Iljitsu,

It is not an implementation choice, it is by design. If a signed object does 
not validate (based on whatever reason not just expiration), it is like if did 
not existed.

I guess your point is covered.

Roque

Sent from my HTC

----- Reply message -----
From: "Iljitsch van Beijnum" <iljit...@muada.com>
To: "Sandra Murphy" <sa...@tislabs.com>
Cc: "i...@ietf.org wg" <i...@ietf.org>, "g...@apnic.net" <g...@apnic.net>, 
"sidr@ietf.org" <sidr@ietf.org>
Subject: [Idr] Levels of BGPsec/RPKI validation, was: Re: [sidr] wglc for 
draft-ietf-sidr-bgpsec-protocol-11
Date: Tue, Apr 28, 2015 20:02

On 28 Jan 2015, at 23:38, Sandra Murphy <sa...@tislabs.com> wrote:

> idr folk, your attention and comments would be appreciated as well.

Since you ask...

I'm sending this to both idr and sidr as I think this needs broader input than 
just sidr. (And it seems I'm no longer on the sidr list.)

I read draft-ietf-sidr-bgpsec-protocol-11 and 
draft-lepinski-bgpsec-overview-00.txt as well as RFC 6483.

I think what's lacking here is any discussion of what happens when certificates 
etc expire. Please stay with me for a bit:

RFC 6483 talks about RPKI route validation, which suggests that there are three 
possible states:

valid
unknown
invalid

where valid is preferred over unknown and unknown over invalid, and:

"It is a matter of local routing policy as to whether routes with an "invalid" 
validity state are considered to be ineligible for further consideration in a 
route selection process."

Actually, I think the only reasonable approach is to filter out invalids and 
prefer valids over unknowns. The important part here is that if there's a ROA 
for 193.0.0.0/21 and then someone announces a more specific like 193.0.7.0/24, 
that /24 will be "invalid", so even in partial deployment RPKI users are 
protected against malicious or accidental more specifics. But if invalids are 
accepted, even with a very low preference, then they still get to divert 
traffic.

So far, so good.

But now what if a certificate expires? We know from the web that this is 
extremely common. If an expired certificate means the prefixes involved are 
marked invalid, this means that filtering invalids becomes very problematic: 
not only will prefixes randomly drop off the net as people forget to generate 
or install certificates or RPKI caches get stale, but if things get really bad 
the resulting lack of connectivity makes it impossible to correct the problem...

So what we need is for expired certificates to make the affected prefixes 
revert to unknown rather than invalid. Turns out, that's what happens today:

http://mailman.nanog.org/pipermail/nanog/2014-December/071907.html

However, unless this is specified in one of the related documents other than 
the three mentioned above, this seems to be an implementation choice.

I think the above issue needs to be discussed in an update of RFC 6483 or in 
one of the BGPsec documents.

And there's probably a bit more to think about: wouldn't it make sense to be 
able to filter on the signature algorithm at some point during the transition 
from one algorithm to the next? Or to be able to filter on "expired" 
explicitly? A binary valid/invalid isn't enough. Valid/unknown/invalid is 
workable, but maybe four or five levels is even better.

(And have a look at how this works in practice: 
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/command/irg-cr-book/bgp-m1.html
 search for PEX.)

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