On Mon, 6 Aug 2001 21:12:16 -0700
Steve VanDevender <stevev@efn.org> wrote:
SV> Justin Guyett writes:
>> On Tue, 7 Aug 2001, David Spreen wrote:
>>
>> > I was just searching for swap-encryption-solutions in the lkml-archive.
>> > Did I get the point saying ther's no way to do swap encryption
>> > in linux right now? (Well, a swapfile in an encrypted kerneli
>> > partition r something like that is not really what I want to
>> > do I think).
>>
>> What's the benefit? Sure, attackers have to know that encrypted swap is
>> in use, and have to be able to find the key in memory, but they already
>> can do both if they're root, and non-root can't [shouldn't be able to]
>> read swap devices on a properly secured machine. Swap isn't meant for
>> storage across reboots/remounts, which is the only reason I can think of
>> for using encrypted loopback. Once it's mounted, unless you have to enter
>> the password for every write, or unless it locks after some period of
>> inactivity (locking swap and requiring the password to unlock it sounds
>> like a fun proposition when the vm needs to swap), it's insecure until
>> it's locked/unmounted again. Unmounting swap in a running system isn't
>> typical behavior.
SV> It does prevent one means of recovering possibly security-critical
SV> information for attackers who do have physical access to the machine.
Hmmm, if you have PHYSICAL access to the machine, you can simply reboot and type
"linux init=/bin/sh" and after it simply cat /etc/shadow and run John The Ripper....
Am i wrong?
SV> The obvious approach to me would to generate a random session key at
SV> boot time and use that for encrypting/decrypting swap pages. If the
SV> machine is unplugged and the disk pulled out, then the swap area on that
SV> disk could not be recovered the attacker, who presumably is prevented by
SV> other security measures from gaining root on the machine before it's
SV> unplugged to try to get that session key out of the kernel. I haven't
SV> studied this problem, though, so the real solution may be quite a bit
SV> more clever.
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