source /etc/mailinabox.conf source setup/functions.sh # load our functions # Basic System Configuration # ------------------------- # ### Set hostname of the box # If the hostname is not correctly resolvable sudo can't be used. This will result in # errors during the install # # First set the hostname in the configuration file, then activate the setting echo $PRIMARY_HOSTNAME > /etc/hostname hostname $PRIMARY_HOSTNAME # ### Enable IPv6 at Kernel Level # This doesn't mean that the cloud provider must provide IPv6 connectivity. We just want # the loopback interface to also work on IPv6 (that is, we want :: to be available). This # is required because apparently nsd expects this to exist. management/editconf.py /etc/sysctl.conf "net.ipv6.conf.lo.disable_ipv6 = 0" hide_output sysctl --system # ### Fix permissions # The default Ubuntu Bionic image on Scaleway throws warnings during setup about incorrect # permissions (group writeable) set on the following directories. chmod g-w /etc /etc/default /usr # ### Add swap space to the system # If the physical memory of the system is below 2GB it is wise to create a # swap file. This will make the system more resiliant to memory spikes and # prevent for instance spam filtering from crashing # We will create a 1G file, this should be a good balance between disk usage # and buffers for the system. We will only allocate this file if there is more # than 5GB of disk space available # The following checks are performed: # - Check if swap is currently mountend by looking at /proc/swaps # - Check if the user intents to activate swap on next boot by checking fstab entries. # - Check if a swapfile already exists # - Check if the root file system is not btrfs, might be an incompatible version with # swapfiles. User should hanle it them selves. # - Check the memory requirements # - Check available diskspace # See https://www.digitalocean.com/community/tutorials/how-to-add-swap-on-ubuntu-14-04 # for reference SWAP_MOUNTED=$(cat /proc/swaps | tail -n+2) SWAP_IN_FSTAB=$(grep "swap" /etc/fstab || /bin/true) ROOT_IS_BTRFS=$(grep "\/ .*btrfs" /proc/mounts || /bin/true) TOTAL_PHYSICAL_MEM=$(head -n 1 /proc/meminfo | awk '{print $2}' || /bin/true) AVAILABLE_DISK_SPACE=$(df / --output=avail | tail -n 1) if [ -z "$SWAP_MOUNTED" ] && [ -z "$SWAP_IN_FSTAB" ] && [ ! -e /swapfile ] && [ -z "$ROOT_IS_BTRFS" ] && [ $TOTAL_PHYSICAL_MEM -lt 1900000 ] && [ $AVAILABLE_DISK_SPACE -gt 5242880 ] then echo "Adding a swap file to the system..." # Allocate and activate the swap file. Allocate in 1KB chuncks # doing it in one go, could fail on low memory systems dd if=/dev/zero of=/swapfile bs=1024 count=$[1024*1024] status=none if [ -e /swapfile ]; then chmod 600 /swapfile hide_output mkswap /swapfile swapon /swapfile fi # Check if swap is mounted then activate on boot if swapon -s | grep -q "\/swapfile"; then echo "/swapfile none swap sw 0 0" >> /etc/fstab else echo "ERROR: Swap allocation failed" fi fi # ### Set log retention policy. # Set the systemd journal log retention from infinite to 10 days, # since over time the logs take up a large amount of space. # (See https://discourse.mailinabox.email/t/journalctl-reclaim-space-on-small-mailinabox/6728/11.) management/editconf.py /etc/systemd/journald.conf MaxRetentionSec=10day # ### Update Packages # Update system packages to make sure we have the latest upstream versions # of things from Ubuntu, as well as the directory of packages provide by the # PPAs so we can install those packages later. echo Updating system packages... hide_output apt-get update apt_get_quiet upgrade # Old kernels pile up over time and take up a lot of disk space, and because of Mail-in-a-Box # changes there may be other packages that are no longer needed. Clear out anything apt knows # is safe to delete. apt_get_quiet autoremove # ### Install System Packages # Install basic utilities. # # * unattended-upgrades: Apt tool to install security updates automatically. # * cron: Runs background processes periodically. # * ntp: keeps the system time correct # * fail2ban: scans log files for repeated failed login attempts and blocks the