[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 19:59, Bound, Jim escribió:





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)
The above is really not enough it needs to speak to the actual IPsec processing and discuss the out-of-band signaling required. 



i am not sure i understand...
a description of the IPSec processing is what i mentioned above, so i guess we agree here
in addition, you suggest to include the out of band processing, but if i understand correctly this IS the shim6 protocol, since this is the way the alternative locators and associated security information is conveyed... we could put it explicitely... 




  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


Same thing from the HA side as it is proxy to the MN.



No, the HA is not involved in the data path when RO mode is used,
in RO mode the data packet flow directly between the MN and the CN, so the two cases RO and BT mode are different. The point is that RO mode requires similar out of band signaling and result in a IPSEc processing equal to the one of the shim6 protocol 




 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?
It is not exactly the same all cohesive security containment is rigorous on the MN as it owns its HA address.
the point is how oes it proves to the CN that it owns the HoA... using IPSec? no, because, similarly to the shim6 case, in order to use IPSec for this you would need global PKI. So alternative methods (the so called out of band signalling) are needed. The result in terms of IPSec processing is the same than in shim. Both MIP and shim lie below the IPSec layer and the translate the locator of received packet to the original identifiers/home address, so that the IPSec SA can be searched using the identifiers and not the locators used to route the packets.
Much different than what we are saying here. Also the CN still can perform IPsec processing at the IP layer without popping up to code for a shim layer.
I don't see why do you day this... MIP needs to restore the HoA before the IPSec processing exactly the same that in the shim case, where the shim needs to restore the ulids before IPSec processing. In both cases the security of the binding between the identifier and the locators is not based in IPSec but is this out of band security. 

Regards, marcelo



thanks
/jim


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