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Matching an IP to a CIDR mask in PHP 5?

Posted by: admin November 19, 2017 Leave a comment

Questions:

I’m looking for quick/simple method for matching a given IP4 dotted quad IP to a CIDR notation mask.

I have a bunch of IPs I need to see if they match a range of IPs.

example:

$ips = array('10.2.1.100', '10.2.1.101', '10.5.1.100', '1.2.3.4');

foreach ($ips as $IP) {
    if (cidr_match($IP, '10.2.0.0/16') == true) {
        print "you're in the 10.2 subnet\n"; 
    }
}

What would cidr_match() look like?

It doesn’t really have to be simple, but fast would be good. Anything that uses only built-in/common functions is a bonus (as I’m likely to get one person to show me something in pear that does this, but I can’t depend on pear or that package being installed where my code is deployed).

Answers:

If only using IPv4:

  • use ip2long() to convert the IPs and the subnet range into long integers
  • convert the /xx into a subnet mask
  • do a bitwise ‘and’ (i.e. ip & mask)’ and check that that ‘result = subnet’

something like this should work:

function cidr_match($ip, $range)
{
    list ($subnet, $bits) = explode('/', $range);
    $ip = ip2long($ip);
    $subnet = ip2long($subnet);
    $mask = -1 << (32 - $bits);
    $subnet &= $mask; # nb: in case the supplied subnet wasn't correctly aligned
    return ($ip & $mask) == $subnet;
}

Questions:
Answers:

I found many of these methods breaking after PHP 5.2. However the following solution works on versions 5.2 and above:

function cidr_match($ip, $cidr)
{
    list($subnet, $mask) = explode('/', $cidr);

    if ((ip2long($ip) & ~((1 << (32 - $mask)) - 1) ) == ip2long($subnet))
    { 
        return true;
    }

    return false;
}

Example results

cidr_match("1.2.3.4", "0.0.0.0/0"):         true
cidr_match("127.0.0.1", "127.0.0.1/32"):    true
cidr_match("127.0.0.1", "127.0.0.2/32"):    false

Source http://www.php.net/manual/en/function.ip2long.php#82397.

Questions:
Answers:

In a similar situation, I ended up using symfony/http-foundation.

When using this package, your code would look like:

$ips = array('10.2.1.100', '10.2.1.101', '10.5.1.100', '1.2.3.4');

foreach($ips as $IP) {
    if (\Symfony\Component\HttpFoundation\IpUtils::checkIp($_SERVER['REMOTE_ADDR'], '10.2.0.0/16')) {
        print "you're in the 10.2 subnet\n";
    }
}

It also handles IPv6.

Link: https://packagist.org/packages/symfony/http-foundation

Questions:
Answers:

Some function changed:

  • split with explode

function cidr_match($ip, $range)
{
    list ($subnet, $bits) = explode('/', $range);
    $ip = ip2long($ip);
    $subnet = ip2long($subnet);
    $mask = -1 << (32 - $bits);
    $subnet &= $mask; 
    return ($ip & $mask) == $subnet;
}

Questions:
Answers:

My technique uses bit to bit matching using subnet and mask.

function cidr_match($ip, $range){
    list ($subnet, $bits) = explode('/', $range);
    $ip = substr(IP2bin($ip),0,$bits) ;
    $subnet = substr(IP2Bin($subnet),0,$bits) ;
    return ($ip == $subnet) ;
}

function IP2Bin($ip){
    $ips = explode(".",$ip) ;
    foreach ($ips as $iptmp){
        $ipbin .= sprintf("%08b",$iptmp) ;
    }
    return $ipbin ;
}

Questions:
Answers:

I also needed to test IP’s against CIDR masks. I’ve found a website with excellent explanation and sourcecode which works perfectly well.

The website http://pgregg.com/blog/2009/04/php-algorithms-determining-if-an-ip-is-within-a-specific-range/

Because the website can one day cease to exist, here is the code

<?php

/*
 * ip_in_range.php - Function to determine if an IP is located in a
 *                   specific range as specified via several alternative
 *                   formats.
 *
 * Network ranges can be specified as:
 * 1. Wildcard format:     1.2.3.*
 * 2. CIDR format:         1.2.3/24  OR  1.2.3.4/255.255.255.0
 * 3. Start-End IP format: 1.2.3.0-1.2.3.255
 *
 * Return value BOOLEAN : ip_in_range($ip, $range);
 *
 * Copyright 2008: Paul Gregg <pgregg@pgregg.com>
 * 10 January 2008
 * Version: 1.2
 *
 * Source website: http://www.pgregg.com/projects/php/ip_in_range/
 * Version 1.2
 *
 * This software is Donationware - if you feel you have benefited from
 * the use of this tool then please consider a donation. The value of
 * which is entirely left up to your discretion.
 * http://www.pgregg.com/donate/
 *
 * Please do not remove this header, or source attibution from this file.
 */


