Security in Ganeti ~~~~~~~~~~~~~~~~~~ Ganeti was developed to run on internal, trusted systems. As such, the security model is all-or-nothing. All the Ganeti code runs as root, because all the operations that Ganeti is doing require privileges: creating logical volumes, md arrays, starting instances, etc. Running as root does not mean setuid, but that you need to be root to run the cluster commands. Host issues ----------- For a host on which the Ganeti software has been installed but which has not been joined in a cluster, there are no changes to the system. For a host that has been joined to the cluster, there are very important changes: - the host will have its ssh host key replaced with the one of the cluster (which is the one the initial node had at the cluster creation) - root will have added to its authorized_keys file a public key which grants access to all other nodes in the cluster, and furthermore it will also get the private part of this key, which will allow it to login to the other nodes in the cluster (its previous private key will be backed up) - the Ganeti node daemon will accept RPC requests from any host which has the cluster shared secret, and the operations it will do as a result of these requests are: - running commands under the /etc/ganeti/hooks directory - creating DRBD disks between it and the IP it has been told - overwrite a defined list of files on the host As you can see, as soon as a node is joined, it becomes equal to all other nodes in the cluster, and the security of the cluster is determined by the weakest node. Note that only the ssh key will allow other machines to run random commands on this node; the RPC method will run only: - well defined commands to create, remove, activate logical volumes, DRBD disks, md arrays, start/stop instances, etc; - run ssh commands on other nodes in the cluster, again well-defined - scripts under the /etc/ganeti/hooks directory It is therefore important to make sure that the contents of the /etc/ganeti/hooks directory is supervised and only trusted sources can populate it. Cluster issues -------------- As told above, there are multiple ways of communication between cluster nodes: - ssh-based, for high-volume traffic (image dumps) or for low-level command (restart the Ganeti node daemon) - python-twisted based, for the usual operation - DRBD traffic, for real-time disk replication traffic The ssh traffic is protected (after the initial login to a new node) by the cluster-wide shared ssh key. The python-twisted traffic is secured by SSL and two pre-conditions: the client will refuse to connect to servers which don't have the cluster-wide shared SSL certificate, and server will not allow clients which don't have the cluster-wide shared secret. The DRBD traffic is not protected by anything, as the version of DRBD we require (0.7) does not have any protections. It's therefore recommended to implement host-level firewalling or to use a separate range of IP addresses for the DRBD traffic (this is supported in Ganeti) which is not routed outside the cluster.