[PATCH 10/24] hibernate: Disable when the kernel is locked down

[PATCH 10/24] hibernate: Disable when the kernel is locked down

[David Howells]

From: Josh Boyer <jwboyer@fedoraproject.org>

There is currently no way to verify the resume image when returning
from hibernate.  This might compromise the signed modules trust model,
so until we can work with signed hibernate images we disable it when the
kernel is locked down.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-pm@vger.kernel.org
---

 kernel/power/hibernate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index a8b978c35a6a..50cca5dcb62f 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -70,7 +70,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
 
 bool hibernation_available(void)
 {
-	return (nohibernate == 0);
+	return nohibernate == 0 && !kernel_is_locked_down();
 }
 
 /**

[PATCH 11/24] uswsusp: Disable when the kernel is locked down

[David Howells]

From: Matthew Garrett <mjg59@srcf.ucam.org>

uswsusp allows a user process to dump and then restore kernel state, which
makes it possible to modify the running kernel.  Disable this if the kernel
is locked down.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-pm@vger.kernel.org
---

 kernel/power/user.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7ff672..e4b926d329b7 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 	if (!hibernation_available())
 		return -EPERM;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	lock_system_sleep();
 
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Rafael J. Wysocki]

On Wed, Apr 5, 2017 at 10:16 PM, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> From: Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
>
> uswsusp allows a user process to dump and then restore kernel state, which
> makes it possible to modify the running kernel.  Disable this if the kernel
> is locked down.
>
> Signed-off-by: Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
> Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> cc: linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

You probably want to disable hibernation altogether in this case.

Thanks,
Rafael

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Oliver Neukum]

Am Donnerstag, den 06.04.2017, 01:38 +0200 schrieb Rafael J. Wysocki:
> On Wed, Apr 5, 2017 at 10:16 PM, David Howells <dhowells@redhat.com> wrote:
> > 
> > From: Matthew Garrett <mjg59@srcf.ucam.org>
> > 
> > uswsusp allows a user process to dump and then restore kernel state, which
> > makes it possible to modify the running kernel.  Disable this if the kernel
> > is locked down.
> > 
> > Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > cc: linux-pm@vger.kernel.org
> 
> You probably want to disable hibernation altogether in this case.

Your swap partition may be located on an NVDIMM or be encrypted.
Isn't this a bit overly drastic?

	Regards
		Oliver

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[David Howells]

Rafael J. Wysocki <rafael@kernel.org> wrote:

> You probably want to disable hibernation altogether in this case.

See patch 10.  Does that mean patch 11 is superfluous?

David

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[David Howells]

Oliver Neukum <oneukum@suse.com> wrote:

> Your swap partition may be located on an NVDIMM or be encrypted.

An NVDIMM should be considered the same as any other persistent storage.

It may be encrypted, but where's the key stored, how easy is it to retrieve
and does the swapout code know this?

> Isn't this a bit overly drastic?

Perhaps, but if it's on disk and it's not encrypted, then maybe not.

David

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Rafael J. Wysocki]

On Thu, Apr 6, 2017 at 8:55 AM, David Howells <dhowells@redhat.com> wrote:
> Rafael J. Wysocki <rafael@kernel.org> wrote:
>
>> You probably want to disable hibernation altogether in this case.
>
> See patch 10.  Does that mean patch 11 is superfluous?

Yes, it does.

You can't open /dev/snapshot if hibernation_available() returns false.

Thanks,
Rafael

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Rafael J. Wysocki]

On Thu, Apr 6, 2017 at 10:41 AM, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> wrote:
>
>> Your swap partition may be located on an NVDIMM or be encrypted.
>
> An NVDIMM should be considered the same as any other persistent storage.
>
> It may be encrypted, but where's the key stored, how easy is it to retrieve
> and does the swapout code know this?
>
>> Isn't this a bit overly drastic?
>
> Perhaps, but if it's on disk and it's not encrypted, then maybe not.

Right.

Swap encryption is not mandatory and I'm not sure how the hibernate
code can verify whether or not it is in use.

Thanks,
Rafael

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Rafael J. Wysocki]

On Thu, Apr 6, 2017 at 10:09 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Thu, Apr 6, 2017 at 10:41 AM, David Howells <dhowells@redhat.com> wrote:
>> Oliver Neukum <oneukum@suse.com> wrote:
>>
>>> Your swap partition may be located on an NVDIMM or be encrypted.
>>
>> An NVDIMM should be considered the same as any other persistent storage.
>>
>> It may be encrypted, but where's the key stored, how easy is it to retrieve
>> and does the swapout code know this?
>>
>>> Isn't this a bit overly drastic?
>>
>> Perhaps, but if it's on disk and it's not encrypted, then maybe not.
>
> Right.
>
> Swap encryption is not mandatory and I'm not sure how the hibernate
> code can verify whether or not it is in use.

