Subject: [AAA-WG]: Regarding security proposals from the interim meeting

From: Kaushik Narayan <[email-masked]>
Date: Fri, 9 Feb 2001 10:16:35 -0800 (PST)

hi!

   Well at the interim meeting it was felt that the following security
   mechanisms be supported

   NAS - IPSEC,SSL,Object Level (pki,kerb)
   Proxy - IPSEC,SSL 
   Homeserver - IPSEC,SSL, Object Level(pki,kerb)

   Conclusion -

   Use IPSEC/SSL for hop by hop
   Do away with ICV and E-P and shared secret mechanism
   Use object mechanism for end to end

   Here is what I feel

   Since object level mechanisms provide end to end security the
   object level infrastructure (CA,kdc) can be use to provide 
   hop by hop security as well, moreover the shared secret mechanism
   can stay as well.
   
   The ICV and E-P can stay and provide hop by hop security, they can 
   be generated using the shared secret or by using keys negotiated 
   using the object level security mechanism (pki,kerb). Shared secrets
   could be used for intra-domain hops and object level security 
   mechanisms could be used for inter-domain hops.

   Well i foresee two scenarios

  1> Scenario I

  Single domain enterprise - The user logs in via the enterprise NAS
  and is authenticated by a diameter server in the same domain. In such 
  a scenario shared secret security between the NAS and the diameter 
  server would suffice.

  2> Scenario II

  Multi-domain shared/roaming services - The user logs into a romaing/shared
  use NAS and the request is forwarded to the diameter homeserver via the
  roaming/shared proxy/proxies. 

  In such cases there is need for e2e security between NAS-to-homeserver and
  hop-by-hop security between NAS-to-proxy and proxy-to-homeserver. There
  is a difference between these two hops.(this is a simplistic case with
  a single proxy in between a NAS and homeserver) 

  NAS-to-proxy hop is an intra-domain hop and shared secret security might
  suffice but the proxy-to-homeserver is an inter-domain hop and there MUST
  be a strong security mechanism (either transport or object level). Morever
  NAS-to-proxy is typically a (1:1 or 1:number of backup proxies) so managing
  shared secrets is not a problem. 
  
  Now the question boils down whether e2e security is mandatory. If e2e 
  is mandatory for multi-domain scenarios then there would an object 
  level mechanism and the necessary infrastructure would be present. This
  infrastructure can be used to provide object level security for hop-by-hop
  as well.

  In case e2e is optional and in a certain ISP decides not to use e2e security
  then we would need transport layer security to secure the proxy-to-homeserver
  hop since the customer won't need to have the object level mechanism  
  infrastructure (KDC or PKI).

  Scenario I

  -----------                   -----------
 |           |                 |           |
 |           |                 |           |
 |    NAS    |                 |   server  |
 |           |                 |           |
 |           |                 |           |
  -----------                   -----------
             <----------------> 
                shared secret

  Scenario II (e2e used)

  -----------                   -----------               ---------
 |           |                 |           |             |          |
 |           |                 |           |             |          |
 |    NAS    |                 |   proxy   |             |homeserver|
 |           |                 |           |             |          |
 |           |                 |           |             |          |
  -----------                   -----------               ----------
             <---------------->             <------------> 
                shared secret                 Object Level (Kerb,pki)
             
             <------------------------------------------->
                         Object Level (Kerb,pki)

  Scenario II (e2e not used)

  -----------                   -----------               ---------
 |           |                 |           |             |          |
 |           |                 |           |             |          |
 |    NAS    |                 |   proxy   |             |homeserver|
 |           |                 |           |             |          |
 |           |                 |           |             |          |
  -----------                   -----------               ----------
             <---------------->             <------------> 

              shared secret                    IPSEC/SSL

   In this case it would too much of an overhead to ask someone 
   to have kerb,pki infrastucture for only hop by hop since hop 
   by hop strong security can be achieved by IPSec,SSL.

   One note - In all three diagrams above the shared secret mechanism 
   is being used for NAS-to-proxy hop by hop security. This is need not 
   mandatory and strong security might be used for this hop as well.

   The only other scenario is the redirection wherin the NAS->to-homeserver
   is hop-by-hop wherein it again you would need to transport layer security.

   So I guess the answer to my original question of whether object level
   security can be used for hop by hop as well lies in two questions

   i> Is e2e mandatory ? 

   ii> There was some talk in the interim meeting about discouraging 
       redirection. Is redirection very important?

   There is another question that is raised

    Should we do away with shared secret for hop by hop especially 
    since shared secrets might suffice for NAS-to-proxy hop and it
    won't effect NAS performance.

 kaushik!