Re: [TLS] analysis of wider impact of TLS1.3 replayabe data

Colm MacCárthaigh <colm@allcosts.net> Mon, 14 March 2016 18:40 UTC

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Date: Mon, 14 Mar 2016 11:40:52 -0700
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From: =?UTF-8?Q?Colm_MacC=C3=A1rthaigh?= <colm@allcosts.net>
To: Subodh Iyengar <subodh@fb.com>
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Subject: Re: [TLS] analysis of wider impact of TLS1.3 replayabe data
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On Mon, Mar 14, 2016 at 11:27 AM, Subodh Iyengar <subodh@fb.com>; wrote:

> Currently the only way to express retry behavior in HTTP is by the method
> (i.e. whether it is idempotent or not), which as you pointed out may have
> unfortunate side effects, since it is not explicit. The proposal (at least
> one of them) is to add an explicit way to express retry safety in HTTP as
> an additional request property similar to method. This can be used by the
> agent (browser or http library) to decide whether or not to use 0-RTT for
> the http data. I'll link to it in this thread once it's posted.
>

Just on this; if you want to be sure of idempotency on the server side; the
best answer to is might be to intentionally send the data 2+ times at the
protocol level.  If the action really is idempotent, then the repeat will
be safe. Doing so as a matter of course builds up anti-bodies against any
nascent idempotency bugs.

Tackling it with new verbs and declarations is probably doomed to "I
thought it /was/ idempotent".

-- 
Colm