Friday, January 21, 2022

Network Segmentation of Users on Multi-User Servers and Networks

Early last year, I finished a paper for the Master of Science in Information Security Engineering program at SANS Technology Institute. The paper was published at and a year ago but I am just now writing about the project here since life was pretty busy at the time.

I spent several years thinking through this problem and trying different technologies to make it work. I spent a few months finalizing it then writing it up for the academic paper (during which time I also had to, um... think about... this totally hypothetical disaster for several months...).

Rather than rewriting my paper as a blog post, I will include some of the most important parts of the paper, add some additional commentary, then refer you to the paper as needed. If you are actually interested in this solution, please read the paper since it has many more details.

Problem: Potential attack vector

As seen in real life on an HPC login node:

tcp  0  0*   LISTEN   23689/Xorg​
tcp  0  0*   LISTEN   123965/mpiexec​
tcp  0  0*   LISTEN   107345/Xorg​
tcp  0  0*   LISTEN   213053/node ​
tcp  0  0*   LISTEN   212528/mongod ​
tcp  0  0*   LISTEN   212606/python ​
tcp  0  0*   LISTEN   212788/python ​
tcp  0  0*   LISTEN   212879/python​
tcp  0  0*  LISTEN   60839/java ​
tcp  0  0*   LISTEN   60839/java​
tcp  0  0*   LISTEN   60839/java​
tcp  0  0*   LISTEN   6473/mpiexec​
tcp  0  0*   LISTEN   219999/mpiexec​
tcp  0  0*   LISTEN   175150/mpiexec​
tcp  0  0*   LISTEN   199971/mpiexec​
tcp  0  0*   LISTEN   123965/mpiexec​
tcp  0  0*   LISTEN   264169/mpiexec​

These processes were all owned by various HPC users and there were probably dozens of people logged into that system at that moment.

I'll be lazy and quote from the paper's abstract:

In High Performance Computing (HPC) environments, hundreds of users can be logged in and running batch jobs simultaneously on clusters of servers in a multi-user environment. Security controls may be in place for much of the overall HPC environment, but user network communication is rarely included in those controls. Some users run software that must listen on arbitrary network ports, exposing user software to attacks by others. This creates the possibility of account compromise by fellow users who have access to those same servers and networks. A solution was developed to transparently segregate users from each other both locally and over the network. The result is easy to install and administer.