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Re: [Acme] dns-01 challenge limitations

Michael Richardson <mcr@sandelman.ca> Fri, 11 September 2020 19:45 UTC

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From: Michael Richardson <mcr@sandelman.ca>
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Date: Fri, 11 Sep 2020 15:45:28 -0400
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Subject: Re: [Acme] dns-01 challenge limitations
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Ilari Liusvaara <ilariliusvaara@welho.com> wrote:
    >> For now, this is for many ACME clients a manual step. If you run your
    >> authoritative DNS service locally in your network, perhaps you could
    >> look into any options for automatically update the zone content.

    > I think the current best way is to have _acme-challenge be a CNAME
    > pointing to zone served by single master with no slaves that accepts
    > DNS UPDATE with TSIG HMAC-SHA256 authentication for ACME client to
    > update the records.

That's precisely what I do.
I do it because bind9 does not do well when zones are managed by updates as
well as manual edits.   So I CNAME to a single (sub)zone where it is all
updates.

    > The single master is more than reliable enough for the purpose (as
    > there should be donzens of retries spread over time for renewal before
    > the certificate expires) and eliminates the propagation times.

I do have multiple masters, and I mean to program a query to all NS to see if
the update has propogated, but for now, I "sleep(30)", which is definitely
sub-optimal in the best cases, and a failure if there are problems.
So far, it works great.

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

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