Re: [websec] #58: Should we pin only SPKI, or also names

[Trevor Perrin <[e-mail]>]

On Wed, Aug 7, 2013 at 2:55 AM, Gervase Markham <[e-mail]> wrote:
> On 07/08/13 10:45, Trevor Perrin wrote:
>> Presumably the browser would have a table mapping names to key lists,
>> and would evaluate a site's cert chain by checking for an intersection
>> with all relevant keys in the pin (direct or indirect).
>
> Yes; this would need to be metadata associated with each cert in the
> root store. It would need to be added when roots were added.

I was imagining a table which is indexed by CA names, and which maps a
CA name to a corresponding list of key hashes.  These hashes might
correspond to certs in the root store or they might not (e.g., they
might correspond to intermediates).

Only CAs which had "opted-in" and provided the requisite info to
browsers would be in the table.


> What happens if a CA requests a change to this mapping? This might
> violate the expectations of some users as to which keys they were pinning.

When a pinned CA wants to introduce a new root, it would need to
update the mapping and wait for the update to propagate before using
the new root to sign certs.

When a pinned CA wants to remove a revoked or expired root from the
mapping, it should be able to do so without problems since browsers
would not construct cert paths that require this root.

Anyways, if users want to be pinned to a specific key, they should pin
to that key directly.  If they're pinned to a name, they're trusting
the CA and browser vendor to keep the mapping updated in a sensible
way.


Trevor