linux-kernel - [PATCH 09/18] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode

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Date:	Thu, 22 Aug 2013 19:01:48 +0800
From:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-crypto@...r.kernel.org,
	opensuse-kernel@...nsuse.org, David Howells <dhowells@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	James Bottomley <james.bottomley@...senpartnership.com>,
	Greg KH <gregkh@...uxfoundation.org>, JKosina@...e.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Gary Lin <GLin@...e.com>, Vivek Goyal <vgoyal@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: [PATCH 09/18] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode

From: Josh Boyer <jwboyer@...hat.com>

This forcibly drops CAP_COMPROMISE_KERNEL from both cap_permitted and cap_bset
in the init_cred struct, which everything else inherits from.  This works on
any machine and can be used to develop even if the box doesn't have UEFI.

Signed-off-by: Josh Boyer <jwboyer@...hat.com>
Acked-by: Lee, Chun-Yi <jlee@...e.com>
Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
---
 Documentation/kernel-parameters.txt |    7 +++++++
 kernel/cred.c                       |   17 +++++++++++++++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 15356ac..6ad8292 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2784,6 +2784,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Note: increases power consumption, thus should only be
 			enabled if running jitter sensitive (HPC/RT) workloads.
 
+	secureboot_enable=
+			[KNL] Enables an emulated UEFI Secure Boot mode.  This
+			locks down various aspects of the kernel guarded by the
+			CAP_COMPROMISE_KERNEL capability.  This includes things
+			like /dev/mem, IO port access, and other areas.  It can
+			be used on non-UEFI machines for testing purposes.
+
 	security=	[SECURITY] Choose a security module to enable at boot.
 			If this boot parameter is not specified, only the first
 			security module asking for security registration will be
diff --git a/kernel/cred.c b/kernel/cred.c
index e0573a4..c3f4e3e 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -565,6 +565,23 @@ void __init cred_init(void)
 				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 }
 
+void __init secureboot_enable()
+{
+	pr_info("Secure boot enabled\n");
+	cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL);
+	cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL);
+}
+
+/* Dummy Secure Boot enable option to fake out UEFI SB=1 */
+static int __init secureboot_enable_opt(char *str)
+{
+	int sb_enable = !!simple_strtol(str, NULL, 0);
+	if (sb_enable)
+		secureboot_enable();
+	return 1;
+}
+__setup("secureboot_enable=", secureboot_enable_opt);
+
 /**
  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
  * @daemon: A userspace daemon to be used as a reference
-- 
1.6.4.2

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