Re: [PATCH 5/7] efi: Get the secure boot status [ver #3]

From: David Howells <dhowells@redhat.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: dhowells@redhat.com,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	Lukas Wunner <lukas@wunner.de>,
	keyrings@vger.kernel.org,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 5/7] efi: Get the secure boot status [ver #3]
Date: Fri, 25 Nov 2016 13:00:55 +0000	[thread overview]
Message-ID: <31374.1480078855@warthog.procyon.org.uk> (raw)
In-Reply-To: <CAKv+Gu9c-C2uXZ0fVatCM8ffXJZDgjBcDb_T0nsFecGqgrF11Q@mail.gmail.com>

Okay, how about the attached?

Can these variables every be anything other than 1 or 0?  E.g. should the
check on SetupMode be that it isn't 0 rather than it is 1?

David
---
commit 6d4bb08e376045e27706c2740c0fdff0a6ec43f7
Author: David Howells <dhowells@redhat.com>
Date:   Fri Nov 25 11:52:05 2016 +0000

    efi: Handle secure boot from UEFI-2.6
    
    UEFI-2.6 adds a new variable, DeployedMode.  If it exists, this must be 1
    if we're to engage lockdown mode.
    
    Reported-by: James Bottomley <James.Bottomley@HansenPartnership.com>
    Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
index ca643eba5a4b..157782d1c552 100644
--- a/drivers/firmware/efi/libstub/secureboot.c
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -22,6 +22,9 @@ static const efi_char16_t const efi_SecureBoot_name[] = {
 static const efi_char16_t const efi_SetupMode_name[] = {
 	'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
 };
+static const efi_char16_t const efi_DeployedMode_name[] = {
+	'D', 'e', 'p', 'l', 'o', 'y', 'e', 'd', 'M', 'o', 'd', 'e', 0
+};
 
 /* SHIM variables */
 static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
@@ -62,6 +65,17 @@ int efi_get_secureboot(efi_system_table_t *sys_table_arg)
 	if (val == 1)
 		return 0;
 
+	/* UEFI-2.6 requires DeployedMode to be 1. */
+	if (sys_table_arg->hdr.revision == EFI_2_60_SYSTEM_TABLE_REVISION) {
+		status = get_efi_var(efi_DeployedMode_name, &efi_variable_guid,
+				     NULL, &size, &val);
+		if (status != EFI_SUCCESS)
+			goto out_efi_err;
+
+		if (val != 1)
+			return 0;
+	}
+
 	/* See if a user has put shim into insecure mode.  If so, and if the
 	 * variable doesn't have the runtime attribute set, we might as well
 	 * honor that.
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 333d31bf55bf..563abb37f03f 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -645,6 +645,10 @@ typedef struct {
 
 #define EFI_SYSTEM_TABLE_SIGNATURE ((u64)0x5453595320494249ULL)
 
+#define EFI_2_60_SYSTEM_TABLE_REVISION  ((2 << 16) | (60))
+#define EFI_2_50_SYSTEM_TABLE_REVISION  ((2 << 16) | (50))
+#define EFI_2_40_SYSTEM_TABLE_REVISION  ((2 << 16) | (40))
+#define EFI_2_31_SYSTEM_TABLE_REVISION  ((2 << 16) | (31))
 #define EFI_2_30_SYSTEM_TABLE_REVISION  ((2 << 16) | (30))
 #define EFI_2_20_SYSTEM_TABLE_REVISION  ((2 << 16) | (20))
 #define EFI_2_10_SYSTEM_TABLE_REVISION  ((2 << 16) | (10))
