Yes, in a very superficial sense, you can't literally route a packet over the internet backwards to a host behind NAT without matching a state entry or explicit port forwarding. But implementing NAT on it's own says nothing about the behavior of your router firewall with regards to receiving Martians, or with regards to whether the router firewall itself accepts connections and if the router firewall itself isn't running some service which causes exposure.
To actually protect things behind NAT you still need firewall rules and you can keep those rules even when you are not using NAT. Thus those rules, and by extension the protection, are separable from the concept of NAT.
This is the kind of weird argument that has caused a lot of people who hadn't ever used IPv6 to avoid trying it.
NAT a.k.a IP masquerading does not do that, it only figures out that some ingress packets whose DST is the gateway actually map to previous packets coming from a LAN endpoint that have been masqueraded before, performs the reverse masquerading, and routes the new packet there.
But plop in a route to the network behind and unmatched ingress packets definitely get routed to the internal side. To have that not happen you need to drop those unmatched ingress packets, and that's the firewall doing that.
Fun fact: some decade ago an ISP where I lived screwed that up. A neighbour and I figured out the network was something like that:
192.168.1.x --- 192.168.1.1 --
\
10.0.0.x ----> WAN
/
192.168.2.x --- 192.168.2.1 --
You'd never see that 10.0.0.x usually as things towards WAN would get NAT'd (twice). But 10.0.0.x would know about both of the 192, so you just had to add respective routes to each other in the 192.168.x.1 and bam you'd be able to have packets fly through both ways, NAT be damned.
Network Address Translation is not a firewall and provides no magically imbued protection.
* https://kb.netgear.com/25891/What-is-the-De-Militarized-Zone...
Don’t forget source routing. That said, depending on your threat model, it’s not entirely unreasonable to just rely on your ISP’s configuration to protect you from stuff like this, specifically behind an IANA private range.
It's like we've been collectively trained to think of RFC1918 as "safe" and forgotten what a firewall is. It's one of those "a little knowledge is a dangerous thing" things.
The vast, vast majority of people do not know what NAT is: ask your mom, aunt, uncle, grandma, cousin(s), etc. They simply have a 'magic box' (often from the ISP) that "connects to Internet". People connect to it (now mostly via Wifi) and they are "on the Internet".
They do not know about IPv4 or IPv6 (or ARP, or DHCP, or SLAAC).
As long as the magic box is stateful inspecting traffic, which is done for IPv4-NAT, and for IPv6 firewalls, it makes no practical difference which address family you are using from a security perspective.
The rending of garments over having a globally routable IPv6 address (but not globally reachable, because of SPI) on your home is just silliness.
If you think NAT addresses are safe because… of any reason whatsoever really… simply shows a lack of network understanding. You might as well be talking to a Flat Earther about orbital mechanics.
Death , taxes and transfer fees
This is probably a result of all AWS services being independent teams with their own release schedule. But it would have made sense for AWS to coordinate this better.
It’s a (small) moving part we now have to maintain. But it’s very much worth the massive cost savings in NATGateway-Bytes.
A big part of OpsLevel is we receive all kinds of event and payload data from prod systems, so as we grew, so did our network costs. fck-nat turned that growing variable cost into an adorably small fixed one.
i've had to look at my nat gateway zero times since i set it up a couple years ago. i can't say that about any VM host i've got. to me, that's easily worth the few dollars a month that aws charges for it. it's cheaper than hiring somebody, and it's cheaper than me.
That said, the paid NAT gateways do also publish metrics. That can be nice when debugging a legitimate issue, such as when your gateway actually runs out of NAT ports to use.
2) Companies will happily pay thousands in recurring fees for the built-in NAT gateway, but if an engineer asks for even half that as a one-off sum to motivate them to learn Linux networking/firewalling, they'd get a hard no, so why should they bother?
No your service does not need the extra .099% availability for 100x the price...
Make your own VPN while you are at it, wireguard is basically the same config.
For personal a cheap vps will end up costing around the same as something you can do on your own, without the risk of messing up your machine/network from a vulnerable endpont
Only a tiny minority of people have to look at those addresses, the majority just types "facebook", enter, clicks on first google result and gets facebook (because ".com" is too hard to write).
Yet again, another fundamental misunderstanding (either genuine or not, I'm not sure) about the low-level technologies and their origins that underpin all of this. "Can't we just..."? No.
Modern devs are helpless in the face of things I taught myself to do in a day or two when I was fourteen, and they’re paralyzed with terror at the thought of running something.
It’s “hard” goes the cliche. Networking is “hard.” Sys admin is “hard.” Everything is “hard” so you’d better pay an expert to do it.
Where do we get these experts? Ever wonder that?
It’s just depressing. Why even bother.
It really makes me worry about who will keep all this stuff running or build anything new in the future if we are losing not only skills but spine and curiosity. Maybe AI.
And when you got things wrong back in the day, you came home from school, saw a very weirdly behaving computer, grumbled and reinstalled the OS. Nowadays it is a very different story with potentially very severe consequences.
And this is just about getting things wrong at home, in corporate environment it is 100x more annoying. In corporate, anyway you spend 80% of the development time figuring out how to do things and then 20% on actual work, nobody will have the time to teach themselves something out of their domain.
OSes are more secure. Isolation is better. Languages are better. Hardware is vastly cheaper and faster and more reliable. Everything is easier and faster and better.
In the corp world we have this absurd embarrassment of riches. There are like ten choices in every category. Half of it is free. It’s easier to set up and run than it was back then. Way easier. Hosting is silly cheap if you compare cost / performance.
