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.
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
@@ -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;
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
@@ -813,6 +820,8 @@ static int __init ima_init_arch_policy(void)
void __init ima_init_policy(void)
{
int build_appraise_entries, arch_entries;
+ struct ima_template_desc *template = NULL;
+ int ret = 0;
/* if !ima_policy, we load NO default rules */
if (ima_policy)
@@ -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));
+ 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();
}
--
2.17.1
--
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