Re: [TLS] SNI and Resumption/0-RTT

mrex@sap.com (Martin Rex) Fri, 21 October 2016 14:35 UTC

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To: Ilari Liusvaara <ilariliusvaara@welho.com>
Date: Fri, 21 Oct 2016 16:35:12 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
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Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] SNI and Resumption/0-RTT
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Ilari Liusvaara wrote:
> On Fri, Oct 21, 2016 at 11:41:59PM +1100, Martin Thomson wrote:
>> On 21 October 2016 at 19:55, Ilari Liusvaara <ilariliusvaara@welho.com>; wrote:
>>> Of course, defining the "same certificate" is
>>> way trickier than it initially seems
>> 
>> Not if you think simplistically: same octets in EE ASN1Cert
>> in both handshakes.
> 
> Such behaviour would run into problems with certificate renewal.

Just the opposite.  You definitely want full handshake on
certificate renewal.

I don't know how common it is in TLS servers (and TLS clients) to
allow replacing of TLS certificates in "full flight".  I implemented
this in ours about 10 years ago, and I'm flushing the session cache
after loading of the new/updated cert, so that every new handshake
will result in a full handshake rather than session resume (ongoing
connections continue to use the old/previous certificate until
closed by the application).

-Martin