kernel/efi-Disable-secure-boot-if-shim-is-in-insecure-mode.patch

From a04f786b6799ace9a7d42631abc4daf3d8e3bd89 Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Tue, 5 Feb 2013 19:25:05 -0500
Subject: [PATCH] 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@fedoraproject.org>
---
 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 88edd48f03e9..3b18ef2b534c 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -806,8 +806,9 @@ out:
 
 static int get_secure_boot(void)
 {
-	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;
 
@@ -831,6 +832,23 @@ static int get_secure_boot(void)
 	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_early->call((unsigned long)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;
 }
 
-- 
1.9.3