[OLPC Security] Bitfrost and dual-boot

Bobby Powers bobbypowers at gmail.com
Thu May 29 19:31:11 EDT 2008

On Fri, May 30, 2008 at 12:39 AM, C. Scott Ananian <cscott at laptop.org>

> On Thu, May 29, 2008 at 6:03 PM, Michael Stone <michael at laptop.org> wrote:
> > On Thu, May 29, 2008 at 05:53:49PM -0400, Michael Stone wrote:
> >> On Thu, May 29, 2008 at 02:58:07PM -0600, Jameson Chema Quinn wrote:
> >> In recent builds, any process running as user OLPC can execute code as
> >> uid 0 via the setuid-0 user-olpc-executable /usr/bin/sudo.
> >
> > A small correction: in recent builds, /bin/su is 04550 root/wheel, user
> > olpc is a member of wheel, and /usr/bin/sudo is a thin wrapper around
> > /bin/su.
> And to elaborate: the idea is that untrusted code should not be
> running as the 'olpc' user: 'olpc' is a trusted account.  Activities
> run/should be running as their own unique UUIDs, which are isolated
> from the olpc account.
> As to some other issues brought up:
> * Windows runs from an SD card, but there is not much space left on
> that SD card to store user files.  User files are stored in NAND at
> the moment.  In the dual-boot scenario which OFW2 will enable, we will
> either partition the NAND (likely also expand amount on onboard NAND),
> or limit Windows to the storage on the SD card (probably necessitating
> an increase in the size of the SD card).  None of this has been
> decided yet.

Did I miss something?  I was under the impression that the XO uses JFFS2 on
the NAND.  If we're worried about Windows malware messing with files on the
NAND, won't they have to be able to mount the volume first?  I only did a
quick google search, but I didn't find any Windows JFFS2 implementation.


> * It is worth separating out the various bitfrost protections.
> Initial activation security is implemented by OFW; it doesn't matter
> whether windows or linux is running after the firmware cedes control.
> Other bitfrost protections are OS-dependent, and you are likely to
> give up at least some security when you install Windows on the XO.
>  --scott
> --
>  ( http://cscott.net/ )
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