linux-scripts/arch-hardening.sh

#!/bin/bash

# [STRG-1846] Disable drivers like firewire
sudo tee /etc/modprobe.d/firewire-disable.conf > /dev/null <<EOL
# Disable FireWire kernel modules to prevent unauthorized DMA access
blacklist firewire-core
install firewire-core /bin/false
# Optional additional modules to blacklist
blacklist firewire-ohci
blacklist firewire-sbp2
install firewire-ohci /bin/false
install firewire-sbp2 /bin/false
EOL

# [LOGG-2154] Ensure system log is configured to send logs to a remote log server
sudo pacman -S --noconfirm --needed syslog-ng
sudo systemctl enable --now syslog-ng@default.service

# [NETW-2706] Ensure DNSSEC validation is enabled
echo 'DNSSEC=yes' | sudo tee -a /etc/systemd/resolved.conf > /dev/null
sudo systemctl restart systemd-resolved

# [USB-3000] Ensure USBGUARD is installed and configured
sudo pacman -S --noconfirm --needed usbguard
sudo usbguard generate-policy | sudo tee /etc/usbguard/rules.conf > /dev/null
sudo sed -i 's/^PresentControllerPolicy=.*/PresentControllerPolicy=apply-policy/' /etc/usbguard/usbguard-daemon.conf
sudo systemctl enable --now usbguard

# [NETW-3032] Checking for ARP monitoring software
sudo pacman -S --noconfirm --needed arpwatch
# Find first non-loopback, non-virbr/vmbr interface and enable arpwatch on it
iface=$(ip -o link show | awk -F': ' '{print $2}' | sed 's/@.*$//' | grep -Ev '^(lo|virbr|vmbr)' | head -n1)
if [ -n "$iface" ]; then
    sudo systemctl enable --now "arpwatch@${iface}.service"
else
    echo "No suitable network interface found for arpwatch; service not enabled." >&2
fi

# [NETW-3200] Disable unused network protocols
sudo tee /etc/modprobe.d/network-protocols-disable.conf > /dev/null <<EOL
# Disable unnecessary network protocols to reduce attack surface
blacklist dccp
install dccp /bin/false

blacklist sctp
install sctp /bin/false

blacklist rds
install rds /bin/false

blacklist tipc
install tipc /bin/false
EOL

# [MALW-3276] Ensure rkhunter is installed
sudo pacman -S --noconfirm --needed rkhunter
sudo rkhunter --propupd
sudo tee /etc/rkhunter.conf > /dev/null <<EOL
# rkhunter configuration file

# Whitelist to avoid false positive
SCRIPTWHITELIST=/usr/bin/egrep
SCRIPTWHITELIST=/usr/bin/fgrep
SCRIPTWHITELIST=/usr/bin/ldd
SCRIPTWHITELIST=/usr/bin/vendor_perl/GET
EOL

# [MALW-3282] Ensure ClamAV is installed
sudo pacman -S --noconfirm --needed clamav
sudo freshclam
sudo systemctl enable --now clamav-freshclam
sleep 5
sudo systemctl enable --now clamav-daemon

# [FINT-4350] Install a file integrity tool
sudo pacman -S --noconfirm --needed aide
sudo aide --init
sudo mv /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
sudo systemctl enable --now aidecheck.timer

# [FIRE-45XX] Firewall configuration
# remove iptables if installed
if pacman -Qi iptables &> /dev/null; then
    sudo pacman -R --noconfirm iptables
fi
sudo pacman -S --noconfirm --needed nftables

sudo tee /etc/modprobe.d/ip_tables-disable.conf > /dev/null <<EOL
# Disable ip_tables to prevent conflicts with nftables
blacklist ip_tables
install ip_tables /bin/false
EOL

# [TOOL-5190] Ensure IDS/IPS tools are installed
sudo pacman -S --noconfirm --needed snort
sudo systemctl enable --now snort

