NAME
pklocalauthority - PolicyKit Local Authority
DESCRIPTION
The Local Authority is the default PolicyKit authority implementation.
Configuration for the Local Authority and information pertaining to
authorization decisions are read from local files on the disk. One
design goal of the Local Authority is to split configuration items into
separate files such that 3rd party packages and users won't conflict
trying to edit the same files. This policy also ensures smooth upgrades
when distributing PolicyKit using a package management system.
Files shipped with PolicyKit and 3rd party packages (e.g. under package
manager control) typically have comments (such as "DO NOT EDIT THIS
FILE, it will be overwritten on update") telling the system
administrator that changes will be overwritten on update.
ADMINISTRATOR AUTHENTICATION
PolicyKit makes a distinction between user authentication (to make the
user in front of the system prove he really is the user) and
administrator authentication (to make the user in front of the system
prove he really is an administrator). Since various operating systems
(or even flavors of the same operating system) has different ways of
defining "administrator", the Local Authority provides a way to specify
what "administrator authentication" means.
By default, "administrator authentication" is defined as asking for the
root password. Since some systems, for usability reasons, don't have a
root password and instead rely on a group of users being member of an
administrative group that gives them super-user privileges, the Local
Authority can be configured to support this use-case as well.
Configuration for the Local Authority is read from files in the
/etc/polkit-1/localauthority.conf.d directory. All files are read in
lexigraphical order (using the C locale) meaning that later files can
override earlier ones. The file 50-localauthority.conf contains the
settings provided by the OS vendor. Users and 3rd party packages can
drop configuration files with a priority higher than 60 to change the
defaults. The configuration file format is simple. Each configuration
file is a key file (also commonly known as a ini file) with a single
group called [Configuration]. Only a single key, AdminIdentities is
read. The value of this key is a semi-colon separated list of
identities that can be used when administrator authentication is
required. Users are specified by prefixing the user name with
unix-user: and groups of users are specified by prefixing with
unix-group:. See the section called "EXAMPLES" for an example of a
configuration file.
DIRECTORY STRUCTURE
The Local Authority reads files with .pkla extension from all
directories located inside the /etc/polkit-1/localauthority and
/var/lib/polkit-1/localauthority directories. By default, the following
sub-directories are installed.
/etc/polkit-1/
`-- localauthority
|-- 10-vendor.d
|-- 20-org.d
|-- 30-site.d
|-- 50-local.d
`-- 90-mandatory.d
and
/var/lib/polkit-1/
`-- localauthority
|-- 10-vendor.d
|-- 20-org.d
|-- 30-site.d
|-- 50-local.d
`-- 90-mandatory.d
The /etc/polkit-1/localauthority hierarchy is inteded for local
configuration and the /var/lib/polkit-1/localauthority is intended for
3rd party packages.
Each .pkla file contains one or more authorization entries. If the
underlying filesystem supports file monitoring, the Local Authority
will reload information whenever .pkla files are added, removed or
changed.
Each directory is intended for a specific audience
10-vendor.d
Intended for use by the OS vendor.
20-org.d
Intended for the organization deploying the OS.
30-site.d
Intended for the site deploying the system.
50-local.d
Intended for local usage.
90-mandatory.d
Intended for the organization deploying the OS.
and new directories can be added/removed as needed.
As to regards to the content, each .pkla file is a standard key file
and contains key/value pairs in one or more groups with each group
representing an authorization entry. A .pkla file MUST be named by
using a scheme to ensure that the name is unique, e.g. reverse DNS
notation or similar. For example, if the organization is "Acme Corp"
needs to modify policy for the product "Frobnicator", a name like
com.acme.frobnicator.pkla would be suitable.
AUTHORIZATION ENTRY
Each group in a .pkla file must have a name that is unique within the
file it belongs to. The following keys are are recognized:
Identity
A semi-colon separated list of globs to match identities. Each glob
should start with unix-user: or unix-group: to specify whether to
match on a UNIX user name or a UNIX group name.
Action
A semi-colon separated list of globs to match action identifiers.
ResultActive
The result to return for subjects in an active local session that
matches one or more of the given identities. Allowed values are
similar to what can be used in the defaults section of .policy
files used to define actions, e.g. yes, no, auth_self,
auth_self_keep, auth_admin and auth_admin_keep.
