Slashdot Mirror
HTTPS Cookie Hijacking Not Just For Gmail
mikepery writes with a followup to last month's mention of a security vulnerability affecting Gmail accounts, which it seems understated the problem.
"I figure the Slashdot readership is the best place to reach a large number of
slacking admins and developers, so I want to announce that it's been 30 days
since my DEFCON presentation on HTTPS
cookie hijacking, and as such, it's now time to release the tool to a much
wider group. Despite what was initially
reported, neither the attack nor the tool
are gmail-specific, and many
other websites are vulnerable. So, if you maintain any sort of reasonable
looking website secured by
any SSL certificate (Sorry Rupert, you lose on both counts), even if it is just self-signed, you can contact me and I will provide you with a copy of the tool. Be sure to put 'CookieMonster' in the subject, without a space." (More below.)
"I'd also like to encourage security professionals and consultants to request a
copy of the tool for use in encouraging their clients to adopt
SSL properly for their websites. There's no possible way for me to reach
every site, but if convincing demonstrations can be given of the vulnerability
on an individual basis, perhaps that will drive the issue home much more than
the press alone has done. Heck, the tool might even land you a few new
clients."
If you want to manually examine a site you visit:
Clear all cookies.
Log in.
Clear all cookies marked as "SECURE" (in firefox, preferences->privacy->show cookies. Delete JUST the cookies marked as "Encrypted connections only").
Go back to the site. Can you act as if you are logged in? If so, the site is COMPLETELY insecure.
Test your net with Netalyzr
Comment removed based on user account deletion
In what way? We run a lot of stuff over our SIPR and I haven't really noticed any "limits" to what we've done. Hell, I even watch CNN over SIPR sometimes.
I run a few Django SSL-secured websites, and I noticed the default is to send insecure cookies for the session id (i.e. hijack-able cookies). I'm going to try to get on someone's case to make this information more widely available, because you have to turn on secure cookies with a "SESSION_COOKIE_SECURE = True" statement, which I never knew until I checked today. Doing this should secure any Django-powered site from this particular attack.
Three rights make a left. Freedom of speech, freedom of the press, freedom of assembly.
Many (most?) classified government systems require TEMPEST hardening, to specifically protect against your second point. Many government buildings which contain classified materials also require a similar hardening.
File Permissions: When the web server asks to write cookie, browser uses file permissions to create a group for that site, and allows only members of that group to read or write to that cookie. Either use the disk filesystem's permissioning, or reimplement a permissioning system within the browser profile, to be used only for cookies.
Requires giving the browser root access to the system (though you can mitigate this by running a jail or sandbox).
File Encryption: Using a public key encryption method, the content of cookie file is encrypted using the web site's private encryption key, and can only be decrypted by the web server.
I thought that's what SSL cookies do in the first place?
God invented whiskey so the Irish would not rule the world.
Because then every worm that looks for username@domain.cc would find it. Congrats on defeating the purpose by posting it, though.
There were a lot of 'email me's and talk about bad htps settings but not much content on really what needs to be done for fixing an existing site or properly setting up a new site to be secure.
Executive summary:
It is possible to set a single bit in a cookie sent to the browser which means "Only send this cookie over secured connections".
Many websites (including some important ones like online banking) don't set this bit for the cookie(s) used for session tracking. Hence, it is possible for an attacker to get the cookie with an invisible proxy that injects HTML which forces the browser to fetch something from the server which set up the cookie.
eg. I set up an invisible proxy on my wireless network which injects into every page and logs the cookie your browser sends when it attempts to connect to mail.google.com for the image.
I can now plug this cookie into Firefox and read your email.
Solution: if your website sets any cookies over an HTTPS connection, such cookies must set the bit meaning "Only send over secure connections". How one goes about doing this will depend on whether you're generating cookies yourself or using an existing framework.
1. Look at DNS requests or do a IP-domain reverse lookup to know what websites the target is visiting over HTTPS. Automated tool can do this over time.
2. On next regular HTTP request by your target, be a man-in-the-middle and inject an image pointing to desired HTTPS site, except don't use HTTPS - just HTTP.
3. Browser will dutifully send the cookie along with the image request over plain HTTP (after all, the domain names match), even though the cookie was created and managed only via HTTPS by the original website.
4. Now your automated sniffer just picked up the supposedly "secure" cookie for the HTTPS site, even though you never even attempted to hack the HTTPS conversation. If the site stores your username/password, a session id, etc this could expose sensitive information.
5. Protect your applications by setting the encrypted session only flag on the cookie so the browser won't send it with plain HTTP requests. If you have HTTP and HTTPS areas of the site, keep separate cookies for both areas and make sure sensitive info is only stored in the HTTPS-only cookie.
Natural != (nontoxic || beneficial)