Re: More comments and questions on OSPFv3 security draft

[Vishwas Manral <[e-mail]>]

Hi Mike,

 

The quote I refer to is from 2401bis(which is with the IESG), which
replaces 2401.

     "- Remote IP Address(es) (IPv4 or IPv6): this is a list of ranges
       of IP addresses (unicast, anycast, broadcast (IPv4 only), or
       multicast group). "



I would be ok if any clarification is added though.

 

Thanks,

Vishwas

 

________________________________

From: Mailing List [mailto:[e-mail]] On Behalf Of Mike
Fox
Sent: Wednesday, May 18, 2005 1:22 AM
To: [e-mail]
Subject: More comments and questions on OSPFv3 security draft

 


Back in Feburary and March I had a dialog with Vishwas involving some
questions on the OSPFv3 security draft.  Our security expert has asked
for some additional clarification, here is his comment:   

My comment is based on the following from RFC 2401 (section 4.1): 

A security association is uniquely identified by a triple consisting
  of a Security Parameter Index (SPI), an IP Destination Address, and a
  security protocol (AH or ESP) identifier.  In principle, the
  Destination Address may be a unicast address, an IP broadcast
  address, or a multicast group address.  However, IPsec SA management
  mechanisms currently are defined only for unicast SAs.  Hence, in the
  discussions that follow, SAs will be described in the context of
  point-to-point communication, even though the concept is applicable
  in the point-to-multipoint case as well. 

As noted above, two types of SAs are defined: transport mode and
  tunnel mode.  A transport mode SA is a security association between
  two hosts.

Comment: Certainly an SPD can have a ranged address that points to the
same SA. This is how you would set up an SPD in a firewall for tunnel
mode traffic. That is, a range of addresses for a network (not on the
firewall) can use a single SA. The destination IP address is an IPSec SA
endpoint. However, the SA must adhere to the definition above. For
unicast transport mode, I read this to be that the destination address
is a single IP address not a range. I suggest that the OSPFv3 security
draft specify exactly how the manual SAs would need to be set up to be
compliant. I don't think there is anything in RFC 2401 that allows a
range of unicast IP addresses to be "a unicast address". 

And since it has been a while, here is the string of notes he is
commenting on: 





 

Vishwas Manral <[e-mail]> 
Sent by: Mailing List <[e-mail]> 

03/01/2005 05:59 AM 
Please respond to Mailing List 

        
        To:        [e-mail] 
        cc:         
        Subject:        Re: Questions about OSPF v3 security draft




Hi Mike,

Sorry for the delay. I may be wrong as I have not implemented this
myself, however my views are as follows: -

If you see the SPD entry the Remote IP Address can be 
     "- Remote IP Address(es) (IPv4 or IPv6): this is a list of ranges
       of IP addresses (unicast, anycast, broadcast (IPv4 only), or
               multicast group). "
So for OSPF the Multicast as well as the unicast addresses will be used
to refer to an SA.

Next Layer Protocol would say OSPF.

That way we will have just one entry for all OSPF packets out of an
interface, just as we want it and a similar entry for inbound traffic. I
do not see a case of Full Mesh at all. I may be missing the point.

Thanks,
Vishwas
________________________________________
From: Mailing List [mailto:[e-mail]] On Behalf Of Mike
Fox
Sent: Friday, February 25, 2005 2:58 AM
To: [e-mail]
Subject: Re: Questions about OSPF v3 security draft


Vishwas, 

I shared your response with our security expert and here is his
response: 

What we need to know is whether the paragraph is referring to unicast. "
What it means is we will use the same crypto-algorithm and keys for all
traffic to a neighbor over an interface." If this comment is referring
to unicast, the point remains is that there will be multiple SAs. We
will not be able to adhere to the figure 3 requirements for unicast, and
there will be full meshing of SAs required between all communicating
OSPFs. Not so bad if using IKE. Really bad if using manual SAs.   

Here is the thread of notes being referred to (since it's been a couple
of weeks): 

Vishwas Manral <[e-mail]> 
Sent by: Mailing List <[e-mail]> 
02/15/2005 12:01 AM 
Please respond to Mailing List 
        
        To:        [e-mail] 
        cc:         
        Subject:        Re: Questions about OSPF v3 security draft



Hi Mike, 
  
I think both the authors are on leave, so they will probably reply
later. 
  
However regarding the first point, I agree the wording should be
clearer. However what it means is we will use the same crypto-algorithm
and keys for all traffic to a neighbor over an interface. 
  
Regarding the second point, I think I too have brought the issue on this
list and the reply I think was that the draft does not prohibit the use
of IKE for unicast flows. 
 

Thanks, 
Vishwas 
________________________________________

From: Mailing List [mailto:[e-mail]] On Behalf Of Mike
Fox
Sent: Friday, February 11, 2005 8:04 PM
To: [e-mail]
Subject: Questions about OSPF v3 security draft 
  

Regarding
http://www.ietf.org/internet-drafts/draft-ietf-ospf-ospfv3-auth-07.txt,
and the previous drafts, a couple of questions have come up in our shop.


1) Section 7, 2nd paragraph says "the implementations MUST use manually
configured keys with same SA for inbound and outbound traffic (as shown
in figure 3).  I assume the "same SA" MUST rule applies to multicast
traffic only and not unicast traffic. This is because an SA is defined
as an SPI, security protocol (AH or ESP), and destination IP address.
For unicast addresses, by definition there will be as many SAs as there
are unicast destination addresses. Therefore, I don't think it is
possible to apply this MUST rule given the current IPSec definition (RFC
2401 section 4.1) of an SA for unicast. Assuming the intention of the
draft was to apply only to multicast and given the number of potential
SAs carrying unicast traffic, it would seem that using IKE to setup the
SAs dynamically would be a reasonable alternative to manual keying.     
 
2)Section 9, 2nd paragraph discusses setting up a "secure IPSec channel
dynamically once it acquires the required information".  Since this
traffic is unicast only, IKE could easily set up the required SAs
without knowing the specific IP addresses in advance. Creating SAs
dynamically do not fit easily within scope of manual SA functional
capabilities. Why not use IKE for this traffic? Is this an acceptable
option?   

Mike 


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