linux-kernel - Re: [PATCH 15/18] Hibernate: adapt to UEFI secure boot with signature check

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Date:	Sun, 25 Aug 2013 18:42:19 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-crypto@...r.kernel.org,
	opensuse-kernel@...nsuse.org, David Howells <dhowells@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Len Brown <len.brown@...el.com>,
	Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	James Bottomley <james.bottomley@...senpartnership.com>,
	Greg KH <gregkh@...uxfoundation.org>, JKosina@...e.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Gary Lin <GLin@...e.com>, Vivek Goyal <vgoyal@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [PATCH 15/18] Hibernate: adapt to UEFI secure boot with
 signature check

On Thu 2013-08-22 19:01:54, Lee, Chun-Yi wrote:
> In current solution, the snapshot signature check used the RSA key-pair
> that are generated by bootloader(e.g. shim) and pass the key-pair to
> kernel through EFI variables. I choice to binding the snapshot
> signature check mechanism with UEFI secure boot for provide stronger
> protection of hibernate. Current behavior is following:
> 
>  + UEFI Secure Boot ON, Kernel found key-pair from shim:
>    Will do the S4 signature check.
> 
>  + UEFI Secure Boot ON, Kernel didn't find key-pair from shim:
>    Will lock down S4 function.
> 
>  + UEFI Secure Boot OFF
>    Will NOT do the S4 signature check.
>    Ignore any keys from bootloader.
> 
> v2:
> Replace sign_key_data_loaded() by skey_data_available() to check sign key data
> is available for hibernate.
> 
> Reviewed-by: Jiri Kosina <jkosina@...e.cz>
> Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
> ---
>  kernel/power/hibernate.c |   36 +++++++++++++++++-
>  kernel/power/main.c      |   11 +++++-
>  kernel/power/snapshot.c  |   95 ++++++++++++++++++++++++++--------------------
>  kernel/power/swap.c      |    4 +-
>  kernel/power/user.c      |   11 +++++
>  5 files changed, 112 insertions(+), 45 deletions(-)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index c545b15..0f19f3d 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -29,6 +29,7 @@
>  #include <linux/ctype.h>
>  #include <linux/genhd.h>
>  #include <linux/key.h>
> +#include <linux/efi.h>
>  
>  #include "power.h"
>  
> @@ -632,7 +633,14 @@ static void power_down(void)
>  int hibernate(void)
>  {
>  	int error;
> -	int skey_error;
> +
> +#ifdef CONFIG_SNAPSHOT_VERIFICATION
> +	if (!capable(CAP_COMPROMISE_KERNEL) && !skey_data_available()) {
> +#else
> +	if (!capable(CAP_COMPROMISE_KERNEL)) {
> +#endif
> +		return -EPERM;
> +	}
>  
>  	lock_system_sleep();
>  	/* The snapshot device should not be opened while we're running */
> @@ -799,6 +807,15 @@ static int software_resume(void)
>  	if (error)
>  		goto Unlock;
>  
> +#ifdef CONFIG_SNAPSHOT_VERIFICATION
> +	if (!capable(CAP_COMPROMISE_KERNEL) && !wkey_data_available()) {
> +#else
> +	if (!capable(CAP_COMPROMISE_KERNEL)) {
> +#endif
> +		mutex_unlock(&pm_mutex);
> +		return -EPERM;
> +	}
> +
>  	/* The snapshot device should not be opened while we're running */
>  	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
>  		error = -EBUSY;
> @@ -892,6 +909,15 @@ static ssize_t disk_show(struct kobject *kobj, struct kobj_attribute *attr,
>  	int i;
>  	char *start = buf;
>  
> +#ifdef CONFIG_SNAPSHOT_VERIFICATION
> +	if (efi_enabled(EFI_SECURE_BOOT) && !skey_data_available()) {
> +#else
> +	if (efi_enabled(EFI_SECURE_BOOT)) {
> +#endif
> +		buf += sprintf(buf, "[%s]\n", "disabled");
> +		return buf-start;
> +	}
> +
>  	for (i = HIBERNATION_FIRST; i <= HIBERNATION_MAX; i++) {
>  		if (!hibernation_modes[i])
>  			continue;
> @@ -926,6 +952,14 @@ static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	char *p;
>  	int mode = HIBERNATION_INVALID;
>  
> +#ifdef CONFIG_SNAPSHOT_VERIFICATION
> +	if (!capable(CAP_COMPROMISE_KERNEL) && !skey_data_available()) {
> +#else
> +	if (!capable(CAP_COMPROMISE_KERNEL)) {
> +#endif
> +		return -EPERM;
> +	}
> +
>  	p = memchr(buf, '\n', n);
>  	len = p ? p - buf : n;
>  

You clearly need some helper function.
									Pavel

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