Re: [pkix] Proposed resolution to non-issued certificates - 2560bis

["Peter Rybar" <[e-mail]>]

Stefan,

 

I agree with David A. Cooper and Piyush.

 

And also retroactive revocation is not allowed in X.509.

The certificate status "revoked" in OCSP must be consistent with the status in CRL.

In this case it is not consistent because status "revoked" is proposed to be in OCSP but in the same time it is not included in CRL.

Validation will be different by CRL/OCSP!

 

Don't forget that also thisUpdate MUST be correctly used and included in OCSP response.

 

   - thisUpdate: The time at which the status being indicated is known to be correct.

 

It mans any new "correct" revocation MUST be with revocation value which is greater than value thisUpdate of any issued CRL/OCSP.

Including revocation date/time before value thisUpdate (of any already issued CRL/OCSP) is destruction of X.509 fundamental rules for validations.

Date and time of revocation MUST be only after value thisUpdate which is included in last issued CRL or OCSP.

 

[David A. Cooper]

 In your message yesterday you raised the issue of OCSP responders that have access to a database of issued certificates that are currently valid, but not of the certificates that were issued but that have now expired.

 As I explained before (http://www.ietf.org/mail-archive/web/pkix/current/msg31863.html), I believe that would be a non-backward compatible change.

 

[Piyush] Only scenario that matters is the one in which CA is compromised.

 In every other scenario the content of the response is irrelevant.

 Once the CA is compromised, no certificates issued by that CA could be trusted.

 

Peter Rybar

 

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Piyush Jain
Sent: Thursday, November 01, 2012 11:13 PM
To: 'Stefan Santesson'; [e-mail]
Subject: Re: [pkix] Proposed resolution to non-issued certificates - 2560bis

 

So far we've outlined 3 scenarios in which this response makes sense

1) Buggy Client

2) Malicious client

3) CA compromise

 

For 1 and 2, the content of the response does not matter.

That leaves us with 3 in which case caCompromise is right choice. And your

conclusion is right. Once the CA is compromised, no certificates issued by

that CA could be trusted.

 

BTW, I hope that there will be guidance in the updated draft on what to

include in CRL References extension in such cases.

It might suffice to say that the responder MUST not include the CRL

References extension if it is issuing revoked for fraudulently-issued

certificates.

 

-Piyush

 

> -----Original Message-----

> From: Stefan Santesson [mailto:[e-mail]]

> Sent: Thursday, November 01, 2012 12:38 PM

> To: Piyush Jain; [e-mail]

> Subject: Re: [pkix] Proposed resolution to non-issued certificates -

2560bis

> 

> To clear a few things up.

> 

> The current draft does not reflect the straw-poll. It will be updated to

> capture that which is/will be agreed.

> 

> CA compromise is a worse choice since it could be interpreted that no

certs

> from that CA can be trusted.

 

 

> certificateHold only affects that serialNumber and only temporary, thus it

is

> more suitable from a practical standpoint.

 

 

> 

> Yes, combined with the optional extension, "good" will be a positive

> statement of the existence of the cert. This is perfectly compliant with

the

> current "good" text saying "Response extensions may be used to convey

> additional information on assertions made by the responder regarding the

> status of the certificate such as positive statement about issuance,

validity,

> etc"

> 

> /Stefan

> 

> 

> 

> On 11/1/12 5:37 PM, "Piyush Jain" <[e-mail]> wrote:

> 

> >

> >

> >> -----Original Message-----

> >> From: Stefan Santesson [mailto:[e-mail]]

> >> Sent: Thursday, November 01, 2012 8:40 AM

> >> To: Piyush Jain; [e-mail]

> >> Subject: Re: [pkix] Proposed resolution to non-issued certificates -

> >2560bis

> >>

> >> As a short reply.

> >>

> >> No, the good response is still true from a very practical perspective.

> >> It is exactly as written.

> >[Piyush] I'm sure you have your reasons. But the obvious question that

> >comes to my mind is that if a responder returns revoked for non-issued,

> >than why can't good be considered a proof of issuance. The current text

> >fails to capture this.

> >>

> >> Secondly,

> >> Even if the major reason for allowing revoked for non-ussued certs is

> >> to detect/react to compromised CA situations,

> >[Piyush] That is the reason that has been cited. The way I see it is to

> >allow CAs to continue operations even after the compromise. I have not

> >seen a single discussion on how CA would react if starts getting such

> >requests.

> >It does give the CAs the tool to advertise the security of their

> >systems to unsuspecting customers who do not understand the OCSP trust

> >model.

> >

> >>this does NOT mean that any

> >> request for a non-issued cert is caused by a compromised CA.

> >

> >[Piyush]Nor does it mean that certificate was issued and put on hold,

> >which is what certifcateOnHold implies.

> >

> >>

> >> It can simply be caused by a bug in the requesting client or a

> >>deliberate

> >false

> >> request.

> >[Piyush] In either of these cases, what the responder returns has no

> >value.

> >The best response in such cases is to return transport level error

> >(HTTP 422).

