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>

diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
index f290f78c3f3012976a15d507cd26f195230a7fd0..08b6d12f99b4fd7abcff197dada5c448569a0f1c 100644 (file)
--- 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)