# [KRNL-5820] Disable core dumps

# Disable coredump handling in systemd's coredump configuration and mask units
sudo mkdir -p /etc/systemd/coredump.conf.d
sudo tee /etc/systemd/coredump.conf.d/99-disable-coredumps.conf > /dev/null <<'EOL'
[Coredump]
# Prevent any core file data being stored and limit accepted size to 0
ProcessSizeMax=0
Storage=none
EOL
sudo systemctl daemon-reload

sudo mkdir -p /etc/security/limits.d/
sudo tee /etc/security/limits.d/20-disable-core-dumps.conf > /dev/null <<EOL
# Disable core dumps for ALL users
# The format is: <domain> <type> <item> <value>
* hard    core    0
* soft    core    0
EOL
# Append to /etc/profile to enforce core dump restriction system-wide
echo '# Disable core dumps system-wide' | sudo tee -a /etc/profile > /dev/null
echo 'ulimit -c 0 > /dev/null 2>&1' | sudo tee -a /etc/profile > /dev/null
echo '# Set the core dump soft limit to 0 (current enforceable limit)' | sudo tee -a /etc/profile > /dev/null
echo 'ulimit -S -c 0 > /dev/null 2>&1' | sudo tee -a /etc/profile > /dev/null
echo '# Set the hard limit to 0 (absolute maximum limit)' | sudo tee -a /etc/profile > /dev/null
echo 'ulimit -H -c 0 > /dev/null 2>&1' | sudo tee -a /etc/profile > /dev/null

# [KRNL-6000] Check sysctl settings for kernel hardening
sudo tee /etc/sysctl.d/99-hardened.conf > /dev/null <<'EOL'
# Kernel and filesystem hardening settings
kernel.randomize_va_space = 2
kernel.kptr_restrict = 2
kernel.unprivileged_bpf_disabled = 1
#kernel.modules_disabled = 1 # Uncomment to disable module loading entirely at your own risk
kernel.sysrq = 0
kernel.core_uses_pid = 1

fs.suid_dumpable = 0
fs.protected_fifos = 2
fs.protected_hardlinks = 1
fs.protected_regular = 2
fs.protected_symlinks = 1

dev.tty.ldisc_autoload = 0

net.core.bpf_jit_harden = 2

net.ipv4.conf.all.forwarding = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.all.rp_filter = 1

net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.default.log_martians = 1

net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
EOL

sudo sysctl --system

# [SHLL-6220] Idle session handling
echo 'TMOUT=900' | sudo tee -a /etc/profile > /dev/null
echo 'readonly TMOUT' | sudo tee -a /etc/profile > /dev/null
echo 'export TMOUT' | sudo tee -a /etc/profile > /dev/null

# [MACF-6290] Enable MAC framework (AppArmor)
sudo pacman -S --noconfirm --needed apparmor apparmor.d-git
sudo systemctl enable --now apparmor

# [FILE-6344] Restricting process details to users
## Editing fstab
if ! grep -q '^proc\s\+/proc\s\+proc\s\+' /etc/fstab; then
    echo '# /proc' | sudo tee -a /etc/fstab > /dev/null
    echo 'proc    /proc    proc    defaults,hidepid=2,gid=wheel    0 0' | sudo tee -a /etc/fstab > /dev/null
else
    sudo sed -i 's|^proc[[:space:]]\+/proc[[:space:]]\+proc[[:space:]]\+.*$|proc    /proc    proc    defaults,hidepid=1,gid=wheel    0 0|' /etc/fstab
fi
## Remount /proc to apply changes immediately
sudo systemctl daemon-reload
sudo mount -o remount /proc

# [FILE-6374] Check mount options
# if /dev/shm is not in /etc/fstab, add it with the correct options
if ! grep -q '^tmpfs\s\+/dev/shm\s\+tmpfs\s\+' /etc/fstab; then
    echo '# /dev/shm' | sudo tee -a /etc/fstab > /dev/null
    echo 'tmpfs    /dev/shm    tmpfs    rw,nosuid,nodev,noexec    0 0' | sudo tee -a /etc/fstab > /dev/null
else
    sudo sed -i 's|^tmpfs[[:space:]]\+/dev/shm[[:space:]]\+tmpfs[[:space:]]\+.*$|tmpfs    /dev/shm    tmpfs    rw,nosuid,nodev,noexec    0 0|' /etc/fstab
fi
# Remount /dev/shm to apply changes immediately
sudo systemctl daemon-reload
sudo mount -o remount /dev/shm

