Pi-hole as All-Around DNS Solution - raspbian little

pihole_recursive_dns.sh

#!/usr/bin/env bash

## Setting up Pi-hole as a recursive DNS server solution¶
## https://docs.pi-hole.net/guides/unbound/

## 1. The first thing you need to do is to install the recursive DNS resolver:
sudo apt update
sudo apt -y install unbound

## 2. Important: Download the current root hints file
## (the list of primary root servers which are serving the domain "." - the root domain).
## Update it roughly every six months. Note that this file changes infrequently.
wget -O root.hints https://www.internic.net/domain/named.root
sudo mv -v root.hints /var/lib/unbound/

## 3. Configure unbound
# Highlights:
#   - Listen only for queries from the local Pi-hole installation (on port 5335)
#   - Listen for both UDP and TCP requests
#   - Verify DNSSEC signatures, discarding BOGUS domains
#   - Apply a few security and privacy tricks
sudo bash -c 'cat << EOF > /etc/unbound/unbound.conf.d/pi-hole.conf
server:
    # If no logfile is specified, syslog is used
    # logfile: "/var/log/unbound/unbound.log"
    verbosity: 0

    interface: 127.0.0.1
    port: 5335
    do-ip4: yes
    do-udp: yes
    do-tcp: yes

    # May be set to yes if you have IPv6 connectivity
    do-ip6: no

    # You want to leave this to no unless you have *native* IPv6. With 6to4 and
    # Terredo tunnels your web browser should favor IPv4 for the same reasons
    prefer-ip6: no

    # Use this only when you downloaded the list of primary root servers!
    # If you use the default dns-root-data package, unbound will find it automatically
    root-hints: "/var/lib/unbound/root.hints"

    # Trust glue only if it is within the servers authority
    harden-glue: yes

    # Require DNSSEC data for trust-anchored zones, if such data is absent, the zone becomes BOGUS
    harden-dnssec-stripped: yes

    # Do not use Capitalization randomization as it known to cause DNSSEC issues sometimes
    # see https://discourse.pi-hole.net/t/unbound-stubby-or-dnscrypt-proxy/9378 for further details
    use-caps-for-id: no

    # Reduce EDNS reassembly buffer size.
    # IP fragmentation is unreliable on the Internet today, and can cause
    # transmission failures when large DNS messages are sent via UDP. Even
    # when fragmentation does work, it may not be secure; it is theoretically
    # possible to spoof parts of a fragmented DNS message, without easy
    # detection at the receiving end. Recently, there was an excellent study
    # >>> Defragmenting DNS - Determining the optimal maximum UDP response size for DNS <<<
    # by Axel Koolhaas, and Tjeerd Slokker (https://indico.dns-oarc.net/event/36/contributions/776/)
    # in collaboration with NLnet Labs explored DNS using real world data from the
    # the RIPE Atlas probes and the researchers suggested different values for
    # IPv4 and IPv6 and in different scenarios. They advise that servers should
    # be configured to limit DNS messages sent over UDP to a size that will not
    # trigger fragmentation on typical network links. DNS servers can switch
    # from UDP to TCP when a DNS response is too big to fit in this limited
    # buffer size. This value has also been suggested in DNS Flag Day 2020.
    edns-buffer-size: 1232

    # Perform prefetching of close to expired message cache entries
    # This only applies to domains that have been frequently queried
    prefetch: yes

    # One thread should be sufficient, can be increased on beefy machines. In reality for most users running on small networks or on a single machine, it should be unnecessary to seek performance enhancement by increasing num-threads above 1.
    num-threads: 1

    # Ensure kernel buffer is large enough to not lose messages in traffic spikes
    so-rcvbuf: 1m

    # Ensure privacy of local IP ranges
    private-address: 192.168.0.0/16
    private-address: 169.254.0.0/16
    private-address: 172.16.0.0/12
    private-address: 10.0.0.0/8
    private-address: fd00::/8
    private-address: fe80::/10
EOF'

sudo su -c "echo 'edns-packet-max=1232' > /etc/dnsmasq.d/99-edns.conf"

# 4. Set cron to update root hints file 
sudo bash -c 'cat << EOF > /etc/cron.weekly/unbound_root_hints.sh
#!/usr/bin/env bash

# A. Download current root hints file
wget -O root.hints https://www.internic.net/domain/named.root
sudo mv -v root.hints /var/lib/unbound/
sudo ls -lt /var/lib/unbound/root.hints

# B. Restart your local recursive server
sudo /etc/init.d/unbound restart
EOF'

# 5. Set execute permissions
sudo chmod +x /etc/cron.weekly/unbound_root_hints.sh

## 6. Setup logs
sudo mkdir -p /var/log/unbound
sudo touch /var/log/unbound/unbound.log
sudo chown unbound /var/log/unbound/unbound.log

## 7. Check unbound config 
sudo /usr/sbin/unbound-checkconf

## 8. Restart your local recursive server
sudo service unbound restart

## 9. Test that it's operational
dig pi-hole.net @127.0.0.1 -p 5335

## 10. Test DNSSEC validation using
dig fail01.dnssec.works @127.0.0.1 -p 5335
dig dnssec.works @127.0.0.1 -p 5335

## 11. Configure Pi-hole
## go to http://localhost:80/admin/settings.php?tab=dns
# Finally, configure Pi-hole to use your recursive DNS server by specifying 127.0.0.1#5335 as the Custom DNS (IPv4):