[PATCH] selinux: add selinux_is_enforced() function

[PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

Add selinux_is_enforced() function to give access to SELinux
enforcement to the rest of the kernel.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
---
 include/linux/selinux.h             | 5 +++++
 security/selinux/exports.c          | 6 ++++++
 security/selinux/hooks.c            | 2 ++
 security/selinux/include/avc.h      | 6 ------
 security/selinux/include/security.h | 1 +
 5 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/selinux.h b/include/linux/selinux.h
index 44f4596..1007321 100644
--- a/include/linux/selinux.h
+++ b/include/linux/selinux.h
@@ -24,12 +24,17 @@
  * selinux_is_enabled - is SELinux enabled?
  */
 bool selinux_is_enabled(void);
+bool selinux_is_enforced(void);
 #else
 
 static inline bool selinux_is_enabled(void)
 {
 	return false;
 }
+static inline bool selinux_is_enforced(void)
+{
+	return false;
+}
 #endif	/* CONFIG_SECURITY_SELINUX */
 
 #endif /* _LINUX_SELINUX_H */
diff --git a/security/selinux/exports.c b/security/selinux/exports.c
index e75dd94..016f1e2 100644
--- a/security/selinux/exports.c
+++ b/security/selinux/exports.c
@@ -21,3 +21,9 @@ bool selinux_is_enabled(void)
 	return selinux_enabled;
 }
 EXPORT_SYMBOL_GPL(selinux_is_enabled);
+
+bool selinux_is_enforced(void)
+{
+	return selinux_enforcing;
+}
+EXPORT_SYMBOL_GPL(selinux_is_enforced);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e67a526..da2baeb 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -109,6 +109,8 @@ static int __init enforcing_setup(char *str)
 	return 1;
 }
 __setup("enforcing=", enforcing_setup);
+#else
+int selinux_enforcing;
 #endif
 
 #ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM
diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h
index 0999df0..ff98351 100644
--- a/security/selinux/include/avc.h
+++ b/security/selinux/include/avc.h
@@ -19,12 +19,6 @@
 #include "av_permissions.h"
 #include "security.h"
 
-#ifdef CONFIG_SECURITY_SELINUX_DEVELOP
-extern int selinux_enforcing;
-#else
-#define selinux_enforcing 1
-#endif
-
 /*
  * An entry in the AVC.
  */
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index f979c35..1e67e268 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -64,6 +64,7 @@
 struct netlbl_lsm_secattr;
 
 extern int selinux_enabled;
+extern int selinux_enforcing;
 
 /* Policy capabilities */
 enum {
-- 
1.8.3.1

Re: [PATCH] selinux: add selinux_is_enforced() function

[Paul Moore]

On Wed, Apr 12, 2017 at 5:06 AM, Sebastien Buisson
<sbuisson.ddn@gmail.com> wrote:
> Add selinux_is_enforced() function to give access to SELinux
> enforcement to the rest of the kernel.
>
> Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
> ---
>  include/linux/selinux.h             | 5 +++++
>  security/selinux/exports.c          | 6 ++++++
>  security/selinux/hooks.c            | 2 ++
>  security/selinux/include/avc.h      | 6 ------
>  security/selinux/include/security.h | 1 +
>  5 files changed, 14 insertions(+), 6 deletions(-)

As currently written this code isn't something we would want to merge
upstream for two important reasons:

* No clear user of this functionality.  There needs to be a well
defined user of this functionality in the kernel.

* No abstraction layer at the LSM interface.  The core kernel code
should not call directly into any specific LSM, all interaction should
go through the LSM hooks.

