security-misc/debian/security-misc.preinst

#!/bin/bash

## Copyright (C) 2012 - 2022 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
## See the file COPYING for copying conditions.

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

set -e

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

user_groups_modifications() {
   ## /usr/libexec/security-misc/hide-hardware-info
   addgroup --system sysfs
   addgroup --system cpuinfo

   ## group 'sudo' membership required to use 'su'
   ## /usr/share/pam-configs/wheel-security-misc
   addgroup root sudo

   ## Useful to create groups in preinst rather than postinst.
   ## Otherwise if a user saw an error message such as this:
   ##
   ## /var/lib/ dpkg/tmp.ci/preinst: ERROR: No user is a member of group 'console'. Installation aborted.
   ## /var/lib/ dpkg/tmp.ci/preinst: ERROR: You probably want to run:
   ## sudo adduser user console
   ##
   ## Then the user could not run 'sudo adduser user console' but also would
   ## have to create the groups himself.

   ## Related to Console Lockdown.
   ## /usr/share/pam-configs/console-lockdown-security-misc
   ## /etc/security/access-security-misc.conf
   addgroup --system console
   addgroup --system console-unrestricted
   ## This has no effect since by default this package also ships and an
   ## /etc/securetty configuration file that contains nothing but comments, i.e.
   ## an "empty" /etc/securetty.
   ## In case a system administrator edits /etc/securetty, there is no need to
   ## block for this to be still blocked by console lockdown. See also:
   ## https://www.whonix.org/wiki/Root#Root_Login
   addgroup root console
}

output_skip_checks() {
   echo "security-misc '$0' INFO: Allow installation of security-misc anyway." >&2
   echo "security-misc '$0' INFO: (technical reason: $@)" >&2
   echo "security-misc '$0' INFO: If this is a chroot this is probably OK." >&2
   echo "security-misc '$0' INFO: Otherwise you might not be able to login." >&2
}

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

   local sudo_users user_with_sudo are_there_any_sudo_users OLD_IFS

   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

   if [ "$are_there_any_sudo_users" = "yes" ]; then
      return 0
   fi

   ## Prevent users from locking themselves out.
   ## https://forums.whonix.org/t/is-security-misc-suitable-for-hardening-bridges-and-relays/8299/4
   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

   if [ "$SECURITY_MISC_INSTALL" = "force" ]; then
      output_skip_checks "Environment variable SECURITY_MISC_INSTALL is set to 'force'."
      return 0
   fi
   if test -f "/var/lib/security-misc/skip_install_check" ; then
      output_skip_checks "File '/var/lib/security-misc/skip_install_check' exists."
      return 0
   fi

   exit 200
}

console_users_check() {
   if [ "$SECURITY_MISC_INSTALL" = "force" ]; then
      return 0
   fi
   if test -f "/var/lib/security-misc/skip_install_check" ; then
      return 0
   fi
   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

   local console_users console_unrestricted_users user_with_console are_there_any_console_users OLD_IFS

   console_users="$(getent group console | cut -d: -f4)"
   ## example console_users:
   ## user
   console_unrestricted_users="$(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
      return 0
   fi

   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

   if [ "$SECURITY_MISC_INSTALL" = "force" ]; then
      output_skip_checks "Environment variable SECURITY_MISC_INSTALL is set to 'force'."
      return 0
   fi
   if test -f "/var/lib/security-misc/skip_install_check" ; then
      output_skip_checks "File '/var/lib/security-misc/skip_install_check' exists."
      return 0
   fi

   exit 201
}

legacy() {
   if [ -f "/var/lib/legacy/do_once/${FUNCNAME}_version_1" ]; then
      return 0
   fi

   local continue_yes user_to_be_created

   if [ -f "/usr/share/whonix/marker" ]; then
      continue_yes=true
   fi
   if [ -f "/usr/share/kicksecure/marker" ]; then
      continue_yes=true
   fi

   if [ ! "$continue_yes" = "true" ]; then
      return 0
   fi

   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

   ## https://forums.whonix.org/t/etc-security-hardening-console-lockdown-pam-access-access-conf/8592/7

   user_to_be_created=user

   if ! id "$user_to_be_created" &>/dev/null ; then
      true "INFO: user '$user_to_be_created' does not exist. Skipping addgroup console and pam-auth-update."
      return 0
   fi

   addgroup "$user_to_be_created" console

   pam-auth-update --enable console-lockdown-security-misc

   mkdir --parents "/var/lib/legacy/do_once"
   touch "/var/lib/legacy/do_once/${FUNCNAME}_version_1"
}

user_groups_modifications
legacy

if [ "$1" = "install" ] || [ "$1" = "upgrade" ]; then
   sudo_users_check
   console_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