Re: [tram] Allow TURN to forward inbound connectivity checks without permission

Brandon Williams <brandon.williams@akamai.com> Tue, 20 March 2018 15:02 UTC

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To: Simon Perreault <sperreault@jive.com>, Nils Ohlmeier <nohlmeier@mozilla.com>
Cc: tram@ietf.org, Cullen Jennings <fluffy@cisco.com>, Eric Rescorla <ekr@rtfm.com>
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From: Brandon Williams <brandon.williams@akamai.com>
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Date: Tue, 20 Mar 2018 11:01:55 -0400
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Subject: Re: [tram] Allow TURN to forward inbound connectivity checks without permission
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On 03/20/2018 06:07 AM, Simon Perreault wrote:
> Same opinion here. The point of permissions is to prevent TURN clients 
> from being able to run generic servers. It seems like always allowing 
> STUN packets would preserve this feature while solving the session 
> establishment latency problem. And would be quite a bit simpler to 
> implement than ufrag perms. Have your cake, eat it, and eat it a second 
> time.

If you want to prevent someone from running a server on the allocation 
you can't assume that a STUN-looking packet is actually legitimate, so 
some additional validations would be required. Perhaps packet size, 
rate-limiting, and max session counts are enough.

ufrag permissions didn't do enough to be more meaningful there, since it 
would be easy to post the ufrag somewhere public via a mechanism similar 
to dynamic DNS.

--Brandon