> diff --git a/include/linux/selinux.h b/include/linux/selinux.h
> index 44f4596..1007321 100644
> --- a/include/linux/selinux.h
> +++ b/include/linux/selinux.h
> @@ -24,12 +24,17 @@
>   * selinux_is_enabled - is SELinux enabled?
>   */
>  bool selinux_is_enabled(void);
> +bool selinux_is_enforced(void);
>  #else
>
>  static inline bool selinux_is_enabled(void)
>  {
>         return false;
>  }
> +static inline bool selinux_is_enforced(void)
> +{
> +       return false;
> +}
>  #endif /* CONFIG_SECURITY_SELINUX */
>
>  #endif /* _LINUX_SELINUX_H */
> diff --git a/security/selinux/exports.c b/security/selinux/exports.c
> index e75dd94..016f1e2 100644
> --- a/security/selinux/exports.c
> +++ b/security/selinux/exports.c
> @@ -21,3 +21,9 @@ bool selinux_is_enabled(void)
>         return selinux_enabled;
>  }
>  EXPORT_SYMBOL_GPL(selinux_is_enabled);
> +
> +bool selinux_is_enforced(void)
> +{
> +       return selinux_enforcing;
> +}
> +EXPORT_SYMBOL_GPL(selinux_is_enforced);
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index e67a526..da2baeb 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -109,6 +109,8 @@ static int __init enforcing_setup(char *str)
>         return 1;
>  }
>  __setup("enforcing=", enforcing_setup);
> +#else
> +int selinux_enforcing;
>  #endif
>
>  #ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM
> diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h
> index 0999df0..ff98351 100644
> --- a/security/selinux/include/avc.h
> +++ b/security/selinux/include/avc.h
> @@ -19,12 +19,6 @@
>  #include "av_permissions.h"
>  #include "security.h"
>
> -#ifdef CONFIG_SECURITY_SELINUX_DEVELOP
> -extern int selinux_enforcing;
> -#else
> -#define selinux_enforcing 1
> -#endif
> -
>  /*
>   * An entry in the AVC.
>   */
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index f979c35..1e67e268 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -64,6 +64,7 @@
>  struct netlbl_lsm_secattr;
>
>  extern int selinux_enabled;
> +extern int selinux_enforcing;
>
>  /* Policy capabilities */
>  enum {
> --
> 1.8.3.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
paul moore
security @ redhat

Re: [PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

2017-04-12 13:55 GMT+02:00 Paul Moore <pmoore@redhat.com>:
> As currently written this code isn't something we would want to merge
> upstream for two important reasons:
>
> * No abstraction layer at the LSM interface.  The core kernel code
> should not call directly into any specific LSM, all interaction should
> go through the LSM hooks.

The idea behind this patch and the other one was to replicate what is
done with selinux_is_enabled(). As I understand it now,
selinux_is_enabled() should remain the only exception to the LSM
hooks.
So do you agree if I propose a new security_is_enforced() function at
the LSM abstraction layer, which will be hooked to a
selinux_is_enforced() function defined inside the SELinux LSM?

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 15:30 +0200, Sebastien Buisson wrote:
> 2017-04-12 13:55 GMT+02:00 Paul Moore <pmoore@redhat.com>:
> > As currently written this code isn't something we would want to
> > merge
> > upstream for two important reasons:
> > 
> > * No abstraction layer at the LSM interface.  The core kernel code
> > should not call directly into any specific LSM, all interaction
> > should
> > go through the LSM hooks.
> 
> The idea behind this patch and the other one was to replicate what is
> done with selinux_is_enabled(). As I understand it now,
> selinux_is_enabled() should remain the only exception to the LSM
> hooks.
> So do you agree if I propose a new security_is_enforced() function at
> the LSM abstraction layer, which will be hooked to a
> selinux_is_enforced() function defined inside the SELinux LSM?

Even your usage of selinux_is_enabled() looks suspect; that should
probably go away.  Only other user of it seems to be some cred validity
checking that could be dropped as well.  The include/linux/selinux.h
interfaces were originally for use by audit and secmark when there were
no other LSMs and have gradually been removed.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

2017-04-12 15:58 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> Even your usage of selinux_is_enabled() looks suspect; that should
> probably go away.  Only other user of it seems to be some cred validity
> checking that could be dropped as well.

Well the main reason for calling selinux_is_enabled() is performance
optimization.
Should I propose a patch to add a new security_is_enabled() function
at the LSM abstraction layer? Or do you consider we should not test
security enabled at all?

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 17:19 +0200, Sebastien Buisson wrote:
> 2017-04-12 15:58 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> > Even your usage of selinux_is_enabled() looks suspect; that should
> > probably go away.  Only other user of it seems to be some cred
> > validity
> > checking that could be dropped as well.
> 
> Well the main reason for calling selinux_is_enabled() is performance
> optimization.
> Should I propose a patch to add a new security_is_enabled() function
> at the LSM abstraction layer? Or do you consider we should not test
> security enabled at all?

