374 lines
16 KiB
Bash
Executable file
374 lines
16 KiB
Bash
Executable file
source /etc/mailinabox.conf
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source setup/functions.sh # load our functions
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# Basic System Configuration
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# -------------------------
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# ### Set hostname of the box
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# If the hostname is not correctly resolvable sudo can't be used. This will result in
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# errors during the install
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#
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# First set the hostname in the configuration file, then activate the setting
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echo $PRIMARY_HOSTNAME > /etc/hostname
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hostname $PRIMARY_HOSTNAME
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# ### Enable IPv6 at Kernel Level
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# This doesn't mean that the cloud provider must provide IPv6 connectivity. We just want
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# the loopback interface to also work on IPv6 (that is, we want :: to be available). This
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# is required because apparently nsd expects this to exist.
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management/editconf.py /etc/sysctl.conf "net.ipv6.conf.lo.disable_ipv6 = 0"
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hide_output sysctl --system
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# ### Fix permissions
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# The default Ubuntu Bionic image on Scaleway throws warnings during setup about incorrect
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# permissions (group writeable) set on the following directories.
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chmod g-w /etc /etc/default /usr
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# ### Add swap space to the system
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# If the physical memory of the system is below 2GB it is wise to create a
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# swap file. This will make the system more resiliant to memory spikes and
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# prevent for instance spam filtering from crashing
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# We will create a 1G file, this should be a good balance between disk usage
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# and buffers for the system. We will only allocate this file if there is more
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# than 5GB of disk space available
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# The following checks are performed:
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# - Check if swap is currently mountend by looking at /proc/swaps
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# - Check if the user intents to activate swap on next boot by checking fstab entries.
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# - Check if a swapfile already exists
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# - Check if the root file system is not btrfs, might be an incompatible version with
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# swapfiles. User should hanle it them selves.
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# - Check the memory requirements
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# - Check available diskspace
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# See https://www.digitalocean.com/community/tutorials/how-to-add-swap-on-ubuntu-14-04
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# for reference
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SWAP_MOUNTED=$(cat /proc/swaps | tail -n+2)
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SWAP_IN_FSTAB=$(grep "swap" /etc/fstab || /bin/true)
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ROOT_IS_BTRFS=$(grep "\/ .*btrfs" /proc/mounts || /bin/true)
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TOTAL_PHYSICAL_MEM=$(head -n 1 /proc/meminfo | awk '{print $2}' || /bin/true)
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AVAILABLE_DISK_SPACE=$(df / --output=avail | tail -n 1)
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if
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[ -z "$SWAP_MOUNTED" ] &&
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[ -z "$SWAP_IN_FSTAB" ] &&
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[ ! -e /swapfile ] &&
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[ -z "$ROOT_IS_BTRFS" ] &&
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[ $TOTAL_PHYSICAL_MEM -lt 1900000 ] &&
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[ $AVAILABLE_DISK_SPACE -gt 5242880 ]
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then
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echo "Adding a swap file to the system..."
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# Allocate and activate the swap file. Allocate in 1KB chuncks
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# doing it in one go, could fail on low memory systems
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dd if=/dev/zero of=/swapfile bs=1024 count=$[1024*1024] status=none
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if [ -e /swapfile ]; then
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chmod 600 /swapfile
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hide_output mkswap /swapfile
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swapon /swapfile
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fi
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# Check if swap is mounted then activate on boot
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if swapon -s | grep -q "\/swapfile"; then
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echo "/swapfile none swap sw 0 0" >> /etc/fstab
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else
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echo "ERROR: Swap allocation failed"
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fi
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fi
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# ### Set log retention policy.
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# Set the systemd journal log retention from infinite to 10 days,
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# since over time the logs take up a large amount of space.
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# (See https://discourse.mailinabox.email/t/journalctl-reclaim-space-on-small-mailinabox/6728/11.)
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management/editconf.py /etc/systemd/journald.conf MaxRetentionSec=10day
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# ### Update Packages
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# Update system packages to make sure we have the latest upstream versions
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# of things from Ubuntu, as well as the directory of packages provide by the
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# PPAs so we can install those packages later.
