linux-kernel - [PATCH v7 7/8] IMA: define a builtin critical data measurement policy

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Message-Id: <20201209194212.5131-8-tusharsu@linux.microsoft.com>
Date:   Wed,  9 Dec 2020 11:42:11 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     zohar@...ux.ibm.com, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com, paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: [PATCH v7 7/8] IMA: define a builtin critical data measurement policy

From: Lakshmi Ramasubramanian <nramas@...ux.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 <nramas@...ux.microsoft.com>
---
 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