It isn't clear what "is enabled" means in general, particularly with
stacking. I would either drop it or replace it with a LSM hook that is
more precise.  For example, NFSv4 introduced a security_ismaclabel()
hook so that it could test whether a given security.* xattr is a MAC
label.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Casey Schaufler]

On 4/12/2017 9:33 AM, Stephen Smalley wrote:
> On Wed, 2017-04-12 at 17:19 +0200, Sebastien Buisson wrote:
>> 2017-04-12 15:58 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
>>> Even your usage of selinux_is_enabled() looks suspect; that should
>>> probably go away.  Only other user of it seems to be some cred
>>> validity
>>> checking that could be dropped as well.
>> Well the main reason for calling selinux_is_enabled() is performance
>> optimization.
>> Should I propose a patch to add a new security_is_enabled() function
>> at the LSM abstraction layer? Or do you consider we should not test
>> security enabled at all?
> It isn't clear what "is enabled" means in general, particularly with
> stacking. I would either drop it or replace it with a LSM hook that is
> more precise.  For example, NFSv4 introduced a security_ismaclabel()
> hook so that it could test whether a given security.* xattr is a MAC
> label.

You can determine what security modules are enabled
by reading /sys/kernel/security/lsm in userspace (4.11 feature).

Your kernel code *really* shouldn't care what security
modules are enabled. If you do care, you've designed poorly.
If you're trying to ensure consistent policy between members
of your cluster you're better off doing that in user space
than in the kernel.

>
> _______________________________________________
> Selinux mailing list
> Selinux@tycho.nsa.gov
> To unsubscribe, send email to Selinux-leave@tycho.nsa.gov.
> To get help, send an email containing "help" to Selinux-request@tycho.nsa.gov.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

2017-04-12 13:55 GMT+02:00 Paul Moore <pmoore@redhat.com>:
> As currently written this code isn't something we would want to merge
> upstream for two important reasons:
>
> * No clear user of this functionality.  There needs to be a well
> defined user of this functionality in the kernel.

The use case for this new functionality (and the other one) is getting
SELinux information from the Lustre client code in kernel space.
Latest patch can be accessed at:
https://review.whamcloud.com/24421
Actual user is sptlrpc_get_sepol() function in lustre/lustre/ptlrpc/sec.c file.
This code will be pushed to the upstream kernel as soon as it is
landed into Lustre master branch.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 15:30 +0200, Sebastien Buisson wrote:
> 2017-04-12 13:55 GMT+02:00 Paul Moore <pmoore@redhat.com>:
> > As currently written this code isn't something we would want to
> > merge
> > upstream for two important reasons:
> > 
> > * No clear user of this functionality.  There needs to be a well
> > defined user of this functionality in the kernel.
> 
> The use case for this new functionality (and the other one) is
> getting
> SELinux information from the Lustre client code in kernel space.
> Latest patch can be accessed at:
> https://review.whamcloud.com/24421
> Actual user is sptlrpc_get_sepol() function in
> lustre/lustre/ptlrpc/sec.c file.
> This code will be pushed to the upstream kernel as soon as it is
> landed into Lustre master branch.

How are you using this SELinux information in the kernel and/or in
userspace?  What's the purpose of it?  What are you comparing it
against?  Why do you care if it changes?

Note btw that the notion of a policy name/type and the policy file path
is purely a userspace construct and shouldn't be embedded in your
kernel code.  Android for example doesn't follow that convention at
all; their SELinux policy file is simply /sepolicy.  On modern kernels,
you can always read the currently loaded policy from the kernel itself
via /sys/fs/selinux/policy (formerly just /selinux/policy).

Re: [PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

2017-04-12 16:35 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> How are you using this SELinux information in the kernel and/or in
> userspace?  What's the purpose of it?  What are you comparing it
> against?  Why do you care if it changes?

Enforcement status and policy version are compared to their previously
stored value. If they differ, then it means we need to call a userland
helper from Lustre client kernelspace to read the currently loaded
policy (reading it will let us know if the Lustre client node is
conforming to the Lustre-wide security policy).
As calling the userland helper is costly, we do it only when it is
necessary by retrieving some SELinux key information directly from
kernelspace.

> Note btw that the notion of a policy name/type and the policy file path
> is purely a userspace construct and shouldn't be embedded in your
> kernel code.  Android for example doesn't follow that convention at
> all; their SELinux policy file is simply /sepolicy.  On modern kernels,
> you can always read the currently loaded policy from the kernel itself
> via /sys/fs/selinux/policy (formerly just /selinux/policy).

As I understand it, a userspace program can directly read the policy
info exposed by the kernel by reading this file. But how about reading
it from kernelspace?

