The Hedge 82: Jared Smith and Route Poisoning

Intentionally poisoning BGP routes in the Default-Free Zone (DFZ) would always be a bad thing, right? Actually, this is a fairly common method to steer traffic flows away from and through specific autonomous systems. How does this work, how common is it, and who does this? Jared Smith joins us on this episode of the Hedge to discuss the technique, and his research into how frequently it is used.

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The Hedge 66: Tyler McDaniel and BGP Peer Locking

Tyler McDaniel joins Eyvonne, Tom, and Russ to discuss a study on BGP peerlocking, which is designed to prevent route leaks in the global Internet. From the study abstract:

BGP route leaks frequently precipitate serious disruptions to interdomain routing. These incidents have plagued the Internet for decades while deployment and usability issues cripple efforts to mitigate the problem. Peerlock, introduced in 2016, addresses route leaks with a new approach. Peerlock enables filtering agreements between transit providers to protect their own networks without the need for broad cooperation or a trust infrastructure.

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Current Work in BGP Security

I’ve been chasing BGP security since before the publication of the soBGP drafts, way back in the early 2000’s (that’s almost 20 years for those who are math challenged). The most recent news largely centers on the RPKI, which is used to ensure the AS originating an advertisements is authorized to do so (or rather “owns” the resource or prefix). If you are not “up” on what the RPKI does, or how it works, you might find this old blog post useful—its actually the tenth post in a ten post series on the topic of BGP security.

Recent news in this space largely centers around the ongoing deployment of the RPKI. According to Wired, Google and Facebook have both recently adopted MANRS, and are adopting RPKI. While it might not seem like autonomous systems along the edge adopting BGP security best practices and the RPKI system can make much of a difference, but the “heavy hitters” among the content providers can play a pivotal role here by refusing to accept routes that appear to be hijacked. This not only helps these providers and their customers directly—a point the Wired article makes—this also helps the ‘net in a larger way by blocking attackers access to at least some of the “big fish” in terms of traffic.

Leslie Daigle, over at the Global Cyber Alliance—an organization I’d never heard of until I saw this—has a post up explaining exactly how deploying the RPKI in an edge AS can make a big difference in the service level from a customer’s perspective. Leslie is looking for operators who will fill out a survey on the routing security measures they deploy. If you operate a network that has any sort of BGP presence in the default-free zone (DFZ), it’s worth taking a look and filling the survey out.

One of the various problems with routing security is just being able to see what’s in the RPKI. If you have a problem with your route in the global table, you can always go look at a route view server or looking glass (a topic I will cover in some detail in an upcoming live webinar over on Safari Books Online—I think it’s scheduled for February right now). But what about the RPKI? RIPE NCC has released a new tool called the JDR:

Just like RP software, JDR interprets certificates and signed objects in the RPKI, but instead of producing a set of Verified ROA Payloads (VRPs) to be fed to a router, it annotates everything that could somehow cause trouble. It will go out of its way to try to decode and parse objects: even if a file is clearly violating the standards and should be rejected by RP software, JDR will try to process it and present as much troubleshooting information to the end-user afterwards.

You can find the JDR here.

Finally, the folks at APNIC, working with NLnet Labs, have taken a page from the BGP playbook and proposed an opaque object for the RPKI, extending it beyond “just prefixes.” They’ve created a new Resource Tagged Attestations, or RTAs, which can carry “any arbitrary file.” They have a post up explaining the rational and work here.

Reducing RPKI Single Point of Takedown Risk

The RPKI, for those who do not know, ties the origin AS to a prefix using a certificate (the Route Origin Authorization, or ROA) signed by a third party. The third party, in this case, is validating that the AS in the ROA is authorized to advertise the destination prefix in the ROA—if ROA’s were self-signed, the security would be no better than simply advertising the prefix in BGP. Who should be able to sign these ROAs? The assigning authority makes the most sense—the Regional Internet Registries (RIRs), since they (should) know which company owns which set of AS numbers and prefixes.

The general idea makes sense—you should not accept routes from “just anyone,” as they might be advertising the route for any number of reasons. An operator could advertise routes to source spam or phishing emails, or some government agency might advertise a route to redirect traffic, or block access to some web site. But … if you haven’t found the tradeoffs, you haven’t looked hard enough. Security, in particular, is replete with tradeoffs.

