[RFC PATCH] ima: require secure_boot rules in lockdown mode

[David Howells]

I've made the revisions suggested.  See the attached patch.

David
---
commit 721c0994b824b91acd3c412abe55ae41287fc64d
Author: Mimi Zohar <zohar at linux.vnet.ibm.com>
Date:   Mon Oct 23 11:59:47 2017 -0400

    ima: require secure_boot rules in lockdown mode
    
    Require the "secure_boot" rules, whether or not it is specified
    on the boot command line, for both the builtin and custom policies
    in secure boot lockdown mode.
    
    Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
    Signed-off-by: David Howells <dhowells at redhat.com>

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 95209a5f8595..f64f2be2dc0c 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -427,14 +427,21 @@ void ima_update_policy_flag(void)
  */
 void __init ima_init_policy(void)
 {
-	int i, measure_entries, appraise_entries, secure_boot_entries;
+	int i;
+	int measure_entries = 0;
+	int appraise_entries = 0;
+	int secure_boot_entries = 0;
+	bool kernel_locked_down = kernel_is_locked_down();
 
 	/* if !ima_policy set entries = 0 so we load NO default rules */
-	measure_entries = ima_policy ? ARRAY_SIZE(dont_measure_rules) : 0;
-	appraise_entries = ima_use_appraise_tcb ?
-			 ARRAY_SIZE(default_appraise_rules) : 0;
-	secure_boot_entries = ima_use_secure_boot ?
-			ARRAY_SIZE(secure_boot_rules) : 0;
+	if (ima_policy)
+		measure_entries = ARRAY_SIZE(dont_measure_rules);
+
+	if (ima_use_appraise_tcb)
+		appraise_entries = ARRAY_SIZE(default_appraise_rules);
+
+	if (ima_use_secure_boot || kernel_locked_down)
+		secure_boot_entries = ARRAY_SIZE(secure_boot_rules);
 
 	for (i = 0; i < measure_entries; i++)
 		list_add_tail(&dont_measure_rules[i].list, &ima_default_rules);
@@ -455,11 +462,23 @@ void __init ima_init_policy(void)
 
 	/*
 	 * Insert the appraise rules requiring file signatures, prior to
-	 * any other appraise rules.
+	 * any other appraise rules.  In secure boot lock-down mode, also
+	 * require these appraise rules for custom policies.
 	 */
-	for (i = 0; i < secure_boot_entries; i++)
-		list_add_tail(&secure_boot_rules[i].list,
-			      &ima_default_rules);
+	for (i = 0; i < secure_boot_entries; i++) {
+		struct ima_rule_entry *entry;
+
+		/* Include for builtin policies */
+		list_add_tail(&secure_boot_rules[i].list, &ima_default_rules);
+
+		/* Include for custom policies */
+		if (kernel_locked_down) {
+			entry = kmemdup(&secure_boot_rules[i], sizeof(*entry),
+					GFP_KERNEL);
+			if (entry)
+				list_add_tail(&entry->list, &ima_policy_rules);
+		}
+	}
 
 	for (i = 0; i < appraise_entries; i++) {
 		list_add_tail(&default_appraise_rules[i].list,
--
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