From patchwork Fri May 21 17:24:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12273451 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C27EDC4707A for ; Fri, 21 May 2021 17:35:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95E6761168 for ; Fri, 21 May 2021 17:35:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234356AbhEURg5 (ORCPT ); Fri, 21 May 2021 13:36:57 -0400 Received: from mout.gmx.net ([212.227.15.15]:48553 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233220AbhEURg4 (ORCPT ); Fri, 21 May 2021 13:36:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621618477; bh=jYd+DBUq5/+hoWltaHEIKEySfVzGVUxKtuTlWhtWnNU=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=Kx8aLe9AKZkFlHBFzKJQ/0wO5CcwPquXKmR8TTit7BChbVKbSqFooAblS8Rf2ryz/ rem1qyVFe5OlpYpwOF7Op7yahmHVvWV0DF4yriyBrQICZBlEvZluGaW1rxMkC4ACeF ZbpwL+OavEkNMn3DVwawfQnaDwrNffx+jtc3qgfg= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from localhost.localdomain ([83.52.228.41]) by mail.gmx.net (mrgmx004 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MPGW7-1m6u3c2AHd-00PaoO; Fri, 21 May 2021 19:34:37 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 1/7] security: Add LSM hook at the point where a task gets a fatal signal Date: Fri, 21 May 2021 19:24:08 +0200 Message-Id: <20210521172414.69456-2-john.wood@gmx.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:Bd6lib84LVlkJT8jNqZAPUjNinmei+Xet/u0DD1+cHkiKEm3feF HT9bCqV7iIbCFUzz/JKgZCFWJOJMWDiXaJlKsCIUC2k7end9vd+XP1uID+wLCkVzUwFhr3+ y+v3JS+c2GJC76pLYtnMrj7kZuxHwGgbttcFMRFUIpuNjaUpqH29kG7NGc4ZZ7OlrjLEP2R vHsgogfOcVJBKVmcoBkTQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:6IzlPLp9f6s=:mRCsH7AFbIQl1g7NxLFy2S RL3o1/lFuK9b4P0IYPqitza5mnxG0OhhsvQaeBsmwlhRDQo8uuYJ9Ag2sTZilVX4aMwiqkZKV 7UMoe4qaCcWKByzEk5LMdt/K2wS1P82N1MEJOKeONkrwQpXX1EUsLASFlmF0D39p9DpidEkna xEKYNdtU8pDVUWfidjveb5cFVlQk4qZq7MjnXfUkSCsNAC570amFjHEn3Nt6OLIUZgu/nOcoN kHcU3m10GpTHZhMz1tV7YVmb+yUS07ItIUJJkb01F+AFI3b+T1+WCbBOsXwklBZ882GuKccCD jOp66XHdJp7r/A3D6eoVqscOtQ3g/3bjtmSFtC4vUwfwtnKSprS7IeJ3kBS+5DrGL8EYRdGPy FMpUNTomkI+frPzJpZGhFzA+EghsWzinnk/7yg8y0O0xRQq7GtRNyeSiSfuchH+2bhl73rW5o ddlbm+jTdO06FpRiz44lOl8AxVI+CzisvNSgP9JSc5bfN4gkldOt3EisIjVElbl2Wg3Emmwiy OH3uqW55FfrIN2xawGSyF8feR/0ZRDG653I3R1+gkgI24NO7imkyMoHX7KUeXzbtzGjGFaSYL T1txig1UyxtAoAA4PZDr02bv+yRMOCWyPU2eGn0o8552XIggIDelLtp3OwWPr9Xdb7XX9Qtd/ +59rwgB8cHWLeqiWC1/JjrE8HuLHeroUswRaSgbdA9TN0gMjT28fs2LJyixM/zVjJr3hSD8cA 92MxppbEOkiBA7m9gd1roANZ9z4UU2s4bMFcaUMucc2cSrXgKb9woSGT3PJfMH+VL+1nMHNWw bUbkZB8mNO1y1B5oe4k5X9DT7YB0C/gYeadDtY3kMUKCbfV/JrUbwD6N3pFkapfrxWiGspnWn me+rNqShm2CHXkzEpS+sKguOFLpQ2hZVXMVoMN46zZfZgfABx7E2QCUY1hnjt4MjUsdifT+9y 4HIyw/uyCZLCXun7J6Al3257WGQcMCkXhJg02qkrc1efWfd7SKOYzsZN8tZv8O5QFdxddV/Ag sM/b744VAcGw3oNEsDGLatxlxMfibejfCFQwGmEtA5ivPc3/iUogkT+HKa6l/sXLfDDcPQats zFvgx2bD9eQqxjlz5+xAJ7g1gdauvaF9EECxUmckN5umXE5j+Q+G03dIBswKFxR9EiS5mOYdN iGJW7jRzXHgB+wjp0BT89AxY6aDhp+eLQWsGteid+QEzBgLFF6aWsvY06kSq879vhyY/w= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add a security hook that allows a LSM to be notified when a task gets a fatal signal. This patch is a previous step on the way to compute the task crash period by the "brute" LSM (linux security module to detect and mitigate fork brute force attack against vulnerable userspace processes). Signed-off-by: John Wood Reviewed-by: Kees Cook --- include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 4 ++++ include/linux/security.h | 4 ++++ kernel/signal.c | 1 + security/security.c | 5 +++++ 5 files changed, 15 insertions(+) -- 2.25.1 diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 04c01794de83..e28468e84300 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -225,6 +225,7 @@ LSM_HOOK(int, -ENOSYS, task_prctl, int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) LSM_HOOK(void, LSM_RET_VOID, task_to_inode, struct task_struct *p, struct inode *inode) +LSM_HOOK(void, LSM_RET_VOID, task_fatal_signal, const kernel_siginfo_t *siginfo) LSM_HOOK(int, 0, ipc_permission, struct kern_ipc_perm *ipcp, short flag) LSM_HOOK(void, LSM_RET_VOID, ipc_getsecid, struct kern_ipc_perm *ipcp, u32 *secid) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 5c4c5c0602cb..fc8bef0f15d9 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -799,6 +799,10 @@ * security attributes, e.g. for /proc/pid inodes. * @p contains the task_struct for the task. * @inode contains the inode structure for the inode. + * @task_fatal_signal: + * This hook allows security modules to be notified when a task gets a + * fatal signal. + * @siginfo contains the signal information. * * Security hooks for Netlink messaging. * diff --git a/include/linux/security.h b/include/linux/security.h index 06f7c50ce77f..609c76c6c764 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -433,6 +433,7 @@ int security_task_kill(struct task_struct *p, struct kernel_siginfo *info, int security_task_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5); void security_task_to_inode(struct task_struct *p, struct inode *inode); +void security_task_fatal_signal(const kernel_siginfo_t *siginfo); int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag); void security_ipc_getsecid(struct kern_ipc_perm *ipcp, u32 *secid); int security_msg_msg_alloc(struct msg_msg *msg); @@ -1183,6 +1184,9 @@ static inline int security_task_prctl(int option, unsigned long arg2, static inline void security_task_to_inode(struct task_struct *p, struct inode *inode) { } +static inline void security_task_fatal_signal(const kernel_siginfo_t *siginfo) +{ } + static inline int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag) { diff --git a/kernel/signal.c b/kernel/signal.c index 66e88649cf74..62625ad98b14 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2787,6 +2787,7 @@ bool get_signal(struct ksignal *ksig) /* * Anything else is fatal, maybe with a core dump. */ + security_task_fatal_signal(&ksig->info); current->flags |= PF_SIGNALED; if (sig_kernel_coredump(signr)) { diff --git a/security/security.c b/security/security.c index b38155b2de83..208e3e7d4284 100644 --- a/security/security.c +++ b/security/security.c @@ -1891,6 +1891,11 @@ void security_task_to_inode(struct task_struct *p, struct inode *inode) call_void_hook(task_to_inode, p, inode); } +void security_task_fatal_signal(const kernel_siginfo_t *siginfo) +{ + call_void_hook(task_fatal_signal, siginfo); +} + int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag) { return call_int_hook(ipc_permission, 0, ipcp, flag); From patchwork Fri May 21 17:24:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12273463 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 590B2C47076 for ; 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Fri, 21 May 2021 19:44:41 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 2/7] security/brute: Define a LSM and add sysctl attributes Date: Fri, 21 May 2021 19:24:09 +0200 Message-Id: <20210521172414.69456-3-john.wood@gmx.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:dHBeZqKBH5p0TcaXbrstKdGyyd/PDgfJ4pllDUkxJomNf1zrhQS wEwmAdIcTPVCLq5r85oIJzyvZiXhzvdfFQG6rQcpAFsqkKAY65ukfTL0amIk33gCswxD7uo HFgOO0hlvXZSXkvcwhrKixek/fZE9+DKCifW73SO6lE1X/1HVhCDhXag/9axuiYVrzaSlj8 ZxeGZMHpJqbnVUpk+pnug== X-UI-Out-Filterresults: notjunk:1;V03:K0:SLwDhqiwQPo=:NncsFwf/hAeSlE45N0sg2O 2sgmkBoIdegPQSagAZCIIqH4k1dy8NMENnN9xJ5p+GOH9fNPmb3xK7qqEIgHthB5MjsW7FZHy WZVTU5vUSjz5IXaKfkYEROf9HsXHw3mHXVYcnkE9I1FFH5Sx7eAydmN1irjeNETQOeSIl6r/K tGJEHRnRmvySjBPocVh8FVhplTrkEpaLGcDv9YQ8ZKKVkoTOH18svj3voUR/rW5Xo15Fx+ThO ipqy9lljKXtzSML6cu4Av2+o5WDwTuOOlDhY6xd0uJ2+iW17GNHU21JDBnBNenzNO3OPTE53y OZpAmARmh87jlYPjtTR98jJGQaZZ1ZwzXxe7bT1IwZTZHCGWxmuiOQzfJY9qIsfaAgKcmTtYz nH6Bh6DZSn+E6NloAHsaADCks3Zl7GxyXNjl/+V7QeSUqr3WMPqy4i2nimZd3ijCSrcmZH6Fv Wwf5C7pXwhPB3yp10fKJp/piPSG5R7uDAshAC90YlVpzMz4Iu6XUNzIkCiVZXwnxg0+YBYzsU tz2PMqoNaZcdy4ZfVqPunp8XdHL4XCQXCxsMbZuYFMOV4PV8uq6fzgiELuUOSrkb1uqI403RI WioE8j5YvDgnQcXIgIoPyAgP2gZi6/QeMhvwsy4jWOFBh9T67qnUtUVQSVyGbqz+evpUZx7eB h++SehlSLLTtJKY8o8ieE+HuKNRJgszIuxUB+QoSJN9GaIE6JHyULZW4zksGJlHI0yJ8X7Qg7 zpL69bUZAMZPklsyqwUcLG8XL9O9mcRYIVsL7w7JlwWYTHOsLKoYYvgxv85QR3+nRfD+ZdOUg GY7q51YX24Q853NfkMiRtFiG3SYJT+X7ON41mimP3MDtckeXG81cgh6ESVbww0SIL/0HcIzuG DAZTtPPnca1of3cMilIrRhYmo1lGbhsFlvAzxjZRIau6BPQksMSyjBbt87vYSv59WBAjYcfZ7 tq/XP/v9z0p+A35FbLgdVxmta+w7c9glpZCN98EHEBeP0dTtmjcVGxe6aapvKGZYuq70VxNXG uLPLGyKLOSuyA3bucSookEaQlKYfheQKkiy9XSIsOgfFHK3paIFo4w9BpRE36RrHlh7MJ4Awj JWthOKHZSKOCkUdqqo7IVcSuC9MAixs4XV+ Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add a new Kconfig file to define a menu entry under "Security options" to enable the "Fork brute force attack detection and mitigation" feature. The detection of a brute force attack can be based on the number of faults per application and its crash rate. There are two types of brute force attacks that can be detected. The first one is a slow brute force attack that is detected if the maximum number of faults per fork hierarchy is reached. The second type is a fast brute force attack that is detected if the application crash period falls below a certain threshold. The application crash period must be a value that is not prone to change due to spurious data and follows the real crash period. So, to compute it, the exponential moving average (EMA) will be used. This kind of average defines a weight (between 0 and 1) for the new value to add and applies the remainder of the weight to the current average value. This way, some spurious data will not excessively modify the average and only if the new values are persistent, the moving average will tend towards them. Mathematically the application crash period's EMA can be expressed as follows: period_ema = period * weight + period_ema * (1 - weight) Moreover, it is important to note that a minimum number of faults is needed to guarantee a trend in the crash period when the EMA is used. So, based on all the previous information define a LSM with five sysctl attributes that will be used to fine tune the attack detection. ema_weight_numerator ema_weight_denominator max_faults min_faults crash_period_threshold This patch is a previous step on the way to fine tune the attack detection. Signed-off-by: John Wood --- security/Kconfig | 11 +-- security/Makefile | 2 + security/brute/Kconfig | 14 ++++ security/brute/Makefile | 2 + security/brute/brute.c | 147 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 171 insertions(+), 5 deletions(-) create mode 100644 security/brute/Kconfig create mode 100644 security/brute/Makefile create mode 100644 security/brute/brute.c -- 2.25.1 diff --git a/security/Kconfig b/security/Kconfig index 0ced7fd33e4d..2df1727f2c2c 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -241,6 +241,7 @@ source "security/lockdown/Kconfig" source "security/landlock/Kconfig" source "security/integrity/Kconfig" +source "security/brute/Kconfig" choice prompt "First legacy 'major LSM' to be initialized" @@ -278,11 +279,11 @@ endchoice config LSM string "Ordered list of enabled LSMs" - default "landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK - default "landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR - default "landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO - default "landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC - default "landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf" + default "landlock,lockdown,brute,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK + default "landlock,lockdown,brute,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR + default "landlock,lockdown,brute,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO + default "landlock,lockdown,brute,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC + default "landlock,lockdown,brute,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf" help A comma-separated list of LSMs, in initialization order. Any LSMs left off this list will be ignored. This can be diff --git a/security/Makefile b/security/Makefile