Re: [secdir] SecDir review of draft-ietf-mpls-ldp-hello-crypto-auth-05

[Stephen Farrell <[e-mail]>]

Manav,

On 21/05/14 08:39, Bhatia, Manav (Manav) wrote:
> Hi Stephen,
> 
> The crypto mathematics in our draft (and RFC 5310, 5709, 6506, .. and
> quite a few other RFCs/drafts) is slightly different from the basic
> HMAC. In all these RFCs we've introduced an additional pad
> (unimaginatively called the "Apad") that's used in the hash
> computation. We were asked to include the Apad when we were
> originally writing the IS-IS and OSPFv2 security (RFC 5310 and 5709)
> RFCs. Ran Atkinson along with Mathhew Fanto (from NIST) had earlier
> written the RIPv2 RFC which had first employed the Apad. I was
> unequivocally told (by the Security ADs as well) that the Apad had to
> be included since that's what NIST wanted. I am sure Ran Atkinson can
> explain you more clearly about what the actual deal was. However,
> ever since then, we've been including the Apad in all our standards
> (at least the ones coming out of the Routing Area WG).
> 
> This has now been extensively implemented and there are libraries
> available that account for the Apad when computing the hash for the
> routing protocols.
> 
> The Apad is now employed for RIP, OSPF, OSPFv3. I see no reason why
> LDP should be an exception. The same has been proposed for BFD btw.

Even given the above, I fail to see why you repeat this text over
and over and over. Is there a real logic for that?

S

> 
> Cheers, Manav
> 
>> -----Original Message----- From: Stephen Farrell
>> [mailto:[e-mail]] Sent: Wednesday, May 21, 2014
>> 2:53 AM To: Bhatia, Manav (Manav); IETF Security Directorate; The
>> IESG; draft- [e-mail] Cc:
>> Yaron Sheffer; [e-mail] Subject: Re: SecDir review of
>> draft-ietf-mpls-ldp-hello-crypto-auth-05
>> 
>> 
>> 
>> On 19/05/14 21:27, Yaron Sheffer wrote:
>>>>> 
>>>>> * 5.1: Redefining HMAC (RFC 2104) is an extremely bad idea.
>>>>> This reviewer does not have the appropriate background to
>>>>> critique the proposed solution, but there must be an
>>>>> overwhelming reason to
>> reopen
>>>>> cryptographic primitives.
>>>> 
>>>> This is a decision that was taken by Sec Ads when we were doing
>>>> the crypto protection for the IGPs based on some feedback from
>>>> NIST.
>> This
>>>> mathematics is not new and has been done for all IGPs and has
>>>> been approved and rather encouraged by the Security ADs.
>> 
>> The above does not sound like something I recognise. I have
>> repeatedly asked that documents not re-define HMAC. Perhaps this
>> time, I'll make that a DISCUSS and not budge. I probably should
>> have done that before TBH.
>> 
>> If you are revising that doc, *please* get rid of the re-definition
>> and just properly refer to HMAC. Its about time to stop repeating
>> that error.
>> 
>> S.
> 
> 
>