Re: [manet-dlep-rg] DLEP session establishment

[Henning Rogge <[e-mail]>]

I think if someone breaks into the local link between router and
radio/modem, you have more things to worry about than spoofing
attacks.

Henning Rogge

On Tue, Nov 12, 2013 at 5:21 PM, Taylor, Rick <[e-mail]> wrote:
> I seem to remember SCTP (which I hold in high regard) uses a cookie for its 4-way handshake on the grounds that it stops some types of spoofing attacks.
>
> I'll re-read their rationale doc if I can find it.  I was just trying to cover some security considerations here, but it might be misplaced.
>
> I just wonder whether replying to a broadcast with a IP address by blindly connecting to it without some way of checking what your connecting to is what you expect to be there is 'unsafe' - but you do make a good point about the TCP 4-tuple...
>
> Rick Taylor
>
>> -----Original Message-----
>> From: Stan Ratliff (sratliff) [mailto:[e-mail]]
>> Sent: 12 November 2013 16:04
>> To: Taylor, Rick
>> Cc: DLEP Research Group ([e-mail])
>> Subject: Re: [manet-dlep-rg] DLEP session establishment
>>
>> Rick,
>>
>> On Nov 12, 2013, at 10:45 AM, "Taylor, Rick" <[e-mail]>
>> wrote:
>>
>> > Hmmm... good point about complexity in the radio Stan.
>> >
>> > I'd be okay with flipping the whole discovery process so the router
>> advertises and the radio connects.  Making the router maintain the extra
>> timer for strobing is probably more sensible.  Obviously some
>> recommendation for timing of the strobes is needed.
>> >
>> > The handshake still stays 3-way and that covers most of my concerns.
>> >
>> > Any comment on a cookie in the offer?
>>
>> What is the cookie used for? I was thinking the TCP 4-tuple (Source
>> IP/Source Port/Destination IP/Destination Port) is sufficient for any
>> correlation.
>>
>> Regards,
>> Stan
>>
>> >
>> > I have double checked with the 04 draft, and you have covered the
>> broadcast or configured unicast UDP address in the text, so I'm happy.
>> >
>> > Rick Taylor
>> >
>> >> -----Original Message-----
>> >> From: Stan Ratliff (sratliff) [mailto:[e-mail]]
>> >> Sent: 12 November 2013 15:17
>> >> To: Taylor, Rick
>> >> Cc: DLEP Research Group ([e-mail])
>> >> Subject: Re: [manet-dlep-rg] DLEP session establishment
>> >>
>> >> OK, looks like my opinion is "in the rough" on this one...
>> >>
>> >> But I'm still concerned about putting the TCP "server" code into the
>> >> (probably more) constrained modem device. So, what if we make the
>> *router*
>> >> issue the Peer Discovery (call it a Peer Advertisement) to an MCAST
>> >> address/well-known port? That Peer Discovery/Peer Advertisement would
>> >> contain the unicast IP address/port for the TCP listener. The modem
>> would
>> >> respond with the TCP SYN...
>> >>
>> >> The router would continue to periodically "strobe" the Peer
>> Discovery/Peer
>> >> Advertisement ad-nauseum (as much as I hate that approach).
>> >>
>> >> I'm really concerned about modem-side complexity, based on discussions
>> I
>> >> had a couple of years ago with some radio vendors who were looking at
>> >> implementing.
>> >>
>> >> Regards,
>> >> Stan
>> >>
>> >> On Nov 12, 2013, at 7:47 AM, "Taylor, Rick" <[e-mail]>
>> >> wrote:
>> >>
>> >>> Sorry for the delay, I was out of office yesterday.
>> >>>
>> >>> My thoughts:
>> >>>
>> >>>   Router                                        Modem
>> >>>   ===================================================
>> >>>
>> >>> 1)                                  TCP socket listen()
>> >>>
>> >>> 2)  <--------------------------- Peer Discovery Message
>> >>>                             UDP unicast or broadcast?
>> >>>                                      + Session Cookie
>> >>>                                    + TCP address/port
>> >>>          + Alternate reliable protocol endpoint infos
>> >>>
>> >>> 3)  TCP connect()
>> >>>
