99% of Android Devices Harbor Authentication Flaw on Open WiFi Networks

German researchers uncovered a flaw with the way applications authenticate with Google services that could allow a man-in-the-middle attack to intercept tokens and impersonate the user.

Most devices running Google's Android operating system are vulnerable to a man-in-the-middle attack that would allow adversaries to access victims' personal data stored in Google services, warned a group of university researchers.

Malicious individuals can intercept authentication tokens from Android users running applications over an unsecured WiFi network, said researchers from Germany's University of Ulm on May 13. Applications that access Google services, such as Calendar and Contacts, use ClientLogin authentication protocol requests and receive an authentication token to gain access to user data. Google designed the token so that the same instance can be reused to access that service for two weeks.

However, if the token is requested and sent while the user was on an unencrypted insecure connection, anyone eavesdropping could find and steal the token and use it for the 14-day period to access user contacts, calendar items, email and other personal information. The tokens aren't bound to a session or a device, making it very easy for the attacker to impersonate the user with a different handset, according to researchers Bastian Konings, Jens Nickels and Florian Schaub.

"We wanted to know if it is really possible to launch an impersonation attack against Google services and started our own analysis," the researchers in the university's Institute of Media Informatics wrote. "The short answer is: Yes, it is possible and it is quite easy to do so."

The problem exists in Android 2.3.3 and earlier, which includes 99.7 percent of current Android devices, according to Google's platform statistics. The hole has been addressed in 2.3.4, and all the applications use the secure HTTPS connection to access Google services, according to the researchers.

The ClientLogin authentication protocol vulnerability is an example of attackers exploiting WiFi networks and spying on enterprise and personal data, Dan Hoffman, chief mobile evangelist at Juniper Networks Global Threat Center, told eWEEK. The "ease of this exploitation" makes this a serious vulnerability for anyone with sensitive data stored in Google services, Hoffman said.

"An adversary can gain full access to the calendar, contacts information or private Web albums of the respective Google user," according to the researchers.

The adversary can view, modify or delete any contacts, calendar events or private pictures as if the legitimate user had properly logged in, Hoffman said. The person would be able to obtain and manipulate all items owned by the user "clandestinely" over an extended period of time, according to Hoffman.

A malicious hacker could harvest a large number of tokens by merely setting up a WiFi access point and pretending to be an unencrypted wireless network. Any Android device within range could connect, giving the hacker access to the service tokens.

Enterprises should make sure employees are using VPN software to access the corporate data or email over open WiFi networks, said Hoffman. Wireless settings should be properly configured and application developers should make sure they are using proper security protocols to protect data, according to Hoffman.

Researchers tested applications that contact Google services on various versions of Android and found that the problem existed in all versions before 2.3.3. On Android 2.3.4 and later, only the Gallery application, which synchronizes Picasa with online Web albums, remained vulnerable as it uses regular HTTP for synchronization. Any Android or desktop application that accesses Google services using the ClientLogin protocol over HTTP is vulnerable, the researchers found.

Researchers suggested Google shorten the length of time the tokens are valid and automatically reject ClientLogin requests from insecure HTTP connections.

Android users should update to version 2.3.4 although that is easier said than done since most users have to wait for the wireless carriers to roll out the update. Many Verizon Wireless customers are still stuck at version 2.2.2, for example. Users willing to jailbreak can go ahead with the update. Either way, users should disable the setting that allows the Android device to automatically synchronize with open WiFi networks.

Even though the chances of a regular user coming under this kind of attack "is not high," users should be "paranoid" and avoid open WiFi networks, according to Paul Laudanski, director of the Cyber Threat Analysis Center at ESET. "Be mindful of where you are and what your systems connect into," Laudanski said.