[PATCH secure-modules 11/13] efi: Disable secure boot if shim is in insecure mode

[Josh Boyer]

>From b1604407fff69b17b598af03888a9efda0d58f2b Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer at redhat.com>
Date: Tue, 5 Feb 2013 19:25:05 -0500
Subject: [PATCH 11/13] efi: Disable secure boot if shim is in insecure mode

A user can manually tell the shim boot loader to disable validation of
images it loads.  When a user does this, it creates a UEFI variable called
MokSBState that does not have the runtime attribute set.  Given that the
user explicitly disabled validation, we can honor that and not enable
secure boot mode if that variable is set.

Signed-off-by: Josh Boyer <jwboyer at redhat.com>
---
 arch/x86/boot/compressed/eboot.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 145294d..545d4a6 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -863,8 +863,9 @@ fail:
 
 static int get_secure_boot(efi_system_table_t *_table)
 {
-	u8 sb, setup;
+	u8 sb, setup, moksbstate;
 	unsigned long datasize = sizeof(sb);
+	u32 attr;
 	efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
 	efi_status_t status;
 
@@ -888,6 +889,23 @@ static int get_secure_boot(efi_system_table_t *_table)
 	if (setup == 1)
 		return 0;
 
+	/* See if a user has put shim into insecure_mode.  If so, and the variable
+	 * doesn't have the runtime attribute set, we might as well honor that.
+	 */
+	var_guid = EFI_SHIM_LOCK_GUID;
+	status = efi_call_phys5(sys_table->runtime->get_variable,
+				L"MokSBState", &var_guid, &attr, &datasize,
+				&moksbstate);
+
+	/* If it fails, we don't care why.  Default to secure */
+	if (status != EFI_SUCCESS)
+		return 1;
+
+	if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS)) {
+		if (moksbstate == 1)
+			return 0;
+	}
+
 	return 1;
 }
 
-- 
1.8.3.1