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" (see 'Anonymous' in
the table below) 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
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.