hide-hardware-info

#!/bin/bash

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

set -e

sysfs_whitelist=1
cpuinfo_whitelist=1

## https://www.whonix.org/wiki/Security-misc#selinux
selinux=0

shopt -s nullglob

## Allows for disabling the whitelist.
for i in /etc/hide-hardware-info.d/*.conf
do
  bash -n "${i}"
  source "${i}"
done

create_whitelist() {
  if [ "${1}" = "sysfs" ]; then
    whitelist_path="/sys"
  elif [ "${1}" = "cpuinfo" ]; then
    whitelist_path="/proc/cpuinfo"
  else
    echo "ERROR: ${1} is not a correct parameter."
    exit 1
  fi

  if grep -q "${1}" /etc/group; then
    ## Changing the permissions of /sys recursively
    ## causes errors as the permissions of /sys/kernel/debug
    ## and /sys/fs/cgroup cannot be changed.
    chgrp -fR "${1}" "${whitelist_path}" || true

    chmod o-rwx "${whitelist_path}"
  else
    echo "ERROR: The ${1} group does not exist, the ${1} whitelist was not created."
  fi
}

## sysfs and debugfs expose a lot of information
## that should not be accessible by an unprivileged
## user which includes hardware info, debug info and
## more. This restricts /sys, /proc/cpuinfo, /proc/bus
## and /proc/scsi to the root user only. This hides
## many hardware identifiers from ordinary users
## and increases security.
for i in /proc/cpuinfo /proc/bus /proc/scsi /sys
do
  if [ -e "${i}" ]; then
    if [ "${i}" = "/sys" ]; then
      ## Whitelist for /sys.
      if [ "${sysfs_whitelist}" = "1" ]; then
        create_whitelist sysfs
      else
        chmod og-rwx /sys
        echo "INFO: The sysfs whitelist is not enabled. Some things may not work properly."
      fi
    elif [ "${i}" = "/proc/cpuinfo" ]; then
      ## Whitelist for /proc/cpuinfo.
      if [ "${cpuinfo_whitelist}" = "1" ]; then
        create_whitelist cpuinfo
      else
        chmod og-rwx /proc/cpuinfo
        echo "INFO: The cpuinfo whitelist is not enabled. Some things may not work properly."
      fi
    else
      chmod og-rwx "${i}"
    fi
  else
    ## /proc/scsi doesn't exist on Debian so errors
    ## are expected here.
    if ! [ "${i}" = "/proc/scsi" ]; then
      echo "ERROR: ${i} could not be found."
    fi
  fi
done

## https://www.whonix.org/wiki/Security-misc#selinux
##
## on SELinux systems, at least /sys/fs/selinux
## must be visible to unprivileged users, else
## SELinux userspace utilities will not function
## properly
if [ -d /sys/fs/selinux ]; then
  if [ "${selinux}" = "1" ]; then
    ## restrict permissions on everything but
    ## what is needed
    for i in /sys/* /sys/fs/*
    do
      if [ "${sysfs_whitelist}" = "1" ]; then
        chmod o-rwx "${i}" || continue
      else
        chmod og-rwx "${i}" || continue
      fi
    done
    chmod o+rx /sys /sys/fs /sys/fs/selinux
    echo "INFO: SELinux mode enabled. Restrictions loosened slightly in order to allow userspace utilities to function."
  else
    echo "INFO: SELinux detected, but SELinux mode is not enabled. Some userspace utilities may not work properly."
  fi
fi