linux-kernel - Re: [PATCH v3 1/9] KEYS: Defined an IMA hook to measure keys on key create or update

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Date:   Thu, 31 Oct 2019 08:10:31 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        dhowells@...hat.com, matthewgarrett@...gle.com, sashal@...nel.org,
        jamorris@...ux.microsoft.com, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Cc:     prsriva@...ux.microsoft.com
Subject: Re: [PATCH v3 1/9] KEYS: Defined an IMA hook to measure keys on key
 create or update

On Wed, 2019-10-30 at 18:19 -0700, Lakshmi Ramasubramanian wrote:
> 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.

It's not enough for the kernel to be able to compile the kernel after
applying all the patches in a patch set.  After applying each patch,
the kernel should build properly, otherwise it is not bi-sect safe.
 Refer to "3) Separate your changes" of
"Documentation/process/submitting-patches.rst.
 
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  security/integrity/ima/ima.h      |  2 ++
>  security/integrity/ima/ima_main.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 997a57137351..22d0628faf56 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -21,6 +21,8 @@
>  #include <linux/tpm.h>
>  #include <linux/audit.h>
>  #include <crypto/hash_info.h>
> +#include <crypto/public_key.h>
> +#include <keys/asymmetric-type.h>
>  
>  #include "../integrity.h"
>  
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 492b8f241d39..18e1bc105be7 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -635,6 +635,9 @@ void process_buffer_measurement(const void *buf, int size,
>  	int action = 0;
>  	u32 secid;
>  
> +	if (!ima_policy_flag)
> +		return;
> +
>  	if (func) {
>  		security_task_getsecid(current, &secid);
>  		action = ima_get_action(NULL, current_cred(), secid, 0, func,
> @@ -695,6 +698,29 @@ void ima_kexec_cmdline(const void *buf, int size)
>  	}
>  }
>  
> +/**
> + * 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;
> +
> +	if (key->type != &key_type_asymmetric)
> +		return;
> +
> +	pk = key->payload.data[asym_crypto];
> +	process_buffer_measurement(pk->key, pk->keylen,
> +				   keyring->description,
> +				   NONE, 0);

This patch should also define the new "func".

Mimi

> +}
> +
>  static int __init init_ima(void)
>  {
>  	int error;