mailinabox/setup/system.sh

source setup/functions.sh # load our functions

# Base system configuration.

apt-get -qq update
apt-get -qq -y upgrade

# Install basic utilities.

apt_install python3 python3-pip wget curl bind9-host

# Turn on basic services:
#
#   ntp: keeps the system time correct
#
#   fail2ban: scans log files for repeated failed login attempts and blocks the remote IP at the firewall
#
# These services don't need further configuration and are started immediately after installation.

apt_install ntp fail2ban

if [ -z "$DISABLE_FIREWALL" ]; then
	# Turn on the firewall. First allow incoming SSH, then turn on the firewall.
	# Other ports will be opened at the point where we set up those services.
	#
	# Various virtualized environments like Docker and some VPSs don't provide
	# a kernel that supports iptables. To avoid error-like output in these cases,
	# let us disable the firewall.
	apt_install ufw
	ufw_allow ssh;
	ufw --force enable;
fi

# Resolve DNS using bind9 locally, rather than whatever DNS server is supplied
# by the machine's network configuration. We do this to ensure that DNS queries
# that *we* make (i.e. looking up other external domains) perform DNSSEC checks.
# We could use Google's Public DNS, but we don't want to create a dependency on
# Google per our goals of decentralization. bind9, as packaged for Ubuntu, has
# DNSSEC enabled by default via "dnssec-validation auto".
#
# So we'll be running bind9 bound to 127.0.0.1 for locally-issued DNS queries
# and nsd bound to the public ethernet interface for remote DNS queries asking
# about our domain names. nsd is configured in dns.sh.
#
# About the settings:
#
# * RESOLVCONF=yes will have bind9 take over /etc/resolv.conf to tell
#   local services that DNS queries are handled on localhost.
# * Adding -4 to OPTIONS will have bind9 not listen on IPv6 addresses
#   so that we're sure there's no conflict with nsd, our public domain
#   name server, on IPV6.
# * The listen-on directive in named.conf.options restricts bind9 to
#   binding to the loopback interface instead of all interfaces.
apt_install bind9
tools/editconf.py /etc/default/bind9 \
	RESOLVCONF=yes \
	"OPTIONS=\"-u bind -4\""
if ! grep -q "listen-on " /etc/bind/named.conf.options; then
	# Add a listen-on directive if it doesn't exist inside the options block.
	sed -i "s/^}/\n\tlisten-on { 127.0.0.1; };\n}/" /etc/bind/named.conf.options
fi

service bind9 restart