Re: [sidr] Ben Campbell's Discuss on draft-ietf-sidr-rpki-validation-reconsidered-08: (with DISCUSS and COMMENT)

[Alvaro Retana <[e-mail]>]

Tim:

Hi!

FWIW, I agree with Ben that the text doesn’t resolve his concerns, and it
doesn’t reflect what you said on the thread.  I think you two are actually
saying the same thing (or pretty close), but using different words.

I think that at least (+ the specific points made by Ben below) the text
needs to explicitly expand the new Abstract text throughout the rest of the
document, potentially include an example of mixed OIDs, and talk about the
use of the new OIDs in with the old procedure.  Some of these things are
sort of implicit already; for example, using the new OIDs with the old
procedure is not specified in rfc6487…but explicitly mentioning it in this
document won’t hurt.

Thanks!

Alvaro.

On October 27, 2017 at 5:57:08 PM, Ben Campbell ([e-mail]) wrote:

Hi Tim,

(Apologies for the delayed response)

Sorry, but these changes do not resolve my concern. Specifically, I think
implementors reading this draft will create inconsistent of mixed-OID
chains. Commenting specifically:

Section 4.2.1 was changed from saying that the new OID indicates that the
procedures in 4.2.4.4 are to be used to saying that the new OID “drives the
decision” in step 8 4.2.4.4. “Drives the decision” is vague without details
about how the how the rule in step 8 of 4.2.4.4 actually uses that
information. There has been no change in 4.2.4.4 to address this. Sections
4.2.2.5 and 4.2.2.6 still say that the new OIDs indicate the procedures in
4.2.4.4 are to be used. The “rather than” clause has been removed, but I
don’t think that changes anything, and it’s still a reasonable (and likely)
interpretation to assume that certificates with the old OID will follow the
old validation policy.

I don’t see how the new text in the abstract changes anything. (And if it
did, I would argue the abstract is the wrong place to say it.)

I think fixing this would require one of the following changes:

1) Disallow mixed-OID chains, or…

2) The following changes to allow mixed-OID chains:
- Explicit text that implementations MAY/SHOULD use the new validation
policy even for certs in the chain that do not include the OID. (Perhaps
only if the root cert included it?)
- Change the description of the OID to say the OID is an input into the new
validation rules, not a discriminator about which rules to use. (Which, if
I understand correctly might remove the point of a new OID in the first
place. Maybe it only matters in the root cert?)
- Add text to 4.2.4.4 to explain exactly how the rules use the OID as an
input.

Thanks,

Ben.

