#!/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

#######################################
# NOTE:
#   According to the manual pages of limits.conf(5) and pam_limits(8),
#   entries in '/etc/security/limits.conf' or drop-ins under
#   '/etc/security/limits.d/' are NOT applied automatically by the system.
#   The actual enforcement of these ulimit(2) constraints, including
#   '* soft core 0' and '* hard core 0' to disable kernel core dumps,
#   requires that the PAM module 'pam_limits.so' is invoked in the
#   'session' stack of the respective service (e.g., via
#   '/etc/pam.d/common-session' and
#   '/etc/pam.d/common-session-noninteractive').
#
#   Without 'pam_limits.so' present in these PAM configuration files,
#   the configured limits remain ineffective for PAM-based logins
#   (SSH, local TTY, sudo, su, cron, etc.).
#   Services launched by systemd bypass PAM and must have 'LimitCORE=0'
#   or 'DefaultLimitCORE=0' set in their unit or in system.conf.d(5).
#
# References:
#   - man 5 limits.conf
#   - man 8 pam_limits
#######################################

#######################################
# Hardening memory dump via:
#   '/etc/systemd/coredump.conf.d/disable.conf'
#   '/etc/security/limits.d/90-ciss-core.conf'
#   '/etc/systemd/system.conf.d/90-ciss-core.conf'
#   '/etc/pam.d/common-session'
#   '/etc/pam.d/common-session-noninteractive'
# Globals:
#   TARGET
#   VAR_ARCHITECTURE
#   VAR_CODENAME
#   VAR_VERSION
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
hardening_memory() {
  mkdir -p "${TARGET}/etc/systemd/coredump.conf.d"
  mkdir -p "${TARGET}/etc/systemd/system.conf.d"

  insert_header   "${TARGET}/etc/security/limits.d/99-ciss-core.conf"
  insert_comments "${TARGET}/etc/security/limits.d/99-ciss-core.conf"
  cat << 'EOF' >> "${TARGET}/etc/security/limits.d/99-ciss-core.conf"
# Enforce: no core dumps for all logins by default.
# Format: <domain> <type> <item> <value>
*     hard core 0
*     soft core 0
root  hard core 0
root  soft core 0

# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=conf
EOF


  insert_header   "${TARGET}/etc/systemd/coredump.conf.d/disable.conf"
  insert_comments "${TARGET}/etc/systemd/coredump.conf.d/disable.conf"
  cat << 'EOF' >> "${TARGET}/etc/systemd/coredump.conf.d/disable.conf"
### Do not store core images anywhere, keep the at most minimal metadata.

[Coredump]
Storage=none
ProcessSizeMax=0
ExternalSizeMax=0
JournalSizeMax=0

# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=conf
EOF


  [[ -f  "${TARGET}/etc/systemd/system.conf.d/10-coredump-debian.conf" ]] && \
    mv "${TARGET}/etc/systemd/system.conf.d/10-coredump-debian.conf" "${TARGET}/etc/systemd/system.conf.d/10-coredump-debian.conf.bak"


  insert_header   "${TARGET}/etc/systemd/system.conf.d/99-ciss-core.conf"
  insert_comments "${TARGET}/etc/systemd/system.conf.d/99-ciss-core.conf"
  cat << 'EOF' >> "${TARGET}/etc/systemd/system.conf.d/99-ciss-core.conf"
[Manager]
DefaultLimitCORE=0

# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=conf
EOF

  guard_pam_limits

  guard_dir && return 0
}

#######################################
# Ensure 'pam_limits.so' is activated in:
#   '/etc/pam.d/common-session'
#   '/etc/pam.d/common-session-noninteractive'
# Globals:
#   TARGET
# Arguments:
#   None
# Returns:
#   0: on success
#######################################
guard_pam_limits() {
  ### Declare Arrays, HashMaps, and Variables.
  declare     var_file_0="${TARGET}/etc/pam.d/common-session"
  declare     var_file_1="${TARGET}/etc/pam.d/common-session-noninteractive"
  declare     var_line='session required pam_limits.so' var_file=""
  declare -i  var_changed=0

  for var_file in "${var_file_0}" "${var_file_1}"; do

    [[ -f "${var_file}" ]] || continue

    ### Already active (not commented out)?
    if grep -qE '^[[:space:]]*session[[:space:]]+required[[:space:]]+pam_limits\.so([[:space:]]|$)' "${var_file}"; then

      continue

    fi

    ### If only commented out, activate (preferred over blunt appending).
    if grep -qE '^[[:space:]]*#([[:space:]]*)session[[:space:]]+required[[:space:]]+pam_limits\.so([[:space:]]|$)' "${var_file}"; then

      ### Remove comment characters at the beginning of lines (atomically via tmp file).
      declare var_tmp; var_tmp="$(mktemp "${var_file}.XXXXXX")"

      awk '
        /^[[:space:]]*#([[:space:]]*)session[[:space:]]+required[[:space:]]+pam_limits\.so([[:space:]]|$)/ {
          sub(/^[[:space:]]*#([[:space:]]*)/,""); print; next
        } { print }
      ' "${var_file}" >> "${var_tmp}" && mv -- "${var_tmp}" "${var_file}"

      var_changed=1
      continue
    fi

    ### Otherwise, append to the end (cleanly with a new line).
    printf '\n%s\n' "${var_line}" >> "${var_file}"
    var_changed=1

  done

  (( var_changed )) && do_log "info" "file_only" "4460() Activated pam_limits.so: (common-session[*])"

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