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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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# Old kernels pile up over time and take up a lot of disk space, and because of Mail-in-a-Box
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# changes there may be other packages that are no longer needed. Clear out anything apt knows
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# is safe to delete.
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apt_get_quiet autoremove
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# ### Install System Packages
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# Install basic utilities.
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#
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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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# * openssh-client: provides ssh-keygen
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echo Installing system packages...
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apt_install python3 python3-dev python3-pip python3-setuptools \
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netcat-openbsd wget curl git sudo coreutils bc file \
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pollinate openssh-client unzip \
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unattended-upgrades cron ntp fail2ban rsyslog
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# ### Suppress Upgrade Prompts
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# When Ubuntu 20 comes out, we don't want users to be prompted to upgrade,
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# because we don't yet support it.
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if [ -f /etc/update-manager/release-upgrades ]; then
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management/editconf.py /etc/update-manager/release-upgrades Prompt=never
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rm -f /var/lib/ubuntu-release-upgrader/release-upgrade-available
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fi
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# ### Set the system timezone
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#
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# Some systems are missing /etc/timezone, which we cat into the configs for
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# Z-Push and ownCloud, so we need to set it to something. Daily cron tasks
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# like the system backup are run at a time tied to the system timezone, so
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# letting the user choose will help us identify the right time to do those
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# things (i.e. late at night in whatever timezone the user actually lives
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# in).
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#
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# However, changing the timezone once it is set seems to confuse fail2ban
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# and requires restarting fail2ban (done below in the fail2ban
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# section) and syslog (see #328). There might be other issues, and it's
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# not likely the user will want to change this, so we only ask on first
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# setup.
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if [ -z "${NONINTERACTIVE:-}" ]; then
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if [ ! -f /etc/timezone ] || [ ! -z ${FIRST_TIME_SETUP:-} ]; then
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# If the file is missing or this is the user's first time running
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# Mail-in-a-Box setup, run the interactive timezone configuration
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# tool.
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dpkg-reconfigure tzdata
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restart_service rsyslog
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fi
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else
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# This is a non-interactive setup so we can't ask the user.
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# If /etc/timezone is missing, set it to UTC.
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if [ ! -f /etc/timezone ]; then
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echo "Setting timezone to UTC."
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echo "Etc/UTC" > /etc/timezone
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restart_service rsyslog
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fi
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fi
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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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# * DNSSEC signing keys (see `dns.sh`)
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# * our management server's API key (via Python's os.urandom method)
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# * Roundcube's SECRET_KEY (`webmail.sh`)
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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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if ! pollinate -q -r --strict 2> /dev/null; then
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# In the case pollinate is ill-configured (e.g. server is example.com), try using a server we know that works
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# Even if this fails - don't bail and carry on.
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pollinate -q -r -s entropy.ubuntu.com 2> /dev/null
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fi
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# Between these two, we really ought to be all set.
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# We need an ssh key to store backups via rsync, if it doesn't exist create one
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if [ ! -f /root/.ssh/id_rsa_miab ]; then
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echo 'Creating SSH key for backup…'
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ssh-keygen -t rsa -b 2048 -a 100 -f /root/.ssh/id_rsa_miab -N '' -q
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fi
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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 "0";
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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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# Check if we have got an SSH server installed.
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# It's not critical for us to have one, so if it isn't installed,
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# no need to open the port
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if [ -x "$(command -v sshd)" ]; then
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# Allow incoming connections to SSH.
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ufw_limit ssh;
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# ssh might be running on an alternate port. Use sshd -T to dump sshd's #NODOC
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# settings, find the port it is supposedly running on, and open that port #NODOC
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# too. #NODOC
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SSH_PORT=$(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_limit $SSH_PORT #NODOC
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fi
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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 recursive DNS server --- i.e. for DNS queries made by
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# local services running on this machine.
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#
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# (This is unrelated to the box's public, non-recursive DNS server that
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# answers remote queries about domain names hosted on this box. For that
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# see dns.sh.)
