linux-kernel - [PATCH] integrity: Do not load MOK and MOKx when secure boot be disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20211218020905.7187-1-jlee@suse.com>
Date:   Sat, 18 Dec 2021 10:09:05 +0800
From:   "Lee, Chun-Yi" <joeyli.kernel@...il.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, James Morris <jmorris@...ei.org>
Cc:     Eric Snowberg <eric.snowberg@...cle.com>,
        David Howells <dhowells@...hat.com>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, "Lee, Chun-Yi" <jlee@...e.com>
Subject: [PATCH] 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@...e.com>
---
 security/integrity/platform_certs/load_uefi.c | 5 +++++
 1 file changed, 5 insertions(+)

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)
-- 
2.26.2