>> >>> 4)  Initialize (was Peer Offer) ---------------------->
>> >>>   + Session Cookie
>> >>>
>> >>> 5)  <----------------------------------- Initialize ACK
>> >>>                                      + Session Cookie
>> >>>                               + Supported metric TLVs
>> >>>
>> >>>
>> >>> My reasoning, often agreeing with others:
>> >>>
>> >>> The Modem 'advertises' its DLEP support, and therefore should
>> >>> be the one that listens for the TCP connect.
>> >>>
>> >>> A cookie passed between the UDP discovery message and the TCP
>> >>> connection adds a little security (is this the modem I think I am
>> >>> connecting to?)  This could be extended to a full signature TLV
>> >>> in a later RFC.
>> >>>
>> >>> The Peer Discovery message could carry additional reliable
>> >>> protocol endpoint information for non-TCP transports.
>> >>>
>> >>> The Initialize ACK is the correct place to put the 'default'
>> >>> metric TLVs, and is sent by the modem.
>> >>>
>> >>> A 3-way handshake seems safer to me.
>> >>>
>> >>> I have a question over whether the Peer Discovery message should
>> >>> be unicast to a configured destination, or broadcast to all
>> >>> connected peers on a TBD port.  I prefer broadcast as it is more
>> >>> ZeroConf, but I can see use-cases for unicast to a configured
>> >>> destination for more complex topologies.
>> >>>
>> >>> Cheers,
>> >>>
>> >>> Rick Taylor
>> >>>
>> >>>> -----Original Message-----
>> >>>> From: [e-mail] [mailto:manet-dlep-rg-
>> >>>> [e-mail]] On Behalf Of Teco Boot
>> >>>> Sent: 11 November 2013 16:29
>> >>>> To: Stan Ratliff
>> >>>> Cc: DLEP Research Group ([e-mail])
>> >>>> Subject: [manet-dlep-rg] DLEP session establishment
>> >>>>
>> >>>>
>> >>>> Op 11 nov. 2013, om 01:55 heeft Stan Ratliff (sratliff)
>> >>>> <[e-mail]> het volgende geschreven:
>> >>>>
>> >>>>> Also, as to the Discovery: Here's what I'm writing up as we speak:
>> >>>>>
>> >>>>>
>> >>>>> Router
>> >>>> Modem
>> >>>>> ========================================
>> >>>>>                                   <------------------------ Peer
>> >>>> Discovery Message
>> >>>>> Peer Offer with           ------------------------->
>> >>>>> unicast IP addr/
>> >>>>> port for TCP connect
>> >>>>
>> >>>> So this is multicast reply, telling modem to connect?
>> >>>> Why not TCP connect from router to modem? Makes more sense to me, the
>> >>>> modem is the peer offering a service.
>> >>>> Maybe add a TcpPort TLV in the Peer Discovery, this allows other than
>> >> IANA
>> >>>> assigned ports.
>> >>>>
>> >>>>
>> >>>>>
>> >>>>> *Connect on TCP socket. Router has issued TCP "listen",
>> >>>>>  modem issues TCP "connect" (e.g. Modem is the TCP "client",
>> >>>>>  router is the TCP "server")
>> >>>>>
>> >>>>> Now, The modem's UDP socket can be closed.
>> >>>>
>> >>>> Please don't.
>> >>>>
>> >>>>
>> >>>>> Over the TCP
>> >>>>> Socket,
>> >>>>>                                  <------------------------- Peer
>> >>>> Initialization containing
>> >>>>>
>> >>>> TLVs/default values for ALL
>> >>>>>
>> >>>> supported metric values - all
>> >>>>>
>> >>>> meaning the MANDATORY ones,
>> >>>>>
>> >>>> plus any optional metrics (right now,
>> >>>>>
>> >>>> just Resources) that are supported.
>> >>>>
>> >>>> Yes, here the full set TLV exchange takes place. This should not be
>> in
>> >> the
>> >>>> Peer Discovery. That's why I suggested to put this in the Peer Offer.
>> >>>>
>> >>>>
>> >>>>>
>> >>>>> Peer Initialization ACK ---------------------->
>> >>>>> MAY contain optional
>> >>>>> Layer 3 (address) TLVs
>> >>>>
>> >>>> I'm fine with three way handshake, not with this two way. Or use TCP
>> >>>> disconnect when modem modem is not willing to accept first message
>> from
>> >>>> router.
>> >>>>
>> >>>> Teco
>> >>>>
>> >>>>>
>> >>>>> .... And, everything from there is basically the same as before.
>> >>>>
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