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#
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# The default systemd-resolved service provides local DNS name resolution. By default it
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# is a recursive stub nameserver, which means it simply relays requests to an
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# external nameserver, usually provided by your ISP or configured in /etc/systemd/resolved.conf.
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#
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# This won't work for us for three reasons.
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#
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# 1) We have higher security goals --- we want DNSSEC to be enforced on all
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# DNS queries (some upstream DNS servers do, some don't).
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# 2) We will configure postfix to use DANE, which uses DNSSEC to find TLS
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# certificates for remote servers. DNSSEC validation *must* be performed
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# locally because we can't trust an unencrypted connection to an external
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# DNS server.
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# 3) DNS-based mail server blacklists (RBLs) typically block large ISP
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# DNS servers because they only provide free data to small users. Since
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# we use RBLs to block incoming mail from blacklisted IP addresses,
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# we have to run our own DNS server. See #1424.
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#
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# systemd-resolved has a setting to perform local DNSSEC validation on all
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# requests (in /etc/systemd/resolved.conf, set DNSSEC=yes), but because it's
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# a stub server the main part of a request still goes through an upstream
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# DNS server, which won't work for RBLs. So we really need a local recursive
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# nameserver.
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#
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# We'll install `bind9`, which as packaged for Ubuntu, has DNSSEC enabled by default via "dnssec-validation auto".
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# We'll have it be bound to 127.0.0.1 so that it does not interfere with
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# the public, recursive nameserver `nsd` bound to the public ethernet interfaces.
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#
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# About the settings:
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#
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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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# * The max-recursion-queries directive increases the maximum number of iterative queries.
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# If more queries than specified are sent, bind9 returns SERVFAIL. After flushing the cache during system checks,
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# we ran into the limit thus we are increasing it from 75 (default value) to 100.
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apt_install bind9
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touch /etc/default/bind9
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touch /etc/default/named
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management/editconf.py /etc/default/bind9 \
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"OPTIONS=\"-u bind -4\""
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management/editconf.py /etc/default/named \
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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 ! grep -q "max-recursion-queries " /etc/bind/named.conf.options; then
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# Add a max-recursion-queries directive if it doesn't exist inside the options block.
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sed -i "s/^}/\n\tmax-recursion-queries 100;\n}/" /etc/bind/named.conf.options
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fi
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# First we'll disable systemd-resolved's management of resolv.conf and its stub server.
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# Breaking the symlink to /run/systemd/resolve/stub-resolv.conf means
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# systemd-resolved will read it for DNS servers to use. Put in 127.0.0.1,
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# which is where bind9 will be running. Obviously don't do this before
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# installing bind9 or else apt won't be able to resolve a server to
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# download bind9 from.
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rm -f /etc/resolv.conf
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management/editconf.py /etc/systemd/resolved.conf DNSStubListener=no
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echo "nameserver 127.0.0.1" > /etc/resolv.conf
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# Restart the DNS services.
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restart_service bind9
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systemctl restart systemd-resolved
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# ### Fail2Ban Service
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# Configure the Fail2Ban installation to prevent dumb bruce-force attacks against dovecot, postfix, ssh, etc.
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rm -f /etc/fail2ban/jail.local # we used to use this file but don't anymore
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rm -f /etc/fail2ban/jail.d/defaults-debian.conf # removes default config so we can manage all of fail2ban rules in one config
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cat conf/fail2ban/jails.conf \
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| sed "s/PUBLIC_IPV6/$PUBLIC_IPV6/g" \
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| sed "s/PUBLIC_IP/$PUBLIC_IP/g" \
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| sed "s#STORAGE_ROOT#$STORAGE_ROOT#" \
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> /etc/fail2ban/jail.d/mailinabox.conf
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cp -f conf/fail2ban/filter.d/* /etc/fail2ban/filter.d/
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# On first installation, the log files that the jails look at don't all exist.
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# e.g., The roundcube error log isn't normally created until someone logs into
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# Roundcube for the first time. This causes fail2ban to fail to start. Later
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# scripts will ensure the files exist and then fail2ban is given another
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# restart at the very end of setup.
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restart_service fail2ban
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