remote IP at the firewall # * netcat-openbsd: `nc` command line networking tool # * git: we install some things directly from github # * sudo: allows privileged users to execute commands as root without being root # * coreutils: includes `nproc` tool to report number of processors, mktemp # * bc: allows us to do math to compute sane defaults # * openssh-client: provides ssh-keygen echo Installing system packages... apt_install python3 python3-dev python3-pip python3-setuptools \ netcat-openbsd wget curl git sudo coreutils bc file \ pollinate openssh-client unzip \ unattended-upgrades cron ntp fail2ban rsyslog # ### Suppress Upgrade Prompts # When Ubuntu 20 comes out, we don't want users to be prompted to upgrade, # because we don't yet support it. if [ -f /etc/update-manager/release-upgrades ]; then management/editconf.py /etc/update-manager/release-upgrades Prompt=never rm -f /var/lib/ubuntu-release-upgrader/release-upgrade-available fi # ### Set the system timezone # # Some systems are missing /etc/timezone, which we cat into the configs for # Z-Push and ownCloud, so we need to set it to something. Daily cron tasks # like the system backup are run at a time tied to the system timezone, so # letting the user choose will help us identify the right time to do those # things (i.e. late at night in whatever timezone the user actually lives # in). # # However, changing the timezone once it is set seems to confuse fail2ban # and requires restarting fail2ban (done below in the fail2ban # section) and syslog (see #328). There might be other issues, and it's # not likely the user will want to change this, so we only ask on first # setup. if [ -z "${NONINTERACTIVE:-}" ]; then if [ ! -f /etc/timezone ] || [ ! -z ${FIRST_TIME_SETUP:-} ]; then # If the file is missing or this is the user's first time running # Mail-in-a-Box setup, run the interactive timezone configuration # tool. dpkg-reconfigure tzdata restart_service rsyslog fi else # This is a non-interactive setup so we can't ask the user. # If /etc/timezone is missing, set it to UTC. if [ ! -f /etc/timezone ]; then echo "Setting timezone to UTC." echo "Etc/UTC" > /etc/timezone restart_service rsyslog fi fi # ### Seed /dev/urandom # # /dev/urandom is used by various components for generating random bytes for # encryption keys and passwords: # # * TLS private key (see `ssl.sh`, which calls `openssl genrsa`) # * DNSSEC signing keys (see `dns.sh`) # * our management server's API key (via Python's os.urandom method) # * Roundcube's SECRET_KEY (`webmail.sh`) # # Why /dev/urandom? It's the same as /dev/random, except that it doesn't wait # for a constant new stream of entropy. In practice, we only need a little # entropy at the start to get going. After that, we can safely pull a random # stream from /dev/urandom and not worry about how much entropy has been # added to the stream. (http://www.2uo.de/myths-about-urandom/) So we need # to worry about /dev/urandom being seeded properly (which is also an issue # for /dev/random), but after that /dev/urandom is superior to /dev/random # because it's faster and doesn't block indefinitely to wait for hardware # entropy. Note that `openssl genrsa` even uses `/dev/urandom`, and if it's # good enough for generating an RSA private key, it's good enough for anything # else we may need. # # Now about that seeding issue.... # # /dev/urandom is seeded from "the uninitialized contents of the pool buffers when # the kernel starts, the startup clock time in nanosecond resolution,...and # entropy saved across boots to a local file" as well as the order of # execution of concurrent accesses to /dev/urandom. (Heninger et al 2012, # https://factorable.net/weakkeys12.conference.pdf) But when memory is zeroed, # the system clock is reset on boot, /etc/init.d/urandom has not yet run, or # the machine is single CPU or has no concurrent accesses to /dev/urandom prior # to this point, /dev/urandom may not be seeded well. After this, /dev/urandom # draws from the same entropy sources as /dev/random, but it doesn't block or # issue any warnings if no entropy is actually