Re: [Acme] Last Call: <draft-ietf-acme-email-smime-08.txt> (Extensions to Automatic Certificate Mana

Sebastian Nielsen <> Thu, 25 June 2020 21:41 UTC

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From: Sebastian Nielsen <>
To: 'S Moonesamy' <>, 'Alexey Melnikov' <>
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Date: Thu, 25 Jun 2020 23:40:43 +0200
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Subject: Re: [Acme] Last Call: <draft-ietf-acme-email-smime-08.txt> (Extensions to Automatic Certificate Mana
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1: Of course DKIM can be used to validate the authenticity of the email such
as it has been sent from the specified domain.

2: Validation response messages should NOT be forwarded! Normally, you would
send a response message like from to
Of course, if is in full control of all email servers, they
can easily do the validation at the leaf server, and then
forward the email message to a internal server for SMIME issuance, for
example by adding a encrypted and signed header with the validation, or
communicating out-of-band - for example with a MySQL server, that the
message X is propely SPF and DKIM validated.

The type of forwarding SPF don't work with, would be if was forwarded to lets say then if I send a validation reponse to from , validation would fail
@ GMAIL when they receive the message from which is a server
not on my authorization list.

And a CA running an email server that forwards to an server they are not in
full control of, is a HUGE security risk for SMIME issuance - unless they
have proper agreements in place - for example a subCA that forwards their
validations to the main CA, but still want a "branded" email adress for
their ACME validations - but then their agreements could easily include that
the subCA should do the validations at the leaf server, and then add
information to the email that allows the main CA to see that SPF and DKIM
was propely validated.
Or include the client IP in the message, signed securely, so the main CA can
validate SPF.

-----Ursprungligt meddelande-----
Från: <> För S Moonesamy
Skickat: den 25 juni 2020 21:59
Till: Alexey Melnikov <>
Ämne: Re: [Acme] Last Call: <draft-ietf-acme-email-smime-08.txt> (Extensions
to Automatic Certificate Mana

Hi Alexey,
At 11:57 AM 25-06-2020, The IESG wrote:
>The IESG has received a request from the Automated Certificate 
>Management Environment WG (acme) to consider the following document: - 
>'Extensions to Automatic Certificate Management Environment for end
>    user S/MIME certificates'
>   <draft-ietf-acme-email-smime-08.txt> as Proposed Standard
>The IESG plans to make a decision in the next few weeks, and solicits 
>final comments on this action. Please send substantive comments to the

In Section 3.1, there is the following in Point 3 and 5: "The message MAY
contain Reply-To header field."  Is the duplication a mistake?

Point 6 states that its purpose is to "prove authenticity of a challenge
message".  How does DKIM prove authenticity [1]?

Why is there a requirement that the message has to pass DMARC validation?
Has forwarding been taken into account [2]?

S. Moonesamy

1. Please see Section 5.4 of RFC 6376.
2. That does not work well with SPF. 

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