If you have the August 13, 2024—KB5041580 update. You’re good.
No NAT doesn’t mean no firewall. It just means that you both don’t have to deal with NAT fuckery or the various hacks meant to punch a hole through it.
Behind NAT, hosting multiple instances of some service that uses fixed port numbers requires a load-balancer or proxy that supports virtual hosts. Behind CGNAT, good luck hosting anything.
For “just works” peer to peer services like playing an online co-op game with a friend, users can’t be expected to understand what port forwarding is, let alone how it works. So, we have UPnP for that… except, it doesn’t work behind double NAT, and it’s a gaping security hole because you can expose arbitrary ports of other devices if the router isn’t set up to ignore those requests. Or, if that’s not enough of a bad idea, we have clever abuse of IP packets to trick two routers into thinking they each initiated an outbound connection with the other.
can you tell me if any device in an IPv6 LAN can just assign itself more IP v6 adresses and thereby bypass any fw rule?
IPv6 has two main types of non-broadcast addresses to think about: link-local (fe80::) and public.
A device can self-assign a link-local address, but it only provides direct access to other devices connected to the same physical network. This would be used for peer discovery, such as asking every device if they are capable of acting as a router.
Once it finds the router, there are two ways it can get an IP address that can reach the wider internet: SLAAC and DHCPv6. SLAAC involves the device picking its own unique address from the block of addresses the router advertises itself as owning, which is likely what you’re concerned about. One option for ensuring a device can’t just pick a different address and pretend to be a new device is by giving it a subset of the router’s full public address space to work with, so no matter what address it picks, it always picks something within a range exclusively assigned to it.
Edit: I butchered the explanation by tying to simplify it. Rewrote it to try again.
In most cases, the router advertises the prefix, and the devices choose their own IPv6. Unless you run DHCPv6 (which really no-one does in reality, I don’t even think android will use it if present).
It doesn’t allow firewall bypass though, as the other commenter noted.
Honestly, I think most fear of IPv6 is just borne out of ignorance and assigning their understanding of IPv4 onto IPv6 and making assumptions.
Not if your firewall router is setup right (strict mac address filtering)
so back to the beginning of this thread: ipv6 in home lans is likely to be unsafe due to the defaults in some/many/most routers? and those ipv6 devices can in these szenarios escalate their permissions be spawning new ip adresses that would overcome lazy output fw rules?
thanks for all the explaining here so far!
or if i upload a malicious apk to some smartTV and have a it spawn a dhvpv6 server and then spawn a new virtual device that would be given an IP by my fake dhcpv6 to bypass. and we all can use macaddresschanger.
so you say with macfiltering the router would still prevent unwanted direct connections between my c&c server and some malicious virtual device? that’d be cool, but i dont understand how.
