Re: [secdir] secdir review of draft-ietf-ospf-encapsulation-cap-06

<bruno.decraene@orange.com> Tue, 19 September 2017 08:15 UTC

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From: <bruno.decraene@orange.com>
To: Robert Raszuk <robert@raszuk.net>
CC: "iesg@ietf.org" <iesg@ietf.org>, David Mandelberg <david@mandelberg.org>, "draft-ietf-ospf-encapsulation-cap.all@ietf.org" <draft-ietf-ospf-encapsulation-cap.all@ietf.org>, "secdir@ietf.org" <secdir@ietf.org>
Thread-Topic: secdir review of draft-ietf-ospf-encapsulation-cap-06
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Date: Tue, 19 Sep 2017 08:15:08 +0000
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Subject: Re: [secdir] secdir review of draft-ietf-ospf-encapsulation-cap-06
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From: rraszuk@gmail.com [mailto:rraszuk@gmail.com] On Behalf Of Robert Raszuk


Please replace AS with Administrative Domain.
[Bruno] I replaced AS with “OSPF domain” as indeed, AS is a BGP term rather than an OSPF one. And as you note, in some cases, the AS and the IGP domain may be different. Thanks.


If I have three ASes there should be no artificial limits prohibiting encap to my central collector.
[Bruno]
If your central collector is part of the OSPF domain of the encapsulator, there is no problem.
Otherwise, if the route to your central collector is advertised in OSPF by the decapsulator, there is no problem.
Otherwise, if the route to your central collector is advertised in BGP, then draft-ietf-idr-tunnel-encaps is probably the right tool.

--Bruno


Thx
R

On Sep 19, 2017 08:18, <bruno.decraene@orange.com<mailto:bruno.decraene@orange.com>> wrote:
> From: David Mandelberg [mailto:david@mandelberg.org<mailto:david@mandelberg.org>]
 > Sent: Monday, September 18, 2017 9:30 PM
>
 > On 09/18/2017 05:08 AM, bruno.decraene@orange.com<mailto:bruno.decraene@orange.com> wrote:
 > >   > (c) is the one that I think is worth looking into. E.g., does this new
 > >   > extension make it easier for an attacker to route a packet across AS
 > >   > boundaries, by setting a tunnel endpoint outside of the OSPF-routed network?
 > >
 > > No. The following text already prohibits even more than this:
 > >
 > > "  A tunnel MUST NOT be
 > >        used if there is no route toward the IP address specified in the
 > >        Endpoint Sub-TLV (See <xref target="EndpointTLV"/>) or if the route is
 > >        not advertised by the router advertising this Tunnel Sub-TLV."
 > >
 > > - By definition, this Tunnel Sub-TLV is advertised in OSPF i.e. from within the AS.
 > > - The text also prohibits setting a tunnel endpoint to another router within the AS.
 > >
 > >
 > > That being said, within the AS, the point "c" still applies.
 > > However, thinking twice, the probability is even more limited. Indeed, one can only advertise a
 > tunnel to itself. Assuming that the third party can't control the whole routing topology (i.e. routing
 > advertisement from most core routers), it cannot control the path followed by the tunnel. Hence it
 > would need to have monitoring capabilities on specific links that it cannot choose. (the link on
 > the path to itself).
 > > Plus this risk is not new, as the third party could already advertise the destination IP address of
 > the packets (or of the BGP Next-hop of the BGP route matching the packet destination), without
 > using any tunnel.
 > > In conclusion, although I could be wrong, I'm not seeing such new risk. (again, assuming that
 > a third party can modify the OSPF routing is a big assumption).
 > >
 > > But the discussion was useful, thanks for the comments.
 >
 > That explanation is great, thank you. I hadn't realized the implications
 > of the paragraph you quoted, when I initially read it. I'm convinced
 > that there isn't a security issue here, but it would be nice to see your
 > explanation in the document itself, if it's not already obvious to
 > anybody who knows OSPF better than I do.

I've just added the following text in the security section of my local version:
"We note that the last paragraph of <xref target="Operation"/> forbid the establishment of a tunnel toward arbitrary destinations. It prohibits a destination outside of the Autonomous System and also to other routers within the AS. This avoid that a third-party gaining access to an OSPF router be able to send the traffic to other destinations, for e.g. inspection purposes. "

Feel free to comment/propose other text.

Since I've just published -08 a few hours ago, I'll probably delay the upload of this new update.

--Bruno


 > --
 > Freelance cyber security consultant, software developer, and more
 > https://david.mandelberg.org/

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