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< h1 > Client access control< / h1 >
< p >
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.
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< ul id = "toc" > < / ul >
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< h2 > < a id = "intro" > Access control introduction< / a > < / h2 >
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< p >
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.
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< p >
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
< code > virDomainSetSchedulerParametersFlags< / code > method will
check whether the client user has the < code > write< / code >
permission on the < code > domain< / code > 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 < code > virConnectListAllDomains< / code >
method will check the < code > search_domains< / code > on the < code > connect< / code >
object, but will also filter the returned < code > domain< / code >
objects to only those on which the client user has the
< code > getattr< / code > permission.
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< h2 > < a id = "drivers" > Access control drivers< / a > < / h2 >
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< p >
The access control framework is designed as a pluggable
system to enable future integration with arbitrary access
control technologies. By default, the < code > none< / code >
driver is used, which does no access control checks at
all. At this time, libvirt ships with support for using
< a href = "http://www.freedesktop.org/wiki/Software/polkit/" > polkit< / a > as a real access
control driver. To learn how to use the polkit access
driver consult < a href = "aclpolkit.html" > the configuration
docs< / a > .
< / p >
< p >
The access driver is configured in the < code > libvirtd.conf< / code >
configuration file, using the < code > access_drivers< / code >
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:
< / p >
< pre >
# augtool -s set '/files/etc/libvirt/libvirtd.conf/access_drivers[1]' polkit
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< p >
And to reset back to the default (no-op) driver
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< pre >
# augtool -s rm /files/etc/libvirt/libvirtd.conf/access_drivers
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< p >
< strong > Note:< / strong > changes to libvirtd.conf require that
the libvirtd daemon be restarted.
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< h2 > < a id = "perms" > Objects and permissions< / a > < / h2 >
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< p >
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
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< a href = "html/index.html" > API reference manual< / a >
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documentation for the API in question.
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