|  |  |  | polkit Reference Manual |  | 
|---|
| pkexecpkexec — Execute a command as another user | 
pkexec  [--version] [--disable-internal-agent] [--help]
pkexec  [ 
          --user
          username
         ]  PROGRAM  [ ARGUMENTS ...]
      pkexec allows an authorized user to
      execute PROGRAM as another
      user. If username is not specified,
      then the program will be executed as the administrative super
      user, root.
    
      Upon successful completion, the return value is the return value
      of PROGRAM. If the calling process is
      not authorized or an authorization could not be obtained through
      authentication or an error occured, pkexec
      exits with a return value of 127. If the authorization could not
      be obtained because the user dismissed the authentication
      dialog, pkexec exits with a return value of
      126.
    
      pkexec, like any other PolicyKit application,
      will use the authentication agent registered for the calling
      process. However, if no authentication agent is available, then
      pkexec will register its own textual
      authentication agent. This behavior can be turned off by passing
      the --disable-internal-agent option.
    
Executing a program as another user is a privileged operation. By default the required authorization (See the section called “REQUIRED AUTHORIZATIONS”) requires administrator authentication. In addition, the authentication dialog presented to the user will display the full path to the program to be executed so the user is aware of what will happen:
      The environment that PROGRAM will run
      it, will be set to a minimal known and safe environment in order
      to avoid injecting code
      through LD_LIBRARY_PATH or similar
      mechanisms. In addition the PKEXEC_UID
      environment variable is set to the user id of the process
      invoking pkexec. As a
      result, pkexec will not allow you to run
      X11 applications as another user since
      the $DISPLAY and $XAUTHORITY
      environment variables are not set. These two variables will be retained
      if the org.freedesktop.policykit.exec.allow_gui annotation
      on an action is set to a nonempty value; this is discouraged, though, and
      should only be used for legacy programs.
    
By default, the org.freedesktop.policykit.exec authorization is required unless an action definition file is present for the program in question. To require another authorization, it can be specified using the org.freedesktop.policykit.exec.path annotation on an action (See the section called “EXAMPLE” for details).
      To specify what kind of authorization is needed to execute the
      program /usr/bin/pk-example-frobnicate as
      another user, simply write an action definition file like this
    
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE policyconfig PUBLIC
 "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/PolicyKit/1/policyconfig.dtd">
<policyconfig>
  <vendor>Examples for the PolicyKit Project</vendor>
  <vendor_url>http://hal.freedesktop.org/docs/PolicyKit/</vendor_url>
  <action id="org.freedesktop.policykit.example.pkexec.run-frobnicate">
    <description>Run the PolicyKit example program Frobnicate</description>
    <description xml:lang="da">Kør PolicyKit eksemplet Frobnicate</description>
    <message>Authentication is required to run the PolicyKit example program Frobnicate (user=$(user), program=$(program), command_line=$(command_line))</message>
    <message xml:lang="da">Autorisering er påkrævet for at afvikle PolicyKit eksemplet Frobnicate (user=$(user), program=$(program), command_line=$(command_line))</message>
    <icon_name>audio-x-generic</icon_name> 
    <defaults>
      <allow_any>no</allow_any>
      <allow_inactive>no</allow_inactive>
      <allow_active>auth_self_keep</allow_active>
    </defaults>
    <annotate key="org.freedesktop.policykit.exec.path">/usr/bin/pk-example-frobnicate</annotate>
  </action>
</policyconfig>
      and drop it in the
      /usr/share/polkit-1/actions directory under
      a suitable name (e.g. matching the namespace of the action).
      Note that in addition to specifying the program, the
      authentication message, description, icon and defaults can be
      specified. Note that occurences of the strings
      $(user), $(program) and
      $(command_line) in the message will be
      replaced with respectively the user (of the form "Real Name
      (username)" or just "username" if there is no real name for the
      username), the binary to execute (a fully-qualified path,
      e.g. "/usr/bin/pk-example-frobnicate") and
      the command-line, e.g. "pk-example-frobnicate foo
      bar". For example, for the action defined above, the
      following authentication dialog will be shown:
    
      If the user is using the da_DK locale, the
      dialog looks like this:
    
      Note that pkexec does no validation of
      the ARGUMENTS passed
      to PROGRAM. In the normal case (where
      administrator authentication is required every
      time pkexec is used), this is not a problem
      since if the user is an administrator he might as well just
      run pkexec bash to get root.
    
      However, if an action is used for which the user can retain
      authorization (or if the user is implicitly authorized), such as
      with pk-example-frobnicate above, this
      could be a security hole. Therefore, as a rule of thumb,
      programs for which the default required authorization is
      changed, should never implicitly trust user input (e.g. like any
      other well-written suid program).
    
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.