Re: [Extra] draft-ietf-extra-imap4rev2-04 review

["Chris Newman" <[e-mail]>]

On 26 Mar 2019, at 15:13, Ned Freed wrote:
>> On 25 Mar 2019, at 13:04, Timo Sirainen wrote:
>> >> 3.4.  Logout State
>> >>
>> >
>> >>    A server MUST NOT unilaterally close the connection without
>> >> sending
>> >>    an untagged BYE response that contains the reason for having 
>> done
>> >> so.
>> >
>> > Also already in RFC 3501, but this MUST NOT has to be violated
>> > sometimes. For example otherwise it would allow client to FETCH a
>> > large message and keep reading it very very slowly over days, and
>> > server wouldn't be allowed to disconnect it, because it can't send 
>> BYE
>> > in the middle of the large mail literal.
>
>> Another example is if a client gets hung up (or goes silently 
>> offline)
>> during a TLS negotiation. The server has to eventually timeout the
>> connection but it would be semantically wrong to send a "* BYE" since
>> there's no data channel. One case where this happened was when our 
>> SSL
>> stack dropped support for an SSLv2-compatible hello (allowed by RFC
>> 6176), but some very old client kept sending such a hello (prohibited 
>> by
>> RFC 6176). Incidentally, SSLv2 is completely incompatible with SSLv3 
>> so
>> the client sends something that's not sufficient to complete an SSLv3
>> packet so both ends get stuck waiting until one side hangs up.
>
> There was a suggestion (I think) during the meeting that this should 
> be handled
> by sending the TLS equivalent of "* BYE". Which sounds fine in theory, 
> but as
> said at the time, I'm skeptical that many/most TLS implementations 
> provide
> implementors with the means to conveniently do that.

I didn't hear such a suggestion. I made the observation that a wedged 
TLS negotiation is a scenario where sending "* BYE" shouldn't be done. 
It was suggested that example be mentioned in the document. I did not 
mention the fact that TLS has it's own alert syntax that could be used 
instead of "* BYE" -- I agree discussing that would be a bad idea.

		- Chris