svn commit: r261266 - in head: sys/dev/drm sys/kern sys/sys usr.sbin/jail

[Doug Ambrisko]

On Fri, Jan 31, 2014 at 06:28:27PM -0700, James Gritton wrote:
| On 1/31/2014 2:30 PM, Alexander Leidinger wrote:
| > On Fri, 31 Jan 2014 12:34:48 +0000 (GMT)
| > Robert Watson <rwatson at FreeBSD.org> wrote:
| >> On Wed, 29 Jan 2014, Alexander Leidinger wrote:
| >>>> It does.  I included a warning in jail.8 that this will pretty
| >>>> much undo jail security.  There are still reasons some may want to
| >>>> do this, but it's definitely not for everyone or even most people.
| >>>
| >>> It only "unjails" (= basically the same security level as the
| >>> jail-host with the added benefit of the flexibility of a jail like
| >>> easy moving from one system to another) the jail which has this
| >>> flag set. All other jails without the flag can not "escape" to the
| >>> host.
| >>>
| >>> I also have to add that just setting this flag does not give access
| >>> to the host, you also have to configure a non-default devfs rule
| >>> for this jail (to have the devices appear in the jail).
| >>
| >> This is not correct: devices do not need to be delegated in devfs for
| >> PRIV_IO to allow bypass of the Jail security model, due to sysarch()
| >> and the Linux-emulated equivalent, which turn out direct I/O access
| >> from a user process without use of a device node.
| >
| > Ok, then it is just the non-default flag, not the additional devfs part.
| >
| > I agree with your other post that we are better of to document better
| > what it means if an admin allows kmem access for a specific jail.
| 
| I second the documentation route.  Yes, it's true that this option
| makes a totally insecure jail - at least one lacking the expected jail
| security additions.  But I think that while security is one of the
| primary purposes of jails, it's not the only purpose.  It should be
| possible to have a trusted "master jail" that still takes advantage of
| the encapsulation while allowing otherwise unsupported features such
| as a desktop.
| 
| The distinction of whether certain devices are required to break out
| of a jail with allow.kmem is something of a red herring - the fact is
| that anyone who wants this level of access is going to have the
| devices in place anyway.
| 
| I suppose "obviate" wasn't the best word for the situation.  Maybe
| something that starts with "WARNING: ..." is in order.

It's unfortunate that vimage requires jail.  I want to use vimage but
not have the security restrictions of a jail.  To do this I patched
jail to basically let everything through.  It would be nice to be
able to run jail in an insecure mode which I understand is a contradition.
I do use the jail infrastructure to set the uname*/getosreldate so
that a specific jail thinks it is FreeBSD version blah.  Then I can ssh
into that jail and pkg_add things, make ports etc.  I use this on
my laptop running current on the base.  My other jails run various
versions of FreeBSD.  I don't care about security in this case.

Thanks,

Doug A.