index 47e432900e24..94d325256413 100644 --- a/security/Makefile +++ b/security/Makefile @@ -14,6 +14,7 @@ subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown subdir-$(CONFIG_BPF_LSM) += bpf subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock +subdir-$(CONFIG_SECURITY_FORK_BRUTE) += brute # always enable default capabilities obj-y += commoncap.o @@ -34,6 +35,7 @@ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ obj-$(CONFIG_CGROUPS) += device_cgroup.o obj-$(CONFIG_BPF_LSM) += bpf/ obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ +obj-$(CONFIG_SECURITY_FORK_BRUTE) += brute/ # Object integrity file lists subdir-$(CONFIG_INTEGRITY) += integrity diff --git a/security/brute/Kconfig b/security/brute/Kconfig new file mode 100644 index 000000000000..5da314d221aa --- /dev/null +++ b/security/brute/Kconfig @@ -0,0 +1,14 @@ +# SPDX-License-Identifier: GPL-2.0 +config SECURITY_FORK_BRUTE + bool "Fork brute force attack detection and mitigation" + depends on SECURITY + help + This is an LSM that stops any fork brute force attack against + vulnerable userspace processes. The detection method is based on + the application crash period and as a mitigation procedure all the + offending tasks are killed. Also, the executable file involved in the + attack will be marked as "not allowed" and new execve system calls + using this file will fail. Like capabilities, this security module + stacks with other LSMs. + + If you are unsure how to answer this question, answer N. diff --git a/security/brute/Makefile b/security/brute/Makefile new file mode 100644 index 000000000000..d3f233a132a9 --- /dev/null +++ b/security/brute/Makefile @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0 +obj-$(CONFIG_SECURITY_FORK_BRUTE) += brute.o diff --git a/security/brute/brute.c b/security/brute/brute.c new file mode 100644 index 000000000000..0edb89a58ab0 --- /dev/null +++ b/security/brute/brute.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include + +/** + * DOC: brute_ema_weight_numerator + * + * Weight's numerator of EMA. + */ +static unsigned int brute_ema_weight_numerator __read_mostly = 7; + +/** + * DOC: brute_ema_weight_denominator + * + * Weight's denominator of EMA. + */ +static unsigned int brute_ema_weight_denominator __read_mostly = 10; + +/** + * DOC: brute_max_faults + * + * Maximum number of faults. + * + * If a brute force attack is running slowly for a long time, the application + * crash period's EMA is not suitable for the detection. This type of attack + * must be detected using a maximum number of faults. + */ +static unsigned int brute_max_faults __read_mostly = 200; + +/** + * DOC: brute_min_faults + * + * Minimum number of faults. + * + * The application crash period's EMA cannot be used until a minimum number of + * data has been applied to it. This constraint allows getting a trend when this + * moving average is used. + */ +static unsigned int brute_min_faults __read_mostly = 5; + +/** + * DOC: brute_crash_period_threshold + * + * Application crash period threshold. + * + * A fast brute force attack is detected when the application crash period falls + * below this threshold. The units are expressed in seconds. + */ +static unsigned int brute_crash_period_threshold __read_mostly = 30; + +#ifdef CONFIG_SYSCTL +static unsigned int uint_max = UINT_MAX; +#define SYSCTL_UINT_MAX (&uint_max) + +/* + * brute_sysctl_path - Sysctl attributes path. + */ +static struct ctl_path brute_sysctl_path[] = { + { .procname = "kernel", }, + { .procname = "brute", }, + { } +}; + +/* + * brute_sysctl_table - Sysctl attributes. + */ +static struct ctl_table brute_sysctl_table[] = { + { + .procname = "ema_weight_numerator", + .data = &brute_ema_weight_numerator, + .maxlen = sizeof(brute_ema_weight_numerator), + .mode = 0644, + .proc_handler = proc_douintvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = &brute_ema_weight_denominator, + }, + { + .procname = "ema_weight_denominator", + .data = &brute_ema_weight_denominator, + .maxlen = sizeof(brute_ema_weight_denominator), + .mode = 0644, + .proc_handler = proc_douintvec_minmax, + .extra1 = &brute_ema_weight_numerator, + .extra2 = SYSCTL_UINT_MAX, + }, + { + .procname = "max_faults", + .data = &brute_max_faults, + .maxlen = sizeof(brute_max_faults), + .mode = 0644, + .proc_handler = proc_douintvec_minmax, + .extra1 = &brute_min_faults, + .extra2 = SYSCTL_UINT_MAX, + }, + { + .procname = "min_faults", + .data = &brute_min_faults, + .maxlen = sizeof(brute_min_faults), + .mode = 0644, + .proc_handler = proc_douintvec_minmax, + .extra1 = SYSCTL_ONE, + .extra2 = &brute_max_faults, + }, + { + .procname = "crash_period_threshold", + .data = &brute_crash_period_threshold, + .maxlen = sizeof(brute_crash_period_threshold), + .mode = 0644, + .proc_handler = proc_douintvec_minmax, + .extra1 = SYSCTL_ONE, + .extra2 = SYSCTL_UINT_MAX, + }, + { } +}; + +/** + * brute_init_sysctl() - Initialize the sysctl interface. + */ +static void __init brute_init_sysctl(void) +{ + if (!register_sysctl_paths(brute_sysctl_path, brute_sysctl_table)) + panic("sysctl registration failed\n"); +} + +#else +static inline void brute_init_sysctl(void) { } +#endif /* CONFIG_SYSCTL */ + +/** + * brute_init() - Initialize the brute LSM. + * + * Return: Always returns zero. + */ +static int __init brute_init(void) +{ + pr_info("becoming mindful\n"); + brute_init_sysctl(); + return 0; +} + +DEFINE_LSM(brute) = { + .name = KBUILD_MODNAME, + .init = brute_init, +}; From patchwork Fri May 21 17:24:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12273529 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41821C4707D for ; Fri, 21 May 2021 17:55:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26E0D613D0 for ; Fri, 21 May 2021 17:55:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234848AbhEUR4j (ORCPT ); Fri, 21 May 2021 13:56:39 -0400 Received: from mout.gmx.net ([212.227.15.15]:58273 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232832AbhEUR4i (ORCPT ); Fri, 21 May 2021 13:56:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621619684; bh=+R5t0/zrJeQqbmiLiGPXh/L2XjmF15vBCZmCmoedNdQ=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=dZOuXAg6ArC9bUlxALvCZLgYilxkXAkiedJTBTwCK9QOXFL1n4i3nk3L+9btEX0vV 3l1hQ+AmJeEp97abthTQb1e5TcJkgnZ6JKGiUvSz+TvEP4zvGeDTHdo7KMDz3IS5eP C5fw8ydgZyRDv3cgmryfZru1OKM8vVMf5HQgLoD4= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from localhost.localdomain ([83.52.228.41]) by mail.gmx.net (mrgmx005 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MAfYw-1ldWZw1CGW-00B0lt; Fri, 21 May 2021 19:54:44 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 3/7] security/brute: Detect a brute force attack Date: Fri, 21 May 2021 19:24:10 +0200 Message-Id: <20210521172414.69456-4-john.wood@gmx.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:Trlmb+U40dzl+1U481ccJxduXI0CahO7IvEpRF8zPQEbf00rMl+ OSL59QXFur0Jdt8ylx7H4CUnqVdiBRCFS84xLlMi8hPpCNC+DXhtH0ZplN1ia6PpWMb7Mir FgxcNsyvbR7xmxw5p36XODq+QrWMp+6NgVxtdvJeYovkouRKUeh+R3tw1pejO0Ot3Nvo4KA TWMX5gG2sP5dA/KvdakTw== X-UI-Out-Filterresults: notjunk:1;V03:K0:+J5qzQKHjlM=:br0PCK+eIRIUvKqfjkCyQV yJlKB+H+/603ERROUYPYsVhapHnqXJKisD8tK8GHNhAtS8/rO5/aXnk6uWSrFPCtkzT3JBgVo 1a1GSBjGOeiHK521UyFHXkvEee8ulL46YBOdE0vLFEcq1VJRN0+jX5o8/e/j7YcMdnSOxk+me 0C9W8BN0QS1nJ70Tl8H/hrLflWVq7A8qYmlzxas8dqN/kd31T4VIZ9ma5MIWPVF4DUrrgM3/m delGTS56jcQL8JBbC9tyDpe6So/6m/r+ZV+xQRWBlddAvSv5ubQR4OrE4b7A0fDyQPEYHgILh ump8tuQafLfkbiypc8V4TPrYGf+Oln8rdlV5mOW/9QUlBvnTUWWTm5J2IxkTQZoQiHm/lNLCL qyt5neMlP4M2ItjToOoTIhSRn8qTt7rPR/XqmmGkDp+dPqjTJ6X7dEnfNdgrHyNIM4MQaxuJk mqC+YMmcO/mKVATalafqPinJLIv+UAsDsRlTkWjiNUd1yds9JLSTICpv9ApbnlAl+f5UdCxbX +xJ0Yi0N8pfqlj9SyqaflRQaEwirDyIjrUfNkAckBbeCifvy/w1m319WHMozjK2uugPp1Wy1x 6I/R5YkQrT6fcjhW+VucPOYzXFumNSycdd721VenlPlrPLX+WYMqQ6WgAUeCc+2GoSyKxY0qr fj6VdsHtWlJN/MLCIC6hP0qwlCAflgW5fGMYDBkJMt1eIlP5ZcRahCig8B1scDII3JiiPifBv Vp6pwELCbUSJ9bpRHVcslzR6PIEcoDN3Zy06NQGo9XGrUPw/5Y7RvLY6J/eXuYrpzd7j6EdBE acyVFhTmlg6eeZ3nsxSRQYb1sQEmWa0nBbSg8I9cU7qV2sXb7J3JIuLg+SJICv41NIC6rsM7R 45BFw1DsbTsaC1crFNoJyRxwrq8UDDkFo11Z5gqNuF2cGfkjdEPnXIOZNp3mlPd0m8sdW0W2L UCVpZ8jHWLS4ZofroYqx6S3isMQdf+F29cVaSRoaCY0YNZVFcVixdrv5xFksac58IrPY1q3ED 6iGNvls7TeDDMPpK6Vy3WehJb68bM6IEenGV9MGRCAXXNXf1IwV8qx2rXXDZTp7TU2UlGtwhs Wz+9lkqFvM5XPzvXbxOHDhuSgDroqRqtfCAXwNN25dSRaigLbCzJa/wcZsYzzOTlXgRUNcwH8 SmFYoaivoMYwcgKrgv9gL7ZaLjQYt/vSRZEEas4ii/ZGR4EHJDMryDIFGg728v7+W1POQ= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org For a correct management of a fork brute force attack it is necessary to track all the information related to the application crashes. To do so, use the extended attributes (xattr) of the executable files and define a statistical data structure to hold all the necessary information shared by all the fork hierarchy processes. This info is the number of crashes, the last crash timestamp and the crash period's moving average. The same can be achieved using a pointer to the fork hierarchy statistical data held by the task_struct structure. But this has an important drawback: a brute force attack that happens through the execve system call losts the faults info since these statistics are freed when the fork hierarchy disappears. Using this method makes not possible to manage this attack type that can be successfully treated using extended attributes. Also, to avoid false positives during the attack detection it is necessary to narrow the possible cases. So, only the following scenarios are taken into account: 1.- Launching (fork()/exec()) a setuid/setgid process repeatedly until a desirable memory layout is got (e.g. Stack Clash). 2.- Connecting to an exec()ing network daemon (e.g. xinetd) repeatedly until a desirable memory layout is got (e.g. what CTFs do for simple network service). 3.- Launching processes without exec() (e.g. Android Zygote) and exposing state to attack a sibling. 4.- Connecting to a fork()ing network daemon (e.g. apache) repeatedly until the previously shared memory layout of all the other children is exposed (e.g. kind of related to HeartBleed). In each case, a privilege boundary has been crossed: Case 1: setuid/setgid process Case 2: network to local Case 3: privilege changes Case 4: network to local To mark that a privilege boundary has been crossed it is only necessary to create a new stats for the executable file via the extended attribute and only if it has no previous statistical data. This is done using four different LSM hooks, one per privilege boundary: setuid/setgid process --> bprm_creds_from_file hook (based on secureexec flag). network to local -------> socket_accept hook (taking into account only external connections). privilege changes ------> task_fix_setuid and task_fix_setgid hooks. To detect a brute force attack it is necessary that the executable file statistics be updated in every fatal crash and the most important data to update is the application crash period. To do so, use the new "task_fatal_signal" LSM hook added in a previous step. The application crash period must be a value that is not prone to change due to spurious data and follows the real crash period. So, to compute it, the exponential moving average (EMA) is used. Based on the updated statistics two different attacks can be handled. A slow brute force attack that is detected if the maximum number of faults per fork hierarchy is reached and a fast brute force attack that is detected if the application crash period falls below a certain threshold. Moreover, only the signals delivered by the kernel are taken into account with the exception of the SIGABRT signal since the latter is used by glibc for stack canary, malloc, etc failures, which may indicate that a mitigation has been triggered. Signed-off-by: John Wood --- include/uapi/linux/xattr.h | 3 + security/brute/brute.c | 478 +++++++++++++++++++++++++++++++++++++ 2 files changed, 481 insertions(+) -- 2.25.1 diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h