Subject: [Acme] PR: allow challenge retries

From: Hugo Landau <[email-masked]>
Date: Sun, 9 Apr 2017 09:47:56 +0100

This is a proposed change to enable challenges to be retried.

https://github.com/ietf-wg-acme/acme/pull/292

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From: Richard Barnes <[email-masked]>
Date: Mon, 17 Apr 2017 18:40:06 -0400

Hey Hugo,

Thanks for the PR.  Jacob and I chatted a bit about this, and wanted to
propose a slightly different approach:

https://github.com/ietf-wg-acme/acme/pull/297

What do you think?  Others on the list have any thoughts?

Thanks,
--Richard

On Sun, Apr 9, 2017 at 4:47 AM, Hugo Landau <[email-masked]> wrote:

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From: Hugo Landau <[email-masked]>
Date: Tue, 18 Apr 2017 06:28:02 +0100

>    [1]https://github.com/ietf-wg-acme/acme/pull/297

This looks mostly OK.

My only concern is that it's not clear how a client can determine when a
server is still attempting automatic retries. Is this to be detected via
the absence of the Retry-After header? Something more explicit might be
nicer (and less susceptible to misimplementation).

Also, is each automatic retry to result in an error being appended if
unsuccessful? This could get quite spammy depending on how many times a
server repeats verification. Possibly amendment of the problem document
format to add a repeat count (in the spirit of "last message repeated N
times") might be desirable. Or that might be my usual overengineering.

Hugo Landau

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From: Richard Barnes <[email-masked]>
Date: Thu, 27 Apr 2017 15:35:22 -0400

> nicer (and less susceptible to misimplementation).

The idea is that as long as the challenge status is still "pending", the
server is still retrying.  Once it gives up, it marks the challenge as
"invalid".

> times") might be desirable. Or that might be my usual overengineering.

Yeah, I'm not to worried about spamminess here.  The server can always
limit the number of retries.

--Richard

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From: Hugo Landau <[email-masked]>
Date: Fri, 28 Apr 2017 17:01:09 +0100

>    server is still retrying.  Once it gives up, it marks the challenge as
Bad idea. This prevents a server from supporting retries unless it
commits to continuously reverifying the challenge itself. A server may
want to allow retries but require a client to retrigger it (which is the
most consistent with the initial behaviour of challenges anyway).

Options here would be to add a new status, or an additional boolean
field indicating whether proactive retries are being made.