This patch fixes the AppArmor profile path clause and adds
(currently ignored) network rules.
The AppArmor profile used to be defined for the path sbin/dnscrypt-proxy,
but the real path is bin/dnscrypt-proxy (due to sbin now being a symlink
to bin), which permitted the service to run unconfined.
Adding the network rules has no effect other than improving correctness,
as the version of AppArmor in the NixOS kernel fails to enforce network
rules.
The dnscrypt-proxy service relays regular DNS queries to
a DNSCrypt enabled upstream resolver.
The traffic between the client and the upstream resolver is
encrypted and authenticated, which may mitigate the risk of
MITM attacks and third-party snooping (assuming a trustworthy
upstream).
Though dnscrypt-proxy can run as a standalone DNS client,
the recommended setup is to use it as a forwarder for a
caching DNS client.
To use dnscrypt-proxy as a forwarder for dnsmasq, do
```nix
{
# ...
networking.nameservers = [ "127.0.0.1" ];
networking.dhcpcd.extraConfig = "nohook resolv.conf";
services.dnscrypt-proxy.enable = true;
services.dnscrypt-proxy.localAddress = "127.0.0.1";
services.dnscrypt-proxy.port = 40;
services.dnsmasq.enable = true;
services.dnsmasq.extraConfig = ''
no-resolv
server=127.0.0.1#40
listen-address=127.0.0.1
'';
# ...
}
```
