I installed Lede 17.01.4 on a TP-Link router, and I want to use its web interface through https. I followed this doc for it: https://openwrt.org/docs/guide-user/luci/getting-rid-of-luci-https-certificate-warnings
Unfortunately, I still cannot connect to it with https. I think, my cert is correct. I wanted to check logs, but I found no logs! In /var/log there are lastlog and wtmp, but they are empty. According to ps, /sbin/logd -S 64 is running.
I had the same issue once. HTTPS just stopped working, I don't know what caused it but it resolved itself after a few flashes with the firmware I am using. As a workaround I enabled http access until it got resolved.
Are you using Chrome? Does it occur with any other browser?
The RFC depreciated using the CN for IP & DNS names over two decades ago due to the ability to exploit a connection using a cert with an IP or DNS as it's CN. Chrome finally dropped support for IP & DNS names in the CN about a year ago. (I've corrected the wiki linked to in the OP)
The correct way to specify IP and DNS names are in the SAN profile. You can utilize the OpenSSL Certificates wiki to generate a self-signed CA to sign the SSL cert with
It should be noted while the luci-ssl packages & the wiki linked to in the OP will generate a self-signed cert, this is the laziest and most insecure way of securing HTTPS, as it opens up the possiblity of a MITM attack.
While a MITM attack is unlikely on a LAN, the potential exists and will always remain... considering it's quite easy to generate a self-signed CA and use that self-signed CA to sign the SSL cert, there's no reason why this should not be the norm.
Either way, you can utilize the OpenSSL Certificates wiki to generate the self-signed CA and signed SSL cert.
You can find the script blocks within the /etc/init.d/uhttpd script
There is no such thing as a secure self-signed cert, as, by definition, it lacks a chain of trust, having no way to verify it's validity, of which makes a MITM attack possible.
While the OpenSSL Certificates wiki is under the VPN section, the exact same steps can be utilized to create a self-signed CA, which can then be used to sign the uhttpd [LuCI] cert (if you were using openssl).
Since you're using mbed, I couldn't tell you what the method is for it, as I've never used anything other than openssl
If you have multiple routers/servers, it's recommended to create a self-signed master CA that's used exclusively to only sign other ICAs (each router and VPN server should have their own ICA).