Security in Ganeti
-~~~~~~~~~~~~~~~~~~
+==================
Ganeti was developed to run on internal, trusted systems. As such, the
security model is all-or-nothing.
Host issues
-----------
-For a host on which the Ganeti software has been installed, but not joined to a
-cluster, there are no changes to the system.
+For a host on which the Ganeti software has been installed, but not
+joined to 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)
- - A new public key will be added to root's authorized_keys file, granting
- root access to all nodes of the cluster. The private part of the key
- is also distributed to all nodes. Old files are renamed.
- - Communication between nodes is encrypted using SSL/TLS. A common
- key and certificate combo is shared between all nodes of the cluster.
- At this time, no CA is used.
- - The Ganeti node daemon will accept RPC requests from any host within the
- cluster with the correct certificate, 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
+
+- 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)
+- A new public key will be added to root's authorized_keys file,
+ granting root access to all nodes of the cluster. The private part of
+ the key is also distributed to all nodes. Old files are renamed.
+- Communication between nodes is encrypted using SSL/TLS. A common key
+ and certificate combo is shared between all nodes of the cluster. At
+ this time, no CA is used.
+- The Ganeti node daemon will accept RPC requests from any host within
+ the cluster with the correct certificate, 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
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 devices, start/stop instances, etc;
- - run SSH commands on other nodes in the cluster, again well-defined
- - scripts under the /etc/ganeti/hooks directory
+
+- well defined commands to create, remove, activate logical volumes,
+ drbd devices, 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
As told above, there are multiple ways of communication between cluster
nodes:
- - SSH-based, for high-volume traffic like image dumps or for low-level
- command, e.g. restarting the Ganeti node daemon
- - RPC communication between master and nodes
- - DRBD real-time disk replication traffic
+
+- SSH-based, for high-volume traffic like image dumps or for low-level
+ command, e.g. restarting the Ganeti node daemon
+- RPC communication between master and nodes
+- DRBD 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.
-RPC communication between the master and nodes is protected using SSL/TLS
-encryption. Both the client and the server must have the cluster-widely
-shared SSL/TLS certificate and verify it when establishing the connection
-by comparing fingerprints. We decided not to use a CA to simplify the
-key handling.
+RPC communication between the master and nodes is protected using
+SSL/TLS encryption. Both the client and the server must have the
+cluster-wide shared SSL/TLS certificate and verify it when establishing
+the connection by comparing fingerprints. We decided not to use a CA to
+simplify the key handling.
-The DRBD traffic is not protected by encryption. DRBD does not support
-traffic encryption. It's therefore recommended to implement host-level
+The DRBD traffic is not protected by encryption, as DRBD does not
+support this. 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. DRBD connections are protected from connecting to random other
-machines by using a shared secret exchanged via RPC requests when
-starting the device.
+cluster. DRBD connections are protected from connecting due to bugs to
+other machines, and from accepting connections from other machines, by
+using a shared secret, exchanged via RPC requests from the master to the
+nodes when configuring the device.
+
+Master daemon
+-------------
+
+The command-line tools to master daemon communication is done via an
+UNIX socket, whose permissions are reset to ``0600`` after listening but
+before serving requests. This permission-based protection is documented
+and works on Linux, but is not-portable; however, Ganeti doesn't work on
+non-Linux system at the moment.
Remote API
----------
-Starting with Ganeti 2.0, Remote API traffic is encrypted using SSL/TLS by
-default. It supports Basic authentication as per RFC2617.
-
-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.
+Starting with Ganeti 2.0, Remote API traffic is encrypted using SSL/TLS
+by default. It supports Basic authentication as per :rfc:`2617`.
+
+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.
+
+Inter-cluster instance moves
+----------------------------
+
+To move instances between clusters, different clusters must be able to
+communicate with each other over a secure channel. Up to and including
+Ganeti 2.1, clusters were self-contained entities and had no knowledge
+of other clusters. With Ganeti 2.2, clusters can exchange data if tokens
+(an encryption certificate) was exchanged by a trusted third party
+before.
+
+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 one 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
+.. fill-column: 72
+.. End:
projects / ganeti-local / blobdiff