Advertisements.
> > >
> > > > In general, I would like to point out that indeed as in
> > > > most other attacks these attacks may also be mitigated by
> > > > proper firewall rules. However, I do not believe that this
> > > > should be our only answer against these attacks. I believe
> > > > that since these attacks are made possible due to the
> > > > inherent characteristics of the tunnels they should be
> > > > stopped intrinsically as much as possible by the tunnel
> > > > participants and not relay on outside filtering rules.
> > >
> > > In RFC5214, Section 10 we have: "restricting access to the
> > > link can be achieved by restricting access to the site". The
> > > mitigations do exactly that, and in such a way that ISATAP
> > > nodes can operate with only the necessary and sufficient
> > > checks. So on this point, I do not share your opinion.
> > >
> > > What about two ISATAP tunnels that reside on the same site like in attack #3.
> > Do you also think that
> > > proto-41 filtering should barrier between the two tunnels within the site?
> > >
> > >
> > > ==> I think this may be overcome by the discussion above.
> > > ==> Short story is that operational practices must be
> > > ==> employed whereby an ISATAP router is not mistaken for
> > > ==> a 6to4 router. This is through proper arrangement of
> > > ==> 6to4 router/relay interfaces outside of the site border
> > > ==> rather than inside, and ISATAP router interfaces inside
> > > ==> of the site border rather than outside. Also proper
> > > ==> ip-proto-41 filtering and IPv6 ingress filtering at
> > > ==> site borders.
> > > ==>
> > > ==> Also, when there are multiple ISATAP links within the
> > > ==> same local IPv4 routing region, an ISATAP router should
> > > ==> first verify a node's willingness to act as a host on
> > > ==> the ISATAP link before blindly sending a packet to it.
> > > ==>
> > > ==> Fred
> > > ==> fred.l.templin@boeing.com
> > >
> > > Fred
> > > fred.l.templin@boeing.com
> > >
> > > ________________________________________
> > > From: "Templin, Fred L"
> > > To: Gabi Nakibly ; v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Sent: Monday, August 17, 2009 8:35:08 PM
> > > Subject: RE: Routing loop attacks using IPv6 tunnels
> > >
> > >
> > > Gabi,
> > >
> > > Thanks for publishing this work. In the document, attacks A, B and C
> > > correspond to a configuration that violates section 6.2 of RFC5214:
> > >
> > > > 6.2.  ISATAP Interface Address Configuration
> > > >
> > > >   Each ISATAP interface configures a set of locators consisting of IPv4
> > > >   address-to-interface mappings from a single site; i.e., an ISATAP
> > > >   interface's locator set MUST NOT span multiple sites.
> > >
> > > In particular, in scenarios A, B and C the IPv4 locator used for ISATAP
> > > is seen both within the enterprise as site #1 and within the global Internet
> > > itself as site #2. If the ISATAP interface is to be used as an enterprise-
> > > interior interface, it should therefore not accept IP-proto-41 packets
> > > coming from an IPv4 source outside of the enterprise nor source
> > > IP-proto-41 packets that are destined to an IPv4 node outside of the
> > > enterprise. This condition should be satisfied by having the site border
> > > routers implement IPv4 ingress filtering and ip-protocol-41 filtering as
> > > required in Section 10 of RFC5214.
> > >
> > > It is mentioned that attack C could also occur when the routers reside
> > > in the same site, where their addresses may be private. This would
> > > correspond to a case in which an attacker within the site attacks the
> > > site itself, which can easily be traced - especially when source address
> > > spoofing from a node within the site is prevented through proper ingress
> > > filtering.
> > >
> > > Fred
> > > fred.l.templin@boeing.com
> > >
> > > ________________________________________
> > > From: Gabi Nakibly [mailto:gnakibly@yahoo.com]
> > > Sent: Monday, August 17, 2009 8:21 AM
> > > To: v6ops
> > > Cc: ipv6@ietf.org; secdir@ietf.org
> > > Subject: Routing loop attacks using IPv6 tunnels
> > >
> > > Hi all,
> > > I would like to draw the attention of the list to some research results which
> > my colleague and I at
> > > the National EW Research & Simulation Center have recently published. The
> > research presents a class
> > > of routing loop attacks that abuses 6to4, ISATAP and Teredo. The paper can be
> > found at:
> > > http://www.usenix.org/events/woot09/tech/full_papers/nakibly.pdf
> > >
> > > Here is the abstract:
> > > IPv6 is the future network layer protocol for the Internet. Since it is not
> > compatible with its
> > > predecessor, some interoperability mechanisms were designed. An important
> > category of these
> > > mechanisms is automatic tunnels, which enable IPv6 communication over an IPv4
> > network without prior
> > > configuration. This category includes ISATAP, 6to4 and Teredo. We present a
> > novel class of attacks
> > > that exploit vulnerabilities in these tunnels. These attacks take advantage of
> > inconsistencies
> > > between a tunnel's overlay IPv6 routing state and the native IPv6 routing
> > state. The attacks form
> > > routing loops which can be abused as a vehicle for traffic amplification to
> > facilitate DoS attacks.
> > > We exhibit five attacks of this class. One of the presented attacks can DoS a
> > Teredo server using a
> > > single packet. The exploited vulnerabilities are embedded in the design of the
> > tunnels; hence any
> > > implementation of these tunnels may be vulnerable. In particular, the attacks
> > were tested
> > > against the ISATAP, 6to4 and Teredo implementations of Windows Vista and
> > Windows Server 2008 R2.
> > >
> > > I think the results of the research warrant some corrective action. If
> > this indeed shall be the
> > > general sentiment of the list, I will be happy write an appropriate I-D. The
> > mitigation measures we
> > > suggested in the paper are the best we could think of to completely eliminate
> > the problem. However
> > > they are far from perfect since they would require tunnel implementations to
> > be updated in case new
> > > types of automatic tunnels are introduced.
> > >
> > > Your comments are welcome.
> > >
> > > Gabi
> > >
> > >
> > >
> 
> 
>