[PATCH v8 0/3] IMA: Deferred measurement of keys

[PATCH v8 0/3] IMA: Deferred measurement of keys

[Lakshmi Ramasubramanian]

The IMA subsystem supports measuring asymmetric keys when the key is
created or updated[1]. But keys created or updated before a custom
IMA policy is loaded are currently not measured. This includes keys
added, for instance, to either the .ima or .builtin_trusted_keys keyrings,
which happens early in the boot process.

Measuring the early boot keys, by design, requires loading
a custom IMA policy. This change adds support for queuing keys
created or updated before a custom IMA policy is loaded.
The queued keys are processed when a custom policy is loaded.
Keys created or updated after a custom policy is loaded are measured
immediately (not queued). In the case when a custom policy is not loaded
within 5 minutes of IMA initialization, the queued keys are freed.

[1] https://lore.kernel.org/linux-integrity/20191211164707.4698-1-nramas@linux.microsoft.com/

Testing performed:

  * Ran kernel self-test following the instructions given in
    https://www.kernel.org/doc/Documentation/kselftest.txt
  * Ran the lkp-tests using the job script provided by
    kernel test robot <rong.a.chen@intel.com>
  * Booted the kernel with this change.
  * Added .builtin_trusted_keys in "keyrings=" option in
    the IMA policy and verified the keys added to this
    keyring are measured.
  * Specified only func=KEY_CHECK and not "keyrings=" option,
    and verified the keys added to builtin_trusted_keys keyring
    are processed.
  * Added keys at runtime and verified they are measured
    if the IMA policy permitted.
      => For example, added keys to .ima keyring and verified.

Changelog:

  v8

  => Rebased the changes to linux-next
  => Need to apply the following patch first
  https://lore.kernel.org/linux-integrity/20200108160508.5938-1-nramas@linux.microsoft.com/

  v7

  => Updated cover letter per Mimi's suggestions.
  => Updated "Reported-by" tag to be specific about
     the issues fixed in the patch.

  v6

  => Replaced mutex with a spinlock to sychronize access to
     queued keys. This fixes the problem reported by
     "kernel test robot <rong.a.chen@intel.com>"
     https://lore.kernel.org/linux-integrity/2a831fe9-30e5-63b4-af10-a69f327f7fb7@linux.microsoft.com/T/#t
  => Changed ima_queue_key() to a static function. This fixes
     the issue reported by "kbuild test robot <lkp@intel.com>"
     https://lore.kernel.org/linux-integrity/1577370464.4487.10.camel@linux.ibm.com/
  => Added the patch to free the queued keys if a custom IMA policy
     was not loaded to this patch set.

  v5

  => Removed temp keys list in ima_process_queued_keys()

  v4

  => Check and set ima_process_keys flag with mutex held.

  v3

  => Defined ima_process_keys flag to be static.
  => Set ima_process_keys with ima_keys_mutex held.
  => Added a comment in ima_process_queued_keys() function
     to state the use of temporary list for keys.

  v2

  => Rebased the changes to v5.5-rc1
  => Updated function names, variable names, and code comments
     to be less verbose.

  v1

  => Code cleanup

  v0

  => Based changes on v5.4-rc8
  => The following patchsets should be applied in that order
     https://lore.kernel.org/linux-integrity/1572492694-6520-1-git-send-email-zohar@linux.ibm.com
     https://lore.kernel.org/linux-integrity/20191204224131.3384-1-nramas@linux.microsoft.com/
  => Added functions to queue and dequeue keys, and process
     the queued keys when custom IMA policies are applied.

Lakshmi Ramasubramanian (3):
  IMA: Define workqueue for early boot key measurements
  IMA: Call workqueue functions to measure queued keys
  IMA: Defined timer to free queued keys

 security/integrity/ima/ima.h                 |  17 ++
 security/integrity/ima/ima_asymmetric_keys.c | 159 +++++++++++++++++++
 security/integrity/ima/ima_init.c            |   8 +-
 security/integrity/ima/ima_policy.c          |   3 +
 4 files changed, 186 insertions(+), 1 deletion(-)

-- 
2.17.1

[PATCH v8 1/3] IMA: Define workqueue for early boot key measurements

[Lakshmi Ramasubramanian]

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.