// decbin32
// In order to simplify working with IP addresses (in binary) and their
// netmasks, it is easier to ensure that the binary strings are padded
// with zeros out to 32 characters - IP addresses are 32 bit numbers
Function decbin32 ($dec) {
  return str_pad(decbin($dec), 32, '0', STR_PAD_LEFT);
}

// ip_in_range
// This function takes 2 arguments, an IP address and a "range" in several
// different formats.
// Network ranges can be specified as:
// 1. Wildcard format:     1.2.3.*
// 2. CIDR format:         1.2.3/24  OR  1.2.3.4/255.255.255.0
// 3. Start-End IP format: 1.2.3.0-1.2.3.255
// The function will return true if the supplied IP is within the range.
// Note little validation is done on the range inputs - it expects you to
// use one of the above 3 formats.
Function ip_in_range($ip, $range) {
  if (strpos($range, '/') !== false) {
    // $range is in IP/NETMASK format
    list($range, $netmask) = explode('/', $range, 2);
    if (strpos($netmask, '.') !== false) {
      // $netmask is a 255.255.0.0 format
      $netmask = str_replace('*', '0', $netmask);
      $netmask_dec = ip2long($netmask);
      return ( (ip2long($ip) & $netmask_dec) == (ip2long($range) & $netmask_dec) );
    } else {
      // $netmask is a CIDR size block
      // fix the range argument
      $x = explode('.', $range);
      while(count($x)<4) $x[] = '0';
      list($a,$b,$c,$d) = $x;
      $range = sprintf("%u.%u.%u.%u", empty($a)?'0':$a, empty($b)?'0':$b,empty($c)?'0':$c,empty($d)?'0':$d);
      $range_dec = ip2long($range);
      $ip_dec = ip2long($ip);

      # Strategy 1 - Create the netmask with 'netmask' 1s and then fill it to 32 with 0s
      #$netmask_dec = bindec(str_pad('', $netmask, '1') . str_pad('', 32-$netmask, '0'));

      # Strategy 2 - Use math to create it
      $wildcard_dec = pow(2, (32-$netmask)) - 1;
      $netmask_dec = ~ $wildcard_dec;

      return (($ip_dec & $netmask_dec) == ($range_dec & $netmask_dec));
    }
  } else {
    // range might be 255.255.*.* or 1.2.3.0-1.2.3.255
    if (strpos($range, '*') !==false) { // a.b.*.* format
      // Just convert to A-B format by setting * to 0 for A and 255 for B
      $lower = str_replace('*', '0', $range);
      $upper = str_replace('*', '255', $range);
      $range = "$lower-$upper";
    }

    if (strpos($range, '-')!==false) { // A-B format
      list($lower, $upper) = explode('-', $range, 2);
      $lower_dec = (float)sprintf("%u",ip2long($lower));
      $upper_dec = (float)sprintf("%u",ip2long($upper));
      $ip_dec = (float)sprintf("%u",ip2long($ip));
      return ( ($ip_dec>=$lower_dec) && ($ip_dec<=$upper_dec) );
    }

    echo 'Range argument is not in 1.2.3.4/24 or 1.2.3.4/255.255.255.0 format';
    return false;
  }

}
?>

(I did not develop this; this is developed by Paul Gregg (http://pgregg.com/)

Questions:
Answers:

Here is one fast 64bits function to do it, please comment the return line you don’t need. Accepting any valid Ipv4 with or without valid CIDR Routing Prefix for example 63.161.156.0/24 or 63.161.156.0

<?php
function cidr2range($ipv4){
if ($ip=strpos($ipv4,'/'))
{$n_ip=(1<<(32-substr($ipv4,1+$ip)))-1;   $ip_dec=ip2long(substr($ipv4,0,$ip)); }
else
{$n_ip=0;                                   $ip_dec=ip2long($ipv4);             }
$ip_min=$ip_dec&~$n_ip;
$ip_max=$ip_min+$n_ip;
#Array(2) of Decimal Values Range
return [$ip_min,$ip_max];
#Array(2) of Ipv4 Human Readable Range
return [long2ip($ip_min),long2ip($ip_max)];
#Array(2) of Ipv4 and Subnet Range
return [long2ip($ip_min),long2ip(~$n_ip)];
#Array(2) of Ipv4 and Wildcard Bits
return [long2ip($ip_min),long2ip($n_ip)];
#Integer Number of Ipv4 in Range
return ++$n_ip;
}

