Subject: Re: Questions about OSPF v3 security draft

From: Vishwas Manral <[email-masked]>
Date: Mon, 14 Feb 2005 21:01:28 -0800

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:[email-masked]] On Behalf Of Mike
Fox
Sent: Friday, February 11, 2005 8:04 PM
To: [email-masked]
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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From: Mike Fox <[email-masked]>
Date: Thu, 24 Feb 2005 14:27:47 -0700

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 <[email-masked]>
Sent by: Mailing List <[email-masked]>
02/15/2005 12:01 AM
Please respond to Mailing List
 
        To:     [email-masked]
        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

Regarding 

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