This is a request for feature feasibility or acceptability.

Some circumstances may be vulnerable to DNS rebinding attacks against global IPv6 address. Through DHPCv6-PD the local network is a uniquely identifying global subnet. This makes DNS rebinding to a local machine on its global IPv6 as easy as traditional RFC1918. It would be a good idea to eliminate any local network IP (RFC1918 or otherwise) from global DNS responses.

For dnsmasq, this could be implemented with a few options or option variations. One option is to rebind protect range on all DHCP served address, if outside of the normal local IPv4/6 ranges. Another option would add the IPv4/6 discovered on an interface to the rebind protection range. Granted few small installations (dnsmasq user base) have the cash for a global IPv4, but maybe implement this generically for completeness. This could either reuse the current option or create a new option. The following is just a rough concept.

without sub options, it takes its original actions

add DHCPv4/v6 address into the rebind protection range. Tag is optional to include only include limited subnets, else all DHCP server ranges are added.

uses the same method as the DHCPv6 construction to obtain the subnet IPv6 prefix. May not work or be implemented for IPv4.

just insert any address into the rebind protection range.

Notable use case: if you actually have outward facing servers such as http or vpn, then they should probably be on a unique subnet DMZ. If excluding those interfaces in the rebind protection (maybe =dhcp,[tag]), or running a separate dnsmasq instance for the subnet, then such subnet would resolve globally and locally without filtering.


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