Re: [PATCH v3 09/10] certs: Allow root user to append signed hashes to the blacklist keyring

From: Mickaël Salaün
Date: Wed Jan 20 2021 - 07:08:11 EST

On 20/01/2021 06:23, Jarkko Sakkinen wrote:
> On Thu, Jan 14, 2021 at 04:19:08PM +0100, Mickaël Salaün wrote:
>> From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
>> Add a kernel option SYSTEM_BLACKLIST_AUTH_UPDATE to enable the root user
>> to dynamically add new keys to the blacklist keyring. This enables to
>> invalidate new certificates, either from being loaded in a keyring, or
>> from being trusted in a PKCS#7 certificate chain. This also enables to
>> add new file hashes to be denied by the integrity infrastructure.
>> Being able to untrust a certificate which could have normaly been
>> trusted is a sensitive operation. This is why adding new hashes to the
>> blacklist keyring is only allowed when these hashes are signed and
>> vouched by the builtin trusted keyring. A blacklist hash is stored as a
>> key description. The PKCS#7 signature of this description must be
>> provided as the key payload.
>> Marking a certificate as untrusted should be enforced while the system
>> is running. It is then forbiden to remove such blacklist keys.
>> Update blacklist keyring and blacklist key access rights:
>> * allows the root user to search for a specific blacklisted hash, which
>> make sense because the descriptions are already viewable;
>> * forbids key update;
>> * restricts kernel rights on the blacklist keyring to align with the
>> root user rights.
>> See the help in tools/certs/ provided by a
>> following commit.
> Please re-order patches in a way that is
> available before this. That way we get rid of this useless remark.


>> Cc: David Howells <dhowells@xxxxxxxxxx>
>> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
>> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
> /Jarkko