From patchwork Tue Aug 20 00:17:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11102369 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C905A1395 for ; Tue, 20 Aug 2019 00:18:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9EC9222CE8 for ; Tue, 20 Aug 2019 00:18:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LlqGJcsH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728872AbfHTASR (ORCPT ); Mon, 19 Aug 2019 20:18:17 -0400 Received: from mail-vs1-f73.google.com ([209.85.217.73]:37714 "EHLO mail-vs1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728810AbfHTASQ (ORCPT ); Mon, 19 Aug 2019 20:18:16 -0400 Received: by mail-vs1-f73.google.com with SMTP id r17so1392294vsp.4 for ; Mon, 19 Aug 2019 17:18:16 -0700 (PDT) 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=5YPIjXjcyEp11sfZB0ez9FVAI8/V2zY6x+YQLUd2pLU=; b=LlqGJcsHZG0rAhwIjpYeUnvxxoeUAmfOZOt+nqa6LavnvGsUgHr+vl9op71Xg7XcL4 Aq5jGY8Pid90CkBr6npGC4H4YCMmTaDuhafRm1OhvmyNT+ai3pqE1zTJrhbr2CrofeaH GqFg3T0f+5N/J6GDp74sm4b4x5Kv58SKyoGdscTTQjVU/UeISpXH8GrD4xBoTavKg5Cc YnBzdR0WnIO4F5OHZsrMjaCkv5B/TJvNRfNoGRRdH2P4LtBCtTgmDfc7mES4vhvRxftf dlV9Pa09Z5/KaWa4cco+Rh7Q8KmHeKbHpsK42Q4pZbypI+xwmiYi5QknBZHMMYDj3gwV iK4g== 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=5YPIjXjcyEp11sfZB0ez9FVAI8/V2zY6x+YQLUd2pLU=; b=NGAaXyzJugNTrUc5WcftAPo7qhD2Uyhq/ZwHjHF+ak/pJDZBI5XiG4Huywatc9o/1G XtTc8q6NnKseSU6KyNROeZjty7SWzdjM1ihFBtK4Ot1EI/TQjNLGiG/QCA4n1PeJIrG5 0Q+hm7+EzgYjzsoICwe1B0Pfzz+8N16iMVisb4czMwXd/8pHj/zMgLn43SbTU+5PGiZI Bz0nOVboEITmuLclR+JA9/UqWnbnzAXVsgVCe1q7hZoJX26PtLhDXAAKNAs1e0iiAaud YWKpxdNq5Nu8XnmDq7ziyvQcPNRjr1bKRWbvMG2KiCkZhtGXyqCzwFNOnCNW/XGjv8dy xlWA== X-Gm-Message-State: APjAAAUoD2snHZZHs3GcWLrZSQAKCxEsMhQHLetsDhHPtSUXr8QEc5lu bLMICXsJ+U0sHfhm6/+IDT5BU0+7MN2PpsZ8zLzkgg== X-Google-Smtp-Source: APXvYqwDYnisDv+ixr6874+eJXMW4bVLtplZnZtow9TjHzzaCTwGHu/cXUBpz5qOOOksc7+5hHjiMZD3wHetsHlwBczTFg== X-Received: by 2002:ab0:32d8:: with SMTP id f24mr8933854uao.121.1566260295200; Mon, 19 Aug 2019 17:18:15 -0700 (PDT) Date: Mon, 19 Aug 2019 17:17:38 -0700 In-Reply-To: <20190820001805.241928-1-matthewgarrett@google.com> Message-Id: <20190820001805.241928-3-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190820001805.241928-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.23.0.rc1.153.gdeed80330f-goog Subject: [PATCH V40 02/29] security: Add a "locked down" LSM hook From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , Matthew Garrett , Kees Cook , Casey Schaufler Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Add a mechanism to allow LSMs to make a policy decision around whether kernel functionality that would allow tampering with or examining the runtime state of the kernel should be permitted. Signed-off-by: Matthew Garrett Acked-by: Kees Cook Acked-by: Casey Schaufler --- include/linux/lsm_hooks.h | 7 +++++++ include/linux/security.h | 32 ++++++++++++++++++++++++++++++++ security/security.c | 6 ++++++ 3 files changed, 45 insertions(+) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index b02e8bb6654d..2f4ba9062fb8 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1446,6 +1446,11 @@ * @bpf_prog_free_security: * Clean up the security information stored inside bpf prog. * + * @locked_down + * Determine whether a kernel feature that potentially enables arbitrary + * code execution in kernel space should be permitted. + * + * @what: