srandom

#!/bin/bash

#  Copyright (C) 2015 Jonathan Senkerik

#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.

#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.

#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.


PATH=/usr/sbin:/usr/bin:/bin:/sbin
export PATH



is_mod_loaded(){
    lsmod |grep -q srandom 
    return $?
}

is_srandom_OK(){
    if [ `dd if=/dev/srandom count=4 bs=2k 2>/dev/null|hexdump -ve '4/2 "%02X " "\n"'|sort|uniq|wc -l` -eq 1024 ];then
      return 0
    else
      return 1
    fi
}

is_linked(){
    S=`ls -i /dev/srandom|awk '{print $1}'`
    U=`ls -i /dev/urandom|awk '{print $1}'`
    if [[ $S -eq $U ]];then
      return 0
    else
      return 1
    fi

}



case "$1" in
  set)
    if is_mod_loaded >/dev/null; then
      if is_linked >/dev/null; then
        restorecon /dev/urandom >/dev/null 2>1
        exit 0
      else
	if [ ! -f /dev/urandom.orig ];then
          mv /dev/urandom /dev/urandom.orig
	fi
        ln /dev/srandom /dev/urandom
        chcon system_u:object_r:urandom_device_t:s0 /dev/srandom >/dev/null 2>1
      fi
    else
      echo "Module not loaded"
    fi
    ;;

  default)
    rm -f /dev/urandom 
    mknod -m 444 /dev/urandom c 1 9 
    restorecon /dev/urandom >/dev/null 2>1
    ;;
  status)
    if is_mod_loaded >/dev/null; then
      echo "Module loaded"
    else
      echo "Module not loaded" 
    fi
    if [ -c /dev/srandom ];then
      if is_srandom_OK >/dev/null; then
        echo "srandom is functioning correctly"
      else
        echo "srandom FAILED to generate random numbers"
      fi
      if is_linked >/dev/null; then
        echo "/dev/urandom is LINKED to /dev/srandom (system is using srandom)"
      else
        echo "/dev/urandom is NOT LINKED to /dev/srandom (system is using built-in generator)"
      fi
      cat /proc/srandom
    fi
    ;;
  *)
    echo "NAME"
    echo
    echo "    /usr/bin/srandom -  /dev/srandom device configuration tool"
    echo
    echo "Usage"
    echo
    echo "/usr/bin/srandom [set|default|status]"
    echo
    echo "   set - Set /dev/srandom as the system PRNG (/dev/urandom)."
    echo
    echo "   default - Use the built-in PRNG as the system /dev/urandom."
    echo
    echo "   status - Display status of srandom module."
    echo
    echo "   help - Display this message"
    echo
    ;;
esac