That's totally reasonable, and I agree that using something hosted entirely by a 3rd party makes sense for some use cases. Our reason goes a bit beyond security concerns, in this case. We built Nebula for large scale deployments, and because of that, we have made decisions that lean into that model for hosting.
Our decision to leave lighthouse hosting in the hands of users has one primary rationale: We want users to have complete control their network availability. Any downtime of our service should not impact their network availability. You can even host some of your lighthouses inside of network boundaries to ensure that an internal network functions properly if its connection to the internet is interrupted. Other overlay options may continue to work for some time, but new connections are often not possible, and the network can degrade rapidly.
Relays are are a similar story, but with an additional reason: We don't have to limit our customers' relay bandwidth due to cost. When hosting relays on behalf of others, we would be transiting a lot of traffic, which has an associated (sometimes unpredictable) cost. By letting our customers host relays, they can ensure relay traffic is just as fast as direclt connections.
That's a great question! One of the things I enjoyed during my time at Slack was their willingness to contribute to open source projects. We had similar IP clauses, but asking permission to open source things was straightforward.
The most important concern (IMO), was considering whether we could commit to properly maintaining a project. Before open sourcing anything, you need to discuss how you'll go about managing an issue and pull request backlog, so that people don't come across "dead" projects under your stewardship.
In a high growth startup, I do think something like this could happen again, but as a company grows, there are certainly more layers that can make it difficult to share things openly.
We have an automated set of ansible scripts that spin up large groups of hosts for Nebula performance regression testing, and a while back I added zerotier, tailscale, wireguard-userspace, wireguard, tinc, ipsec, and openvpn to that automation so I could get a sense of where things stand. I spent a lot of time optimizing each of the above options to make fair comparisons, but it was mostly for mine and the team's curiosity, and we weren't interested in playing benchmark-fight with similar softwares of the world.
Publishing repeatable benchmarks is hard, and when doing open source work, it just hasn't been a priority. As I replied above, if I'm going to say it I should prove it, and I promised to do just that.
And a counterpoint: tailscale does mention in the "Tailscale vs Nebula" article on their website that performance is just about the same but similarly provides no proof. This is motivation enough for me to show proof of the opposite, I guess.
I mean... the title of the Tailscale blog post is "Tailscale raises $100M… to fix the Internet", and that's pretty massive scale. /s
I don't have 100k hosts on a large network to test deploying Tailscale, but if I did, I'd be benchmarking the cpu/network/storage overhead of telling 99,999 hosts about a new one that comes online, every time that happens, or every time its pubkey changes. You can optimize this away _if_ your "fan out" is not as large, but there are plenty of cases where every host on your network needs to talk to a particular host, so all of them need to know about its keys as soon as possible.
Again these aren't unsolvable problems, to a point, but we didn't want to solve a problem when we could avoid it entirely, so that's the path we chose. It removes complexity and is a good part of the reason the system we built has been resilient.
A complaint some people express about tailscale is the battery life on mobile (or at least iOS). This exists because there is coordination overhead on even idle tailscale nodes. Back when we ported Nebula to iOS, we sweated details like "how often it wakes the radios" and did a lot of profiling. I never turn Nebula "off" on my iPhone, and it just sits in there in the background not using any resources most of the time.
We worked hard to optimize this out of our architecture, so that Nebula avoids generating traffic that is unrelated to the actual communication between hosts or lookups to lighthouses. An idle nebula tunnel can truly be idle indefinitely, and that also matters as the set of hosts becomes larger.
I do not think the Nebula project and Tailscale are direct replacements for each other in any fashion, and afaik neither is trying to be. I'm just pointing out that different design goals led to unique advantages and disadvantages to each architecture.
The Nebula CA we built at Slack was very specific to Slack's internal devops, and just wasn't generalizable. It is highly automated there, and is custom tooling, just as you describe. The open source version is somewhat bare bones (a command line tool for CA vs something like vault).
I will say that the OSS tooling of Nebula is everything someone needs to stand up an entire working network on every common platform (linux/mac/windows/ios/android), but there is a definite gap in simplification that we need to address to make it easier for smaller scale use cases.
We actually have a managed enterprise Nebula offering at my current gig, but that's rather a different market than Tailscale, so I'm avoiding talking as that company as opposed to a Nebula OSS project lead. The commercial offering is targeted at large enterprises, because that's the market where Nebula has unique advantages. It also means we don't currently have a freemium or smb type offering, and are not prioritizing creating one at all. I don't want to give people false hope that we will, and would prefer to see the OSS project improve to address the small-medium use cases.
Another fair criticism. We will publish the benchmarks and make them repeatable (which most existing ones I've found don't bother to do). We hadn't done so because Tailscale isn't really seen as a direct competitor to what the Nebula project is doing, but if people want numbers, that's a thing we are happy to provide.
Fair enough. I am sure the key distribution is fast and all that, but not needing peer key distribution at all was a goal and the overhead associated is less scalable than just not doing it at all. Regardless, very cool that you can handle that many nodes, which is a hard problem. I assume you do just-in-time key distribution or something, because (n-1) distribution of peer keys would be ... less than ideal.
