Re: [PATCH v9 1/3] IMA: Define workqueue for early boot key measurements

[Mimi Zohar <zohar@linux.ibm.com>]

Hi Lakshmi,

On Wed, 2020-01-22 at 17:32 -0800, Lakshmi Ramasubramanian wrote:
> Measuring keys requires a custom IMA policy to be loaded.
> Keys created or updated before a custom IMA policy is loaded should
> be queued and the keys should be processed after a custom policy
> is loaded.

The addition of "and the keys" makes the sentence a run-on.  I've
reverted this change.

> 
> This patch defines workqueue for queuing keys when a custom IMA policy
> has not yet been loaded. An intermediate Kconfig boolean option namely
> IMA_QUEUE_EARLY_BOOT_KEYS is used to declare the workqueue functions.
> 
> A flag namely ima_process_keys is used to check if the key should be
> queued or should be processed immediately.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Thanks!  With this patch, if queueing keys ever becomes an issue,
resolving it will be straight forward.

This patch set is now in the next-integrity-testing branch.  Assuming
there are no problems, it will be merged into the next-integrity
branch, requiring a rebase.  I'm sorry for any inconvenience this may
cause.

Mimi

> ---
>  security/integrity/ima/Kconfig          |   5 +
>  security/integrity/ima/Makefile         |   1 +
>  security/integrity/ima/ima.h            |  22 ++++
>  security/integrity/ima/ima_queue_keys.c | 137 ++++++++++++++++++++++++
>  4 files changed, 165 insertions(+)
>  create mode 100644 security/integrity/ima/ima_queue_keys.c
> 
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 6bec78eeeae8..711ff10fa36e 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -317,3 +317,8 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
>  	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
>  	default y
>  
> +config IMA_QUEUE_EARLY_BOOT_KEYS
> +	bool
> +	depends on IMA_MEASURE_ASYMMETRIC_KEYS
> +	depends on SYSTEM_TRUSTED_KEYRING
> +	default y
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index 3e9d0ad68c7b..064a256f8725 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -13,3 +13,4 @@ ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
>  ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
>  obj-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
> +obj-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index f06238e41a7c..905ed2f7f778 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -205,6 +205,28 @@ extern const char *const func_tokens[];
>  
>  struct modsig;
>  
> +#ifdef CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS
> +/*
> + * To track keys that need to be measured.
> + */
> +struct ima_key_entry {
> +	struct list_head list;
> +	void *payload;
> +	size_t payload_len;
> +	char *keyring_name;
> +};
> +bool ima_should_queue_key(void);
> +bool ima_queue_key(struct key *keyring, const void *payload,
> +		   size_t payload_len);
> +void ima_process_queued_keys(void);
> +#else
> +static inline bool ima_should_queue_key(void) { return false; }
> +static inline bool ima_queue_key(struct key *keyring,
> +				 const void *payload,
> +				 size_t payload_len) { return false; }
> +static inline void ima_process_queued_keys(void) {}
> +#endif /* CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS */
> +
>  /* LIM API function definitions */
>  int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>  		   int mask, enum ima_hooks func, int *pcr,
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> new file mode 100644
> index 000000000000..9b561f2b86db
> --- /dev/null
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -0,0 +1,137 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2019 Microsoft Corporation
> + *
> + * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
> + *
> + * File: ima_queue_keys.c
> + *       Enables deferred processing of keys
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <keys/asymmetric-type.h>
> +#include "ima.h"
> +
> +/*
> + * Flag to indicate whether a key can be processed
> + * right away or should be queued for processing later.
> + */
> +static bool ima_process_keys;
> +
> +/*
> + * To synchronize access to the list of keys that need to be measured
> + */
> +static DEFINE_MUTEX(ima_keys_lock);
> +static LIST_HEAD(ima_keys);
> +
> +static void ima_free_key_entry(struct ima_key_entry *entry)
> +{
> +	if (entry) {
> +		kfree(entry->payload);
> +		kfree(entry->keyring_name);
> +		kfree(entry);
> +	}
> +}
> +
> +static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
> +						 const void *payload,
> +						 size_t payload_len)
> +{
> +	int rc = 0;
> +	struct ima_key_entry *entry;
> +
> +	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> +	if (entry) {
> +		entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
> +		entry->keyring_name = kstrdup(keyring->description,
> +					      GFP_KERNEL);
> +		entry->payload_len = payload_len;
> +	}
> +
> +	if ((entry == NULL) || (entry->payload == NULL) ||
> +	    (entry->keyring_name == NULL)) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	INIT_LIST_HEAD(&entry->list);
> +
> +out:
> +	if (rc) {
> +		ima_free_key_entry(entry);
> +		entry = NULL;
> +	}
> +
> +	return entry;
> +}
> +
> +bool ima_queue_key(struct key *keyring, const void *payload,
> +		   size_t payload_len)
> +{
> +	bool queued = false;
> +	struct ima_key_entry *entry;
> +
> +	entry = ima_alloc_key_entry(keyring, payload, payload_len);
> +	if (!entry)
> +		return false;
> +
> +	mutex_lock(&ima_keys_lock);
> +	if (!ima_process_keys) {
> +		list_add_tail(&entry->list, &ima_keys);
> +		queued = true;
> +	}
> +	mutex_unlock(&ima_keys_lock);
> +
> +	if (!queued)
> +		ima_free_key_entry(entry);
> +
> +	return queued;
> +}
> +
> +/*
> + * ima_process_queued_keys() - process keys queued for measurement
> + *
> + * This function sets ima_process_keys to true and processes queued keys.
> + * From here on keys will be processed right away (not queued).
> + */
> +void ima_process_queued_keys(void)
> +{
> +	struct ima_key_entry *entry, *tmp;
> +	bool process = false;
> +
> +	if (ima_process_keys)
> +		return;
> +
> +	/*
> +	 * Since ima_process_keys is set to true, any new key will be
> +	 * processed immediately and not be queued to ima_keys list.
> +	 * First one setting the ima_process_keys flag to true will
> +	 * process the queued keys.
> +	 */
> +	mutex_lock(&ima_keys_lock);
> +	if (!ima_process_keys) {
> +		ima_process_keys = true;
> +		process = true;
> +	}
> +	mutex_unlock(&ima_keys_lock);
> +
> +	if (!process)
> +		return;
> +
> +
> +	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
> +		process_buffer_measurement(entry->payload,
> +					   entry->payload_len,
> +					   entry->keyring_name,
> +					   KEY_CHECK, 0,
> +					   entry->keyring_name);
> +		list_del(&entry->list);
> +		ima_free_key_entry(entry);
> +	}
> +}
> +
> +inline bool ima_should_queue_key(void)
> +{
> +	return !ima_process_keys;
> +}