kernel feature being accessed */ union security_list_options { int (*binder_set_context_mgr)(struct task_struct *mgr); @@ -1807,6 +1812,7 @@ union security_list_options { int (*bpf_prog_alloc_security)(struct bpf_prog_aux *aux); void (*bpf_prog_free_security)(struct bpf_prog_aux *aux); #endif /* CONFIG_BPF_SYSCALL */ + int (*locked_down)(enum lockdown_reason what); }; struct security_hook_heads { @@ -2046,6 +2052,7 @@ struct security_hook_heads { struct hlist_head bpf_prog_alloc_security; struct hlist_head bpf_prog_free_security; #endif /* CONFIG_BPF_SYSCALL */ + struct hlist_head locked_down; } __randomize_layout; /* diff --git a/include/linux/security.h b/include/linux/security.h index c5dd90981c98..04cf48fab15d 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -77,6 +77,33 @@ enum lsm_event { LSM_POLICY_CHANGE, }; +/* + * These are reasons that can be passed to the security_locked_down() + * LSM hook. Lockdown reasons that protect kernel integrity (ie, the + * ability for userland to modify kernel code) are placed before + * LOCKDOWN_INTEGRITY_MAX. Lockdown reasons that protect kernel + * confidentiality (ie, the ability for userland to extract + * information from the running kernel that would otherwise be + * restricted) are placed before LOCKDOWN_CONFIDENTIALITY_MAX. + * + * LSM authors should note that the semantics of any given lockdown + * reason are not guaranteed to be stable - the same reason may block + * one set of features in one kernel release, and a slightly different + * set of features in a later kernel release. LSMs that seek to expose + * lockdown policy at any level of granularity other than "none", + * "integrity" or "confidentiality" are responsible for either + * ensuring that they expose a consistent level of functionality to + * userland, or ensuring that userland is aware that this is + * potentially a moving target. It is easy to misuse this information + * in a way that could break userspace. Please be careful not to do + * so. + */ +enum lockdown_reason { + LOCKDOWN_NONE, + LOCKDOWN_INTEGRITY_MAX, + LOCKDOWN_CONFIDENTIALITY_MAX, +}; + /* These functions are in security/commoncap.c */ extern int cap_capable(const struct cred *cred, struct user_namespace *ns, int cap, unsigned int opts); @@ -393,6 +420,7 @@ void security_inode_invalidate_secctx(struct inode *inode); int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen); int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen); int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen); +int security_locked_down(enum lockdown_reason what); #else /* CONFIG_SECURITY */ static inline int call_lsm_notifier(enum lsm_event event, void *data) @@ -1210,6 +1238,10 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32 { return -EOPNOTSUPP; } +static inline int security_locked_down(enum lockdown_reason what) +{ + return 0; +} #endif /* CONFIG_SECURITY */ #ifdef CONFIG_SECURITY_NETWORK diff --git a/security/security.c b/security/security.c index ef4a0111c8b4..7fc373486d7a 100644 --- a/security/security.c +++ b/security/security.c @@ -2389,3 +2389,9 @@ void security_bpf_prog_free(struct bpf_prog_aux *aux) call_void_hook(bpf_prog_free_security, aux); } #endif /* CONFIG_BPF_SYSCALL */ + +int security_locked_down(enum lockdown_reason what) +{ + return call_int_hook(locked_down, 0, what); +} +EXPORT_SYMBOL(security_locked_down);