[RFC PATCH v7 01/16] security: add ipe lsm & initial context creation

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; Integrity Policy Enforcement (IPE) is an LSM that provides an complimentary approach to Mandatory Access Control than existing LSMs today. Existing LSMs have centered around the concept of access to a resource should be controlled by the current user's credentials. IPE's approach, is that access to a resource should be controlled by the system's trust of a current resource. The basis of this approach is that every process in the kernel is associated with a context that determines the policy for what is trusted by said process and its descendents, starting with 'init'. Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Split up patch 02/11 into three parts: 1. context creation (new) [this patch] 2. parser (refactored) 3. evaluation loop * Refactor series to: 1. Support a context structure, enabling easier testing --- MAINTAINERS | 6 ++ security/Kconfig | 11 +-- security/Makefile | 1 + security/ipe/Kconfig | 19 +++++ security/ipe/Makefile | 11 +++ security/ipe/ctx.c | 161 ++++++++++++++++++++++++++++++++++++++++++ security/ipe/ctx.h | 28 ++++++++ security/ipe/hooks.c | 58 +++++++++++++++ security/ipe/hooks.h | 16 +++++ security/ipe/ipe.c | 57 +++++++++++++++ security/ipe/ipe.h | 19 +++++ 11 files changed, 382 insertions(+), 5 deletions(-) create mode 100644 security/ipe/Kconfig create mode 100644 security/ipe/Makefile create mode 100644 security/ipe/ctx.c create mode 100644 security/ipe/ctx.h create mode 100644 security/ipe/hooks.c create mode 100644 security/ipe/hooks.h create mode 100644 security/ipe/ipe.c create mode 100644 security/ipe/ipe.h diff --git a/MAINTAINERS b/MAINTAINERS index e0bca0de0df7..f1e76f791d47 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9279,6 +9279,12 @@ S: Supported T: git git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git F: security/integrity/ima/ +INTEGRITY POLICY ENFORCEMENT (IPE) +M: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; +M: Fan Wu <wufan(a)linux.microsoft.com&gt; +S: Supported +F: security/ipe/ + INTEL 810/815 FRAMEBUFFER DRIVER M: Antonino Daplas <adaplas(a)gmail.com&gt; L: linux-fbdev(a)vger.kernel.org diff --git a/security/Kconfig b/security/Kconfig index 0ced7fd33e4d..6ed9b3b5a75c 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -239,6 +239,7 @@ source "security/yama/Kconfig" source "security/safesetid/Kconfig" source "security/lockdown/Kconfig" source "security/landlock/Kconfig" +source "security/ipe/Kconfig" source "security/integrity/Kconfig" @@ -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,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf,ipe" if DEFAULT_SECURITY_SMACK + default "landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf,ipe" if DEFAULT_SECURITY_APPARMOR + default "landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf,ipe" if DEFAULT_SECURITY_TOMOYO + default "landlock,lockdown,yama,loadpin,safesetid,integrity,bpf,ipe" if DEFAULT_SECURITY_DAC + default "landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf,ipe" 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 18121f8f85cd..527b1864d96c 100644 --- a/security/Makefile +++ b/security/Makefile @@ -24,6 +24,7 @@ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ obj-$(CONFIG_CGROUPS) += device_cgroup.o obj-$(CONFIG_BPF_LSM) += bpf/ obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ +obj-$(CONFIG_SECURITY_IPE) += ipe/ # Object integrity file lists obj-$(CONFIG_INTEGRITY) += integrity/ diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig new file mode 100644 index 000000000000..c4503083e92d --- /dev/null +++ b/security/ipe/Kconfig @@ -0,0 +1,19 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Integrity Policy Enforcement (IPE) configuration +# + +menuconfig SECURITY_IPE + bool "Integrity Policy Enforcement (IPE)" + depends on SECURITY && SECURITYFS + select PKCS7_MESSAGE_PARSER + select SYSTEM_DATA_VERIFICATION + help + This option enables the Integrity Policy Enforcement subsystem + allowing systems to enforce integrity having no dependencies + on filesystem metadata, making its decisions based off of kernel- + resident features and data structures. A key feature of IPE is a + customizable policy to allow admins to reconfigure integrity + requirements on the fly. + + If unsure, answer N. diff --git