Hi All,
On Tue, 15 Nov 2005, silverhairbp wrote:
David Bannon wrote:
Folks, I would like to ask for some advice here. We have a problem and
below is our plan to solve it. I'd be very grateful if you could have a
look at it and let me know if you see anything thats going to bite us
expectantly.
The problem
-----------
We use OpenCA 0.9.2 and it was setup some 12 months ago using default
settings. Our CA Certificate was originally issued without the necessary
parameter of keyUsage being 'critical'.
The solution
------------
Revoke all 220 certificates, revoke the CA Certificate, issue a new CA
certificate (using existing key) and issue new certificates to users.
I think you should not do that. If the only thing you want to change is
technical parameters in your root cert, but otherwise use the same
keypair, you essentially maintain the trust based on the the signatures
made with your original signing key. In other words, you do not need to
revoke anything, instead you simply reissue your root cert with the same
DN, serial, keypair and validity dates and changed technical parameters
(e.g., fixing the keyUsage, changing the signature algorithm etc). In this
way, signatures made with the old or new root certs will validate against
either of them. The already issued certificates will not be effected.
Besides, there is no point in revoking a self-signed certificate anyway,
in case you want to terminate the trust associated with the signatures
made with a CA's signing key before the expiration of the root cert
(emergency key changeover), you revoke all issued certificates (except the
root), publish a last valid CRL, destroy all copies of the CA signing key,
and start anew with a fresh PKI.
If you only want to terminate the usage of a CA's signing key -without
disruption of the trust associated with its signatures- (routine key
changeover), you can harmonize various validity dates and CRL issuance
frequency such that you can keep your usual operating procedures (issuing
CRLs as usual) and let all certs (issued and root) expire. Before that
happens, you already start your fresh PKI in parrallel with some useful
overlap time.
Good Luck,
Cheers
Szabolcs
P.S.: as a sidenote, if the keypair of sub-CA is actually compromised in a
multilevel hierarchy (as opposed to having some flags misconfigured), I
would definitely *revoke* the sub-CA's root certificate for good, not only
suspend it. The keypair is the root of your trust - if it's compromised,
your pki (under that sub-CA's level) is over.
The Plan
------------
We have established that we can generate a new CA Certificate and OpenCA
(0.9.2) is quite happy. So this is what we'll do, steps 1 - 3 (below)
must be done before implementation date.
1) Encourage all end users and RA Operators to lodge new requests for
new certificates.
2) Ordinary users must meet (again) with RA Operators to show photo ID.
RAO must authorise new applications in normal manner.
3) CA Operators and CA Manager will phone RAOs to explicitly confirm
details of their own personal applications, in normal manner.
------ Implementation Day --------
4) On the CA machine, move the existing CA Certificate files
(from /var/crypto/cacerts) out of the way. Their details will remain in
the database. Start openCA, make a new request for a self signed
certificate and then Generate it. (General->Initialization->Request
Setup, Certificate Setup).
5) On RA, revoke all user certificates and process to CA.
6) On RA, revoke the old CA Certificate and process to CA.
7) Commence issuing the backlog of certificate requests currently
pending, in the normal manner.
Although we will aim for completing this process in one day, I doubt we
will be able to do so.
--------------------
I'll be very grateful for any comments you care to make.
David
Rather than revoking the original CA certificate, have you considerd
suspending it to see if there are any user that have not installed their new
certificates? It would be easy to roll back the old root cert and convert
that last users, repead the suspend root process until all users are
converted. That way you can motivate slow converters to get new certificates
while minimizing their down time.
As a suggestion, when deploying the new hierarchy, manage the validity period
closely so taht you can migrate to a new root without a lot of hassle. There
are papers on the technique available.
Bill
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