linux-kernel - Re: [PATCH v1 2/2] IMA: Call workqueue functions to measure queued keys

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Date:   Tue, 10 Dec 2019 20:40:28 -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,
        mathew.j.martineau@...ux.intel.com, matthewgarrett@...gle.com,
        sashal@...nel.org, jamorris@...ux.microsoft.com,
        linux-kernel@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH v1 2/2] IMA: Call workqueue functions to measure queued
 keys

On Thu, 2019-12-05 at 17:29 -0800, Lakshmi Ramasubramanian wrote:
> Measuring keys requires a custom IMA policy to be loaded.
> Keys should be queued for measurement if a custom IMA policy
> is not yet loaded. Keys queued for measurement, if any, should be
> processed when a custom IMA policy is loaded.
> 
> This patch updates the IMA hook function ima_post_key_create_or_update()
> to queue the key if a custom IMA policy has not yet been loaded.
> And, ima_update_policy() function, which is called when
> a custom IMA policy is loaded, is updated to process queued keys.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  security/integrity/ima/ima_asymmetric_keys.c | 9 +++++++++
>  security/integrity/ima/ima_policy.c          | 6 ++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
> index fbdbe9c261cb..510b29d17a7b 100644
> --- a/security/integrity/ima/ima_asymmetric_keys.c
> +++ b/security/integrity/ima/ima_asymmetric_keys.c
> @@ -155,6 +155,8 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>  				   const void *payload, size_t payload_len,
>  				   unsigned long flags, bool create)
>  {
> +	bool key_queued = false;
> +
>  	/* Only asymmetric keys are handled by this hook. */
>  	if (key->type != &key_type_asymmetric)
>  		return;
> @@ -162,6 +164,13 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
>  	if (!payload || (payload_len == 0))
>  		return;
>  
> +	if (!ima_process_keys_for_measurement)
> +		key_queued = ima_queue_key_for_measurement(keyring, payload,
> +							   payload_len);
> +
> +	if (key_queued)
> +		return;
> +
>  	/*
>  	 * keyring->description points to the name of the keyring
>  	 * (such as ".builtin_trusted_keys", ".ima", etc.) to
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 73030a69d546..4dc8fb9957ac 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -808,6 +808,12 @@ void ima_update_policy(void)
>  		kfree(arch_policy_entry);
>  	}
>  	ima_update_policy_flag();
> +
> +	/*
> +	 * Custom IMA policies have been setup.

^has been loaded.

> +	 * Process key(s) queued up for measurement now.

The function name ima_process_queued_keys_for_measurement() provides a
clear indication that the keys will be processed.  We don't comment
the obvious.  Please remove the above comment.

Mimi

> +	 */
> +	ima_process_queued_keys_for_measurement();
>  }
>  
>  /* Keep the enumeration in sync with the policy_tokens! */