The security of the global Default Free Zone DFZ) has been a topic of much debate and concern for the last twenty years (or more). Two recent papers have brought this issue to the surface once again—it is worth looking at what these two papers add to the mix of what is known, and what solutions might be available. The first of these—
Demchak, Chris, and Yuval Shavitt. 2018. “China’s Maxim – Leave No Access Point Unexploited: The Hidden Story of China Telecom’s BGP Hijacking.” Military Cyber Affairs 3 (1). https://doi.org/10.5038/2378-07184.108.40.2060.
—traces the impact of Chinese “state actor” effects on BGP routing in recent years.
Whether these are actual attacks, or mistakes from human error for various reasons generally cannot be known, but the potential, at least, for serious damage to companies and institutions relying on the DFZ is hard to overestimate. This paper lays out the basic problem, and the works through a number of BGP hijacks in recent years, showing how they misdirected traffic in ways that could have facilitated attacks, whether by mistake or intentionally. For instance, quoting from the paper—
- Starting from February 2016 and for about 6 months, routes from Canada to Korean government sites were hijacked by China Telecom and routed through China.
- On October 2016, traffic from several locations in the USA to a large Anglo-American bank
- headquarters in Milan, Italy was hijacked by China Telecom to China.
- Traffic from Sweden and Norway to the Japanese network of a large American news organization was hijacked to China for about 6 weeks in April/May 2017.
What impact could such a traffic redirection have? If you can control the path of traffic while a TLS or SSL session is being set up, you can place your server in the middle as an observer. This can, in many situations, be avoided if DNSSEC is deployed to ensure the certificates used in setting up the TLS session is valid, but DNSSEC is not widely deployed, either. Another option is to simply gather encrypted traffic and either attempt to break the key, or use data analytics to understand what the flow is doing (a side channel attack).
What can be done about these kinds of problems? The “simplest”—and most naïve—answer is “let’s just secure BGP.” There are many, many problems with this solution. Some of them are highlighted in the second paper under review—
Bonaventure, Olivier. n.d. “A Survey among Network Operators on BGP Prefix Hijacking – Computer Communication Review.” Accessed November 3, 2018. https://ccronline.sigcomm.org/2018/ccr-january-2018/a-survey-among-network-operators-on-bgp-prefix-hijacking/.
—which illustrates the objections providers have to the many forms of BGP security that have been proposed to this point. The first is, of course, that it is expensive. The ROI of the systems proposed thus far are very low; the cost is high, and the benefit to the individual provider is rather low. There is both a race to perfection problem here, as well as a tragedy of the commons problem. The race to perfection problem is this: we will not design, nor push for the deployment of, any system which does not “solve the problem entirely.” This has been the mantra behind BGPSEC, for instance. But not only is BGPSEC expensive—I would say to the point of being impossible to deploy—it is also not perfect.
The second problem in the ROI space is the tragedy of the commons. I cannot do much to prevent other people from misusing my routes. All I can really do is stop myself and my neighbors from misusing other people’s routes. What incentive do I have to try to make the routing in my neighborhood better? The hope that everyone else will do the same. Thus, the only way to maintain the commons of the DFZ is for everyone to work together for the common good. This is difficult. Worse than herding cats.
A second point—not well understood in the security world—is this: a core point of DFZ routing is that when you hand your reachability information to someone else, you lose control over that reachability information. There have been a number of proposals to “solve” this problem, but it is a basic fact that if you cannot control the path traffic takes through your network, then you have no control over the profitability of your network. This tension can be seen in the results of the survey above. People want security, but they do not want to release the information needed to make security happen. Both realities are perfectly rational!
Part of the problem with the “more strict,” and hence (considered) “more perfect” security mechanisms proposed is simply this: they are not quiet enough. They expose far too much information. Even systems designed to prevent information leakage ultimately leak too much.
So… what do real solutions on the ground look like?
One option is for everyone to encrypt all traffic, all the time. This is a point of debate, however, as it also damages the ability of providers to optimize their networks. One point where the plumbing allegory for networking breaks down is this: all bits of water are the same. Not all bits on the wire are the same.
Another option is to rely less on the DFZ. We already seem to be heading in this direction, if Geoff Huston and other researchers are right. Is this a good thing, or a bad one? It is hard to tell from this angle, but a lot of people think it is a bad thing.
Perhaps we should revisit some of the proposed BGP security solutions, reshaping some of them into something that is more realistic and deployable? Perhaps—but the community is going to let go of the “but it’s not perfect” line of thinking, and start developing some practical, deployable solutions that don’t leak so much information.
Finally, there is a solution Leslie Daigle and I have been tilting at for a couple of years now. Finding a way to build a set of open source tools that will allow any operator or provider to quickly and cheaply build an internal system to check the routing information available in their neighborhood on the ‘net, and mix local policy with that information to do some bare bones work to make their neighborhood a little cleaner. This is a lot harder than “just build some software” for various reasons; the work is often difficult—as Leslie says, it is largely a matter of herding cats, rather than inventing new things.