People are just incurious and brainwashed with this weird sense of helplessness.
This security phobia is so overblown if you take some basic precautions and don’t run crap service software.
If I were hosting something controversial that might draw the ire of one of the insane political cults out there I’d run it through a free CDN maybe. That’s easy.
I think of AI as a kind of floor, a minimum required skill to be able to get a job as a professional anything. If you want to find paid work as a developer, you have to at least be better than AI at the job.
Optimistically AI will filter out all the helpless Devs who can't get anything done from the job market. "Code monkeys" won't be a thing.
Juniors will have to enter unpaid trainee programs I guess, but that might not be such a bad thing
I'm only in my 30s but I was thinking recently "when I'm retired I feel like I'm going to be telling stories about how back in my day we had this thing called the filesystem and you'd just browse it directly..."
The bash configuration is literally a few lines:
cat <<'EOF' | sudo tee /etc/sysctl.d/99-ip-forwarding.conf > /dev/null
net.ipv4.ip_forward=1
EOF
sudo sysctl --system
sudo iptables -t nat -A POSTROUTING -o ens5 -j MASQUERADE
sudo iptables -F FORWARD
sudo iptables -A FORWARD -i ens5 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -o ens5 -j ACCEPT
sudo iptables-save | sudo tee /etc/iptables/rules.v4 > /dev/null
Also, don’t assign a EIP to your EC2 NAT instances (unless you absolutely must persist a given public IP) as that counterintuitively routes through public traffic. Just use a auto-assigned public IP (no EIP).
NAT instance with EIP
- AWS routes it through the public AWS network infrastructure (hairpinning).
- You get charged $0.01/GB regional data transfer, even if in the same AZ.Could you point me to somewhere I can read more about this? I didn't know there was an extra charge for using an EIP (other than for the EIP itself).
That's what you did before AWS had the "NAT Gateway" managed service. It's literally called "NAT Instance" in current AWS documentation, and you can implement it in any way you wish. Of course, you don't have to limit yourself to iptables/nftables etc. OPNsense is a great way to do a NAT instance.
> NAT AMI is built on the last version of the Amazon Linux AMI, 2018.03, which reached the end of standard support on December 31, 2020 and end of maintenance support on December 31, 2023.
Then I run my stuff locally.
And then I use ssh tunneling to forward the port to localhost of the remote machine. Its a unit file, and will reconstruct the tunnel every 30s if broken. So at most 30s downtime.
Then nginx picks it up.
I use Tailscale myself, but if you want everything totally under your control (and don't want to go to the trouble of setting up headscale or something similar) then that's one of the absolutely simplest, lowest-effort ways of doing it. EDIT: Well, except for the VPS box I suppose, but if that provider went down or you had any reason to suspect they were doing anything suspicious, it would be quite simple to jump to a different provider, so that's pretty darn close to controlling everything yourself.
Particular things: I use letsencrypt wildcard, so my subdomains aren't leaked. If you register per subdomain, LE leaks all your subdomains as part of some transparency report. Learned that and had to burn that domain.
The VPS is from LowEndBox. Like 2 core, 20GB storage 2GB ram. But runs perfectly fine.
I run jellyfin, audiobookshelf, Navidrome, and Romm. Ssh tunnel per application.
It would also be trivial to switch providers as well. But again, not a seed box, not doing torrents, not doing anything that would attract attention. And best of all, no evidence on the VPS. Its all SSL and SSH.
Client automatically deals with reconnecting, never have to touch it.
SSH tunnel would have been simpler, just didn’t want it open.
SSH tunnel probably needs the keep alive on, otherwise connection loss may not be detected.
It is a damn service, which is defined as "you pay someone to do it".
(your second sentence is a bit confusing)
Repeat after me: NAT is not a firewall. And we need to stop pretending it is.
Security is not the purpose of a NAT. It's there to give you more IPs than you have. There's all sorts of NAT hole punching techniques. If you want a firewall, you need a firewall.
The last part isn't adding the security, and you can absolutely NAT without preventing the "outside" subnets from being allowed to route to the "inside" subnet, it's just that NAT is almost always done on the box providing the stateful firewall too so people tend to think of the 3 functions as combined in concept as well.
Shoutout to Hacker News for having IPv6 support!
And virtually everything inside of AWS still requires IPv4 so even if you have zero need to reach out to WAN, if you need any number of private AWS endpoints, you're going to be allocating some ipv4 blocks to your VPC :(.
2.) Market segmentation: keeps home users from easily hosting their own services without spending $$$ on an upgraded plan.
3.) Adding on to #2, I've seen claims of providers putting IPv6 behind NAT, so don't think full IPv6 acceptance will solve this problem.
I get annoyed even when what's offered is a single /64 prefix (rather than something like a /56 or even /60), but putting IPv6 behind NAT is just ridiculous.
Instead I played with IPv6 at home to make sure I understood it well enough should it ever come up at work. We'll see!
For someone just getting started with networking and learning things, this seems rhe best way to go forward.
Port forwarding, external/internal address split, split horizon DNS, SNI proxies, NAT, hairpin routing - some of the hacks made mostly because of shortage in IP space.
Using both GUA/ULA together solves enough to get by, but its not ideal
Why state this as absolute fact? Seems a bit lacking in epistemic humility.
Wait, is "seems lacking in epistemic humility" just coded language for "I disagree, therefore you couldn't possibly be thoughtful"?