Re: [secdir] secdir review of draft-ietf-spring-segment-routing-13

["Les Ginsberg (ginsberg)" <[e-mail]>]

Eric –

Alissa’s comments were addressed – and we have been waiting for a response from her for nearly 3 months.
See attached.

   Les


From: Eric Rescorla <[e-mail]>
Sent: Saturday, March 24, 2018 3:40 AM
To: Les Ginsberg (ginsberg) <[e-mail]>
Cc: David Mandelberg <[e-mail]>; [e-mail]; [e-mail]; [e-mail]
Subject: Re: secdir review of draft-ietf-spring-segment-routing-13

The DISCUSS on this document is being held by Alissa Cooper.
https://datatracker.ietf.org/doc/draft-ietf-spring-segment-routing/ballot/

I would suggest responding to her points (there should be an associated email thread)

-Ekr


On Fri, Mar 23, 2018 at 11:27 PM, Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>> wrote:

Hmmm...well if you look at https://datatracker.ietf.org/doc/draft-ietf-spring-segment-routing/ we see




Reviews

OPSDIR Last Call Review (of -13): Ready <https://datatracker.ietf.org/doc/review-ietf-spring-segment-routing-13-opsdir-lc-ersue-2017-12-19/>
SECDIR Last Call Review (of -13): Has Nits <https://datatracker.ietf.org/doc/review-ietf-spring-segment-routing-13-secdir-lc-mandelberg-2017-11-18/>
RTGDIR Telechat Review (of -13): Ready <https://datatracker.ietf.org/doc/review-ietf-spring-segment-routing-13-rtgdir-telechat-hardwick-2017-12-12/>




And then the SECDIR review link points to your review: https://datatracker.ietf.org/doc/review-ietf-spring-segment-routing-13-secdir-lc-mandelberg-2017-11-18/



So I don’t know what else needs to be done to clear this.



Bruno? Rob? Can you help here?



    Les



> -----Original Message-----

> From: David Mandelberg <[e-mail]<mailto:[e-mail]>>

> Sent: Friday, March 23, 2018 4:18 PM

> To: Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>;

> [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>

> Subject: Re: secdir review of draft-ietf-spring-segment-routing-13

>

> No worries about the delay. And I'm just a secdir reviewer, not an IESG member,

> so I can't do anything about a DISCUSS.

>

> On 03/23/2018 07:02 PM, Les Ginsberg (ginsberg) wrote:

> > David -

> >

> > Yes - IGP specs have this. See (for example):

> >

> > https://tools.ietf.org/html/draft-ietf-isis-segment-routing-extensions

> > -15#section-2.2.1

> >

> > If this suffices please clear your DISCUSS on the draft.

> >

> > Again, apologies for the long delay in responding - it was not intentional.

> >

> >      Les

> >

> >> -----Original Message-----

> >> From: David Mandelberg <[e-mail]<mailto:[e-mail]>>

> >> Sent: Friday, March 23, 2018 3:57 PM

> >> To: Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>;

> >> [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>

> >> Subject: Re: secdir review of draft-ietf-spring-segment-routing-13

> >>

> >> Thanks, I didn't know it was in the IGP specs. If the usage you

> >> describe would be clear to anybody using this, then I think you've

> >> fully addressed my original comment.

> >>

> >> On 03/23/2018 06:43 PM, Les Ginsberg (ginsberg) wrote:

> >>> David -

> >>>

> >>> Thanx for the very prompt response.

> >>>

> >>> If a controller (for example) is defining a SID stack for an SR

> >>> Policy, it can

> >> choose to use an  Adj-SID which is advertised as Persistent and be

> >> confident that the SID will not be reused for some other purpose no

> >> matter what happens on the owning node.

> >>>

> >>> BTW, the flag isn’t new - it has been part of the IGP specifications

> >>> for quite a

> >> long while. It just wasn't mentioned in the SR Architecture in earlier versions.

