linux-kernel - Re: [PATCH v6 1/3] IMA: Add KEY

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Message-Id: <1573676066.4843.18.camel@linux.ibm.com>
Date:   Wed, 13 Nov 2019 15:14:26 -0500
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-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] IMA: Add KEY_CHECK func to measure keys

On Wed, 2019-11-13 at 10:46 -0800, Lakshmi Ramasubramanian wrote:
> Measure keys loaded onto any keyring.
> 
> This patch defines a new IMA policy func namely KEY_CHECK to
> measure keys. Updated ima_match_rules() to check for KEY_CHECK
> and ima_parse_rule() to handle KEY_CHECK.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  Documentation/ABI/testing/ima_policy | 6 +++++-
>  security/integrity/ima/ima.h         | 1 +
>  security/integrity/ima/ima_main.c    | 7 +++++++
>  security/integrity/ima/ima_policy.c  | 4 +++-
>  4 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index 29aaedf33246..066d32797500 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -29,7 +29,7 @@ Description:
>  		base: 	func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
>  				[FIRMWARE_CHECK]
>  				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
> -				[KEXEC_CMDLINE]
> +				[KEXEC_CMDLINE] [KEY_CHECK]
>  			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
>  			       [[^]MAY_EXEC]
>  			fsmagic:= hex value
> @@ -113,3 +113,7 @@ Description:
>  		Example of appraise rule allowing modsig appended signatures:
>  
>  			appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
> +
> +		Example of measure rule using KEY_CHECK to measure all keys:
> +
> +			measure func=KEY_CHECK
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index df4ca482fb53..fe6c698617bd 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -193,6 +193,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
>  	hook(KEXEC_INITRAMFS_CHECK)	\
>  	hook(POLICY_CHECK)		\
>  	hook(KEXEC_CMDLINE)		\
> +	hook(KEY_CHECK)			\
>  	hook(MAX_CHECK)
>  #define __ima_hook_enumify(ENUM)	ENUM,
>  
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index d7e987baf127..12684e8d7124 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -655,6 +655,13 @@ void process_buffer_measurement(const void *buf, int size,
>  	int action = 0;
>  	u32 secid;
>  
> +	/*
> +	 * If IMA is not yet initialized or IMA policy is empty
> +	 * then there is no need to measure.
> +	 */
> +	if (!ima_policy_flag)
> +		return;
> +

This addition has nothing to do with defining a new IMA hook and
should be a separate patch.  This can be posted independently of this
patch set.

Mimi

>  	/*
>  	 * Both LSM hooks and auxilary based buffer measurements are
>  	 * based on policy.  To avoid code duplication, differentiate
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index f19a895ad7cd..1525a28fd705 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -373,7 +373,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>  {
>  	int i;
>  
> -	if (func == KEXEC_CMDLINE) {
> +	if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
>  		if ((rule->flags & IMA_FUNC) && (rule->func == func))
>  			return true;
>  		return false;
> @@ -997,6 +997,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  				entry->func = POLICY_CHECK;
>  			else if (strcmp(args[0].from, "KEXEC_CMDLINE") == 0)
>  				entry->func = KEXEC_CMDLINE;
> +			else if (strcmp(args[0].from, "KEY_CHECK") == 0)
> +				entry->func = KEY_CHECK;
>  			else
>  				result = -EINVAL;
>  			if (!result)