As an ‘experiment’ I tried switching from my own local ‘adblocking’ solution to using an upstream adblocking resolver, eg. cloudflare’s 1.1.1.2 or 1.1.1.3 service.
The local adblock solution uses (multiple!) ‘—address/naughtydomain.foo/‘ lines that cause dnsmasq to return ’NXDOMAIN’ - fair enough. Cloudflare (& others I’ve tested) return ‘0.0.0.0’ or ‘::’ instead, not NXDOMAIN. With rebind protection enabled (--stop-dns-rebind), even with --rebind-localhost-ok I get log ’spam’ warning of possible rebind attacks due to the ‘0.0.0.0’ address response. I can turn ‘0.0.0.0’ into NXDOMAIN by using --bogus-nxdomain=0.0.0.0 and that works fine and stops the rebind warnings. However ‘::’ still gets through if an AAAA is specifically requested. There is no equivalent bogus-nxdomain for ipv6. The dnsmasq manpage (under —address) advised "Note that NULL addresses [0.0.0.0 & ::] normally work in the same way as localhost, so beware that clients looking up these names are likely to end up talking to themselves.” Ideally then 0.0.0.0 & :: would both be turned into NXDOMAIN. Should ‘0.0.0.0/32’ be excluded from the rebind checks/accepted by the ‘—rebind-localhost-ok’ option. It’s currently being caught by a ‘0.0.0.0/8’ check. Cheers, Kevin D-B gpg: 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A
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