Hardening Ubuntu. Systemd edition.

A quick way to make a Ubuntu server a bit more secure.

Use the newly installed and configured system as a reference, or golden, image. Use that image as a baseline installation media and ensure that any future installation comply with benchmarks and policies using a configuration management tool, e.g Ansible or Puppet.

Tested on Ubuntu 20.04 Focal Fossa and Ubuntu 22.04 Jammy Jellyfish.

If you’re just interested in the security focused systemd configuration, it’s available as a separate document.

If you’re interested in testing your host settings, you’ll find the instructions here.

Note	Read the code and do not run this script without first testing in a non-operational environment. The code is not idempotent, use the Ansible role in production environments instead.

Note	There is a SLSA artifact present under the slsa workflow for file checksum verification.

Packer template and Ansible playbook

A Packer template is available in the Packer directory.

An Ansible playbook is available in the konstruktoid/ansible-role-hardening repository.

Howto

Start the server installation.
Pick language and keyboard layout.
Select "Ubuntu Server (minimized)".
Configure network connections.
Partition the system, see below for recommendations.
Do not install the OpenSSH server, "Featured Server Snaps", or any other packages.
Finish the installation and reboot.
Log in.
If wanted, set a Grub2 password with grub-mkpasswd-pbkdf2. See https://help.ubuntu.com/community/Grub2/Passwords for more information.
Install necessary packages: sudo apt-get -y install git net-tools procps --no-install-recommends.
Download the script: git clone https://github.com/konstruktoid/hardening.git.
Change the configuration options in the ubuntu.cfg file. Make sure to update the CHANGEME variable otherwise the script will fail.
Run the script: sudo bash ubuntu.sh.
Reboot.

Recommended partitions and options

/boot (rw)
/home (rw,nosuid,nodev)
/var/log (rw,nosuid,nodev,noexec)
/var/log/audit (rw,nosuid,nodev,noexec)
/var/tmp (rw,nosuid,nodev,noexec)

Note that /tmp will be added automatically by the script.

Configuration options

FW_ADMIN='127.0.0.1' // (1)
SSH_GRPS='sudo' // (2)
SSH_PORT='22' // (3)
SYSCTL_CONF='./misc/sysctl.conf' // (4)
AUDITD_MODE='1' // (5)
AUDITD_RULES='./misc/audit-base.rules ./misc/audit-aggressive.rules ./misc/audit-docker.rules' // (6)
LOGROTATE_CONF='./misc/logrotate.conf' // (7)
NTPSERVERPOOL='0.ubuntu.pool.ntp.org 1.ubuntu.pool.ntp.org 2.ubuntu.pool.ntp.org 3.ubuntu.pool.ntp.org pool.ntp.org' // (8)
TIMEDATECTL='' // (9)
VERBOSE='N' // (10)
AUTOFILL='N' // (11)
ADMINEMAIL="root@localhost" // (12)
KEEP_SNAPD='Y' // (13)
CHANGEME='' // (14)

# Configuration files // (15)
ADDUSER='/etc/adduser.conf'
AUDITDCONF='/etc/audit/auditd.conf'
AUDITRULES='/etc/audit/rules.d/hardening.rules'
COMMONPASSWD='/etc/pam.d/common-password'
COMMONACCOUNT='/etc/pam.d/common-account'
COMMONAUTH='/etc/pam.d/common-auth'
COREDUMPCONF='/etc/systemd/coredump.conf'
DEFAULTGRUB='/etc/default/grub.d'
DISABLEFS='/etc/modprobe.d/disablefs.conf'
DISABLEMOD='/etc/modprobe.d/disablemod.conf'
DISABLENET='/etc/modprobe.d/disablenet.conf'
FAILLOCKCONF='/etc/security/faillock.conf'
JOURNALDCONF='/etc/systemd/journald.conf'
LIMITSCONF='/etc/security/limits.conf'
LOGINDCONF='/etc/systemd/logind.conf'
LOGINDEFS='/etc/login.defs'
LOGROTATE='/etc/logrotate.conf'
PAMLOGIN='/etc/pam.d/login'
PSADCONF='/etc/psad/psad.conf'
PSADDL='/etc/psad/auto_dl'
RESOLVEDCONF='/etc/systemd/resolved.conf'
RKHUNTERCONF='/etc/default/rkhunter'
RSYSLOGCONF='/etc/rsyslog.conf'
SECURITYACCESS='/etc/security/access.conf'
SSHFILE='/etc/ssh/ssh_config'
SSHDFILE='/etc/ssh/sshd_config'
SYSCTL='/etc/sysctl.conf'
SYSTEMCONF='/etc/systemd/system.conf'
TIMESYNCD='/etc/systemd/timesyncd.conf'
UFWDEFAULT='/etc/default/ufw'
USERADD='/etc/default/useradd'
USERCONF='/etc/systemd/user.conf'

