Hi Lakshmi,
On Thu, 2020-11-19 at 15:26 -0800, Tushar Sugandhi wrote:
> From: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
>
> The IMA hook to measure kernel critical data, namely
> ima_measure_critical_data(), could be called before a custom IMA policy
> is loaded.
> Define a new critical data builtin policy to allow measuring
> early kernel integrity critical data before a custom IMA policy is
> loaded.
Everything needing to be said seems to be included in the second
sentence. Does the first sentence add anything? "Define a new
critical data builtin policy" makes for a good Subject line.
>
> Add critical data to built-in IMA rules if the kernel command line
> contains "ima_policy=critical_data".
The boot command line parameters are defined in Documentation/admin-
guide/kernel-parameters.txt. Please update "ima_policy".
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
> ---
> security/integrity/ima/ima_policy.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index c9e52dab0638..119604a3efa0 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -206,6 +206,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
> .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
> };
>
> +static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
> + {.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
> +};
> +
> /* An array of architecture specific rules */
> static struct ima_rule_entry *arch_policy_entry __ro_after_init;
>
> @@ -228,6 +232,7 @@ __setup("ima_tcb", default_measure_policy_setup);
>
> static bool ima_use_appraise_tcb __initdata;
> static bool ima_use_secure_boot __initdata;
> +static bool ima_use_critical_data __ro_after_init;
Unlike ima_fail_unverifiable_sigs, ima_use_critical_data is only used
during __init. Please change "__ro_after_init" to "__initdata". (The
critical data policy itself is defined properly as __ro_after_init.)
> static bool ima_fail_unverifiable_sigs __ro_after_init;
> static int __init policy_setup(char *str)
> {
> @@ -242,6 +247,8 @@ static int __init policy_setup(char *str)
> ima_use_appraise_tcb = true;
> else if (strcmp(p, "secure_boot") == 0)
> ima_use_secure_boot = true;
> + else if (strcmp(p, "critical_data") == 0)
> + ima_use_critical_data = true;
> else if (strcmp(p, "fail_securely") == 0)
> ima_fail_unverifiable_sigs = true;
> else
> @@ -875,6 +882,11 @@ void __init ima_init_policy(void)
> ARRAY_SIZE(default_appraise_rules),
> IMA_DEFAULT_POLICY);
>
> + if (ima_use_critical_data)
> + add_rules(critical_data_rules,
> + ARRAY_SIZE(critical_data_rules),
> + IMA_DEFAULT_POLICY);
> +
> ima_update_policy_flag();
> }
>
