[TLS] ESNI padding

Rob Sayre <sayrer@gmail.com> Tue, 22 October 2019 21:00 UTC

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From: Rob Sayre <sayrer@gmail.com>
Date: Tue, 22 Oct 2019 14:00:08 -0700
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To: Ben Schwartz <bemasc@google.com>
Cc: Eric Rescorla <ekr@rtfm.com>, "TLS@ietf.org" <tls@ietf.org>
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Subject: [TLS] ESNI padding
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I thought this discussion was important enough to surface with a new topic.

I can see why the server might need to set a minimum in the DNS record, but
I find it likely irrelevant, since I intend to effectively max out the
padding allowed within a packet.

thanks,
Rob

On Tue, Oct 22, 2019 at 11:52 AM Rob Sayre <sayrer@gmail.com>; wrote:

> On Tue, Oct 22, 2019 at 11:45 AM Ben Schwartz <bemasc@google.com>; wrote:
>
>> On Tue, Oct 22, 2019 at 2:29 PM Rob Sayre <sayrer@gmail.com>; wrote:
>> > It seems to me that the client is in the best position to set the
>> padding, so I’m not sure why there is anything in the DNS record.
>>
>> Strongly disagree.  If one IP address hosts two domains, short.example
>> and longlonglonglonglonglonglonglong.example, a client of
>> short.example has no SNI privacy unless they pad up to the length of
>> the longer name.  The client can't know to do this unless the DNS
>> record says so.
>
>
> Well, I am not sure we are disagreeing so strongly. I want to pad
> everything up to 260 since the ClientHello will still fit in one packet. I
> think it would be ok to send a minimum length in the DNS record.
>
>>