Sudo and USB flash drives

Colin Law clanlaw at
Sat Aug 18 20:41:09 UTC 2012

On 18 August 2012 21:02, Bill Stanley <bstanle at> wrote:
> On 08/18/2012 02:37 PM, Nils Kassube wrote:
>> Bill Stanley wrote:
>>> When I was repartitioning my HD and booting a USB flash drive, I
>>> found what may be a security flaw with sudo.  This problem might not
>>> affect computers with Linux installed so this might not be a
>>> problem.  It goes as follows...
>> [...]
>>> Do we really want to allow root access when booting to a flash drive?
>>> Maybe when booting from a USB drive or a CD-ROM, sudo should match
>>> the root (sudo) password that is on the Hard drive.  Of course,
>>> since I did not have Linux installed yet, in this case sudo acted
>>> appropriately.
>> IMHO, there is no advantage if you check for an installed Linux and use
>> the root password from that partition. You pointed out the next
>> necessary check, i.e. find out the Windows admin password and use that
>> one, if there is only Windows on the machine. But what would you suggest
>> to do if there are Windows and Linux installed? What if the disk is
>> bought secondhand and you don't even know the password of the still
>> existing OS on that disk?
>> If the system isn't locked down and anyone can boot from external media,
>> it isn't safe anyway. Then why should an installation medium check for
>> existing passwords? IMHO that doesn't make much sense.
> The issue of multiple OS's which are multi-booted is another thing that
> occurred to me.  Which OS root (or admin) password do you choose?  It is a
> bit of a corundum.  Still, sudo should keep people without sudo access from
> executing sudo privilege programs.  If someone can easily get around sudo by
> booting off a flash drive what security is in that?  I think that the sudo
> people should think about that!

Even if the Ubuntu USB stick was modified in the way you suggest,
anyone could boot from the USB stick burned with another operating
system, or the gparted live cd or anything else that takes their fancy
and do anything they like to the system.  Once someone with malice in
their mind has access to the machine there is nothing that can be done
to stop them doing anything they like if they are clever enough.  Data
can be protected so that it cannot be read, by encrypting the disc,
but that is all.


> Bill Stanley
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