index 9463db2dfa9d..ce1c8497dceb 100644 --- a/include/uapi/linux/xattr.h +++ b/include/uapi/linux/xattr.h @@ -76,6 +76,9 @@ #define XATTR_CAPS_SUFFIX "capability" #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX +#define XATTR_BRUTE_SUFFIX "brute" +#define XATTR_NAME_BRUTE XATTR_SECURITY_PREFIX XATTR_BRUTE_SUFFIX + #define XATTR_POSIX_ACL_ACCESS "posix_acl_access" #define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS #define XATTR_POSIX_ACL_DEFAULT "posix_acl_default" diff --git a/security/brute/brute.c b/security/brute/brute.c index 0edb89a58ab0..66db0dd0664d 100644 --- a/security/brute/brute.c +++ b/security/brute/brute.c @@ -2,8 +2,85 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include #include #include +#include +#include +#include + +/** + * struct brute_stats - Fork brute force attack statistics. + * @faults: Number of crashes. + * @nsecs: Last crash timestamp as the number of nanoseconds in the + * International Atomic Time (TAI) reference. + * @period: Crash period's moving average. + * @flags: Statistics flags as a whole. + * @not_allowed: Not allowed executable file flag. + * @unused: Remaining unused flags. + * + * This structure holds the statistical data shared by all the fork hierarchy + * processes. + */ +struct brute_stats { + u32 faults; + u64 nsecs; + u64 period; + union { + u8 flags; + struct { + u8 not_allowed : 1; + u8 unused : 7; + }; + }; +}; + +/** + * struct brute_raw_stats - Raw fork brute force attack statistics. + * @faults: Number of crashes. + * @nsecs: Last crash timestamp as the number of nanoseconds in the + * International Atomic Time (TAI) reference. + * @period: Crash period's moving average. + * @flags: Statistics flags. + * + * This structure holds the statistical data on disk as an extended attribute. + * Since the filesystems on which extended attributes are stored might also be + * used on architectures with a different byte order and machine word size, care + * should be taken to store attribute values in an architecture-independent + * format. + */ +struct brute_raw_stats { + __le32 faults; + __le64 nsecs; + __le64 period; + u8 flags; +} __packed; + +/** + * brute_get_current_exe_file() - Get the current task's executable file. + * + * Since all the kernel threads associated with a task share the same executable + * file, get the thread group leader's executable file. + * + * Context: The file must be released via fput(). + * Return: NULL if the current task has no associated executable file. A pointer + * to the executable file otherwise. + */ +static struct file *brute_get_current_exe_file(void) +{ + struct task_struct *task = current; + struct file *exe_file; + + rcu_read_lock(); + if (!thread_group_leader(task)) + task = rcu_dereference(task->group_leader); + get_task_struct(task); + rcu_read_unlock(); + + exe_file = get_task_exe_file(task); + put_task_struct(task); + return exe_file; +} /** * DOC: brute_ema_weight_numerator @@ -19,6 +96,18 @@ static unsigned int brute_ema_weight_numerator __read_mostly = 7; */ static unsigned int brute_ema_weight_denominator __read_mostly = 10; +/** + * brute_mul_by_ema_weight() - Multiply by EMA weight. + * @value: Value to multiply by EMA weight. + * + * Return: The result of the multiplication operation. + */ +static inline u64 brute_mul_by_ema_weight(u64 value) +{ + return mul_u64_u32_div(value, brute_ema_weight_numerator, + brute_ema_weight_denominator); +} + /** * DOC: brute_max_faults * @@ -30,6 +119,56 @@ static unsigned int brute_ema_weight_denominator __read_mostly = 10; */ static unsigned int brute_max_faults __read_mostly = 200; +/** + * brute_update_crash_period() - Update the application crash period. + * @stats: Statistics that hold the application crash period to update. Cannot + * be NULL. + * + * The application crash period must be a value that is not prone to change due + * to spurious data and follows the real crash period. So, to compute it, the + * exponential moving average (EMA) is used. + * + * This kind of average defines a weight (between 0 and 1) for the new value to + * add and applies the remainder of the weight to the current average value. + * This way, some spurious data will not excessively modify the average and only + * if the new values are persistent, the moving average will tend towards them. + * + * Mathematically the application crash period's EMA can be expressed as + * follows: + * + * period_ema = period * weight + period_ema * (1 - weight) + * + * If the operations are applied: + * + * period_ema = period * weight + period_ema - period_ema * weight + * + * If the operands are ordered: + * + * period_ema = period_ema - period_ema * weight + period * weight + * + * Finally, this formula can be written as follows: + * + * period_ema -= period_ema * weight; + * period_ema += period * weight; + */ +static void brute_update_crash_period(struct brute_stats *stats) +{ + u64 current_period; + u64 now = ktime_get_clocktai_ns(); + + if (stats->faults >= (u32)brute_max_faults) + return; + + if (stats->nsecs) { + current_period = now > stats->nsecs ? now - stats->nsecs : 0; + stats->period -= brute_mul_by_ema_weight(stats->period); + stats->period += brute_mul_by_ema_weight(current_period); + } + + stats->nsecs = now; + stats->faults += 1; +} + /** * DOC: brute_min_faults * @@ -51,6 +190,343 @@ static unsigned int brute_min_faults __read_mostly = 5; */ static unsigned int brute_crash_period_threshold __read_mostly = 30; +/** + * brute_attack_running() - Test if a brute force attack is happening. + * @stats: Statistical data shared by all the fork hierarchy processes. Cannot + * be NULL. + * + * The decision if a brute force attack is running is based on the statistical + * data shared by all the fork hierarchy processes. + * + * There are two types of brute force attacks that can be detected using the + * statistical data. The first one is a slow brute force attack that is detected + * if the maximum number of faults per fork hierarchy is reached. The second + * type is a fast brute force attack that is detected if the application crash + * period falls below a certain threshold. + * + * Moreover, it is important to note that no attacks will be detected until a + * minimum number of faults have occurred. This allows to have a trend in the + * crash period when the EMA is used. + * + * Return: True if a brute force attack is happening. False otherwise. + */ +static bool brute_attack_running(const struct brute_stats *stats) +{ + u64 threshold; + + if (stats->faults < (u32)brute_min_faults) + return false; + + if (stats->faults >= (u32)brute_max_faults) + return true; + + threshold = (u64)brute_crash_period_threshold * (u64)NSEC_PER_SEC; + return stats->period < threshold; +} + +/** + * brute_print_attack_running() - Warn about a fork brute force attack. + */ +static inline void brute_print_attack_running(void) +{ + pr_warn("fork brute force attack detected [pid %d: %s]\n", current->pid, + current->comm); +} + +/** + * brute_get_xattr_stats() - Get the stats from an extended attribute. + * @dentry: The dentry of the file to get the extended attribute. + * @inode: The inode of the file to get the extended attribute. + * @stats: The stats where to store the info obtained from the extended + * attribute. Cannot be NULL. + * + * Return: An error code if it is not possible to get the statistical data. Zero + * otherwise. + */ +static int brute_get_xattr_stats(struct dentry *dentry, struct inode *inode, + struct brute_stats *stats) +{ + int rc; + struct brute_raw_stats raw_stats; + + rc = __vfs_getxattr(dentry, inode, XATTR_NAME_BRUTE, &raw_stats, + sizeof(raw_stats)); + if (rc < 0) + return rc; + + stats->faults = le32_to_cpu(raw_stats.faults); + stats->nsecs = le64_to_cpu(raw_stats.nsecs); + stats->period = le64_to_cpu(raw_stats.period); + stats->flags = raw_stats.flags; + return 0; +} + +/** + * brute_set_xattr_stats() - Set the stats to an extended attribute. + * @dentry: The dentry of the file to set the extended attribute. + * @inode: The inode of the file to set the extended attribute. + * @stats: The stats from where to extract the info to set the extended attribute. + * Cannot be NULL. + * + * Return: An error code if it is not possible to set the statistical data. Zero + * otherwise. + */ +static int brute_set_xattr_stats(struct dentry *dentry, struct inode *inode, + const struct brute_stats *stats) +{ + struct brute_raw_stats raw_stats; + + raw_stats.faults = cpu_to_le32(stats->faults); + raw_stats.nsecs = cpu_to_le64(stats->nsecs); + raw_stats.period = cpu_to_le64(stats->period); + raw_stats.flags = stats->flags; + + return __vfs_setxattr(&init_user_ns, dentry, inode, XATTR_NAME_BRUTE, + &raw_stats, sizeof(raw_stats), 0); +} + +/** + * brute_update_xattr_stats() - Update the stats of a file. + * @file: The file that holds the statistical data to update. Cannot be NULL. + * + * For a correct management of a fork brute force attack it is only necessary to + * update the statistics and test if an attack is happening based on these data. + * It is important to note that if the file has no stats nothing is updated nor + * created. This way, the scenario where an application has not crossed any + * privilege boundary is avoided since the existence of the extended attribute + * denotes the crossing of bounds. + */ +static void brute_update_xattr_stats(const struct file *file) +{ + struct dentry *dentry = file_dentry(file); + struct inode *inode = file_inode(file); + struct brute_stats stats; + int rc; + + inode_lock(inode); + rc = brute_get_xattr_stats(dentry, inode, &stats); + WARN_ON_ONCE(rc && rc != -ENODATA); + if (rc) { + inode_unlock(inode); + return; + } + + brute_update_crash_period(&stats); + if (brute_attack_running(&stats)) { + brute_print_attack_running(); + stats.not_allowed = true; + } + + rc = brute_set_xattr_stats(dentry, inode, &stats); + WARN_ON_ONCE(rc); + inode_unlock(inode); +} + +/** + * brute_reset_stats() - Reset the statistical data. + * @stats: Statistics to be reset. Cannot be NULL. + */ +static inline void brute_reset_stats(struct brute_stats *stats) +{ + memset(stats, 0, sizeof(*stats)); +} + +/** + * brute_new_xattr_stats() - New statistics for a file. + * @file: The file in which to create the new statistical data. Cannot be NULL. + * + * Only if the file has no statistical data create it. This function will be + * called to mark that a privilege boundary has been crossed so, if new stats + * are required, they do not contain any useful data. The existence of the + * extended attribute denotes the crossing of privilege bounds. + * + * Return: An error code if it is not possible to get or set the statistical + * data. Zero otherwise. + */ +static int brute_new_xattr_stats(const struct file *file) +{ + struct dentry *dentry = file_dentry(file); + struct inode *inode = file_inode(file); + struct brute_stats stats; + int rc; + + inode_lock(inode); + rc = brute_get_xattr_stats(dentry, inode, &stats); + if (rc && rc != -ENODATA) + goto unlock; + + if (rc == -ENODATA) { + brute_reset_stats(&stats); + rc = brute_set_xattr_stats(dentry, inode, &stats); + if (rc) + goto unlock; + } + +unlock: + inode_unlock(inode); + return rc; +} + +/** + * brute_current_new_xattr_stats() - New stats for the current task's exe file. + * + * Return: An error code if it is not possible to get or set the statistical + * data. Zero otherwise. + */ +static int brute_current_new_xattr_stats(void) +{ + struct file *exe_file; + int rc; + + exe_file = brute_get_current_exe_file(); + if (WARN_ON_ONCE(!exe_file)) + return -ENOENT; + + rc = brute_new_xattr_stats(exe_file); + WARN_ON_ONCE(rc); + fput(exe_file); + return rc; +} + +/** + * brute_signal_from_user() - Test if a signal is coming from userspace. + * @siginfo: Contains the signal information. + * + * To avoid false positives during the attack detection it is necessary to + * narrow the possible cases. So, only the signals delivered by the kernel are + * taken into account with the exception of the SIGABRT signal since the latter + * is used by glibc for stack canary, malloc, etc failures, which may indicate + * that a mitigation has been triggered. + * + * Return: True if the signal is coming from usersapce. False otherwise. + */ +static inline bool brute_signal_from_user(const kernel_siginfo_t *siginfo) +{ + return siginfo->si_signo == SIGKILL && siginfo->si_code != SIGABRT; +} + +/** + * brute_task_fatal_signal() - Target for the task_fatal_signal hook. + * @siginfo: Contains the signal information. + * + * To detect a brute force attack it is necessary, as a first step, to test in + * every fatal crash if the signal is delibered by the kernel. If so, update the + * statistics and act based on these data. + */ +static void brute_task_fatal_signal(const kernel_siginfo_t *siginfo) +{ + struct file *exe_file; + + if (brute_signal_from_user(siginfo)) + return; + + exe_file = brute_get_current_exe_file(); + if (WARN_ON_ONCE(!exe_file)) + return; + + brute_update_xattr_stats(exe_file); + fput(exe_file); +} + +/** + * brute_task_execve() - Target for the bprm_creds_from_file hook. + * @bprm: Contains the linux_binprm structure. + * @file: Binary that will be executed without an interpreter. + * + * This hook is useful to mark that a privilege boundary (setuid/setgid process) + * has been crossed. This is done based on the "secureexec" flag. + * + * To be defensive return an error code if it is not possible to get or set the + * stats using an extended attribute since this blocks the execution of the + * file. This scenario is treated as an attack. + * + * It is important to note that here the brute_new_xattr_stats function could be + * used with a previous test of the secureexec flag. However it is better to use + * the basic xattr functions since in a future commit a test if the execution is + * allowed (via the brute_stats::not_allowed flag) will be necessary. This way, + * the stats of the file will be get only once. + * + * Return: An error code if it is not possible to get or set the statistical + * data. Zero otherwise. + */ +static int brute_task_execve(struct linux_binprm *bprm, struct file *file) +{ + struct dentry *dentry = file_dentry(bprm->file); + struct inode *inode = file_inode(bprm->file); + struct brute_stats stats; + int rc; + + inode_lock(inode); + rc = brute_get_xattr_stats(dentry, inode, &stats); + if (WARN_ON_ONCE(rc && rc != -ENODATA)) + goto unlock; + + if (rc == -ENODATA && bprm->secureexec) { + brute_reset_stats(&stats); + rc = brute_set_xattr_stats(dentry, inode, &stats); + if (WARN_ON_ONCE(rc)) + goto unlock; + } + + rc = 0; +unlock: + inode_unlock(inode); + return rc; +} + +/** + * brute_task_change_priv() - Target for the task_fix_setid hooks. + * @new: The set of credentials that will be installed. + * @old: The set of credentials that are being replaced. + * @flags: Contains one of the LSM_SETID_* values. + * + * This hook is useful to mark that a privilege boundary (privilege changes) has + * been crossed. + * + * Return: An error code if it is not possible to get or set the statistical + * data. Zero otherwise. + */ +static int brute_task_change_priv(struct cred *new, const struct cred *old, int flags) +{ + return brute_current_new_xattr_stats(); +} + +/** + * brute_socket_accept() - Target for the socket_accept hook. + * @sock: Contains the listening socket structure. + * @newsock: Contains the newly created server socket for connection. + * + * This hook is useful to mark that a privilege boundary (network to local) has + * been crossed. This is done only if the listening socket accepts external + * connections. The sockets for inter-process communication (IPC) and those that + * are listening on loopback addresses are not taken into account. + * + * Return: An error code if it is not possible to get or set the statistical + * data. Zero otherwise. + */ +static int brute_socket_accept(struct socket *sock, struct socket *newsock) +{ + struct sock *sk = sock->sk; + + if (sk->sk_family == AF_UNIX || sk->sk_family == AF_NETLINK || + sk->sk_rcv_saddr == htonl(INADDR_LOOPBACK) || + ipv6_addr_equal(&sk->sk_v6_rcv_saddr, &in6addr_loopback)) + return 0; + + return brute_current_new_xattr_stats(); +} + +/* + * brute_hooks - Targets for the LSM's hooks. + */ +static struct security_hook_list brute_hooks[] __lsm_ro_after_init = { + LSM_HOOK_INIT(task_fatal_signal, brute_task_fatal_signal), + LSM_HOOK_INIT(bprm_creds_from_file, brute_task_execve), + LSM_HOOK_INIT(task_fix_setuid, brute_task_change_priv), + LSM_HOOK_INIT(task_fix_setgid, brute_task_change_priv), + LSM_HOOK_INIT(socket_accept, brute_socket_accept), +}; + #ifdef CONFIG_SYSCTL static unsigned int uint_max = UINT_MAX; #define SYSCTL_UINT_MAX (&uint_max) @@ -137,6 +613,8 @@ static inline void brute_init_sysctl(void) { } static int __init brute_init(void) { pr_info("becoming mindful\n"); + security_add_hooks(brute_hooks, ARRAY_SIZE(brute_hooks), + KBUILD_MODNAME); brute_init_sysctl(); return 0; } From patchwork Fri May 21 17:24:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12273543 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 911CDC4707A for ; Fri, 21 May 2021 18:05:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 731EE613D0 for ; Fri, 21 May 2021 18:05:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237856AbhEUSGk (ORCPT ); Fri, 21 May 2021 14:06:40 -0400 Received: from mout.gmx.net ([212.227.15.15]:36933 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232931AbhEUSGj (ORCPT ); Fri, 21 May 2021 14:06:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621620287; bh=FkAJBNlJfXLTD1aQ6QDAIzJgHaThVI5Z24R4aGMuUUA=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=iAgVa/3bF5UaWLOS11qXVGUcBijLwHVI3/+lSKQlkeLKapq5Dx7E0Fv6Agx7eplAk QqcMhEYoxsBVzVruTuvit1W6SlN0fgyMs1o10Y9vG2U8p9Y1Aj2+DKF9isTc+jUvqz 347CPGpNZVeywpzBFvg6f/8y3m10hHX+Rz1zh3no= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from localhost.localdomain ([83.52.228.41]) by mail.gmx.net (mrgmx005 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MUXtS-1lsqh52Nw8-00QT09; Fri, 21 May 2021 20:04:47 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 4/7] security/brute: Mitigate a brute force attack Date: Fri, 21 May 2021 19:24:11 +0200 Message-Id: <20210521172414.69456-5-john.wood@gmx.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:zRoeZqE/E+sUnl6e4VWaC6n7LeLrOHxonXqERKe/uJW00GZSVOs /qTH7j1end+WvQAikPGKqA7eYPxBZAacnNY4Z7LSY8JgL0DUdxdGwvww2bfxeeJMiJKsa5g I0FyJHJblOkC78fn2a1iaqE6Q/N4uYoV+8/RwauYWwfX7+pr55UXVHCY5fzF+vSz3KI4VS7 4MmMA6hglQ6HiDGXiFCbg== X-UI-Out-Filterresults: notjunk:1;V03:K0:+WT2bkSS6RQ=:iSRmDYv2F2PmKlCpx+OmO9 0EPhng9GnF779vkXZqS7J4ioH8QxVNOqjjhLq9ELRLP6vrCibK/oOkVkDoEEaUnPeWTlawszh w5OMjp6wAlyx2CbCRQluGuxOnaGdWJzKooV+1GOrK9KVov/46JL8G/XXnjZHLoyEyIXc+ehQ/ Y4CAmEWzBYT2yVWABNO2x+jvjtZpWgIEGgL30gXZqlAggtoqIlqfnOCIfK238NH3h1A3RCM0W O649kXkDjp3qJTIbHRIErEKGWMtvRW+uTx/lXqXRVAqw+HdTjAk0C6Z5er/YpxG41Zkq9JnyI gP4yxbE/cIXo8dZMGYKu+mjIh/crnWf26eEnI3CVEdFHlZfJy8TBVD53LL4FdpER9EMzPX9NS sfd1eLLBjw6hQGDYqSniavVe+P6GlwtrSRcAS4lyJi2Coh16rbHyX4dmRPi0sIbFzV+hMdGjW vpW1FdPdUWyOIeomaEcLdYSMppRqgpwujqy/kERWvtUiQJafQPcR7L0SuHHzuW5+DQs8vlTIM 8zFEXPoA+rjMs/2Np56J4qHF7qe3bDSJP2p3REJ1vCV29X8UO920FNomiUvj5FLwy3LQCeJwK RUI5O3P+O/0ZhyEomm48oN/aeXzE6mcK9So6CXO020CuH1rVv9gI17YXX7i4x9wfUVoVny1EL /Yayib2zjBzNQd0ttfxdnOg+vyFrqEUJivc5qQnIf5FulJ9icWESdmtFHz1qmhaAsbfQQIWHd bCmKhwkY9Qp3f6W+nv5Hn3VmJXwlhneOwVfbGsPH2UHimdg3QcP5vfx9ZIM0txSNDtLv7Laou k4T7xnWKA3XyBjUPalrOpjtoh5vkPERoCwvw/cC6TCsPJ5Tq93UFTstHGf5+cv8JSnKNWkmH/ dHluKoSWPLpBJLPTq62sQGMxMEi5hjsa6XPAlEahw/QJVEfM+Q91LT3vUdX5zfceFdOSKVscg IKrU53PlZAZSyJ5Fv5u6+ARO/4ZLKKsyrA8uZ0Qu8hiFetV519WfDyBTLgAtK9XLFJo+vQSNh MPzjgzoiprBMQs27z8z89Bujgly4zWYGiq/Ri55rkAwUgm4Bwc2kzPDgmdYHLM1UzXBkLu1I0 MnZTFy14YoFofmyfWXTVrQD58pgNERMVqK35sVGrrQo1hEkxvIgE1mhP32BCrkdd/3nkzzM9r y9DjiniX+cHw0/faaHJn2JeyDcBxGbUAbGhyd//H9xS9Abc1QYiqzdBlydvWWsZwsTPDY= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When a brute force attack is detected all the offending tasks involved in the attack must be killed. In other words, it is necessary to kill all the tasks that are executing the same file that is running during the brute force attack. Also, to prevent the executable involved in the attack from being respawned by a supervisor, and thus prevent a brute force attack from being started again, test the "not_allowed" flag and avoid the file execution based on this. Signed-off-by: John Wood --- security/brute/brute.c | 113 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 102 insertions(+), 11 deletions(-) -- 2.25.1 diff --git a/security/brute/brute.c b/security/brute/brute.c index 66db0dd0664d..7712dac888db 100644 --- a/security/brute/brute.c +++ b/security/brute/brute.c @@ -233,6 +233,88 @@ static inline void brute_print_attack_running(void) current->comm); } +/** + * brute_print_file_not_allowed() - Warn about a file not allowed. + * @dentry: The dentry of the file not allowed. + */ +static void brute_print_file_not_allowed(struct dentry *dentry) +{ + char *buf, *path; + + buf = __getname(); + if (WARN_ON_ONCE(!buf)) + return; + + path = dentry_path_raw(dentry, buf, PATH_MAX); + if (WARN_ON_ONCE(IS_ERR(path))) + goto free; + + pr_warn_ratelimited("%s not allowed\n", path); +free: + __putname(buf); +} + +/** + * brute_is_same_file() - Test if two files are the same. + * @file1: First file to compare. Cannot be NULL. + * @file2: Second file to compare. Cannot be NULL. + * + * Two files are the same if they have the same inode number and the same block + * device. + * + * Return: True if the two files are the same. False otherwise. + */ +static inline bool brute_is_same_file(const struct file *file1, + const struct file *file2) +{ + struct inode *inode1 = file_inode(file1); + struct inode *inode2 = file_inode(file2); + + return inode1->i_ino == inode2->i_ino && + inode1->i_sb->s_dev == inode2->i_sb->s_dev; +} + +/** + * brute_kill_offending_tasks() - Kill the offending tasks. + * @file: The file executed during a brute force attack. Cannot be NULL. + * + * When a brute force attack is detected all the offending tasks involved in the + * attack must be killed. In other words, it is necessary to kill all the tasks + * that are executing the same file that is running during the brute force + * attack. Moreover, the processes that have the same group_leader that the + * current task must be avoided since they are in the path to be killed. + * + * The for_each_process loop is protected by the tasklist_lock acquired in read + * mode instead of rcu_read_lock to avoid that the newly created processes + * escape this RCU read lock. + */ +static void brute_kill_offending_tasks(const struct file *file) +{ + struct task_struct *task; + struct file *exe_file; + bool is_same_file; + + read_lock(&tasklist_lock); + for_each_process(task) { + if (task->group_leader == current->group_leader) + continue; + + exe_file = get_task_exe_file(task); + if (!exe_file) + continue; + + is_same_file = brute_is_same_file(exe_file, file); + fput(exe_file); + if (!is_same_file) + continue; + + do_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_PID); + pr_warn_ratelimited("Offending process %d [%s] killed\n", + task->pid, task->comm); + } + read_unlock(&tasklist_lock); +} + /** * brute_get_xattr_stats() - Get the stats from an extended attribute. * @dentry: The dentry of the file to get the extended attribute. @@ -295,6 +377,10 @@ static int brute_set_xattr_stats(struct dentry *dentry, struct inode *inode, * created. This way, the scenario where an application has not crossed any * privilege boundary is avoided since the existence of the extended attribute * denotes the crossing of bounds. + * + * Also, do not update the statistics if the execution of the file is not + * allowed and kill all the