POLKIT-AUTH(1) polkit-auth POLKIT-AUTH(1)
polkit-auth - Manage authorizations
polkit-auth [--obtain action] [--show-obtainable] [[--user user] --explicit]
[[--user user] --explicit-detail]
[[--user user] --grant action [--constraint constraint]*]
[[--user user] --block action [--constraint constraint]*]
[[--user user] --revoke action] [--version] [--help]
polkit-auth is used to inspect, obtain, grant and revoke PolicyKit authorizations. If
invoked without any options, the authorizations of the calling process will be printed.
Attempt to obtain an authorization through authentication for the given action. This
is only useful for implicit authorizations requiring authentication; e.g. when an
appropriate stanza in the defaults section of the .policy file for the action
The gained authorization will be constrained as much as possible using the constraints
specified in the section called "CONSTRAINTS". For example, on a system running
SELinux, if the caller runs uses this tool to obtain an authorization from a shell in
a desktop in an active session, then constraints for local, active, exe and
selinux_context will all be added.
If an Authentication Agent (such as the one from PolicyKit-gnome) is available in the
session, it will used for authentication unless the environment variable
POLKIT_AUTH_FORCE_TEXT is set. If the environment variable POLKIT_AUTH_GRANT_TO_PID is
set, the authorization will be granted to that process id instead of the invoking
process (e.g. the shell from which polkit-auth is launched).
Prints all actions that can be obtained via authentication and for which an
authorization does not exist.
[--user user] --explicit
Show explicit authorizations. Duplicates are not printed. If used with the --user
option, the authorization org.freedesktop.policykit.read is required.
[--user user] --explicit-detail
Show detailed information about explicit authorizations. In contrast to the
--explicit, duplicates are printed as several authorizations with different scope and
constraints may exist.
[--user user] --grant action [--constraint constraint]*
Grant an authorization for an action. This is different than --obtain insofar that the
defaults stanza of the .policy file is not consulted. Optionally, one or more
constraints on the granted authorization can be specified, see the section called
"CONSTRAINTS" for details. The authorization needed to grant authorizations is
[--user user] --block action [--constraint constraint]*
Grant an negative authorization for an action. Negative authorizations are normally
used to block users that would normally be authorized due to implicit authorizations.
Optionally, one or more constraints on the granted authorization can be specified, see
the section called "CONSTRAINTS" for details. The authorization needed to grant
negative authorizations is org.freedesktop.policykit.grant if the "beneficiary" is
[--user user] --revoke action
Revoke all authorizations for an action. If the user is not specified the calling user
is used. The authorization org.freedesktop.policykit.revoke is needed to revoke
authorizations from other users.
Show version and exit.
Show this information.
One can put one or more constraints on an authorization. They are used to limit where the
authrorization applies. Presently the following constraints are supported
The caller must be in a session on a local console attached to the system. For example
processes that belong to remote XDMCP or ssh connections will fail to meet this
constraint and as such the authorization with such a constraint won't apply.
The caller must be in an active session. This is typically used with a local
constraint to ensure that the caller is only authorized if his session is in the
foreground. This is typically used for fast user switching (multiple sessions on the
same console) to prevent inactive sessions from doing privileged operations like
spying (using a webcam or a sound card) on the current active session.
The authorization is constrained to processes for where executable path (/proc/pid/exe
on Linux) matches the given path. See the section called "NOTES" for limitations on
why this may not be secure.
The authorization is constrained to processes for where their SELinux security context
matches the given context.
Note that the executable path for a process is not necessary reliable information and as
such shouldn't be relied on 100% to make a security decision. In fact, this information is
only trustworthy in situations where the given binary is securely locked down meaning that
1) it can't be ptrace(2)'d; 2) libc secure mode kicks in (e.g LD_PRELOAD won't work); 3)
there are no other attack vectors (e.g. GTK_MODULES, X11, CORBA, D-Bus) to patch running
code into the process.
In other words: the risk of relying on constraining an authorization to a path of an
executable is high. Suppose that the program /usr/bin/gullible obtains an authorization
via authentication for the action org.example.foo. We add a constraint to say that the
gained authorization only applies to processes for whom /proc/pid/exe points to
Now enter /usr/bin/evil. It knows that the program /usr/bin/gullible is not "securely
locked down" (per the definition in the above paragraph). So /usr/bin/evil simply sets
LD_PRELOAD and execs /usr/bin/gullible and it can now run code in a process where
/proc/pid/exe points to /usr/bin/gullible. Thus, the recently gained authorization for
org.example.foo applies. Also, /usr/bin/evil could use a host of other attack vectors to
run it's own code under the disguise of pretending to be /usr/bin/gullible.
Specifically for interpreted languages like Python and Mono it is the case that
/proc/pid/exe always points to /usr/bin/python resp. /usr/bin/mono. Thus, it's not very
useful to rely on that the result for this function if you want to constrain an
authorization to e.g. /usr/bin/tomboy or /usr/bin/banshee.
It is however possible to write programs that are "securely locked down" (per the
definition in the above paragraph); for example all properly written setuid and setgid
programs are written in this way.
PolicyKit ships with a collection of shell functions such that completion on users,
actions and constraints work when using the bash(1) shell. For completion to properly work
for polkit-auth, arguments should be entered in the order specified in this manual page;
for example. --user should be specified before --revoke to complete only on the
authorizations the given user has. Note that if the calling user lacks the
org.freedesktop.policykit.read authorization, the completion function will fall back to
completing on all registered actions.
Please send bug reports to either the distribution or the hal mailing list, see
http://lists.freedesktop.org/mailman/listinfo/hal. to subscribe.
PolicyKit(8), PolicyKit.conf(5), polkit-action(1)
PolicyKit August 2007 POLKIT-AUTH(1)