IMA: Define an IMA hook to measure keys

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_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += ima_asymmetric_keys.o

// 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 <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

 * @payload: The data used to instantiate or update the key.

 * @payload_len: The length of @payload.

 * @flags: key flags

 * @create: flag indicating whether the key was created or updated

 *

 * Keys can only be measured, not appraised.

 * The payload data used to instantiate or update the key is measured.

 */

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)

{

	/* Only asymmetric keys are handled by this hook. */

	if (key->type != &key_type_asymmetric)

		return;

	if (!payload || (payload_len == 0))

		return;

	/*

	 * 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(payload, payload_len,

				   keyring->description, KEY_CHECK, 0);

}