This patch defines workqueue for queuing keys when a custom IMA policy
has not yet been loaded.

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>
Reported-by: kernel test robot <rong.a.chen@intel.com> # sleeping
function called from invalid context
Reported-by: kbuild test robot <lkp@intel.com> # sparse symbol
ima_queued_key() should be static
---
 security/integrity/ima/ima.h                 |  15 +++
 security/integrity/ima/ima_asymmetric_keys.c | 115 +++++++++++++++++++
 2 files changed, 130 insertions(+)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index f06238e41a7c..c7fdf3d66b98 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -205,6 +205,21 @@ extern const char *const func_tokens[];
 
 struct modsig;
 
+#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_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;
+};
+void ima_process_queued_keys(void);
+#else
+static inline void ima_process_queued_keys(void) {}
+#endif /* CONFIG_IMA_MEASURE_ASYMMETRIC_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_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index fea2e7dd3b09..1d56f003f1a7 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -14,6 +14,121 @@
 #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_SPINLOCK(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;
+}
+
+static 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;
+
+	spin_lock(&ima_keys_lock);
+	if (!ima_process_keys) {
+		list_add_tail(&entry->list, &ima_keys);
+		queued = true;
+	}
+	spin_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.
+	 */
+	spin_lock(&ima_keys_lock);
+	if (!ima_process_keys) {
+		ima_process_keys = true;
+		process = true;
+	}
+	spin_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);
+	}
+}
+
 /**
  * ima_post_key_create_or_update - measure asymmetric keys
  * @keyring: keyring to which the key is linked to
-- 
2.17.1

[PATCH v8 2/3] IMA: Call workqueue functions to measure queued keys

[Lakshmi Ramasubramanian]

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@linux.microsoft.com>
---
 security/integrity/ima/ima_asymmetric_keys.c | 8 ++++++++
 security/integrity/ima/ima_policy.c          | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 1d56f003f1a7..eb71cbf224c1 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -145,6 +145,8 @@ 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 queued = false;
+
 	/* Only asymmetric keys are handled by this hook. */
 	if (key->type != &key_type_asymmetric)
 		return;
@@ -152,6 +154,12 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 	if (!payload || (payload_len == 0))
 		return;
 
+	if (!ima_process_keys)
+		queued = ima_queue_key(keyring, payload, payload_len);
+
+	if (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 8f2ca487753b..1bdda05d963b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -807,6 +807,9 @@ void ima_update_policy(void)
 		kfree(arch_policy_entry);
 	}
 	ima_update_policy_flag();
+
+	/* Custom IMA policy has been loaded */
+	ima_process_queued_keys();
 }
 
 /* Keep the enumeration in sync with the policy_tokens! */
-- 
2.17.1

[PATCH v8 3/3] IMA: Defined timer to free queued keys

[Lakshmi Ramasubramanian]

keys queued for measurement should be freed if a custom IMA policy
was not loaded. Otherwise, the keys will remain queued forever
consuming kernel memory.

This patch defines a timer to handle the above scenario. The timer
is setup to expire 5 minutes after IMA initialization is completed.

