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

Mimi Zohar
2019-10-23T13:23:22Z

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@linux.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);
> }