linux-kernel - Re: [PATCH v1 5/6] KEYS: measure queued keys

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Date:   Wed, 23 Oct 2019 09:23:10 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        dhowells@...hat.com, casey@...aufler-ca.com, sashal@...nel.org,
        jamorris@...ux.microsoft.com,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH v1 5/6] KEYS: measure queued keys

On Tue, 2019-10-22 at 17:18 -0700, Lakshmi Ramasubramanian wrote:
> Call process_buffer_measurement to measure keys that
> are added and updated in the system.

This patch description doesn't describe what the patch actually does
(eg. it not only calls process_buffer_measurement, but defines the IMA
hook itself.)

The ordering of this patch set is awkward.  It should first introduce
a generic method for measuring keys based on the keyring.  Then add
the additional support needed for the specific builtin_trusted_keys
keyring usecase.

> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  security/integrity/ima/ima_main.c  | 23 +++++++++++++++++++++
>  security/integrity/ima/ima_queue.c | 32 ++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 8e965d18fb21..7c2afb954f19 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -678,6 +678,29 @@ void ima_kexec_cmdline(const void *buf, int size)
>  	}
>  }
>  
> +/*
> + * ima_post_key_create_or_update
> + * @keyring points to the keyring to which the key belongs
> + * @key points to the key being created or updated
> + * @cred cred structure
> + * @flags flags passed to key_create_or_update function
> + * @create flag to indicate whether the key was created or updated
> + *
> + * IMA hook called when a new key is created or updated.
> + *
> + * On success return 0.
> + * Return appropriate error code on error
> + */
> +int ima_post_key_create_or_update(struct key *keyring, struct key *key,
> +				  const struct cred *cred,
> +				  unsigned long flags, bool create)
> +{
> +	if (key->type != &key_type_asymmetric)
> +		return 0;
> +
> +	return ima_measure_key(keyring, key);
> +}
> +

Here is the new IMA hook, not "[PATCH v1 3/6] KEYS: ima hook to
measure builtin_trusted_keys".  The new hook should call
process_buffer_measurement() directly.  A subsequent patch, based on
the keyring, would determine if it needs to be queued.

Mimi


>  static int __init init_ima(void)
>  {
>  	int error;
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index a262e289615b..0da11a292f99 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -322,7 +322,12 @@ static struct ima_trusted_key_entry *ima_alloc_trusted_queue_entry(
>  int ima_measure_key(struct key *keyring, struct key *key)
>  {
>  	int rc = 0;
> +	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> +	struct ima_template_desc *template_desc = ima_template_desc_current();
> +	int action;
>  	struct ima_trusted_key_entry *entry = NULL;
> +	const struct public_key *pk;
> +	u32 secid;
>  	enum ima_hooks func;
>  	bool queued = false;
>  
> @@ -344,16 +349,43 @@ int ima_measure_key(struct key *keyring, struct key *key)
>  
>  	mutex_unlock(&ima_trusted_keys_mutex);
>  
> +	if ((rc == 0) && !queued) {
> +		security_task_getsecid(current, &secid);
> +		action = ima_get_action(NULL, current_cred(), secid, 0,
> +					func, &pcr, &template_desc);
> +		if (action & IMA_MEASURE) {
> +			pk = key->payload.data[asym_crypto];
> +			process_buffer_measurement(pk->key, pk->keylen,
> +						   key->description,
> +						   pcr, template_desc);
> +		}
> +	}
> +
>  	return rc;
>  }
>  
>  void ima_measure_queued_trusted_keys(void)
>  {
>  	struct ima_trusted_key_entry *entry, *tmp;
> +	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> +	struct ima_template_desc *template_desc = ima_template_desc_current();
> +	int action;
> +	u32 secid;
>  
>  	mutex_lock(&ima_trusted_keys_mutex);
>  
>  	list_for_each_entry_safe(entry, tmp, &ima_trusted_keys, list) {
> +		security_task_getsecid(current, &secid);
> +		action = ima_get_action(NULL, current_cred(), secid, 0,
> +					entry->func, &pcr,
> +					&template_desc);
> +		if (action & IMA_MEASURE) {
> +			process_buffer_measurement(entry->public_key,
> +						   entry->public_key_len,
> +						   entry->key_description,
> +						   pcr,
> +						   template_desc);
> +		}
>  		list_del(&entry->list);
>  		ima_free_trusted_key_entry(entry);
>  	}