The other side of the moon

Watching the twitter feed about #jsconf shows a lot of people tweeting about #poopin. Turns out that someone's been stealing twitter cookies using a firesheep like tool and tweeting on their behalf. The tweets aren't malicious in nature, and are geared more at educating the user about the need to use SSL or some kind of encrypted tunnel when tweeting over untrusted wireless connections.

Here's the problem. Even people who do know the risks, and take the trouble to use twitter over SSL will get caught because of certain bugs with twitter's handling of their SSL pages.

If you visit https://mobile.twitter.com/, this is what you'd get: (shown in a browser so I could hilight the URL bar)

Click Sign in and this is what you get:

Sign in, and this is what you get:

Notice that the post sign-in URL is no longer https, but is now http.

At various points of time, trying this through my mobile phone, I get redirected from an https site to an http site when I do some of the following:

• Replying to a tweet
• Replying to a direct message (seems to be fixed)
• Retweeting (with/without? JavaScript)

If you search through the page source on https://mobile.twitter.com/ for the string "http://", you'll find a few instances in comments, but then these interesting ones in a JSON object:

"twitterApiBase":"http://api.twitter.com"
"apiBase":"http://api.local.twitter.com:9000"
"twitterBase":"http://twitter.com"
"mobileBase":"http://mobile.twitter.com"

I haven't examined the code in detail to see how these are used, but it seems to suggest that at least some calls are going out over http, and since they're all on the twitter.com domain, your twitter cookies get sent along.

Now this is only the twitter mobile website. Mobile clients could be another matter, and the desktop site could also have problems. I haven't tested. Personally, I try to either use a VPN, or only tweet using SMS, but I have been caught by something like this before (at FOSS.IN/2010) which is when I started to study the problem.

Also, it doesn't matter if you've configured twitter to always use HTTPS. It still has this problem.