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Thread: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

  1. #1
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    Question Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    I've a number of kiosk computer implemented my company's application which use firefox as front end user interface. All the users have to do is just staying on firefox to do their job. However when they click on firefox's "File" Menu and click open or save page as, the file dialog show up so they can explore the file system including my back end application files and mapped network drive which I seriously want to hide for security reason. I've found methods to hide those in nautilus using the .hidden file but it doesn't work in file/save dialog.


    As I'm very new to Linux, I created user accounts for them as standard users and I think all user has read access to file system by default (and should they need it to make operating system and application run properly?) Then can't I take read permission out from them? Please correct me if I'm wrong.

    So can i just prevent users from open file dialog? An approach i can think now is that are there any file system or library file that handle those file/save dialog? so that i can edit permission of them and the users will get permission denied dialog instead.


    If not possible, any suggestion to hide file system and mapped network folder in file dialog? Please help every suggestion will be appreciated. Thanks in advance.

  2. #2
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    Make the folders and files you want unviewable with restricted permissions
    something like
    Code:
    sudo chmod -R 700 <foldernamehere>
    which will make the folder viewable, writable, and executable for the owner, but no one else.
    But this is a very basic means.

    More here
    https://help.ubuntu.com/community/FilePermissions

    As a sidenote, I would only do this to files and folders you already own, and not ones owned by the system(root-owned).
    That can cause problems.
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  3. #3
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    Thanks deadflowr, I understand that I can modify the permission of files I want to restrict users access. However the problem is that the users have to have read access permission in order to make my application run properly but I want to close the "door" which allow user to see the files (and structure of directory). And the "door" I mean now is the file dialog (and save dialog) that show up when users click some menu on firefox such as "open" or "save page as". So that why I need some ways to disable these dialog or to hide file system in dialog.

    As I'm very new to Linux, please correct me if there are things I'm misunderstand.

  4. #4
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    Search "Addons" in Firefox for "kiosk". I saw a few extensions that might be useful. Here's one: https://addons.mozilla.org/en-US/firefox/addon/r-kiosk/.

    If your users must log on, consider segregating the files they need to access into one directory, creating one group for all your users, and giving the group and the individual users read access only to that directory. You'll need to delve into permissions, groups, etc., but I believe it's doable.
    Last edited by buzzingrobot; April 2nd, 2014 at 01:59 PM.

  5. #5
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    If you right-click on a tool bar like the top menu, you'll see that you can disable the menu entirely by unchecking the "Menu Bar" box. As long as users cannot modify the settings in your Firefox profile, they won't be able to get the menu back.

    Type "about:config" into the Firefox address bar and search for "toolbar". You'll see a number of relevant settings.

    That won't stop an informed user, though, since browsers also support the file:// URL. For instance, enter this URL into the address bar: file:///etc/passwd. (I tried using [url] tags, vBulletin apparently disables links like these.)

    So you probably also want to disable the address bar as well.

    Presumably the kiosk shows a main page with links to others. Just make that front page the default home page in Firefox. I'd probably also use some Javascript to revert to the front page after reaching a maximum idle time.
    Last edited by SeijiSensei; April 2nd, 2014 at 03:42 PM.
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  6. #6
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    Many Thanks to buzzingrobot, the "r-kiosk" Addon is very useful and partially answer what I'm looking for. However if users open pages that contain pdf content, firefox still show up pdf tool bar with a save button. Again, it open up file dialog and allows users to explore filesystem and mapped network drive that I need to hide. So I'm still looking for some ways to permanently disable the file dialog.

    For example, in the case below
    http://ubuntuforums.org/showthread.php?t=1363852
    they remove the file: /usr/lib/gtk-2.0/2.10.0/printbackends/libprintbackend-file.so to disable "print to file" function.

    And another case
    https://answers.launchpad.net/ubuntu...uestion/186540
    they edit permission of the folder: /usr/lib/gvfs/gvfsd-smb-browse to prevent users from clicking "Browse Network" button in Nautilus.

    Then my question is "are there something like that ?" , "Are there any file system or library file that handle those file/save dialog ?"
    So that i can edit permission of that files and the users will get permission denied dialog instead.

    ================================================== =======================

    Also thanks to SeijiSensei, that's valuable suggestion. I'll do more research about that.

  7. #7
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    You could compile Firefox from source, commenting out/removing the dialogues that trigger the file system access.

  8. #8
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    Re: Is it possible to prevent user from open/save file dialog in Ubuntu 12.04 LTS

    After all, deadflowr's answer is correct. But I did a slight difference, something like

    sudo chmod -R 773 <foldernamehere>

    Removing the read permission from the directory prevents users to list the contents of a directory. As a result, users cannot "see" the contents manually via file dialogue or nautilus but the application still can "read" them properly.

    Sorry deadflowr, I misunderstood at first because I'm not familiar with linux permission. Thanks everyone here for your help
    Last edited by dech_dragon; April 20th, 2014 at 11:29 AM. Reason: typo

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