The IP addresses that will be able to connect with SSH, separated by spaces.
Which group the users have to be member of in order to acess via SSH, separated by spaces.
Configure SSH port.
Stricter sysctl settings.
Auditd failure mode. 0=silent 1=printk 2=panic.
Auditd rules.
Logrotate settings.
NTP server pool.
Add a specific time zone or use the system default by leaving it empty.
If you want all the details or not.
Let the script guess the FW_ADMIN and SSH_GRPS settings.
Add a valid email address, so PSAD can send notifications.
If 'Y' then the snapd package will be held to prevent removal.
Add something just to verify that you actually glanced the code.
Default configuration file locations.

Functions

Function list in execution order

Note that all functions has the f_ prefix in the code.

`pre`

Sets apt flags and performs basic permission check.

The pre function is located in ./scripts/pre.

`kernel`

Sets /sys/module/nf_conntrack/parameters/hashsize to 1048576 if hashsize exists and is writable.

Sets /sys/kernel/security/lockdown to confidentiality if lockdown exists and is writable.

The kernel function is located in ./scripts/kernel.

`firewall`

Configures UFW if installed.

Allows connections from the adresses in $FW_ADMIN to the $SSH_PORT.

Sets logging and IPT_SYSCTL=/etc/sysctl.conf.

The firewall function is located in ./scripts/ufw.

`disablenet`

Disables the dccp, sctp, rds and tipc kernel modules.

The disablenet function is located in ./scripts/disablenet.

`disablefs`

Disables the cramfs freevxfs jffs2 ksmbd hfs hfsplus udf kernel modules.

The disablefs function is located in ./scripts/disablefs.

`disablemod`

Disables the bluetooth, bnep, btusb, cpia2, firewire-core, floppy, n_hdlc, net-pf-31, pcspkr, soundcore, thunderbolt, usb-midi, usb-storage, uvcvideo, v4l2_common kernel modules.

Note that disabling the usb-storage module will disable any usage of USB storage devices, if such devices are needed USBGuard should be configured accordingly.

The disablemod function is located in ./scripts/disablemod.

`systemdconf`

Sets CrashShell=no, DefaultLimitCORE=0, DefaultLimitNOFILE=1024, DefaultLimitNPROC=1024, DumpCore=no in $SYSTEMCONF and $USERCONF.

The systemdconf function is located in ./scripts/systemdconf.

`resolvedconf`

Sets DNS=$dnslist, DNSOverTLS=opportunistic, DNSSEC=allow-downgrade, FallbackDNS=1.0.0.1 in $RESOLVEDCONF, where $dnslist is an array with the nameservers present in /etc/resolv.conf.

The resolvedconf function is located in ./scripts/resolvedconf.

`logindconf`

Sets IdleAction=lock, IdleActionSec=15min, KillExcludeUsers=root, KillUserProcesses=1, RemoveIPC=yes in $LOGINDCONF.

The logindconf function is located in ./scripts/logindconf.

`journalctl`

Copies ./misc/logrotate.conf to $LOGROTATE.

Sets Compress=yes, ForwardToSyslog=yes, Storage=persistent in $JOURNALDCONF.

Sets $FileCreateMode 0600/ in $RSYSLOGCONF. if RSYSLOGCONF is writable.

The journalctl function is located in ./scripts/journalctl.

`timesyncd`

Sets NTP=${SERVERARRAY}, FallbackNTP=${FALLBACKARRAY}, RootDistanceMaxSec=1 in $TIMESYNCD where the arrays are up to four time servers with < 50ms latency.

The timesyncd function is located in ./scripts/timesyncd.

