Google fixes Wallet flaw

News 15 Feb, 2012

Google has fixed one flaw but a brute force attack on rooted phones could still yield results for criminals.

Google said it has fixed a vulnerability in its Wallet service, after two flaws brought the security of the mobile payments offering into question.

Over the weekend, the tech giant had temporarily disabled provisioning of prepaid cards for Google Wallet as a precaution until a permanent fix was found.

We took this step as a precaution to ensure the security of our Wallet customers.

Google has now reopened the service, although it did not specify which vulnerability it had fixed.

“In addition, we issued a fix that prevents an existing prepaid card from being re-provisioned to another user,” said Osama Bedier, vice president of Google Wallet and Payments, in an updated blog post.

“While we’re not aware of any abuse of prepaid cards or the Wallet PIN resulting from these recent reports, we took this step as a precaution to ensure the security of our Wallet customers.”

One flaw meant that if a user was able to clear the data for Google Wallet in the phone's application settings, they could reset the PIN and spend the remainder of funds on the account.

There was no information from Google on whether it had done anything to prevent a brute force attack exposing PIN numbers on rooted devices.

When zvelo researcher Joshua Rubin took apart the code of the Wallet service, he found a long integer “salt” and a SHA256 hex encoded string “hash.” To get the PIN information all he had to do was run a simple brute force attack.

“zvelo feels that the fact that this attack requires root permissions does not in the least bit diminish the risk it imposes on users of Google Wallet,” Rubin said in a blog post earlier this week.

“Our reasoning is simple: presently, the PIN is easily revealed, but with the proper fix in place, the PIN will be nearly impossible to crack. It is as simple as that.”

Google advised customers not to root their phones.