Re: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt

Alan Johnston <alan.b.johnston@gmail.com> Wed, 08 July 2015 18:42 UTC

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Date: Wed, 08 Jul 2015 13:42:52 -0500
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From: Alan Johnston <alan.b.johnston@gmail.com>
To: Eric Rescorla <ekr@rtfm.com>
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Cc: DISPATCH <dispatch@ietf.org>
Subject: Re: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt
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Hi Ekr,

Thanks for the feedback.  See below.

More feedback on #3 from others would be very helpful.

- Alan -

On Wed, Jul 8, 2015 at 1:00 PM, Eric Rescorla <ekr@rtfm.com> wrote:

> This seems like a good idea.
>
> I have three comments:
>
> 1. You should forbid the answerer from sending back two types of
> keying parameters (e.g., a=crypto and a=fingerprint) because that creates
> confusion.
>

Agreed - I'll put that in.


>
> 2. You probably shouldn't relax the need to send SDES over HTTPS because
> the security properties there are still fairly bad.
>

Right.  I tried to say that in the Security Considerations: "For SDP
Security Descriptions key agreement [RFC4568], an authenticated signaling
channel does not need to be used with OSRTP if it is not available,
although an encrypted signaling channel must still be used."  Did I get it
wrong?


>
> 3. I would suggest that failure to negotiate a secure channel (for
> DTLS-SRTP
> and ZRTP) should lead to media failure not falling back. There's basically
> no good reason for this to fail and it seems like it will make diagnosing
> issues easier.
>
>
I was on the fence about this one.  Agree that it shouldn't happen for
DTLS-SRTP or ZRTP, but I could imagine it happening for certain MIKEY
modes.  Should that really fail the whole session?



> -Ekr
>
>
> On Wed, Jul 8, 2015 at 9:17 AM, Alan Johnston <alan.b.johnston@gmail.com>
> wrote:
>
>> Hi Martin,
>>
>> It is the version of the draft that is actually implemented and used.
>> There are also a few slight differences due to the way that Opportunistic
>> Security is defined.
>>
>> - Alan -
>>
>> On Wed, Jul 8, 2015 at 11:14 AM, Martin Thomson <martin.thomson@gmail.com
>> > wrote:
>>
>>> How does this differ from:
>>> https://tools.ietf.org/html/draft-kaplan-mmusic-best-effort-srtp-01
>>>
>>> On 8 July 2015 at 04:02, Alan Johnston <alan.b.johnston@gmail.com>
>>> wrote:
>>> > All,
>>> >
>>> > Many of us have been talking about "Best Effort SRTP" for many years,
>>> and
>>> > there are a number of deployments.  In addition, the IMTC has
>>> recommended
>>> > it, and the SIP Forum would like to recommend it in SIPconnect 2.0
>>> which for
>>> > the first time includes SRTP media.  With the publication of RFC 7435
>>> > (https://tools.ietf.org/html/rfc7435) the IETF has endorsed this
>>> approach
>>> > as Opportunistic Security (OS), so it would be nice to bring standards
>>> in
>>> > line with industry practice.
>>> >
>>> > Comments on the draft, "An Opportunistic Approach for Secure Real-time
>>> > Transport Protocol (OSRTP)" and the best way forward are most welcome!
>>> >
>>> > - Alan -
>>> >
>>> > ---------- Forwarded message ----------
>>> > From: <internet-drafts@ietf.org>
>>> > Date: Mon, Jul 6, 2015 at 1:48 PM
>>> > Subject: I-D Action: draft-johnston-dispatch-osrtp-00.txt
>>> > To: i-d-announce@ietf.org
>>> >
>>> >
>>> >
>>> > A New Internet-Draft is available from the on-line Internet-Drafts
>>> > directories.
>>> >
>>> >
>>> >         Title           : An Opportunistic Approach for Secure
>>> Real-time
>>> > Transport Protocol (OSRTP)
>>> >         Authors         : Alan Johnston
>>> >                           Bernard Aboba
>>> >                           Andy Hutton
>>> >                           Laura Liess
>>> >                           Thomas Stach
>>> >         Filename        : draft-johnston-dispatch-osrtp-00.txt
>>> >         Pages           : 8
>>> >         Date            : 2015-07-06
>>> >
>>> > Abstract:
>>> >    Opportunistic Secure Real-time Transport Protocol (OSRTP) allows
>>> >    encrypted media to be used in environments where support for
>>> >    encryption is not known in advance, and not required.  OSRTP is an
>>> >    implementation of Opportunistic Security, as defined in RFC 7435.
>>> >    OSRTP does not require advanced SDP extensions or features and is
>>> >    fully backwards compatible with existing secure and insecure
>>> >    implementations.  OSRTP is not specific to any key management
>>> >    technique for SRTP.
>>> >
>>> >
>>> > The IETF datatracker status page for this draft is:
>>> > https://datatracker.ietf.org/doc/draft-johnston-dispatch-osrtp/
>>> >
>>> > There's also a htmlized version available at:
>>> > https://tools.ietf.org/html/draft-johnston-dispatch-osrtp-00
>>> >
>>> >
>>> > Please note that it may take a couple of minutes from the time of
>>> submission
>>> > until the htmlized version and diff are available at tools.ietf.org.
>>> >
>>> > Internet-Drafts are also available by anonymous FTP at:
>>> > ftp://ftp.ietf.org/internet-drafts/
>>> >
>>> > _______________________________________________
>>> > I-D-Announce mailing list
>>> > I-D-Announce@ietf.org
>>> > https://www.ietf.org/mailman/listinfo/i-d-announce
>>> > Internet-Draft directories: http://www.ietf.org/shadow.html
>>> > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>>> >
>>> >
>>> > _______________________________________________
>>> > dispatch mailing list
>>> > dispatch@ietf.org
>>> > https://www.ietf.org/mailman/listinfo/dispatch
>>> >
>>>
>>
>>
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>