ResultInactive
Like ResultActive but instead applies to subjects in inactive local
sessions.
ResultAny
Like ResultActive but instead applies to any subject.
ReturnValue
A semi-colon separated list of key/value pairs (of the form
key=value) that are added to the details of authorization result on
positive matches.
All keys specified above are required except that only at least one of
ResultAny, ResultInactive and ResultActive must be present. The
ReturnValue key is optional.
EVALUATION ORDER
When a Mechanism requests services from the Authority to check if a
given Subject is authorized for a given Action, the authorization
entries discussed above are consulted using the following algorithm.
The authorization entries from all .pkla files are ordered using the
following rules. First all the basename of all sub-directories (e.g.
30-site.d) from both the /etc/polkit-1/localauthority and
/var/lib/polkit-1/localauthority directories are enumerated and sorted
(using the C locale). If a name exists in both /etc and /var, the one
in /etc takes precedence. Then all .pkla files are read in order from
this list of sub-directories. For each .pkla file, authorizations from
each file are appended in order resulting in an ordered list of
authorization entries.
For example, given the following files
/var/lib/polkit-1
localauthority
10-vendor.d
10-desktop-policy.pkla
20-org.d
30-site.d
50-local.d
55-org.my.company.d
10-org.my.company.product.pkla
90-mandatory.d
/etc/polkit-1
localauthority
10-vendor.d
01-some-changes-from-a-subvendor.pkla
20-org.d
30-site.d
50-local.d
55-org.my.company.d
10-org.my.company.product.pkla
90-mandatory.d
the evaluation order of the .pkla files is:
1. 10-desktop-policy.pkla
2. 01-some-changes-from-a-subvendor.pkla
3. 10-org.my.company.product.pkla (the /var one)
4. 10-org.my.company.product.pkla (the /etc one)
When the list of authorization entries has been calculated, the
authorization check can be made. First, the user of the Subject is
determined and the groups that the user belongs are looked up. For each
group identity, the authorization entries are consulted in order. If
the authorization check matches the data from the authorization check,
then the authorization result from RequireAny, RequireInactive or
RequireActive is used and ReturnValue is added to the authorization
result.
Finally, the authorization entries are consulted using the user
identity in the same manner.
Note that processing continues even after a match. This allows for
socalled "negative authorizations", see the section called "EXAMPLES"
for further discussion.
EXAMPLES
The following .conf file
[Configuration]
AdminIdentities=unix-group:desktop_admin_r
that any user in the desktop_admin_r UNIX group can be used for
authentication when administrator authentication is needed. This file
would typically be installed in the /etc/polkit-1/localauthority.conf.d
directory and given the name 60-desktop-policy.conf to ensure that it
is evaluted after the 50-localauthority.conf file shipped with
PolicyKit. If the local administrator wants to override this (suppose
60-desktop-policy.conf was shipped as part of the OS) he can simply
create a file 99-my-admin-configuration.conf with the following content
[Configuration]
AdminIdentities=unix-user:lisa;unix-user:marge
to specify that only the users lisa and marge can authenticate when
administrator authentication is needed.
The following .pkla file grants authorization to all users in the staff
group for actions matching the glob com.example.awesomeproduct.*
provided they are in an active session on the local console:
[Normal Staff Permissions]
Identity=unix-group:staff
Action=com.example.awesomeproduct.*
ResultAny=no
ResultInactive=no
ResultActive=yes
If the users homer and grimes are member of the staff group but policy
requires that an administrator needs to authenticate every time
authorization for any action matching com.example.awesomeproduct.* is
required, one would add
[Exclude Some Problematic Users]
Identity=unix-user:homer;unix-user:grimes
Action=com.example.awesomeproduct.*
ResultAny=no
ResultInactive=no
ResultActive=auth_admin
and make sure this authorization entry is after the first one.
AUTHOR
Written by David Zeuthen davidz@redhat.com with a lot of help from many
others.
BUGS
Please send bug reports to either the distribution or the polkit-devel
mailing list, see the link
http://lists.freedesktop.org/mailman/listinfo/polkit-devel on how to
subscribe.
SEE ALSO
polkit(8)