Commit 4e9dcb8a authored by Guido Trotter's avatar Guido Trotter
Browse files

security.rst: add a KVM security section


Signed-off-by: default avatarGuido Trotter <ultrotter@google.com>
Reviewed-by: default avatarIustin Pop <iustin@google.com>
parent 76431533
......@@ -99,6 +99,48 @@ Paths for certificate, private key and CA files required for SSL/TLS
will be set at source configure time. Symlinks or command line
parameters may be used to use different files.
KVM Security
------------
When running KVM instances under Ganeti three security models ara
available: 'none', 'user' and 'pool'.
Under security model 'none' instances run by default as root. This means
that, if an instance gets jail broken, it will be able to own the host
node, and thus the ganeti cluster. This is the default model, and the
only one available before Ganeti 2.1.2.
Under security model 'user' an instance is run as the user specified by
the hypervisor parameter 'security_domain'. This makes it easy to run
all instances as non privileged users, and allows to manually allocate
specific users to specific instances or sets of instances. If the
specified user doesn't have permissions a jail broken instance will need
some local privilege escalation before being able to take over the node
and the cluster. It's possible though for a jail broken instance to
affect other ones running under the same user.
Under security model 'pool' a global cluster-level uid pool is used to
start each instance on the same node under a different user. The uids in
the cluster pool can be set with ``gnt-cluster init`` and ``gnt-cluster
modify``, and must correspond to existing users on all nodes. Ganeti
will then allocate one to each instance, as needed. This way a jail
broken instance won't be able to affect any other. Since the users are
handed out by ganeti in a per-node randomized way, in this mode there is
no way to make sure a particular instance is always run as a certain
user. Use mode 'user' for that.
In addition to these precautions, if you want to avoid instances sending
traffic on your node network, you can use an iptables rule such as::
iptables -A OUTPUT -m owner --uid-owner <uid>[-<uid>] -j LOG \
--log-prefix "ganeti uid pool user network traffic"
iptables -A OUTPUT -m owner --uid-owner <uid>[-<uid>] -j DROP
This won't affect regular instance traffic (that comes out of the tapX
allocated to the instance, and can be filtered or subject to appropriate
policy routes) but will stop any user generated traffic that might come
from a jailbroken instance.
.. vim: set textwidth=72 :
.. Local Variables:
.. mode: rst
......
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