TY - GEN
T1 - Blind in/on-path attacks and applications to VPNs
AU - Tolley, William J.
AU - Kujath, Beau
AU - Khan, Mohammad Taha
AU - Vallina-Rodriguez, Narseo
AU - Crandall, Jedidiah R.
N1 - Funding Information:
This material is based upon work supported by the U.S. National Science Foundation under Grant nos. 1518523, 1518878, 1801613, and 2007741, as well as the Open Technology Fund and the Ministry of Science and Innovation (Spain) (PID2019-111429RB-C22). We thank our shepherd, Zakir Du-rumeric; the anonymous reviewers of both the paper and the artifact; and Jeffrey Knockel and Philipp Winter for valuable feedback. We also thank the developers who provided important insights during the ethical disclosure process, especially Jason Donenfeld and the other members of the OSS Security mailing list. Many unnamed members of our research team lent us mobile phones for testing, and Lynn Pham donated an iPhone, for which we are grateful. Steve Gibson and Leo Laporte provided comic relief with their fascinating analysis of our initial ethical disclosure.
Publisher Copyright:
© 2021 by The USENIX Association. All rights reserved.
PY - 2021
Y1 - 2021
N2 - Protecting network protocols within an encrypted tunnel, using technologies such as Virtual Private Networks (VPNs), is increasingly important to millions of users needing solutions to evade censorship or protect their traffic against in/on-path observers/attackers. In this paper, we present a series of attacks from two threat models: an attacker that can inject spoofed packets into the network stack of a VPN client (called client-side), and an attacker that can spoof packets on the Internet and send them to a VPN server (called server-side). In both cases, we assume that the attacker is in/on-path, and can count encrypted bytes or packets over time. In both threat models, we demonstrate attacks to infer the existence of, interfere with, or inject data into TCP connections forwarded through the encrypted VPN tunnel. In the server-side threat model, we also demonstrate an attack to hijack tunneled DNS queries and completely remove the protections of the VPN tunnel. For the attacks presented in this paper, we (1) assess their feasibility in terms of packet rates and timing; (2) test their applicability against a broad range of VPN technologies, types, and vendors; and (3) consider practical issues with respect to real-world attacks. We followed an ethical disclosure process for all attacks presented in this paper. Client-side attacks were addressed with two CVEs and partially mitigated by a series of updates from some operating system and VPN client vendors. Server-side attacks have not been addressed and are still feasible with all operating systems and VPN servers that we tested.
AB - Protecting network protocols within an encrypted tunnel, using technologies such as Virtual Private Networks (VPNs), is increasingly important to millions of users needing solutions to evade censorship or protect their traffic against in/on-path observers/attackers. In this paper, we present a series of attacks from two threat models: an attacker that can inject spoofed packets into the network stack of a VPN client (called client-side), and an attacker that can spoof packets on the Internet and send them to a VPN server (called server-side). In both cases, we assume that the attacker is in/on-path, and can count encrypted bytes or packets over time. In both threat models, we demonstrate attacks to infer the existence of, interfere with, or inject data into TCP connections forwarded through the encrypted VPN tunnel. In the server-side threat model, we also demonstrate an attack to hijack tunneled DNS queries and completely remove the protections of the VPN tunnel. For the attacks presented in this paper, we (1) assess their feasibility in terms of packet rates and timing; (2) test their applicability against a broad range of VPN technologies, types, and vendors; and (3) consider practical issues with respect to real-world attacks. We followed an ethical disclosure process for all attacks presented in this paper. Client-side attacks were addressed with two CVEs and partially mitigated by a series of updates from some operating system and VPN client vendors. Server-side attacks have not been addressed and are still feasible with all operating systems and VPN servers that we tested.
UR - http://www.scopus.com/inward/record.url?scp=85114506900&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85114506900&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:85114506900
T3 - Proceedings of the 30th USENIX Security Symposium
SP - 3129
EP - 3146
BT - Proceedings of the 30th USENIX Security Symposium
PB - USENIX Association
T2 - 30th USENIX Security Symposium, USENIX Security 2021
Y2 - 11 August 2021 through 13 August 2021
ER -