Re: [sfc] Alvaro Retana's No Objection on draft-ietf-sfc-nsh-integrity-06: (with COMMENT)

[[e-mail]]

Re-,

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Alvaro Retana [mailto:[e-mail]]
> Envoyé : lundi 12 juillet 2021 21:27
> À : BOUCADAIR Mohamed INNOV/NET <[e-mail]>; The
> IESG <[e-mail]>
> Cc : [e-mail]; [e-mail];
> [e-mail]; [e-mail]
> Objet : RE: Alvaro Retana's No Objection on draft-ietf-sfc-nsh-
> integrity-06: (with COMMENT)
> 
> On July 12, 2021 at 2:52:22 PM, [e-mail] wrote:
> 
> 
> Med:
> 
> Hi!
> 
> ...
> > > (1) Given the required behavior specified in the Security
> > > Considerations section...
> > >
> > > NSH data are exposed to several threats:
> > >
> > > o A man-in-the-middle attacker modifying the NSH data.
> > >
> > > o Attacker spoofing the NSH data.
> > >
> > > o Attacker capturing and replaying the NSH data.
> > >
> > > o Data carried in Context Headers revealing privacy-sensitive
> > > information to attackers.
> > >
> > > o Attacker replacing the packet on which the NSH is imposed with
> a
> > > bogus packet.
> > >
> > > In an SFC-enabled domain where the above attacks are possible,
> (1)
> > > NSH data MUST be integrity-protected and replay-protected, and
> (2)
> > > privacy-sensitive NSH metadata MUST be encrypted for
> confidentiality
> > > preservation purposes. The Base and Service Path headers are not
> > > encrypted.
> > >
> > > Why doesn't this document formally update rfc8300? Concerns that
> > > eventually led to this solution have been expressed for several
> > > other documents, including rfc8459 and rfc8979.
> > >
> > > It looks like the WG didn't consider the question of Updating
> the
> > > base NSH specification. I believe that this document specifies a
> > > required update to NSH, and would like the WG to consider
> formally
> > > Updating rfc8300. [My search of the archive didn't find any
> related
> > > discussion -- did I miss it?]
> >
> > [Med] We don't use the update header as we don't formally update
> any
> > text in 8300.
> 
> Updating text is not the only reason to formally Update another
> specification.
> 
> This document requires the use of both integrity and encryption if
> specific attacks are possible (text above).  It is reasonable to
> interpret that as cases where the "operator deems protection is
> required", which is the text that rfc8300 uses when it talks about
> the need for integrity protection (similar text can also be found
> about encryption).  IOW, the formal Update that I'm suggesting here
> is to provide more insight into when integrity protection and
> encryption are required, and the mechanism to use.
> 
> 
> As I look into this further, I believe there is a normative
> inconsistency between this document and rfc8300:
> 
> - rfc8300 requires the use of an encapsulating transport protocol
> that can provide integrity protection and/or encryption, as needed.
> 
> - This document requires protection as specified in the text
> above.  A stated goal of this specification is so that "the NSH does
> not have to rely upon an underlying transport encapsulation for
> security and confidentiality".
> 
> The outcome is that the requirements in rfc8300 would result in not
> using this specification.
> 

[Med] Not sure about this given that RFC8300 says the following:  

      NSH itself does not mandate protocol-specific integrity
      protection.  However, if an operator deems protection is required,
      several options are viable:

      1.  SFF/SF NSH verification
      ...
      2.  Transport Security
      ...
      3.  NSH Variable Header-Based Integrity

          Lastly, NSH MD Type 2 provides, via variable-length headers,
          the ability to append cryptographic integrity protection to
          the NSH packet.  The implementation of such a scheme is
          outside the scope of this document.

The I-D is basically the third option. 

> 
> > I know that we can interpret the update as "amends", but unless
> I'm
> > mistaken there is no formal IETF consensus on this.
> 
> True.
> 
> Without at least some text explaining the relationship between the
> requirements in this document and how they may be considered instead
> of the ones in rfc8300, I don't think this document is
> complete.  For better or worse, the only tool we have right now to
> make that link clear is the Updates tag.
> 
> 
> Thanks!
> 
> Alvaro.

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