PolicyKit is an application framework that acts as a negotiator between the
unprivileged user session and the privileged system context. Whenever a
process from the user session tries to carry out an action in the system
context, PolicyKit is queried. Based on its configuration—specified in a
so-called “policy”—the answer could be
“yes”, “no”, or “ authentication
needed”. Unlike classical privilege authorization programs such as
sudo, PolicyKit does not grant
root permissions to an entire process,
following the “least privilege” concept.
At the moment, there are two PolicyKit versions available with openSUSE
in parallel: the “old”
At the moment, not all applications requiring privileges make use of PolicyKit. In the following the most important policies available on openSUSE® are listed.
|Set scheduling priorities for the PulseAudio daemon|
|Controlling dial-up connections|
|Add, remove, edit, enable or disable printers|
|Modify system and mandatory values with GConf|
|Change the system time|
|Manage and modify local virtualized systems|
|Apply and modify connections|
|Read and change privileges for other users|
|Update and remove packages|
|Wake on LAN|
|Mount or unmount fixed, hotpluggable and encrypted devices|
|Eject and decrypt removable media|
|Enable or disable WLAN|
|Enable or disable Bluetooth|
|Stop, suspend, hibernate and restart the system|
|Undock a docking station|
|Change the system time and language|
Every time a PolicyKit-enabled process carries out a privileged operation, PolicyKit is asked whether this process is entitled to do so. The answer PolicyKit gives depends on the policy defined for this process. It can be “yes”, “no”, or “authentication needed”. By default, a policy contains “implicit” privileges, which automatically apply to all users. It is also possible to specify “explicit” privileges which apply to a specific user.
Implicit privileges can be defined for any, active, and inactive sessions. An active session is the one in which you are currently working. It becomes inactive when you switch to another console for example. When setting implicit privileges to “no”, no user is authorized, whereas “yes” authorizes all users. However, in most cases it is useful to demand authentication.
A user can either authorize by authenticating as
root or by
authenticating as self. Both authentication methods exist in four
The user always has to authenticate
The authentication is bound to the instance of the program currently running. Once the program is restarted, the user is required to authenticate again.
The authentication dialog box offers a check button. If checked, the authentication is valid until the user logs out.
The authentication dialog box offers a check button. If checked, the user has to authenticate only once.
Explicit privileges can be granted to specific users. They can either be granted without limitations, or, when using constraints, limited to an active session and/or a local console.
It is not only possible to grant privileges to a user, a user can also be blocked. Blocked users will not be able to carry out an action requiring authorization, even though the default implicit policy allows authorization by authentication.
To modify implicit privileges or to set explicit ones, you can either use the graphicaltool available in the Advanced tab of the KDE System Settings, use the command line tools shipped with PolicyKit, or modify the configuration files. While the GUI and the command line tools are a good solution for making temporary changes, editing the configuration files should be the preferred way to make permanent changes.
|The graphical GNOMEtool|
The graphicaltool available with GNOME is for the old PolicyKit. Better use the above mentioned tools.
At the moment, there are two PolicyKit versions available in parallel with
openSUSE: the “old”
and the “new”
(polkit-1), which is a re-write of the old
PolicyKit) comes with two command line
tools for changing implicit privileges and for assigning explicit
privileges. Each existing policy has got a speaking, unique name with
which it can be identified and which is used with the command line
tools. List all available policies with the command
List and modify implicit privileges. Using this command you can also reset all policies to the default value. When invoked with no parameters, the command polkit-action shows a list of all policies. See man 1 polkit-action for more information.