Anywho, the more important bit is my point about performance. Nebula is significantly faster than userspace Wireguard, and plain userspace Wireguard is (last I checked) a bit faster than Tailscale, due to the additional code needed for things like your ACLs. At gigabit type scale it is probably fine and not noticeable, but at Slack, we needed to scale to 10G+ on links, while ensuring we didn't take a significant hit on CPU resources.
Again, I think Tailscale is very good for its target use case as a VPN replacement, and congrats on raising these funds!
It does! In fact replacing AWS security groups and making them cross region and cross platform was probably the first goal of the project. My coauthor, Nate, wrote Nebula's internal firewall code before we wrote a single line of the actual protocol, because he wanted to ensure it was performant enough for massive scale.
People sometimes ask me to describe the differences between Nebula and Tailscale. One of the most important relates to performance and scale. Nebula can handle the amount of internal network traffic and scalability of nodes (100k+ nodes, constant churn) required on a large network like Slack's, but Tailscale cannot. Tailscale's performance is fine for many situations, but not suitable for infrastructure. It is just a fundamentally different set of goals.
Nebula was created and open sourced before Tailscale was offering their product, but their architecture is similar to older offerings in the market, and is something we purposely avoided when creating Nebula.
Fwiw, I even recommend Tailscale to friends who want to do things like connect to their Plex server or Synology or [other thing] at home remotely. It simplifies this kind of thing greatly and doesn't require you to set up any infrastructure you control directly, which can be a headache for folks who just want to reach a handful of computers/devices.
We briefly considered building something atop Wireguard in the early days of Nebula, but decided not to do so because of scaling. Wireguard's protocol necessitates that all nodes have existing keypairs for each other ahead of time. At Slack's scale, that means every time a fresh node is launched, you would have to tell 50,000 other nodes it exists.
Obviously you can smarten this up and tell only hosts it might talk to. But this adds complexity. Using PKI eliminates this key distribution problem and means that you don't have the same scaling limitations as something built on WG.
Wireguard is a very very good VPN, but I cannot imagine trying to run something on the scale of tens of thousands of nodes when you need such complex coordination systems to exchange keys/trust, especially in a dynamic environment where nodes are coming and going all the time.
I totally get that it solvable overall, but Slack has had 4 years of nearly perfect uptime on Nebula, whilst using it to pass >95% of all backend traffic. These considerations may seem simple to address, but there are fundamentals that mattered and led us to writing Nebula. We didn't want to create something new, but to do what Slack needed, we had to.
I wasn't commenting on the strength of RSA-1024, per se, but on the assumed age of that key. OpenSSH's ssh-keygen hasn't defaulted to 1024 bit RSA keys since before version 4.2, in 2005. (I had to look it up: https://www.openssh.com/releasenotes.html)
You can still generate a 1024 bit RSA key, but someone would have to go out of their way to do so, and I can't imagine why they would have done that in the past .. decade?
The author of this article should consider following their own advice, since they have a woefully outdated RSA-1024 ssh key securing their GitHub account.
It is, admittedly, impossible for me to be unbiased in this discussion (coauthor of Nebula, hi), but I strongly disagree that your client code is your most important component, from a trust perspective.
Your coordination server tells every node about every other node and distributes the keys for the entire network. Everything on a tailscale network implicitly trusts your coordination service.
If an individual client is compromised, code or otherwise, the effect is more limited than your coordination service being compromised, in which case the entire system's trust is broken.
Every aspiring programmer should learn C. They should also learn multiple dialects of ASM. Learning these things helps you better understand how computers fundamentally work, and knowing how computers work pushes you to write better code in any language. Ignoring how computers organize data can lead to inefficient code in any language.
That said, if you are writing something new, you should carefully consider whether C is the best choice before using it. If you are working within a nearly-impossible-to-replace + enormous codebase (such as the Linux kernel), it is the only option. If your project's #1 goal is performance above all else, and you are a seasoned or aspiring expert, perhaps C is the best choice. The majority of people writing software do not fall into either of these categories.
eBPF is great, and we plan to support it as our collection mechanism, but not today and maybe not soon. When we wrote go-audit, there were few, (if any?), distros that had eBPF kernel support. Now Ubuntu 16.04 has support, as do many others, and that is great!
But..
Releasing a tool that will work for most people today is very different to releasing one that will work for most people in a couple of years. We are sharing this imperfect tool that uses an using an imperfect syscall monitoring mechanism, both of which were written by imperfect humans.
We have found plenty of problems with auditd during development (some real facepalm stuff, to be sure), but it also does many useful things. We have worked around limitations and very definitely stress tested it in our environment. A lot. A lot lot.
If you don't trust auditd, that's a totally valid opinion to hold. I welcome criticism of our approach, but a PSA that doesn't involve having testing our tool is rather unfair.
Our decision to leave lighthouse hosting in the hands of users has one primary rationale: We want users to have complete control their network availability. Any downtime of our service should not impact their network availability. You can even host some of your lighthouses inside of network boundaries to ensure that an internal network functions properly if its connection to the internet is interrupted. Other overlay options may continue to work for some time, but new connections are often not possible, and the network can degrade rapidly.
Relays are are a similar story, but with an additional reason: We don't have to limit our customers' relay bandwidth due to cost. When hosting relays on behalf of others, we would be transiting a lot of traffic, which has an associated (sometimes unpredictable) cost. By letting our customers host relays, they can ensure relay traffic is just as fast as direclt connections.