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IMA: define a builtin critical data measurement policy

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Define a new critical data builtin policy to allow measuring
early kernel integrity critical data before a custom IMA policy
is loaded.

Update the documentation on kernel parameters to document
the new critical data builtin policy.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Lakshmi Ramasubramanian 2021-01-07 20:07:07 -08:00 committed by Mimi Zohar
parent 9f5d7d23cc
commit 03cee16836
2 changed files with 16 additions and 1 deletions
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5
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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

12
security/integrity/ima/ima_policy.c
View File

@ -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
@ -871,6 +878,11 @@ 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();
}