Re: [IPsec] New revision of TCP Encapsulation draft

Tue, 08 Dec 2015 13:09:04 -0800 

Hi Tommy,
Thanks for clarifying this point. But I still think we are making a protocol change for what can be solved easily at the implementation level. Implementations will need to tag each IKE SA with the currently valid TCP connection on which responses can be sent. And ESP SAs likely already point to their parent IKE SA. So when we have an ESP packet that needs to be sent back from the responder, why not look up its associated IKE SA and use it to find the TCP connection? 


IMHO it would be better if we can stick to the simple model of a TCP 
wrapper for an unordered pile of IKE and ESP messages. This would add 
TCP with the minimal change to ESP, IKE and the relationship between them.


Thanks,
    Yaron

On 12/08/2015 10:24 PM, Tommy Pauly wrote:

Hi Yaron,


The original version of the draft did not require that the new TCP 
connection begin with an IKE message, but it was added in response to 
feedback we received at our meeting in Yokohama.



The concern was that the new TCP connection would almost certainly 
have different ports from the old connection. In order for the server 
to send packets back to the client, it needs to know the correct 
mapping for both the IKE SAs and the Child SAs. If we allow an ESP 
packet to be the first packet of a new connection, it may be hard to 
implement a correct server that reacts to that and adjusts all 
associated IKE and Child SA values to use the new port. However, it 
the first packet is an IKE packet, the server can essentially treat it 
as if it were MOBIKE and reset the ports.



In the case of multiple IKE SAs over a TCP connection (which is a new 
edge case that has been brought up), perhaps it would make sense to 
say that for all IKE SAs using the connection, at least one IKE 
message must precede any ESP messages for a Child SA of the IKE SA.


Does this make sense?

Thanks,
Tommy


On Dec 8, 2015, at 2:12 AM, Yaron Sheffer <[email protected] 
<mailto:[email protected]>> wrote:


Hi Samy,


Thanks for the new draft. It addresses most of my comments, but one 
question remains.



I still don't understand why we require that each connection should 
start with an IKE message. The explanation given is "to allow the 
peer to know with which IKE session the traffic is associated." But 
of course the ESP SPI identifies the Child SA, and implicitly, the 
IKE SA.



Moreover, later in the same section you allow multiple IKE SAs over 
the same connection, which again doesn't work well with the reasoning 
above.


Best,
    Yaron

On 12/08/2015 08:40 AM, Samy Touati wrote:

Hi Yaron and Yoav,

An updated draft addressing your comments has been posted.

https://www.ietf.org/internet-drafts/draft-pauly-ipsecme-tcp-encaps-02.txt

Please check it out, and provide feedback.


Thanks.
Samy.


*From:* Yaron Sheffer <[email protected]>
*Sent:* Nov 20, 2015 3:11 PM
*To:* Tommy Pauly; IPsecME WG
*Subject:* Re: [IPsec] New revision of TCP Encapsulation draft

Hi Tommy,

I also think this is very relevant work. Here are some comments to -01:


I think that Yoav's draft, draft-nir-ipsecme-ike-tcp-01, should be 
cited

under "prior work", both because it is documented and also because I
believe it is implemented by a vendor.

In Sec. 1, under the UDP encapsulation, I suggest to add "Often peers
will use UDP encapsulation even when there is no NAT on the path, for
example because networks or middleboxes do not support IP protocols
other than TCP and UDP."

"Although a stream" - this paragraph is not worded very well (streams
don't send anything) and is hard to understand. There are lots of

networks that use jumbo frames and so hardcoding the value 1500 into 
the

spec may not be a good idea.


I can think of HA cases where several gateways are handling ESP SAs 
that

are all associated with the same IKE SA. So I'm wondering why we are

insisting on all Child SAs being in the same connection, and as a 
result

requiring that an IKE message be the preamble to any new connection.

Although it might seem obvious, I think Sec. 3 should say explicitly

that if the connection is closed midway through a message, the 
recipient

must silently drop the partial message.

You may want to add to the last paragraph of the Security
Considerations: This document explicitly does not define a profile for
TLS when used in this manner, or any relation between identities at the
IPsec level and those at the TLS level ("channel binding").

Thanks,
        Yaron

On 11/20/2015 11:49 PM, Tommy Pauly wrote:
> Hello,
>

> Based on the feedback received at our informal meeting in 
Yokohama, I’ve updated the draft for TCP Encapsulation of IKEv2 and ESP:

>
> https://tools.ietf.org/html/draft-pauly-ipsecme-tcp-encaps-01
>
> The revisions include:

> - More explanation in the introduction about the motivation, and 
other work that this draft is trying to standardize (3GPP 
recommendations, proprietary IKEv1 IPSec over TCP versions, and SSL 
VPNs).
> - Comments about maximum IKE and ESP message size within the TCP 
stream, which is effective the MTU of the tunnel.
> - Specify that if the TCP connection is brought down and 
re-established, the first message on the stream must be an IKE message.
> - Detailed considerations about interactions with middleboxes 
(thanks Graham Bartlett for input on this).

>

> In the meeting in Yokohama, there was general agreement that this 
was relevant work that we’d like to keep looking into. Please read 
the document, and provide any feedback you have!

>
> Thanks,
> Tommy
> _______________________________________________
> IPsec mailing list
> [email protected] <mailto:[email protected]>
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>

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