> >>>

> >>> HTH

> >>>

> >>>        Les

> >>>

> >>>> -----Original Message-----

> >>>> From: David Mandelberg <[e-mail]<mailto:[e-mail]>>

> >>>> Sent: Friday, March 23, 2018 3:17 PM

> >>>> To: Les Ginsberg (ginsberg) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>;

> >>>> [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>

> >>>> Subject: Re: secdir review of draft-ietf-spring-segment-routing-13

> >>>>

> >>>> Hi,

> >>>>

> >>>> How will the indication of persistence be used? I scanned the

> >>>> changes from -13 to -15, but I didn't notice any other text about the new

> flag.

> >>>>

> >>>> On 03/23/2018 06:34 AM, Les Ginsberg (ginsberg) wrote:

> >>>>> David -

> >>>>>

> >>>>> Apologies. It appears that I neglected to respond to this old

> >>>>> review comment.

> >>>>>

> >>>>> This was not intentional. Authors actively discussed your comment

> >>>>> promptly and we did add text in V14 of the draft to address this point:

> >>>>>

> >>>>> Please see:

> >>>>> https://tools.ietf.org/html/draft-ietf-spring-segment-routing-15#s

> >>>>> ec

> >>>>> ti

> >>>>> on-3.4

> >>>>>

> >>>>> /o  Indication whether the Adj-SID is persistent across control

> >>>>> plane/

> >>>>>

> >>>>> /      restarts.  Persistence is a key attribute in ensuring that

> >>>>> an SR/

> >>>>>

> >>>>> /      Policy does not temporarily result in misforwarding due to/

> >>>>>

> >>>>> /      reassignment of an Adj-SID./

> >>>>>

> >>>>> //

> >>>>>

> >>>>> Please let us know if this adequately addresses your comment.

> >>>>>

> >>>>> Again, apologies for the long delay.

> >>>>>

> >>>>>       Les

> >>>>>

> >>>>>    > -----Original Message-----

> >>>>>

> >>>>>    > From: David Mandelberg <[e-mail]<mailto:[e-mail]>>

> >>>>>

> >>>>>    > Sent: Thursday, November 02, 2017 10:53 AM

> >>>>>

> >>>>>    > To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>;

> >>>>> draft-ietf-spring-segment-

> >>>>>

> >>>>>    > [e-mail]<mailto:[e-mail]>

> >>>>>

> >>>>>    > Subject: secdir review of

> >>>>> draft-ietf-spring-segment-routing-13

> >>>>>

> >>>>>    >

> >>>>>

> >>>>>    > I have reviewed this document as part of the security

> >>>>> directorate's ongoing

> >>>>>

> >>>>>    > effort to review all IETF documents being processed by the IESG.

> >>>>> These

> >>>>>

> >>>>>    > comments were written primarily for the benefit of the

> >>>>> security area directors.

> >>>>>

> >>>>>    > Document editors and WG chairs should treat these comments

> >>>>> just like any

> >>>>>

> >>>>>    > other last call comments.

> >>>>>

> >>>>>    >

> >>>>>

> >>>>>    > The summary of the review is Ready with nits.

> >>>>>

> >>>>>    >

> >>>>>

> >>>>>    > This document affects routing within a trusted domain, and

> >>>>> the security

> >>>>>

> >>>>>    > considerations section adequately talks about filtering at

> >>>>> the border of a trusted

> >>>>>

> >>>>>    > domain.

> >>>>>

> >>>>>    >

> >>>>>

> >>>>>    > I do have one question about something I didn't see in the

> >>>>> document, what

> >>>>>

> >>>>>    > happens when SIDs change while packets are in transit? Here's

> >>>>> a hypothetical

> >>>>>

> >>>>>    > situation that could be bad for security, but I'm not sure

> >>>>> whether or not it could

> >>>>>

> >>>>>    > happen: 1. An internal node calculates an SR Policy and sends

> >>>>> out a packet that

> >>>>>

> >>>>>    > will eventually egress towards a BGP peer. 2. Multiple links

> >>>>> on the BGP router go

> >>>>>

> >>>>>    > down and then back up, but are allocated different PeerAdj

> >>>>> SIDs than they had

> >>>>>

> >>>>>    > before. 3. The packet reaches the BGP router, but egresses to

> >>>>> the wrong BGP

> >>>>>

> >>>>>    > peer because the original PeerAdj SID is now mapped to a

> >>>>> different PeerAdj

> >>>>>

> >>>>>    > segment.