# Replace /tmp mount
if ! grep -q '^tmpfs\s\+/tmp\s\+tmpfs\s\+' /etc/fstab; then
    echo '# /tmp' | sudo tee -a /etc/fstab > /dev/null
    echo 'tmpfs    /tmp    tmpfs    rw,nosuid,nodev,noexec    0 0' | sudo tee -a /etc/fstab > /dev/null
else
    sudo sed -i 's|^tmpfs[[:space:]]\+/tmp[[:space:]]\+tmpfs[[:space:]]\+.*$|tmpfs    /tmp    tmpfs    rw,nosuid,nodev,noexec    0 0|' /etc/fstab
fi
# Remount /tmp to apply changes immediately
sudo systemctl daemon-reload
sudo mount -o remount /tmp

# [FILE-6430] Disable mounting of some filesystems
sudo tee /etc/modprobe.d/fs_blacklist.conf > /dev/null <<EOL
# Blacklist unnecessary filesystem modules to reduce attack surface

# Cramfs (Compressed ROM filesystem)
blacklist cramfs
install cramfs /bin/false

# HFS and HFS+ (Apple filesystems)
blacklist hfs
install hfs /bin/false

blacklist hfsplus
install hfsplus /bin/false

# JFFS2 (Journaling Flash Filesystem)
blacklist jffs2
install jffs2 /bin/false

# SquashFS (Compressed read-only filesystem, often used for live media/AppImage)
blacklist squashfs
install squashfs /bin/false

# UDF (Universal Disk Format, used for optical media like DVD/BD)
blacklist udf
install udf /bin/false
EOL

# [BANN-7126] Add legal banner to /etc/issue
sudo tee /etc/issue > /dev/null <<EOL
********************************************************************
*                  WARNING - UNAUTHORIZED ACCESS                   *
*                                                                  *
* Unauthorized access to this computer system is strictly          *
* prohibited. Individuals accessing, using, or modifying this      *
* system without explicit authorization will be subject to legal   *
* action and prosecuted to the fullest extent of the law.          *
*                                                                  *
* Authorized users should have no expectation of privacy. All      *
* activity on this system is monitored, recorded, and may be used  *
* as evidence in criminal or civil proceedings.                    *
********************************************************************
\n - \l
EOL

# [HRDN-7220] Don't install /usr/bin/as by adding it to NoExtract
if sudo grep -q 'usr/bin/as' /etc/pacman.conf; then
    : # already present
else
    if sudo grep -qE '^[[:space:]]*NoExtract' /etc/pacman.conf; then
        sudo sed -i '0,/^[[:space:]]*NoExtract/ s|^\([[:space:]]*NoExtract[[:space:]]*=[[:space:]]*\)\(.*\)$|\1\2 usr/bin/as|' /etc/pacman.conf
        elif sudo grep -qE '^[[:space:]]*#[[:space:]]*NoExtract' /etc/pacman.conf; then
        sudo sed -i '/^[[:space:]]*#[[:space:]]*NoExtract/ a NoExtract = usr/bin/as' /etc/pacman.conf
    else
        sudo bash -c 'printf "\n# NoExtract added by hardening script\nNoExtract = usr/bin/as\n" >> /etc/pacman.conf'
    fi
fi

# [HRDN-7222] Restricting compilator access to root user only
sudo chown 700 /usr/bin/as
sudo chmod 700 /usr/bin/gcc
sudo chmod 700 /usr/bin/g++
sudo chmod 700 /usr/bin/cc
sudo chmod 700 /usr/bin/c++
sudo chmod 700 /usr/bin/ld
sudo chmod 700 /usr/bin/lld
sudo chmod 700 /usr/bin/clang