offending tasks when a brute force attack is + * detected. */ static void brute_update_xattr_stats(const struct file *file) { @@ -306,7 +392,7 @@ static void brute_update_xattr_stats(const struct file *file) inode_lock(inode); rc = brute_get_xattr_stats(dentry, inode, &stats); WARN_ON_ONCE(rc && rc != -ENODATA); - if (rc) { + if (rc || (!rc && stats.not_allowed)) { inode_unlock(inode); return; } @@ -320,6 +406,9 @@ static void brute_update_xattr_stats(const struct file *file) rc = brute_set_xattr_stats(dentry, inode, &stats); WARN_ON_ONCE(rc); inode_unlock(inode); + + if (stats.not_allowed) + brute_kill_offending_tasks(file); } /** @@ -433,21 +522,17 @@ static void brute_task_fatal_signal(const kernel_siginfo_t *siginfo) * @bprm: Contains the linux_binprm structure. * @file: Binary that will be executed without an interpreter. * - * This hook is useful to mark that a privilege boundary (setuid/setgid process) - * has been crossed. This is done based on the "secureexec" flag. + * If there are statistics, test the "not_allowed" flag and avoid the file + * execution based on this. Also, this hook is useful to mark that a privilege + * boundary (setuid/setgid process) has been crossed. This is done based on the + * "secureexec" flag. * * To be defensive return an error code if it is not possible to get or set the * stats using an extended attribute since this blocks the execution of the * file. This scenario is treated as an attack. * - * It is important to note that here the brute_new_xattr_stats function could be - * used with a previous test of the secureexec flag. However it is better to use - * the basic xattr functions since in a future commit a test if the execution is - * allowed (via the brute_stats::not_allowed flag) will be necessary. This way, - * the stats of the file will be get only once. - * - * Return: An error code if it is not possible to get or set the statistical - * data. Zero otherwise. + * Return: -EPERM if the execution of the file is not allowed. An error code if + * it is not possible to get or set the statistical data. Zero otherwise. */ static int brute_task_execve(struct linux_binprm *bprm, struct file *file) { @@ -461,6 +546,12 @@ static int brute_task_execve(struct linux_binprm *bprm, struct file *file) if (WARN_ON_ONCE(rc && rc != -ENODATA)) goto unlock; + if (!rc && stats.not_allowed) { + brute_print_file_not_allowed(dentry); + rc = -EPERM; + goto unlock; + } + if (rc == -ENODATA && bprm->secureexec) { brute_reset_stats(&stats); rc = brute_set_xattr_stats(dentry, inode, &stats); From patchwork Sat May 22 06:35:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12274351 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63F12C4707E for ; Sat, 22 May 2021 06:36:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D49C6120D for ; Sat, 22 May 2021 06:36:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229952AbhEVGiA (ORCPT ); Sat, 22 May 2021 02:38:00 -0400 Received: from mout.gmx.net ([212.227.17.22]:36867 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229689AbhEVGiA (ORCPT ); Sat, 22 May 2021 02:38:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621665354; bh=hmQBDVRwQZGdfUeCmGY0i6E6TJ8Eh2j60vUrtQTIASY=; h=X-UI-Sender-Class:Date:From:To:Cc:Subject:References:In-Reply-To; b=KIFMqP+whBZ8KmQ8l+tpjRervYyri9smUEvbMomF2mla2lenPn3Mt/ys1k3vyer3n kfruTWsQH6xvAdyD90oegzCGKFf2t+zAyztZC1+HcwLtZs+nqHMSTUu1pAr+ONyZse v0xPl7vRcVtwS/g8dWjWQ+azALQO6EACLidejIoU= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from ubuntu ([83.52.228.41]) by mail.gmx.net (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1M59C8-1llRAT2dMa-001CeS; Sat, 22 May 2021 08:35:53 +0200 Date: Sat, 22 May 2021 08:35:13 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 5/7] selftests/brute: Add tests for the Brute LSM Message-ID: <20210522063513.GA3094@ubuntu> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> X-Provags-ID: V03:K1:pCZdcB7GyPfC/MfGFJ8rtDrcfAmecBYR3LlmpouuSQO6BCQARbC gywvwTNeAVVMMxPkTDz1YVmFpyiDFQjnDQrhH7Y+VBl7JtJxF97wx9M+wl8xdrNv0WAEig/ sYwUNJxAOTdlTfIKyrC+C9GO8ecJSUuEls8wJr5UOW6NFK+MvgM1vRMa/ubM4lkGTfpma3z HYo8ZJyzkRsN44/dT/JyQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:ye3mU39bEnU=:VyOB+AmPJTXmezFlzhoCwY gPZ+xenlW/7NSxy2How1epUIouG3a+UjWdemUf7P0CYt97qSr7v4owYX5Y2k4Qm0DhxAllgGo ubJYnpKDk3sdAmxGIbHbNY5LGPJ+CRHJABrvRISbVjbn2+tU31WKKDE6uIBkw0/X960uCTn+G p0Tr8X3RkMDr4FWNFakhJecewbT2D+9bwU4ncLhOJsDhm0LMgSZAsUfiZNAqNKeZN8KLWEP15 GjQ5eBZf8PJggBpYV68M+ZfrtSeOEPUApy5ZMGyEEZTqQ8O/Mqi3+RNHbP/asDuFVrInBM4Yd ktyrU7NpZeFKLf72o5L3cPHpQKd5rc6Ka8rWzaPkPUI0I6Ueh7tqErGMXCAWDQr9oCkqRtEGd OPE+/ESA9uy5lUT07taZXO+MKu+CEuDuvbiwDi+Z0xzba1tzc52L4pPrWnnE8sMX1EOAmH8de GFjrdT/Zrw7Y/lUBFcKvxZlEQXKZYg8EpswVT+xB+07ofzpbUEi9AGwZEtapdcs3Ztv2mEWqr wXge6g0M2NY6WT8s1wer9CnAJmXY2P4Rnk8pPZraW2SWIjXomc27KDK9IxL2eG3AZSznBEzKC r9ie4Z8mI8f4hbUcygT29tfKYhIwbmeOMcwEe8NY44orCR7Ap8QLCq4ZAhN6Y72nGbYQqU9V4 IVDndbdwFIguwPHoBmXBDaFjf9oHoPG60L8kXXth3Ns3asL+0DlaTHZt8dG1wcSas5Elh6Acu dEVD6FgaQGfpP3+8xS5VSbvBGHslvpW+344Dm/b1lYC838zHhJvYVVAnJ5gvuUrvN6uEB94Km zNdgwv4X5JZ6TlIcyVmY+7WgruvFqxCSlofJDWk5kNEHFSDDK7NyKSB5uGrsu358MUOUCUi0Z CAk+CG+5xoB0Gq+yn0olhLupADIwoLPRXt2I0KT/xrjzjDYdDKBEoM6nM4MPOjeN4Orw5epea luo2yYBqIY/3vzSC1zTaOe3HVjPVLRudoMH9tICGBxP99YmqX10boXasNPDas4rgYuSY/oZhY RzRG+whz6NHUIOaSm0RR0PF6GTeL5yUahKVvXFClVCbwNgKsI71wivd9wHA57YSiVrVfasYEj k80KZF3n4SyFOnqLNhP9/NL1mMHd+za5tMl5syGiIGnNxanJ+V7IRYUAeboOYDodnWkjgWkBu kUvoegWy0xBAX5fjm7hPGMKW8CrnADIQaCMBcfz6UjGXla0vtofJqcw5p+BZ+AQ06OiPU= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add tests to check the brute LSM functionality and cover fork/exec brute force attacks crossing the following privilege boundaries: 1.- setuid process 2.- privilege changes 3.- network to local Also, as a first step check that fork/exec brute force attacks without crossing any privilege boundary already commented doesn't trigger the detection and mitigation stage. Once a brute force attack is detected, the "test" executable is marked as "not allowed". To start again a new test, use the "rmxattr" app to revert this state. This way, all the tests can be run using the same binary. Signed-off-by: John Wood --- tools/testing/selftests/Makefile | 1 + tools/testing/selftests/brute/.gitignore | 2 + tools/testing/selftests/brute/Makefile | 5 + tools/testing/selftests/brute/config | 1 + tools/testing/selftests/brute/rmxattr.c | 34 ++ tools/testing/selftests/brute/test.c | 507 +++++++++++++++++++++++ tools/testing/selftests/brute/test.sh | 256 ++++++++++++ 7 files changed, 806 insertions(+) create mode 100644 tools/testing/selftests/brute/.gitignore create mode 100644 tools/testing/selftests/brute/Makefile create mode 100644 tools/testing/selftests/brute/config create mode 100644 tools/testing/selftests/brute/rmxattr.c create mode 100644 tools/testing/selftests/brute/test.c create mode 100755 tools/testing/selftests/brute/test.sh -- 2.25.1 diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile index bc3299a20338..5c413a010849 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -2,6 +2,7 @@ TARGETS = arm64 TARGETS += bpf TARGETS += breakpoints +TARGETS += brute TARGETS += capabilities TARGETS += cgroup TARGETS += clone3 diff --git a/tools/testing/selftests/brute/.gitignore b/tools/testing/selftests/brute/.gitignore new file mode 100644 index 000000000000..989894615766 --- /dev/null +++ b/tools/testing/selftests/brute/.gitignore @@ -0,0 +1,2 @@ +rmxattr +test diff --git a/tools/testing/selftests/brute/Makefile b/tools/testing/selftests/brute/Makefile new file mode 100644 index 000000000000..c675d1df62ca --- /dev/null +++ b/tools/testing/selftests/brute/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +CFLAGS += -Wall -O2 +TEST_PROGS := test.sh +TEST_GEN_FILES := rmxattr test +include ../lib.mk diff --git a/tools/testing/selftests/brute/config b/tools/testing/selftests/brute/config new file mode 100644 index 000000000000..3587b7bf6c23 --- /dev/null +++ b/tools/testing/selftests/brute/config @@ -0,0 +1 @@ +CONFIG_SECURITY_FORK_BRUTE=y diff --git a/tools/testing/selftests/brute/rmxattr.c b/tools/testing/selftests/brute/rmxattr.c new file mode 100644 index 000000000000..9ed90409d337 --- /dev/null +++ b/tools/testing/selftests/brute/rmxattr.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include + +static __attribute__((noreturn)) void error_failure(const char *message) +{ + perror(message); + exit(EXIT_FAILURE); +} + +#define PROG_NAME basename(argv[0]) + +#define XATTR_SECURITY_PREFIX "security." +#define XATTR_BRUTE_SUFFIX "brute" +#define XATTR_NAME_BRUTE XATTR_SECURITY_PREFIX XATTR_BRUTE_SUFFIX + +int main(int argc, char **argv) +{ + int rc; + + if (argc < 2) { + printf("Usage: %s \n", PROG_NAME); + exit(EXIT_FAILURE); + } + + rc = removexattr(argv[1], XATTR_NAME_BRUTE); + if (rc) + error_failure("removexattr"); + + return EXIT_SUCCESS; +} diff --git a/tools/testing/selftests/brute/test.c b/tools/testing/selftests/brute/test.c new file mode 100644 index 000000000000..44c32f446dca --- /dev/null +++ b/tools/testing/selftests/brute/test.c @@ -0,0 +1,507 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static const char *message = "message"; + +enum mode { + MODE_NONE, + MODE_CRASH, + MODE_SERVER_CRASH, + MODE_CLIENT, +}; + +enum crash_after { + CRASH_AFTER_NONE, + CRASH_AFTER_FORK, + CRASH_AFTER_EXEC, +}; + +enum signal_from { + SIGNAL_FROM_NONE, + SIGNAL_FROM_USER, + SIGNAL_FROM_KERNEL, +}; + +struct args { + uint32_t ip; + uint16_t port; + int counter; + long timeout; + enum mode mode; + enum crash_after crash_after; + enum signal_from signal_from; + unsigned char has_counter : 1; + unsigned char has_change_priv : 1; + unsigned char has_ip : 1; + unsigned char has_port : 1; + unsigned char has_timeout : 1; +}; + +#define OPT_STRING "hm:c:s:n:Ca:p:t:" + +static void usage(const char *prog) +{ + printf("Usage: %s \n", prog); + printf("OPTIONS:\n"); + printf(" -h: Show this help and exit. Optional.\n"); + printf(" -m (crash | server_crash | client): Mode. Required.\n"); + printf("Options for crash mode:\n"); + printf(" -c (fork | exec): Crash after. Optional.\n"); + printf(" -s (user | kernel): Signal from. Required.\n"); + printf(" -n counter: Number of crashes.\n"); + printf(" Required if the option -c is used.\n"); + printf(" Not used without the option -c.\n"); + printf(" Range from 1 to INT_MAX.\n"); + printf(" -C: Change privileges before crash. Optional.\n"); + printf("Options for server_crash mode:\n"); + printf(" -a ip: Ip v4 address to accept. Required.\n"); + printf(" -p port: Port number. Required.\n"); + printf(" Range from 1 to UINT16_MAX.\n"); + printf(" -t secs: Accept timeout. Required.\n"); + printf(" Range from 1 to LONG_MAX.\n"); + printf(" -c (fork | exec): Crash after. Required.\n"); + printf(" -s (user | kernel): Signal from. Required.\n"); + printf(" -n counter: Number of crashes. Required.\n"); + printf(" Range from 1 to INT_MAX.\n"); + printf("Options for client mode:\n"); + printf(" -a ip: Ip v4 address to connect. Required.\n"); + printf(" -p port: Port number. Required.\n"); + printf(" Range from 1 to UINT16_MAX.\n"); + printf(" -t secs: Connect timeout. Required.\n"); + printf(" Range from 1 to LONG_MAX.