[PATCH v2 1/2] IMA: Define workqueue for early boot "key" measurements

Lakshmi Ramasubramanian
2019-12-11T18:51:26Z

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>
---
security/integrity/ima/ima.h | 15 +++
security/integrity/ima/ima_asymmetric_keys.c | 110 +++++++++++++++++++
2 files changed, 125 insertions(+)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index f06238e41a7c..97f8a4078483 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_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+/*
+ * 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_ASYMMETRIC_PUBLIC_KEY_SUBTYPE */
+
/* 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..ba01e04ec025 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -14,6 +14,116 @@
#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.
+ */
+bool ima_process_keys;
+
+/*
+ * To synchronize access to the list of keys that need to be measured
+ */
+static DEFINE_MUTEX(ima_keys_mutex);
+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_mutex);
+ if (!ima_process_keys) {
+ list_add_tail(&entry->list, &ima_keys);
+ queued = true;
+ }
+ mutex_unlock(&ima_keys_mutex);
+
+ 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;
+ LIST_HEAD(temp_ima_keys);
+
+ if (ima_process_keys)
+ return;
+
+ ima_process_keys = true;
+
+ INIT_LIST_HEAD(&temp_ima_keys);
+
+ mutex_lock(&ima_keys_mutex);
+
+ list_for_each_entry_safe(entry, tmp, &ima_keys, list)
+ list_move_tail(&entry->list, &temp_ima_keys);
+
+ mutex_unlock(&ima_keys_mutex);
+
+ list_for_each_entry_safe(entry, tmp, &temp_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