# [PKGS-7320] Checking for package auditing tools
sudo pacman -S --noconfirm --needed arch-audit

# [FILE-7524] Ensuring file permissions
sudo chmod 600 /etc/ssh/sshd_config
sudo chmod 700 /etc/cron.hourly

# [CRYP-8004] Presence of hardware random number generator
sudo pacman -S --noconfirm --needed rng-tools
sudo systemctl enable --now rngd

# [CRYP-8005] Presence of software pseudo random number generator
sudo pacman -S --noconfirm --needed haveged
sudo systemctl enable --now haveged

# [CRYP-8006] Ensure MemoryOverwriteRequest-bit set
sudo tee /usr/lib/systemd/system-shutdown/mor-bit-wipe.sh > /dev/null <<'EOL'
#!/bin/bash

# Path to the MemoryOverwriteRequestControl UEFI variable
MOR_VAR_PATH="/sys/firmware/efi/efivars/MemoryOverwriteRequestControl-e20939be-32d4-41be-a150-897f85d49829"

# Check if the UEFI variable path exists
if [ -e "$MOR_VAR_PATH" ]; then
    # The expected format is: Attributes (4 bytes) + Value (1 byte for MOR state)
    # We need to write 5 bytes in total: 0x07 0x00 0x00 0x00 (Attributes) + 0x01 (MOR-bit set)

    # Use printf to create the necessary 5-byte data and write it to the variable
    # 0x01 means MOR is SET (request memory wipe)
    printf "\x07\x00\x00\x00\x01" | dd of="$MOR_VAR_PATH" bs=5 count=1 conv=notrunc >/dev/null 2>&1

    # Log the action (optional, for debugging/audit logs)
    echo "$(date) - Successfully set MOR-bit (MemoryOverwriteRequestControl) for next boot memory wipe." >> /var/log/mor-wipe.log
fi

exit 0
EOL
sudo chmod +x /usr/lib/systemd/system-shutdown/mor-bit-wipe.sh

# [AUTH-9230] Ensure password hashing algorithm is set to YESCRYPT and hashing rounds to minimum of 5000 and maximum of 5000000
sudo sed -i 's/^ENCRYPT_METHOD .*/ENCRYPT_METHOD YESCRYPT/' /etc/login.defs
sudo sed -i 's/^#SHA_CRYPT_MIN_ROUNDS .*/SHA_CRYPT_MIN_ROUNDS 5000/' /etc/login.defs
sudo sed -i 's/^#SHA_CRYPT_MAX_ROUNDS .*/SHA_CRYPT_MAX_ROUNDS 5000000/' /etc/login.defs

# [AUTH-9262] Password strength checking tool is installed
sudo pacman -S --noconfirm --needed libpwquality
sudo tee /etc/security/pwquality.conf > /dev/null <<EOL
# PAM pwquality configuration file
retry = 3
difok = 6
minlen = 14
dcredit = -1
ucredit = -1
ocredit = -1
lcredit = -1
EOL

sudo sed -i '/^password\s*required\s*pam_unix.so\s*try_first_pass\s*nullok\s*shadow/i password   required                    pam_pwquality.so' /etc/pam.d/system-auth

# [AUTH-9286] Ensure minimum days between password changes is 7 or more and maximum days is 90 or less
sudo sed -i 's/^PASS_MIN_DAYS.*/PASS_MIN_DAYS 7/' /etc/login.defs
sudo sed -i 's/^PASS_MAX_DAYS.*/PASS_MAX_DAYS 90/' /etc/login.defs

