Re: [6tsch] Feedback on draft-ohba-6tsch-security-00

Rafa Marin Lopez <rafa@um.es> Fri, 05 July 2013 17:39 UTC

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From: Rafa Marin Lopez <rafa@um.es>
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Date: Fri, 5 Jul 2013 19:39:19 +0200
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To: Rene Struik <rstruik.ext@gmail.com>
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Cc: 6TSCH <6tsch@ietf.org>, Yoshihiro Ohba <yoshihiro.ohba@toshiba.co.jp>, Rafa Marin Lopez <rafa@um.es>
Subject: Re: [6tsch] Feedback on draft-ohba-6tsch-security-00
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Hi Rene:

El 05/07/2013, a las 18:51, Rene Struik escribió:

> Hi Rafa:
> 
> Thanks for your note. Some brief feedback below.

Mine are also below

> 
> Buen fin de semana.

Gracias!

> 
> Rene
> 
> On 7/5/2013 12:15 PM, Rafa Marin Lopez wrote:
>> Hi Rene:
>> 
>> Thanks for your review. Let me provide some comments about your review in Section 5.
>> 
>> a) Regarding PANA, it is worth noting that the usage PANA here is for phase 2 KMP, which is different from phase 1.
> 
> RS>>
> True, Section 5.2 refers to use of PANA with Phase-II key establishment; however, Section 5.1 refers to use with Phase-I as well. The more important question to explain would be how it can act in stateless manner.

Not sure how "stateless" applies in phase 2. I mean in this case there is no relay in the middle. Just PaC and PAA and a direct link between two nodes. I guess your comment is more related with R1-2 in Section 4, right?.

> <<RS
>> Here a node tries to establish a one hop link connection with another node. Then one acts as the PaC and the other PAA. That is why the text says:
>> 
>> "It is worth noting that, though
>>           this candidate solution leverages the PaC implementation from
>>           Phase-1, each node needs to deploy a PAA implementation, an EAP
>>           server and a specific EAP method, which may be different from the one
>>           used for Phase-1."
>> 
>> 
>>         
>> So here, you run PANA
>>           between both nodes and establish a key that you pass to IEEE
>>           802.15.4e to protect the link. I assume you want more details
>>           about this particular point, don't you?
>>  
>> b) Regarding HIP-DEX, the text says that HIP-DEX would require to carry certificates and for that you need CERT parameter. So, in
>>           the end, my understanding is that HIP-DEX is not deficient to
>>           carry certificates since you would have the CERT parameter for
>>           that.
>> 
>> 
>>         
> RS>> 
> My understanding of the text was that HIP DEX does not include CERTs, but admittedly I did not check the internet draft. (As an aside, I thought HIP IETF group was winding down and the draft has been expired for a while). 

The text is right and so is your interpretation: CERT parameter is not defined in HIP DEX but in RFC 5201 and draft-ietf-hip-rfc5201-bis-12. However, I do not see any reason why HIP-DEX could not carry this parameter.

> 
> The text says this:
> However, by just using
> the value of the public key and the private key is not enough to
> carry out the authentication between nodes. In particular, a node
> A and node B should not be able to successfully finish HIP DEX
> execution if they both have not been authenticated in Phase-1.
> Thus, HIP DEX will require the inclusion of the certificate of
> each node to achieve full mutual authentication. The information
> in the certificate must ensure that the node was authenticated in
> Phase-1. In consequence, HIP DEX must include a CERT parameter
> for carrying this certificate.
> <<RS
> 
> RS>>
> On a general note, when reviewing the text, I mostly look at security properties and try and see how protocols would fit the bill. To me, it was not clear what makes using HIP-{DEX, BEX, other acronym} desirable to use (and I am not aware of too many people who seriously looked into this). I think it would be useful to articulate why one *should* use a particular protocol, rather than simply listing protocols one apparently *could* use, and to articulate metrics (security properties, protocol flows, communication/computational latency, etc.).

Regarding HIP-DEX, and just as an example, you would expect something like http://www.cs.helsinki.fi/u/gurtov/papers/hip_dex.pdf

In any case, I understand your point. I guess, in general, you would like to see this type of analysis for each of the alternatives, no?. 

Best regards.


