Re: [Xen-devel] RAM security

[Keir Fraser <keir@xxxxxxx>]

On 06/12/2010 07:35, "Jonathan Tripathy" <jonnyt@xxxxxxxxxxx> wrote:

> Just a few questions:
> 
> 1) By saying "the guest's responsibility", does this mean that
> CONFIG_XEN_SCRUB_PAGES=y is set in the DomU kernel config?

Yes.

> 2) Also, if a DomU was shutdown by xm destroy, obviously the DomU
> wouldn¹t scrub the RAM. However would Xen still scrub the RAM?

Xen always scrubs memory on behalf of a dead domain.

> 3) If the physical server was shutdown (e.g. plug pulled), I'm guessing
> this will presetn a problem?

Xen scrubs all memory during boot, unless told not to via a boot parameter.

> 4) Why doesn't Xen scrub the RAM before giving it to the DomU?

It does in the above circumstances. Otherwise it is up to the domU, and why
not.

 -- Keir

> Thanks
> 
> On 06/12/10 14:49, George Dunlap wrote:
>> I looked into this sometime this last year.  I believe the answer is
>> "no": the domain destruction routines will zero memory before handing
>> it back to Xen.
>> 
>> One potential data leak, however (last time I looked at this), is that
>> Xen does not scrub memory handed back by the balloon driver.  So if
>> the guest OS hasn't scrubbed it, and it contains sensitive
>> information, it may end up being assigned to another domain as-is
>> (either via ballooning or start-of-day domain creation).  At the
>> moment that's considered the guest's responsibility.
>> 
>>   -George
>> 
>> On Mon, Dec 6, 2010 at 2:35 PM, Jonathan Tripathy<jonnyt@xxxxxxxxxxx>  wrote:
>>> Hi Everyone,
>>> 
>>> In Xen, is a DomU able to access data in RAM which a previous DomU has
>>> stored in the past, but didn't "zero" it?
>>> 
>>> I understand that this is a problem with physical disks (using phy:/), just
>>> wondering if the same stands with RAM
>>> 
>>> Thanks
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
>>> 
>>> 
> 
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