Re: [MLS] Proposal: Proposals (was: Laziness)

Raphael Robert <raphael@wire.com> Fri, 23 August 2019 12:18 UTC

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From: Raphael Robert <raphael@wire.com>
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Date: Fri, 23 Aug 2019 14:17:53 +0200
In-Reply-To: <9d3f0d93-4f69-bb71-9951-f3007820b14d@cs.tcd.ie>
Cc: Richard Barnes <rlb@ipv.sx>, Messaging Layer Security WG <mls@ietf.org>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [MLS] Proposal: Proposals (was: Laziness)
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The ghost user scenario is precisely what we want to avoid. In Richard’s Proposals draft, every Proposal has to be validated by a Commit message, and the latter can only be issued by an existing member of the group. Therefore the server still cannot control the group membership, it can rather only make proposals on how the membership list should be modified. Naturally we need to make sure that everything works as intended.

> On 23 Aug 2019, at 13:26, Stephen Farrell <stephen.farrell@cs.tcd.ie>; wrote:
> 
> 
> Hiya,
> 
> On 23/08/2019 11:24, Raphael Robert wrote:
>> Right now, Add and Remove handshake messages have to be signed by an
>> existing member of the group. There is no way for the server to make
>> any changes to the group membership.
> 
> Thanks. As you note in your other mail, that seems a
> bit concerning, from a potentially ghostly point of
> view. My initial reaction (again with the "benefit"
> of not having kept up to date with the drafts:-) is
> that a service using MLS could put itself in a position
> to do the same thing within the application layer if
> necessary, so it'd seem better for it not to be a
> feature of the MLS protocol.
> 
> I've no opinion on the general idea of proposals, my
> concern is only really about a non-member of the group
> (the server or anyone else) being able to control
> group membership like that, for what I guess would
> effectively be all applications using MLS.
> 
> Cheers,
> S.
> 
>> 
>>> On 23 Aug 2019, at 11:08, Stephen Farrell
>>> <stephen.farrell@cs.tcd.ie>; wrote:
>>> 
>>> Signed PGP part
>>> 
>>> Sorry for not following mls in detail but can you explain how:
>>> 
>>> On 22/08/2019 23:16, Richard Barnes wrote:
>>>> 2. Allow some flavor of server-initiated Add and Remove
>>> 
>>> ...compares to the status quo ante?
>>> 
>>> Thanks, S. <0x5AB2FAF17B172BEA.asc>
>>> 
>>> 
>> 
>> 
> <0x5AB2FAF17B172BEA.asc>