Re: [Detnet] Benjamin Kaduk's Discuss on draft-ietf-detnet-architecture-11: (with DISCUSS and COMMENT)

[János Farkas <[e-mail]>]

Hi Benjamin,

Thank you for your review!

Focusing on the main point now: Section 5 Security Considerations. We 
could consolidate the section to address your comment. Would it be 
helpful to replace the section with the following text?:


Security considerations for DetNet are described in detail in 
[I-D.ietf-detnet-security]. This section considers exclusively security 
considerations which are specific to the DetNet Architecture.

Security aspects which are unique to DetNet are those whose aim is to 
secure the specific quality of service aspects of DetNet, which are 
primarily to deliver data flows with extremely low packet loss rates and 
bounded end-to-end delivery latency. A DetNet is implemented using MPLS 
and IP (including both v4 and v6) technologies, and thus inherits the 
security properties of those technologies at both the control plane and 
the data plane.

Security considerations for DetNet are constrained (compared to, for 
example, the open Internet) because DetNet is defined to operate only 
within a single administrative domain (see Section 1).  The primary 
considerations are to secure the request and control of DetNet 
resources, maintain confidentiality of data traversing the DetNet, and 
provide uninterrupted availability of the DetNet quality of service.

To secure the request and control of DetNet resources, authentication 
and authorization must be provided for each device connected to a DetNet 
domain, most importantly to network controller devices. Control of a 
DetNet network may be centralized or distributed (within a single 
administrative domain). In the case of centralized control, precedent 
for security considerations as defined for ACTN can be found in RFC8453, 
Section 9. In the case of a distributed control protocols, DetNet 
security is expected to be provided by the security properties of the 
protocols in use. In any case, the result must be that manipulation of 
administratively configurable parameters is limited to authorized entities.

To maintain confidentiality of data traversing the DetNet, application 
flows must be protected through whatever means is provided by the 
underlying technology. For example, encryption may be used, such as that 
provided by IPSec for IP (Layer 3) flows and by MACSec for Ethernet 
(Layer 2) flows. DetNet flows are identified on a per-flow basis, which 
may provide attackers with additional information about the data flows 
(when compared to networks that do not include per-flow identification); 
this is an inherent property of DetNet which has security implications 
which must be considered when determining if DetNet is a suitable 
technology for any given use case. Similar consideration may need to be 
given to the use of replicated packet flows, which result in increased 
surface for Reconnaissance attacks. In any case, the result must be that 
the confidentiality of the data is maintained to a degree sufficient for 
the use cases addressed by the given DetNet implementation.

To provide uninterrupted availability of the DetNet quality of service, 
provisions must be made against DOS attacks and delay attacks. To 
protect against DOS attacks, excess traffic due to malicious or 
malfunctioning devices must be prevented or mitigated, for example 
through the use of traffic admission control applied at the input of a 
DetNet domain, as described in Section 3.2.1.1, and through the fault 
mitigation methods described in Section 3.3.2.

To prevent DetNet packets from being delayed, protection must be 
provided against Man-In-The-Middle attacks, for example through use of 
authentication and authorization of devices within the DetNet domain.

Time synchronization methods are not specified by DetNet, however any 
time synchronization method used with DetNet must also be secured, using 
the security methods available for the given time synchronization 
mechanism, for example as described in [RFC7384].
In any case, the result must be that the DetNet is protected from DOS, 
delay, and time manipulation attacks to the extent sufficient for the 
use cases addressed by the given DetNet implementation.

DetNet use cases are known to have widely divergent security 
requirements. The intent of this section is to provide a baseline for 
security considerations which are common to all DetNet designs and 
implementations, without burdening individual designs with specifics of 
security infrastructure which may not be germane to the given use case. 
Designers and Implementers of DetNet systems are expected to take use 
case specific considerations into account in their DetNet designs and 
implementations.


