IMA: Define workqueue for early boot key measurements

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
will be processed after a custom policy is loaded.

This patch defines a 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>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 355754a..711ff10 100644 (file)
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -316,3 +316,9 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
        depends on IMA
        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 3e9d0ad..064a256 100644 (file)
--- 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 f06238e..905ed2f 100644 (file)
--- 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 (file)
index 0000000..9b561f2
--- /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;
+}