[cabfpub] [EXTERNAL]Re: Ballot 199 - Require commonName in Root and Intermediate Certificates

Ryan Sleevi sleevi at google.com
Wed Apr 26 17:53:21 UTC 2017

On Wed, Apr 26, 2017 at 1:25 PM, Bruce Morton via Public <
public at cabforum.org> wrote:

> Hi Gerv,
> I'm also confused with the proposal, so wanted to discuss our methodology.
> From our point of view, we create a subordinate certification authority
> and give this CA a distinguished name. We use the CN to give the CA a
> unique identifier, so that the common name will not be mixed up with any
> other subordinate CAs.
> Then we need to give the subordinate CA trust, so we issue it a
> subordinate CA certificate from a root CA. The subordinate CA certificate
> will have the same distinguished name.

All fantastic so far...

> If for some reason we need to issue the subordinate CA another CA
> certificate (e.g., the original certificate expires), then the new
> certificate will have the identical subject name as the original.

Could you explain the use cases here? This introduces a significant amount
of complexity (ergo: risk) into the Web PKI. The situation you described -
the original expiring - should not require the reissuance with the same
name, because no leaf certificate should have exceeded the validity window
of the intermediate. As you approach the intermediates expiration,
minimally, you could/should have begun transitioning off of it.

What other use cases exist to imbue this? I can certainly understand
situations like "add additional extensions", but there again, a new name
(for new certificates) could imbue the new powers and capabilities. The
only reason to reissue the existing certificate is to retroactively imbue
the extant certificates with new capabilities, and I'm curious when that
situation is necessary.

Otherwise, it should hopefully seem uncontroversial to identify a new
common name for this new certificate with new capabilities (whether the
validity period or the extension-based capability). But I'm interested to
learn why CAs do so, and if there's any particular need/advantage over
simply issuing a new intermediate.
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