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 17:11 +0200, Sebastien Buisson wrote:
> 2017-04-12 16:35 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> > How are you using this SELinux information in the kernel and/or in
> > userspace?  What's the purpose of it?  What are you comparing it
> > against?  Why do you care if it changes?
> 
> Enforcement status and policy version are compared to their
> previously
> stored value. If they differ, then it means we need to call a
> userland
> helper from Lustre client kernelspace to read the currently loaded
> policy (reading it will let us know if the Lustre client node is
> conforming to the Lustre-wide security policy).
> As calling the userland helper is costly, we do it only when it is
> necessary by retrieving some SELinux key information directly from
> kernelspace.

Maybe you want to register a notifier callback on policy reload? See
the archives for the SELinux support for Infiniband RDMA patches (which
seem to have stalled), which included LSM hooks and SELinux
implementation to support notifications on policy reloads.

> 
> > Note btw that the notion of a policy name/type and the policy file
> > path
> > is purely a userspace construct and shouldn't be embedded in your
> > kernel code.  Android for example doesn't follow that convention at
> > all; their SELinux policy file is simply /sepolicy.  On modern
> > kernels,
> > you can always read the currently loaded policy from the kernel
> > itself
> > via /sys/fs/selinux/policy (formerly just /selinux/policy).
> 
> As I understand it, a userspace program can directly read the policy
> info exposed by the kernel by reading this file. But how about
> reading
> it from kernelspace?

In SELinux, the underlying kernel function is security_read_policy();
you'd have to wrap it with a LSM hook interface, and generalize it a
bit wrt whether to use vmalloc_user() or not.

This seems very inefficient though for your purposes.  Wouldn't it be
better to just extend SELinux to compute the checksum from the original
image when the policy is loaded, save that checksum in the policydb,
and provide you with a way to fetch the already computed checksum?  The
computation would be done in security_load_policy() and saved in the
policydb.  Then you could introduce a function and a LSM hook to export
it to your code. We would probably want to also expose it via a
selinuxfs node to userspace.

This however only works for checking that you have a completely
identical policy built in exactly the same way.  You could have
semantically identical policies that still differ in the binary policy
file, or policies with minor local customizations that aren't
significant.  But perhaps that isn't an issue for Lustre environments.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Sebastien Buisson]

2017-04-12 18:24 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> Maybe you want to register a notifier callback on policy reload? See
> the archives for the SELinux support for Infiniband RDMA patches (which
> seem to have stalled), which included LSM hooks and SELinux
> implementation to support notifications on policy reloads.

I need to have a look indeed. So it is a callback in kernelspace?

>> As I understand it, a userspace program can directly read the policy
>> info exposed by the kernel by reading this file. But how about
>> reading it from kernelspace?
>
> This seems very inefficient though for your purposes.  Wouldn't it be
> better to just extend SELinux to compute the checksum from the original
> image when the policy is loaded, save that checksum in the policydb,
> and provide you with a way to fetch the already computed checksum?  The
> computation would be done in security_load_policy() and saved in the
> policydb.  Then you could introduce a function and a LSM hook to export
> it to your code. We would probably want to also expose it via a
> selinuxfs node to userspace.

This is an excellent suggestion. It makes much more sense to have the
checksum computed on SELinux side when a policy is loaded. And then
just read this checksum when needed, both from kernel and userspace.

> This however only works for checking that you have a completely
> identical policy built in exactly the same way.  You could have
> semantically identical policies that still differ in the binary policy
> file, or policies with minor local customizations that aren't
> significant.  But perhaps that isn't an issue for Lustre environments.

If we can protect against local customizations this is great. What
could be the other scenario leading to different binary policies while
being semantically identical?

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 19:07 +0200, Sebastien Buisson wrote:
> 2017-04-12 18:24 GMT+02:00 Stephen Smalley <sds@tycho.nsa.gov>:
> > Maybe you want to register a notifier callback on policy reload?
> > See
> > the archives for the SELinux support for Infiniband RDMA patches
> > (which
> > seem to have stalled), which included LSM hooks and SELinux
> > implementation to support notifications on policy reloads.
> 
> I need to have a look indeed. So it is a callback in kernelspace?

