Creating CName entry that points to self kills DNS Service

[jessechahal]

while I was playing around with CName entries in the Web GUI I ended up creating a CName that pointed to itself. Essentially I did something like CName Jesse.Chahal == jesse.chahal. The entry got written to the /etc/dnsmasq.d/05-pihole-custom-cname.conf but made it so the DNS Service could no longer start. I had to manually go into the file to prune to entry so DNS could start back up.

I guess the main issue's are:

1. the backend should ignore/error case for ascii characters for all DNS entries. Front-end should display appropriate message to the end user if error. --> this is because DNS records are case insensitive (at least for english characters).
2. You should not be able to create CName records that point back to itself.

[yubiuser]

[2022-10-20 06:41:46.574 22783M] FATAL ERROR in dnsmasq core: CNAME loop involving jesse.chahal

[rdwebdesign]

We can verify the value on the web interface, but the problem also exists when using the command line.

[yubiuser]

Fixed with https://github.com/pi-hole/AdminLTE/releases/tag/v5.17