Re: [dmarc-ietf] [rfc-i] Question about changes introduced by erratum
Damian Lukowski <rfc@arcsin.de> Sat, 21 March 2020 23:23 UTC
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From: Damian Lukowski <rfc@arcsin.de>
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Subject: Re: [dmarc-ietf] [rfc-i] Question about changes introduced by erratum
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Hello DMARC working group, I am going through the changes between RFC7601 and RFC8601 and try to understand the implication of the change introduced by erratum 5435. The new resinfo definition uses 1*propspec, that is, by my understanding of [1] and [2], potentially multiple consecutive propspecs without obvious delimiters. The beginning of a ptype and the end of a pvalue have no mandatory CFWS, so from my understanding, a verifier could construct a valid authres-header-field that is cumbersome to parse. I will refer to the "ptype.property" part of a propspec as its "key". The spf method defines smtp.helo and smtp.mailfrom. RFC8601, RFC7601 and RFC7001 have only examples of the form smtp.mailfrom=domain-name. However, RFC7208 shows a local-part@domain-name form in [3], so I must assume a parser for an RFC8601 resinfo needs to recognize both forms. So consider > spf=pass smtp.mailfrom=x.y.zsmtp.helo=a.b This is "clearly" - smtp.mailfrom = x.y.z - smtp.helo = a.b It seems that a 10 character lookahead is sufficient, as long as we are in the domain-name case. However, with > spf=pass smtp.mailfrom=x.y.zsmtp.helo=a.b@c.de the previous "cut" between x.y.z and smtp.helo is no longer valid, as we have a single smtp.mailfrom with - "x.y.zsmtp.helo=a.b" as the local-part, and - "c.de" as the domain-name. I see some issues: 1. The lookahead for the "@" is unbounded. 2. RFC8601 does not (that I am aware of) prohibit duplicate keys among multiple propspecs. They may be either completely redundant, i.e. "k1=v1 k1=v1 ..." or contradicting/overwriting each other, i.e. "k1=v1 k1=v2 ...". Without a delimiter between the propspecs, it seems even impossible to parse them unambiguously. 3. I believe that a parser for potentially non-separated propspecs would be ugly. Did I overlook or misunderstand something? Would you consider a parser RFC8601 compliant if it was only able to parse the "benevolent" forms of an authres header? Regards Damian [1] https://www.rfc-editor.org/rfc/rfc5234 [2] https://www.rfc-editor.org/rfc/rfc5234#section-3.1 [no "implicit specification of linear white space"] [3] https://www.rfc-editor.org/rfc/rfc7208#section-9.2 > But in answer to your question: dmarc@ietf.org, since RFC8601 is from the dmarc WG. [...] >> I have a question about a change in an RFC introduced by a specific >> erratum (5435). Is this the right list to ask such question?
- Re: [dmarc-ietf] [rfc-i] Question about changes i… Damian Lukowski
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… John Levine
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… Damian Lukowski
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… John Levine
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… Damian Lukowski
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… John Levine
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… Damian Lukowski
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… John R Levine
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… Damian Lukowski
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… John R Levine
- Re: [dmarc-ietf] Errors in RFC 8601, was Question… Damian Lukowski