To fast check if a given ipv4 is matching a given CIDR you can do it inline like in this example

<?php
$given_cidr='55.55.55.0/24';
$given_ipv4='55.55.55.55';
if(($range=cidr2range($given_cidr)) &&
($check=ip2long($given_ipv4))!==false &&
$check>=$range[0] && $check<=$range[1])
{
echo 'Yes, '.$given_ipv4.' is included in '.$given_cidr;
}
else
{
echo 'No, '.$given_ipv4.' is not included in '.$given_cidr;
}

To get the full range as an array for a given IP (with or without CIDR Routing Prefix) you can use the following code but be carefull because for example 25.25.25.25/16 return an array with 65536 elements and you can easily run out of memory using a smaller Routing Prefix

<?php
$result=cidr2range($ipv4);
for($ip_dec=$result[0];$ip_dec<=$result[1];$ip_dec++)
$full_range[$ip_dec]=long2ip($ip_dec);
print_r($full_range);

To fast check if a given ipv4 is matching a given array of IP (with or without CIDR Routing Prefix)

<?php
#This code is checking if a given ip belongs to googlebot
$given_ipv4='74.125.61.208';
$given_cidr_array=['108.59.93.43/32','108.59.93.40/31','108.59.93.44/30','108.59.93.32/29','108.59.93.48/28','108.59.93.0/27','108.59.93.64/26','108.59.93.192/26','108.59.92.192/27','108.59.92.128/26','108.59.92.96/27','108.59.92.0/27','108.59.94.208/29','108.59.94.192/28','108.59.94.240/28','108.59.94.128/26','108.59.94.16/29','108.59.94.0/28','108.59.94.32/27','108.59.94.64/26','108.59.95.0/24','108.59.88.0/22','108.59.81.0/27','108.59.80.0/24','108.59.82.0/23','108.59.84.0/22','108.170.217.128/28','108.170.217.160/27','108.170.217.192/26','108.170.217.0/25','108.170.216.0/24','108.170.218.0/23','108.170.220.0/22','108.170.208.0/21','108.170.192.0/20','108.170.224.0/19','108.177.0.0/17','104.132.0.0/14','104.154.0.0/15','104.196.0.0/14','107.167.160.0/19','107.178.192.0/18','125.17.82.112/30','125.16.7.72/30','74.125.0.0/16','72.14.192.0/18','77.109.131.208/28','77.67.50.32/27','66.102.0.0/20','66.227.77.144/29','66.249.64.0/19','67.148.177.136/29','64.124.98.104/29','64.71.148.240/29','64.68.64.64/26','64.68.80.0/20','64.41.221.192/28','64.41.146.208/28','64.9.224.0/19','64.233.160.0/19','65.171.1.144/28','65.170.13.0/28','65.167.144.64/28','65.220.13.0/24','65.216.183.0/24','70.32.132.0/23','70.32.128.0/22','70.32.136.0/21','70.32.144.0/20','85.182.250.128/26','85.182.250.0/25','80.239.168.192/26','80.149.20.0/25','61.246.224.136/30','61.246.190.124/30','63.237.119.112/29','63.226.245.56/29','63.158.137.224/29','63.166.17.128/25','63.161.156.0/24','63.88.22.0/23','41.206.188.128/26','12.234.149.240/29','12.216.80.0/24','8.34.217.24/29','8.34.217.0/28','8.34.217.32/27','8.34.217.64/26','8.34.217.128/25','8.34.216.0/24','8.34.218.0/23','8.34.220.0/22','8.34.208.128/29','8.34.208.144/28','8.34.208.160/27','8.34.208.192/26','8.34.208.0/25','8.34.209.0/24','8.34.210.0/23','8.34.212.0/22','8.35.195.128/28','8.35.195.160/27','8.35.195.192/26','8.35.195.0/25','8.35.194.0/24','8.35.192.0/23','8.35.196.0/22','8.35.200.0/21','8.8.8.0/24','8.8.4.0/24','8.6.48.0/21','4.3.2.0/24','23.236.48.0/20','23.251.128.0/19','216.239.32.0/19','216.252.220.0/22','216.136.145.128/27','216.33.229.160/29','216.33.229.144/29','216.34.7.176/28','216.58.192.0/19','216.109.75.80/28','216.74.130.48/28','216.74.153.0/27','217.118.234.96/28','208.46.199.160/29','208.44.48.240/29','208.21.209.0/28','208.184.125.240/28','209.185.108.128/25','209.85.128.0/17','213.200.103.128/26','213.200.99.192/26','213.155.151.128/26','199.192.112.224/29','199.192.112.192/27','199.192.112.128/26','199.192.112.0/25','199.192.113.176/28','199.192.113.128/27','199.192.113.192/26','199.192.113.0/25','199.192.115.80/28','199.192.115.96/27','199.192.115.0/28','199.192.115.128/25','199.192.114.192/26','199.192.114.0/25','199.223.232.0/21','198.108.100.192/28','195.16.45.144/29','192.104.160.0/23','192.158.28.0/22','192.178.0.0/15','206.160.135.240/28','207.223.160.0/20','203.222.167.144/28','173.255.125.72/29','173.255.125.80/28','173.255.125.96/27','173.255.125.0/27','173.255.125.128/25','173.255.124.240/29','173.255.124.232/29','173.255.124.192/27','173.255.124.128/29','173.255.124.144/28','173.255.124.160/27','173.255.124.48/29','173.255.124.32/28','173.255.124.0/27','173.255.124.64/26','173.255.126.0/23','173.255.122.128/26','173.255.122.64/26','173.255.123.0/24','173.255.121.128/26','173.255.121.0/25','173.255.120.0/24','173.255.117.32/27','173.255.117.64/26','173.255.117.128/25','173.255.116.192/27','173.255.116.128/26','173.255.116.0/25','173.255.118.0/23','173.255.112.0/22','173.194.0.0/16','172.102.8.0/21','172.253.0.0/16','172.217.0.0/16','162.216.148.0/22','162.222.176.0/21','180.87.33.64/26','128.177.109.0/26','128.177.119.128/25','128.177.163.0/25','130.211.0.0/16','142.250.0.0/15','146.148.0.0/17'];
echo '<pre>';
$in_range=false;
if (($given_ipv4_dec=ip2long($given_ipv4))!==false)
{
foreach($given_cidr_array as $given_cidr){
if(($range=cidr2range($given_cidr)) &&
$given_ipv4_dec>=$range[0] && $given_ipv4_dec<=$range[1])
{
$in_range=true;
echo $given_ipv4.' matched '.$given_cidr.' ('.join(array_map('long2ip',$range),' - ').")\n";
}
}
}
echo $given_ipv4.' is probably'.($in_range?'':' not').' a Googlebot IP';

