Re: [dmarc-ietf] ESC for Failed DMARC Validation

Дилян Палаузов <dilyan.palauzov@aegee.org> Fri, 02 August 2019 20:19 UTC

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To: "Murray S. Kucherawy" <superuser@gmail.com>
Cc: IETF DMARC WG <dmarc@ietf.org>, Alessandro Vesely <vesely@tana.it>
Date: Fri, 02 Aug 2019 20:19:26 +0000
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Subject: Re: [dmarc-ietf] ESC for Failed DMARC Validation
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Hello Murray,

ESC X.7.20, X.7.21 and X.7.22 are glued to return code 550, while I propose an ESC, that works also with 250.

Apart from this, X.7.20 and X.7.21 cannot be used instead of the proposed X.7.30:

If a site sees a valid DKIM signature, and previous experience with the domain signing DKIM leads to increased trust in
this domain, then the signature is acceptable, but it does not have to align with the From: address.

With X.7.22:

      Description:        This status code is returned when a message
                          contains one or more passing DKIM
                          signatures, but none are acceptable because
                          none have an identifier(s)
                          that matches the author address(es) found in
                          the From header field.  This is a special
                          case of X.7.21. (This violates the advice
                          of Section 6.1 of RFC 6376.)

If “none have an identifier that matches the author address found in the From header field” means, that the DKIM part of
DMARC fails, then this ESC can be recommended by the DMARC specification to signal to the sender, that the DKIM
implementations of sender and receiver disagree, as a light substitute to the failure reports.

Greetings
  Дилян


On Fri, 2019-08-02 at 13:01 -0700, Murray S. Kucherawy wrote:
> On Fri, Aug 2, 2019 at 10:52 AM Дилян Палаузов <dilyan.palauzov@aegee.org> wrote:
> > I mean an enhanced status code, as at 
> > https://www.iana.org/assignments/smtp-enhanced-status-codes/smtp-enhanced-status-codes.xhtml .
> 
> RFC7372 registered some for exactly this purpose (though not specific to DMARC).  Its Security Considerations section talks about the privacy risks.
> 
> I don't know if they're actually in use.
> 
> -MSK
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