Signal Hacks Cellebrite Phone Hacking Kit

Secure messaging service Signal has turned the tables on security specialist Cellebrite and claimed it has hacked its own hacking equipment and software.

Signal said in a blog post that it found and exploited a number of vulnerabilities with Cellebrite’s UFED software, which is used by law enforcement to break into Android or iOS phones and allegedly extract secure messages.

Signal’s creator Moxie Marlinspike claimed that his team obtained Cellebrite’s hacking kit and discovered several vulnerabilities. He then implied that Signal will update the app to stymie any law enforcement attempts to hack it.

Sweet revenge?

The move will be sweet revenge for Marlinspike and Signal.

This is because in December last year, Cellebrite astonished the security industry when it claimed it had cracked the encryption of Signal, one of the most secure messaging apps on the market.

Cellebrite’s claim was quickly dismissed by Moxie Marlinspike, after it emerged that the exploit seemed to work via an unlocked Android phone.

Matters were not helped when Cellebrite significantly altered its original blog on the hacking claim, leading to question marks over the reliability of its original claim.

In the blog post, Marlinspike explained that his team had managed to obtain a Cellebrite UFED, complete with the software and hardware dongle.

He joked that it fell off a truck while he was out for a walk.

“Cellebrite makes software to automate physically extracting and indexing data from mobile devices,” Marlinspike wrote. “Their customer list has included authoritarian regimes in Belarus, Russia, Venezuela, and China; death squads in Bangladesh; military juntas in Myanmar; and those seeking to abuse and oppress in Turkey, UAE, and elsewhere. A few months ago, they announced that they added Signal support to their software.”

“Their products have often been linked to the persecution of imprisoned journalists and activists around the world, but less has been written about what their software actually does or how it works,” Marlinspike wrote. “Let’s take a closer look.”

Hacking Cellebrite

Marlinspike pointed out that Cellebrite produces two primary pieces of software (both for Windows): UFED and Physical Analyzer.

UFED apparently creates a backup of a device onto the Windows machine running UFED (it is essentially a front-end to ‘adb backup’ on Android and iTunes backup on iPhone, he explained.

Once a backup has been created, Physical Analyzer then parses the files from the backup in order to display the data in browsable form.

“When Cellebrite announced that they added Signal support to their software, all it really meant was that they had added support to Physical Analyzer for the file formats used by Signal,” Marlinspike wrote. “This enables Physical Analyzer to display the Signal data that was extracted from an unlocked device in the Cellebrite user’s physical possession.”

“One way to think about Cellebrite’s products is that if someone is physically holding your unlocked device in their hands, they could open whatever apps they would like and take screenshots of everything in them to save and go over later,” he wrote. “Cellebrite essentially automates that process for someone holding your device in their hands.”

Exploited

“By a truly unbelievable coincidence, I was recently out for a walk when I saw a small package fall off a truck ahead of me,” Marlinspike wrote. “As I got closer, the dull enterprise typeface slowly came into focus: Cellebrite.”

“Inside, we found the latest versions of the Cellebrite software, a hardware dongle designed to prevent piracy (tells you something about their customers I guess!), and a bizarrely large number of cable adapters,” he wrote.

“Looking at both UFED and Physical Analyzer, though, we were surprised to find that very little care seems to have been given to Cellebrite’s own software security,” he wrote. “Industry-standard exploit mitigation defenses are missing, and many opportunities for exploitation are present.”

Marlinspike noted that Cellebrite used some old and out-of-date DLLs, including a 2012 version of FFmpeg and MSI Windows installer packages for Apple’s iTunes program.

Signal’s team found that by including “specially formatted but otherwise innocuous files in any app on a device” scanned by Cellebrite, it could run code that modifies the UFED report.

For instance, it could potentially insert or remove text, email, photos, contacts and other data while leaving no trace of the tampering.

In a tweet, Signal demonstrated in a video the hack in action, with the UFED parsing a file formatted to run code and display a benign message.

Tom Jowitt

Tom Jowitt is a leading British tech freelancer and long standing contributor to Silicon UK. He is also a bit of a Lord of the Rings nut...

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