Libvirt's client access control framework allows administrators to setup fine grained permission rules across client users, managed objects and API operations. This allows client connections to be locked down to a minimal set of privileges.
In a default configuration, the libvirtd daemon has three levels of access control. All connections start off in an unauthenticated state, where the only API operations allowed are those required to complete authentication. After successful authentication, a connection either has full, unrestricted access to all libvirt API calls, or is locked down to only "read only" operations, according to what socket a client connection originated on.
The access control framework allows authenticated connections to
have fine grained permission rules to be defined by the administrator.
Every API call in libvirt has a set of permissions that will
be validated against the object being used. For example, the
virDomainSetSchedulerParametersFlags method will
check whether the client user has the write
permission on the domain object instance passed
in as a parameter. Further permissions will also be checked
if certain flags are set in the API call. In addition to
checks on the object passed in to an API call, some methods
will filter their results. For example the virConnectListAllDomains
method will check the search_domains on the connect
object, but will also filter the returned domain
objects to only those on which the client user has the
getattr permission.
The access control framework is designed as a pluggable
system to enable future integration with arbitrary access
control technologies. By default, the none
driver is used, which does no access control checks at
all. At this time, libvirt ships with support for using
polkit as a real access
control driver. To learn how to use the polkit access
driver consult the configuration
docs.
The access driver is configured in the libvirtd.conf
configuration file, using the access_drivers
parameter. This parameter accepts an array of access control
driver names. If more than one access driver is requested,
then all must succeed in order for access to be granted.
To enable 'polkit' as the driver:
# augtool -s set '/files/etc/libvirt/libvirtd.conf/access_drivers[1]' polkit
And to reset back to the default (no-op) driver
# augtool -s rm /files/etc/libvirt/libvirtd.conf/access_drivers
Note: changes to libvirtd.conf require that the libvirtd daemon be restarted.
Libvirt applies access control to all the main object types in its API. Each object type, in turn, has a set of permissions defined. To determine what permissions are checked for specific API call, consult the API reference manual documentation for the API in question.