From patchwork Thu Feb 28 23:10:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 10834223 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 68331180E for ; Thu, 28 Feb 2019 23:11:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 52D382FC3B for ; Thu, 28 Feb 2019 23:11:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4706E2FC45; Thu, 28 Feb 2019 23:11:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2CCE42FC3B for ; Thu, 28 Feb 2019 23:11:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732829AbfB1XLL (ORCPT ); Thu, 28 Feb 2019 18:11:11 -0500 Received: from mail-io1-f73.google.com ([209.85.166.73]:55514 "EHLO mail-io1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726437AbfB1XLL (ORCPT ); Thu, 28 Feb 2019 18:11:11 -0500 Received: by mail-io1-f73.google.com with SMTP id l10so16698798iob.22 for ; Thu, 28 Feb 2019 15:11:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=JgzwmpXUZt6KNQDOAKfrLdx7UP057Xc3K0KJM8I4IMs=; b=dAsLSfXKyGPDbouXPHYH7fcKODImrwXNQePsf+wCZ+qJwU7tMD1lpoJtzkrPa4pVD2 JWIHq4euZwKPAsUus5g0jCU9AOXfE4c6Lyfi58DZHmWmqnxSUmzFn5hw/jbkXCkdGJu7 HOjlUGqDfMtuSvkgY54QZtrQ/eak3eOXEAqareVRpM5GmExq4/0DRQybRuQ/NpkWeuLS NnccSbCIUpMNwLq3HnLFivAqKGS7dcMJxs5kY9lfpIbUTjVF/3xotZOGaDMiCIB4I4pi yKWhdaOtZXfiLWcDIsoJ08S1/GX5n+w5PxH2EWFt9IQ9hX0pRq+PgrMlFimdipdlLp2P ytaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=JgzwmpXUZt6KNQDOAKfrLdx7UP057Xc3K0KJM8I4IMs=; b=i3IoV1pmXC/57k63qVr5uE5s5LGtwF6hYndDhJTjneccBkU4FEclmXxrzosLt3tn+P RO412tnHCvRI+rJOC9NIW4gcWsAbnEdwyWPUsX7BWjN3v2qXoNo7t3Wm5F5ave3o8YPX lAGJe0oJi87UjlkzV09g5QmFgoC8Wif/H9fYXw9Phn5X36XCa/f4aYIl+6ChWeD3CTIl ErztOGlCk4EApO7eVUyXmsJnmrnSmgOzAL3kFNEMBtWsxLbZMPRs31GYsGNmViZHekp1 gto4V4U+koruzV759QL9XfwypR5a3LIArjXka0T7gVfP7ecq1qns8FSN7zmfBApQcHII +dTQ== X-Gm-Message-State: APjAAAVv8UdXXFlm+/5NvZOrljaVVuHfEVFuubjzHmQLIVxbjg55ckFh xg939eIsJxrg9mnAeyfVSTW59O+VJL9KgVygR5DNDw== X-Google-Smtp-Source: AHgI3IY6NNUBdt5MkW6pSZcmTm5A+kECbiKydGPISbLnqOl3M90zVJgeT7wYgwxiXGnopf7j8KJFHFZ4i5W4j5Z+Iq5XbA== X-Received: by 2002:a24:d083:: with SMTP id m125mr1455178itg.5.1551395470150; Thu, 28 Feb 2019 15:11:10 -0800 (PST) Date: Thu, 28 Feb 2019 15:10:41 -0800 In-Reply-To: Message-Id: <20190228231107.209611-1-matthewgarrett@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.21.0.352.gf09ad66450-goog Subject: [PATCH 01/27] Add the ability to lock down access to the running kernel image From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: David Howells Provide a single call to allow kernel code to determine whether the system should be locked down, thereby disallowing various accesses that might allow the running kernel image to be changed including the loading of modules that aren't validly signed with a key we recognise, fiddling with MSR registers and disallowing hibernation. Signed-off-by: David Howells Acked-by: James Morris --- include/linux/kernel.h | 17 ++++++++++++ include/linux/security.h | 9 +++++- security/Kconfig | 15 ++++++++++ security/Makefile | 3 ++ security/lock_down.c | 59 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 102 insertions(+), 1 deletion(-) create mode 100644 security/lock_down.c diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 8f0e68e250a7..833bf32ce4e6 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -340,6 +340,23 @@ static inline void refcount_error_report(struct pt_regs *regs, const char *err) { } #endif +#ifdef CONFIG_LOCK_DOWN_KERNEL +extern bool __kernel_is_locked_down(const char *what, bool first); +#else +static inline bool __kernel_is_locked_down(const char *what, bool first) +{ + return false; +} +#endif + +#define kernel_is_locked_down(what) \ + ({ \ + static bool message_given; \ + bool locked_down = __kernel_is_locked_down(what, !message_given); \ + message_given = true; \ + locked_down; \ + }) + /* Internal, do not use. */ int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res); int __must_check _kstrtol(const char *s, unsigned int base, long *res); diff --git a/include/linux/security.h b/include/linux/security.h index dbfb5a66babb..35f0be540e0b 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1793,5 +1793,12 @@ static inline void security_bpf_prog_free(struct bpf_prog_aux *aux) #endif /* CONFIG_SECURITY */ #endif /* CONFIG_BPF_SYSCALL */ -#endif /* ! __LINUX_SECURITY_H */ +#ifdef CONFIG_LOCK_DOWN_KERNEL +extern void __init init_lockdown(void); +#else +static inline void __init init_lockdown(void) +{ +} +#endif +#endif /* ! __LINUX_SECURITY_H */ diff --git a/security/Kconfig b/security/Kconfig index e4fe2f3c2c65..c2aff0006de2 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -230,6 +230,21 @@ config STATIC_USERMODEHELPER_PATH If you wish for all usermode helper programs to be disabled, specify an empty string here (i.e. ""). +config LOCK_DOWN_KERNEL + bool "Allow the kernel to be 'locked down'" + help + Allow the kernel to be locked down. If lockdown support is enabled + and activated, the kernel will impose additional restrictions + intended to prevent uid 0 from being able to modify the running + kernel. This may break userland applications that rely on low-level + access to hardware. + +config LOCK_DOWN_KERNEL_FORCE + bool "Enable kernel lockdown mode automatically" + depends on LOCK_DOWN_KERNEL + help + Enable the kernel lock down functionality automatically at boot. + source "security/selinux/Kconfig" source "security/smack/Kconfig" source "security/tomoyo/Kconfig" diff --git a/security/Makefile b/security/Makefile index 4d2d3782ddef..507ac8c520ce 100644 --- a/security/Makefile +++ b/security/Makefile @@ -30,3 +30,6 @@ obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o # Object integrity file lists subdir-$(CONFIG_INTEGRITY) += integrity obj-$(CONFIG_INTEGRITY) += integrity/ + +# Allow the kernel to be locked down +obj-$(CONFIG_LOCK_DOWN_KERNEL) += lock_down.o diff --git a/security/lock_down.c b/security/lock_down.c new file mode 100644 index 000000000000..13a8228c1034 --- /dev/null +++ b/security/lock_down.c @@ -0,0 +1,59 @@ +/* Lock down the kernel + * + * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include + +static __ro_after_init bool kernel_locked_down; + +/* + * Put the kernel into lock-down mode. + */ +static void __init lock_kernel_down(const char *where) +{ + if (!kernel_locked_down) { + kernel_locked_down = true; + pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", + where); + } +} + +static int __init lockdown_param(char *ignored) +{ + lock_kernel_down("command line"); + return 0; +} + +early_param("lockdown", lockdown_param); + +/* + * Lock the kernel down from very early in the arch setup. This must happen + * prior to things like ACPI being initialised. + */ +void __init init_lockdown(void) +{ +#ifdef CONFIG_LOCK_DOWN_FORCE + lock_kernel_down("Kernel configuration"); +#endif +} + +/** + * kernel_is_locked_down - Find out if the kernel is locked down + * @what: Tag to use in notice generated if lockdown is in effect + */ +bool __kernel_is_locked_down(const char *what, bool first) +{ + if (what && first && kernel_locked_down) + pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", + what); + return kernel_locked_down; +} +EXPORT_SYMBOL(__kernel_is_locked_down);