\n"); +} + +static __attribute__((noreturn)) void info_failure(const char *message, + const char *prog) +{ + printf("%s\n", message); + usage(prog); + exit(EXIT_FAILURE); +} + +static enum mode get_mode(const char *text, const char *prog) +{ + if (!strcmp(text, "crash")) + return MODE_CRASH; + + if (!strcmp(text, "server_crash")) + return MODE_SERVER_CRASH; + + if (!strcmp(text, "client")) + return MODE_CLIENT; + + info_failure("Invalid mode option [-m].", prog); +} + +static enum crash_after get_crash_after(const char *text, const char *prog) +{ + if (!strcmp(text, "fork")) + return CRASH_AFTER_FORK; + + if (!strcmp(text, "exec")) + return CRASH_AFTER_EXEC; + + info_failure("Invalid crash after option [-c].", prog); +} + +static enum signal_from get_signal_from(const char *text, const char *prog) +{ + if (!strcmp(text, "user")) + return SIGNAL_FROM_USER; + + if (!strcmp(text, "kernel")) + return SIGNAL_FROM_KERNEL; + + info_failure("Invalid signal from option [-s]", prog); +} + +static int get_counter(const char *text, const char *prog) +{ + int counter; + + counter = atoi(text); + if (counter > 0) + return counter; + + info_failure("Invalid counter option [-n].", prog); +} + +static __attribute__((noreturn)) void error_failure(const char *message) +{ + perror(message); + exit(EXIT_FAILURE); +} + +static uint32_t get_ip(const char *text, const char *prog) +{ + int ret; + uint32_t ip; + + ret = inet_pton(AF_INET, text, &ip); + if (!ret) + info_failure("Invalid ip option [-a].", prog); + else if (ret < 0) + error_failure("inet_pton"); + + return ip; +} + +static uint16_t get_port(const char *text, const char *prog) +{ + long port; + + port = atol(text); + if ((port > 0) && (port <= UINT16_MAX)) + return htons(port); + + info_failure("Invalid port option [-p].", prog); +} + +static long get_timeout(const char *text, const char *prog) +{ + long timeout; + + timeout = atol(text); + if (timeout > 0) + return timeout; + + info_failure("Invalid timeout option [-t].", prog); +} + +static void check_args(const struct args *args, const char *prog) +{ + if (args->mode == MODE_CRASH && args->crash_after != CRASH_AFTER_NONE && + args->signal_from != SIGNAL_FROM_NONE && args->has_counter && + !args->has_ip && !args->has_port && !args->has_timeout) + return; + + if (args->mode == MODE_CRASH && args->signal_from != SIGNAL_FROM_NONE && + args->crash_after == CRASH_AFTER_NONE && !args->has_counter && + !args->has_ip && !args->has_port && !args->has_timeout) + return; + + if (args->mode == MODE_SERVER_CRASH && args->has_ip && args->has_port && + args->has_timeout && args->crash_after != CRASH_AFTER_NONE && + args->signal_from != SIGNAL_FROM_NONE && args->has_counter && + !args->has_change_priv) + return; + + if (args->mode == MODE_CLIENT && args->has_ip && args->has_port && + args->has_timeout && args->crash_after == CRASH_AFTER_NONE && + args->signal_from == SIGNAL_FROM_NONE && !args->has_counter && + !args->has_change_priv) + return; + + info_failure("Invalid use of options.", prog); +} + +static uid_t get_non_root_uid(void) +{ + struct passwd *pwent; + uid_t uid; + + while (true) { + errno = 0; + pwent = getpwent(); + if (!pwent) { + if (errno) { + perror("getpwent"); + endpwent(); + exit(EXIT_FAILURE); + } + break; + } + + if (pwent->pw_uid) { + uid = pwent->pw_uid; + endpwent(); + return uid; + } + } + + endpwent(); + printf("A user different of root is needed.\n"); + exit(EXIT_FAILURE); +} + +static inline void do_sigsegv(void) +{ + int *p = NULL; + *p = 0; +} + +static void do_sigkill(void) +{ + int ret; + + ret = kill(getpid(), SIGKILL); + if (ret) + error_failure("kill"); +} + +static void crash(enum signal_from signal_from, bool change_priv) +{ + int ret; + + if (change_priv) { + ret = setuid(get_non_root_uid()); + if (ret) + error_failure("setuid"); + } + + if (signal_from == SIGNAL_FROM_KERNEL) + do_sigsegv(); + + do_sigkill(); +} + +static void execve_crash(char *const argv[]) +{ + execve(argv[0], argv, NULL); + error_failure("execve"); +} + +static void exec_crash_user(void) +{ + char *const argv[] = { + "./test", "-m", "crash", "-s", "user", NULL, + }; + + execve_crash(argv); +} + +static void exec_crash_user_change_priv(void) +{ + char *const argv[] = { + "./test", "-m", "crash", "-s", "user", "-C", NULL, + }; + + execve_crash(argv); +} + +static void exec_crash_kernel(void) +{ + char *const argv[] = { + "./test", "-m", "crash", "-s", "kernel", NULL, + }; + + execve_crash(argv); +} + +static void exec_crash_kernel_change_priv(void) +{ + char *const argv[] = { + "./test", "-m", "crash", "-s", "kernel", "-C", NULL, + }; + + execve_crash(argv); +} + +static void exec_crash(enum signal_from signal_from, bool change_priv) +{ + if (signal_from == SIGNAL_FROM_USER && !change_priv) + exec_crash_user(); + if (signal_from == SIGNAL_FROM_USER && change_priv) + exec_crash_user_change_priv(); + if (signal_from == SIGNAL_FROM_KERNEL && !change_priv) + exec_crash_kernel(); + if (signal_from == SIGNAL_FROM_KERNEL && change_priv) + exec_crash_kernel_change_priv(); +} + +static void do_crash(enum crash_after crash_after, enum signal_from signal_from, + int counter, bool change_priv) +{ + pid_t pid; + int status; + + if (crash_after == CRASH_AFTER_NONE) + crash(signal_from, change_priv); + + while (counter > 0) { + pid = fork(); + if (pid < 0) + error_failure("fork"); + + /* Child process */ + if (!pid) { + if (crash_after == CRASH_AFTER_FORK) + crash(signal_from, change_priv); + + exec_crash(signal_from, change_priv); + } + + /* Parent process */ + counter -= 1; + pid = waitpid(pid, &status, 0); + if (pid < 0) + error_failure("waitpid"); + } +} + +static __attribute__((noreturn)) void error_close_failure(const char *message, + int fd) +{ + perror(message); + close(fd); + exit(EXIT_FAILURE); +} + +static void do_server(uint32_t ip, uint16_t port, long accept_timeout) +{ + int sockfd; + int ret; + struct sockaddr_in address; + struct timeval timeout; + int newsockfd; + + sockfd = socket(AF_INET, SOCK_STREAM, 0); + if (sockfd < 0) + error_failure("socket"); + + address.sin_family = AF_INET; + address.sin_addr.s_addr = ip; + address.sin_port = port; + + ret = bind(sockfd, (const struct sockaddr *)&address, sizeof(address)); + if (ret) + error_close_failure("bind", sockfd); + + ret = listen(sockfd, 1); + if (ret) + error_close_failure("listen", sockfd); + + timeout.tv_sec = accept_timeout; + timeout.tv_usec = 0; + ret = setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, + (const struct timeval *)&timeout, sizeof(timeout)); + if (ret) + error_close_failure("setsockopt", sockfd); + + newsockfd = accept(sockfd, NULL, NULL); + if (newsockfd < 0) + error_close_failure("accept", sockfd); + + close(sockfd); + close(newsockfd); +} + +static void do_client(uint32_t ip, uint16_t port, long connect_timeout) +{ + int sockfd; + int ret; + struct timeval timeout; + struct sockaddr_in address; + + sockfd = socket(AF_INET, SOCK_STREAM, 0); + if (sockfd < 0) + error_failure("socket"); + + timeout.tv_sec = connect_timeout; + timeout.tv_usec = 0; + ret = setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, + (const struct timeval *)&timeout, sizeof(timeout)); + if (ret) + error_close_failure("setsockopt", sockfd); + + address.sin_family = AF_INET; + address.sin_addr.s_addr = ip; + address.sin_port = port; + + ret = connect(sockfd, (const struct sockaddr *)&address, + sizeof(address)); + if (ret) + error_close_failure("connect", sockfd); + + ret = write(sockfd, message, strlen(message)); + if (ret < 0) + error_close_failure("write", sockfd); + + close(sockfd); +} + +#define PROG_NAME basename(argv[0]) + +int main(int argc, char **argv) +{ + int opt; + struct args args = { + .mode = MODE_NONE, + .crash_after = CRASH_AFTER_NONE, + .signal_from = SIGNAL_FROM_NONE, + .has_counter = false, + .has_change_priv = false, + .has_ip = false, + .has_port = false, + .has_timeout = false, + }; + + while ((opt = getopt(argc, argv, OPT_STRING)) != -1) { + switch (opt) { + case 'h': + usage(PROG_NAME); + return EXIT_SUCCESS; + case 'm': + args.mode = get_mode(optarg, PROG_NAME); + break; + case 'c': + args.crash_after = get_crash_after(optarg, PROG_NAME); + break; + case 's': + args.signal_from = get_signal_from(optarg, PROG_NAME); + break; + case 'n': + args.counter = get_counter(optarg, PROG_NAME); + args.has_counter = true; + break; + case 'C': + args.has_change_priv = true; + break; + case 'a': + args.ip = get_ip(optarg, PROG_NAME); + args.has_ip = true; + break; + case 'p': + args.port = get_port(optarg, PROG_NAME); + args.has_port = true; + break; + case 't': + args.timeout = get_timeout(optarg, PROG_NAME); + args.has_timeout = true; + break; + default: + usage(PROG_NAME); + return EXIT_FAILURE; + } + } + + check_args(&args, PROG_NAME); + + if (args.mode == MODE_CRASH) { + do_crash(args.crash_after, args.signal_from, args.counter, + args.has_change_priv); + } else if (args.mode == MODE_SERVER_CRASH) { + do_server(args.ip, args.port, args.timeout); + do_crash(args.crash_after, args.signal_from, args.counter, + false); + } else if (args.mode == MODE_CLIENT) { + do_client(args.ip, args.port, args.timeout); + } + + return EXIT_SUCCESS; +} diff --git a/tools/testing/selftests/brute/test.sh b/tools/testing/selftests/brute/test.sh new file mode 100755 index 000000000000..47173f38a7c6 --- /dev/null +++ b/tools/testing/selftests/brute/test.sh @@ -0,0 +1,256 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +TCID="test.sh" + +KSFT_PASS=0 +KSFT_FAIL=1 +KSFT_SKIP=4 + +errno=$KSFT_PASS + +check_root() +{ + local uid=$(id -u) + if [ $uid -ne 0 ]; then + echo $TCID: must be run as root >&2 + exit $KSFT_SKIP + fi +} + +tmp_files_setup() +{ + DMESG=$(mktemp --tmpdir -t brute-dmesg-XXXXXX) +} + +tmp_files_cleanup() +{ + rm -f "$DMESG" +} + +save_dmesg() +{ + dmesg > "$DMESG" +} + +count_attack_matches() +{ + dmesg | comm --nocheck-order -13 "$DMESG" - | \ + grep "brute: fork brute force attack detected" | wc -l +} + +assert_equal() +{ + local val1=$1 + local val2=$2 + + if [ $val1 -eq $val2 ]; then + echo "$TCID: $message [PASS]" + else + echo "$TCID: $message [FAIL]" + errno=$KSFT_FAIL + fi +} + +test_fork_user() +{ + COUNTER=20 + + save_dmesg + ./test -m crash -c fork -s user -n $COUNTER + count=$(count_attack_matches) + + message="Fork attack (user signals, no bounds crossed)" + assert_equal $count 0 +} + +test_fork_kernel() +{ + save_dmesg + ./test -m crash -c fork -s kernel -n $COUNTER + count=$(count_attack_matches) + + message="Fork attack (kernel signals, no bounds crossed)" + assert_equal $count 0 +} + +test_exec_user() +{ + save_dmesg + ./test -m crash -c exec -s user -n $COUNTER + count=$(count_attack_matches) + + message="Exec attack (user signals, no bounds crossed)" + assert_equal $count 0 +} + +test_exec_kernel() +{ + save_dmesg + ./test -m crash -c exec -s kernel -n $COUNTER + count=$(count_attack_matches) + + message="Exec attack (kernel signals, no bounds crossed)" + assert_equal $count 0 +} + +assert_not_equal() +{ + local val1=$1 + local val2=$2 + + if [ $val1 -ne $val2 ]; then + echo $TCID: $message [PASS] + else + echo $TCID: $message [FAIL] + errno=$KSFT_FAIL + fi +} + +remove_xattr() +{ + ./rmxattr test >/dev/null 2>&1 +} + +test_fork_kernel_setuid() +{ + save_dmesg + chmod u+s test + ./test -m crash -c fork -s kernel -n $COUNTER + chmod u-s test + count=$(count_attack_matches) + + message="Fork attack (kernel signals, setuid binary)" + assert_not_equal $count 0 + remove_xattr +} + +test_exec_kernel_setuid() +{ + save_dmesg + chmod u+s test + ./test -m crash -c exec -s kernel -n $COUNTER + chmod u-s test + count=$(count_attack_matches) + + message="Exec attack (kernel signals, setuid binary)" + assert_not_equal $count 0 + remove_xattr +} + +test_fork_kernel_change_priv() +{ + save_dmesg + ./test -m crash -c fork -s kernel -n $COUNTER -C + count=$(count_attack_matches) + + message="Fork attack (kernel signals, change privileges)" + assert_not_equal $count 0 + remove_xattr +} + +test_exec_kernel_change_priv() +{ + save_dmesg + ./test -m crash -c exec -s kernel -n $COUNTER -C + count=$(count_attack_matches) + + message="Exec attack (kernel signals, change privileges)" + assert_not_equal $count 0 + remove_xattr +} + +network_ns_setup() +{ + local vnet_name=$1 + local veth_name=$2 + local ip_src=$3 + local ip_dst=$4 + + ip netns add $vnet_name + ip link set $veth_name netns $vnet_name + ip -n $vnet_name addr add $ip_src/24 dev $veth_name + ip -n $vnet_name link set $veth_name up + ip -n $vnet_name route add $ip_dst/24 dev $veth_name +} + +network_setup() +{ + VETH0_NAME=veth0 + VNET0_NAME=vnet0 + VNET0_IP=10.0.1.0 + VETH1_NAME=veth1 + VNET1_NAME=vnet1 + VNET1_IP=10.0.2.0 + + ip link add $VETH0_NAME type veth peer name $VETH1_NAME + network_ns_setup $VNET0_NAME $VETH0_NAME $VNET0_IP $VNET1_IP + network_ns_setup $VNET1_NAME $VETH1_NAME $VNET1_IP $VNET0_IP +} + +test_fork_kernel_network_to_local() +{ + INADDR_ANY=0.0.0.0 + PORT=65535 + TIMEOUT=5 + + save_dmesg + ip netns exec $VNET0_NAME ./test -m server_crash -a $INADDR_ANY \ + -p $PORT -t $TIMEOUT -c fork -s kernel -n $COUNTER & + sleep 1 + ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \ + -t $TIMEOUT + sleep 1 + count=$(count_attack_matches) + + message="Fork attack (kernel signals, network to local)" + assert_not_equal $count 0 + remove_xattr +} + +test_exec_kernel_network_to_local() +{ + save_dmesg + ip netns exec $VNET0_NAME ./test -m server_crash -a $INADDR_ANY \ + -p $PORT -t $TIMEOUT -c exec -s kernel -n $COUNTER & + sleep 1 + ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \ + -t $TIMEOUT + sleep 1 + count=$(count_attack_matches) + + message="Exec attack (kernel signals, network to local)" + assert_not_equal $count 0 + remove_xattr +} + +network_cleanup() +{ + ip netns del $VNET0_NAME >/dev/null 2>&1 + ip netns del $VNET1_NAME >/dev/null 2>&1 + ip link delete $VETH0_NAME >/dev/null 2>&1 + ip link delete $VETH1_NAME >/dev/null 2>&1 +} + +cleanup() +{ + network_cleanup + tmp_files_cleanup + remove_xattr +} +trap cleanup EXIT + +check_root +tmp_files_setup +test_fork_user +test_fork_kernel +test_exec_user +test_exec_kernel +test_fork_kernel_setuid +test_exec_kernel_setuid +test_fork_kernel_change_priv +test_exec_kernel_change_priv +network_setup +test_fork_kernel_network_to_local +test_exec_kernel_network_to_local +exit $errno From patchwork Sat May 22 06:39:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12274353 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27B33C2B9FB for ; Sat, 22 May 2021 06:41:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2C4D60BBB for ; Sat, 22 May 2021 06:41:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229865AbhEVGmi (ORCPT ); Sat, 22 May 2021 02:42:38 -0400 Received: from mout.gmx.net ([212.227.15.19]:42431 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229689AbhEVGmi (ORCPT ); Sat, 22 May 2021 02:42:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621665640; bh=+Zh7rJ7sR7FIj5WCV0QEldYaN5NYO8mP4vWlHrrjpng=; h=X-UI-Sender-Class:Date:From:To:Cc:Subject:References:In-Reply-To; b=bkpszwsP0FGt7jbkuJYzJI4brQ6IwEb/tzH1m6Ij5ZhTxW0QVEh51ze48Rw2c8hZX RbdMkiYly6U8FeXRunKWGDs4Zfc2fdAIlvRT4ME+2DiD5VY4DG14SuXFMIm/zbEyOV 78JvWmsHZxCEmHdqDvZJ/QiHcdJClXdI4lDt3wU4= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from ubuntu ([83.52.228.41]) by mail.gmx.net (mrgmx004 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MBUqL-1lbEcq4BCx-00D3F0; Sat, 22 May 2021 08:40:40 +0200 Date: Sat, 22 May 2021 08:39:55 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 6/7] Documentation: Add documentation for the Brute LSM Message-ID: <20210522063955.GB3094@ubuntu> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> X-Provags-ID: V03:K1:zmnblJkyhWmwKEaOubT2kmnxbLxgdpuda2zvRtBo44MvhGdd9PB x7wt0u76rufAKPQ9M1yp24+m+wh5HmZ+xn4UsEoS2dhRyp92waynOnJ3L4OmHw1MaDk78X8 0oZLnOe/RvsBFp5bEHm3niyVFOt6ez8xSLrg4aZpEllIyiaUK6DDFXwWbwbhghFp0zzWcWn omTmXQtLQ+ypJ2BoL0jBw== X-UI-Out-Filterresults: notjunk:1;V03:K0:q76mp3yoqsc=:q6NtqCaZJ5KL4da3A+hNu/ j/sreBZX07fjCjUyy0+ghMhDVEG8WZyULmnVWLTwswplEuUNx+LvAuztR6mpa7QzuLwskdjcM EbDclCZsLAzfj/cbfpxfimUd8/MORFP3kgoRWXzEUpP6fAyYqA0sjkUW2iwzLHHvF0d2BXWxz 6FM3KwDMYWaQGTqdbVb5JIlnYRdKrWS4nZZ8UWSjfYK8tjYSNDAl/r3L5iBmY1sRYRunCsO04 gFm1spftNadASK31MNbmVsGugiXZ7bjJ/XXHvbD9z5EumuYurXkJNnuUXY87tzvt+RI8hpbWc 8HXhqsgAEfiUmlS+LEt8CJV4gmSjBQhrtUlLtf95AbzDXOVUIQy3umrr/jtHJkRZAoIL+FT4D rcQ/xGZmZq3bvIsuUYo8BSTRHaeTTjCnSTlAtCeTreuBg/Txml5YY+VnLeASFxoaqHdIWhUMZ lJa9dgsSAmfczlUm1MbXX1stIFYnEkPuyYrdbY72QVYMlHdqVZaZEYjqX3m2SCZLwKKWr6ABp pZ0bi+diigoUZZlrAHz1mXhjUSGN5ybWEJjf+jRzQn8WT/d0itgdg6oNAcF4ThbhWsl8eXGtx J0AYKh6XZ9RIWQBxBWhB0qesFLF8/o56mMfKyJ05mIp2ptRTdOP+n4nYhB8FV5WKCfhpJe86q znRZ4UeDQw3PHes8/jFK9/pQaZ4KD744HyMT1PpIv4+V5V7KDDwaVxknAHtEzF2O+tT1QGGjv dZ4OD6RCHw6a8BFbD4vYORibk/WaherQ0gIaI3Yk6B7YSUsQMVvnyJEwXs7I01iwv4zVfdvOe lDHjlDwhDPDrehm8zK73uNveqF1RtO5e9TF9FZr73r1ZxOaKEAGmNO8lzc40ziMknACqK7N4J ocwZ8CPKbi0nvQaDAqKkE8NI/TwFQ3q6drStPwAClA6SahDZnJ7x6171OivEDiq3JgJHNhRMc /Y9F4G0hqeUjjXLe3dev5nMvXY08U3Q27666QaEhabIuRW1ib00ssF+M+WaY/PkKjvHhl9yzY NJYLAgXIiI5NJ+7VH8EoUVcEWFBcsJoCux1OkpmAkHCPz0BZ8FF59dns9ViDCkRMArehRYc0D 7IUXF/grkE2LPq/OGoKAIYOALbCO0cSyhebnKSpk88Kw3rkvSoIIUDR0NzHL6+Q79KNXOCiuw nFOgytcNSuciE1yMX1kXYzhQ2n0jGlW3+QifUOsSKFs6RzpGOqqG1bezxG/iroewdJetE= Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add some info detailing what is the Brute LSM, its motivation, weak points of existing implementations, proposed solutions, enabling, disabling, configuration and self-tests. Signed-off-by: John Wood --- Documentation/admin-guide/LSM/Brute.rst | 334 ++++++++++++++++++++++++ Documentation/admin-guide/LSM/index.rst | 1 + security/brute/Kconfig | 3 +- 3 files changed, 337 insertions(+), 1 deletion(-) create mode 100644 Documentation/admin-guide/LSM/Brute.rst -- 2.25.1 diff --git a/Documentation/admin-guide/LSM/Brute.rst b/Documentation/admin-guide/LSM/Brute.rst new file mode 100644 index 000000000000..97c9aac33093 --- /dev/null +++ b/Documentation/admin-guide/LSM/Brute.rst @@ -0,0 +1,334 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===== +Brute +===== + +Brute is a Linux Security Module that detects and mitigates fork brute force +attacks against vulnerable userspace processes. + + +Motivation +========== + +Attacks against vulnerable userspace applications with the purpose to break ASLR +or bypass canaries traditionally use some level of brute force with the help of +the fork system call. This is possible since when creating a new process using +fork its memory contents are the same as those of the parent process (the +process that called the fork system call). So, the attacker can test the memory +infinite times to find the correct memory values or the correct memory addresses +without worrying about crashing the application. + +Based on the above scenario it would be nice to have this detected and +mitigated, and this is the goal of this implementation. Specifically the +following attacks are expected to be detected: + + 1. Launching (fork()/exec()) a setuid/setgid process repeatedly until a + desirable memory layout is got (e.g. Stack Clash). + 2. Connecting to an exec()ing network daemon (e.g. xinetd) repeatedly until a + desirable memory layout is got (e.g. what CTFs do for simple network + service). + 3. Launching processes without exec() (e.g. Android Zygote) and exposing state + to attack a sibling. + 4. Connecting to a fork()ing network daemon (e.g. apache) repeatedly until the + previously shared memory layout of all the other children is exposed (e.g. + kind of related to HeartBleed). + +In each case, a privilege boundary has been crossed: + + | Case 1: setuid/setgid process + | Case 2: network to local + | Case 3: privilege changes + | Case 4: network to local + +So, what really needs to be detected are fork/exec brute force attacks that +cross any of the commented bounds. + + +Other implementations +===================== + +The public version of grsecurity, as a summary, is based on the idea of delaying +the fork system call if a child died due to some fatal signal (``SIGSEGV``, +``SIGBUS``, ``SIGKILL`` or ``SIGILL``). This has some issues: + +Bad practices +------------- + +Adding delays to the kernel is, in general, a bad idea. + +Scenarios not detected (false negatives) +---------------------------------------- + +This protection acts only when the fork system call is called after a child has +crashed. So, it would still be possible for an attacker to fork a big amount of +children (in the order of thousands), then probe all of them, and finally wait +the protection time before repeating the steps. + +Moreover, this method is based on the idea that the protection doesn't act if +the parent crashes. So, it would still be possible for an attacker to fork a +process and probe itself. Then, fork the child process and probe itself again. +This way, these steps can be repeated infinite times without any mitigation. + +Scenarios detected (false positives) +------------------------------------ + +Scenarios where an application rarely fails for reasons unrelated to a real +attack. + + +This implementation +=================== + +The main idea behind this implementation is to improve the existing ones +focusing on the weak points annotated before. Basically, the adopted solution is +to detect a fast crash rate instead of only one simple crash and to detect both +the crash of parent and child processes. Also, fine tune the detection focusing +on privilege boundary crossing. And finally, as a mitigation method, kill all +the offending tasks involved in the attack and mark the executable as "not +allowed" (to block the following executions) instead of using delays. + +To achieve this goal, and going into more details, this implementation is based +on the use of some statistical data shared across all the processes that can +have the same memory contents. Or in other words, a statistical data shared +between all the fork hierarchy processes after an execve system call. + +The purpose of these statistics is, basically, collect all the necessary info to +compute the application crash period in order to detect an attack. To track all +this information, the extended attributes (xattr) of the executable files are +used. More specifically, the name of the attribute is "brute" and uses the +"security" namespace. So, the full xattr name for the Brute LSM is: + + ``security.brute`` + +The same can be achieved using a pointer to the fork hierarchy statistical data +held by the ``task_struct`` structure, but this has an important drawback: a +brute force attack that happens through the execve system call losts the faults +info since these statistics are freed when the fork hierarchy disappears. Using +the last method (pointer in the ``task_struct`` structure) makes not possible to +manage this attack type that can be successfully treated using extended +attributes. + +To detect a brute force attack it is necessary that the statistics shared by all +the fork hierarchy processes be updated in every fatal crash and the most +important data to update is the application crash period. + +The crash period is the time between two consecutive faults, but this also has a +drawback: if an application crashes twice in a short period of time for some +reason unrelated to a real attack, a false positive will be triggered. To avoid +this scenario the exponential moving average (EMA) is used. This way, the +application crash period will be a value that is not prone to change due to +spurious data and follows the real crash period. + +These statistics are stored in the executables using the extended attributes +feature. So, the detection and mitigation of brute force attacks using this LSM +it is only feasible in filesystems that support xattr. + +.. kernel-doc:: security/brute/brute.c + :identifiers: brute_raw_stats + +This is a fixed sized struct with a very small footprint. So, in reference to +memory usage, it is not expected to have problems storing it as an extended +attribute. + +Concerning to access rights to this statistical data, as stated above, the +"security" namespace is used. Since no custom policy, related to this extended +attribute, has been implemented for the Brute LSM, all processes have read +access to these statistics, and write access is limited to processes that have +the ``CAP_SYS_ADMIN`` capability. + +Attack detection +---------------- + +There are two types of brute force attacks that need to be detected. The first +one is an attack that happens through the fork system call and the second