May 9, 2005
Yesterday, an article on Slashdot about Dashboard widgets got my attention. It has been discovered that widgets pose a possible threat to users’ systems, as they are automatically run when downloaded. A specially crafted web page can direct your browser to download a widget, and Safari’s default behavior is to decompress the .zip archive. The Finder recognizes the .wdgt extension of the newly unzipped file, and launches the widget. In most cases, this makes for a very user-friendly Dashboard experience. However, user-friendliness almost always comes at a cost. Any code contained within the widget gets run, and that’s where the threat comes in. Some code gets run on the target system without any action on the user’s part, other than loading a web page in Safari.
Widgets do have a security layer provided by Apple, and it is built into the Info.plist files within each widget. A standard widget has no access to the internet, the command-line, files outside the widget bundle, Java applets, browser plugins, or widget plugins. In short, without your permission, a widget is effectively in its own sandbox and can do nothing harmful. When a widget needs access to one or more of these resources, it asks for your permission upon launch. When you click “Accept”, the widget can do whatever it needs.
From a security-oriented point of view, I think the main problem with the widget security layer is that the would-be “attacker,” a widget with bad intentions, defines its own security limitations. Mentioned above, each widget’s security is controlled by the Info.plist file written by it’s author and stored inside the widget bundle. A better solution might be to present the user with a dialog that details what resources the widget is requesting, allowing the user to decide what the widget should be allowed to do. This problem is made worse by an overly simple security interface. Different levels of security controlled by one “Accept” button. If the widget is going to define it’s own security limitations and the user will only see one button for any or all of them, why have more than one level of security? A single “AllowFullAccess” key in the Info.plist file would suffice. Future versions of Dashboard may see a security preference where users can control the level of access they would like widgets to have. This may be a bit of a problem, though, because not all users are aware of what a widget needs to do it’s job, and they really shouldn’t have to know. A solution lies somewhere between what the user knows about the inner workings of a widget and what security allowances are necessary for the widget to function. At best, the user needs to be able to easily control what a widget can do without knowing how it works. This is the type of situation in which Apple’s wizards excel, and I look forward to an elegant yet effective solution.
So what can you do to protect yourself right now? The front line for stopping harmful widgets from automatically installing themselves is to change your Safari download settings, as Safari expands widget archives upon download. In Safari’s “General” preferences tab, uncheck “Open ‘Safe’ files after downloading. With this unchecked, all widgets and files that download and would normally be auto-opened are simply saved to your default download location in their respective format. While you can still “infect” yourself by opening the archive and running the widget, nothing happens automatically without your permission. Turning off the opening of “safe” files may cause you to go through one more step after downloading something, but your computer’s security is worth the time it takes to switch out of Safari and examine a file before you run it.
The second thing you can do to help protect yourself is learn where widgets are stored in Mac OS X. While widgets can be run from any location via a double-click, they aren’t listed in the Widget Bar (which is activated by clicking the plus symbol in the lower-left of Dashboard). Widgets listed there are kept in the main Library folder inside the Widgets folder, at /Library/Widgets/ inside your boot drive. Optionally, widgets can be kept in separate folders for each user, under your Home folder, then following the same structure above. You can add or remove widgets from either folder, and the Widget Bar will be updated. Stephan.com, the origin of the widget security threat report, claims that “the Dashboard bar is not very good about updating when a widget is removed, but eventually it figures things out.” From my own testing, though, I find that the Widget Bar gets updated as soon as you add or remove widgets and activate it again. Alternatively, you could use Widget Manager to control all the widgets you use.
Finally, you can also learn how to stop an active widget in its tracks. By opening Activity Monitor, in the /Applications/Utilities/ folder, you can see all current processes running on your machine. If you type “dashboard” into the “Filter” search field at the top, you will filter the process list to only dashboard widgets (and whatever else may happen to have “dashboard” in its title). Using the list of widgets, you can click on one and click the red “Quit Process” button, then “Force Quit,” and that widget will be stopped, regardless of what it was doing. While not the best solution, it’s a fairly simple way to end an annoying widget that just won’t quit.
Update: Several other sites commented on the widget problem:
- The Unofficial Apple Weblog: The Problem With Widgets (Part 1, Part 2)
- Macworld:News: Dashboard: Widget (In)Security
- Macworld:News: ‘Zaptastic’ widget demonstrates Dashboard exploit
- The Mac Observer: Developer Demonstrates Dashboard Exploit