incusd/firewall: Restrict wildcard proxy NAT to local addresses - #3824
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jochumdev wants to merge 1 commit into
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incusd/firewall: Restrict wildcard proxy NAT to local addresses#3824jochumdev wants to merge 1 commit into
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A proxy device with a wildcard listen address (0.0.0.0 or ::) generated DNAT rules with no destination match at all, in both the nat prerouting and nat output hooks, so every packet with a matching destination port was redirected to the instance regardless of where it was headed. With br_netfilter loaded, which proxy NAT requires, that included traffic between containers on the same bridge and outbound traffic from both instances and the host. Match "fib daddr type local" instead, so a wildcard listen address means any of the host's own addresses rather than any address at all. The output hook also excludes the loopback prefix; prerouting needs no such exclusion, as the output hook initializes the conntrack DST binding first for loopback flows. Add a "meta nfproto" match too, as without a destination address nothing constrained the rules to the DNAT target's address family. Fixes: dcf2c22 ("incusd/firewall: Allow wildcard listen address in proxy NAT") Signed-off-by: René Jochum <rene@jochum.dev>
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A proxy device with a wildcard listen address (0.0.0.0 or ::) generated DNAT rules with no destination match at all, in both the nat prerouting and nat output hooks, so every packet with a matching destination port was redirected to the instance regardless of where it was headed. With br_netfilter loaded, which proxy NAT requires, that included traffic between containers on the same bridge and outbound traffic from both instances and the host.
Match "fib daddr type local" instead, so a wildcard listen address means any of the host's own addresses rather than any address at all. The output hook also excludes the loopback prefix; prerouting needs no such exclusion, as the output hook initializes the conntrack DST binding first for loopback flows. Add a "meta nfproto" match too, as without a destination address nothing constrained the rules to the DNAT target's address family.
Fixes: dcf2c22 ("incusd/firewall: Allow wildcard listen address in proxy NAT")