On 2020-12-09 11:42:11, Tushar Sugandhi wrote:
> From: Lakshmi Ramasubramanian <nra...@linux.microsoft.com>
>
> Define a new critical data builtin policy to allow measuring
> early kernel integrity critical data before a custom IMA policy
> is loaded.
>
> Add critical data to built-in IMA rules if the kernel command line
> contains "ima_policy=critical_data".
>
> Update the documentation on kernel parameters to document
> the new critical data builtin policy.
>
> Signed-off-by: Lakshmi Ramasubramanian <nra...@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhi...@linux.microsoft.com>
Tyler
> ---
> Documentation/admin-guide/kernel-parameters.txt | 5 ++++-
> security/integrity/ima/ima_policy.c | 12 ++++++++++++
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt
> b/Documentation/admin-guide/kernel-parameters.txt
> index 526d65d8573a..6034d75c3ca0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1746,7 +1746,7 @@
> ima_policy= [IMA]
> The builtin policies to load during IMA setup.
> Format: "tcb | appraise_tcb | secure_boot |
> - fail_securely"
> + fail_securely | critical_data"
>
> The "tcb" policy measures all programs exec'd, files
> mmap'd for exec, and all files opened with the read
> @@ -1765,6 +1765,9 @@
> filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
> flag.
>
> + The "critical_data" policy measures kernel integrity
> + critical data.
> +
> ima_tcb [IMA] Deprecated. Use ima_policy= instead.
> Load a policy which meets the needs of the Trusted
> Computing Base. This means IMA will measure all
> diff --git a/security/integrity/ima/ima_policy.c
> b/security/integrity/ima/ima_policy.c
> index 7486d09a3f60..37ca16a9e65f 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 __initdata;
> 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();
> }
>
> --
> 2.17.1
>
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