202 lines
8.2 KiB
Bash
Executable File
202 lines
8.2 KiB
Bash
Executable File
source setup/functions.sh # load our functions
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# Basic System Configuration
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# -------------------------
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# ### Add Mail-in-a-Box's PPA.
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# We've built several .deb packages on our own that we want to include.
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# One is a replacement for Ubuntu's stock postgrey package that makes
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# some enhancements. The other is dovecot-lucene, a Lucene-based full
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# text search plugin for (and by) dovecot, which is not available in
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# Ubuntu currently.
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#
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# Add that to the system's list of repositories using add-apt-repository.
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# But add-apt-repository may not be installed. If it's not available,
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# then install it. But we have to run apt-get update before we try to
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# install anything so the package index is up to date. After adding the
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# PPA, we have to run apt-get update *again* to load the PPA's index,
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# so this must precede the apt-get update line below.
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if [ ! -f /usr/bin/add-apt-repository ]; then
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echo "Installing add-apt-repository..."
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hide_output apt-get update
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apt_install software-properties-common
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fi
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hide_output add-apt-repository -y ppa:mail-in-a-box/ppa
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# ### Update Packages
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# Update system packages to make sure we have the latest upstream versions of things from Ubuntu.
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echo Updating system packages...
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hide_output apt-get update
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apt_get_quiet upgrade
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# ### Install System Packages
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# Install basic utilities.
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#
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# * haveged: Provides extra entropy to /dev/random so it doesn't stall
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# when generating random numbers for private keys (e.g. during
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# ldns-keygen).
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# * unattended-upgrades: Apt tool to install security updates automatically.
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# * cron: Runs background processes periodically.
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# * ntp: keeps the system time correct
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# * fail2ban: scans log files for repeated failed login attempts and blocks the remote IP at the firewall
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# * netcat-openbsd: `nc` command line networking tool
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# * git: we install some things directly from github
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# * sudo: allows privileged users to execute commands as root without being root
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# * coreutils: includes `nproc` tool to report number of processors, mktemp
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# * bc: allows us to do math to compute sane defaults
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echo Installing system packages...
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apt_install python3 python3-dev python3-pip \
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netcat-openbsd wget curl git sudo coreutils bc \
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haveged pollinate \
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unattended-upgrades cron ntp fail2ban
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# ### Seed /dev/urandom
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#
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# /dev/urandom is used by various components for generating random bytes for
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# encryption keys and passwords:
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#
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# * TLS private key (see `ssl.sh`, which calls `openssl genrsa`)
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# * our management server's API key (via Python's os.urandom method)
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#
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# Why /dev/urandom? It's the same as /dev/random, except that it doesn't wait
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# for a constant new stream of entropy. In practice, we only need a little
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# entropy at the start to get going. After that, we can safely pull a random
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# stream from /dev/urandom and not worry about how much entropy has been
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# added to the stream. (http://www.2uo.de/myths-about-urandom/) So we need
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# to worry about /dev/urandom being seeded properly (which is also an issue
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# for /dev/random), but after that /dev/urandom is superior to /dev/random
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# because it's faster and doesn't block indefinitely to wait for hardware
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# entropy. Note that `openssl genrsa` even uses `/dev/urandom`, and if it's
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# good enough for generating an RSA private key, it's good enough for anything
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# else we may need.
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#
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# Now about that seeding issue....
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#
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# /dev/urandom is seeded from "the uninitialized contents of the pool buffers when
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# the kernel starts, the startup clock time in nanosecond resolution,...and
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# entropy saved across boots to a local file" as well as the order of
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# execution of concurrent accesses to /dev/urandom. (Heninger et al 2012,
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# https://factorable.net/weakkeys12.conference.pdf) But when memory is zeroed,
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# the system clock is reset on boot, /etc/init.d/urandom has not yet run, or
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# the machine is single CPU or has no concurrent accesses to /dev/urandom prior
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# to this point, /dev/urandom may not be seeded well. After this, /dev/urandom
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# draws from the same entropy sources as /dev/random, but it doesn't block or
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# issue any warnings if no entropy is actually available. (http://www.2uo.de/myths-about-urandom/)
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# Entropy might not be readily available because this machine has no user input
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# devices (common on servers!) and either no hard disk or not enough IO has
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# ocurred yet --- although haveged tries to mitigate this. So there's a good chance
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# that accessing /dev/urandom will not be drawing from any hardware entropy and under
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# a perfect-storm circumstance where the other seeds are meaningless, /dev/urandom
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# may not be seeded at all.