> On Oct 6, 2017, at 8:36 AM, Tim Bruijnzeels <[e-mail]> wrote:
>
> Dear Ben, Alvaro, others,
>
> Please find a new version -09 attached. Not uploaded yet, because I
thought it better to discuss here first and get clarity.
>
> With regards to the changes. I understand that the non-normative text in
the abstract and the sections where the new OIDs are introduced in -08 were
inconsistent with the intent (and normative) text in section 4.2.2.4 to
have one validation algorithm that can be used to validate both current
RFC6487 Resource Certificates as well as Resource Certificates that use the
new OIDs introduced here.I hope that this new version eliminated this
ambiguity. Ben, can you please let us know if this version addresses your
concerns?
>
> Alvaro, it’s of course your prerogative to take this back to IETF or WG
last call if you feel this confusion was widespread and let to
misinterpretations. For our part I do want to re-state though that the
normative text in 4.2.2.4 was quite explicit, as well as the deployment
considerations section where it’s explicitly mentioned that this is a per
CA choice and a mix of OIDs in a tree is possible. I also referred to this
in my email to the WG when -07 was published on 3 October 2016. So, it was
certainly not our intent to have any unclarity or inconsistency about this
in earlier sections in the document.
>
> Please let me know what you think. If we can proceed, then I can update
this document with the other review comments and upload, and hopefully get
this rolling again. But first I want to make sure that the issues above are
resolved.
>
> Kind regards,
>
> Tim Bruijnzeels
>
> =====
>
> For the impatient, we made changes to the following sections:
>
> Abstract
>
> This document specifies an alternative to the certificate validation
procedure specified in RFC 6487 that reduces aspects of operational
fragility in the management of certificates in the RPKI, while retaining
essential security features.
>
> Where the procedure specified in RFC 6487 requires that Resource
Certificates are rejecting entirely if they are found to over-claim any
resources not contained on the issuing certificate, the validation process
defined here allows an issuing Certificate Authority to chose to
communicate that such Resource Certificates should be accepted for the
intersection of their resources and the issuing certificate.
>
> This choice is signalled by form of a set of alternative Object
Identifiers (OIDs) of RFC 3779 X.509 Extensions for IP Addresses and AS
Identifiers, and certificate policy for the Resource Public Key
Infrastructure (RFC 6484). It should be noted that in case these OIDs are
not used for any certificate under a Trust Anchor, the validation procedure
defined here has the same outcome as the procedure defined in RFC 6487
>
> Furthermore this document provides an alternative to ROA (RFC 6482), and
BGPSec Router Certificate (BGPSec PKI Profiles - publication requested)
validation.
>
> 4.2.1. Certificate Policy (CP) for use with validation reconsidered in
the Resource PKI (RPKI)
>
> ...
> This alternative Certificate Policy is the same as the Certificate Policy
described in [RFC6484], except that it is used to drive the decision in
step 8 of the validation procedure described in Section 4.2.4.4.
>
> 4.2.2.1. OID for id-pe-ipAddrBlocks-v2
>
> This document request an OID for the extension id-pe-ipAddrBlocks-v2
(id-pe TBD2). This OID MUST only be used in conjunction with the
alternative Certificate Policy OID defined in Section 4.2.1.
> ….
>
> 4.2.2.3. OID for id-pe-autonomousSysIds-v2
>
> This document request an OID for the extension id-pe-autonomousSysIds-v2
( id-pe TBD3). This OID MUST only be used in conjunction with the
alternative Certificate Policy OID defined in Section 4.2.1.
> ….
>
>
> 4.2.2.5. Amended IP Address Delegation Extension Certification Path
Validation
>
> Certificate path validation is performed as specified in Section 4.2.4.4.
>
> 4.2.2.6. Amended Autonomous System Identifier Delegation Extension
Certification Path Validation
>
> Certificate path validation is performed as specified in Section 4.2.4.4.
>
> <draft-ietf-sidr-rpki-validation-reconsidered-09.txt>
>
>
>
>> On 22 Sep 2017, at 22:56, Ben Campbell <[e-mail]> wrote:
>>
>>>
>>> On Sep 19, 2017, at 6:54 AM, Tim Bruijnzeels <[e-mail]> wrote:
>>>
>>>
>>>> On 18 Sep 2017, at 23:36, Ben Campbell <[e-mail]> wrote:
>>>>
>>>>>
>>>>> On Sep 18, 2017, at 8:15 AM, Tim Bruijnzeels <[e-mail]> wrote:
>>>>>
>>>>> Hi Ben, all,
>>>>>
>>>>>> On 15 Sep 2017, at 23:20, Ben Campbell <[e-mail]> wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> See comments inline. I apologize in advance if I am just being
dense, and I cannot claim to be an expert on how one applies a path
validation policy OID in general.
>>>>>>
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> Ben.
>>>>>>
>>>>>>> On Sep 14, 2017, at 7:00 AM, Tim Bruijnzeels <[e-mail]> wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Sure. I also proceeded to discuss your and Terry’s points, but
apparently not to the desired level of clarity. Let me try again here, and
tackle both your and Terry’s discuss items since they are closely related.
>>>>>>>
>>>>>>>> Is it legal to mix certificate policies in a given cert path? The
last
>>>>>>>> paragraph of section 5 implies that you can, but doesn't say so
explicitly.
>>>>>>>
>>>>>>> According to this document it is. Section 4.2.2.4 starts with the
following:
>>>>>>>
>>>>>>> The following is an amended specification for path validation to be
>>>>>>> used in place of section 7.2 of [RFC6487] allowing for the
validation
