Re: [perpass] Fwd: New Version Notification for draft-fenton-smtp-require-tls-01.txt
Jim Fenton <fenton@bluepopcorn.net> Thu, 18 February 2016 03:43 UTC
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To: Yakov Shafranovich <yakov@shaftek.biz>
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From: Jim Fenton <fenton@bluepopcorn.net>
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Date: Wed, 17 Feb 2016 19:42:59 -0800
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Subject: Re: [perpass] Fwd: New Version Notification for draft-fenton-smtp-require-tls-01.txt
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On 2/17/16 2:13 PM, Yakov Shafranovich wrote: > Some minor comments: > > Section 1: > "It also requires that the SMTP server advertise > that it also supports REQUIRETLS, in effect promising that it will > honor the requirement to require STARTTLS and REQUIRETLS for all > onward transmissions of messages specifying that requirement." > " > > The part about "promising" does not seem to go together with the > optional parameter in section 2 about onward transmission. If you are saying that the statement in Section 1 is incomplete because it does not say that the server must honor the requirements of the optional (server authentication) parameter as well, I agree. > > Section 3.1 - tagging: > I am wondering if an email header should be defined to carry this > data, which would also allow for auditing by the receiver. Sort of > similar to the SPF/DKIM headers used today. One could be defined, but that would be a message format extension (RFC 5322) rather than a mail transport extension (RFC 5321). It would then be necessary to define under what circumstances the new header field would be moved into the transport realm. I thought it to be more straightforward to consider REQUIRETLS to be an aspect of the message envelope (like the envelope-to and envelope-from addresses) rather than a header field. > > Section 3.4 - delivery: > It is unclear what "delivery" means here, especially considering that > SMTP may relay messages to another server, perhaps reference RFC 5598? > Also, the parts in section 1 and the optional parameter in section 2 > should play together with this, perhaps by requiring TLS in IMAP, etc. > or not. Either way, this may need clarification. I have been trying to void "boiling the ocean" by constraining this feature to SMTP. From the context, it should be clear that by delivery I was referring to protocols such as IMAP and POP, although webmail applies here as well. Are you suggesting that this requirement should be a MUST rather than the SHOULD I proposed? > > Section 5: > What are the actual added codes? I believe 5.7.10 already exists. 5.7.10 does exist, but seems to have the right semantics ("Encryption needed"). The others will need to be allocated and since they are numeric codes I didn't presume to define them myself. > > Section 6: > Maybe reference RFC 4949 for terminology? I'll have a look at 4949. > > One other comment - perhaps some sort of limiting digital signatures > for headers only like DKIM can be employed by the receiving MTA to > certify that the receipt and transmission was effective? I am thinking > along the lines of Received headers or DKIM headers, which would allow > traceability. This seems to be a separate feature - authenticated return receipts. This might be useful, but I don't think it belongs here. I would hope that MTAs would add information about REQUIRETLS to their Received: header fields, much as they do about the use of TLS for messages they receive, but I haven't worked out quite how to specify that yet. > Yakov Thanks for your review! -Jim
- [perpass] Fwd: New Version Notification for draft… Jim Fenton
- Re: [perpass] Fwd: New Version Notification for d… Yakov Shafranovich
- Re: [perpass] Fwd: New Version Notification for d… Jim Fenton
- Re: [perpass] Fwd: New Version Notification for d… Yakov Shafranovich