a/security/ipe/Makefile b/security/ipe/Makefile new file mode 100644 index 000000000000..ba3df729e252 --- /dev/null +++ b/security/ipe/Makefile @@ -0,0 +1,11 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) Microsoft Corporation. All rights reserved. +# +# Makefile for building the IPE module as part of the kernel tree. +# + +obj-$(CONFIG_SECURITY_IPE) += \ + ctx.o \ + hooks.o \ + ipe.o \ diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c new file mode 100644 index 000000000000..c24f5d1d41bd --- /dev/null +++ b/security/ipe/ctx.c @@ -0,0 +1,161 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "ctx.h" + +#include <linux/slab.h> +#include <linux/types.h> +#include <linux/parser.h> +#include <linux/refcount.h> +#include <linux/spinlock.h> + +/** + * ipe_current_ctx: Helper to retrieve the ipe_context for the current task. + * + * Return: + * See ipe_get_ctx_rcu + */ +struct ipe_context *ipe_current_ctx(void) +{ + return ipe_get_ctx_rcu(*ipe_tsk_ctx(current)); +} + +/** + * ipe_tsk_ctx: Retrieve the RCU-protected address of the task + * that contains the ipe_context. + * @tsk: Task to retrieve the address from. + * + * Callers need to use the rcu* family functions to interact with + * the ipe_context, or ipe_get_ctx_rcu. + * + * Return: + * Valid Address to a location containing an RCU-protected ipe_context. + */ +struct ipe_context __rcu **ipe_tsk_ctx(struct task_struct *tsk) +{ + return tsk->security + ipe_blobs.lbs_task; +} + +/** + * ipe_get_ctx_rcu: Retrieve the underlying ipe_context in an rcu protected + * address space. + * @ctx: Context to dereference. + * + * This function will increment the reference count of the dereferenced + * ctx, ensuring that it is valid outside of the rcu_read_lock. + * + * However, if a context has a reference count of 0 (and thus being) + * freed, this API will return NULL. + * + * Return: + * !NULL - Valid context + * NULL - the dereferenced context will not exist outside after the + * next grace period. + */ +struct ipe_context *ipe_get_ctx_rcu(struct ipe_context __rcu *ctx) +{ + struct ipe_context *rv = NULL; + + rcu_read_lock(); + + rv = rcu_dereference(ctx); + if (!rv || !refcount_inc_not_zero(&rv->refcount)) + rv = NULL; + + rcu_read_unlock(); + + return rv; +} + +/** + * free_ctx_work: Worker function to deallocate a context structure. + * @work: work_struct passed to schedule_work + */ +static void free_ctx_work(struct work_struct *const work) +{ + struct ipe_context *ctx = NULL; + + ctx = container_of(work, struct ipe_context, free_work); + + kfree(ctx); +} + +/** + * create_ctx: Allocate a context structure. + * + * The reference count at this point will be set to 1. + * + * Return: + * !IS_ERR - OK + * ERR_PTR(-ENOMEM) - Lack of memory. + */ +static struct ipe_context *create_ctx(void) +{ + int rc = 0; + struct ipe_context *ctx = NULL; + + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); + if (!ctx) { + rc = -ENOMEM; + goto err; + } + + INIT_WORK(&ctx->free_work, free_ctx_work); + refcount_set(&ctx->refcount, 1); + spin_lock_init(&ctx->lock); + + return ctx; + +err: + ipe_put_ctx(ctx); + return ERR_PTR(rc); +} + +/** + * ipe_put_ns: Decrement the reference of an ipe_context structure, + * scheduling a free as necessary.s + * @ctx: Structure to free + * + * This function no-ops on error and null values for @ctx, and the + * deallocation will only occur if the refcount is 0. + */ +void ipe_put_ctx(struct ipe_context *ctx) +{ + if (IS_ERR_OR_NULL(ctx) || !refcount_dec_and_test(&ctx->refcount)) + return; + + schedule_work(&ctx->free_work); +} + +/** + * ipe_init_ctx: Initialize the init context. + * + * This is called at LSM init, and marks the kernel init process + * with a context. All processes descendent from kernel + * init will inherit this context. + * + * Return: + * 0 - OK + * -ENOMEM: Not enough memory to allocate the init context. + */ +int __init ipe_init_ctx(void) +{ + int rc = 0; + struct ipe_context *lns = NULL; + + lns = create_ctx(); + if (IS_ERR(lns)) { + rc = PTR_ERR(lns); + goto err; + } + + rcu_assign_pointer(*ipe_tsk_ctx(current), lns); + + return 0; +err: + ipe_put_ctx(lns); + return rc; +} diff --git a/security/ipe/ctx.h b/security/ipe/ctx.h new file mode 100644 index 000000000000..69a2c92c0a8c --- /dev/null +++ b/security/ipe/ctx.h @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_CONTEXT_H +#define IPE_CONTEXT_H + +#include <linux/sched.h> +#include <linux/types.h> +#include <linux/refcount.h> +#include <linux/spinlock.h> +#include <linux/workqueue.h> + +struct ipe_context { + refcount_t refcount; + /* Protects concurrent writers */ + spinlock_t lock; + + struct work_struct free_work; +}; + +int __init ipe_init_ctx(void); +struct ipe_context __rcu **ipe_tsk_ctx(struct task_struct *tsk); +struct ipe_context *ipe_current_ctx(void); +struct ipe_context *ipe_get_ctx_rcu(struct ipe_context __rcu *ctx); +void ipe_put_ctx(struct ipe_context *ctx); + +#endif /* IPE_CONTEXT_H */ diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c new file mode 100644 index 000000000000..ed0c886eaa5a --- /dev/null +++ b/security/ipe/hooks.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "ctx.h" +#include "hooks.h" + +#include <linux/sched.h> +#include <linux/types.h> +#include <linux/refcount.h> +#include <linux/rcupdate.h> + +/** + * ipe_task_alloc: Assign a new context for an associated task structure. + * @task: Supplies the task structure to assign a context to. + * @clone_flags: unused. + * + * The context assigned is always the context of the current task. + * Reference counts are dropped by ipe_task_free + * + * Return: + * 0 - OK + * -ENOMEM - Out of Memory + */ +int ipe_task_alloc(struct task_struct *task, unsigned long clone_flags) +{ + struct ipe_context __rcu **ctx = NULL; + struct ipe_context *current_ctx = NULL; + + current_ctx = ipe_current_ctx(); + ctx = ipe_tsk_ctx(task); + rcu_assign_pointer(*ctx, current_ctx); + refcount_inc(&current_ctx->refcount); + + ipe_put_ctx(current_ctx); + return 0; +} + +/** + * ipe_task_free: Drop a reference to an ipe_context associated with @task. + * If there are no tasks remaining, the context is freed. + * @task: Supplies the task to drop an ipe_context reference to. + */ +void ipe_task_free(struct task_struct *task) +{ + struct ipe_context *ctx; + + /* + * This reference was the initial creation, no need to increment + * refcount + */ + rcu_read_lock(); + ctx = rcu_dereference(*ipe_tsk_ctx(task)); + ipe_put_ctx(ctx); + rcu_read_unlock(); +} diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h new file mode 100644 index 000000000000..e0ae3c7dfb5b --- /dev/null +++ b/security/ipe/hooks.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_HOOKS_H +#define IPE_HOOKS_H + +#include <linux/types.h> +#include <linux/sched.h> + +int ipe_task_alloc(struct task_struct *task, + unsigned long clone_flags); + +void ipe_task_free(struct task_struct *task); + +#endif /* IPE_HOOKS_H */ diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c new file mode 100644 index 000000000000..d600346702e5 --- /dev/null +++ b/security/ipe/ipe.c @@ -0,0 +1,57 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "ctx.h" +#include "hooks.h" + +#include <linux/fs.h> +#include <linux/sched.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/security.h> +#include <linux/rcupdate.h> +#include <linux/lsm_hooks.h> + +struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = { + .lbs_task = sizeof(struct ipe_context __rcu *), +}; + +static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { + LSM_HOOK_INIT(task_alloc, ipe_task_alloc), + LSM_HOOK_INIT(task_free, ipe_task_free), +}; + +/** + * ipe_init: Entry point of IPE. + * + * This is called at LSM init, which happens occurs early during kernel + * start up. During this phase, IPE loads the properties compiled into + * the kernel, and register's IPE's hooks. The boot policy is loaded + * later, during securityfs init, at which point IPE will start + * enforcing its policy. + * + * Return: + * 0 - OK + * -ENOMEM - Context creation failed. + */ +static int __init ipe_init(void) +{ + int rc = 0; + + rc = ipe_init_ctx(); + if (rc) + return rc; + + security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), "ipe"); + + return rc; +} + +DEFINE_LSM(ipe) = { + .name = "ipe", + .init = ipe_init, + .blobs = &ipe_blobs, +}; diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h new file mode 100644 index 000000000000..09c492b8fd03 --- /dev/null +++ b/security/ipe/ipe.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef IPE_H +#define IPE_H + +#define pr_fmt(fmt) "IPE " fmt "\n" + +#include "ctx.h" + +#include <linux/types.h> +#include <linux/sched.h> +#include <linux/lsm_hooks.h> + +extern struct lsm_blob_sizes ipe_blobs; + +#endif /* IPE_H */ -- 2.33.0