Attachment Filter

Description/Features

The Attachment Filter Plugin allows administrators to control which file types users may upload.

Installation

1. Download the AttachmentFilter.tar.
2. Untar it. (tar xvf AttachmentFilter.tar)
3. The tar contains 2 files of interest:
   1. The plugin jar (plugins-attachfilter.jar)
   2. An updated Atlassian class (AttachFileHelper.class) - Note: If you're feeling nervous about this, backup the Atlassian class somewhere before continuing)
4. Copy plugins-attachfilter.jar to [Confluence-DIR]/confluence/WEB-INF/lib/.
5. Copy AttachFileHelper.class to [CONFLUENCE-DIR]/confluence/WEB-INF/classes/com/atlassian/confluence/util/.
6. Restart Confluence

All attachments will be restricted All attachments will be filtered until you configure which ones you allow.

Not Upload Friendly The attachment filter plugin will not work correctly, if you attempt to install it by uploading it with the Plugins Administrative console. The plugin must be installed in WEB-INF/lib and Confluence must be restarted in order for the plugin to work correctly.

Configuration

After installation, all file uploads will be restricted! To allow filetypes:
1. Login as an administrator.
2. Go to the Administration Console.
3. Click the Customize Attachment Filter link (in the Configuration panel)
4. Add extensions by typing a comma seperated list of extensions into the textfield, and clicking the '+' button.
5. See the Help Tips panel on that page for further instructions.

Screenshots

Screenshots
Customization Screen Shot	Filtering Screen Shot

Future Improvements

Advanced Filetype Checking

This currently hasn't been implemented yet, although the UI for the Configuration page already has the stubs setup for it.
Currently, the AttachmentFilter simply checks the filename for a valid extension. If you're just trying to encourage your users towards following your company polices, that's fine. However, as a security feature, it lacks something. What's to stop someone from uploading an .exe file that's been renamed to say .jpg? So, if the use of this plugin is to protect the wiki from malicious users, then the files themselves have to be verified to be what they say they are.

As a quick fix, I think it would be possible to exec an existing app (like the Unix 'file' command) to do this checking for us.

So, changes that would allow this would be:

• Configuration page provides:
  • a way to turn this on
  • a way to tell the plugin where the 'file' command is located on the system (/usr/bin/file)
• The AttachmentFilter.isValidExtension method, now passes a candidate filename to the file command (via Runtime.exec), and compares the return value against what it's expecting.
  • Security concern: in order to do this we'll have to upload the file, so the file command can look at it. Does this mean we attach it, then remove it?

Filtering on a per Space basis

Currently, the Attachment Filter works only a global basis. Possibly, administrators might want to leverage this plugin on a per space basis.
I think the big issue here is providing

• a Configuration page from the Space Admin tab (so, adding another Web UI Plugin to do this)
• again, adjusting the AttachmentFilter.isValidExtension method to check for overriding Space configuration options.
• maybe a global setting to explicitly set non-overridable options. (A Global administrator might not want to allow anyone to let (for example) .exes anywhere. This might be especially important if non-global-admins had some Space administrative rights)