Re: BGP-iSec: Improved Security of Internet Routing Against Post-ROV Attacks

[Amir Herzberg <amir.lists () gmail com>]

Job, many thanks for this detailed feedback! I copy Nanog on my response
below, since you sent there, but maybe we could move future emails off list
to avoid spamming people not into this subject.

* It appears that BGP-iSec requires a deployment flag day per Autonomous
>   System, rather than doing security upgrades "one EBGP session at a
>   time" (a deployment model both RPKI-ROV and BGPsec support).

Thanks for this important comment; indeed, if something like BGP-iSec would
be adopted as a standard, then such `flad day' requirement should indeed be
avoided. One simple option would be to allow an adopting AS X to include in
its relevant RPKI entry, a specific `enforcement time' T_E. Only after this
time would another adopting AS, say AS Y, drop announcements with origin AS
X but without a valid signature.   AS X will select the enforcement time
T_E to be sufficient in the future (upon deploying) to ensure that all of
its routers will already be deployed at that time. But we don't view
BGP-iSec as a proposal for adoption; we expect few improvements in future
work, in particular, improvements to its efficiency (which is currently
comparable to, and even somewhat higher than, that of BGPsec, i.e., quite
high). And additional evaluation is also very important (esp. from experts
like you, Job - thanks!) and may lead to changes. For example, we may do an
fix to the design soon to address an important comment from Joel Halpern
(thanks Joel!).

> * As noted in RFC 7132 [0], Google's [1], Fastly's [2] response to
>   the FCC "inquiry into internet routing vulnerabilities" which your
>   paper cites; BGPsec was consciously not designed to address route
>   leaks, as leaks are not precluded by the specification for BGP and
>   might be the result of a local policy that is not publicly disclosed.

That's correct. But, again, BGP-iSec is an academic paper, not a proposed
standard. In practically all papers on BGP security, we adopt the
valley-free routing model which basically forbids leaks. If this is
modified to a standard, I'm sure this issue can be addressed, similarly to
how it is dealt with in the OTC RFC.


>   To me the sentence "Even under full adoption, BGPsec does not prevent
>   route leaks" reads contentious, because of an implicit assertion that
>   BGPsec was intended to address route leaks.

Good point, we should clarify this indeed, thanks!


>   To me the above reads as "Even under full adoption of IPv6, world
>   hunger will not be achieved". E.g. seems a false equivalence is drawn.

I admit that sometimes it appears to me that full adoption of IPv6 will
indeed occur only after we solve world hunger.

> * It appears BGP-iSec took some inspiration from ASPA, but instead of
>   signalling the list of providers out-of-band (which ASPA does via the
>   RPKI publication system); BGP-iSec proposed an in-band signal in the
>   form of 'UP' messages encapsulated inside BGP Path Attributes.


Actually, I think we became aware of ASPA only after that part of the
design :)


> Again,
>   this suggests that BGP-iSec requires a flag day for all EBGP routers
>   in a given Autonomous System;

Here you're wrong. There is no problem if different EBGP routers adopt the
UP mechanism at different times; the mechanism will be implemented only for
announcements which passed via an adopting router, that's all, no harm.

> * The bold assertion made by the BGP-iSec authors that BGPSec offers
>   "meagre benefits in partial adoption" to me seems a subjective one.

You're right, we should clarify that we merely referred to the reductions
in hijack rates in simulations of the defense (under different adoption
percentages). Our expression was too extreme and may give wrong impression;
thanks for pointing this out.


>   Consider when two BGPSec-capable networks interconnect, both parties
>   immediately benefit from having secured that interconnection point.
>   For example, if this happens to be the interconnection between two
>   major cloud providers, the advantages are massive and can positively
>   benefit billions of indirect constituents.


 Let's say that these large cloud ASes, say AS A an AS Z have a direct
connection (BGP peering) and both adopt BGPsec. What benefit do you see (to
billions of entities)? In particular, do you think this prevents a attacker
from hijacking traffic sent from A to Z? I'm not sure. Consider AS 666 who
is a customer of AS A, and let 1.2.3/24 be a prefix of cloud/AS Z. Now, AS
666 may send an announcement with origin Z and path 666-Z to AS A; this may
be unsigned (without even receiving announcement of 1.2.3/24 from Z) or
even signed (if Z received the announcement from Z - e.g., when 666 is a
customer of Z). I think that in both cases, A ends up sending the traffic
via 666. So, can you clarify the benefits? I may miss something.


> Similarly, in the past I've
>   argued that only the biggest networks in the world need to do RPKI-ROV
>   for all of the Internet to take benefit from that deployment action by
>   a single small group. Comparing RPKI-ROV & BGPSec is apples and
>   oranges;


I definitely agree with this last statement. RPKI-ROV does not
automatically downgrade once an announcement exits an island of deploying
ASes.


> but the point stands that in an Internet with increased
>   centralization we have to rethink what exactly the consequences are of
>   so-called 'partial deployments' of security features.

But that's exactly what we try to do by using simulations to measure the
impact.

> I enjoyed reading the BGP-iSec paper and certainly view and appreciate
> it as an interesting perspective on the routing security problem space;
Thanks!


> but I think for very good reasons AS_PATH integrity (BGPsec) and AS_PATH
> route leaks (OPEN Policy, OTC, ASPA) are addressed as independent
> technology extensions to the routing stack.