Regards,
Janos



On 2/21/2019 9:32 PM, Lou Berger wrote:
> Hi Benjamin,
>
> On 2/20/2019 4:21 PM, Benjamin Kaduk wrote:
>> Hi Lou,
>>
>> On Wed, Feb 20, 2019 at 11:34:11AM -0500, Lou Berger wrote:
>>> On 2/20/2019 11:07 AM, Benjamin Kaduk wrote:
>>>> On Wed, Feb 20, 2019 at 09:33:34AM -0500, Lou Berger wrote:
>>>>> On 2/19/2019 10:44 PM, Benjamin Kaduk wrote:
>>>>>> I note that the DETNET WG is explicitly chartered with a work 
>>>>>> item for the
>>>>>> "overall architecture: This work encompasses ... and security 
>>>>>> aspects".
>>>>>> It seems incomplete to specify an architecture for a topic such as
>>>>>> deterministic networking without specifically considering what 
>>>>>> threats are
>>>>>> and are not in scope to be protected against.
>>>>> The working group certainly recognizes that security is an important
>>>>> topic and necessary part of the work. The WG's  approach to ensure 
>>>>> that
>>>>> this significant topic is sufficiently covered is to have a  document
>>>>> dedicated to the topic.  As you note below this work,
>>>>> draft-ietf-detnet-security, is not at the same level maturity - so
>>>>> please stay tuned.  Of course, the WG would welcome any input on this
>>>>> security draft now or even a full early-review or security area 
>>>>> advisor.
>>>> I do appreciate that the WG has taken the time to work on a dedicated
>>>> security document, that goes through the (tedious!) effort to 
>>>> tabulate the
>>>> various known attacker capabilities, threats, and their interactions.
>>>>
>>>> What I think is missing from the high-level architecture document is a
>>>> sense for what security goals the architecture intends to achieve.  
>>>> It's
>>>> fine to have this be separate from the nitty-gritty stuff in the 
>>>> separate
>>>> document, but these high-level questions can have an impact on the
>>>> high-level design of the protocol ecosystem as a whole.  We have 
>>>> mounds of
>>>> examples of "come up with a design; bolt security on as an 
>>>> afterthought"
>>>> working poorly or being nigh-impossible, and I haven't seen any 
>>>> attempt at
>>>> justification for why doing so here is likely to be any different.
>>>> Including the security concepts from the start and wholly 
>>>> integrating them
>>>> into the system tends to produce a much more elegant design and 
>>>> smoother
>>>> outcomes all around.
>>> We went back and forth on how much of the security topic to include in
>>> the architecture document and settled on the current text of section 5
>>> where just high level security requirements are identified. From your
>>> list below, the architecture covers the points you raise (non-detnet
>>> traffic impacting detnet traffic, and detnet traffic trying to use more
>>> than its allocation) mainly from a service delivery perspective.  It
>>> does mention "shaping" as a security concern, the document could expand
>>> these if helpful. But I think the real discussion point is how much of
>>> the security details should be in the base (vs dedicated) document  --
>>> and that you disagree with where the WG has drawn the line. Is this
>>> correct?
>> Well, it's not as much that I disagree about where the line is drawn, as
>> that I disagree with the characterization as "high level security
>> requirements".
>>
>> The first paragraph covers topics worth including here, certainly -- an
>> attacker that can introduce delay can inherently break the DetNet
>> guarantees, and there is no further defense.  But the text could 
>> probably
>> go further than its current version and explicitly call out that no
>> technical measures can defend against such delay, other than by
>> rerouting/avoiding the compromised position.
>>
>> The second paragraph also covers a topic worth noting, that entropy and
>> Murphy as as important of risks to consider as active attacks.
>>
>> The rest of the section/list don't seem to match up with the high-level
>> view, though -- "protection of the signaling protocol", but protection
>> against what?  Authentication and authorization are important parts of
>> security, but authorization is tied to actions and entities, not just
>> entities in vacuo.  For "identification and shaping of DetNet flows", if
>> security must cover them, what security properties are needed. Do we 
>> need
>> to provide integrity protection for the marking, or confidentiality
>> protection, too?  Does authentication/integrity need to be provided for
>> in-line or are out-of-band considerations in play?
>>
>> The rest of the document presents a good high level picture of what 
>> pieces
>> will be involved in a system, and how they fit together.  I'm hoping 
>> to see
>> a high-level picture of what attacks/failures the architecture does and
>> does not aim to protect against.  It's somewhat implied that we need to
>> protect against the failure of any single node or link (except at the
>> boundary) due to random faults; explicitly saying this would be a 
>> perfect
>> hting to include in the security considerations here!  Once we get 
>> beyond
>> entropy as an attack, into more active attack scenarios, though, we 
>> need to
>> consider what capabilities an attacker might have.  Do we protect 
>> against
>> an entity with the ability to inject various forms of traffic? Modify or
>> drop valid traffic?  Are there any (classes of) credentials that we 
>> assume
>> must be securely held, or will we attempt to protect against 
>> attackers that
>> have some privilege within the system?  (Note that misbehaving 
>> hardware can
>> sometimes present as similar or identical to such an attacker.)
>>
>> Does this give a better picture of what I'm thinking of as "high-level
>> security requirements"?  I don't necessarily need details of specific
>> hardware or credentials at play, and certainly not for the solutions, 
>> but I
>> want to have a clear picture of what the scope of future security 
>> analysis
>> will be.  "How will I be able to tell if the actual protocols meet the
>> security requirements of the architecture?"
>
> I'll get with authors (of both the architecture and security docs) and 
> see how much they think can be reasonably be added to this document -- 
> to be clear you *are* asking for a change in how the WG decide to 
> address this topic and what would go in which document.
>
> Lou
>
>> -Benjamin
>>
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