`fstab`

Configures the /boot and /home partitions with defaults,nosuid,nodev if they are available in /etc/fstab.

Configures the /var/log, /var/log/audit and /var/tmp partitions with defaults,nosuid,nodev,noexec if they are available in /etc/fstab.

Adds /run/shm tmpfs rw,noexec,nosuid,nodev, /dev/shm tmpfs rw,noexec,nosuid,nodev and /proc proc rw,nosuid,nodev,noexec,relatime,hidepid=2 to /etc/fstab if the partition isn’t present in /etc/fstab.

Removes any floppy drivers from /etc/fstab.

Copies ./config/tmp.mount[./config/tmp.mount] to /etc/systemd/system/tmp.mount, removes /tmp from /etc/fstab and enables the tmpfs /tmp mount instead.

The /proc hidepid option is described in https://www.kernel.org/doc/html/latest/filesystems/proc.html#mount-options.

The fstab function is located in ./scripts/fstab.

`prelink`

Reverts binaries and libraries to their original content before they were prelinked and uninstalls prelink.

The prelink function is located in ./scripts/prelink.

`aptget_configure`

Sets apt options Acquire::http::AllowRedirect "false";, APT::Get::AllowUnauthenticated "false";, APT::Periodic::AutocleanInterval "7";, APT::Install-Recommends "false";, APT::Get::AutomaticRemove "true";, APT::Install-Suggests "false";, Acquire::AllowDowngradeToInsecureRepositories "false";, Acquire::AllowInsecureRepositories "false";, APT::Sandbox::Seccomp "1";

See https://manpages.ubuntu.com/manpages/jammy/man5/apt.conf.5.html.

The aptget_configure function is located in ./scripts/aptget.

`aptget`

Upgrades installed packages.

The aptget function is located in ./scripts/aptget.

`hosts`

Sets sshd : ALL : ALLOW, ALL: LOCAL, 127.0.0.1 in /etc/hosts.allow and ALL: ALL in /etc/hosts.deny.

See https://manpages.ubuntu.com/manpages/jammy/man5/hosts_access.5.html for the format of host access control files.

The hosts function is located in ./scripts/hosts.

`issue`

Writes a notice regarding authorized use only to /etc/issue, /etc/issue.net and /etc/motd.

Removes the executable flag from every file in /etc/update-motd.d/.

The issue function is located in ./scripts/issue.

`sudo`

Restricts su access to members of the sudo group using pam_wheel.

Sets !pwfeedback, !visiblepw, logfile=/var/log/sudo.log, passwd_timeout=1, timestamp_timeout=5, use_pty sudo options.

The sudo function is located in ./scripts/sudo.

`logindefs`

Writes LOG_OK_LOGINS yes, UMASK 077, PASS_MIN_DAYS 1, PASS_MAX_DAYS 60, DEFAULT_HOME no, ENCRYPT_METHOD SHA512, USERGROUPS_ENAB no, SHA_CRYPT_MIN_ROUNDS 10000, SHA_CRYPT_MAX_ROUNDS 65536 to $LOGINDEFS

The logindefs function is located in ./scripts/logindefs.

`sysctl`

Copies ./misc/sysctl.conf to $SYSCTL.

For an explanation of the options set, see https://www.kernel.org/doc/html/latest/admin-guide/sysctl/.

The sysctl function is located in ./scripts/sysctl.

`limitsconf`

Sets hard maxlogins 10, hard core 0, soft nproc 512, hard nproc 1024 in $LIMITSCONF

The limitsconf function is located in ./scripts/limits.

`adduser`

Sets DIR_MODE=0750,DSHELL=/bin/false, and USERGROUPS=yes in $ADDUSER.

Sets INACTIVE=30 and SHELL=/bin/false in $USERADD.

The adduser function is located in ./scripts/adduser.

`rootaccess`

Writes +:root:127.0.0.1/' to $SECURITYACCESS and console to /etc/securetty.

Masks debug-shell.

The rootaccess function is located in ./scripts/rootaccess.

`package_install`

Installs acct, aide-common, cracklib-runtime, debsums, gnupg2, haveged, libpam-pwquality, libpam-tmpdir, needrestart, openssh-server, postfix, psad, rkhunter, sysstat, systemd-coredump, tcpd, update-notifier-common, vlock.

