In the past few days, developers on the XDA-Developers forum have discovered a new root exploit for recent Samsung phones. Normally a root exploit is a good thing for advanced users; they can modify their OS to improve performance, install new and rare apps, or even patch bugs. On the other hand, novice and uninformed users can have their phones targeted by attackers looking to reduce security and steal money or personal data. Malware writers have previously taken exploits written by the legitimate rooting community and repackaged them along with their malware to gain absolute control of a victim’s device.
XDA-Developers member alephzain discovered the vulnerability and created an exploit. A second forum member, Chainfire, packaged the exploit into an app that installed the exploit and rooted vulnerable phones. The app was later modified to disable the vulnerability to prevent an attacker from entering your phone.
Chainfire’s app makes rooting a Samsung phone easier for users.
How the exploit works
The vulnerability involves how the Exynos processor is used on certain Samsung phones (for example, the Galaxy S2). It is possible to access the entirety of physical memory through the OS. Usually this is limited to the root user, but in this case that memory is accessible by any user program.
The exploit uses this physical memory access to patch a system function in memory, bypassing the security and user controls in place. This lets the exploit gain root access on the phone. Once an attacker has root access, the entire phone is open.
Already exploited? Not maliciously
With such an open vulnerability in the wild, one might think that malware authors would be rushing to weaponize the exploit. Fortunately only Chainfire has done so, with this mobile rooting app. Currently knowledgeable phone “modders” can download and install this app to root their phones. And so can attackers, intent on stealing your personal data or money.
To protect against the latter situation, we detect the most recent versions of Chainfire’s tool as Android/ExynosToor.A-B, and alephzain’s exploit as Exploit/ExymemBrk.A.
Visa is testing out its PayWave contactless payment service at the Summer Olympics in London. Every athlete will get a Samsung Galaxy SIII phone enabled with near-field communication (NFC) along with Visa’s payment app. Contactless payments aren’t new, and similar payments by mobile phone have been tested by Google with its Wallet app and other NFC smartphones.
A Samsung Galaxy SIII will be given to every athlete competing at the 2012 Summer Olympics in London.
When we last looked at NFC phones and similar apps, there were questions of whether an attacker could go after the apps or the phone hardware and the Android OS. Since then we have seen a PIN-reset vulnerability that allowed an attacker to use the free prepaid card and the ability to crack PINs on the phone. Google updated the Wallet app to fix those vulnerabilities and make attacks much harder. Now attackers would need to go after the hardware itself, though this does not necessarily involve going after the Secure Element portion. One can get excellent results by targeting the OS and its NFC-handling libraries.
Fuzzing the hardware, which involves feeding corrupt or damaged data to an app to discover vulnerabilities, is a good first step. Researchers Charlie Miller and Collin Mulliner fuzzed SMS messages to great effect to discover exploitable vulnerabilities on Android and iOS phones a few years back. Mulliner has also looked at fuzzing NFC tags, going as far as developing a Python library and framework for testing older devices. Recently he updated his software to measure Android devices, allowing him to inject crafted NFC tags to a phone and then monitor the results. He can programmatically feed crafted or damaged NFC tags to Android’s library and then capture any crashes or code-execution opportunities.
Collin Mulliner’s NFC library can be used in fuzzing Android phones. This is very useful for discovering new vulnerabilities.
The Samsung Galaxy SIII goes on sale in North America and wordlwide within the first two weeks of July. An attacker wishing to target the device can purchase one easily and use Mulliner’s research to help find vulnerabilities and eventually develop exploits to steal a victim’s credit card. The large number of readers at the Olympics will provide places where a successful attacker can use stolen credentials to make purchases. The Olympics will also provide a concentrated pool of targets (people and phones) to pilfer from–especially if everyone is busy watching who wins the medals and not worrying about where his or her phone is.