Attacks/Breaches
11/1/2012
07:16 PM
50%
50%

Researchers Develop Cross-VM Side-Channel Attack

A new attack vector shows that isolation in public clouds is not a perfect answer for security, researcher says

A group of researchers has developed a side-channel attack targeting virtual machines that could pose a threat to cloud computing environments.

The attack is described in a paper entitled "Cross-VM Side Channels and Their Use to Extract Private Keys," authored by Yinqian Zhang, a PhD. student at the University of North Carolina at Chapel Hill; UNC professor Michael K. Reiter; Thomas Ristenpart, an assistant professor at University of Wisconsin-Madison; and Ari Juels, chief scientist at EMC's RSA security division.

According to the paper (PDF), the group was able to demonstrate an attack in a lab environment that allowed a malicious virtual machine (VM) to extract a private ElGamal decryption key from a co-resident virtual machine running Gnu Privacy Guard, which implements the OpenPGP email encryption standard.

"This attack is the first such attack demonstrated on a symmetric multiprocessing system virtualized using a modern VMM (Xen)," the paper states. "Such systems are very common today, ranging from desktops that use virtualization to sandbox application or OS compromises, to clouds that co-locate the workloads of mutually distrustful customers. Constructing such a side-channel requires overcoming challenges including core migration, numerous sources of channel noise, and the difficulty of preempting the victim with sufficient frequency to extract fine-grained information from it."

"The upshot is that isolation in public clouds is imperfect and can potentially be breached," Juels told Dark Reading. "So highly sensitive workloads should not be placed in a public cloud. Our attack is the first solid confirmation of a long hypothesized attack vector."

The underlying vulnerable code is in the most recent version of the libgcrypt library, according to the report.

"Specifically, we show that the attacker VM's monitoring of a victim's repeated exponentiations over the course of a few hours provides it enough information to reconstruct the victim's 457-bit private exponent accompanying a 4096-bit modulus with very high accuracy—so high that the attacker was then left to search fewer than 10, 000 possible exponents to find the right one," the researchers write.

The attack is fairly elaborate, Juels says. The attack environment is extremely noisy, making the attacker's job similar to reconstructing a conversation while listening through the wall with a stereo blaring on the other side, he explains. But then, the goal was ambitious: to extract a complete cryptographic key.

"To glean other secrets may be easier," he says. "I think it's unlikely that there will be a rash of private-key thefts, but attacks are always subject to improvement and automation. So the bottom line remains: Co-residency is not safe for highly sensitive workloads."

"A key point here is that the attacker doesn't need to compromise the VM she's using," he adds. "She can simply pay for and launch her own VMs in the cloud to mount the attack. In other words, she doesn't need to compromise any software. The harder part is getting the attack VM to sit on the same host as the victim."

Have a comment on this story? Please click "Add Your Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.

Comment  | 
Print  | 
More Insights
Register for Dark Reading Newsletters
White Papers
Cartoon
Current Issue
Dark Reading December Tech Digest
Experts weigh in on the pros and cons of end-user security training.
Flash Poll
Video
Slideshows
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2014-5426
Published: 2014-11-27
MatrikonOPC OPC Server for DNP3 1.2.3 and earlier allows remote attackers to cause a denial of service (unhandled exception and DNP3 process crash) via a crafted message.

CVE-2014-2037
Published: 2014-11-26
Openswan 2.6.40 allows remote attackers to cause a denial of service (NULL pointer dereference and IKE daemon restart) via IKEv2 packets that lack expected payloads. NOTE: this vulnerability exists because of an incomplete fix for CVE 2013-6466.

CVE-2014-6609
Published: 2014-11-26
The res_pjsip_pubsub module in Asterisk Open Source 12.x before 12.5.1 allows remote authenticated users to cause a denial of service (crash) via crafted headers in a SIP SUBSCRIBE request for an event package.

CVE-2014-6610
Published: 2014-11-26
Asterisk Open Source 11.x before 11.12.1 and 12.x before 12.5.1 and Certified Asterisk 11.6 before 11.6-cert6, when using the res_fax_spandsp module, allows remote authenticated users to cause a denial of service (crash) via an out of call message, which is not properly handled in the ReceiveFax dia...

CVE-2014-7141
Published: 2014-11-26
The pinger in Squid 3.x before 3.4.8 allows remote attackers to obtain sensitive information or cause a denial of service (out-of-bounds read and crash) via a crafted type in an (1) ICMP or (2) ICMP6 packet.

Best of the Web
Dark Reading Radio
Archived Dark Reading Radio
Now that the holiday season is about to begin both online and in stores, will this be yet another season of nonstop gifting to cybercriminals?