Slashdot Mirror
Poor SSL Implementations Leave Many Android Apps Vulnerable
Trailrunner7 writes "There are thousands of apps in the Google Play mobile market that contain serious mistakes in the way that SSL/TLS is implemented, leaving them vulnerable to man-in-the-middle attacks that could compromise sensitive user data such as banking credentials, credit card numbers and other information. Researchers from a pair of German universities conducted a detailed analysis of thousands of Android apps and found that better than 15 percent of those apps had weak or bad SSL implementations. The researchers conducted a detailed study of 13,500 of the more popular free apps on Google Play, the official Android app store, looking at the SSL/TLS implementations in them and trying to determine how complete and effective those implementations are. What they found is that more than 1,000 of the apps have serious problems with their SSL implementations that make them vulnerable to MITM attacks, a common technique used by attackers to intercept wireless data traffic. In its research, the team was able to intercept sensitive user data from these apps, including credit card numbers, bank account information, PayPal credentials and social network credentials."
Researchers from a pair of German universities conducted a detailed analysis of thousands of Android apps and found that better than 15 percent of those apps had weak or bad SSL implementations.
I would have thought that an SSL implementation, complete with certificate chain validation would be provided by the OS, and that apps would use that. Only apps that had special requirements should have to implement SSL. Does anyone know if android does provide a TLS interface, and if so are the apps ignoring the platform service?
I myself have implemented them for shopping apps (SSL for anything dealing with user details, payment, etc.). When you're communicating with an external service that requires (or where you want to use) encrypted connections and that service only offers SSL (this is probably 90% of the time) you need to use it. Now the catch here is that the standard SSL handlers available to you in Android provide an "ideal" setup, where servers and certs are exactly as they "should" be. The problem is unless you are paying rediculous ammounts for dedicated SSL services and high quality certs your setup will not be the "ideal", and you'll have to make exceptions by overriding code.
As an example, in the shopping system I set up there were two sets of certs, one set was signed [payment gateway] the other wasn't [user control pannel]. I had to jump through a few hoops, and the app would be open for man-in-the-middle if set up right - but luckilly all they'd get would be user login details, address and phone number - billing is all external and requires a separate authorization.
This is not a platform problem, this is a matter of the choices made by application developers. I can guarantee this same sort of analysis would fail a similar number of apps across the board for Windows, OSX, or *any* platform with a sufficient number of applications making use of SSL sockets. I know the sort of developers that do this and they'll do it *everywhere*, because of some mix of not quite understanding the point of the CA and the hassle they perceive in trying to find a way to do it right (admittedly, the logistics of doing it right in certain scenarios is daunting and necessarily puts work on the enduser if you want to be truly secure).
I have now read the article and it is apps misuse the APIS. They search for apps that either don't use the TLS APIs but have ssl addresses encoded, or which use a non-default trust manager. When you establish an SSL connection via the normal Java APIs the default trust manager does check the validity of the certificates (i.e. that tey are signed by a trusted CA) and that the URL requested matches the hostname in the certificate's subject DN. There can be valid reasons for overriding this, including using your own specific certificate rather than any signed by a CA, or for development to allow self-signed certificates - though this should be put in production.
They found that a lot of apps had overridden the rust manager in a dangerous way, allowing self-signed certificates in production or allowing any certificate even if id didn't match the host.
Though this is a problem it is not an "android issue". You can write apps that use self-signed certificates, bypass host checking etc. on Windows and any platform that allows you to customise certificate trust checking.
The problem does not always lie in the certificate. It also lies in the fact that the SSL clients built into Windows NT 5.1 (XP) Android 2.3 (Gingerbread) does not support Server Name Indication (SNI), which allows multiple certificates on one IP address. This lack of support for SNI was not corrected until Windows NT 6 (Vista) on PCs, Android 3.0 (Honeycomb) on tablets, or Android 4.0 (ICS) on phones and pocket tablets. Without SNI and without DNSSEC, each site using SSL needs its own IP address.