Re: [Trans] Precertificate format

Rob Stradling <rob.stradling@comodo.com> Tue, 16 September 2014 10:25 UTC

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Date: Tue, 16 Sep 2014 11:25:53 +0100
From: Rob Stradling <rob.stradling@comodo.com>
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To: Erwann Abalea <eabalea@gmail.com>
References: <540DFA75.2040000@gmail.com><540E0E90.1070208@bbn.com><540E28FD.7050809@gmail.com><540ECD3A.4040704@primekey.se><540F4598.5010505@bbn.com><CABrd9SSg5=wuierLoqAU00pMHxgGx+=ai5mHv4u5t6zm43yDWg@mail.gmail.com><5410779A.20209@bbn.com><CABrd9STnjqDBF4-5ABJ86M_d0bwRyjRNjRW6Hnj9UpeYC7Xz9A@mail.gmail.com><5411BDE4.1060508@bbn.com><CABrd9STAHzg_KJi=nA7hsvz+k0SMS+bg6c3hcBtUwfOUm=hqTQ@mail.gmail.com><5411E6B4.5040401@bbn.com><02c365fdc2b8478fb78f310382ae0bb7@EX2.corp.digicert.com><CA+i=0E4bKzn6DB73H7p8k+kDyrku54WhU5ZFcA2g5zY69Kn-Hg@mail.gmail.com><5416B216.6050904@comodo.com><CA+i=0E6svuD8RGNWqHaywtGm17JWz7Mw005OhRbnb+hPDrdrSw@mail.gmail.com> <5416EFD8.1040801@comodo.com>
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Cc: "trans@ietf.org" <trans@ietf.org>, Jeremy Rowley <jeremy.rowley@digicert.com>
Subject: Re: [Trans] Precertificate format
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On 15/09/14 14:55, Rob Stradling wrote:
> On 15/09/14 14:27, Erwann Abalea wrote:
<snip>
>> AKI being a variable extension, how could the log know which one of
>> {issuerName+serialNumber}, {keyIdentifier},
>> {issuerName+serialNumber+keyIdentifier} content will be found in the
>> final certificate?
>
> Funny you should mention this.  Right now I'm working on SCT
> verification code for OpenSSL with Steve Henson and Emilia.  Just a few
> minutes ago Steve asked the very same question you've just asked here.
>
> So I just looked at the language in RFC6962 Section 3.2.  I think "the
> TBSCertificate also has its Authority Key Identifier changed to match
> the final issuer" is sufficiently vague that we need to file an erratum
> to RFC6962 to specify exactly how to deal with the optionality of the
> various AKI components.
>
> I also just looked at the certificate-transparency.org code for
> inspiration, but it seems to be doing completely the wrong thing!  It's
> copying the final cert issuer's AKI rather than SKI.  :-(

Sorry, ignore that.  Looks like the certificate-transparency.org code is 
actually copying the Issuer Name and AKI from the Precertificate Signing 
Certificate.  That's correct.

Nonetheless, I still think RFC6962 needs an erratum to deal with the 
optionality of the various AKI components.

>> If it's the log signer's job, then in the PreCert signing certificate
>> situation, there's no non-conformance to RFC5280 (regarding to
>> issuerName+serialNumber uniqueness).
>
> Correct.  The serialNumber is identical, but the issuerName is different.

-- 
Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online