On 07/14/2017 08:04 AM, Eric W. Biederman wrote:
Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> writes:
On 07/13/2017 08:38 PM, Eric W. Biederman wrote:
Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> writes:
On 07/13/2017 01:49 PM, Eric W. Biederman wrote:
My big question right now is can you implement Ted's suggested
restriction. Only one security.foo or secuirty.foo@... attribute ?
We need to raw-list the xattrs and do the check before writing them. I am fairly sure this can be done.
So now you want to allow security.foo and one security.foo@uid=<> or just a single one security.foo(@[[:print:]]*)?
The latter.
That case would prevent a container user from overriding the xattr on
the host. Is that what we want?
Most definitely. If a more privileged use has set secure.capable that
is better.
For limiting the number of xattrs and
getting that functionality (override IMA signature for example) the
former seems better...
I don't know about IMA. But my feeling is that we will only be dealing
with a single signing key, so I don't see how having multiple IMA xattrs
make sense. Could you explain that to me?
Admittedly I would need to construct and example where the user inside
the container doesn't want to share the public key with the host on a
file mounted from the host for some reason.
An example related to security.capability could be a Fedora Docker
container where the container is distributed with the ping tool
installed. The ping tool is installed with cap_net_admin,cap_net_raw+ep.
On a normal Fedora container I cannot use this tool due to my
capabilities bounding set not including cap_net_admin. So, I overwrite
this and set only cap_net_raw+ep and I can use for pinging. I may loose
some functionality on the way due to the lost cap_net_admin but I can
now use the tool. I guess the point is one can override the capabilities
set of a distributed container if the container is started with less
capabilities.
Stefan
For the former I now have the topmost patch here:
https://github.com/stefanberger/linux/commits/xattr_for_userns.v3
Thank you.
Eric
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