Re: [Anima] [lamps] Long-lived certificates, but frequently renewed certificates

Michael Richardson <mcr+ietf@sandelman.ca> Sat, 20 March 2021 18:00 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Eliot Lear <lear@cisco.com>, Nico Williams <nico@cryptonector.com>, Toerless Eckert <tte@cs.fau.de>, LAMPS <spasm@ietf.org>, netconf@ietf.org, anima@ietf.org
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Subject: Re: [Anima] [lamps] Long-lived certificates, but frequently renewed certificates
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Eliot Lear <lear@cisco.com> wrote:
    >> On 18 Mar 2021, at 19:58, Michael Richardson <mcr+ietf@sandelman.ca> wrote:
    >>
    >> A pity that EST (and I think SCEP, but I haven't read it all), just returns
    >> the resulting certificate, and not something more useful, like a JSON dict
    >> that includes the certificate.
    >>
    >> RFC7030 has a 202, Retry-After, which could be used to tell the holder to
    >> go away and come back later, but the intended use is not to say not now,
    >> but rather, "I'm working on it".

    > This is definitely a problem in a number of deployments.  One aspect
    > that people have to deal with is not so much the gross expiry time, but
    > when it is convenient to take a risk of moving to a new cert.  Of
    > course you’re going to want to make that operation as bullet-proof as
    > possible, but in some environments they want multiple levels of
    > resilience.  So scheduling does become an issue.

    > The big question is- who does the scheduling?  Is it the end system?
    > Is it the EST server?  Who knows when “convenient” is?  Probably the
    > answer is “both”.

It has to be a three phase commit, and it needs to be initiated from the EST server.
1) send out new identities and trust anchors, but continue to initiate with
   old ones.
2) do a fire drill with new identities, testing responders
3) switch to new identities, mark old identities to be removed

I really like the netconf solution.
I think that putting the EST server in charge of collecting new CSRs, and
delivering new certificates is the right way.  I argued for this back when we
were doing 6tisch-minimal-security:   on a challenged network, a stampeding
herd of elephants is very undesireable.

I would like brski-async-enroll to consider
   https://datatracker.ietf.org/doc/draft-ietf-netconf-sztp-csr/?include_text=1
as being the collection protocol between registrar agent and pledge.

--
Michael Richardson <mcr+IETF@sandelman.ca>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide