On Mon, 2020-06-22 at 19:32 -0500, Tyler Hicks wrote:
> Buffer based hook functions, such as KEXEC_CMDLINE and KEY_CHECK, can
> only measure. The process_buffer_measurement() function quietly ignores
> all actions except measure so make this behavior clear at the time of
> policy load.
>
> The parsing of the keyrings conditional had a check to ensure that it
> was only specified with measure actions but the check should be on the
> hook function and not the keyrings conditional since
> "appraise func=KEY_CHECK" is not a valid rule.
>
> Fixes: b0935123a183 ("IMA: Define a new hook to measure the kexec boot command line arguments")
> Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
> Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
> ---
> security/integrity/ima/ima_policy.c | 36 +++++++++++++++++++++++++++--
> 1 file changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index ee5152ecd3d9..ecc234b956a2 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -979,6 +979,39 @@ static void check_template_modsig(const struct ima_template_desc *template)
> #undef MSG
> }
>
> +static bool ima_validate_rule(struct ima_rule_entry *entry)
> +{
> + if (entry->action == UNKNOWN)
> + return false;
> +
> + if (entry->flags & IMA_FUNC) {
> + switch (entry->func) {
> + case NONE:
> + case FILE_CHECK:
> + case MMAP_CHECK:
> + case BPRM_CHECK:
> + case CREDS_CHECK:
> + case POST_SETATTR:
> + case MODULE_CHECK:
> + case FIRMWARE_CHECK:
> + case KEXEC_KERNEL_CHECK:
> + case KEXEC_INITRAMFS_CHECK:
> + case POLICY_CHECK:
> + break;
> + case KEXEC_CMDLINE:
> + case KEY_CHECK:
> + if (entry->action & ~(MEASURE | DONT_MEASURE))
> + return false;
> +
> + break;
> + default:
> + return false;
> + }
> + }
> +
> + return true;
> +}
> +
Good idea. There are a couple of other examples that could be cleaned
up as well. For example, for performance reasons
"appraise_flag=check_blacklist" is limited to files with appended
signatures, like kernel modules and the kexec kernel image
(OpenPower).
Mimi
