On 05/11/2012 18:28, Michael StJohns wrote:
At 09:17 AM 11/5/2012, Vincent Ryan wrote:
Thanks for your suggestion Mike. I quite like that approach but I'm concerned
that existing tools and
browsers do not support this new type of PKCS12 safe bag.
I went back and took a look at the PKCS12 standard. The ASN1 defining the list of bag
types ends with an elipsis "..." which indicates extensibility.
I just took a look at the code for BouncyCastle - it just prints a "file has extra
data" and continues.
I'm digging into the Openssl code - it appears to do the right thing with the
ASN1 parsing - still tracking back to the app code.
I know these tools can successfully parse arbitrary PKCS12 elements - I
have already done some testing using the PKCS12 Secret Bag to store
symmetric keys.
My point is that the parsers will just ignore unrecognized elements.
One of the goals of this feature is to migrate from JKS to a format
that is more interoperable with commonly used PKI-aware components.
If we could overcome the issue with using extendedKeyUsage as a bag attribute
then I think that the
current proposal using cert bag would be a more interoperable solution.
I talked to the author of RFC5914 and proposed both your original approach and
my suggestion. If anything I think he was more opposed to using
ExtendedKeyUsage in this approach than I am.
If you want to do this, you need to find something that's typed as an ATTRIBUTE, and
that's got an unambiguous meaning of "this cert is considered to be a trust
anchor". I can't find an OID that means this and I've looked.
So that leaves defining a new attribute that denotes a cert's level
of trust. I guess it could also be used to denote a lack of trust or a
prohibition of trust.
On 4 Nov 2012, at 21:31, Michael StJohns wrote:
At 11:14 PM 11/1/2012, Michael StJohns wrote:
The appeal of re-purposing the extendedKeyUsage attribute is that it is already
well known as a certificate extension. And in addition, it can be used by
keystore owners to limit a cert's trust level to quite specific purposes.
This is one of those things where you have to read the fine print. AnyKeyUsage
means exactly that. It means the key pair associated with this certificate can
be used to sign pretty much anything and still be within policy. It says
nothing about the trust status of the associated certificate or the public key
within the certificate.
What you want is an attribute that says "this certificate is a representation of a
root of trust" and that attribute type doesn't exist AFAIK.
I sent a note off to the PKIX mailing list to see if anyone has already defined
such a beast. I should have an answer shortly. If there isn't one, you can
either assign one from Sun/Oracle/Java's arc (and write a 1 pager somewhere
that describes the format) or better - write an Informational ID that defines
the format and submit it for publication.
Mike
I haven't heard back from the PKIX group, but take a look at RFC5914 - section
3 - Trust Anchor List.
Instead of adding an attribute in a CertBag with a type of
ExtendedKeyUsage:AnyKey, instead, use the type and values in this section to
create a TrustAnchorBag - use TrustAnchorList as the format and
id-ct-trustAnchorList as the OID for the bag type.
Doing it this way allows you to avoid overloading the CertBag / PrivateKey
pairing model, and should be an acceptable way of including trust anchors in a
P12 file.
I'm going to try and grab the author(s) of 5914 and see what they think.
Later, Mike
