ubuntu sudoers改坏了。

       pkexec - 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:

           [IMAGE][1]

               +----------------------------------------------------------+

               |                     Authenticate                     [X] |

               +----------------------------------------------------------+

               |                                                          |

               |  [Icon]  Authentication is needed to run `/bin/bash'     |

               |          as the super user                               |

               |                                                          |

               |          An application is attempting to perform an      |

               |          action that requires privileges. Authentication |

               |          as the super user is required to perform this   |

               |          action.                                         |

               |                                                          |

               |          Password for root: [_________________________]  |

               |                                                          |

               | [V] Details:                                             |

               |  Command: /bin/bash                                      |

               |  Run As:  Super User (root)                              |

               |  Action:  org.freedesktop.policykit.exec                 |

               |  Vendor:  The PolicyKit Project                          |

               |                                                          |

               |                                  [Cancel] [Authenticate] |

               +----------------------------------------------------------+

       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">Kor 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 pakraevet 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:

           [IMAGE][2]

               +----------------------------------------------------------+

               |                     Authenticate                     [X] |

               +----------------------------------------------------------+

               |                                                          |

               |  [Icon]  Authentication is required to run the PolicyKit |

               |          example program Frobnicate                      |

               |                                                          |

               |          An application is attempting to perform an      |

               |          action that requires privileges. Authentication |

               |          is required to perform this action.             |

               |                                                          |

               |          Password: [__________________________________]  |

               |                                                          |

               | [V] Details:                                             |

               |  Command: /usr/bin/pk-example-frobnicate                 |

               |  Run As:  Super User (root)                              |

               |  Action:  org.fd.pk.example.pkexec.run-frobnicate        |

               |  Vendor:  Examples for the PolicyKit Project             |

               |                                                          |

               |                                  [Cancel] [Authenticate] |

               +----------------------------------------------------------+

       If the user is using the da_DK locale, the dialog looks like this:

           [IMAGE][3]

               +----------------------------------------------------------+

               |                     Autorisering                     [X] |

               +----------------------------------------------------------+

               |                                                          |

               |  [Icon]  Autorisering er pakraevet for at afvikle         |

               |          PolicyKit eksemplet Frobnicate                  |

               |                                                          |

               |          Et program forsoger at udfore en handling der   |

               |          kraever privilegier. Autorisering er pakraevet.   |

               |                                                          |

               |          Kodeord: [___________________________________]  |

               |                                                          |

               | [V] Detaljer:                                            |

               |  Bruger:   Super User (root)                             |

               |  Program:  /usr/bin/pk-example-frobnicate                |

               |  Handling: org.fd.pk.example.pkexec.run-frobnicate       |

               |  Vendor:   Examples for the PolicyKit Project            |

               |                                                          |

               |                                [Annuller] [Autorisering] |

               +----------------------------------------------------------+

       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).

       Written by David Zeuthen davidz@redhat.com with a lot of help from many

       others.

       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.

       polkit(8), pkaction(1), pkcheck(1)

        1. /usr/share/gtk-doc/html/polkit-1/pkexec-bash.png

        2. /usr/share/gtk-doc/html/polkit-1/pkexec-frobnicate.png

        3. /usr/share/gtk-doc/html/polkit-1/pkexec-frobnicate-da.png

ubuntu sudoers改坏了。

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

AUTHENTICATION AGENT

SECURITY NOTES

REQUIRED AUTHORIZATIONS

EXAMPLE

AUTHOR

BUGS

SEE ALSO

NOTES

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