If a custom IMA policy is loaded before the timer expires, the timer
is removed and any queued keys are processed for measurement.
But if a custom policy was not loaded, on timer expiration
queued keys are just freed.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reported-by: kernel test robot <rong.a.chen@intel.com> # sleeping
function called from invalid context
Reported-by: kbuild test robot <lkp@intel.com> # redefinition of
ima_init_key_queue() function.
---
 security/integrity/ima/ima.h                 |  2 +
 security/integrity/ima/ima_asymmetric_keys.c | 42 ++++++++++++++++++--
 security/integrity/ima/ima_init.c            |  8 +++-
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index c7fdf3d66b98..6bb3152b3e24 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -216,8 +216,10 @@ struct ima_key_entry {
 	char *keyring_name;
 };
 void ima_process_queued_keys(void);
+void ima_init_key_queue(void);
 #else
 static inline void ima_process_queued_keys(void) {}
+static inline void ima_init_key_queue(void) {}
 #endif /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
 
 /* LIM API function definitions */
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index eb71cbf224c1..d1fa1706e03f 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -11,6 +11,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/timer.h>
 #include <keys/asymmetric-type.h>
 #include "ima.h"
 
@@ -26,6 +27,36 @@ static bool ima_process_keys;
 static DEFINE_SPINLOCK(ima_keys_lock);
 static LIST_HEAD(ima_keys);
 
+/*
+ * If custom IMA policy is not loaded then keys queued up
+ * for measurement should be freed. This timer is used
+ * for handling this scenario.
+ */
+static long ima_key_queue_timeout = 300000; /* 5 Minutes */
+static struct timer_list ima_key_queue_timer;
+static bool timer_expired;
+
+/*
+ * This timer callback function frees keys that may still be
+ * queued up in case custom IMA policy was not loaded.
+ */
+static void ima_timer_handler(struct timer_list *timer)
+{
+	timer_expired = true;
+	ima_process_queued_keys();
+}
+
+/*
+ * This function sets up a timer to free queued keys in case
+ * custom IMA policy was never loaded.
+ */
+void ima_init_key_queue(void)
+{
+	timer_setup(&ima_key_queue_timer, ima_timer_handler, 0);
+	mod_timer(&ima_key_queue_timer,
+		  jiffies + msecs_to_jiffies(ima_key_queue_timeout));
+}
+
 static void ima_free_key_entry(struct ima_key_entry *entry)
 {
 	if (entry) {
@@ -120,10 +151,15 @@ void ima_process_queued_keys(void)
 	if (!process)
 		return;
 
+	del_timer(&ima_key_queue_timer);
+
 	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);
+		if (!timer_expired)
+			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);
 	}
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 5d55ade5f3b9..195cb4079b2b 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -131,5 +131,11 @@ int __init ima_init(void)
 
 	ima_init_policy();
 
-	return ima_fs_init();
+	rc = ima_fs_init();
+	if (rc != 0)
+		return rc;
+
+	ima_init_key_queue();
+
+	return rc;
 }
-- 
2.17.1

Re: [PATCH v8 0/3] IMA: Deferred measurement of keys

[Mimi Zohar]

On Wed, 2020-01-08 at 18:43 -0800, Lakshmi Ramasubramanian wrote:

> Changelog:
> 
>   v8
> 
>   => Rebased the changes to linux-next
>   => Need to apply the following patch first
>   https://lore.kernel.org/linux-integrity/20200108160508.5938-1-nramas@linux.microsoft.com/

Unless you made some other changes, the previous version of this patch
set is already in next-integrity-testing.  There's no reason to re-
post these patches again, and definitely not against linux-next.

Mimi

Re: [PATCH v8 0/3] IMA: Deferred measurement of keys

[Lakshmi Ramasubramanian]

On 1/8/20 9:07 PM, Mimi Zohar wrote:

> On Wed, 2020-01-08 at 18:43 -0800, Lakshmi Ramasubramanian wrote:
> 
>> Changelog:
>>
>>    v8
>>
>>    => Rebased the changes to linux-next
>>    => Need to apply the following patch first
>>    https://lore.kernel.org/linux-integrity/20200108160508.5938-1-nramas@linux.microsoft.com/
> 
> Unless you made some other changes, the previous version of this patch
> set is already in next-integrity-testing.  There's no reason to re-
> post these patches again, and definitely not against linux-next.
> 
> Mimi
> 

