Telegram is supposedly a secure messaging application, but it forces clients to only use P2P connection while initiating a call, however this setting can also be changed from “Settings > Privacy and security > Calls > peer-to-peer” to other available options.
The tdesktop and telegram for windows breaks this trust by leaking public/private IP address of end user and there was no such option available yet for setting “P2P > nobody” in tdesktop and telegram for windows.
PS: Even telegram for Android will also leak your IP address if you have not set “Settings > Privacy and security > Calls > peer-to-peer >nobody” (But Peer-to-Peer settings for call option already exists in Telegram for android).
To view this in action in tdesktop:
1. Open tdesktop,
2. Initiate a call to anyone,
3. You will notice the end user IP address is leaking.
1. Open tdesktop in Ubuntu and login with user A
2. Open telegram in windows phone login with user B
3. Let user B initiate the call to user A
4. While user A access log will have public/private IP address of user B.
Not only the MTProto Mobile Protocol fails here in covering the IP address, rather such information can also be used for OSINT. This issue was fixed in 1.3.17 beta and v1.4.0 which have an option of setting your “P2P to Nobody/My contacts”, Later CVE-2018-17780 was assign to this vulnerability.
Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer.
Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US.
Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines.
Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.