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I'm designing an app that needs to configure iptables with root. Is there already some sort of framework that can be used to gain superuser access with an app or will i have to design my own?

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2 Answers 2

  1. Simplest way, start your application with sudo application name or

  2. Quoting from man pkexec

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"

             <vendor>Examples for the PolicyKit Project</vendor>

             <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_
               <message xml:lang="da">Autorisering er påkrævet for at afvikle PolicyKit eksemplet Frobnicate (user=$(user), program=$(program)
, command_line=$(command_line))</message>
               <annotate key="org.freedesktop.policykit.exec.path">/usr/bin/pk-example-frobnicate</annotate>

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:


           |                     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:


           |                     Autorisering                     [X] |
           |                                                          |
           |  [Icon]  Autorisering er påkrævet for at afvikle         |
           |          PolicyKit eksemplet Frobnicate                  |
           |                                                          |
           |          Et program forsøger at udføre en handling der   |
           |          kræver privilegier. Autorisering er påkrævet.   |
           |                                                          |
           |          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            |
           |                                                          |
           |                                [Annullér] [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).

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I would think it would be preferred to write a thin system dbus service to handle just the things that require root. Then send requests from the parts of your application that require root to said dbus service.

I don't have a ready to fire-off sample, but google does.

The tedious parts are:

You're writing a mini-app (the dbus service) and the application itself.

It adds about 2 files to your package iirc. The service file itself and the configuration file for the dbus service.

You would want to either provide privilege escalation to all users for said service OR you would want to include some kind of authentication/authorization.

Sort of a problem, but not really.

The upside is:

No prompt. It just works.

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Interesting. Do you have any sample code which does that? –  thefourtheye Jun 16 '13 at 9:46
@thefourtheye - If you really need sample code, this is how wicd-gtk communicates with the wicd daemon I believe. wicd is in repo. –  hbdgaf Jul 11 '13 at 13:54

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