mailinabox/setup/dns.sh

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#!/bin/bash
# DNS: Configure a DNS server using nsd
#######################################
# This script installs packages, but the DNS zone files are only
# created by the /dns/update API in the management server because
# the set of zones (domains) hosted by the server depends on the
# mail users & aliases created by the user later.
source setup/functions.sh # load our functions
# Install nsd, our DNS server software, and ldnsutils which helps
# us sign zones for DNSSEC.
# ...but first, we have to create the user because the
# current Ubuntu forgets to do so in the .deb
# see issue #25 and https://bugs.launchpad.net/ubuntu/+source/nsd/+bug/1311886
if id nsd > /dev/null 2>&1; then
true; #echo "nsd user exists... good";
else
useradd nsd;
fi
# Okay now install the packages.
#
# nsd: The non-recursive nameserver that publishes our DNS records.
# ldnsutils: Helper utilities for signing DNSSEC zones.
# openssh-client: Provides ssh-keyscan which we use to create SSHFP records.
apt_install nsd ldnsutils openssh-client
# Prepare nsd's configuration.
sudo mkdir -p /var/run/nsd
# Create DNSSEC signing keys.
mkdir -p "$STORAGE_ROOT/dns/dnssec";
if [ ! -f "$STORAGE_ROOT/dns/dnssec/keys.conf" ]; then
echo "Generating DNSSEC signing keys. This may take a few minutes..."
# Create the Key-Signing Key (KSK) (-k) which is the so-called
# Secure Entry Point. Use a NSEC3-compatible algorithm (best
# practice), and a nice and long keylength. The domain name we
# provide ("_domain_") doesn't matter -- we'll use the same
# keys for all our domains.
KSK=$(umask 077; cd $STORAGE_ROOT/dns/dnssec; ldns-keygen -a RSASHA1-NSEC3-SHA1 -b 2048 -k _domain_);
# Now create a Zone-Signing Key (ZSK) which is expected to be
# rotated more often than a KSK, although we have no plans to
# rotate it (and doing so would be difficult to do without
# disturbing DNS availability.) Omit '-k' and use a shorter key.
ZSK=$(umask 077; cd $STORAGE_ROOT/dns/dnssec; ldns-keygen -a RSASHA1-NSEC3-SHA1 -b 1024 _domain_);
# These generate two sets of files like:
# K_domain_.+007+08882.ds <- DS record for adding to NSD configuration files
# K_domain_.+007+08882.key <- public key (goes into DS record & upstream DNS provider like your registrar)
# K_domain_.+007+08882.private <- private key (secret!)
# The filenames are unpredictable and encode the key generation
# options. So we'll store the names of the files we just generated.
# We might have multiple keys down the road. This will identify
# what keys are the current keys.
cat > $STORAGE_ROOT/dns/dnssec/keys.conf << EOF;
KSK=$KSK
ZSK=$ZSK
EOF
fi
# Force the dns_update script to be run every day to re-sign zones for DNSSEC.
cat > /etc/cron.daily/mailinabox-dnssec << EOF;
#!/bin/bash
# Mail-in-a-Box
# Re-sign any DNS zones with DNSSEC because the signatures expire periodically.
`pwd`/tools/dns_update
EOF
chmod +x /etc/cron.daily/mailinabox-dnssec
# Permit DNS queries on TCP/UDP in the firewall.
ufw_allow domain