available. (http://www.2uo.de/myths-about-urandom/) # Entropy might not be readily available because this machine has no user input # devices (common on servers!) and either no hard disk or not enough IO has # ocurred yet --- although haveged tries to mitigate this. So there's a good chance # that accessing /dev/urandom will not be drawing from any hardware entropy and under # a perfect-storm circumstance where the other seeds are meaningless, /dev/urandom # may not be seeded at all. # # The first thing we'll do is block until we can seed /dev/urandom with enough # hardware entropy to get going, by drawing from /dev/random. haveged makes this # less likely to stall for very long. echo Initializing system random number generator... dd if=/dev/random of=/dev/urandom bs=1 count=32 2> /dev/null # This is supposedly sufficient. But because we're not sure if hardware entropy # is really any good on virtualized systems, we'll also seed from Ubuntu's # pollinate servers: if ! pollinate -q -r --strict 2> /dev/null; then # In the case pollinate is ill-configured (e.g. server is example.com), try using a server we know that works # Even if this fails - don't bail and carry on. pollinate -q -r -s entropy.ubuntu.com 2> /dev/null fi # Between these two, we really ought to be all set. # We need an ssh key to store backups via rsync, if it doesn't exist create one if [ ! -f /root/.ssh/id_rsa_miab ]; then echo 'Creating SSH key for backup…' ssh-keygen -t rsa -b 2048 -a 100 -f /root/.ssh/id_rsa_miab -N '' -q fi # ### Package maintenance # # Allow apt to install system updates automatically every day. cat > /etc/apt/apt.conf.d/02periodic </dev/null | grep "^port " | sed "s/port //") #NODOC if [ ! -z "$SSH_PORT" ]; then if [ "$SSH_PORT" != "22" ]; then echo Opening alternate SSH port $SSH_PORT. #NODOC ufw_limit $SSH_PORT #NODOC fi fi fi ufw --force enable; fi #NODOC # ### Local DNS Service # Install a local recursive DNS server --- i.e. for DNS queries made by # local services running on this machine. # # (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.) # # 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: # # * 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. # * The max-recursion-queries directive increases the maximum number of iterative queries. # If more queries than specified are sent, bind9 returns SERVFAIL. After flushing the cache during system checks, # we ran into the limit thus we are increasing it from 75 (default value) to 100. apt_install bind9 touch /etc/default/bind9 touch /etc/default/named management/editconf.py /etc/default/bind9 \ "OPTIONS=\"-u bind -4\"" management/editconf.py /etc/default/named \ "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 ! grep -q "max-recursion-queries " /etc/bind/named.conf.options; then # Add a max-recursion-queries directive if it doesn't exist inside the options block. sed -i "s/^}/\n\tmax-recursion-queries 100;\n}/" /etc/bind/named.conf.options 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 management/editconf.py /etc/systemd/resolved.conf DNSStubListener=no echo "nameserver 127.0.0.1" > /etc/resolv.conf # Restart the DNS services. restart_service bind9 systemctl restart systemd-resolved # ### Fail2Ban Service # Configure the Fail2Ban installation to prevent dumb bruce-force attacks against dovecot, postfix, ssh, etc. rm -f /etc/fail2ban/jail.local # we used to use this file but don't anymore rm -f /etc/fail2ban/jail.d/defaults-debian.conf # removes default config so we can manage all of fail2ban rules in one config cat conf/fail2ban/jails.conf \ | sed "s/PUBLIC_IPV6/$PUBLIC_IPV6/g" \ | sed "s/PUBLIC_IP/$PUBLIC_IP/g" \ | sed "s#STORAGE_ROOT#$STORAGE_ROOT#" \ > /etc/fail2ban/jail.d/mailinabox.conf cp -f conf/fail2ban/filter.d/* /etc/fail2ban/filter.d/ # On first installation, the log files that the jails look at don't all exist. # e.g., The roundcube error log isn't normally created until someone logs into # Roundcube for the first time. This causes fail2ban to fail to start. Later # scripts will ensure the files exist and then fail2ban is given another # restart at the very end of setup. restart_service fail2ban