security-misc/debian/security-misc.preinst

#!/bin/bash

## Copyright (C) 2012 - 2019 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
## See the file COPYING for copying conditions.

if [ -f /usr/lib/helper-scripts/pre.bsh ]; then
   source /usr/lib/helper-scripts/pre.bsh
fi

set -e

true "
#####################################################################
## INFO: BEGIN: $DPKG_MAINTSCRIPT_PACKAGE $DPKG_MAINTSCRIPT_NAME $@
#####################################################################
"

sudo_users_check () {
   if command -v "qubesdb-read" &>/dev/null; then
      ## Qubes users can use dom0 to get a root terminal emulator.
      ## For example:
      ## qvm-run -u root debian-10 xterm
      return 0
   fi

   sudo_users="$(getent group sudo | cut -d: -f4)"
   ## example sudo_users:
   ## user,root

   OLD_IFS="$IFS"
   IFS=","
   export IFS

   for user_with_sudo in $sudo_users ; do
      if [ "$user_with_sudo" = "root" ]; then
         ## root login is also restricted.
         ## Therefore user "root" being member of group "sudo" is
         ## considered insufficient.
         continue
      fi
      are_there_any_sudo_users=yes
      break
   done

   IFS="$OLD_IFS"
   export IFS

   ## Prevent users from locking themselves out.
   ## https://forums.whonix.org/t/is-security-misc-suitable-for-hardening-bridges-and-relays/8299/4
   if [ ! "$are_there_any_sudo_users" = "yes" ]; then
      echo "$0: ERROR: No user is a member of group 'sudo'. Installation aborted." >&2
      echo "$0: ERROR: You probably want to run:" >&2
      echo "" >&2
      echo "sudo adduser user sudo" >&2
      echo "sudo adduser user console" >&2
      echo "" >&2
      echo "$0: ERROR: See also installation instructions:" >&2
      echo "https://www.whonix.org/wiki/security-misc#install" >&2
      exit 200
   fi
}

console_users_check() {
   console_users="$(getent group console | cut -d: -f4)"
   ## example ssh_users:
   ## user
   console_unrestricted_users="$(getent group console-unrestricted | cut -d: -f4)"

   OLD_IFS="$IFS"
   IFS=","
   export IFS

   for user_with_console in $console_users $console_unrestricted_users ; do
      if [ "$user_with_console" = "root" ]; then
         ## root login is also restricted.
         ## Therefore user "root" being member of group "console" is
         ## considered insufficient.
         continue
      fi
      are_there_any_console_users=yes
      break
   done

   IFS="$OLD_IFS"
   export IFS

   ## Prevent users from locking themselves out.
   ## https://forums.whonix.org/t/is-security-misc-suitable-for-hardening-bridges-and-relays/8299/4
   if [ ! "$are_there_any_console_users" = "yes" ]; then
      echo "$0: ERROR: No user is a member of group 'console'. Installation aborted." >&2
      echo "$0: ERROR: You probably want to run:" >&2
      echo "" >&2
      echo "sudo adduser user console" >&2
      echo "" >&2
      echo "$0: ERROR: See also installation instructions:" >&2
      echo "https://www.whonix.org/wiki/security-misc#install" >&2
      exit 201
   fi
}

ssh_users_check() {
   if ! deb-systemd-helper --quiet was-enabled 'ssh.service'; then
      return 0
   fi

   ssh_users="$(getent group ssh | cut -d: -f4)"
   ## example ssh_users:
   ## user

   OLD_IFS="$IFS"
   IFS=","
   export IFS

   for user_with_ssh in $ssh_users ; do
      if [ "$user_with_ssh" = "root" ]; then
         ## root login is also restricted.
         ## Therefore user "root" being member of group "ssh" is
         ## considered insufficient.
         continue
      fi
      are_there_any_ssh_users=yes
      break
   done

   IFS="$OLD_IFS"
   export IFS

   ## Prevent users from locking themselves out.
   ## https://forums.whonix.org/t/is-security-misc-suitable-for-hardening-bridges-and-relays/8299/4
   if [ ! "$are_there_any_ssh_users" = "yes" ]; then
      echo "$0: ERROR: ssh.service is enabled but no user is a member of group 'ssh'." >&2
      echo "$0: ERROR: Installation aborted since this would likely break SSH login." >&2
      echo "$0: ERROR: You probably want to run:" >&2
      echo "" >&2
      echo "sudo adduser user ssh" >&2
      echo "" >&2
      echo "$0: ERROR: See also installation instructions:" >&2
      echo "https://www.whonix.org/wiki/security-misc#install" >&2
      exit 201
   fi
}

if [ "$1" = "install" ] || [ "$1" = "upgrade" ]; then
   sudo_users_check
   console_users_check
   ssh_users_check
fi

true "INFO: debhelper beginning here."

#DEBHELPER#

true "INFO: Done with debhelper."

true "
#####################################################################
## INFO: END  : $DPKG_MAINTSCRIPT_PACKAGE $DPKG_MAINTSCRIPT_NAME $@
#####################################################################
"

## Explicitly "exit 0", so eventually trapped errors can be ignored.
exit 0