Tool that checks if a given IP-address is valid in a specified subnet. The tool also specefies if the checked IP-address is a Network ID or Broadcast address and echo out the result. The tool is a php script that can be ran in CLI by any client with php installed. Use the tool this way: php ip_subnet_validator.php [IP] [SUBNET] Example: php ip_s…

ip_subnet-Validator.php

<?php
error_reporting(0);
print("\n");

$slashpos = strpos($argv[2], '/');  //get the position of the '/' in $argv[1]
$checkIP = $argv[1];
$ip = substr($argv[2], 0, $slashpos); //Use this to break out the ip and cidr-number
//if the ip is shorter than 4 chars (x.x.x.x) or if the ip is logner than 16 chars xxx.xxx.xxx.xxx
//kill the script and tell user that ip is invalid
if(strlen($ip) > 15 || strlen($ip) < 7){
  die("Invalid ip");
}
//check if a fraction of a ip fr.fr.fr.fr has a value of over 255 assume that the ip is invalid
//also convert the ip address to binary Array
$ipFractions = explode(".", $ip);
$ipBinary = array();

foreach ($ipFractions as $fraction) {
  if($fraction > 255 || $fraction < 0){
    die("Invalid ip");
  }
  array_push($ipBinary, sprintf( "%08d", decbin($fraction)));
}

//if the cidr number is greater than 32 kill the script and tell the user that the CIDR number is invalid.
$cidr = substr($argv[2], $slashpos+1);
if($cidr > 32 ||$cidr < 0){
  die("Invalid CIDR input");
}

//make a new array and push 1 or zeros to it (convert cidr to binary subnetmask)
$subnetBinary = array();

for($i = 1; $i <= 32; $i++){
  if($i <= $cidr){
    array_push($subnetBinary, '1');
  }else{
    array_push($subnetBinary, '0');
  }
}
$subnetBinary = implode($subnetBinary); //convert the char array to a string variable.

//make an array of the subnet in .-separated fractions
$subnetBinaryArray = array();
array_push($subnetBinaryArray, substr($subnetBinary, 0, 8) );
array_push($subnetBinaryArray, substr($subnetBinary, 8, 8) );
array_push($subnetBinaryArray, substr($subnetBinary, 16, 8) );
array_push($subnetBinaryArray, substr($subnetBinary, 24, 8) );

//get the first ip in binary.
$first = array();

for ($i = 0; $i < 4; $i++){
  $fraction = array();
  for($j = 0; $j < 8; $j++){
    array_push($fraction, ( substr($subnetBinaryArray[$i], $j, 1) * substr($ipBinary[$i], $j, 1) ) );
  }
  array_push($first, implode("", $fraction));
}

//get the last ip in binary
$lastStr = array();

for($k = 0; $k < 32; $k++){
  $netmask = substr($subnetBinary, $k, 1);
  $ipaddr = substr(implode($ipBinary), $k, 1);
  if($netmask == 0){
    $num = 1;
  }else{
    $num = $ipaddr;
  }
  array_push($lastStr, $num);
}
//convert the last ip to an array splited by . e.g array(192, 168, 0, 1)
$last = array();
array_push($last, substr( implode($lastStr), 0, 8) );
array_push($last, substr( implode($lastStr), 8, 8) );
array_push($last, substr( implode($lastStr), 16, 8) );
array_push($last, substr( implode($lastStr), 24, 8) );


//convert the last and first ip in range to decimal
$min = array();
$max = array();

foreach($last as $b){
  array_push($max, bindec($b));
}
foreach($first as $b){
  array_push($min, bindec($b));
}


//check if ip is in range
if( (ip2long(implode(".", $min)) <= ip2long($checkIP)) && ( ip2long($checkIP) <= ip2long(implode(".", $max)))){
  print("True");

  if (ip2long(implode(".", $min)) == ip2long($checkIP)){
    print("Net id");
  }elseif (ip2long(implode(".", $max)) == ip2long($checkIP)){
    print("broadcast");
  }

}else{
  print("False");
}

?>