The change was to integrate the changes from the patch for the CONFIG issue:

https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git/commit/?h=next-integrity-testing&id=50a2506e069fc71f4be1bbcc2c5534bf58ed94ab

The following commit needs to be updated to use the new config 
CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS instead of 
CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE

https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git/commit/?h=next-integrity-testing&id=e164a1695a5705c24c897b0bc7e9b97abb0830c8

Please let me know if I can clone next-integrity-testing and make the 
above update. I'll post the updated patch today.

thanks,
  -lakshmi

[PATCH v8 3/3] IMA: Defined timer to free queued keys

[Lakshmi Ramasubramanian]

keys queued for measurement should be freed if a custom IMA policy
was not loaded. Otherwise, the keys will remain queued forever
consuming kernel memory.

This patch defines a timer to handle the above scenario. The timer
is setup to expire 5 minutes after IMA initialization is completed.

If a custom IMA policy is loaded before the timer expires, the timer
is removed and any queued keys are processed for measurement.
But if a custom policy was not loaded, on timer expiration
queued keys are just freed.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reported-by: kernel test robot <rong.a.chen@intel.com> # sleeping
function called from invalid context
Reported-by: kbuild test robot <lkp@intel.com> # redefinition of
ima_init_key_queue() function.
---
 security/integrity/ima/ima.h                 |  2 +
 security/integrity/ima/ima_asymmetric_keys.c | 42 ++++++++++++++++++--
 security/integrity/ima/ima_init.c            |  8 +++-
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index c7fdf3d66b98..6bb3152b3e24 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -216,8 +216,10 @@ struct ima_key_entry {
 	char *keyring_name;
 };
 void ima_process_queued_keys(void);
+void ima_init_key_queue(void);
 #else
 static inline void ima_process_queued_keys(void) {}
+static inline void ima_init_key_queue(void) {}
 #endif /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
 
 /* LIM API function definitions */
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index eb71cbf224c1..d1fa1706e03f 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -11,6 +11,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/timer.h>
 #include <keys/asymmetric-type.h>
 #include "ima.h"
 
@@ -26,6 +27,36 @@ static bool ima_process_keys;
 static DEFINE_SPINLOCK(ima_keys_lock);
 static LIST_HEAD(ima_keys);
 
+/*
+ * If custom IMA policy is not loaded then keys queued up
+ * for measurement should be freed. This timer is used
+ * for handling this scenario.
+ */
+static long ima_key_queue_timeout = 300000; /* 5 Minutes */
+static struct timer_list ima_key_queue_timer;
+static bool timer_expired;
+
+/*
+ * This timer callback function frees keys that may still be
+ * queued up in case custom IMA policy was not loaded.
+ */
+static void ima_timer_handler(struct timer_list *timer)
+{
+	timer_expired = true;
+	ima_process_queued_keys();
+}
+
+/*
+ * This function sets up a timer to free queued keys in case
+ * custom IMA policy was never loaded.
+ */
+void ima_init_key_queue(void)
+{
+	timer_setup(&ima_key_queue_timer, ima_timer_handler, 0);
+	mod_timer(&ima_key_queue_timer,
+		  jiffies + msecs_to_jiffies(ima_key_queue_timeout));
+}
+
 static void ima_free_key_entry(struct ima_key_entry *entry)
 {
 	if (entry) {
@@ -120,10 +151,15 @@ void ima_process_queued_keys(void)
 	if (!process)
 		return;
 
+	del_timer(&ima_key_queue_timer);
+
 	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);
+		if (!timer_expired)
+			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);
 	}
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 5d55ade5f3b9..195cb4079b2b 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -131,5 +131,11 @@ int __init ima_init(void)
 
 	ima_init_policy();
 
-	return ima_fs_init();
+	rc = ima_fs_init();
+	if (rc != 0)
+		return rc;
+
+	ima_init_key_queue();
+
+	return rc;
 }
-- 
2.17.1