[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: IPsec Issue Discussed for Shim6 at IETF Meeting July 10, 2006


El 19/07/2006, a las 16:50, Bound, Jim escribió:
The MIPv6 case is written down and was discussed at a minimum shime6 needs to add such wording to the spec and have it reviewed by the WG.
The shim6 spec does have some words about this, in particular section 1.6 states: 

   Layering AH and ESP above the multihoming shim means that IPsec can
   be made to be unaware of locator changes the same way that transport
   protocols can be unaware.  Thus the IPsec security associations
   remain stable even though the locators are changing.  This means that
   the IP addresses specified in the selectors should be the ULIDs.
however, it would be possible to add additional detailed description about how would IPSec processing look like in a shimmed environment (whether in the base spec or in the applicability statement)
That would help yes. But, the home agent address is secured with the mobile node too by IPsec.
i was not cosnidering the communication with the HA but directly with the CN using RO mode
Making this word change in the spec and having a discussion would be progress for sure, and we can then at least discuss security ramifications. If you go to my very first mail on this the first input is that the text discussing this part of shim6 is not clear fixing that is a priori for sure then we can go to next steps. But the MIPv6 case is not out of band signaling per se because the home agent address was kept with the node when it roamed and did not have to be securely negotiated after going mobile. That is a different network security scenario and property than CGA in shim6.
indeed the communication between the HA and the mobile node is a different scenario, but the communication between the MN and the CN in RO mode is exactly the same scenario than a shim6 communication AFAICT and it uses the exact same type of out-band signalling, agree? 

regards, marcelo



/jim


-----Original Message-----
From: marcelo bagnulo braun [mailto:marcelo@it.uc3m.es]
Sent: Wednesday, July 19, 2006 4:32 AM
To: Bound, Jim
Cc: Brian E Carpenter; shim6@psg.com; Joe Abley
Subject: Re: IPsec Issue Discussed for Shim6 at IETF Meeting
July 10, 2006

Hi Jim,


El 18/07/2006, a las 18:23, Bound, Jim escribió:


Brian and Joe, (thanks).

If ULID is both ID and Locator that is fine.  Here is more

on my issue

and sorry for late response traveling and email is a pain.

If when the packet is transmitted and the Locator is not

the ULID, AND

the ULID is the SA to decrypt the packet is my concern.

Here is why.

First that means some form of out-of-band signaling was done to
identify a Locator to a ULID so the decrypt can even

happen. This is

out of scope for the IPsec architecture we clearly did not support
out-of-band singaling for IPsec all the way back to the

1994 or 1995

Danvers IETF meeting when we decided to move to IPsec.

Second I am concerned about implementations that now assume

per IPsec

that in fact the Locator is the SA in the arriving or

sending packet

to another node.

Does that help?




but isn't the case that there are existent protocols that
also use an out of band signaling that you mention below the
IPSec layer in a similar fashion that the shim6 protocol (and
i think there are valid reasons why to do that)

Let's consider that case of Mobile IPv6 and in particular the
case of RO mode

Suppose that we have a node M that is communicating with a node C

Suppose that node M has a stable address IPH and that node C
has an address IPC

Suppose that M and C have established and IPSec protected
communication using IPH and IPC (hence the IPSec SA contains
IPH and IPC)

Suppose now that node M (which is a mobile node running
MIPv6) moves and it gets a new address CoA

Suppose that the communication between M and C is in route
optimization mode

Consider the case of packet flowing from M to node C.
In this case, packets flowing from M to the mobile node C
will be carrying CoA in the src address field of the IPv6
header and they will carry the HoA dst option containing the
IPH address In addition, the packets carry the ESP/AH header.
Since the IPSec SA contains IPH (and not CoA) the IPH must be
restored by the MIPv6 layer before the processing.

Actually, RFC3775 states in page 110 that:

       If route optimization is in use, the mobile node inserts a Home
       Address destination option into the packet, replacing
the Source
       Address in the packet's IP header with the care-of address used
       with this correspondent node, as described in Section
11.3.1.  The
       Destination Options header in which the Home Address
destination
       option is inserted MUST appear in the packet after the routing
       header, if present, and before the IPsec (AH [5] or ESP [6])
       header, so that the Home Address destination option is
processed
       by the destination node before the IPsec header is processed.

This basically means, that upon reception, MIPv6 will restore
the original IPH address before the IPSec processing, so that
the original addresses/identifers can be used to search the IPSec SA.

As far as i can see this is exactly the same behaviour that
is being proposed for the shim, or do you see any difference
between the case of the shim6 and mipv6?

Regards, marcelo





Thanks
/jim


-----Original Message-----
From: Brian E Carpenter [mailto:brc@zurich.ibm.com]
Sent: Tuesday, July 18, 2006 11:04 AM
To: Joe Abley
Cc: Bound, Jim; shim6@psg.com
Subject: Re: IPsec Issue Discussed for Shim6 at IETF

Meeting July 10,

2006

Joe Abley wrote:


On 18-Jul-2006, at 07:24, Brian E Carpenter wrote:


Sure, in my shim6 world the ULID is an initially valid locator.
Of course, it may become invalid dynamically during the

course of a

session, but that will not invalidate the SA as far as I can see.



Surely the ULID is static for the lifetime of a session,

regardless

of what happens to the locator set?


Exactly my point; but if the ULID ceases to work as a

locator, it no

longer has its initial duality as both an ID and a locator.
And I want to be sure than Jim doesn't see a problem in that.

     Brian