[cabfpub] RFC5280

Erwann Abalea Erwann.Abalea at docusign.com
Thu Feb 25 10:44:55 UTC 2016


Le 24 févr. 2016 à 19:56, Jeremy Rowley <jeremy.rowley at digicert.com<mailto:jeremy.rowley at digicert.com>> a écrit :

I’ve been playing around with Peter Bowen’s certlint (an excellent tool) and, looking at the cert universe as a whole, there are some noticeable issues with the BRs and RFC 5280 that I though merited a public CAB Forum discussion.  Some of this is likely me not knowing the entire history of 5280, so I appreciated any explanation. If there’s exceptions we would like to make to RFC5280, we should probably also push a bis with IETF at the same time.

Here’s what I’m noticing are common issues:
1)      Org names, common names,  and address fields are limited to 64 characters. Very few international companies can comply with this restriction. It’s even worse if you are converting an IDN to a printable string.  I don’t think any browsers limit this to 64 characters?  Is there a strong objection to permitting longer strings in these fields?
2)      keyAgreement isn’t specifically prohibited in the BRs or 5280. However, keyAgreement should no longer be used in ECC certs because of security issues as explained by Ryan Sleevi in previous emails . We should update the BRs to prohibit keyAgreement.

keyAgreement isn’t forbidden in 5280 because (EC)DH certificates can exist, and this would be the only valid key usage.
Referring to BR scope, which is TLS certificates, the EC key included in a certificate isn’t used to establish the PreMesterSecret, but only to sign an ephemeral (or not) DH key that itself will be used to establish this PMS. So declaring keyAgreement in the certificate is useless.

3)      Years ago, we discussed that 2047 bit certs were equivalent to 2048 bit certs (although the discussion may have occurred solely on the Mozilla mailing list).  We should codify this exception.
4)      Why is teletext string not permissible on a lot of these fields? I also don’t understand the weird requirement to use printablestring over UTRF8 for some fields. Specifically, requiring a printable string for subject:serialNumber could cause issues with the EV Guidelines if a country uses an IDN as part of their registration number.

serialNumber, in X.520, is defined as being a PrintableString only, not a choice of different string types as others fields.
That’s the same situation with domainComponent (IA5String only), defined by LDAP RFCs, and countryName (defined in X.520) which is also limited to PrintableString and is exactly 2 characters long.
You can’t change the definition of an attribute.

Erwann Abalea

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