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Re: [Acme] Remove the hyphen from the acceptable character set for _acme-challenge TXT records.

Michael Richardson <mcr+ietf@sandelman.ca> Wed, 25 November 2020 22:37 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Mark Tomlin <Mark@mimocad.io>, acme@ietf.org
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Date: Wed, 25 Nov 2020 17:37:06 -0500
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Subject: Re: [Acme] Remove the hyphen from the acceptable character set for _acme-challenge TXT records.
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Mark Tomlin <Mark@mimocad.io> wrote:
    > I have a bit of a feature request for you all. It's actually to remove
    > the hyphen from the TXT records to make it easier to copy and paste into a
    > DNS server record. Here's my scenario. I ran the following command on my
    > server (Ubuntu 20.04) that as you can see has cerbot on it and a large
    > number of domains to cover.

It is annoying, and I've run into the same problem as well.
The challenge is a base64url encoded (RFC4648) nonce.  It is preferred by web
programmers because it does not use + or /, which are special in URLs.
The base64 alphabet doesn't use -, but does use + and /, but which would
copy and paste better.

The format and contents of the nonce are not mandated by RFC8555, so
LetsEncrypt change this in many different ways.
It would be a unilateral decision on the ACME server only.

I actually think that BASE32 encoding would probably better: you could
probably write a pull-request to the letencrypt code base to do this.
I don't know how they would feel about this, but it would be worth learning.

    > Please deploy a DNS TXT record under the name
    > _acme-challenge.mimocad.io with the following value:

    > 6-K6v7VjtVpGhJk4d6Zx8qxsg6JFUZbGnnr-bDpKpSc

What annoyed me here when renewing a system with 10 different aliases is that
I don't know when I've gotten to the last one.  I should be shown all
10 at the same time, so that I can put them all in place, and then reload the
zone.  Instead, I count (badly), reload the zone too late or too soon...
Even better if they add the entire DNS presentation lines so that
I could copy&paste the entire set.
But, again, this is a client code issue, and not a protocol issue.

I have since bit the bullet and gotten nsupdate to do the right thing,
and it now autorenews on it's own, as Ghod intended.

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

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