linux-kernel - encrypted hibernation (was Re: Hibernation considerations)

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Message-ID: <20070805195628.GA1947@elf.ucw.cz>
Date:	Sun, 5 Aug 2007 21:56:29 +0200
From:	Pavel Machek <pavel@....cz>
To:	Vojtech Pavlik <vojtech@...e.cz>, seife@...e.de
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	pm list <linux-pm@...ts.linux-foundation.org>, david@...g.hm,
	Al Boldi <a1426z@...ab.com>
Subject: encrypted hibernation (was Re: Hibernation considerations)

Hi!

> > > Two things which I think would be nice to consider are:
> > >    1) Encryption - I'd actually prefer if my luks device did not
> > >        remember the key accross a hibernation; I want to be forced to
> > >        reenter the phrase.  However I don't know what the best thing
> > >        to do to partitions/applications using the luks device is.
> > 
> > Encryption is possible with both the userland hibernation (aka uswsusp) and
> > TuxOnIce (formerly known as suspend2).  Still, I don't consider it as a "must
> > have" feature for a framework to be generally useful (many users don't use it
> > anyway).
> 
> If a user uses an encrypted filesystem, then he also needs an encrypted
> swap and encrypted hibernation image: Otherwise the fileystem encryption
> is not very useful.

Actually, we can do most of that stuff already. 

We can encrypt filesystems, encrypt swaps (LVM), and encrypt hibernation.

What we _can't_ do is to hibernate on LVM encrypted partition, and we
could only suspend to swap partition. Bad combination, but here's way
out: just use separate (raw) partition for hibernation.

Ok, that needs re-partitioning; if that's bad, just swapoff before
hibernation and mkswap/swapon after its done.

Index: suspend.c
===================================================================
RCS file: /cvsroot/suspend/suspend/suspend.c,v
retrieving revision 1.82
diff -u -u -r1.82 suspend.c
--- suspend.c	29 Jul 2007 12:48:10 -0000	1.82
+++ suspend.c	5 Aug 2007 19:49:05 -0000
@@ -59,6 +59,7 @@
 static unsigned long pref_image_size = IMAGE_SIZE;
 static int suspend_loglevel = SUSPEND_LOGLEVEL;
 static char compute_checksum;
+static int raw_partition = 1;
 #ifdef CONFIG_COMPRESS
 static char compress;
 #else
@@ -184,6 +185,9 @@
 	int error;
 	loff_t free_swap;
 
+	if (raw_partition)
+		return 1*1024*1024*1024;
+
 	error = ioctl(dev, SNAPSHOT_AVAIL_SWAP, &free_swap);
 	if (!error)
 		return free_swap;
@@ -197,6 +201,12 @@
 	int error;
 	loff_t offset;
 
+	if (raw_partition) {
+		static int cur_offset = 0;
+		cur_offset += page_size;
+		return cur_offset;
+	}
+
 	error = ioctl(dev, SNAPSHOT_GET_SWAP_PAGE, &offset);
 	if (!error)
 		return offset;
@@ -205,6 +215,8 @@
 
 static inline int free_swap_pages(int dev)
 {
+	if (raw_partition)
+		return 0;
 	return ioctl(dev, SNAPSHOT_FREE_SWAP_PAGES, 0);
 }
 
@@ -213,6 +225,8 @@
 	struct resume_swap_area swap;
 	int error;
 
+	if (raw_partition)
+		return 0;
 	swap.dev = blkdev;
 	swap.offset = offset;
 	error = ioctl(dev, SNAPSHOT_SET_SWAP_AREA, &swap);



-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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