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

Simon Perreault <sperreault@jive.com> Sun, 01 April 2018 16:56 UTC

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From: Simon Perreault <sperreault@jive.com>
Date: Sun, 1 Apr 2018 12:56:18 -0400
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To: Justin Uberti <juberti@google.com>
Cc: "Konda, Tirumaleswar Reddy" <TirumaleswarReddy_Konda@mcafee.com>, Brandon Williams <brandon.williams@akamai.com>, Nils Ohlmeier <nohlmeier@mozilla.com>, "Cullen Jennings (fluffy)" <fluffy@cisco.com>, Eric Rescorla <ekr@rtfm.com>, tram@ietf.org
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Subject: Re: [tram] Allow TURN to forward inbound connectivity checks without permission
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2018-03-31 18:50 GMT-04:00 Justin Uberti <juberti@google.com>om>:

> As Brandon says, the ufrag/pwd info could be posted along with the address
> of the server, so while this raises the bar, it doesn't solve the problem.
>
> I agree with Brandon that the only reasonable way to completely contain
> this is some sort of server policy, e.g., some time window or session count
> after which the permission bypass expires, meaning that someone running a
> server would have to be continually requesting new allocations and posting
> their address/credentials.
>

Do we need to completely contain this? Is there actually a problem with the
proposal?

Allowing STUN in allows someone to run a server if and only if the protocol
masquerades as STUN. It doesn't allow a user to run an arbitrary server.
For this to be exploitable, the user would also need to control the clients
in some way.

I can't think of a way this could be exploited practically. Maybe I lack
imagination?

Simon