Bankrupt Covert Channel: Turning Network Predictability into Vulnerability

Authors: 

Dmitrii Ustiugov, Plamen Petrov, M. R. Siavash Katebzadeh, and Boris Grot, University of Edinburgh

Abstract: 

Recent years have seen a surge in the number of data leaks despite aggressive information-containment measures deployed by cloud providers. When attackers acquire sensitive data in a secure cloud environment, covert communication channels are a key tool to exfiltrate the data to the outside world. While the bulk of prior work focused on covert channels within a single CPU, they require the spy (transmitter) and the receiver to share the CPU, which might be difficult to achieve in a cloud environment with hundreds or thousands of machines.

This work presents Bankrupt, a high-rate highly clandestine channel that enables covert communication between the spy and the receiver running on different nodes in an RDMA network. In Bankrupt, the spy communicates with the receiver by issuing RDMA network packets to a private memory region allocated to it on a different machine (an intermediary). The receiver similarly allocates a separate memory region on the same intermediary, also accessed via RDMA. By steering RDMA packets to a specific set of remote memory addresses, the spy causes deep queuing at one memory bank, which is the finest addressable internal unit of main memory. This exposes a timing channel that the receiver can listen on by issuing probe packets to addresses mapped to the same bank but in its own private memory region. Bankrupt channel delivers 74Kb/s throughput in CloudLab's public cloud while remaining undetectable to the existing monitoring capabilities, such as CPU and NIC performance counters.

Open Access Media

USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.

BibTeX
@inproceedings {257186,
author = {Dmitrii Ustiugov and Plamen Petrov and M. R. Siavash Katebzadeh and Boris Grot},
title = {Bankrupt Covert Channel: Turning Network Predictability into Vulnerability},
booktitle = {14th {USENIX} Workshop on Offensive Technologies ({WOOT} 20)},
year = {2020},
url = {https://www.usenix.org/conference/woot20/presentation/ustiugov},
publisher = {{USENIX} Association},
month = aug,
}

Presentation Video