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Subject[PATCH v7 2/5] IMA: Define an IMA hook to measure keys
Date
Measure asymmetric keys used for verifying file signatures,
certificates, etc.

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
which is built only if CONFIG_KEYS is enabled.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
security/integrity/ima/Makefile | 1 +
security/integrity/ima/ima_asymmetric_keys.c | 51 ++++++++++++++++++++
2 files changed, 52 insertions(+)
create mode 100644 security/integrity/ima/ima_asymmetric_keys.c

diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 31d57cdf2421..3c796664be8a 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -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_KEYS) += ima_asymmetric_keys.o
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
new file mode 100644
index 000000000000..f6884641a622
--- /dev/null
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -0,0 +1,51 @@
+// 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 by this hook. */
+ if (key->type != &key_type_asymmetric)
+ return;
+
+ /* Get the public_key of the given asymmetric key to measure. */
+ pk = key->payload.data[asym_crypto];
+
+ /*
+ * keyring->description points to the name of the keyring
+ * (such as ".builtin_trusted_keys", ".ima", etc.) to
+ * which the given key is linked to.
+ *
+ * The name of the keyring is passed in the "eventname"
+ * parameter to process_buffer_measurement() and is set
+ * in the "eventname" field in ima_event_data for
+ * the key measurement IMA event.
+ */
+ process_buffer_measurement(pk->key, pk->keylen,
+ keyring->description, KEY_CHECK, 0);
+}
--
2.17.1
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