Inspect, grant, block and revoke explicit privileges. To print a
list of explicit privileges for a specific user, use the command
polkit-auth --explicit-detail --user
USER has to be replaced by a valid
username. If the
--user option is left out,
privileges for the user executing the command are shown. See
man 1 polkit-auth for more information.
|Restrictions of polkit-action on openSUSE|
Using the option
For more information about
Adjusting privileges by modifying configuration files is useful when you want to deploy the same set of policies to different machines, for example to the computers of a specific team. It is possible to change implicit as well as explicit privileges by modifying configuration files.
openSUSE ships with two sets of default authorizations located in
.standard file defines privileges suitable for
most desktop systems. It is active by
.restrictive set of
privileges is designed for machines administrated
it by setting
/etc/sysconfig/security and run
Do not modify these two files.
In order to define your custom set of privileges, use
defined here will always take precedence over the ones defined in the
other configuration files. To define a privilege, add a line for each
policy with the following format:
For a list of all privilege names available, run the command polkit-action. The following values are valid for the session parameters:
user needs to authenticate with own password every time the privilege is requested
user needs to authenticate with own password once per session, privilege is granted for the whole session
user needs to authenticate with own password once, privilege is granted for the current and for future sessions
user needs to authenticate with
root password every time the
privilege is requested
user needs to authenticate with
root password once per
session, privilege is granted for the whole session
user needs to authenticate with
root password once, privilege
is granted for the current and for future sessions
Run set_polkit_default_privs to activate your settings.
Explicit privileges can be set in
/etc/PolicyKit/PolicyKit.conf. This configuration
file is written in XML using the PolicyKit DTD. The file that is shipped
with openSUSE already contains the necessary headers and the root
<config>. Place your edits inside the
Specify an action or a user.
match knows two
but only a single attribute is allowed. Use nested
match statements to combine attributes. POSIX
Extended Regular Expressions are allowed as attribute values.
Specify one or more login names. Separate multiple names by the “|” symbol.
Specify a policy by it's unique identifier. To get a list of all available policy identifiers use the command polkit-action.
Specify the answer PolicyKit will return. Takes a single attribute,
result= with one
of the values listed under
Section 126.96.36.199, “Modifying Configuration Files for Implicit Privileges”.
Specify users or groups allowed to authorize with their own password
where normally the
root password would be required. Takes the
only one may be used at a time. Multiple attribute values must be
separated by “|”, Extended POSIX Regular Expressions
are not supported. Applies to all policies when used at the top
level, or to specific policies when used within
Example 9.1. An example
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE pkconfig PUBLIC "-//freedesktop//DTD PolicyKit Configuration 1.0//EN" "http://hal.freedesktop.org/releases/PolicyKit/1.0/config.dtd"> <config version="0.1"> <match action="org.freedesktop.packagekit.system-update"> <match user="tux"> <return result="yes"/> </match> </match> <match action="org.freedesktop.policykit.*"> <match user="tux|wilber"> <return result="no"/> </match> </match> <define_admin_auth group="administrators"/> </config>
The first three lines of the config file are the XML header. These lines are already present in the template file, leave them untouched.
The XML root element must always be present. The attribute
A statement granting the user tux the privilege to update packages via PackageKit without having to authorize.
Withdraw privileges for all PolicyKit related policies from the users tux and wilber.
This statement allows all members of the group
Each application supporting PolicyKit comes with a default set of implicit policies defined by the application's developers, the so-called “upstream defaults”. The privileges defined by the upstream defaults are not necessarily the ones that are activated by default on openSUSE. openSUSE comes with a predefined set of privileges (see Section 188.8.131.52, “Modifying Configuration Files for Implicit Privileges” for more information) that is activated by default, overriding the upstream defaults.
Since the Authorization tool and the PolicyKit command line utilities always
operate on the upstream defaults, openSUSE comes with the
command-line tool set_polkit_default_privs that
resets privileges to the values defined in
set_polkit_default_privs will only reset policies
that are set to the upstream defaults. To reset all policies to the
upstream defaults first and then apply the openSUSE defaults, run
the following command:
rm -f /var/lib/PolicyKit-public/* && set_polkit_default_privs
In order to apply the openSUSE defaults, make sure