linux-kernel - [PATCH V3 07/10] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode

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Message-ID: <20120925130818.GE18546@hansolo.jdub.homelinux.org>
Date:	Tue, 25 Sep 2012 09:08:18 -0400
From:	Josh Boyer <jwboyer@...hat.com>
To:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Matthew Garrett <mjg@...hat.com>
Subject: [PATCH V3 07/10] Secure boot: Add a dummy kernel parameter that will
 switch on Secure Boot mode

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>
---
 Documentation/kernel-parameters.txt |  7 +++++++
 kernel/cred.c                       | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9b2b8d3..93978d5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2562,6 +2562,13 @@ 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 de728ac..7e6e83f 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -623,6 +623,23 @@ 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
-- 
1.7.11.4

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