> >I hope that the expectation here is not that this response will help

> >RPs to recover from software bugs or that it will teach malicious

> >clients to play nice.

> >

> >> It's therefore wrong to reply that the CA is compromised, unless you

> >>know  that the CA is compromised.

> >[Piyush] Only scenario that matters is the one in which CA is

compromised.

> >In every other scenario the content of the response is irrelevant.

> >>

> >> /Stefan

> >>

> >>

> >> On 11/1/12 4:23 PM, "Piyush Jain" <[e-mail]> wrote:

> >>

> >> >

> >> >

> >> >> -----Original Message-----

> >> >> From: Stefan Santesson [mailto:[e-mail]]

> >> >> Sent: Thursday, November 01, 2012 6:11 AM

> >> >> To: Piyush Jain; [e-mail]

> >> >> Subject: Re: [pkix] Proposed resolution to non-issued certificates

> >> >> -

> >> >2560bis

> >> >>

> >> >> In-line;

> >> >>

> >> >> On 11/1/12 12:12 AM, "Piyush Jain" <[e-mail]> wrote:

> >> >>

> >> >> >

> >> >> >

> >> >> >> -----Original Message-----

> >> >> >> From: [e-mail] [mailto:[e-mail]] On

> >> >> >> Behalf Of Stefan Santesson

> >> >> >> Sent: Wednesday, October 31, 2012 11:47 AM

> >> >> >> To: [e-mail]

> >> >> >> Subject: [pkix] Proposed resolution to non-issued certificates

> >> >> >> - 2560bis

> >> >> >>

> >> >> >> I didn't put up an end date for the straw-poll, but the trend

> >> >> >>seems clear.

> >> >> >>

> >> >> >> The results so far (if I counted right)

> >> >> >>

> >> >> >> Supporting #1: 22

> >> >> >> Supporting #2: 0

> >> >> >> Supporting #3 using "unknown": 6 Supporting #3 using

> >> >> >> "unauthorised: 2

> >> >> >>

> >> >> >> 6 persons supporting #1 has expressed various levels of

> >> >> >>support/demand for  an explicit declaration that the OCSP

> >> >> >>responder supports the enhanced  definition of "revoked" to

> >> >> >>include "no

> >issued".

> >> >> >>

> >> >> >> 1 person responded off-line supporting #1.

> >> >> >>

> >> >> >>

> >> >> >> If the trend reflects the opinion of the WG. This is my

> >> >> >> proposed

> >> >> >> resolution:

> >> >> >>

> >> >> >>

> >> >> >> 1) Extend the "revoked" response to also be allowed for

> >> >> >> non-issued certificates. Clearly stating that this is optional

> >> >> >> if and only if the

> >> >> >OCSP

> >> >> >> responder knows that the requested serial number has never been

> >> >> issued.

> >> >> >[Piyush] This requires changing the current text for 'good'.

> >> >> >Pasted for your reference

> >> >> >

> >> >> >The "good" state indicates a positive response to the status

> >>inquiry.

> >> >> >   At a minimum, this positive response indicates that the

> >>certificate

> >> >> >   is not revoked, but does not necessarily mean that the

> >>certificate

> >> >> >   was ever issued or that the time at which the response was

> >>produced

> >> >> >   is within the certificate's validity interval. Response

> >>extensions

> >> >> >   may be used to convey additional information on assertions

> >> >> > made

> >>by

> >> >> >   the responder regarding the status of the certificate such as

> >> >> >   positive statement about issuance, validity, etc.

> >> >>

> >> >> This is still true.

> >> >[Piyush]It is tree in theoretical sense, but incomplete and confusing.

> >> >The meaning of 'good' changes, if the responder returns revoked for

> >> >'fraudulently-issued' certificates.

> >> > In such cases, a positive proof implies that the certificate was

> >>issued.

> >> >Also, the last sentence in the above paragraph does not apply for

> >> >such responders.

> >> >>

> >> >> >

> >> >> >> 2) Specify that a "revoked" status for a non-issued certificate

> >> >> >> serial

> >> >> >number

> >> >> >> MUST have revocationTime set to Jan 1, 1970 and MUST set the

> >> >> >> revocationReason to certificateHold (6).

> >> >> >[Piyush] There were some objections on using certificateHold as

> >> >> >revocationReason for this purpose. CA compromise would be more

> >> >> >appropriate because the only scenario where this is beneficial is

> >> >> >when the CA is compromised.

> >> >>

> >> >> Absolutely not. The CA is not compromised just because I ask for a

> >> >>serial  number that was never issued.

> >> >

> >> >[Piyush] All this time, the reason to propose this change has been

> >> >that it helps the situation where certificates are fraudulently

> >> >issued. If the RP is not doing signature checking than this

> >> >discussion is moot. If RP has verified that signature is correct and

> >> >CA thinks it is not issued, it is caCompromise.

> >> >CA may be compromised or not. But this response is telling the RP

> >> >that if he thinks that certificate is signed by the CA, then it

> >> >implies that CA is compromised.

