Re: [secdir] secdir review of draft-ietf-lisp-lcaf-15

Dino Farinacci <farinacci@gmail.com> Mon, 26 September 2016 16:42 UTC

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From: Dino Farinacci <farinacci@gmail.com>
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Date: Mon, 26 Sep 2016 09:43:00 -0700
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Cc: The IESG <iesg@ietf.org>, draft-ietf-lisp-lcaf.all@ietf.org, secdir@ietf.org
Subject: Re: [secdir] secdir review of draft-ietf-lisp-lcaf-15
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> On 09/25/2016 06:15 PM, Dino Farinacci wrote:
>>> I found one issue in various parts of the document (described below),
>>> but I'm not sure it's relevant to security. If it is, then I think this
>>> document is Almost Ready. If not, then I think this document is Ready
>>> With Nits.
>>> 
>>> There are multiple places in the document where it's possible to encode
>>> semantically equivalent information in multiple ways, despite the word
>>> "canonical" being in the title of the document. Is there anything that
>>> relies on these addresses being canonical for security purposes?
>> 
>> No not for security purposes. There are multiple ways because we allow some nesting of information as well as allow for compatibility for older implementations that can’t parse some AFIs and LCAFs but is required to parse the AFI-List LCAF type.
> 
> Ok, then I think it needs to be made clear in the security
> considerations that this format cannot be relied on to have no more than
> one representation for the same information.

Sorry, I am not following your point. The nesting procuedure of LCAFs allow the same type of address to be expressed multiple ways. I can’t tell from your commentary if this is a good thing for security or a bad thing. So please provide some suggested text on what you would like to see in the Security Considerations section.

> IESG: This means that I think this document is Ready With Nits.
> 
> 
>>> Multiple places in the document (sections 4.1, 4.5, and 4.8) specify
>>> mask lengths, but do not specify that the masked out bits MUST be set to
>>> zero.
>> 
>> Hmm, by definition, a mask-length of say 24 if a mask of 0xffffff00. And in 4.1:
>> 
>>  IID mask-len:  if the AFI is set to 0, then this format is not
>>      encoding an extended EID-prefix but rather an instance-ID range
>>      where the 'IID mask-len' indicates the number of high-order bits
>>      used in the Instance ID field for the range.
>> 
>> It is clear that the high-order bits are used that cover the mask-length and the low-order bits are ignored. Is this not clear to you?
> 
> That part is clear to me. I just meant that the document as written
> appears to allow 1.2.3.4/24 to be equivalent to 1.2.3.7/24. If the

I will make this more clear. I added some text.

>> Section 6 (Security Considerations): There is no discussion of these
>>> addresses being canonical, and what other systems might or might not
>>> rely on these addresses being canonical.
>> 
>> In this respect “canonical” is relative to how LISP defines to encode both simple AFI encoded addresses or more complex/flexible addresses that accompany information.
> 
> Ok. I interpreted canonical to be a security property of the addresses,
> i.e., that if two addresses are not bytewise equal, then they must not
> have the same meaning. If that's not what you meant by canonical, then I
> think the security considerations should say that, so that nobody tries
> to rely on that property in the future.

Canonical in this spec means semantically canonical. That is the following two IP addresses are equal:

AFI=1, 1.1.1.1
AFI=LCAF, lcaf-type=AFI-list, AFI=1, 1.1.1.1

>> Section 4.7: The Key Algorithm description doesn't point to a registry
>>> of valid values or otherwise say how to interpret values in that field.
>> 
>> We have put that in a use-case document. This Security Key LCAF is used by 2 use-cases. It is used for LISP-DDT and for lisp-crypto. In the lisp-crypto document we have a registry for cipher suites used.
> 
> Should this document reference one or both of those documents?

I added text to reference the two documents that use this Security Key LCAF Type.

I’ll post a new draft when you get me some text for the Security Considerations section. Thanks!

Dino

> 
> 
> -- 
> David Eric Mandelberg / dseomn
> http://david.mandelberg.org/
>