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update bind9 configuration

This commit is contained in:
Joshua Tauberer 2018-10-03 14:28:43 -04:00
parent bc4bdca752
commit 3dbd6c994a
3 changed files with 44 additions and 20 deletions
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0
management/munin_start.sh Normal file → Executable file
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2
setup/mail-postfix.sh
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@ -146,7 +146,7 @@ tools/editconf.py /etc/postfix/main.cf \
# then opportunistic TLS is used. Otherwise the server certificate must match the TLSA records
# or else the mail bounces. TLSA also requires DNSSEC on the MX host. Postfix doesn't do DNSSEC
# itself but assumes the system's nameserver does and reports DNSSEC status. Thus this also
# relies on our local bind9 server being present and `smtp_dns_support_level=dnssec`.
# relies on our local DNS server (see system.sh) and `smtp_dns_support_level=dnssec`.
#
# The `smtp_tls_CAfile` is superflous, but it eliminates warnings in the logs about untrusted certs,
# which we don't care about seeing because Postfix is doing opportunistic TLS anyway. Better to encrypt,

62
setup/system.sh
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@ -264,45 +264,69 @@ fi #NODOC
# ### Local DNS Service
# Install a local DNS server, rather than using the DNS server provided by the
# ISP's network configuration.
# Install a local recursive DNS server --- i.e. for DNS queries made by
# local services running on this machine.
#
# 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".
# (This is unrelated to the box's public, non-recursive DNS server that
# answers remote queries about domain names hosted on this box. For that
# see dns.sh.)
#
# 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 later.
# The default systemd-resolved service provides local DNS name resolution. By default it
# is a recursive stub nameserver, which means it simply relays requests to an
# external nameserver, usually provided by your ISP or configured in /etc/systemd/resolved.conf.
#
# This won't work for us for three reasons.
#
# 1) We have higher security goals --- we want DNSSEC to be enforced on all
# DNS queries (some upstream DNS servers do, some don't).
# 2) We will configure postfix to use DANE, which uses DNSSEC to find TLS
# certificates for remote servers. DNSSEC validation *must* be performed
# locally because we can't trust an unencrypted connection to an external
# DNS server.
# 3) DNS-based mail server blacklists (RBLs) typically block large ISP
# DNS servers because they only provide free data to small users. Since
# we use RBLs to block incoming mail from blacklisted IP addresses,
# we have to run our own DNS server. See #1424.
#
# systemd-resolved has a setting to perform local DNSSEC validation on all
# requests (in /etc/systemd/resolved.conf, set DNSSEC=yes), but because it's
# a stub server the main part of a request still goes through an upstream
# DNS server, which won't work for RBLs. So we really need a local recursive
# nameserver.
#
# We'll install `bind9`, which as packaged for Ubuntu, has DNSSEC enabled by default via "dnssec-validation auto".
# We'll have it be bound to 127.0.0.1 so that it does not interfere with
# the public, recursive nameserver `nsd` bound to the public ethernet interfaces.
#
# 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 resolvconf
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
if [ -f /etc/resolvconf/resolv.conf.d/original ]; then
echo "Archiving old resolv.conf (was /etc/resolvconf/resolv.conf.d/original, now /etc/resolvconf/resolv.conf.original)." #NODOC
mv /etc/resolvconf/resolv.conf.d/original /etc/resolvconf/resolv.conf.original #NODOC
fi
# First we'll disable systemd-resolved's management of resolv.conf and its stub server.
# Breaking the symlink to /run/systemd/resolve/stub-resolv.conf means
# systemd-resolved will read it for DNS servers to use. Put in 127.0.0.1,
# which is where bind9 will be running. Obviously don't do this before
# installing bind9 or else apt won't be able to resolve a server to
# download bind9 from.
rm -f /etc/resolv.conf
tools/editconf.py /etc/systemd/resolved.conf DNSStubListener=no
echo "127.0.0.1" > /etc/resolv.conf
# Restart the DNS services.
restart_service bind9
restart_service resolvconf
systemctl restart systemd-resolved
# ### Fail2Ban Service