#!/bin/bash
# SPDX-Version: 3.0
# SPDX-CreationInfo: 2025-06-17; WEIDNER, Marc S.; <msw@coresecret.dev>
# SPDX-ExternalRef: GIT https://git.coresecret.dev/msw/CISS.debian.installer.git
# SPDX-FileContributor: WEIDNER, Marc S.; Centurion Intelligence Consulting Agency
# SPDX-FileCopyrightText: 2024-2025; WEIDNER, Marc S.; <msw@coresecret.dev>
# SPDX-FileType: SOURCE
# SPDX-License-Identifier: EUPL-1.2 OR LicenseRef-CCLA-1.0
# SPDX-LicenseComment: This file is part of the CISS.debian.installer.secure framework.
# SPDX-PackageName: CISS.debian.installer
# SPDX-Security-Contact: security@coresecret.eu

guard_sourcing

#######################################
# Hardening files and directories.
# Globals:
#   None
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
hardening_fail2ban() {
  ### Declare Arrays, HashMaps, and Variables.
  declare
  declare -r  var_logfile="/root/.ciss/cdi/log/4435_hardening_fail2ban.log"

  chroot_logger "${TARGET}${var_logfile}"

  chroot_script "${TARGET}" "
    export INITRD=No
    apt-get install -y --no-install-suggests fail2ban 2>&1 | tee -a ${var_logfile}
    echo ExitCode: \$? >> ${var_logfile}
  "
  cp -u /etc/fail2ban/fail2ban.conf "${DIR_BAK}"fail2ban.conf.bak
  mv "${TARGET}/etc/resolv.conf" "${TARGET}/root/.ciss/cdi/backup/etc/resolv.conf.bak"


  # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1024305
  sed -i 's/#allowipv6 = auto/allowipv6 = auto/1' /etc/fail2ban/fail2ban.conf

  mv /etc/fail2ban/jail.d/defaults-debian.conf /etc/fail2ban/jail.d/defaults-debian.conf.bak
  chmod 644 /etc/fail2ban/jail.d/defaults-debian.conf.bak

  if [[ "${JUMPHOST,,}" = "yes" ]]; then

    ###########################################################################################
    # Remarks: fail2ban ufw aggresive mode - one attempt for Jumphost configuration           #
    ###########################################################################################
    cat <<EOF >/etc/fail2ban/jail.d/centurion-default.conf
##### Added by hardening.sh - Module: do_hardening_fail2ban #####

[DEFAULT]
usedns    = yes
ignoreip  = 127.0.0.0/8 ::1
# $FQDN
  $IPV4 $IPV6/64
# Jumphost
  $JUMPHOST_IPV4 $JUMPHOST_IPV6/64
maxretry  = 8
findtime  = 12h
bantime   = 12h

[sshd]
enabled   = true
backend   = systemd
filter    = sshd
mode      = normal
port      = $SSHPORT
protocol  = tcp
logpath   = /var/log/auth.log
maxretry  = 3
findtime  = 1d
bantime   = 1d

#
# ufw aggressive approach:
# Any valid client communicating with our server should be going directly to the service ports opened in ufw (ssh, 80, 443, ...).
# Any client touching other ports is treated malicious and therefore should be blocked access to ALL ports after 1 attempt.
#

[ufw]
enabled   = true
filter    = ufw.aggressive
action    = iptables-allports
logpath   = /var/log/ufw.log
maxretry  = 1
findtime  = 1d
bantime   = 1d
protocol  = tcp,udp

EOF

  else
    ###########################################################################################
    # Remarks: fail2ban ufw aggresive mode 32 attempts for NO Jumphost configuration          #
    ###########################################################################################
    cat <<EOF >/etc/fail2ban/jail.d/centurion-default.conf
##### Added by hardening.sh - Module: do_hardening_fail2ban #####

[DEFAULT]
usedns    = yes
ignoreip  = 127.0.0.0/8 ::1
# $FQDN
  $IPV4 $IPV6/64
maxretry  = 8
findtime  = 12h
bantime   = 12h

[sshd]
enabled   = true
backend   = systemd
filter    = sshd
mode      = normal
port      = $SSHPORT
protocol  = tcp
logpath   = /var/log/auth.log
maxretry  = 3
findtime  = 1d
bantime   = 1d

#
# ufw aggressive approach:
# Any valid client communicating with our server should be going directly to the service ports opened in ufw (ssh, 80, 443, ...).
# Any client touching other ports is treated malicious and therefore should be blocked access to ALL ports after 32 attempts.
#

[ufw]
enabled   = true
filter    = ufw.aggressive
action    = iptables-allports
logpath   = /var/log/ufw.log
maxretry  = 32
findtime  = 1d
bantime   = 1d
protocol  = tcp,udp

EOF

  fi

  cat <<EOF >/etc/fail2ban/filter.d/ufw.aggressive.conf
##### Added by hardening.sh - Module: do_hardening_fail2ban  #####

[Definition]
failregex = ^.*UFW BLOCK.* SRC=<HOST> .*DPT=\d+ .*
ignoreregex =

EOF

  ###########################################################################################
  # Remarks: hardening of fail2ban systemd                                                  #
  ###########################################################################################
  # https://wiki.archlinux.org/title/fail2ban#Service_hardening                             #
  # The CapabilityBoundingSet parameters CAP_DAC_READ_SEARCH will allow Fail2ban full read  #
  # access to every directory and file. CAP_NET_ADMIN and CAP_NET_RAW allow Fail2ban to     #
  # operate # on any firewall that has command-line shell interface. By using               #
  # ProtectSystem=strict the filesystem hierarchy will only be read-only, ReadWritePaths    #
  # allows Fail2ban to have write access on required paths.                                 #
  ###########################################################################################
  mkdir -p /etc/systemd/system/fail2ban.service.d
  mkdir /var/log/fail2ban

  cat <<EOF >/etc/systemd/system/fail2ban.service.d/override.conf
[Service]
PrivateDevices=yes
PrivateTmp=yes
ProtectHome=read-only
ProtectSystem=strict
ReadWritePaths=-/var/run/fail2ban
ReadWritePaths=-/var/lib/fail2ban
ReadWritePaths=-/var/log/fail2ban
ReadWritePaths=-/var/spool/postfix/maildrop
ReadWritePaths=-/run/xtables.lock
CapabilityBoundingSet=CAP_AUDIT_READ CAP_DAC_READ_SEARCH CAP_NET_ADMIN CAP_NET_RAW
##### Added by CenDev
ProtectClock=true
ProtectHostname=true
EOF

  cat <<EOF >>/etc/fail2ban/fail2ban.local
[Definition]
logtarget = /var/log/fail2ban/fail2ban.log
EOF

  ###########################################################################################
  # Remarks: Hetzner needs special ignoreip rules                                           #
  ###########################################################################################
  if [[ "${VPSPROVIDER,,}" = "hetzner" ]]; then
    sed -i '0,/^maxretry/{s/^maxretry/# Hetzner Intern\n  172.31.1.1\/16\n&/}' /etc/fail2ban/jail.d/centurion-default.conf
  fi

  ###########################################################################################
  # Remarks: Logrotate must be updated either                                               #
  ###########################################################################################
  cp -a /etc/logrotate.d/fail2ban "${DIR_BAK}"fail2ban_logrotate.bak
  sed -i 's/\/var\/log\/fail2ban.log/\/var\/log\/fail2ban\/fail2ban.log/1' /etc/logrotate.d/fail2ban
  touch /var/log/fail2ban/fail2ban.log
  chmod 640 /var/log/fail2ban/fail2ban.log

  guard_dir && return 0
}
# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh