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RE: Signer certificate discovery for CRLs

To: "Denis Pinkas" <Denis.Pinkas@xxxxxxxx>
Subject: RE: Signer certificate discovery for CRLs
From: "Stefan Santesson" <stefans@xxxxxxxxxxxxx>
Date: Mon, 18 Oct 2004 13:19:27 +0100
Cc: "Santosh Chokhani" <chokhani@xxxxxxxxxxxx>, "pkix" <ietf-pkix@xxxxxxx>
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Thread-index: AcS0/XTojw2qZj1iSPaZLFj2w1ClggAC99eQ
Thread-topic: Signer certificate discovery for CRLs
Thanks Denis,

I now finally understand your SIA alternative.

There are some major problems with it though.

1) How can the RP know what certificate's SIA it would use to find the
CRL signer cert?

You just picked the right certificate in my example since I gave that
information in the example. But the RP don't know that path, it only
knows the path of the EE cert and the name of the CRL issuer!

2) And even if RP knew the path beforehand, finding THE one CRL signer
certificate from a CRL AIA is much more direct and efficient than
finding among all issued certificates from a CA the 1 out of x issued
certificates that is the CRL Issuer cert.

3) Using SIA in the examples requires available directories and
directory enabled clients. How do you solve the problem if either of
these is not available?


Do you seriously suggest that use of SIA is a better and more effective
way to address this problem or are you just pointing out the fact that
there are SOME cases where use of SIA may work in theory?


Stefan Santesson
Microsoft Security Center of Excellence (SCOE)
 

> -----Original Message-----
> From: Denis Pinkas [mailto:Denis.Pinkas@xxxxxxxx]
> Sent: den 18 oktober 2004 12:28
> To: Stefan Santesson
> Cc: Santosh Chokhani; pkix
> Subject: Re: Signer certificate discovery for CRLs
> 
> Stefan,
> 
> > Denis,
> 
> > If I get you right you mean that one can always successfully use AIA
and
> > SIA in certs to solve discovery of CRL signer cert.
> > Others on this list (me included) don't understand how. It would
> > therefore be useful if you told us.
> >
> > I'll try to explain the problem from my perspective one more time.
> 
> Thanks.
> 
> > Note: "->" in these examples means "issued by"
> 
> Fine.
> 
> > Case 1 - indirect CRL:
> >
> > Cert path is:  EE_Cert -> CA_1 -> Root-CA
> > CRL path for EE_Cert is:  CRL -> CRL_Issuer_B -> Root-CA
> 
> This means Root-CA has nominated CA_1 and a CRL_Issuer_B and that CA_1
has
> chosen to use CRL_Issuer_B for revocation checking for some
certificates.
> 
> > Scenario:
> > Relying party has access to the cert path, discovers the CRL through
CDP
> > in EE_Cert.
> 
> If there is no attack on the objects stored at the CRL DP, the CRL
Issuer
> from that CRL is CRL_Issuer_B. Now the relying party needs to get the
> certificate isued by Root-CA for CRL_Issuer_B. If Root-CA has included
a
> SIA
> extension in his self-signed certificate, then using that extension
allows
> to get the CRL_Issuer_B certificate issued by the Root-CA.
> 
>  > The RP searches the location specified in SIA through
> > id-ad-caRepository in the CA_1 cert but finds nothing useful since
> > revocation is subordinated to another entity (CRL_Issuer_B)
> 
> Correct, but looking in Root-CA allows to find something useful, if
the
> self-signed certificate includes a SIA extension.
> 
> > In this case, the problem could be solved if an AIA in the CRL
indicated
> > the access location of the CRL Issuer cert.
> 
> This would be an *alternative* way.
> 
> > Case 2 - re-keyed CA.
> >
> > Cert path is:  EE_Cert -> CA_1(old key) -> Root-CA
> > CRL path for EE_Cert is:  CRL -> CA_1(new key) -> Root-CA
> 
> This means that the EE_Cert chain has been created with CA_1(old key)
and
> that the CRL issuer that was originaly used when the EE_Cert was
created
> has
> been changed and a new CRL Issuer got a certificate under CA_1(new
key)
> and
> is now the legitimate CRL issuer for the CRL DP originally mentionned
in
> the
> EE_Cert.
> 
> > The 2 CA_1 certificates above (old key and new key) are issued to
> > different subject keys belonging to the same CA (same name).
> > The cert CA_1(old key) was issued before creation of cert CA_1(new
key)
> > and have thus no reference to CA_1(new key) in its SIA
> >
> > Scenario:
> > RP discovers the CRL for the EE_Cert through the CDP but doesn't
possess
> > the CRL issuer cert. The RP client searches the SIA of the CA_1(old
key)
> > but finds no direct reference to the CRL signer cert. Since the RP
> > client has no access to a directory where the CRL signer cert could
be
> > found through directory lookup, cert validation fails.
> 
> Correct, but looking in Root-CA allows to find something useful, if
the
> self-signed certificate includes a SIA extension.
> 
> > In this scenario the problem could be solved through an AIA in the
CRL.
> 
> This would be an *alternative* way.
> 
> Denis
> 
> >
> >
> >
> > Stefan Santesson
> > Microsoft Security Center of Excellence (SCOE)
> >
> >
> >>-----Original Message-----
> >>From: Denis Pinkas [mailto:Denis.Pinkas@xxxxxxxx]
> >>Sent: den 15 oktober 2004 17:30
> >>To: Stefan Santesson
> >>Cc: Santosh Chokhani; pkix
> >>Subject: Re: Signer certificate discovery for CRLs
> >>
> >>Stefan,
> >>
> >>
> >>>Denis,
> >>
> >>>Unfortunately I fail to understand your questions, issues and
> >>
> > requests.
> >
> >>The sentence below demonstrates that you understand the issue.
> >>
> >>
> >>>It would be very useful if you could explain how current mechanisms
> >>
> > can
> >
> >>>be used in a simple and straightforward manner to discover CRL
> >>
> > signer
> >
> >>>certificates in ALL the use cases discussed, mainly re-keyed CA and
> >>>indirect CRLs.
> >>
> >>You are also reversing the question. Using your terms, my question
> >
> > would
> >
> >>be:
> >>
> >>"It would be very useful if you could explain how current mechanisms
> >>CANNOT
> >>be used in a simple and straightforward manner to discover CRL
signer
> >>certificates in ONE or MORE the use cases discussed, mainly re-keyed
> >
> > CA
> >
> >>and
> >>indirect CRLs."
> >>
> >>Denis
> >>
> >>
> >>>Stefan Santesson
> >>>Microsoft Security Center of Excellence (SCOE)
> >>>
> >>>
> >>>
> >>>
> >>>>-----Original Message-----
> >>>>From: owner-ietf-pkix@xxxxxxxxxxxx
> >>>
> >>>[mailto:owner-ietf-pkix@xxxxxxxxxxxx]
> >>>
> >>>
> >>>>On Behalf Of Denis Pinkas
> >>>>Sent: den 14 oktober 2004 17:13
> >>>>To: Santosh Chokhani
> >>>>Cc: 'pkix'
> >>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>
> >>>>
> >>>>Santosh,
> >>>>
> >>>>
> >>>>
> >>>>>Denis:
> >>>>
> >>>>>With the three assumptions/constraints I provided, how would you
> >>>>
> >>>locate
> >>>
> >>>
> >>>>the
> >>>>
> >>>>
> >>>>>CRL issuer certificate for the two examples using 3280 extensions
> >>>>
> >>>and
> >>>
> >>>
> >>>>>without putting AIA in the CRL?
> >>>>
> >>>>As far as I understand, the three assumptions are:
> >>>>
> >>>>1.  You are directory challenged; and
> >>>>    [I do not understand what this means]
> >>>>2.  You use AIA to develop the path; and
> >>>>    [It does not matter]
> >>>>3.  You develop the path from the end entity to trust anchor
> >>>>    [Could also be the contrary].
> >>>>
> >>>>If this is not correct, thus please correct.
> >>>>
> >>>>Then my request is: "using ANY OF the current extensions that are
> >>>
> >>>defined
> >>>
> >>>
> >>>>in
> >>>>RFC 3280", which includes SIA.
> >>>>
> >>>>In your explanations  you said :
> >>>>"if you do no deal with SIA et. al"
> >>>>
> >>>>This last assumption is neither part of the three assumptions and
> >>>
> > does
> >
> >>>not
> >>>
> >>>
> >>>>conform to my request.
> >>>>
> >>>>Denis
> >>>>
> >>>>
> >>>>
> >>>>>That is my point.
> >>>>>
> >>>>>-----Original Message-----
> >>>>>From: Denis Pinkas [mailto:Denis.Pinkas@xxxxxxxx]
> >>>>>Sent: Thursday, October 14, 2004 6:22 AM
> >>>>>To: Santosh Chokhani
> >>>>>Cc: 'pkix'
> >>>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>>
> >>>>>
> >>>>>Santosh,
> >>>>>
> >>>>>You misread my request. I said:
> >>>>>
> >>>>>"For the time being, I would like that you provide an example
> >>>>
> > where,
> >
> >>>>when
> >>>>
> >>>>
> >>>>>using the current extensions that are defined in RFC 3280, it
will
> >>>>
> >>>NOT
> >>>
> >>>
> >>>>be
> >>>>
> >>>>
> >>>>>possible to locate a CRL Issuer certificate."
> >>>>>
> >>>>>Maybe I would have needed to be clearer and say :
> >>>>>
> >>>>>"For the time being, I would like that you provide an example
> >>>>
> > where,
> >
> >>>>when
> >>>>
> >>>>
> >>>>>using ANY OF the current extensions that are defined in RFC 3280,
> >>>>
> > it
> >
> >>>>will
> >>>>
> >>>>
> >>>>>NOT be possible to locate a CRL Issuer certificate."
> >>>>>
> >>>>>The examples you provide below do not fulfil this request.
> >>>>>
> >>>>>The assumption is that there exists a path to be tested for
> >>>>
> >>>revocation
> >>>
> >>>
> >>>>>checking (and that it does not matter to know which way it has
been
> >>>>>constructed).
> >>>>>
> >>>>>I am not saying that using AIA in CRL might not be useful, but I
am
> >>>>
> >>>>still
> >>>>
> >>>>
> >>>>>lacking the demonstration that there would be no other way.
> >>>>>
> >>>>>Denis
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>Denis:
> >>>>>>
> >>>>>>Two examples are very simple: one for direct CRL Issuer and one
> >>>>>
> > for
> >
> >>>>>>Indirect CRL Issuer.
> >>>>>>
> >>>>>>Let us make the following assumptions that Stefan was making:
> >>>>>>
> >>>>>>1.  You are directory challenged; and
> >>>>>>2.  You use AIA to develop the path; and
> >>>>>>3.  You develop the path from the end entity to trust anchor.
> >>>>>>
> >>>>>
> >>>>>>From what I know of MS CAPI, these are reasonable
> >>>>>
> >>>>>
> >>>>>>assumptions/constraints.
> >>>>>>
> >>>>>>Now the examples.
> >>>>>>
> >>>>>>Example 1: Direct CRL Issuer
> >>>>>>
> >>>>>>The certificate trust path is:
> >>>>>>Root --> CA1 --> CA 2, old key --> Denis
> >>>>>>
> >>>>>>The CRL trust path is:
> >>>>>>Root --> CA1 --> CA 2, new key --> CRL
> >>>>>>
> >>>>>>(Note: We do not do self-issued certificate since there is no
> >>>>>
> >>>simple,
> >>>
> >>>
> >>>>>>secure way to check their revocation status).
> >>>>>>
> >>>>>>Now, with AIA in CRL, finding the CA2, new key certificate is
> >>>>>>straightforward.  How would you find it if you do no deal with
SIA
> >>>>>
> >>>et.
> >>>
> >>>
> >>>>>>al.
> >>>>>>
> >>>>>>Example 2: Indirect CRL Issuer
> >>>>>>
> >>>>>>The certificate trust path is:
> >>>>>>Root --> CA1 --> CA 2 --> Denis
> >>>>>>(Note: Denis's certificate points to CRL DP of an indirect CRL
> >>>>>
> >>>issued
> >>>
> >>>
> >>>>>>by CAI.
> >>>>>>
> >>>>>>The CRL trust path is:
> >>>>>>Root --> CAI --> CRL
> >>>>>>
> >>>>>>Now, with AIA in CRL, finding the CAI certificate is
> >>>>>
> >>>straightforward.
> >>>
> >>>
> >>>>>>How would you find it if you do no deal with SIA et. al.
> >>>>>>
> >>>>>>In addition to the need cited above, please note that the
> >>>>>
> > extension
> >
> >>>>>>semantics does not change, it does not hinder any
> >>>>>
> > interoperability,
> >
> >>>>>>and it does not break any backward compatibility.  So, what if I
> >>>>>>wanted to use this extension in the CRL.  It does no harm to
other
> >>>>>>relying parties.
> >>>>>>
> >>>>>>-----Original Message-----
> >>>>>>From: owner-ietf-pkix@xxxxxxxxxxxx
> >>>>>>[mailto:owner-ietf-pkix@xxxxxxxxxxxx] On Behalf Of Denis Pinkas
> >>>>>>Sent: Wednesday, October 13, 2004 11:01 AM
> >>>>>>To: Stefan Santesson
> >>>>>>Cc: Santosh Chokhani; pkix
> >>>>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>Stefan,
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>>Denis,
> >>>>>>
> >>>>>>
> >>>>>>>I'm not sure what you mean.
> >>>>>>
> >>>>>>
> >>>>>>For the time being, I would like that you provide an example
> >>>>>
> > where,
> >
> >>>>>>when
> >>>>>>using the current extensions that are defined in RFC 3280, it
will
> >>>>>
> >>>NOT
> >>>
> >>>
> >>>>be
> >>>>
> >>>>
> >>>>>>possible to locate a CRL Issuer certificate.
> >>>>>>
> >>>>>>If you are able to provide that example, then it would justify
the
> >>>>>>need for
> >>>>>>an extension at least for one case. Then we can see what that
case
> >>>>>
> >>>is.
> >>>
> >>>
> >>>>>>I am awaiting that example.
> >>>>>>
> >>>>>>Denis
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>>I conclude that I agree with Santosh.
> >>>>>>>
> >>>>>>>The debate is still open... Feel free to express your opinion.
> >>>>>>>
> >>>>>>>Stefan Santesson
> >>>>>>>Microsoft Security Center of Excellence (SCOE)
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>-----Original Message-----
> >>>>>>>>From: Denis Pinkas [mailto:Denis.Pinkas@xxxxxxxx]
> >>>>>>>>Sent: den 13 oktober 2004 16:34
> >>>>>>>>To: Stefan Santesson
> >>>>>>>>Cc: Santosh Chokhani; pkix
> >>>>>>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>>>>>
> >>>>>>>>Stefan,
> >>>>>>>>
> >>>>>>>>You are making a conclusion without letting me the time to
> >>>>>>>
> >>>respond. I
> >>>
> >>>
> >>>>>>>>will need more time to look at the pictures (and understand
> >>>>>>>
> > them).
> >
> >>>>>>>>For the time being, I am still reluctant to accept
> >>>>>>>
> >>>>>>>"yet-another-method".
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>We already have too many.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>Santosh,
> >>>>>>>>>
> >>>>>>>>>I conclude that we are in complete and total agreement.
> >>>>>>>>>The question is how to go about this.
> >>>>>>>>
> >>>>>>>>>Could we do this amendment to RFC 3280 in its next revision?
It
> >>>>>>>>>would hopefully just be a minor change.
> >>>>>>>>
> >>>>>>>>This is exactly what I feared.
> >>>>>>>>
> >>>>>>>>We usually end-up with a "minor change" in an extension
without
> >>>>>>>>saying cleary how and when it shall/should be used.
> >>>>>>>>
> >>>>>>>>I still have in mind that:
> >>>>>>>>
> >>>>>>>>1) a certification path must first be constructed,
> >>>>>>>>2) then the revocation checking of that path must be done.
> >>>>>>>>
> >>>>>>>>This means that information about CRL issuers certificates
> >>>>>>>
> >>>locations
> >>>
> >>>
> >>>>>>>may
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>certainly be found in that chain. If not, I would like an
> >>>>>>>
> > example.
> >
> >>>>>>>>Denis
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>It would not change the definition of AIA just add that it
can
> >>>>>>>>
> > be
> >
> >>>>>>>used
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>also as CRL extension and list eventual restrictions and
> >>>>>>>
> > guidance
> >
> >>>for
> >>>
> >>>
> >>>>>>>use
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>with CRLs.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>Stefan Santesson
> >>>>>>>>>Microsoft Security Center of Excellence (SCOE)
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>>-----Original Message-----
> >>>>>>>>>>From: owner-ietf-pkix@xxxxxxxxxxxx
> >>>>>>>>>
> >>>>>>>[mailto:owner-ietf-pkix@xxxxxxxxxxxx]
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>On Behalf Of Santosh Chokhani
> >>>>>>>>>>Sent: den 13 oktober 2004 04:33
> >>>>>>>>>>To: 'pkix'
> >>>>>>>>>>Subject: RE: Signer certificate discovery for CRLs
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>Stefan:
> >>>>>>>>>>
> >>>>>>>>>>In terms of certificate discovery, your proposal for AIA in
> >>>>>>>>>
> > CRL
> >
> >>>is
> >>>
> >>>
> >>>>>>>more
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>robust.  The whole idea of self-issued key rollover
> >>>>>>>>>
> > certificates
> >
> >>>>>>>>>>and
> >>>>>>>>>
> >>>>>>>>then
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>using the new key to issue CRL is fraught with security
> >>>>>>>>>
> >>>problems.
> >>>
> >>>
> >>>>>>>>>>A secure solution would be one where the new key is
certified
> >>>>>>>>>
> > by
> >
> >>>>>>>>>>the parent
> >>>>>>>>>
> >>>>>>>CA.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>In
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>that case to obtain the new certificate, you could use AIA
in
> >>>>>>>>>
> >>>CRL.
> >>>
> >>>
> >>>>>>>>>>As to indirect CRL, your proposal is a good one.  The CRL DP
> >>>>>>>>>
> > in
> >
> >>>>>>>>>>certificate in question points to the indirect CRL.  You get
> >>>>>>>>>
> >>>that
> >>>
> >>>
> >>>>>>>>>>CRL.  The AIA
> >>>>>>>>>
> >>>>>>>in
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>CRL
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>gets you started for the indirect CRL issuer certification
> >>>>>>>>>
> > path
> >
> >>>and
> >>>
> >>>
> >>>>>>>you
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>are
> >>>>>>>>>>in business.
> >>>>>>>>>>
> >>>>>>>>>>-----Original Message-----
> >>>>>>>>>>From: owner-ietf-pkix@xxxxxxxxxxxx
> >>>>>>>>>
> >>>>>>>[mailto:owner-ietf-pkix@xxxxxxxxxxxx]
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>On
> >>>>>>>>>>Behalf Of Stefan Santesson
> >>>>>>>>>>Sent: Tuesday, October 12, 2004 7:30 PM
> >>>>>>>>>>To: David A. Cooper
> >>>>>>>>>>Cc: pkix
> >>>>>>>>>>Subject: RE: Signer certificate discovery for CRLs
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>David,
> >>>>>>>>>>
> >>>>>>>>>>Thanks for the clarifications, they make sense.
> >>>>>>>>>>I did misread your pictures.
> >>>>>>>>>>
> >>>>>>>>>>So can we conclude that for a re-keyed CA in accordance with
> >>>>>>>>>
> > RFC
> >
> >>>>>>>3280,
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>either the CRL issuer certificate itself, or the location of
> >>>>>>>>>
> > the
> >
> >>>>>>>>>>CRL issuer certificate, will be clearly identified/available
> >>>>>>>>>
> > for
> >
> >>>>>>>>>>the validating
> >>>>>>>>>
> >>>>>>>>party
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>in some cases, but not in others?
> >>>>>>>>>>
> >>>>>>>>>>Can we also conclude that there is no real discovery
solution
> >>>>>>>>>
> >>>for
> >>>
> >>>
> >>>>>>>>indirect
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>CRLs?
> >>>>>>>>>>
> >>>>>>>>>>Do you then agree then that it could be appropriate to allow
> >>>>>>>>>
> > AIA
> >
> >>>as
> >>>
> >>>
> >>>>>>>a
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>CRL
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>extension to facilitate discovery of CRL signer certificate?
> >>>>>>>>>>
> >>>>>>>>>>Stefan Santesson
> >>>>>>>>>>Microsoft Security Center of Excellence (SCOE)
> >>>>>>>>>>
> >>>>>>>>>>________________________________________
> >>>>>>>>>>From: David A. Cooper [mailto:david.cooper@xxxxxxxx]
> >>>>>>>>>>Sent: den 12 oktober 2004 21:14
> >>>>>>>>>>To: Stefan Santesson
> >>>>>>>>>>Cc: pkix
> >>>>>>>>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>>>>>>>
> >>>>>>>>>>Stefan,
> >>>>>>>>>>
> >>>>>>>>>>I believe that you are misinterpreting the figures.  They
> >>>>>>>>>
> > really
> >
> >>>do
> >>>
> >>>
> >>>>>>>>>>represent three different cases, not three different
> >>>>>>>>>
> >>>certification
> >>>
> >>>
> >>>>>>>paths
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>that have been constructed through the same PKI
architecture.
> >>>>>>>>>>
> >>>>>>>>>>In figure 1, CA 1 has generated self-issued key rollover
> >>>>>>>>>
> >>>>>>>certificates.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>The
> >>>>>>>>>>Root CA has issued a certificate to CA 1's new key, but not
> >>>>>>>>>
> > its
> >
> >>>old
> >>>
> >>>
> >>>>>>>key
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>(either the Root CA never issued a certificate to CA 1's old
> >>>>>>>>>
> > key
> >
> >>>or
> >>>
> >>>
> >>>>>>>that
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificate has expired).
> >>>>>>>>>>
> >>>>>>>>>>In figure 2, CA 2 has also generated self-issued key
rollover
> >>>>>>>>>>certificates. The Root CA has issued a certificate to CA 2's
> >>>>>>>>>
> > old
> >
> >>>>>>>>>>key, but not its
> >>>>>>>>>
> >>>>>>>new
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>key.
> >>>>>>>>>>
> >>>>>>>>>>In figure 3, when CA 3 performed key rollover, it requested
a
> >>>>>>>>>
> >>>new
> >>>
> >>>
> >>>>>>>>>>CA certificate from the Root CA.  CA 3 did not generated
> >>>>>>>>>>self-issued
> >>>>>>>>>
> >>>>>>>key
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>rollover certificates.
> >>>>>>>>>>
> >>>>>>>>>>Of course, another realistic scenario would be one in which
a
> >>>>>>>>>
> > CA
> >
> >>>>>>>>generated
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>self-issued key rollover certificates upon key rollover and
> >>>>>>>>>
> > then
> >
> >>>>>>>>>>had
> >>>>>>>>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>Root CA issue a CA certificate to its new key.  In this
case,
> >>>>>>>>>
> > as
> >
> >>>>>>>>>>you suggest, any of the certification paths from figures 1,
2,
> >>>>>>>>>
> >>>or 3
> >>>
> >>>
> >>>>>>>could be
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>constructed.
> >>>>>>>>>>
> >>>>>>>>>>As for the contents of the AIA extension, here is what I
have
> >>>>>>>>>
> >>>>>>>specified
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>in
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the "X.509 Certificate and CRL Extensions Profile for the
> >>>>>>>>>
> > Common
> >
> >>>>>>>>Policy":
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>The authorityInfoAccess extension uses URIs for two
purposes.
> >>>>>>>>>
> >>>When
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>id-ad-caIssuers access method is used, the access location
> >>>>>>>>>>specifies
> >>>>>>>>>
> >>>>>>>>where
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>certificates issued to the issuer of the certificate may be
> >>>>>>>>>
> >>>found.
> >>>
> >>>
> >>>>>>>If
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>LDAP
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>is used, the URI must include the DN of the entry containing
> >>>>>>>>>
> > the
> >
> >>>>>>>>relevant
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>certificates and specify the directory attribute in which
the
> >>>>>>>>>
> >>>>>>>>certificates
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>are located. If the directory in which the certificates are
> >>>>>>>>>
> >>>stored
> >>>
> >>>
> >>>>>>>>expects
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the "binary" option to be specified, then the attribute type
> >>>>>>>>>
> >>>must
> >>>
> >>>
> >>>>>>>>>>be followed by ";binary" in the URI. If HTTP is used, the
URI
> >>>>>>>>>
> >>>must
> >>>
> >>>
> >>>>>>>point to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>a
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>file that has an extension of ".p7c" that contains a
> >>>>>>>>>
> > certs-only
> >
> >>>CMS
> >>>
> >>>
> >>>>>>>>>>message (see RFC 2633). The CMS message should include all
> >>>>>>>>>>certificates
> >>>>>>>>>
> >>>>>>>issued
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>to
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the issuer of this certificate, but must at least contain
all
> >>>>>>>>>
> >>>>>>>>certificates
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>issued to the issuer of this certificate in which the
subject
> >>>>>>>>>>public
> >>>>>>>>>
> >>>>>>>key
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>may
> >>>>>>>>>>be used to verify the signature on this certificate. ....
For
> >>>>>>>>>
> > a
> >
> >>>>>>>>>>certificate issued by "Good CA", some examples of URIs that
> >>>>>>>>>
> > may
> >
> >>>>>>>>>>appear as the
> >>>>>>>>>
> >>>>>>>access
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>location in an authorityInfoAccess extension when the
> >>>>>>>>>
> >>>>>>>id-ad-caIssuers
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>access
> >>>>>>>>>>method is used are:
> >>>>>>>>>
>
>>>>>>>ldap://smime2.nist.gov/cn=Good%20CA,o=Test%20Certificates,c=US?cA
C
> >>>>>>
> > e
> >
> >>>r
> >>>
> >>>
> >>>>>>>>>t
> >>>>>>>>>i
> >>>>>>>>
> >>>>>>>fi
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>ca
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>te
> >>>>>>>>>>,crossCertificatePair
> >>>>>>>>>
>
>>>>>>>ldap://129.6.20.71/cn=Good%20CA,o=Test%20Certificates,c=US?cACert
i
> >>>>>>
> > f
> >
> >>>i
> >>>
> >>>
> >>>>>>>>>c
> >>>>>>>>>a
> >>>>>>>>
> >>>>>>>te
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>;b
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>in
> >>>>>>>>>>ary,crossCertificatePair;binary
> >>>>>>>>>
>
>>>>>>>http://fictitious.nist.gov/fictitiousCertsOnlyCMSdirectory/certsI
s
> >>>>>>
> > s
> >
> >>>u
> >>>
> >>>
> >>>>>>>>>e
> >>>>>>>>>d
> >>>>>>>>
> >>>>>>>To
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>Go
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>od
> >>>>>>>>>>CA.p7c
> >>>>>>>>>>For both LDAP and HTTP, the URI provides the exact location
> >>>>>>>>>
> >>>where
> >>>
> >>>
> >>>>>>>>>>information is to be located, so there is no requirement for
> >>>>>>>>>
> > the
> >
> >>>>>>>relying
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>party to try to figure out where information is located.
> >>>>>>>>>>
> >>>>>>>>>>The HTTP URI points to a certs-only CMS message that
includes
> >>>>>>>>>
> >>>all
> >>>
> >>>
> >>>>>>>>>>certificates issued to the CA identified in the issuer field
> >>>>>>>>>
> > of
> >
> >>>the
> >>>
> >>>
> >>>>>>>>>>certificate.
> >>>>>>>>>>
> >>>>>>>>>>The LDAP URI points to the cACertificate and
> >>>>>>>>>
> >>>crossCertificatePair
> >>>
> >>>
> >>>>>>>>>>attributes of the directory entry of the CA identified in
the
> >>>>>>>>>>issuer field of
> >>>>>>>>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificate.  These two attributes together hold all of the
> >>>>>>>>>
> >>>>>>>certificates
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>issued to the CA:  the cACertificate attribute holds the
CA's
> >>>>>>>>>
> >>>self-
> >>>
> >>>
> >>>>>>>>issued
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>certificates and the crossCertificatePair attribute holds
the
> >>>>>>>>>>cross-certificates issued to the CA by other CAs.
> >>>>>>>>>>
> >>>>>>>>>>Dave
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>Stefan Santesson wrote:
> >>>>>>>>>>
> >>>>>>>>>>David,
> >>>>>>>>>>
> >>>>>>>>>>Thanks for these good thoughts and very useful scenarios.
> >>>>>>>>>>
> >>>>>>>>>>I have some comments and questions on this.
> >>>>>>>>>>
> >>>>>>>>>>First of all we can conclude that in some scenarios (figure
1)
> >>>>>>>>>>where
> >>>>>>>>>
> >>>>>>>a
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>self
> >>>>>>>>>>issued certificate is inserted into the path, you are likely
> >>>>>>>>>
> > to
> >
> >>>>>>>>>>find
> >>>>>>>>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>CRL
> >>>>>>>>>>issuer cert in the path. (given that the new CA have a
common
> >>>>>>>>>
> >>>key
> >>>
> >>>
> >>>>>>>and
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificate for cert signing and CRL signing).
> >>>>>>>>>>
> >>>>>>>>>>Figure 1, 2 and 3 describe the same case. It is just
> >>>>>>>>>
> > describing
> >
> >>>>>>>>different
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>path building strategies. An application that has access
> >>>>>>>>>
> > locally
> >
> >>>to
> >>>
> >>>
> >>>>>>>all
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>chaining options may however still choose path 2 for the
certs
> >>>>>>>>>
> >>>and
> >>>
> >>>
> >>>>>>>path
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>1
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>for the CRL independent of each other (which I think figure
3
> >>>>>>>>>
> >>>tries
> >>>
> >>>
> >>>>>>>to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>describe)
> >>>>>>>>>>
> >>>>>>>>>>Another comment is the structure of AIA extensions. The use
> >>>>>>>>>
> > I'm
> >
> >>>>>>>familiar
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>with doesn't use AIA to describe a directory entry where it
is
> >>>>>>>>>
> >>>left
> >>>
> >>>
> >>>>>>>to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>the
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>validation application logic to be intelligent enough to
find
> >>>>>>>>>
> >>>>>>>>appropriate
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>certificate data from the directory. The model I'm familiar
> >>>>>>>>>
> > with
> >
> >>>is
> >>>
> >>>
> >>>>>>>when
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>AIA URL explicitly identifies the exact location of the
> >>>>>>>>>
> >>>appropriate
> >>>
> >>>
> >>>>>>>CA
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificate file, relieving the validation software from
> >>>>>>>>>
> > complex
> >
> >>>>>>>>>>information queries. If just location of explicit
certificate
> >>>>>>>>>
> >>>files
> >>>
> >>>
> >>>>>>>>>>are
> >>>>>>>>>
> >>>>>>>identified
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>through AIA, the presence of an AIA may not help finding the
> >>>>>>>>>
> > CRL
> >
> >>>>>>>signer
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>cert
> >>>>>>>>>>if this is different from the CA certificate. This is also
the
> >>>>>>>>>
> >>>>>>>problem
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>with
> >>>>>>>>>>Denis proposal.
> >>>>>>>>>>
> >>>>>>>>>>I think we share the basic conclusion that the ability to
> >>>>>>>>>
> > locate
> >
> >>>>>>>>>>the
> >>>>>>>>>
> >>>>>>>CRL
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>signer certificate directly through the CRL could be very
> >>>>>>>>>
> >>>useful.
> >>>
> >>>
> >>>>>>>>>>At
> >>>>>>>>>
> >>>>>>>>least
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>in the case of indirect CRL but it could also be proven very
> >>>>>>>>>
> >>>useful
> >>>
> >>>
> >>>>>>>in
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>CA
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>re-keying scenarios.
> >>>>>>>>>>
> >>>>>>>>>>The easiest solution would probably be to allow AIA to be
used
> >>>>>>>>>
> >>>in
> >>>
> >>>
> >>>>>>>its
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>current shape and structure as a CRL extension (MUST NOT be
> >>>>>>>>>
> >>>>>>>critical).
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>It
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>would present a very clear and uncomplicated logic to
> >>>>>>>>>
> >>>certificate
> >>>
> >>>
> >>>>>>>>>>validating applications in many cases.
> >>>>>>>>>>
> >>>>>>>>>>Stefan Santesson
> >>>>>>>>>>Microsoft Security Center of Excellence (SCOE)
> >>>>>>>>>>
> >>>>>>>>>>________________________________________
> >>>>>>>>>>From: David A. Cooper [mailto:david.cooper@xxxxxxxx]
> >>>>>>>>>>Sent: den 7 oktober 2004 18:35
> >>>>>>>>>>To: Stefan Santesson
> >>>>>>>>>>Cc: pkix
> >>>>>>>>>>Subject: Re: Signer certificate discovery for CRLs
> >>>>>>>>>>
> >>>>>>>>>>Stefan,
> >>>>>>>>>>
> >>>>>>>>>>I think what you are proposing is a good idea.  In most
cases,
> >>>>>>>>>
> >>>path
> >>>
> >>>
> >>>>>>>>>>discovery algorithms assume that both the trust anchor (or
> >>>>>>>>>
> > trust
> >
> >>>>>>>>anchors)
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>and the end entity certificate are provided as input.  In
this
> >>>>>>>>>>case,
> >>>>>>>>>
> >>>>>>>one
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>may
> >>>>>>>>>>need to construct a certification path without a priori
access
> >>>>>>>>>
> >>>to
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>end
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>entity certificate (the one with the subject public key
> >>>>>>>>>
> >>>>>>>corresponding to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>CRL signing key).  Including an AIA extension (or some other
> >>>>>>>>>
> >>>>>>>pointer) in
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>CRL would provide the relying party with a simple way to
> >>>>>>>>>
> > obtain
> >
> >>>the
> >>>
> >>>
> >>>>>>>end
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>entity certificate for the CRL signing key's certification
> >>>>>>>>>
> > path.
> >
> >>>On
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>other hand, I believe that a relying party should be able to
> >>>>>>>>>
> >>>>>>>construct
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>the
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>certification path even without an AIA extension in the CRL,
> >>>>>>>>>
> > so
> >
> >>>>>>>>>>long
> >>>>>>>>>
> >>>>>>>as
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>it
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>is not an indirect CRL.  Attached is a drawing of the three
> >>>>>>>>>
> >>>basic
> >>>
> >>>
> >>>>>>>>>>scenarios that I expect a relying party may encounter:
> >>>>>>>>>>
> >>>>>>>>>>In each of these scenarios, the CA has performed key
rollover
> >>>>>>>>>
> >>>and
> >>>
> >>>
> >>>>>>>>>>is
> >>>>>>>>>
> >>>>>>>>only
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>signing CRLs with its new key.  The diagrams would look
> >>>>>>>>>
> > similar,
> >
> >>>>>>>>however,
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>if
> >>>>>>>>>>the CA simply choose to use different keys to sign
> >>>>>>>>>
> > certificates
> >
> >>>and
> >>>
> >>>
> >>>>>>>CRLs
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>for
> >>>>>>>>>>some other reason.
> >>>>>>>>>>
> >>>>>>>>>>If the PKI architecture resembled figure 1, then the
> >>>>>>>>>
> >>>certification
> >>>
> >>>
> >>>>>>>path
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>for
> >>>>>>>>>>the CRL signing key would just be a subset of the
> >>>>>>>>>
> > certification
> >
> >>>>>>>>>>path
> >>>>>>>>>
> >>>>>>>for
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>EE certificate, so no addition path discovery would be
needed.
> >>>>>>>>>>
> >>>>>>>>>>If the PKI architecture resembled figure 1, then it would be
> >>>>>>>>>
> >>>>>>>necessary
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>to
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>obtain the new-signed-with-old self-issued certificate.  In
> >>>>>>>>>>building
> >>>>>>>>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certification path to the EE certificate, however, the
relying
> >>>>>>>>>>party
> >>>>>>>>>
> >>>>>>>>will
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>obtain the certificates pointed to by the AIA extension in
the
> >>>>>>>>>
> >>>EE
> >>>
> >>>
> >>>>>>>>>>certificate.  This AIA extension will point to a location
> >>>>>>>>>>containing
> >>>>>>>>>
> >>>>>>>all
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificates issued to CA 2, which would include both the
> >>>>>>>>>
> >>>>>>>certificate
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>issued
> >>>>>>>>>>by the Root to CA 2 and CA 2's self-issued certificate.  So,
> >>>>>>>>>
> >>>even
> >>>
> >>>
> >>>>>>>though
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>self-issued certificate would not be part of the
certification
> >>>>>>>>>
> >>>path
> >>>
> >>>
> >>>>>>>to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>the
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>EE certificate, it would be downloaded by the relying party
> >>>>>>>>>
> >>>during
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>construction of that certification path.  (Yes, there are
> >>>>>>>>>
> >>>circular
> >>>
> >>>
> >>>>>>>>>>dependency issues in figure 2, but that is another issue.)
> >>>>>>>>>>
> >>>>>>>>>>A similar situation would happen if the PKI architecture
> >>>>>>>>>
> >>>resembled
> >>>
> >>>
> >>>>>>>>figure
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>3.  The AIA extension in the EE certificate would point to a
> >>>>>>>>>
> >>>>>>>location
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>containing certificates issued to CA 3.  When the relying
> >>>>>>>>>
> > party
> >
> >>>>>>>>downloaded
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>these certificates, it would obtain both of the certificates
> >>>>>>>>>
> >>>issued
> >>>
> >>>
> >>>>>>>by
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>the
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>Root to CA 3 and so again would have the certificate needed
to
> >>>>>>>>>
> >>>>>>>validate
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>the
> >>>>>>>>>>CRL signing key.
> >>>>>>>>>>
> >>>>>>>>>>In the case of an indirect CRL, things may not work as well.
> >>>>>>>>>
> > If
> >
> >>>>>>>>indirect
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>CRLs were used, and the PKI architecture resembled figures 2
> >>>>>>>>>
> > or
> >
> >>>3
> >>>
> >>>
> >>>>>>>>>>(replacing "New Key" with a different CA), then the set of
> >>>>>>>>>>certificates pointed
> >>>>>>>>>
> >>>>>>>to
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>by
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the AIA extension in the EE certificate would not include
the
> >>>>>>>>>
> >>>>>>>>certificate
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>of
> >>>>>>>>>>the CRL signer.  One could find this certificate by building
> >>>>>>>>>
> > in
> >
> >>>the
> >>>
> >>>
> >>>>>>>>>>reverse direction and using the SIA extension, but that may
> >>>>>>>>>
> > not
> >
> >>>be
> >>>
> >>>
> >>>>>>>>>>the most convenient solution.
> >>>>>>>>>>
> >>>>>>>>>>So, when indirect CRLs are being used, it seems that it
would
> >>>>>>>>>
> > be
> >
> >>>>>>>very
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>useful
> >>>>>>>>>>to have a pointer in the CRL to the CRL signing certificate.
> >>>>>>>>>
> >>>When
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>CRL
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>is not indirect, the need for this pointer does not seem to
be
> >>>>>>>>>
> >>>as
> >>>
> >>>
> >>>>>>>clear,
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>but
> >>>>>>>>>>I can't see any harm in including it.
> >>>>>>>>>>
> >>>>>>>>>>Dave
> >>>>>>>>>>
> >>>>>>>>>>Stefan Santesson wrote:
> >>>>>>>>>>All,
> >>>>>>>>>>
> >>>>>>>>>>I'm interested in the opinion from members on this list
about
> >>>>>>>>>
> >>>>>>>discovery
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>of
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>CRL signer's certificate in non directory centric
> >>>>>>>>>
> > environments.
> >
> >>>>>>>>>>The problem is the following.
> >>>>>>>>>>
> >>>>>>>>>>The relying party (RP) needs to check validity of a
> >>>>>>>>>
> > certificate
> >
> >>>and
> >>>
> >>>
> >>>>>>>>finds
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>a
> >>>>>>>>>>CDP extension with a URL to the CRL. The RP retrieves this
CRL
> >>>>>>>>>>which
> >>>>>>>>>
> >>>>>>>in
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>this
> >>>>>>>>>>particular case is either signed by another key of the CA
> >>>>>>>>>
> >>>(re-keyed
> >>>
> >>>
> >>>>>>>CA)
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>or
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>another entity (indirect CRL).
> >>>>>>>>>>
> >>>>>>>>>>In this case the relying party needs to obtain the
certificate
> >>>>>>>>>
> >>>of
> >>>
> >>>
> >>>>>>>the
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>CRL
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>signer which may NOT be part of the original chain. In a
> >>>>>>>>>
> >>>directory
> >>>
> >>>
> >>>>>>>>centric
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>solution this is retrieved from the directory, but what if
> >>>>>>>>>
> > such
> >
> >>>>>>>>directory
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>is
> >>>>>>>>>>not available or accessible.
> >>>>>>>>>>
> >>>>>>>>>>The RP have thus no hint where to find the CRL issuers
> >>>>>>>>>
> >>>certificate
> >>>
> >>>
> >>>>>>>>unless
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the RP already have possession of it by some other means.
> >>>>>>>>>>
> >>>>>>>>>>Is seems that CRLs would need an AIA extension with the
option
> >>>>>>>>>
> >>>to
> >>>
> >>>
> >>>>>>>point
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>to
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>the location of the signers certificate in the same manner
as
> >>>>>>>>>
> > is
> >
> >>>>>>>>possible
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>>for certificates.
> >>>>>>>>>>
> >>>>>>>>>>Maybe AIA should be defined as both cert and CRL extension
and
> >>>>>>>>>
> >>>not
> >>>
> >>>
> >>>>>>>only
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>>certificate extension as today.
> >>>>>>>>>>
> >>>>>>>>>>Thoughts and comments?
> >>>>>>>>>>
> >>>>>>>>>>Stefan Santesson
> >>>>>>>>>>Microsoft Security Center of Excellence (SCOE)
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>
> >>>
> >
> >
>
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