Re: [secdir] [v6ops] Secdir last call review of draft-ietf-v6ops-transition-ipv4aas-11

[Christian Huitema <[e-mail]>]

Pointing to the RFC8415 security section would definitely help. What is
specific about your draft is that attackers can leverage the DHCPv6
issue and mislead nodes into choosing transition schemes in the wrong
order. This is an additional exploitation mechanism on top of  the
existing issues mentioned in the DHCPv6 RFC.

I would also mention that these security issues are hard to mitigate and
that secure environments might require other configuration methods.

This also begs the larger question about why we have so many transition
mechanisms in the first place, and why the local nodes even need to be
aware about them. It seems that this could be radically simplified, by
having the router either advertise IPv4 connectivity using traditional
IPv4 means, or advertise a NAT64 prefix if it expects local nodes to
perform their own mapping.

On 12/13/2018 11:44 PM, [e-mail] wrote:
> Christian,
>
> As mentioned by Jordi, RFC8026 already describes the attack vector you mentioned. 
>
> Wouldn't pointing to https://tools.ietf.org/html/rfc8415#section-22 be sufficient here? 
>
> Cheers,
> Med
>
>> -----Message d'origine-----
>> De : ietf [mailto:[e-mail]] De la part de Christian Huitema
>> Envoyé : vendredi 14 décembre 2018 08:26
>> À : JORDI PALET MARTINEZ; [e-mail]
>> Cc : [e-mail]; [e-mail]; draft-ietf-v6ops-transition-
>> [e-mail]
>> Objet : Re: [v6ops] Secdir last call review of draft-ietf-v6ops-transition-
>> ipv4aas-11
>>
>>
>> On 12/13/2018 2:09 PM, JORDI PALET MARTINEZ wrote:
>>> Hi Christian,
>>>
>>> Thanks a lot for your review.
>>>
>>> Please see below in-line.
>>>
>>> I'm working in a new version according to the comments got from the ops
>> review as well, so will be able to integrate yours very quickly.
>>> Regards,
>>> Jordi
>>>
>>>
>>>
>>> -----Mensaje original-----
>>> De: v6ops <[e-mail]> en nombre de Christian Huitema
>> <[e-mail]>
>>> Fecha: jueves, 13 de diciembre de 2018, 21:50
>>> Para: <[e-mail]>
>>> CC: <[e-mail]>, <[e-mail]>, <draft-ietf-v6ops-transition-
>> [e-mail]>
>>> Asunto: [v6ops] Secdir last call review of draft-ietf-v6ops-transition-
>> ipv4aas-11
>>>     Reviewer: Christian Huitema
>>>     Review result: Has Issues
>>>
>>>     I have reviewed draft-ietf-v6ops-transition-ipv4aas-11 as part of the
>>>     security directorate's ongoing effort to review all IETF documents
>>>     being processed by the IESG.  These comments were written primarily for
>>>     the benefit of the security area directors.  Document editors and WG
>> chairs
>>>     should treat these comments just like any other last call comments.
>>>
>>>     The summary of the review is "ready with issue".
>>>
>>>     The document describes solution for providing "IPv4 as a service", i.e.
>>>     provision of IPv4 as a service over an IPv6 only network.
>>>     It calls this support "transition as a service".
>>>
>>>     For various reasons, IETF working groups have standardized not just one
>> but
>>>     five different mechanisms for providing this transition: 464XLAT
>> [RFC6877],
>>>     Dual-Stack Lite [RFC6333], Lightweight 4over6 (lw4o6) [RFC7596],
>>>     MAP-E [RFC7597], and MAP-T [RFC7599]. (I am sure that Monty Python
>> could have
>>>     produced a nice sketch about that.) The purpose of the draft is to
>>>     state how home routers (a.k.a. customer premise equipment, CPE) should
>>>     inform local devices about which of the mechanisms are available, which
>>>     should be preferred, and what parameters should be used when deploying
>>>     the chosen services. This is done using the DHCPv6 "S46" option
>>>     specified in RFC 8026.
>>>
>>>     The draft also makes specific recommendation regarding the use of the
>> UPnP and
>>>     PCP services, by requiring specific error codes when a requested port
>> mapping
>>>     is not available through the specified transition technology.
>>>
>>>     The security section briefly points to the "Basic Requirements for IPv6
>>>     Customer Edge Routers" specified in RFC 7084, and to the security
>>>     section of each of the RFC describing the security technologies, and
>> implicitly
>>>     argues that there are no other security issues. I think that is
>> insufficient.
>>>     The draft introduces a reliance on the DHCPv6 "S46" option for
>> assessing the
>>>     relative priority of different transition technologies. An attacker
>> could spoof
>>>     the DHCPv6 response, and direct client traffic to a different
>> technology than
>>>     selected by the service provider. This could be used, for example, to
>> capture
>>>     IPv4 traffic in an IPv6 network and send it to a route chosen by the
>> attacker.
>>>     The attack might also be used in a dual stack network that does not
>> support
>>>     any transition technology. I don't understand how this attack is
>> mitigated.
>>> Not sure if you will suggest here that we should say something about the
>> security considerations already mention in RFC8026. In general all those are
>> generic DHCPv6 security considerations I think.
>>
>> Basically, the devices should be programmed to ignore DHCPv6 if they
>> have another more secure way of getting their configuration data. Plus,
>> apply general defense against DHCPv6 hacks in the network, etc. I
>> understand that your draft is meant to inform the building of CPEs, but
>> its effect is generalization of an unsafe mechanism.
>>
>>
>>>     Nits:
>>>
>>>     The introduction uses the acronym WAN without spelling out "Wide Area
>> Network".
>>>     Also, WAN is used as substitute for local Internet Service Provider
>> network. We could
>>>     debate whether such networks are always "wide area", by opposition to
>> say
>>>     "metropolitan" or "regional". This is the same convention used in RFC
>> 7084 that
>>>     this document updates. It is arguably defined by reference, but
>> spelling it out
>>>     would be nice.
>>>
>>> Will do.
>>>
>>>
>>>     The comparison with RFC7084 section includes a mangled sentence:
>>>
>>>        This document doesn't include support for 6rd ([RFC5969]), because
>> as
>>>        in an IPv6-in-IPv4 tunneling.
>>>
>>> Typo, sorry the correct sentence was:
>>>        This document doesn't include support for 6rd ([RFC5969]), because
>> is
>>>        an IPv6-in-IPv4 tunneling.
>>        This document doesn't include support for 6rd ([RFC5969]), because it
>> is
>>        an IPv6-in-IPv4 tunneling.
>>
>>>     Please rephrase. Please also rephrase the next sentence, for similar
>> reasons:
>>>        Regarding DS-LITE [RFC6333], this document includes slightly
>>>        different requirements, because the PCP ([RFC6887]) support and the
>>>        prioritization of the transition mechanisms, including dual-stack.
>>>
>>> I think it is much clear this way:
>>>
>>>        Regarding DS-LITE [RFC6333], this document includes slightly
>>>        different requirements, related to the support of PCP ([RFC6887]),
>>>        IGD-PCP IWF [RFC6970] and the prioritization of the transition
>>>        mechanisms, including dual-stack.
>> OK.
>>
>>
>>>
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>>>
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