Every time you deploy some new security mechanism, you create some new attack surface—sometimes more than one. Deploy a stateful packet filter to protect a server, and the device itself becomes a target of attack, including buffer overflows, phishing attacks to gain access to the device as a launch-point into the private network, and the holes you have to punch in the filters to allow services to work. What about the RPKI?

When the RKI was first proposed, one of my various concerns was the creation of new attack services. One specific attack surface is the control a single organization—the issuing RIR—has over the very existence of the operator. Suppose you start a new content provider. To get the new service up and running, you sign a contract with an RIR for some address space, sign a contract with some upstream provider (or providers), set up your servers and service, and start advertising routes. For whatever reason, your service goes viral, netting millions of users in a short span of time.

Now assume the RIR receives a complaint against your service for whatever reason—the reason for the complaint is not important. This places the RIR in the position of a prosecutor, defense attorney, and judge—the RIR must somehow figure out whether or not the charges are true, figure out whether or not taking action on the charges is warranted, and then take the action they’ve settled on.

In the case of a government agency (or a large criminal organization) making the complaint, there is probably going to be little the RIR can do other than simply revoke your certificate, pulling your service off-line.

Overnight your business is gone. You can drag the case through the court system, of course, but this can take years. In the meantime, you are losing users, other services are imitating what you built, and you have no money to pay the legal fees.

A true story—without the names. I once knew a man who worked for a satellite provider, let’s call them SATA. Now, SATA’s leadership decided they had no expertise in accounts receivables, and they were spending too much time on trying to collect overdue bills, so they outsourced the process. SATB, a competing service, decided to buy the firm SATA outsourced their accounts receivables to. You can imagine what happens next… The accounting firm worked as hard as it could to reduce the revenue SATA was receiving.

Of course, SATA sued the accounting firm, but before the case could make it to court, SATA ran out of money, laid off all their people, and shut their service down. SATA essentially went out of business. They won some money later, in court, but … whatever money they won was just given to the investors of various kinds to make up for losses. The business itself was gone, permanently.

Herein lies the danger of giving a single entity like an RIR, even if they are friendly, honest, etc., control over a critical resource.

A recent paper presented at the ANRW at APNIC caught my attention as a potential way to solve this problem. The idea is simple—just allow (or even require) multiple signatures on a ROA. To be more accurate, each authorizing party issues a “partial certificate;” if “enough” pieces of the certificate are found and valid, the route will be validated.

The question is—how many signatures (or parts of the signature, or partial attestations) should be enough? The authors of the paper suggest there should be a “Threshold Signature Module” that makes this decision. The attestations of the various signers are combined in the threshold module to produce a single signature that is then used to validate the route. This way the validation process on the router remains the same, which means the only real change in the overall RPKI system is the addition of the threshold module.

If one RIR—even the one that allocated the addresses you are using—revokes their attestation on your ROA, the remaining attestations should be enough to convince anyone receiving your route that it is still valid. Since there are five regions, you have at least five different choices to countersign your ROA. Each RIR is under the control of a different national government; hence organizations like governments (or criminals!) would need to work across multiple RIRs and through other government organizations to have a ROA completely revoked.

An alternate solutions here, one that follows the PGP model, might be to simply have the threshold signature model consider the number and source of ROAs using the existing model. Local policy could determine how to weight attestations from different RIRs, etc.

This multiple or “shared” attestation (or signature) idea seems like a neat way to work around one of (possibly the major) attack surfaces introduced by the RPKI system. If you are interested in Internet core routing security, you should take a read through the post linked above, and then watch the video.

The Hedge 43: Ivan Pepelnjak and Trusting Routing Protocols

Can you really trust what a routing protocol tells you about how to reach a given destination? Ivan Pepelnjak joins Nick Russo and Russ White to provide a longer version of the tempting one-word answer: no! Join us as we discuss a wide range of issues including third-party next-hops, BGP communities, and the RPKI.

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The Hedge 42: Andrei Robachevsky and MANRS

The security of the global routing table is foundational to the security of the overall Internet as an ecosystem—if routing cannot be trusted, then everything that relies on routing is suspect, as well. Mutually Agreed Norms for Routing Security (MANRS) is a project of the Internet Society designed to draw network operators of all kinds into thinking about, and doing something about, the security of the global routing table by using common-sense filtering and observation. Andrei Robachevsky joins Russ White and Tom Ammon to talk about MANRS.

More information about MANRS can be found on the project web site, including how to join and how to support global routing security.

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