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    SubjectRe: [RFD] linux-firmware key arrangement for firmware signing
    Date
    Seth Forshee <seth.forshee@canonical.com> wrote:

    > > This begs the question on how we'd manage keys for firmware signing on
    > > linux-firmare. Since the keys are x509 keys we need a CA. Based on some
    > > initial discussions it would seem we'd need the Linux Foundation to create
    > > a key, this would be embedded in the kernel and that key would be used to
    > > sign Kyle's key. Kyle would in turn use his key for signing
    > > linux-firmware files. David, Kyle, did I summarize this correctly ?
    >
    > I raised the question of key revocation when we discussed this on irc,
    > but it wasn't answered to my satisfaction. If a key signed by the
    > kernel-embedded key is compromised, how can that key be revoked so that
    > it is no longer trusted?
    >
    > Someone mentioned UEFI blacklists, which I don't know much about, but
    > not all systems have UEFI. The only reliable option that comes to mind
    > for me is an in-kernel blacklist of keys which should no longer be
    > trusted.

    Key revocation is generally an unpleasant problem. How do you inform a system
    that a key of any sort is revoked? With PGP, for instance, you might be able
    to connect to the net and consult a server.

    UEFI has a blacklist that can theoretically be used to prevent both usage of a
    key and usage of a particular object. As I understand it, the blacklist in
    UEFI is just a table of SHA256 hashes.

    Relying on UEFI presents three problems, though: (1) the system admin has to
    manually, as far as I'm aware, inform the BIOS; (2) the UEFI storage is
    limited; and (3) not all systems have UEFI.

    What you do on a non-UEFI system, I'm not sure. If the kernel isn't verified
    by the loader or the system firmware then you don't have a 'fully' secure
    system anyway and the blacklist may be of questionable value.

    David


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