> >>>>>

> >>>>>    >

> >>>>>

> >>>>>    > --

> >>>>>

> >>>>>    > Freelance cyber security consultant, software developer, and

> >>>>> more

> >>>>>

> >>>>>    > https://david.mandelberg.org/

> >>>>>

> >>>>

> >>>>

> >>>> --

> >>>> Freelance cyber security consultant, software developer, and more

> >>>> https://david.mandelberg.org/

> >>

> >>

> >> --

> >> Freelance cyber security consultant, software developer, and more

> >> https://david.mandelberg.org/

>

>

> --

> Freelance cyber security consultant, software developer, and more

> https://david.mandelberg.org/

--- Begin Message ---

Alissa:

Hi!

Any thoughts on the update to this document?

Thanks!

Alvaro.


On December 20, 2017 at 6:18:13 PM, Les Ginsberg (ginsberg) ([e-mail]<mailto:[e-mail]>) wrote:

Alissa -

Thanx for the review.
V14 has been published and it attempts to address the Security concerns raised by you and others.
Look forward to your feedback.

Inline.

> -----Original Message-----
> From: Alissa Cooper [mailto:[e-mail]<mailto:[e-mail]>]
> Sent: Wednesday, December 13, 2017 10:42 AM
> To: The IESG <[e-mail]<mailto:[e-mail]>>
> Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>;
> [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
> Subject: Alissa Cooper's Discuss on draft-ietf-spring-segment-routing-13:
> (with DISCUSS and COMMENT)
>
> Alissa Cooper has entered the following ballot position for
> draft-ietf-spring-segment-routing-13: Discuss
>
> When responding, please keep the subject line intact and reply to all email
> addresses included in the To and CC lines. (Feel free to cut this introductory
> paragraph, however.)
>
>
> Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
>
>
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-spring-segment-routing/
>
>
>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> I ended up reading draft-ietf-6man-segment-routing-header in tandem with
> this document, and I have a question arising out of that. The trust model for
> SRv6 outlined in this document appears to be one of reliance on the fact that
> an SRH will only ever be inserted and appear within a single administrative
> domain.
> But Section 5.2.2 of draft-ietf-6man-segment-routing-header talks about an
> SRH being inserted by a device outside of the segment routing domain.
> Which is correct? I think this is an important question because the whole
> trust model for the SR information seems to rely on out-of-band trust
> between participating nodes.
>
> I also think this is important because there is no discussion in this document
> of the impact of the inclusion of the SR metadata on the fingerprinting of the
> device that inserted it. Section 5.1.4 of draft-ietf-6man-segment-routing-
> header sort of alludes to this but seems to equate the capabilities of an
> active attacker (who can conduct a traceroute) with a passive attacker who
> could passively collect topology/fingerprinting information simply by
> observing SRHes flowing by on the network. If the limitation to a single
> administrative domain is meant to prevent such a passive attack (not sure if
> that is really true, but perhaps the document assumes it?), that's another
> reason that the existence of such a limitation needs to be clarified.
>
>
[Les:] We share a common concern regarding trust issues. The architecture draft speaks to the default policy of only allowing trusted sources to insert SRH.
The 6man draft currently discusses exceptions under the protection of authentication. I don’t see that as a contradiction.
The risk/reward of allowing such exceptions can (and should) be discussed in the review of the 6man draft, but I am not convinced the architecture draft needs to speak to this since it is a clearly stated exception to the base trust model.

The point that SR is intended to operate within a trusted domain has been clarified/reemphasized in the Security section changes.

Les



> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
>
> Per my DISCUSS comment, I think this document needs to include some
> considerations concerning the additional metadata that SRv6 adds to the
> packet.
> This has implications not just for passive observers but also for any node that
> logs the SRH.
>

--- End Message ---