The package_install function is located in ./scripts/packages.

`psad`

Installs and configures PSAD

The psad function is located in ./scripts/psad.

`coredump`

Writes Storage=none and ProcessSizeMax=0 to $COREDUMPCONF.

The coredump function is located in ./scripts/coredump.

`usbguard`

Installs and configures USBGuard.

The usbguard function is located in ./scripts/usbguard.

`postfix`

Installs postfix and sets disable_vrfy_command=yes, inet_interfaces=loopback-only, smtpd_banner="\$myhostname, smtpd_client_restrictions=permit_mynetworks,reject using postconf.

The postfix function is located in ./scripts/postfix.

`apport`

Disables apport, ubuntu-report and popularity-contest.

The apport function is located in ./scripts/apport.

`motdnews`

Disables apt_news and motd-news.

The motdnews function is located in ./scripts/motdnews.

`rkhunter`

Sets CRON_DAILY_RUN="yes", APT_AUTOGEN="yes" in $RKHUNTERCONF.

The rkhunter function is located in ./scripts/rkhunter.

`sshconfig`

Sets HashKnownHosts yes, Ciphers [email protected],[email protected],aes256-ctr and MACs [email protected],[email protected],hmac-sha2-512,hmac-sha2-256 in $SSHFILE.

The sshconfig function is located in ./scripts/sshdconfig.

`sshdconfig`

Configures the OpenSSH daemon. The configuration changes will be placed in the directory defined by the Include option if present, otherwise $SSHDFILE will be modified.

By default /etc/ssh/sshd_config.d/hardening.conf will contain the following:

AcceptEnv LANG LC_*
AllowAgentForwarding no
AllowGroups sudo
AllowTcpForwarding no
Banner /etc/issue.net
Ciphers [email protected],[email protected],aes256-ctr
ClientAliveCountMax 3
ClientAliveInterval 200
Compression no
GSSAPIAuthentication no
HostbasedAuthentication no
IgnoreUserKnownHosts yes
KbdInteractiveAuthentication no
KerberosAuthentication no
KexAlgorithms [email protected],ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
LogLevel VERBOSE
LoginGraceTime 20
Macs [email protected],[email protected],hmac-sha2-512,hmac-sha2-256
MaxAuthTries 3
MaxSessions 3
MaxStartups 10:30:60
PasswordAuthentication no
PermitEmptyPasswords no
PermitRootLogin no
PermitUserEnvironment no
Port 22
PrintLastLog yes
PrintMotd no
RekeyLimit 512M 1h
StrictModes yes
TCPKeepAlive no
UseDNS no
UsePAM yes
X11Forwarding no

The sshdconfig function is located in ./scripts/sshdconfig.

`password`

Copies ./config/pwquality.conf[./config/pwquality.conf] to /etc/security/pwquality.conf,

Removes nullok from PAM $COMMONAUTH.

Configures faillock or pam_tally2 depending on which is installed.

Adds a password list to cracklib.

The password function is located in ./scripts/password.

`cron`

Disables atd and only allow root to use at or cron.

The cron function is located in ./scripts/cron.

`ctrlaltdel`

Masks ctrl-alt-del.target.

The ctrlaltdel function is located in ./scripts/ctraltdel.

`auditd`

Configures auditd.

See ./misc/audit-base.rules, ./misc/audit-aggressive.rules and ./misc/audit-docker.rules for the rules used.

The auditd function is located in ./scripts/auditd.

`aide`

Excludes /var/lib/lxcfs/cgroup and /var/lib/docker from AIDE.

The aide function is located in ./scripts/aide.

`rhosts`

Removes any existing hosts.equiv or .rhosts files.

The rhosts function is located in ./scripts/rhosts.

`users`

Removes the games, gnats, irc, list, news, sync, uucp users.

The users function is located in ./scripts/users.

`lockroot`

Locks root account

The lockroot function is located in ./scripts/lockroot.

`package_remove`

Removes the apport*, autofs, avahi*, beep, git, pastebinit, popularity-contest, rsh*, rsync, talk*, telnet*, tftp*, whoopsie, xinetd, yp-tools, ypbind packages.

The package_remove function is located in ./scripts/packages.

`suid`

Ensures the executables in ./misc/suid.list don’t have suid bits set.