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#
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# The first thing we'll do is block until we can seed /dev/urandom with enough
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# hardware entropy to get going, by drawing from /dev/random. haveged makes this
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# less likely to stall for very long.
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echo Initializing system random number generator...
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dd if=/dev/random of=/dev/urandom bs=1 count=32 2> /dev/null
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# This is supposedly sufficient. But because we're not sure if hardware entropy
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# is really any good on virtualized systems, we'll also seed from Ubuntu's
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# pollinate servers:
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pollinate -q -r
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# Between these two, we really ought to be all set.
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# ### Package maintenance
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#
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# Allow apt to install system updates automatically every day.
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cat > /etc/apt/apt.conf.d/02periodic <<EOF;
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APT::Periodic::MaxAge "7";
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APT::Periodic::Update-Package-Lists "1";
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APT::Periodic::Unattended-Upgrade "1";
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APT::Periodic::Verbose "1";
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EOF
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# ### Firewall
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# Various virtualized environments like Docker and some VPSs don't provide #NODOC
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# a kernel that supports iptables. To avoid error-like output in these cases, #NODOC
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# we skip this if the user sets DISABLE_FIREWALL=1. #NODOC
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if [ -z "$DISABLE_FIREWALL" ]; then
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# Install `ufw` which provides a simple firewall configuration.
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apt_install ufw
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# Allow incoming connections to SSH.
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ufw_allow ssh;
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# ssh might be running on an alternate port. Use sshd -T to dump sshd's #NODOC
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# settings, find the port it is supposedly running on, and open that port #NODOC
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# too. #NODOC
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SSH_PORT=$(sshd -T 2>/dev/null | grep "^port " | sed "s/port //") #NODOC
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if [ ! -z "$SSH_PORT" ]; then
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if [ "$SSH_PORT" != "22" ]; then
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echo Opening alternate SSH port $SSH_PORT. #NODOC
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ufw_allow $SSH_PORT #NODOC
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fi
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fi
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ufw --force enable;
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fi #NODOC
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# ### Local DNS Service
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# Install a local DNS server, rather than using the DNS server provided by the
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# ISP's network configuration.
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#
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# We do this to ensure that DNS queries
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# that *we* make (i.e. looking up other external domains) perform DNSSEC checks.
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# We could use Google's Public DNS, but we don't want to create a dependency on
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# Google per our goals of decentralization. `bind9`, as packaged for Ubuntu, has
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# DNSSEC enabled by default via "dnssec-validation auto".
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#
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# So we'll be running `bind9` bound to 127.0.0.1 for locally-issued DNS queries
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# and `nsd` bound to the public ethernet interface for remote DNS queries asking
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# about our domain names. `nsd` is configured later.
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#
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# About the settings:
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#
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# * RESOLVCONF=yes will have `bind9` take over /etc/resolv.conf to tell
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# local services that DNS queries are handled on localhost.
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# * Adding -4 to OPTIONS will have `bind9` not listen on IPv6 addresses
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# so that we're sure there's no conflict with nsd, our public domain
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# name server, on IPV6.
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# * The listen-on directive in named.conf.options restricts `bind9` to
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# binding to the loopback interface instead of all interfaces.
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apt_install bind9 resolvconf
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tools/editconf.py /etc/default/bind9 \
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RESOLVCONF=yes \
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"OPTIONS=\"-u bind -4\""
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if ! grep -q "listen-on " /etc/bind/named.conf.options; then
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# Add a listen-on directive if it doesn't exist inside the options block.
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sed -i "s/^}/\n\tlisten-on { 127.0.0.1; };\n}/" /etc/bind/named.conf.options
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fi
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if [ -f /etc/resolvconf/resolv.conf.d/original ]; then
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echo "Archiving old resolv.conf (was /etc/resolvconf/resolv.conf.d/original, now /etc/resolvconf/resolv.conf.original)." #NODOC
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mv /etc/resolvconf/resolv.conf.d/original /etc/resolvconf/resolv.conf.original #NODOC
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fi
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# Restart the DNS services.
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restart_service bind9
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restart_service resolvconf
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# ### Fail2Ban Service
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# Configure the Fail2Ban installation to prevent dumb bruce-force attacks against dovecot, postfix and ssh
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cp conf/fail2ban/jail.local /etc/fail2ban/jail.local
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cp conf/fail2ban/dovecotimap.conf /etc/fail2ban/filter.d/dovecotimap.conf
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restart_service fail2ban
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