Re: [TLS] Industry Concerns about TLS 1.3

Yaron Sheffer <> Fri, 23 September 2016 19:51 UTC

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To: BITS Security <>, Watson Ladd <>, "Ackermann, Michael" <>
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From: Yaron Sheffer <>
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Date: Fri, 23 Sep 2016 22:51:45 +0300
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Subject: Re: [TLS] Industry Concerns about TLS 1.3
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>> What exactly is the problem you are concerned with? As I've pointed
>> out previously one can still log the contents of TLS protected
>> connections: you do this at the client, or with an intercepting
>> proxy. What information does this not get you that you need on the
>> network?
> For enterprises using Content Delivery Networks, the TLS session from
> the browser ends at the edge server in the Content Delivery Network.
> The session that the enterprise sees is completely different:
> different IP's and ports, different TLS session, different
> application layer content because of caching, different network
> behavior (like packet drops and retransmissions).  If some
> infrastructure component in the data center is causing a problem, a
> trace on the browser side is blind to that.  An additional problem is
> that Microsoft does not allow logging of ephemeral keys in their
> browser.
>> From the time a packet enters a data center, it is travelling
>> through routers, switches, firewalls, load balancers, web servers,
>> app servers, middleware servers, and possibly hitting a mainframe,
>> all TLS encrypted for many enterprises.  Frequently, source and
>> destination IP's are NAT'ed multiple times, so there is no visible
>> relationship between the packet that enters the data center and the
>> same call at deeper layers of the infrastructure.  Any one of these
>> infrastructure nodes could be the cause of a problem.  The way to
>> isolate the fault domain of a problem is to take a packet trace at
>> each tier of the application infrastructure and look at the
>> application layer data in a decrypted trace in order to find the
>> transaction that is failing.

You are implicitly suggesting to remove perfect-forward-secrecy as soon 
as a TLS flow is created by the CDN. However these packets will still be 
traveling over the public Internet and/or "private" (leased, not really 
private) MPLS VPNs, where we KNOW that government agencies are 
eavesdropping and recording network flows to keep for years ahead. In 
other words, even when the TLS flow enters "your" network, you and your 
customer are still at risk from pervasive monitoring.