The suid function is located in ./scripts/suid.

`restrictcompilers`

Changes mode to 0750 on any installed compilers.

The restrictcompilers function is located in ./scripts/compilers.

`umask`

Sets the default umask to 077

The umask function is located in ./scripts/umask.

`path`

Copies ./config/initpath.sh[./config/initpath.sh] to /etc/profile.d/initpath.sh and sets PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin for the root user and PATH=/usr/local/bin:/usr/sbin:/usr/bin:/bin:/snap/bin for everyone else.

The path function is located in ./scripts/path.

`aa_enforce`

Enforces available apparmor profiles.

The aa_enforce function is located in ./scripts/apparmor.

`aide_post`

Creates a new AIDE database.

The aide_post function is located in ./scripts/aide.

`aide_timer`

Copies a systemd AIDE check service and timer to /etc/systemd/system/.

The aide_timer function is located in ./scripts/aide.

`aptget_noexec`

Adds a DPkg::Pre-Invoke and DPkg::Post-Invoke to ensure package updates don’t fail on a noexec /tmp partition.

The aptget_noexec function is located in ./scripts/aptget.

`aptget_clean`

Runs apt-get clean and autoremove.

The aptget_clean function is located in ./scripts/aptget.

`systemddelta`

Runs systemd-delta if running in verbose mode.

The systemddelta function is located in ./scripts/systemddelta.

`post`

Ensures fwupdmgr and secureboot-db is installed and GRUB is updated.

The post function is located in ./scripts/post.

`checkreboot`

Checks if a reboot is required.

The checkreboot function is located in ./scripts/reboot.

Tests

There are approximately 760 Bats tests for most of the above settings available in the tests directory.

sudo apt-get -y install bats
git clone https://github.com/konstruktoid/hardening.git
cd hardening/tests/
sudo bats .

Test automation using Vagrant

Running bash ./runTests.sh will use Vagrant to run all above tests, Lynis and OpenSCAP with a CIS Ubuntu benchmark on all supported Ubuntu versions.

The script will generate a file named TESTRESULTS.adoc and CIS report in HTML-format.

Testing a host

Running bash ./runHostTests.sh, located in the tests directory, will generate a TESTRESULTS-<HOSTNAME>.adoc report.

Running bash ./runHostTestsCsv.sh, located in the tests directory, will generate a TESTRESULTS-<HOSTNAME>.csv report.

Contributing

Do you want to contribute? That’s great! Contributions are always welcome, no matter how large or small. If you found something odd, feel free to submit a new issue, improve the code by creating a pull request, or by sponsoring this project.

Logo by reallinfo.

Name		Name	Last commit message	Last commit date
Latest commit History 1,646 Commits
.github		.github
action-shellcheck		action-shellcheck
config		config
logo		logo
misc		misc
packer		packer
scripts		scripts
tests		tests
.gitattributes		.gitattributes
.gitignore		.gitignore
.pre-commit-config.yaml		.pre-commit-config.yaml
LICENSE		LICENSE
README.adoc		README.adoc
SECURITY.md		SECURITY.md
Vagrantfile		Vagrantfile
checkScore.sh		checkScore.sh
createPartitions.sh		createPartitions.sh
renovate.json		renovate.json
runTests.sh		runTests.sh
systemd.adoc		systemd.adoc
ubuntu.cfg		ubuntu.cfg
ubuntu.sh		ubuntu.sh

License

konstruktoid/hardening

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Hardening Ubuntu. Systemd edition.

Packer template and Ansible playbook

Howto

Recommended partitions and options

Configuration options

Functions

Function list in execution order

pre

kernel

firewall

disablenet

disablefs

disablemod

systemdconf

resolvedconf

logindconf

journalctl

timesyncd

fstab

prelink

aptget_configure

aptget

hosts

issue

sudo

logindefs

sysctl

limitsconf

adduser

rootaccess

package_install

psad

coredump

usbguard

postfix

apport

motdnews

rkhunter

sshconfig

sshdconfig

password

cron

ctrlaltdel

auditd

aide

rhosts

users

lockroot

package_remove

suid

restrictcompilers

umask

path

aa_enforce

aide_post

aide_timer

aptget_noexec

aptget_clean

systemddelta

post

checkreboot