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l0kodJames Morris
l0kod
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James Morris
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landlock: Set up the security framework and manage credentials
Process's credentials point to a Landlock domain, which is underneath implemented with a ruleset. In the following commits, this domain is used to check and enforce the ptrace and filesystem security policies. A domain is inherited from a parent to its child the same way a thread inherits a seccomp policy. Cc: James Morris <jmorris@namei.org> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Reviewed-by: Jann Horn <jannh@google.com> Acked-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210422154123.13086-4-mic@digikod.net Signed-off-by: James Morris <jamorris@linux.microsoft.com>
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‎security/Kconfig‎

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@@ -278,11 +278,11 @@ endchoice
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config LSM
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string "Ordered list of enabled LSMs"
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default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
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default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
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default "lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
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default "lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
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default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
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default "landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
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default "landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
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default "landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
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default "landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
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default "landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
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help
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A comma-separated list of LSMs, in initialization order.
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Any LSMs left off this list will be ignored. This can be

‎security/landlock/Makefile‎

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obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
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landlock-y := object.o ruleset.o
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landlock-y := setup.o object.o ruleset.o \
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cred.o

‎security/landlock/common.h‎

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock LSM - Common constants and helpers
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#ifndef _SECURITY_LANDLOCK_COMMON_H
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#define _SECURITY_LANDLOCK_COMMON_H
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#define LANDLOCK_NAME "landlock"
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#ifdef pr_fmt
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#undef pr_fmt
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#endif
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#define pr_fmt(fmt) LANDLOCK_NAME ": " fmt
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#endif /* _SECURITY_LANDLOCK_COMMON_H */

‎security/landlock/cred.c‎

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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Landlock LSM - Credential hooks
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*
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* Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#include <linux/cred.h>
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#include <linux/lsm_hooks.h>
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#include "common.h"
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#include "cred.h"
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#include "ruleset.h"
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#include "setup.h"
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static int hook_cred_prepare(struct cred *const new,
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const struct cred *const old, const gfp_t gfp)
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{
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struct landlock_ruleset *const old_dom = landlock_cred(old)->domain;
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if (old_dom) {
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landlock_get_ruleset(old_dom);
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landlock_cred(new)->domain = old_dom;
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}
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return 0;
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}
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static void hook_cred_free(struct cred *const cred)
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{
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struct landlock_ruleset *const dom = landlock_cred(cred)->domain;
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if (dom)
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landlock_put_ruleset_deferred(dom);
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}
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static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
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LSM_HOOK_INIT(cred_prepare, hook_cred_prepare),
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LSM_HOOK_INIT(cred_free, hook_cred_free),
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};
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__init void landlock_add_cred_hooks(void)
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{
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security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
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LANDLOCK_NAME);
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}

‎security/landlock/cred.h‎

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock LSM - Credential hooks
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*
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* Copyright © 2019-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2019-2020 ANSSI
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*/
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#ifndef _SECURITY_LANDLOCK_CRED_H
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#define _SECURITY_LANDLOCK_CRED_H
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#include <linux/cred.h>
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#include <linux/init.h>
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#include <linux/rcupdate.h>
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#include "ruleset.h"
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#include "setup.h"
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struct landlock_cred_security {
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struct landlock_ruleset *domain;
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};
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static inline struct landlock_cred_security *landlock_cred(
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const struct cred *cred)
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{
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return cred->security + landlock_blob_sizes.lbs_cred;
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}
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static inline const struct landlock_ruleset *landlock_get_current_domain(void)
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{
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return landlock_cred(current_cred())->domain;
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}
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/*
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* The call needs to come from an RCU read-side critical section.
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*/
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static inline const struct landlock_ruleset *landlock_get_task_domain(
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const struct task_struct *const task)
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{
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return landlock_cred(__task_cred(task))->domain;
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}
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static inline bool landlocked(const struct task_struct *const task)
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{
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bool has_dom;
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if (task == current)
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return !!landlock_get_current_domain();
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rcu_read_lock();
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has_dom = !!landlock_get_task_domain(task);
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rcu_read_unlock();
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return has_dom;
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}
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__init void landlock_add_cred_hooks(void);
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#endif /* _SECURITY_LANDLOCK_CRED_H */

‎security/landlock/setup.c‎

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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Landlock LSM - Security framework setup
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#include <linux/init.h>
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#include <linux/lsm_hooks.h>
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#include "common.h"
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#include "cred.h"
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#include "setup.h"
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struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = {
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.lbs_cred = sizeof(struct landlock_cred_security),
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};
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static int __init landlock_init(void)
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{
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landlock_add_cred_hooks();
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pr_info("Up and running.\n");
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return 0;
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}
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DEFINE_LSM(LANDLOCK_NAME) = {
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.name = LANDLOCK_NAME,
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.init = landlock_init,
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.blobs = &landlock_blob_sizes,
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};

‎security/landlock/setup.h‎

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock LSM - Security framework setup
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#ifndef _SECURITY_LANDLOCK_SETUP_H
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#define _SECURITY_LANDLOCK_SETUP_H
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#include <linux/lsm_hooks.h>
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extern struct lsm_blob_sizes landlock_blob_sizes;
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#endif /* _SECURITY_LANDLOCK_SETUP_H */

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