Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753020AbcLGNSw (ORCPT ); Wed, 7 Dec 2016 08:18:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49986 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752968AbcLGNSu (ORCPT ); Wed, 7 Dec 2016 08:18:50 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 6/8] efi: Disable secure boot if shim is in insecure mode [ver #5] From: David Howells To: matt@codeblueprint.co.uk, ard.biesheuvel@linaro.org Cc: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-arm-kernel@lists.infradead.org Date: Wed, 07 Dec 2016 13:18:47 +0000 Message-ID: <148111672749.23390.3812803285687048081.stgit@warthog.procyon.org.uk> In-Reply-To: <148111668193.23390.6340512985876251017.stgit@warthog.procyon.org.uk> References: <148111668193.23390.6340512985876251017.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 07 Dec 2016 13:18:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2380 Lines: 64 From: Josh Boyer 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 Signed-off-by: David Howells --- drivers/firmware/efi/libstub/secureboot.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c index 70e2a36577d4..ba6ef717c66f 100644 --- a/drivers/firmware/efi/libstub/secureboot.c +++ b/drivers/firmware/efi/libstub/secureboot.c @@ -23,6 +23,12 @@ static const efi_char16_t const efi_SetupMode_name[] = { 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 }; +/* SHIM variables */ +static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID; +static efi_char16_t const shim_MokSBState_name[] = { + 'M', 'o', 'k', 'S', 'B', 'S', 't', 'a', 't', 'e', 0 +}; + #define get_efi_var(name, vendor, ...) \ efi_call_runtime(get_variable, \ (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ @@ -33,7 +39,8 @@ static const efi_char16_t const efi_SetupMode_name[] = { */ enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg) { - u8 secboot, setupmode; + u32 attr; + u8 secboot, setupmode, moksbstate; unsigned long size; efi_status_t status; @@ -52,6 +59,21 @@ enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg) if (secboot == 0 || setupmode == 1) goto secure_boot_disabled; + /* 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. + */ + size = sizeof(moksbstate); + status = get_efi_var(shim_MokSBState_name, &shim_guid, + &attr, &size, &moksbstate); + + /* If it fails, we don't care why. Default to secure */ + if (status != EFI_SUCCESS) + goto secure_boot_enabled; + if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1) + goto secure_boot_disabled; + +secure_boot_enabled: pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n"); return efi_secureboot_mode_enabled;