From 92ad19559ea9a8ec6f158480934ae26ebfe2c14f Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
Date: Sat, 18 Dec 2021 10:09:05 +0800
Subject: integrity: Do not load MOK and MOKx when secure boot be disabled

The security of Machine Owner Key (MOK) relies on secure boot. When
secure boot is disabled, EFI firmware will not verify binary code. Then
arbitrary efi binary code can modify MOK when rebooting.

This patch prevents MOK/MOKx be loaded when secure boot be disabled.

Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/platform_certs/load_uefi.c | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'security/integrity')

diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
index f290f78c3f30..08b6d12f99b4 100644
--- a/security/integrity/platform_certs/load_uefi.c
+++ b/security/integrity/platform_certs/load_uefi.c
@@ -6,6 +6,7 @@
 #include <linux/err.h>
 #include <linux/efi.h>
 #include <linux/slab.h>
+#include <linux/ima.h>
 #include <keys/asymmetric-type.h>
 #include <keys/system_keyring.h>
 #include "../integrity.h"
@@ -176,6 +177,10 @@ static int __init load_uefi_certs(void)
 		kfree(dbx);
 	}
 
+	/* the MOK/MOKx can not be trusted when secure boot is disabled */
+	if (!arch_ima_get_secureboot())
+		return 0;
+
 	mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
 	if (!mokx) {
 		if (status == EFI_NOT_FOUND)
-- 
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