On Wed, 2019-12-04 at 14:41 -0800, Lakshmi Ramasubramanian wrote:
> 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 the payload used to create a new key or update an existing key.
>
> The IMA hook is defined in a new file namely ima_asymmetric_keys.c
> which is built only if CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is enabled.
Missing from the last paragraph is the reason for requiring a new
file. I would prefix this last paragraph, explaining that the
asymmetric key structure is only defined when
CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is defined.
Mimi
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
> ---
> security/integrity/ima/Makefile | 1 +
> security/integrity/ima/ima_asymmetric_keys.c | 52 ++++++++++++++++++++
> 2 files changed, 53 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..207a0a9eb72c 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_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += 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..994d89d58af9
> --- /dev/null
> +++ b/security/integrity/ima/ima_asymmetric_keys.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2019 Microsoft Corporation
> + *
> + * Author: Lakshmi Ramasubramanian (nramas@xxxxxxxxxxxxxxxxxxx)
> + *
> + * 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);
> +}