I'm not arguing against separation. OTOH, our results show that OTC becomes
effective even against intentional attack, if protected by the same
integrity mechanisms we use to protect the AS-path.

> Sometimes, trying to kill two or three birds with one stone
> inadvertently introduces significant cost in unexpected places,
> presenting surprising barriers to deployment.

True. And deployment and standardization are very important and
challenging. BGP-iSec, at this point, is just an academic study studying
some new ideas and evaluating their impact in specific configurations,
under specific assumptions etc.; hopefully, this may provide some help to
the community in improving BGP security.
-- 
Amir Herzberg

Comcast professor of Security Innovations, Computer Science and
Engineering, University of Connecticut
Homepage: https://sites.google.com/site/amirherzberg/home
`Applied Introduction to Cryptography' textbook and lectures:
https://sites.google.com/site/amirherzberg/cybersecurity




On Mon, Nov 13, 2023 at 12:06 PM Job Snijders <job () fastly com> wrote:

> Dear Amir,
>
> On Fri, Nov 10, 2023 at 06:02:48PM -0500, Amir Herzberg wrote:
> > We will present our new work, titled: `BGP-iSec: Improved Security of
> > Internet Routing Against Post-ROV Attacks', in NDSS'24.
> >
> > If you're interested in security of Internet routing (BGP), and want a
> > copy, see URL below, drop me a message/email - or see us in the
> > conference - or just read the final version.
> >
> > Available from:
> https://www.researchgate.net/publication/375553362_BGP-iSec_Improved_Security_of_Internet_Routing_Against_Post-ROV_Attacks
>
> Thanks for freely sharing a copy! This allowed me to jot down some
> initial thoughts.
>
> * It appears that BGP-iSec requires a deployment flag day per Autonomous
>   System, rather than doing security upgrades "one EBGP session at a
>   time" (a deployment model both RPKI-ROV and BGPsec support).
>   This lack of "per EBGP session"-granularity doesn't make for a
>   feasible or viable deployment story in the global Internet routing
>   system - as quite some Autonomous Systems are composed of thousands of
>   routers which cannot be made to do the same thing at the same moment
>   for logistical and various other reasons. What BGP-iSec promotes as a
>   'feature' ("Mandatory Signatures for Announcement Integrity") - may
>   turn out to be its biggest impediment towards deployment in the real
>   world.
>
> * As noted in RFC 7132 [0], Google's [1], Fastly's [2] response to
>   the FCC "inquiry into internet routing vulnerabilities" which your
>   paper cites; BGPsec was consciously not designed to address route
>   leaks, as leaks are not precluded by the specification for BGP and
>   might be the result of a local policy that is not publicly disclosed.
>   To me the sentence "Even under full adoption, BGPsec does not prevent
>   route leaks" reads contentious, because of an implicit assertion that
>   BGPsec was intended to address route leaks.
>   To me the above reads as "Even under full adoption of IPv6, world
>   hunger will not be achieved". E.g. seems a false equivalence is drawn.
>
> * It appears BGP-iSec took some inspiration from ASPA, but instead of
>   signalling the list of providers out-of-band (which ASPA does via the
>   RPKI publication system); BGP-iSec proposed an in-band signal in the
>   form of 'UP' messages encapsulated inside BGP Path Attributes. Again,
>   this suggests that BGP-iSec requires a flag day for all EBGP routers
>   in a given Autonomous System; whereas deployment of the ASPA signal
>   happens via a singular place (the RIR RPKI web portal), and in order
>   to publish an ASPA object, no changes have to be executed on the
>   Autonomous System's EBGP routers.
>
> * The bold assertion made by the BGP-iSec authors that BGPSec offers
>   "meagre benefits in partial adoption" to me seems a subjective one.
>   Consider when two BGPSec-capable networks interconnect, both parties
>   immediately benefit from having secured that interconnection point.
>   For example, if this happens to be the interconnection between two
>   major cloud providers, the advantages are massive and can positively
>   benefit billions of indirect constituents. Similarly, in the past I've
>   argued that only the biggest networks in the world need to do RPKI-ROV
>   for all of the Internet to take benefit from that deployment action by
>   a single small group. Comparing RPKI-ROV & BGPSec is apples and
>   oranges; but the point stands that in an Internet with increased
>   centralization we have to rethink what exactly the consequences are of
>   so-called 'partial deployments' of security features.
>
> I enjoyed reading the BGP-iSec paper and certainly view and appreciate
> it as an interesting perspective on the routing security problem space;
> but I think for very good reasons AS_PATH integrity (BGPsec) and AS_PATH
> route leaks (OPEN Policy, OTC, ASPA) are addressed as independent
> technology extensions to the routing stack.
>
> Sometimes, trying to kill two or three birds with one stone
> inadvertently introduces significant cost in unexpected places,
> presenting surprising barriers to deployment.
>
> Kind regards,
>
> Job
>
> [0]: https://datatracker.ietf.org/doc/html/rfc7132
> [1]: https://www.fcc.gov/ecfs/document/104112834502222/1
> [2]:
> https://sobornost.net/~job/fastly-fcc-noi-secure-internet-routing-reply-comments-20220510-201259363-pdf.pdf