Re: [rtcweb] consent freshness [was RE: STUN for keep-alive]

"Muthu Arul Mozhi Perumal (mperumal)" <mperumal@cisco.com> Thu, 22 September 2011 13:58 UTC

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Thread-Topic: [rtcweb] consent freshness [was RE: STUN for keep-alive]
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From: "Muthu Arul Mozhi Perumal (mperumal)" <mperumal@cisco.com>
To: "Magnus Westerlund" <magnus.westerlund@ericsson.com>
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Subject: Re: [rtcweb] consent freshness [was RE: STUN for keep-alive]
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|Secondly, I think in those cases a timer on the inactivity
|from both parties should be considered to terminate the session.

If the timer is based on RTP inactivity it would terminate the session. If it is based on RTCP inactivity (which many implementations do) it wouldn't.

Muthu

|-----Original Message-----
|From: Magnus Westerlund [mailto:magnus.westerlund@ericsson.com]
|Sent: Thursday, September 22, 2011 6:07 PM
|To: Muthu Arul Mozhi Perumal (mperumal)
|Cc: Dan Wing (dwing); rtcweb@ietf.org
|Subject: Re: [rtcweb] consent freshness [was RE: STUN for keep-alive]
|
|On 2011-09-22 14:19, Muthu Arul Mozhi Perumal (mperumal) wrote:
|> |That is a possibility, but I think one can start by ensuring |that
|> one actually check for ones own traffic being reported |back. That
|> gives you some entropy. Which is a slightly longer |context gives you
|> good verification that you are not contining |sending into a location
|> where there receiver you intended to |have sent to moves away.
|>
|> Agree it would suffice in general. However, for cases like double
|> hold (SDP offer with a=inactive) where you would be neither sending
|> nor receiving media the attacker can keep replaying the RTCP packets
|> with an empty report block (that no zero entropy) making you think
|> the other end is still alive.
|>
|> Of course, you may ultimately disconnect the call but it could mean a
|> DOS attack..
|
|If neither party is actually transmitting media then the only traffic is
|RTCP in either directions. Thus one RTCP compound packet per SSRC per
|regular reporting interval. Unless you have an app that open a lot of
|media streams that is usually pretty low bit-rate. And if you actually
|have a lot of streams, then the bit-rate will saturate at the configured
|RTCP rate. But I would note this is in fact a potential attack vector if
|one can set the RTCP bit-rate arbitrary high.
|
|Secondly, I think in those cases a timer on the inactivity from both
|parties should be considered to terminate the session.
|
|Cheers
|
|Magnus Westerlund
|
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