The best solution is for them to be accessed through a publicly registered hostname e.g. https://router0123.netgear.com (that would only resolve locally). They could provision certificates for themselves using the Let's Encrypt DNS challenge.
Or would every router get its own certificate? But then netgear would have to become its own CA.
Why? They could just partner with an existing CA, like Cloudflare does with Comodo.
And how would DNS hijacking be an issue? The attacker wouldn't be able to produce a valid cert anyway (the router would come with a custom burned-in key that it would use to authenticate itself to the CA and get the cert).
I take apart the router, and get a valid certificate
You only get a valid certificate for your router's address. But if you can take apart the router, you don't need to hijack the DNS, you can simply control its traffic.
But if you're a guest in my home and I see you take apart my router, you'll have to answer a few questions. Same in an office or coffeshop. Having LAN access doesn't mean you have complete physical control of the router. So the HTTPS is not useless.
Considering basically every router has the same address
They have the same IP address, not necessarily the same DNS hostname, which is what the certificates are tied to. The user would just be told to connect to the hostname (possibly printed in the sticker) rather than to the IP.
That's certainly one option, but what happens now if I change the IP of the router in its config, because I use multiple in my LAN, one as router, the others as AP?
There is no option for any of this that isn't completely messy and hacky
No, because the implication here is that the private key for these router0123.netgear.com type hostnames will be known to the consumer devices that are serving the pages, so they will be essentially public.
I think the idea is each device has its own FQDN, and gets its own certificates. Thus, breaking open your router only gets you "your" private key, they'd all be different. Buying one on eBay might be risky, but if you buy sketchy network hardware on eBay you're at risk in so many ways already...
You can't do this with Let's Encrypt out of the box (unless you make small numbers bespoke devices) because of their Rate Limits. But several commercial public CAs like Comodo would probably be interested in cutting a deal with a big electronics manufacturer or a trade group.
Correct. The rate limits for the parent domain wouldn't apply if it was added to the public suffix list. The IP restriction wouldn't apply because every router would be requesting from a different IP.
This doesn't make a whole lot of sense as a viable deployment strategy. The routers would necessarily need to ask for the domain name in question to be pointed at their internet-facing, public IP (if indeed they even have one!), because that's all that Lets Encrypt could possibly verify, but the administration interface is usually on a private RFC1918 address. And what secure protocol are you going to use for the router to request that domain name update?
And how is first time setup supposed to work anyway? You need to connect to the administration interface to give it your ISP credentials before it can connect to the internet and obtain its Lets Encrypt certificate.
If you forget about Lets Encrypt and instead point hundreds of thousands of router-<serial>.vendor.com addresses at 192.168.0.1, with a pre-made certificate, you then only have the problems of baking an individual private key into each router at the factory and boxing customised documentation (like maybe a sticker on the router itself) telling the user what the unique domain name is they need to setup their device. Oh, and the problem of what to do when the user wants to change the local address used by their router.
I suppose it really depends on your threat model. I think most offices will be fine with the warning. However, you could configure each device to only respond to the trusted IP address of a HTTPS proxy which at least lowers the attack surface for snooping.
wait, wait, wait, are you saying a "trusted ip address" out on the web? or requiring every office to set up their own https proxy? Cause a "trusted IP address" out on the web would just be insane... "Oh, let's just send my login to and give full access to my network to this third party/manufacturer."
