Re: [PATCH v5 02/10] IMA: Added keyrings= option in IMA policy to only measure keys added to the specified keyrings.

Mimi Zohar
2019-11-12T17:05:16Z

The C maximum line length is 80 characters.  The subject line is even
less than that (~50).  The Subject line here could be "ima: add
support to limit measuring keys".

On Mon, 2019-11-11 at 11:32 -0800, Lakshmi Ramasubramanian wrote:
> IMA policy needs to support measuring only those keys linked to
> a specific set of keyrings.

Patch descriptions should be written in the imperative.  For example,
"Limit measuring keys to those keys being loaded onto a specific
keyring."

>
> This patch defines a new IMA policy option namely "keyrings=" that
> can be used to specify a set of keyrings. If this option is specified
> in the policy for func=KEYRING_CHECK then only the keys linked to
> the keyrings given in "keyrings=" option are measured.

This description does not seem to match the code, which for some
reason isn't included in this patch, nor in 3/10.  Please
combine/squash patches 2 & 3.  Missing from the combined patch is the
keyring matching code in ima_match_rules().

>
> If "keyrings=" option is not specified for func=KEYRING_CHECK then
> all keys are measured.

The last sentence is unnecessary.  Please remove.

>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> ---
> Documentation/ABI/testing/ima_policy | 10 +++++++++-
> security/integrity/ima/ima_policy.c | 2 ++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index 341df49b5ad1..be2874fa3928 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -25,7 +25,7 @@ Description:
> lsm: [[subj_user=] [subj_role=] [subj_type=]
> [obj_user=] [obj_role=] [obj_type=]]
> option: [[appraise_type=]] [template=] [permit_directio]
> - [appraise_flag=]
> + [appraise_flag=] [keyrings=]
> base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
> [FIRMWARE_CHECK]
> [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
> @@ -43,6 +43,9 @@ Description:
> appraise_flag:= [check_blacklist]
> Currently, blacklist check is only for files signed with appended
> signature.
> + keyrings:= list of keyrings
> + (eg, .builtin_trusted_keys|.ima). Only valid
> + when action is "measure" and func is KEYRING_CHECK.
> template:= name of a defined IMA template type
> (eg, ima-ng). Only valid when action is "measure".
> pcr:= decimal value
> @@ -119,3 +122,8 @@ Description:
> all keys:
>
> measure func=KEYRING_CHECK
> +
> + Example of measure rule using KEYRING_CHECK to only measure
> + keys added to .builtin_trusted_keys or .ima keyring:
> +
> + measure func=KEYRING_CHECK keyrings=.builtin_trusted_keys|.ima
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 9ca32ffaaa9d..a0f7ffa80736 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -34,6 +34,7 @@
> #define IMA_EUID 0x0080
> #define IMA_PCR 0x0100
> #define IMA_FSNAME 0x0200
> +#define IMA_KEYRINGS 0x0400
>
> #define UNKNOWN 0
> #define MEASURE 0x0001 /* same as IMA_MEASURE */
> @@ -79,6 +80,7 @@ struct ima_rule_entry {
> int type; /* audit type */
> } lsm[MAX_LSM_RULES];
> char *fsname;
> + char *keyrings; /* Measure keys added to these keyrings */
> struct ima_template_desc *template;
> };
>