Pierluigi Paganini July 09, 2012

Last week, on blog.torproject.org was published the news relative to a security vulnerability found in Cyberoam DPI devices (CVE-2012-3372). All is started when a user in Jordan reported seeing a fake certificate to torproject.org.

The certificate was issued by Cyberoam companies and the researchers of the Tor project believed that the CA has been tricked  such as famous predecessors Comodo, Diginotar. The user not reported problems during its ordinary navigation, he was able to browse web site such as Twitter, Facebook and Gmail, this scenario suggests we are facing with a targeted attack to trick Cyberoam to issue fake certificate for torproject.org website.

Who is Cyberoam and  which are its products?

Cyberoam UTM is a network security solution appliance vendor. But the company also provides a range of devices used for Deep Packet Inspection (DPI), probably the user’s connection was intercepted by one of their devices.

During the investigation the experts of torproject.org found a vulnerability in Cyberoam DPI devices, they discovered that all Cyberoam DPI devices share the same digital certificate.

This means that the private key is the same for every device, the implications, if confirmed, are serious, in fact it could be possible to intercept traffic from any victim of a Cyberoam device extracting the key from the device and import it into other DPI devices to use for the interception or simply using another Cyberoam DPI.

The torproject.org researchers have immediately tried to contact the Cyberoam firm and they have also notified the vulnerability to browser vendors asking them to blacklist the Cyberoam CA certificate in their browsers.

Waiting for the reply of the security firm the experts of torproject.org have published in their blog the following info.

“The Cyberoam CA certificate is not trusted, and so browsers will show users a warning (unless someone has already installed the certificate). Users with the Tor Browser Bundle are not affected.”

Cyberoam has responded that its security devices open up traffic to inspection by third-parties, it also added in an official communicate that the devices implements tamper-protection measures meant it was not possible to export cryptographic keys from them.

“Cyberoam’s private keys cannot be extracted even upon dissecting the box or cloning its hardware and software. This annuls any possibility of tampering with the existing certificates on appliance,” the firm explained.

Obviously Cyberoam reiterated the purpose of the https deep scan inspection technology, it has been developed to network protection from malware detection and not to attack tool such as Tor.

Although devices are bundled with technology designed to perform deep HTTPS scanning usable to peer into the contents of encrypted communications.

They completely excluded to have been involved in any king of attacks against Tor project.

Again the company clarified:

“Cyberoam UTM [Unified Threat Management] either accepts or rejects, but does not store HTTPS Deep Scan Inspection data, as processing is done in real-time. The possibility of data interception between any two Cyberoam appliances is hence nullified,”

How does it work traffic inspection for similar devices?

UTM security appliances perform SSL inspection by generating their own certificates in this way network administrators would install them from Cyberoam on every devices of their network, allowing the traffic inspection technology to work without generating a warning.

The company remarked that HTTPS Deep Scan Inspection is driven by SSL Bridging Technology, so Cyberoam appliance provides self-signed certificate to the client whilst establishing a secure connection with the client and server. A default certificate is shipped which remains the same across all the appliances.

How to prevent traffic analysis?

It could simply possible uninstall the Cyberoam CA certificate from the browser and decline to complete any connection which gives a certificate warning.

Which is the main risk in this case?

Criminals or governments could use the stolen certificates to conduct “man-in-the-middle” attacks, tricking users into thinking they were at a legitimate site when in fact their communications were being secretly tampered and intercepted. That is for example what occurred in the DigiNotar case … companies like Facebook, Google and also agencies like CIA, MI6 were targeted in Dutch government certificate hack.

Pierluigi Paganini