> >> >>

> >> >>

> >> >> >

> >> >> >> 2) Define a new optional non-critical extension declaring that

> >> >> >> OCSP responder returns "revoked" for non-issued certificates

> >> >> >> according to the updated standard. This extension MUST be

> >> >> >> present in all responses where the "revoked" response is

> >> >> >> returned as a result of a status request for a

> >> >> >non-

> >> >> >> issued certificate.

> >> >> >[Piyush] Are you proposing that the specification of this

> >> >> >extension would be part of OCSP or it would be published as a

> >> >> >separate specification?

> >> >> >I think that it should not be part of main OCSP specification,

> >> >> >given that it is useful only in the exceptional scenario where CA

> >> >> >gets compromised.

> >> >>

> >> >> Proposing to include it in the base standard. It can also be used

> >> >> to

> >> >measure

> >> >> whether an OCSP responder adopts this response behaviour even if

> >> >>the CA is  not compromised.

> >> >>

> >> >[Piyush] This is something new. So what are the benefits of this if

> >> >the CA is not compromised? What value does it add over signature

> checking?

> >> >And I thought that in one of you previous emails you said that there

> >> >was a WG decision to limit changes to RFC 2560 to what is necessary

> >> >to resolve previous ambiguity. Don't know if that is still the case.

> >> >>

> >> >> >>

> >> >> >>

> >> >> >> Rationale:

> >> >> >> The certificateHold reason feels important for one particular

> >reason.

> >> >> >>If a

> >> >> >CA is

> >> >> >> issuing certificates with sequential serial numbers, then it

> >> >> >> could be

> >> >> >possible

> >> >> >> to obtain a revoked response for a certificate serial number

> >> >> >> that is not

> >> >> >yet

> >> >> >> issued, but soon will be issued. That the certificate serial

> >> >> >> number is

> >> >> >currently

> >> >> >> not issued, does not mean that it never will, thus the

> >> >> >> certificateHold

> >> >> >reason

> >> >> >> seems more appropriate.

> >> >> >>

> >> >> >[Piyush] Given that a fraudulent certificate has been issued with

> >> >> >a serial number, the CA would eventually revoke the certificate

> >> >> >with this serial number and would not issue any newer certificate

> >> >> >with the same

> >> >> serial.

> >> >> >I think the confusion arises from the fact that we've been using

> >> >> >'not-issued' and 'fraudulently-issued' interchangeably. All this

> >> >> >time I'd been thinking that we are discussing the latter. If that

> >> >> >is indeed the case, caCompromise seems more appropriate.

> >> >>

> >> >> No, for reason above.

> >> >>

> >> >> >

> >> >> >> The date 1 Jan, 1970 is appropriate since it is common in

> >> >> >> programming languages to express time as milliseconds since jan

> >> >> >> 1,

> >> 1970.

> >> >> >> Selecting

> >> >> >this

> >> >> >> time avoids time expression as a negative integer.

> >> >> >>

> >> >> >> This date translates to (java):

> >> >> >> Date revocationTime = new Date(0);  //Jan 1st, 1970

> >> >> >>

> >> >> >> The extension would be a simple OID with no data structure and

> >> >> >> MUST not be set to critical.

> >> >> >>

> >> >> >>

> >> >> >> Question:

> >> >> >> Would it make sense to require an OCSP responder that adopts

> >> >> >>the expanded use of "revoked" to always include the new

> extension?

> >> >> >> It would add the benefit that someone receiving "good" can know

> >> >> >>that the  OCSP responder has checked that the certificate in

> >> >> >>fact has been issued by  the CA.

> >> >> >> In such case it may be reasonable to add an optional data

> >> >> >>structure which  MAY contain a hash of the cert.

> >> >> >> Such hash would make the positive confirmation even stronger,

> >> >> >>adding proof  of existence of the certificate.

> >> >> >[Piyush] I hope that you realize that big enterprise PKI

> >> >> >deployments use OCSP and CRLs interchangeably. And with this

> >> >> >proposal OCSP becomes more authoritative than CRL.

> >> >> >So I guess the next step would be to change the basic path

> >> >> >validation algorithm to drop the use of CRLs in favor of OCSP and

> >> >> >also drop the signature verification (off course if the RP knows

> >> >> >that his OCSP responder issues stronger positive confirmations).

> >> >>

> >> >> It is not part of this work to update CRL processing or path

> >validation.

> >> >[Piyush] Are you saying that there is no need to evaluate how this

> >> >work affects other standards created by pkix.

> >> >>

> >> >> >>

> >> >> >> But perhaps this will bee too much to agree on :)

> >> >> >>

> >> >> >[Piyush] How about a thinner profile of SCVP that could address

> >> >> >everything you are trying to achieve in OCSP.

> >> >>

> >> >> It is neither part of this work to update SCVP. Just to update OCSP.

> >> >[Piyush] SCVP does not need to be updated. It already has provisions

> >> >for what you are trying to duplicate in OCSP.

> >> >>

> >> >> /Stefan

> >> >>

> >> >

> >> >

> >> >_______________________________________________

> >> >pkix mailing list

> >> >[e-mail]

> >> >https://www.ietf.org/mailman/listinfo/pkix

> >>

> >

> >

> 

 

 

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