Re: [TLS] chairs - please shutdown wiretapping discussion...

Stephen Farrell <stephen.farrell@cs.tcd.ie> Mon, 10 July 2017 22:34 UTC

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To: Russ Housley <housley@vigilsec.com>
Cc: "Polk, Tim (Fed)" <william.polk@nist.gov>, IETF TLS <tls@ietf.org>
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From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [TLS] chairs - please shutdown wiretapping discussion...
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On 10/07/17 23:32, Russ Housley wrote:
> Stephen:
> 
>>>>> 
>>>>>> And to avoid a repeat of Russ' failed justification, many
>>>>>> protocols use and depend on TLS where the entity
>>>>>> controlling the TLS server private key materials is not the
>>>>>> higher layer sender or receiver, so all four points in the
>>>>>> definition in 2804 are fully met by your wiretapping
>>>>>> scheme.
>>>>> 
>>>>> It is clear that you do not agree with the reasoning that I
>>>>> posted on Friday.  Some people do, and clearly, others do
>>>>> not.
>>>>> 
>>>>> So, I failed to convince you.  However, you have also failed
>>>>> to convince me that the proposal is wiretapping under the
>>>>> definition in RFC 2804, Section 3.
>>>> 
>>>> Consider SMTP/TLS. Where one MTA on the path supports this. Say
>>>> it's one operated by an anti-spam company for example. That is
>>>> clearly not the sender nor recipient.
>>>> 
>>>> That meets all 4 points in 2804, right?
>>> 
>>> You are pointing to email.  Some MTAs will use SMTP over TLS, but
>>> many others do not.  It would be great if they all do, especially
>>> for the authentication.  In your response you are talking about
>>> an email system that has been using plaintext for ages, and you
>>> are trying to apply hop-by-hop a mechanism to the delivery.
>>> Then, you are saying that the sender and receiver have
>>> confidentiality expectations that are being violated.  I do not
>>> buy it.
>> 
>> See [1].
>> 
>> Those show nearly 90% of mails being encrypted with TLS now.
>> 
>> In many mail deployments there will be an added hop e.g. for
>> anti-spam (we do that here in tcd) to an outside party.
>> 
>> While not 100% of mail is encrypted with TLS on all hops, much is.
>> (And the UTA WG are developing MTA-STS to try improve that.)
>> 
>> If one of those external parties implements your scheme then mail
>> senders and receivers will not know and that real TLS application
>> meets the 2804 definition for lots and lots and lots of emails.
>> 
>> Hence, 2804 applies here and the standards-track label ought be
>> removed.
>> 
>> S.
>> 
>> [1] https://www.google.com/transparencyreport/saferemail/
> 
> I'm glad that TLS is being used to protect email delivery.
> 
> I do not see how this changes the expectation discussed in RFC 2804,
> Section 3, Item number 3.
> 

Talk to our (tcd.ie) or gmail's mail admin folks. Their
expectations count too. (Or are we against enterprise
requirements or something? ;-)

S.

> Russ
> 
> 
>