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>
This commit is contained in:
Mickaël Salaün 2021-04-22 17:41:13 +02:00 коммит произвёл James Morris
Родитель ae271c1b14
Коммит 385975dca5
7 изменённых файлов: 178 добавлений и 6 удалений

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

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@ -1,3 +1,4 @@
obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
landlock-y := object.o ruleset.o
landlock-y := setup.o object.o ruleset.o \
cred.o

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@ -0,0 +1,20 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Landlock LSM - Common constants and helpers
*
* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
*/
#ifndef _SECURITY_LANDLOCK_COMMON_H
#define _SECURITY_LANDLOCK_COMMON_H
#define LANDLOCK_NAME "landlock"
#ifdef pr_fmt
#undef pr_fmt
#endif
#define pr_fmt(fmt) LANDLOCK_NAME ": " fmt
#endif /* _SECURITY_LANDLOCK_COMMON_H */

46
security/landlock/cred.c Normal file
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@ -0,0 +1,46 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* Landlock LSM - Credential hooks
*
* Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
*/
#include <linux/cred.h>
#include <linux/lsm_hooks.h>
#include "common.h"
#include "cred.h"
#include "ruleset.h"
#include "setup.h"
static int hook_cred_prepare(struct cred *const new,
const struct cred *const old, const gfp_t gfp)
{
struct landlock_ruleset *const old_dom = landlock_cred(old)->domain;
if (old_dom) {
landlock_get_ruleset(old_dom);
landlock_cred(new)->domain = old_dom;
}
return 0;
}
static void hook_cred_free(struct cred *const cred)
{
struct landlock_ruleset *const dom = landlock_cred(cred)->domain;
if (dom)
landlock_put_ruleset_deferred(dom);
}
static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(cred_prepare, hook_cred_prepare),
LSM_HOOK_INIT(cred_free, hook_cred_free),
};
__init void landlock_add_cred_hooks(void)
{
security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
LANDLOCK_NAME);
}

58
security/landlock/cred.h Normal file
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@ -0,0 +1,58 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Landlock LSM - Credential hooks
*
* Copyright © 2019-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2019-2020 ANSSI
*/
#ifndef _SECURITY_LANDLOCK_CRED_H
#define _SECURITY_LANDLOCK_CRED_H
#include <linux/cred.h>
#include <linux/init.h>
#include <linux/rcupdate.h>
#include "ruleset.h"
#include "setup.h"
struct landlock_cred_security {
struct landlock_ruleset *domain;
};
static inline struct landlock_cred_security *landlock_cred(
const struct cred *cred)
{
return cred->security + landlock_blob_sizes.lbs_cred;
}
static inline const struct landlock_ruleset *landlock_get_current_domain(void)
{
return landlock_cred(current_cred())->domain;
}
/*
* The call needs to come from an RCU read-side critical section.
*/
static inline const struct landlock_ruleset *landlock_get_task_domain(
const struct task_struct *const task)
{
return landlock_cred(__task_cred(task))->domain;
}
static inline bool landlocked(const struct task_struct *const task)
{
bool has_dom;
if (task == current)
return !!landlock_get_current_domain();
rcu_read_lock();
has_dom = !!landlock_get_task_domain(task);
rcu_read_unlock();
return has_dom;
}
__init void landlock_add_cred_hooks(void);
#endif /* _SECURITY_LANDLOCK_CRED_H */

31
security/landlock/setup.c Normal file
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@ -0,0 +1,31 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* Landlock LSM - Security framework setup
*
* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
*/
#include <linux/init.h>
#include <linux/lsm_hooks.h>
#include "common.h"
#include "cred.h"
#include "setup.h"
struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = {
.lbs_cred = sizeof(struct landlock_cred_security),
};
static int __init landlock_init(void)
{
landlock_add_cred_hooks();
pr_info("Up and running.\n");
return 0;
}
DEFINE_LSM(LANDLOCK_NAME) = {
.name = LANDLOCK_NAME,
.init = landlock_init,
.blobs = &landlock_blob_sizes,
};

16
security/landlock/setup.h Normal file
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@ -0,0 +1,16 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Landlock LSM - Security framework setup
*
* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
*/
#ifndef _SECURITY_LANDLOCK_SETUP_H
#define _SECURITY_LANDLOCK_SETUP_H
#include <linux/lsm_hooks.h>
extern struct lsm_blob_sizes landlock_blob_sizes;
#endif /* _SECURITY_LANDLOCK_SETUP_H */