From: Lakshmi Ramasubramanian Date: Mon, 11 Nov 2019 19:32:59 +0000 Subject: [PATCH v5 06/10] IMA: Defined an IMA hook to measure keys on key create or update Message-Id: <20191111193303.12781-7-nramas@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <20191111193303.12781-1-nramas@linux.microsoft.com> In-Reply-To: <20191111193303.12781-1-nramas@linux.microsoft.com> To: zohar@linux.ibm.com, dhowells@redhat.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org 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 --- 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 diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index 838476d780e5..c6d14884bc19 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -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. diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile index 31d57cdf2421..3e9d0ad68c7b 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_IMA_MEASURE_ASYMMETRIC_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..7d6603bfcc06 --- /dev/null +++ b/security/integrity/ima/ima_asymmetric_keys.c @@ -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 +#include +#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); +} -- 2.17.1