@@ -310,3 +310,17 @@ config IMA_APPRAISE_SIGNED_INIT
default n
help
This option requires user-space init to be signed.
+
+config IMA_MEASURE_ASYMMETRIC_KEYS
+ bool "Enable measuring asymmetric keys on key create or update"
+ depends on IMA
+ depends on KEYS
+ depends on ASYMMETRIC_KEY_TYPE
+ depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+ default n
+ help
+ This option enables measuring asymmetric keys when
+ the key is created or updated. Additionally, IMA policy
+ needs to be configured to either measure keys linked to
+ any keyring or only measure keys linked to the keyrings
+ specified in the IMA policy through the keyrings= option.
@@ -12,3 +12,4 @@ ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
ima-$(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
new file mode 100644
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * File: ima_asymmetric_keys.c
+ * Defines an IMA hook to measure asymmetric keys on key
+ * create or update.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <crypto/public_key.h>
+#include <keys/asymmetric-type.h>
+#include "ima.h"
+
+/**
+ * ima_post_key_create_or_update - measure asymmetric keys
+ * @keyring: keyring to which the key is linked to
+ * @key: created or updated key
+ * @flags: key flags
+ * @create: flag indicating whether the key was created or updated
+ *
+ * Keys can only be measured, not appraised.
+ */
+void ima_post_key_create_or_update(struct key *keyring, struct key *key,
+ unsigned long flags, bool create)
+{
+ const struct public_key *pk;
+
+ /* Only asymmetric keys are handled */
+ if (key->type != &key_type_asymmetric)
+ return;
+
+ /*
+ * Get the public_key of the given asymmetric key to measure.
+ */
+ pk = key->payload.data[asym_crypto];
+ process_buffer_measurement(pk->key, pk->keylen,
+ keyring->description,
+ KEYRING_CHECK, 0,
+ keyring->description);
+}
Asymmetric keys used for verifying file signatures or certificates are currently not included in the IMA measurement list. This patch defines a new IMA hook namely ima_post_key_create_or_update() to measure asymmetric keys. The IMA hook is defined in a new file namely ima_asymmetric_keys.c Note that currently IMA subsystem can be enabled without enabling KEYS subsystem. Adding support for measuring asymmetric keys in IMA requires KEYS subsystem to be enabled. To handle this dependency a new config namely CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS has been added. Enabling this config requires the following configs to be enabled: CONFIG_IMA, CONFIG_KEYS, CONFIG_ASYMMETRIC_KEY_TYPE, and CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE. The new file ima_asymmetric_keys.c is built only if CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. This config is turned off by default. Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> --- security/integrity/ima/Kconfig | 14 +++++++ security/integrity/ima/Makefile | 1 + security/integrity/ima/ima_asymmetric_keys.c | 44 ++++++++++++++++++++ 3 files changed, 59 insertions(+) create mode 100644 security/integrity/ima/ima_asymmetric_keys.c