>>>>>>> of both certificates following the profile defined in [RFC6487], as
>>>>>>> well as certificates following the profile described above.
>>>>>>>
>>>>>>> So the intent here is to describe a single validation algorithm
that can be used to validate a chain of old OIDs only (in which case it’s
semantically equivalent to the current spec in RFC6487), new OIDs only (as
described in the example in 4.3), or indeed a mix - but no example is given
on how that works out.
>>>>>>>
>>>>>>>
>>>>>>>> If you _can_ mix policies, what happens if you do? If I read the
rules in 4.2.4.4.
>>>>>>>> correctly (and it's likely that I am not), if you run into a cert
in the chain
>>>>>>>> that does not follow this profile, it's likely to give a null
VRS-IP or VRS-AS
>>>>>>>> value, which would seem to invalidate an certificate further down
the chain
>>>>>>>> that _does_ follow this policy?
>>>>>>>
>>>>>>>
>>>>>>> The “Validated Resource Sets” (VRS-*) are always calculated,
regardless of whether the old or new OIDs are used.
>>>>>>
>>>>>> This is where I am confused. The calculation of VRS is described in
this draft in the amendment to the path validation in section 7.2 of 6487.
I assumed that the amended path validation procedure only applies with the
“new” OID. Is that incorrect? If so, can you point to the text that states
that? (It’s entirely possible I missed something, or completely
misunderstand how the OIDs are applied. )
>>>>>
>>>>> First paragraph of 4.2.2.4:
>>>>>
>>>>> "The following is an amended specification for path validation to be
used in place of section 7.2 of [RFC6487]
>>>>> allowing for the validation of both certificates following the
profile defined in [RFC6487], as well as certificates
>>>>> following the profile described above."
>>>>>
>>>>> So, yes, as far as I am concerned the intent was to have this cover
both the old and new OIDs. Where the algorithm if applied to old OID only
is semantically equivalent to section 7.2 of RFC6487 - or at least: it has
the same outcome.
>>>>>
>>>>
>>>> That intent surprises me, I was under the impression the entire
document was specific to the new OIDs. This seems to be supported by this
text in the abstract:
>>>>
>>>> "The use of this updated procedure is signalled by form of a set of
alternative Object Identifiers (OIDs) indicating that the alternative
version of RFC 3779 X.509 Extensions for IP Addresses and AS Identifiers,
and certificate policy for the Resource Public Key Infrastructure ( RFC
6484) defined in this document should be used.”
>>>>
>>>> … and in the specific case of the certificate validation policy OID,
there is this text in 4.2.1:
>>>>
>>>> "This alternative Certificate Policy is the same as the Certificate
Policy described in [
>>>> RFC6484], except that it indicates that the validation rules described
in
>>>> Section 4.2.4.4 are to be used.”
>>>>
>>>> If the rules in 4.2.4.4 are used even when that OID is not present,
then I’m confused about what the OID signals in the first place.
>>>
>>> The OIDs are used to drive a decision in the rules described in
4.2.4.4.
>>> = Old OIDs -> reject over-claim, this has the same result as section
7.2 in RFC6487
>>> = New OIDs -> warn on over-claim
>>
>> Are you suggesting the text “should” say that, or “does” say that? As
written, the OID seems to drive the selection about whether you use the
rules in 4.2.4.4 or not. But I think you are saying that, if you implement
these OIDs, you SHOULD/MAY use the rules in 4.2.4.4 all the time, but use
the OID as an input to those rules. Is that correct?
>>
>>
>>>
>>> So as far as clarity goes, it might be better to either leave out the
set regarding the need for the different OIDs in their respective sections,
or say “This OID is used to in the decision process of the validation rules
described in 4.2.4.4.
>>
>> I’m not sure what you mean by the former. If you go with the latter,
then the rules in 4.2.4.4 will need to be explicit in how the OID is used
in that process.
>>
>>>
>>>>> If this needs to be more explicit I am happy to accept a suggestion -
as an author knowing my own intentions, it’s not always trivial to see how
others would interpret text differently.
>>>>
>>>> I’m not sure this is just a matter of clarification. The text I
mention above explicitly says the OID signals the use of the amended CP. I
have to assume that was the working group intent, and what was understood
by people during IETF LC. If that is _not_ the intent, we would need some
degree of consensus to change that text. ( I suspect that would mean going
back to the WG or IETF LC, but I will leave that to Alvaro to decide.)
>>>>
>>>
>>> It was my assumption that my intent was clear.
>>>
>>> But I will accept whatever Alvaro decides on this.
>>>
>>>
>>>> My strictly personal opinion is that it would be _really_ confusing to
have some aspects of the new CP apply even when the new OID is not used.
>>>
>>> The assumption on my part here was that RPs can decide to support this
RFC-to-be and then use section 4.2.4.4 to validate old and new CP alike.
>>>
>>> The process described in 4.2.4.4 when used for old OIDs only has the
same outcome as section 7.2 of RFC 6487. It’s true that “Validated Resource
Sets” are not named in RFC6487, but in a tree where only old OIDs are used
one will find that the Validated Resource Set for a given *valid*
certificate always matches the certificate itself.
>>
>> As I mentioned above, if the idea is to always use the rules in 4.2.4.4,
and use the OID to drive decisions _within_ those rules, the rules need to
be updated with the explicit details.
>>
>>>
>>> Thanks
>>> Tim
>>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>> Ben.
>