linux-kernel - Re: [PATCH v9 5/6] IMA: Add support to limit measuring keys

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Date:   Tue, 03 Dec 2019 07:25:45 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        matthewgarrett@...gle.com, sashal@...nel.org,
        jamorris@...ux.microsoft.com, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH v9 5/6] IMA: Add support to limit measuring keys

Hi Lakshmi,

On Tue, 2019-11-26 at 17:56 -0800, Lakshmi Ramasubramanian wrote:
> Limit measuring keys to those keys being loaded onto a given set of
> keyrings only.
> 
> This patch defines a new IMA policy option namely "keyrings=" that
> can be used to specify a set of keyrings. If this option is specified
> in the policy for "measure func=KEY_CHECK" then only the keys
> loaded onto a keyring given in the "keyrings=" option are measured.
> 
> Added a new parameter namely "keyring" (name of the keyring) to
> process_buffer_measurement(). The keyring name is passed to
> ima_get_action() to determine the required action.
> ima_match_rules() is updated to check keyring in the policy, if
> specified, for KEY_CHECK function.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>

A keyring can be created by any user with any keyring name, other than
 ones dot prefixed, which are limited to the trusted builtin keyrings.
 With a policy of "func=KEY_CHECK template=ima-buf keyrings=foo", for
example, keys loaded onto any keyring named "foo" will be measured.
 For files, the IMA policy may be constrained to a particular uid/gid.
 An additional method of identifying or constraining keyring names
needs to be defined.

Mimi