Security in Ganeti
==================
+Documents Ganeti version 2.7
+
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, drbd devices,
-starting instances, etc. Running as root does not mean setuid, but that
-you need to be root to run the cluster commands.
+Up to version 2.3 all Ganeti code ran as root. Since version 2.4 it is
+possible to run all daemons except the node daemon as non-root users by
+specifying user names and groups at build time. The node daemon
+continues to require root privileges to create logical volumes, DRBD
+devices, start instances, etc. Cluster commands can be run as root or by
+users in a group specified at build time.
Host issues
-----------
- 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,
+- 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
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
+ - 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
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:
+Note that only the SSH key will allow other machines to run any command
+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
+- run well-defined SSH commands on other nodes in the cluster
+- scripts under the ``/etc/ganeti/hooks`` directory
+- scripts under the ``/etc/ganeti/restricted-commands`` directory, if
+ this feature has been enabled at build time (see below)
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.
+``/etc/ganeti/hooks`` and ``/etc/ganeti/restricted-commands``
+directories are supervised and only trusted sources can populate them.
+
+Restricted commands
+~~~~~~~~~~~~~~~~~~~
+
+The restricted commands feature is new in Ganeti 2.7. It enables the
+administrator to run any commands in the
+``/etc/ganeti/restricted-commands`` directory, if the feature has been
+enabled at build time, subject to the following restrictions:
+
+- No parameters may be passed
+- No absolute or relative path may be passed, only a filename
+- The ``/etc/ganeti/restricted-commands`` directory must
+ be owned by root:root and have mode 0755 or stricter
+- Executables must be regular files or symlinks, and must be executable
+ by root:root
+
+Note that it's not possible to list the contents of the directory, and
+there is an intentional delay when trying to execute a non-existing
+command (to slow-down dictionary attacks).
+
+Since for Ganeti itself this functionality is not needed, and is only
+provided as a way to help administrate or recover nodes, it is a local
+site decision whether to enable or not the restricted commands feature.
+
+By default, this feature is disabled.
+
Cluster issues
--------------
-As told above, there are multiple ways of communication between cluster
-nodes:
+As mentioned 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
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 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.
+traffic (this is supported in Ganeti through the use of a secondary
+interface) which is not routed outside the cluster. DRBD connections are
+protected from erroneous connections to other machines (as may happen
+due to software issues), 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
+The command-line tools to master daemon communication is done via a
+UNIX socket, whose permissions are reset to ``0660`` 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.
+Conf daemon
+-----------
+
+In Ganeti 2.7, the ``confd`` daemon (if enabled at build time), serves
+both network-originated queries (about the static configuration) and
+local (UNIX socket) queries (about the run-time configuration; answering
+these means talking to other cluster nodes, which makes use of the
+internal RPC SSL certificate). This makes it a bit more sensitive to
+bugs (a remote attacker could get direct access to the intra-cluster
+RPC), so to harden security it's recommended to:
+
+- disable confd at build time if it's not needed in your setup
+- otherwise, configure Ganeti (at build time) to use separate users, so
+ that the confd daemon doesn't also have access to the server SSL/TLS
+ certificates
+
+It is planned to split the two functionalities (local/remote querying)
+of confd into two separate daemons in a future Ganeti version.
+
Remote API
----------
Starting with Ganeti 2.0, Remote API traffic is encrypted using SSL/TLS
-by default. It supports Basic authentication as per :rfc:`2617`.
+by default. It supports Basic authentication as per :rfc:`2617`. Users
+can be granted different capabilities. Details can be found in the
+:ref:`RAPI documentation <rapi-users>`.
Paths for certificate, private key and CA files required for SSL/TLS
will be set at source configure time. Symlinks or command line
------------
When running KVM instances under Ganeti three security models ara
-available: 'none', 'user' and 'pool'.
+available: "none", "user" and "pool".
-Under security model 'none' instances run by default as root. This means
+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
+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
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
+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
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.
+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::
projects / ganeti-local / blobdiff