Yes, see:
https://patchwork.kernel.org/patch/9443417/

> 
> > > As I understand it, a userspace program can directly read the
> > > policy
> > > info exposed by the kernel by reading this file. But how about
> > > reading it from kernelspace?
> > 
> > This seems very inefficient though for your purposes.  Wouldn't it
> > be
> > better to just extend SELinux to compute the checksum from the
> > original
> > image when the policy is loaded, save that checksum in the
> > policydb,
> > and provide you with a way to fetch the already computed
> > checksum?  The
> > computation would be done in security_load_policy() and saved in
> > the
> > policydb.  Then you could introduce a function and a LSM hook to
> > export
> > it to your code. We would probably want to also expose it via a
> > selinuxfs node to userspace.
> 
> This is an excellent suggestion. It makes much more sense to have the
> checksum computed on SELinux side when a policy is loaded. And then
> just read this checksum when needed, both from kernel and userspace.
>
> > This however only works for checking that you have a completely
> > identical policy built in exactly the same way.  You could have
> > semantically identical policies that still differ in the binary
> > policy
> > file, or policies with minor local customizations that aren't
> > significant.  But perhaps that isn't an issue for Lustre
> > environments.
> 
> If we can protect against local customizations this is great. What
> could be the other scenario leading to different binary policies
> while
> being semantically identical?

There can be ordering or optimization differences, depending on the
policy compiler toolchain and build process. Probably not a concern if
they are all running the same distro with the same policy package,
built in the same build environment.

Re: [PATCH] selinux: add selinux_is_enforced() function

[Stephen Smalley]

On Wed, 2017-04-12 at 18:06 +0900, Sebastien Buisson wrote:
> Add selinux_is_enforced() function to give access to SELinux
> enforcement to the rest of the kernel.
> 
> Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
> ---
>  include/linux/selinux.h             | 5 +++++
>  security/selinux/exports.c          | 6 ++++++
>  security/selinux/hooks.c            | 2 ++
>  security/selinux/include/avc.h      | 6 ------
>  security/selinux/include/security.h | 1 +
>  5 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/selinux.h b/include/linux/selinux.h
> index 44f4596..1007321 100644
> --- a/include/linux/selinux.h
> +++ b/include/linux/selinux.h
> @@ -24,12 +24,17 @@
>   * selinux_is_enabled - is SELinux enabled?
>   */
>  bool selinux_is_enabled(void);
> +bool selinux_is_enforced(void);
>  #else
>  
>  static inline bool selinux_is_enabled(void)
>  {
>  	return false;
>  }
> +static inline bool selinux_is_enforced(void)
> +{
> +	return false;
> +}
>  #endif	/* CONFIG_SECURITY_SELINUX */
>  
>  #endif /* _LINUX_SELINUX_H */
> diff --git a/security/selinux/exports.c b/security/selinux/exports.c
> index e75dd94..016f1e2 100644
> --- a/security/selinux/exports.c
> +++ b/security/selinux/exports.c
> @@ -21,3 +21,9 @@ bool selinux_is_enabled(void)
>  	return selinux_enabled;
>  }
>  EXPORT_SYMBOL_GPL(selinux_is_enabled);
> +
> +bool selinux_is_enforced(void)
> +{
> +	return selinux_enforcing;
> +}
> +EXPORT_SYMBOL_GPL(selinux_is_enforced);
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index e67a526..da2baeb 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -109,6 +109,8 @@ static int __init enforcing_setup(char *str)
>  	return 1;
>  }
>  __setup("enforcing=", enforcing_setup);
> +#else
> +int selinux_enforcing;
>  #endif
>  
>  #ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM
> diff --git a/security/selinux/include/avc.h
> b/security/selinux/include/avc.h
> index 0999df0..ff98351 100644
> --- a/security/selinux/include/avc.h
> +++ b/security/selinux/include/avc.h
> @@ -19,12 +19,6 @@
>  #include "av_permissions.h"
>  #include "security.h"
>  
> -#ifdef CONFIG_SECURITY_SELINUX_DEVELOP
> -extern int selinux_enforcing;
> -#else
> -#define selinux_enforcing 1
> -#endif

If CONFIG_SECURITY_SELINUX_DEVELOP=n, then selinux_enforcing is
supposed to always be 1, i.e. global permissive mode is not supported. 
Your patch breaks that.  That's in addition to the points raised by
others about needing an in-tree user and use of a LSM hook interface
instead.

> -
>  /*
>   * An entry in the AVC.
>   */
> diff --git a/security/selinux/include/security.h
> b/security/selinux/include/security.h
> index f979c35..1e67e268 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -64,6 +64,7 @@
>  struct netlbl_lsm_secattr;
>  
>  extern int selinux_enabled;
> +extern int selinux_enforcing;
>  
>  /* Policy capabilities */
>  enum {