> <<RS
> 
> 
>> Best Regards.
>> 
>> 
>> El 05/07/2013, a las 16:56, Rene Struik escribió:
>> 
>>> Hi Yoshi:
>>> 
>>> I had a look at your draft and reflected somewhat on the requirements mentioned.
>>>  
>>> Initial feedback:
>>> 
>>> General remark:
>>> 1) The draft text seems almost independent of 802.15.4e behavior. While the security considerations make reference to the need to authenticate time synch and channel hopping info in beacon frames and refer to potential nonce "overflow" issues, it is not that easy to see how the mechanisms described in the draft address these 802.15.4e-specific considerations. 
>>> 2) The draft seems to aim at providing both (a) key establishment functionality (setting up a secure peer-to-peer channel); (c) key distribution (handing out link keys, muulticast keys, network keys). It would be useful to organize the draft so as to separate these functionalities more clearly (e.g., Phase-II KMP vs. Phase-II Key Distribution). What about key updates?
>>> 
>>> Security Framework (Section 3):
>>> a) The security framework (Phase-III) seems to require incremental roll-out/planning of the network, witness Fig. 2. If so, it would be good to indicate how devices transgress through the different "phases" defined and to what degree this requires planning/intervention by an operator.
>>> b) The bootstrapping phase (Phase-I) suggests inline interaction of a device with an authentication server (which is assumed to mostly be the coordinator of the mesh network). Since bootstrapping only results in issuance of credentials to be used by devices for Link Establishment (Phase-II), I can imagine this step to be often organized differently than described, e.g., by embedding a device certificate with a device at device manufacturing. In that case, no inline interaction with an authentication server seems required, at least not for *authentication* purposes.
>>>  
>>> KMP Requirements (Section 4):
>>> R1-1: The requirement for mutual authentication seems to rule out "resurrecting duckling" policy models. Is this correct? Moreover, this rules out one/two pass protocols.
>>> R1-2: The requirement for stateless relay may not work within the 802.15.4e context: if a device A talks with an authentication server T via its neighbor R, where R and T operate in a secured network (i.e., one where all communications are cryptographically secured), R needs to "remember" that it should initially communicate back to A without security (since A and R do not have a shared key yet). Thus, R needs to maintain state that communications to A have to be treated differently (in 802.15.4e speak: A has "exempt status"). Or, is the idea that R somehow encodes this exempt status into its relay messages, so that it can pass this "hot potato" along and receive this back via T?
>>> R2-2: I can imagine other scenarios than pre-provisioning of credentials or passing these along via Phase-I KMP: wouldn't piggy-backing this info along communication flows of Phase-II KMP also be an option?
>>> 
>>> Candidate KMPs (Section 5):
>>> a) PANA. With bootstrapping during manufacturing, Phase-I may be organized differently. It would be good to show how PANA can fit 802.15.4e needs in a stateless fashion.
>>> b) HIP-DEX. The draft suggests this protocol (an expired draft), but at the same time points out that it is deficient, since does not support carrying certificates. This is somewhat puzzling.
>>> 
>>> 
>>> 
>>> 
>>> On 7/5/2013 1:20 AM, Thomas Watteyne wrote:
>>>> All,
>>>> 
>>>> Below is the proposed agenda for the 6TSCH call tomorrow:
>>>> 
>>>> Approval minutes last call [1min]
>>>> draft-ohba-6tsch-security-00 [10min]
>>>> Simulator [10min]
>>>> Description of PCE [10min]
>>>> Preparing for the BOF [25min]
>>>> Re-organization Bitbucket [2min]
>>>> AOB [1min]
>>>> 
>>>> As usual, feel free to propose any changes to the agenda, also at the beginning of the call.
>>>> Remember that this call will be recorded.
>>>> 
>>>> Pascal & Thomas
>>>> 
>>>> 
>>>> 
>>>> Topic: 6TSCH Weekly
>>>> Time: 8:00 am, Pacific Daylight Time (San Francisco, GMT-07:00) 
>>>> Meeting Number: 206 802 913 
>>>> Meeting Password: sixtus 
>>>> 
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>>>> ------------------------------------------------------- 
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>>> 
>>> 
>>> -- 
>>> email: rstruik.ext@gmail.com | Skype: rstruik
>>> cell: +1 (647) 867-5658 | US: +1 (415) 690-7363
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>> 
>> -------------------------------------------------------
>> Rafael Marin Lopez, PhD
>> Dept. Information and Communications Engineering (DIIC)
>> Faculty of Computer Science-University of Murcia
>> 30100 Murcia - Spain
>> Telf: +34868888501 Fax: +34868884151 e-mail: rafa@um.es
>> -------------------------------------------------------
>> 
>> 
>> 
>> 
> 
> 
> -- 
> email: rstruik.ext@gmail.com | Skype: rstruik
> cell: +1 (647) 867-5658 | US: +1 (415) 690-7363
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-------------------------------------------------------
Rafael Marin Lopez, PhD
Dept. Information and Communications Engineering (DIIC)
Faculty of Computer Science-University of Murcia
30100 Murcia - Spain
Telf: +34868888501 Fax: +34868884151 e-mail: rafa@um.es
-------------------------------------------------------