one is +an attack that happens through the execve system call. Moreover, these two +attack types have two variants. A slow brute force attack that is detected if a +maximum number of faults per fork hierarchy is reached and a fast brute force +attack that is detected if the application crash period falls below a certain +threshold. + +Attack mitigation +----------------- + +Once an attack has been detected, this is mitigated killing all the offending +tasks involved. Or in other words, once an attack has been detected, this is +mitigated killing all the processes that are executing the same file that is +running during the brute force attack. Also, to prevent the executable involved +in the attack from being respawned by a supervisor, and thus prevent a brute +force attack from being started again, the file is marked as "not allowed" and +the following executions are avoided based on this mark. This method allows +supervisors to implement their own policy: they can read the statistics, know if +the executable is blocked by the Brute LSM and why, and act based on this +information. If they want to respawn the offending executable it is only +necessary to remove the "``security.brute``" extended attribute and thus remove +the statistical data. + +Fine tuning the attack detection +-------------------------------- + +To avoid false positives during the attack detection it is necessary to narrow +the possible cases. To do so, and based on the threat scenarios that we want to +detect, this implementation also focuses on the crossing of privilege bounds. + +To be precise, only the following privilege bounds are taken into account: + + 1. setuid/setgid process + 2. network to local + 3. privilege changes + +Moreover, only the fatal signals delivered by the kernel are taken into account +avoiding the fatal signals sent by userspace applications (with the exception of +the ``SIGABRT`` user signal since this is used by glibc for stack canary, +malloc, etc. failures, which may indicate that a mitigation has been triggered). + +Exponential moving average (EMA) +-------------------------------- + +This kind of average defines a weight (between 0 and 1) for the new value to add +and applies the remainder of the weight to the current average value. This way, +some spurious data will not excessively modify the average and only if the new +values are persistent, the moving average will tend towards them. + +Mathematically the application crash period's EMA can be expressed as follows: + + period_ema = period * weight + period_ema * (1 - weight) + +Related to the attack detection, the EMA must guarantee that not many crashes +are needed. To demonstrate this, the scenario where an application has failed +and then has been running without any crashes for a month, will be used. + +The period's EMA can be written now as: + + period_ema[i] = period[i] * weight + period_ema[i - 1] * (1 - weight) + +If the new crash periods have insignificant values related to the first crash +period (a month in this case), the formula can be rewritten as: + + period_ema[i] = period_ema[i - 1] * (1 - weight) + +And by extension: + + | period_ema[i - 1] = period_ema[i - 2] * (1 - weight) + | period_ema[i - 2] = period_ema[i - 3] * (1 - weight) + | period_ema[i - 3] = period_ema[i - 4] * (1 - weight) + +So, if the substitution is made: + + | period_ema[i] = period_ema[i - 1] * (1 - weight) + | period_ema[i] = period_ema[i - 2] * (1 - weight)\ :sup:`2` + | period_ema[i] = period_ema[i - 3] * (1 - weight)\ :sup:`3` + | period_ema[i] = period_ema[i - 4] * (1 - weight)\ :sup:`4` + +And in a more generic form: + + period_ema[i] = period_ema[i - n] * (1 - weight)\ :sup:`n` + +Where "n" represents the number of iterations to obtain an EMA value. Or in +other words, the number of crashes to detect an attack. + +So, if we isolate the number of crashes: + + | period_ema[i] / period_ema[i - n] = (1 - weight)\ :sup:`n` + | log(period_ema[i] / period_ema[i - n]) = log((1 - weight)\ :sup:`n`) + | log(period_ema[i] / period_ema[i - n]) = n * log(1 - weight) + | n = log(period_ema[i] / period_ema[i - n]) / log(1 - weight) + +Then, in the commented scenario (an application has failed and then has been +running without any crashes for a month), the approximate number of crashes to +detect an attack (using the default implementation values for the weight and the +crash period threshold) is: + + | weight = 7 / 10 + | crash_period_threshold = 30 seconds + + | n = log(crash_period_threshold / seconds_per_month) / log(1 - weight) + | n = log(30 / (30 * 24 * 3600)) / log(1 - 0.7) + | n = 9.44 + +So, with 10 crashes for this scenario an attack will be detected. If these steps +are repeated for different scenarios and the results are collected: + + ======================== ===================================== + time without any crashes number of crashes to detect an attack + ======================== ===================================== + 1 month 9.44 + 1 year 11.50 + 10 years 13.42 + ======================== ===================================== + +However, this computation has a drawback. The first data added to the EMA not +obtains a real average showing a trend. So the solution is simple, the EMA needs +a minimum number of data to be able to be interpreted. This way, the case where +a few first faults are fast enough followed by no crashes is avoided. + +Per system enabling/disabling +----------------------------- + +This feature can be enabled at build time using the +``CONFIG_SECURITY_FORK_BRUTE`` option or using the visual config application +under the following menu: + + Security options ``--->`` Fork brute force attack detection and mitigation + +Also, at boot time, this feature can be disable too, by changing the "``lsm=``" +boot parameter. + +Per system configuration +------------------------ + +To customize the detection's sensibility there are five new sysctl attributes +for the Brute LSM that are accessible through the following path: + + ``/proc/sys/kernel/brute/`` + +More specifically, the files and their description are: + +**ema_weight_numerator** + + .. kernel-doc:: security/brute/brute.c + :doc: brute_ema_weight_numerator + +**ema_weight_denominator** + + .. kernel-doc:: security/brute/brute.c + :doc: brute_ema_weight_denominator + +**max_faults** + + .. kernel-doc:: security/brute/brute.c + :doc: brute_max_faults + +**min_faults** + + .. kernel-doc:: security/brute/brute.c + :doc: brute_min_faults + +**crash_period_threshold** + + .. kernel-doc:: security/brute/brute.c + :doc: brute_crash_period_threshold + +Kernel selftests +---------------- + +To validate all the expectations about this implementation, there is a set of +selftests. This tests cover fork/exec brute force attacks crossing the following +privilege boundaries: + + 1. setuid process + 2. privilege changes + 3. network to local + +Also, there are some tests to check that fork/exec brute force attacks without +crossing any privilege boundariy already commented doesn't trigger the detection +and mitigation stage. + +To build the tests: + ``make -C tools/testing/selftests/ TARGETS=brute`` + +To run the tests: + ``make -C tools/testing/selftests TARGETS=brute run_tests`` + +To package the tests: + ``make -C tools/testing/selftests TARGETS=brute gen_tar`` diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst index a6ba95fbaa9f..1f68982bb330 100644 --- a/Documentation/admin-guide/LSM/index.rst +++ b/Documentation/admin-guide/LSM/index.rst @@ -41,6 +41,7 @@ subdirectories. :maxdepth: 1 apparmor + Brute LoadPin SELinux Smack diff --git a/security/brute/Kconfig b/security/brute/Kconfig index 5da314d221aa..d2dd33b08642 100644 --- a/security/brute/Kconfig +++ b/security/brute/Kconfig @@ -9,6 +9,7 @@ config SECURITY_FORK_BRUTE offending tasks are killed. Also, the executable file involved in the attack will be marked as "not allowed" and new execve system calls using this file will fail. Like capabilities, this security module - stacks with other LSMs. + stacks with other LSMs. Further information can be found in + Documentation/admin-guide/LSM/Brute.rst. If you are unsure how to answer this question, answer N. From patchwork Sat May 22 06:44:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Wood X-Patchwork-Id: 12274363 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88FBBC2B9F2 for ; Sat, 22 May 2021 06:45:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61A5C61244 for ; Sat, 22 May 2021 06:45:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230028AbhEVGrB (ORCPT ); Sat, 22 May 2021 02:47:01 -0400 Received: from mout.gmx.net ([212.227.17.20]:50251 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230023AbhEVGrB (ORCPT ); Sat, 22 May 2021 02:47:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1621665887; bh=VAC/sk0xnp5/8Dxu21k60Pq40+L7HSTTvV7xE1S71qk=; h=X-UI-Sender-Class:Date:From:To:Cc:Subject:References:In-Reply-To; b=kxLjaGcf/HX23OftpEm+6sritLglo0AJ45GakM1jc1YboXyCPIE1zu2pBrBBoE5NT 1fqsiJO7EyU12F51Xv/D9sskzu26JWVAA9tWdgotTu26ImpzXgRKwLCop5d8MfRtCJ Y811fxZ7pPkEgrwMdW+Mbz/14xgqSjDdJpbqxS8g= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from ubuntu ([83.52.228.41]) by mail.gmx.net (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1MKKYx-1m1jdI0WBb-00Llfl; Sat, 22 May 2021 08:44:47 +0200 Date: Sat, 22 May 2021 08:44:42 +0200 From: John Wood To: Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan Cc: John Wood , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v7 7/7] MAINTAINERS: Add a new entry for the Brute LSM Message-ID: <20210522064442.GC3094@ubuntu> References: <20210521172414.69456-1-john.wood@gmx.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210521172414.69456-1-john.wood@gmx.com> X-Provags-ID: V03:K1:EaW59w+taFdVkQq3IT0Sp5BLroZB2cj3eMLYXxy5NmqL+Du6Lr5 6xRDEefEotMQ+jKUXkh9C8PDTCFycM9VbtpMNWx+Y8QLFTqh/ZJxJHoLi7fmxSynxmsUFUz U2r5cjPhEsbNU3BBT1GbxkVQrplQ507I/eJS0e/VEmxEI3Ebz0+q9+XhdYefGrTy0g8cRqb /lxZtdJNXzBAYnDEaMuAQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:K2xzrztLlUg=:SBYCa464E05P8CoolV05rm 8Z2ezmGEBvuhJMCbP3aBr6cxqcW24SVY3SrHLHeNd1Q5fC8aIXobpIPyObN1KU/ktvwPdktXq iQYkH7TuTBiCC7A0whAvncUWF3v0LqV05ZY+5NG/Osi2n8LAz+TeVoFwHq9dmbFOfST0O7s7e CuSIq/e3NfpJ4gF7Gu8cqLH0khzq0gJrqgAcd+bWkTWpI2sWTTQs47Y7NmMLbNdME7GHyyR9G Le1edo0tflCFSsED9K46WOLZVWRsI74/rofb6gkylK+EYeYRsUkprRnWyP2FEVwWlD07ngO6L rqUQYoCx9J5JY6taF/9kN8Lvh5IrdmtAD+yyZqeHFKHWRC+7zttQ67mYyImVYV2vZGdxRV8sj bDnHZNVjlhqkF3m16kz5KsMiHTUpmCBDVMOhdo0Bt+dB5xz0/aqwgnrXCQBQJ/AZGm5j3Zwl6 9kLs1E/g217N8gNquDP4r9olHDXnMpE4inalw1r6skqQQFQ+NLPMWI0gfigZ7nOAd8aZl0253 n2Vp4czU+Vy5ivpKegDqXu41WqWLzksURF7wmewbVY0mwJlOZytlS6nXSGwDp97yOYW9YPYJ3 8uumpuAwf8sifNRrVvh6urC5dejg40Vl9Hdmg238yJ6VByT/j4eO1rvQq/pU4T+B/47OhXZ8n TT+G8QXVz/o6/UR7ugbTs4KAy1stOEyKBKf7oQmslajuA4lNgUzjVoSREb0FBmXtQGK4JvX84 xYUrR0Fm2zEMRftgYnAToF0EjO4qOEUSeiNFMeamiCPuJoXRXw6vf79M1iW288zmn+lR2ACTy ZvuCWTCMU/ztR2OqQ+xY0S39ZDUp03FoDmr3JbUXywwb/TBVgqPreIHh/z6OG13ALuc6HiUd7 Q1yrT/d6G4fYZ3O0/3Wog/bTEXLPXLubviY3+LMVDpGtBaY6TxyEE4bf4YJkHbNdn2Pb9Q2s3 8DsCwU7hNZ8P0NBDWWNDXGz3NbEvF8JQNXM/oD2WpQaRakLNc6fZQfSXvIpP3YrzZ9eolifbL ddvSRUJhUXN0RnMcYU/FtnYRSE7NIglWujtGi3Usbv0DH9MRpecxwAR+5FRvC8nnwtMr1Qhut e6Djays4Mgl/qDBsPX/CXwQfWpiwyr6WhNO Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org In order to maintain the code for the Brute LSM add a new entry to the maintainers list. Signed-off-by: John Wood --- MAINTAINERS | 7 +++++++ 1 file changed, 7 insertions(+) -- 2.25.1 diff --git a/MAINTAINERS b/MAINTAINERS index 008fcad7ac00..102eb3d7dcd6 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3847,6 +3847,13 @@ L: netdev@vger.kernel.org S: Supported F: drivers/net/ethernet/brocade/bna/ +BRUTE SECURITY MODULE +M: John Wood +S: Maintained +F: Documentation/admin-guide/LSM/Brute.rst +F: security/brute/ +F: tools/testing/selftests/brute/ + BSG (block layer generic sg v4 driver) M: FUJITA Tomonori L: linux-scsi@vger.kernel.org