Security researchers have discovered what they believe may be a government attempt to covertly wiretap an instant messaging service in Germany — an attempt that was blown because the potential intercepting authorities failed to reissue a TLS certificate.
The suspected man-in-the-middle attack was identified when the administrator of jabber.ru, the largest Russian XMPP service, received a notification that one of the servers’ certificates had expired.
However, jabber.ru found no expired certificates on the server — as explained in a blog post by ValdikSS, a pseudonymous anti-censorship researcher based in Russia who collaborated on the investigation.
The expired certificate was instead discovered on a single port being used by the service to establish an encrypted Transport Layer Security (TLS) connection with users. Before it had expired, it would have allowed someone to decrypt the traffic being exchanged over the service.
The wiretap is believed to have lasted for up to 6 months, from April 18 through to October 19, although the researchers were only able to confirm 90 days of actual interception. “All jabber.ru and xmpp.ru communications between these dates should be assumed compromised,” wrote ValdikSS.
“Given the nature of the interception, the attacker have been able to execute any action as if it is executed from the authorized account, without knowing the account password. This means that the attacker could download account's roster, lifetime unencrypted server-side message history, send new messages or alter them in real time,” they added.
The researchers said they do not believe that the servers were hacked by criminals, but were reconfigured to facilitate the wiretapping as a result of a government request. “We believe this is lawful interception Hetzner and Linode were forced to setup,” ValdikSS wrote, referencing the hosting providers in Germany.