On 11/6/20 7:37 AM, Lakshmi Ramasubramanian wrote:
Hi Mimi,
Hi Lakshmi, Tushar,
This patch defines a new critical_data builtin policy. Please update
the Subject line.
On Sun, 2020-11-01 at 14:26 -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. For example, SELinux calls ima_measure_critical_data() to
measure its state and policy when they are initialized. This occurs
before a custom IMA policy is loaded, and hence IMA hook will not
measure the data. A built-in policy is therefore needed to measure
critical data provided by callers 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.
I will add the above line in the patch description.
Either remove the references to SELinux or move this patch after the
subsequent patch which measures SELinux critical data.
I will remove the reference to SELinux.
I think it would be better to have this patch before the SELinux
measurement patch.
Add CRITICAL_DATA to built-in IMA rules if the kernel command line
contains "ima_policy=critical_data". Set the IMA template for this rule
to "ima-buf" since ima_measure_critical_data() measures a buffer.
Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
---
security/integrity/ima/ima_policy.c | 32 +++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/security/integrity/ima/ima_policy.c
b/security/integrity/ima/ima_policy.c
index ec99e0bb6c6f..dc8fe969d3fe 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -875,6 +884,29 @@ void __init ima_init_policy(void)
ARRAY_SIZE(default_appraise_rules),
IMA_DEFAULT_POLICY);
+ if (ima_use_critical_data) {
+ template = lookup_template_desc("ima-buf");
+ if (!template) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = template_desc_init_fields(template->fmt,
+ &(template->fields),
+ &(template->num_fields));
The default IMA template when measuring buffer data is "ima_buf". Is
there a reason for allocating and initializing it here and not
deferring it until process_buffer_measurement()?
You are right - good catch.
I will remove the above and validate.
process_buffer_measurement() allocates and initializes "ima-buf"
template only when the parameter "func" is NONE. Currently, only
ima_check_blacklist() passes NONE for func when calling
process_buffer_measurement().
If "func" is anything other than NONE, ima_match_policy() picks
the default IMA template if the IMA policy rule does not specify a template.
We need to add "ima-buf" in the built-in policy for critical_data so
that the default template is not used for buffer measurement.
Please let me know if I am missing something.
thanks,
-lakshmi
+ if (ret)
+ goto out;
+
+ critical_data_rules[0].template = template;
+ add_rules(critical_data_rules,
+ ARRAY_SIZE(critical_data_rules),
+ IMA_DEFAULT_POLICY);
+ }
+
+out:
+ if (ret)
+ pr_err("%s failed, result: %d\n", __func__, ret);
+
ima_update_policy_flag();
}
