Comment by fc417fc802
17 days ago
It's also trivial to roll your own version of dropbox. With IPv6 it's possible to fail to configure those nftables rules. The firewall could be turned off.
In theory you could turn off IPv4 NAT as well but in practice most ISPs will only give you a single address. That makes it functionally impossible to misconfigure. I inadvertently plugged the WAN cable directly into my LAN one time and my ISP's DHCP server promptly banned my ONT entirely.
> In theory you could turn off IPv4 NAT as well but in practice most ISPs will only give you a single address
So, I randomly discovered the other day that my ISP has given me a full /28.
But I have no idea how to actually configure my router to forward those extra IP addresses inside my network. In practice, modern routers just aren't expecting to handle this, there is no easy "turn of NAT" button.
It's possible (at least on my EdgeRouterX), but I have to configure all the routing manually, and there doesn't seem to be much documentation.
You should be able to disable the firewall from the GUI or CLI for Ubiquiti routers. If you don't want to deal with configuring static IPs for each individual device, you can keep DHCP enabled in the router but set the /28 as your lease pool.
> So, I randomly discovered the other day that my ISP has given me a full /28.
Where is this? Here new ISP customers don't even get a single IPv4 unless you beg for it.
Not even CGNAT?
In the US many large companies (not just ISPs) still have fairly large historic IPv4 allocations. Thus most residential ISPs will hand you a single publicly routable IPv4 regardless of if you're using IPv6 or not.
We'll probably still be writing paper checks, using magnetic stripe credit cards, and routing IPv4 well past 2050 if things go how they usually do.
Out of curiosity how did you discover this?
Went to double check what my static IP address was, and noticed the router was displaying it as 198.51.100.48/28 (not my real IP).
I don't think the router used to show subnets like that, but it recently got a major firmware update... Or maybe I just never noticed, I've had that static IP allocation for over 5 years. My ISP gave it to me for free after I complained about their CGNAT being broken for like the 3th time.
Guess they decided it was cheaper to just gave me a free static IPv4 address rather than actually looking at the Wireshark logs I had proving their CGNAT was doing weird things again.
Not sure if they gave me a full /28 by mistake, or as some kind of apology. Guess they have plenty of IPs now thanks to CGNAT.
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> With IPv6 it's possible to fail to configure those nftables rules. The firewall could be turned off.
So what? It's not like you get SNAT without a couple netfilter rules either.
This argument doesn't pass muster, sorry. Consumer and SOHO gear should come with a safe configuration out of the box, it's not rocket science.
Did you even read the second paragraph of the (rather short) comment you're replying to? In most residential scenarios you literally can't turn off NAT and still have things work. Either you are running NAT or you are not connected. Meanwhile the same ISP is (typically) happy to hand out unlimited globally routable IPv6 addresses to you.
I agree though, being able to depend on a safe default deny configuration would more or less make switching a drop in replacement. That would be fantastic, and maybe things have improved to that level, but then again history has a tendency to repeat itself. Most stuff related to computing isn't exactly known for a good security track record at this point.
But that's getting rather off topic. The dispute was about whether or not NAT of IPv4 is of reasonable benefit to end user security in practice, not about whether or not typical IPv6 equipment provides a suitable alternative.
> But that's getting rather off topic. The dispute was about whether or not NAT of IPv4 is of reasonable benefit to end user security in practice, not about whether or not typical IPv6 equipment provides a suitable alternative.
And, my argument, is that the only substantial difference is the action of a netfilter rule being MASQUERADE instead of ALLOW.
This is what literally everyone here, including yourself, continues to miss. Dynamic source NAT is literally a set of stateful firewall rules that have an action to modify src_ip and src_port in a packet header, and add the mapping to a connecting tracking table so that return packets can be identified and then mapped on the way back.
There's no need to do address and port translation with IPv6, so the only difference to secure an IPv6 network is your masquerade rule turns into "accept established, related". That's it, that's the magic! There's no magical extra security from "NAT" - in fact, there are ways to implement SNAT that do not properly validate that traffic is coming from an established connection; which, ironically, we routinely rely on to make things like STUN/TURN work!
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