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From John Sirois <j...@conductant.com>
Subject Re: Looking for feedback - Setting CommandInfo.user by default when launching tasks.
Date Tue, 29 Mar 2016 21:39:36 GMT
On Tue, Mar 29, 2016 at 3:26 PM, Bill Farner <wfarner@apache.org> wrote:

> If i'm understanding you correctly, that doesn't address preventing users
> from reading the credentials though.
>

It does:

Say:
/var/lib/aurora/creds 400 root

And then if the CommandInfo has user: aurora (executor user as Steve
suggested), it will get a copy of /var/lib/aurora/creds  in its sandbox
chowned to 400 aurora

Now aurora's executor (thermos), launches a task in role www-data
announcing for it using the cred.  The www-data user will not be able to
read the local sandbox 400 aurora creds.


> On Tue, Mar 29, 2016 at 1:52 PM, John Sirois <jsirois@apache.org> wrote:
>
> > On Tue, Mar 29, 2016 at 2:31 PM, Steve Niemitz <sniemitz@apache.org>
> > wrote:
> >
> > > So maybe we add it, but don't change the current default behavior?
> > >
> >
> > Could we use the CommandInfo.uris [1] to solve this?  IE: the scheduler
> > would need to learn the credential file path, and with that knowledge,
> the
> > local mesos (root) readable credential file could be specified as a uir
> > dependency for all launched executors (or bare commands).  IIUC, if the
> URI
> > if a file:// the local secured credentails file will be copied into the
> > sandbox where it can be read by the executor (as aurora).
> >
> > [1]
> >
> https://github.com/apache/mesos/blob/master/include/mesos/mesos.proto#L422
> >
> >
> > >
> > > On Tue, Mar 29, 2016 at 4:26 PM, Bill Farner <wfarner@apache.org>
> wrote:
> > >
> > > > I'm in favor of moving forward.  There's no requirement to use the
> > > > Announcer, and a non-root executor seems like a useful option.
> > > >
> > > > On Tue, Mar 29, 2016 at 1:00 PM, Steve Niemitz <sniemitz@apache.org>
> > > > wrote:
> > > >
> > > > > Makes sense, I guess it can be up to the cluster operator which
> model
> > > to
> > > > > choose.  Is there any interest in the feature I proposed or should
> I
> > > just
> > > > > drop it?  It's not a lot of code, but also it's not a requirement
> for
> > > > > anything we're working on either (the docker stuff however, is).
> > > > >
> > > > > On Tue, Mar 29, 2016 at 1:39 PM, Bill Farner <wfarner@apache.org>
> > > wrote:
> > > > >
> > > > > > That's correct - those credentials should require privileged
> > access.
> > > > > >
> > > > > > On Tue, Mar 29, 2016 at 10:25 AM, Steve Niemitz <
> > > > > > sniemitz@twitter.com.invalid> wrote:
> > > > > >
> > > > > > > Re: ZK credential files, thats an interesting issue, I
assume
> you
> > > > don't
> > > > > > > want the role user to be able to read it either, and only
root
> or
> > > > some
> > > > > > > other privileged user?
> > > > > > >
> > > > > > > On Tue, Mar 29, 2016 at 12:14 PM, Erb, Stephan <
> > > > > > > Stephan.Erb@blue-yonder.com>
> > > > > > > wrote:
> > > > > > >
> > > > > > > > I am in favor of your proposal. We offer less attack
surface
> if
> > > the
> > > > > > > > executor is not running as root.
> > > > > > > >
> > > > > > > > Interesting though, this introduces another security
problem:
> > The
> > > > > > > > credentials file in the incoming Zookeeper  ACL patch
(
> > > > > > > > https://reviews.apache.org/r/45042/) will have to
be
> readable
> > by
> > > > > > > > everyone. That feels a little bit like being back
to square
> > one.
> > > > > > > > ________________________________________
> > > > > > > > From: Steve Niemitz <sniemitz@apache.org>
> > > > > > > > Sent: Tuesday, March 29, 2016 17:34
> > > > > > > > To: dev@aurora.apache.org
> > > > > > > > Subject: Looking for feedback - Setting CommandInfo.user
by
> > > default
> > > > > > when
> > > > > > > > launching tasks.
> > > > > > > >
> > > > > > > > I've been working on some changes to how aurora submits
tasks
> > to
> > > > > mesos,
> > > > > > > > specifically around Docker tasks, but I'd also like
to see
> how
> > > > people
> > > > > > > feel
> > > > > > > > about making it more general.
> > > > > > > >
> > > > > > > > Currently, when Aurora submits a task to mesos, it
does NOT
> set
> > > > > > > > command.user on the ExecutorInfo, this means that
mesos
> > > configures
> > > > > the
> > > > > > > > sandbox (mesos sandbox that is) as root, and launches
the
> > > executor
> > > > > > > > (thermos_executor in our case) as root as well.
> > > > > > > >
> > > > > > > > What then happens is that the executor then chown()s
the
> > sandbox
> > > it
> > > > > > > creates
> > > > > > > > to the aurora role/user, and also setuid()s the runners
it
> > forks
> > > to
> > > > > > that
> > > > > > > > role/user.  However, the executor itself is still
running as
> > > root.
> > > > > > > >
> > > > > > > > My proposal / change is to set command.user to the
aurora
> role
> > by
> > > > > > > default,
> > > > > > > > which will cause the executor to run as that user.
 I've
> tested
> > > > this
> > > > > > > > already, and no changes are needed to the executor,
it will
> > still
> > > > try
> > > > > > to
> > > > > > > > chown the sandbox (which is fine since it already
owns it),
> and
> > > > > > setuid()
> > > > > > > > the runners it forks (again, fine, since they're already
> > running
> > > as
> > > > > > that
> > > > > > > > user).
> > > > > > > >
> > > > > > > > *The controversial part of this* however is I'd like
to
> enable
> > > this
> > > > > > > > behavior BY DEFAULT, and allow disabling it (reverting
to the
> > > > current
> > > > > > > > behavior now) via a flag to the scheduler.  My reasoning
here
> > is
> > > > two
> > > > > > > fold.
> > > > > > > >  1) It's a more secure default, preventing a compromised
> > executor
> > > > > from
> > > > > > > > doing things it shouldn't, and 2) we already have
a lot of
> > "flag
> > > > > > bloat",
> > > > > > > > and flags are hard enough to discover as they are.
 However,
> I
> > do
> > > > > > believe
> > > > > > > > this should be considered as a "breaking change",
> particularly
> > > > > because
> > > > > > of
> > > > > > > > finicky PEX extraction for the executor.
> > > > > > > >
> > > > > > > > I'd like to hear people's thoughts on this.
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>



-- 
John Sirois
303-512-3301

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