BTW, SUSE has patches adding secure boot support to the hibernate code
and Jiri promised me to post them last year even. :-)

Thanks,
Rafael

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[Jiri Kosina]

On Thu, 6 Apr 2017, Rafael J. Wysocki wrote:

> >>> Your swap partition may be located on an NVDIMM or be encrypted.
> >>
> >> An NVDIMM should be considered the same as any other persistent storage.
> >>
> >> It may be encrypted, but where's the key stored, how easy is it to retrieve
> >> and does the swapout code know this?
> >>
> >>> Isn't this a bit overly drastic?
> >>
> >> Perhaps, but if it's on disk and it's not encrypted, then maybe not.
> >
> > Right.
> >
> > Swap encryption is not mandatory and I'm not sure how the hibernate
> > code can verify whether or not it is in use.
> 
> BTW, SUSE has patches adding secure boot support to the hibernate code
> and Jiri promised me to post them last year even. :-)

Oh, thanks for a friendly ping :) Adding Joey Lee to CC.

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[poma]

On 06.04.2017 22:25, Jiri Kosina wrote:
> On Thu, 6 Apr 2017, Rafael J. Wysocki wrote:
> 
>>>>> Your swap partition may be located on an NVDIMM or be encrypted.
>>>>
>>>> An NVDIMM should be considered the same as any other persistent storage.
>>>>
>>>> It may be encrypted, but where's the key stored, how easy is it to retrieve
>>>> and does the swapout code know this?
>>>>
>>>>> Isn't this a bit overly drastic?
>>>>
>>>> Perhaps, but if it's on disk and it's not encrypted, then maybe not.
>>>
>>> Right.
>>>
>>> Swap encryption is not mandatory and I'm not sure how the hibernate
>>> code can verify whether or not it is in use.
>>
>> BTW, SUSE has patches adding secure boot support to the hibernate code
>> and Jiri promised me to post them last year even. :-)
> 
> Oh, thanks for a friendly ping :) Adding Joey Lee to CC.
> 

Rafael J., are you talking about HIBERNATE_VERIFICATION ?

Ref.
https://github.com/joeyli/linux-s4sign/commits/s4sign-hmac-v2-v4.2-rc8
https://lkml.org/lkml/2015/8/11/47
https://bugzilla.redhat.com/show_bug.cgi?id=1330335

Re: [PATCH 11/24] uswsusp: Disable when the kernel is locked down

[joeyli]

On Sat, Apr 08, 2017 at 05:28:15AM +0200, poma wrote:
> On 06.04.2017 22:25, Jiri Kosina wrote:
> > On Thu, 6 Apr 2017, Rafael J. Wysocki wrote:
> > 
> >>>>> Your swap partition may be located on an NVDIMM or be encrypted.
> >>>>
> >>>> An NVDIMM should be considered the same as any other persistent storage.
> >>>>
> >>>> It may be encrypted, but where's the key stored, how easy is it to retrieve
> >>>> and does the swapout code know this?
> >>>>
> >>>>> Isn't this a bit overly drastic?
> >>>>
> >>>> Perhaps, but if it's on disk and it's not encrypted, then maybe not.
> >>>
> >>> Right.
> >>>
> >>> Swap encryption is not mandatory and I'm not sure how the hibernate
> >>> code can verify whether or not it is in use.
> >>
> >> BTW, SUSE has patches adding secure boot support to the hibernate code
> >> and Jiri promised me to post them last year even. :-)
> > 
> > Oh, thanks for a friendly ping :) Adding Joey Lee to CC.
> > 
> 
> Rafael J., are you talking about HIBERNATE_VERIFICATION ?
> 
> Ref.
> https://github.com/joeyli/linux-s4sign/commits/s4sign-hmac-v2-v4.2-rc8
> https://lkml.org/lkml/2015/8/11/47
> https://bugzilla.redhat.com/show_bug.cgi?id=1330335
>

I am working on switch to HMAC-SHA512. 

On the other hand, some mechanisms keep signing/encryption key in memory.
e.g. dm-crypt or hibernation verification. Kees Cook suggested that we
should add kernel memory reads as a thread model of securelevel to
prevent leaking those keys by /dev/kmem, bpf, kdump or hibernation...
We still need time to implement it.

Thanks a lot!
Joey Lee