# [AUTH-9328] Ensure default user umask is 027 or more restrictive
sudo sed -i 's/^UMASK.*/UMASK 027/' /etc/login.defs
if sudo grep -qE '^[[:space:]]*#?[[:space:]]*umask' /etc/bash.bashrc; then
    sudo sed -i 's/^[[:space:]]*#\?[[:space:]]*umask.*/umask 027/' /etc/bash.bashrc
else
    echo 'umask 027' | sudo tee -a /etc/bash.bashrc > /dev/null
fi
if sudo grep -qE '^[[:space:]]*#?[[:space:]]*umask' /etc/profile; then
    sudo sed -i 's/^[[:space:]]*#\?[[:space:]]*umask.*/umask 027/' /etc/profile
else
    echo 'umask 027' | sudo tee -a /etc/profile > /dev/null
fi

# [AUTH-9408] Logging of failed login attempts is enabled
if sudo grep FAILLOG_ENAB /etc/login.defs; then
    sudo sed -i 's/^FAILLOG_ENAB .*/FAILLOG_ENAB yes/' /etc/login.defs
else
    echo 'FAILLOG_ENAB yes' | sudo tee -a /etc/login.defs > /dev/null
fi

# [ACCT-9622] Enable process accounting
sudo pacman -S --noconfirm --needed acct
sudo systemctl enable --now acct

# [ACCT-9626] Enable sysstat to collect accounting data
sudo pacman -S --noconfirm --needed sysstat
sudo systemctl enable --now sysstat-collect.timer sysstat-rotate.timer

# [ACCT-9628] Enable auditd to collect audit data
sudo systemctl enable --now auditd audit-rules

# [ACCT-9630] Configure auditd rules
sudo tee /etc/audit/rules.d/10-harden.rules > /dev/null <<EOL
# Monitor attempts to change system time
-w /etc/localtime -p wa -k time-change

# Monitor attempts to change user/group info (password changes)
-w /etc/passwd -p wa -k user-info
-w /etc/shadow -p wa -k user-info
-w /etc/group -p wa -k user-info
-w /etc/gshadow -p wa -k user-info

# Make the configuration immutable (must be the last line)
-e 2
EOL

# To test
# Function to create basic systemd hardening drop-in
create_systemd_hardening () {
    SERVICE="$1"
    DROPIN="/etc/systemd/system/${SERVICE}.d"
    sudo mkdir -p "$DROPIN"
  sudo tee "$DROPIN/hardening.conf" > /dev/null <<EOL
[Service]
PrivateTmp=true
ProtectSystem=full
ProtectHome=true
NoNewPrivileges=true
ProtectKernelTunables=yes
ProtectKernelModules=yes
ProtectClock=true
ProtectHostname=true
ProtectControlGroups=true
PrivateDevices=false
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
SystemCallFilter=@system-service
UMask=0077
EOL
    sudo systemctl daemon-reload
}

# Add conservative hardening overrides for high-risk services you should review
SERVICES_TO_HARDEN=(
    "NetworkManager"
    "accounts-daemon"
    "aidecheck"
    "auditd"
    "bluetooth"
    "bolt"
    "dbus-broker"
    "dirmngr@etc-pacman.d-gnupg"
    "dm-event"
    "emergency"
    "firewalld"
    "fprintd"
    "getty@tty1"
    "gpg-agent@etc-pacman.d-gnupg"
    "keyboxd@etc-pacman.d-gnupg"
    "lenovo-cfgservice"
    "libvirtd"
    "meshagent"
    "ollama"
    "packagekit"
    "plymouth-start"
    "rescue"
    "rtkit-daemon"
    "sddm"
    "snapper-cleanup"
    "snapper-timeline"
    "syslog-ng@default"
    "systemd-ask-password-console"
    "systemd-ask-password-plymouth"
    "systemd-ask-password-wall"
    "systemd-bsod"
    "systemd-rfkill"
    "systemd-importd"
    "systemd-machined"
    "systemd-udevd"
    "udisks2"
    "user@1000"
    "virtlockd"
    "waydroid-container"
    "wpa_supplicant"
)
for S in "${SERVICES_TO_HARDEN[@]}"; do
    if systemctl list-unit-files | grep -q "$S"; then
        create_systemd_hardening "$S"
    fi
done