To run fast the function don’t check input but formally it should be a string matching the following regex

#^(?:((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))(?:/((?:(?:0)|(?:3[0-2])|(?:[1-2]?[0-9]))))?)$#

If you want to verify the input before using the function

<?php
if (is_string($ipv4) && preg_match('#^(?:((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))\.((?:0)|(?:2(?:(?:[0-4][0-9])|(?:5[0-5])))|(?:1?[0-9]{1,2}))(?:/((?:(?:0)|(?:3[0-2])|(?:[1-2]?[0-9]))))?)$#',$ipv4))
{
#This is a valid ipv4 with or without CIDR Routing Prefix
$result=cidr2range($ipv4);
print_r($result);
}

Then the formal answer to your question is the following

<?php
#Requiring cidr2range shown above function
function cidr_match($mixed_ip,$mixed_cidr){
if (!is_array($mixed_ip)){
$string_mode=true;
$mixed_ip=[$mixed_ip=>0];
}
else $mixed_ip=array_fill_keys($mixed_ip,0);
if (!is_array($mixed_cidr)) $mixed_cidr=[$mixed_cidr];
foreach($mixed_ip   as $ip => &$result)
foreach($mixed_cidr as $cidr)
{
if(($range=cidr2range($cidr)) &&
($check=ip2long($ip))!==false &&
$check>=$range[0] && $check<=$range[1]){
$result=$cidr;
break;
}
}
$mixed_ip=array_filter($mixed_ip);
return $string_mode?($mixed_ip?true:false):$mixed_ip;
}

print '<pre>';

#Your example
$ips = array('10.2.1.100', '10.2.1.101', '10.5.1.100', '1.2.3.4');

foreach ($ips as $IP) {
    if (cidr_match($IP, '10.2.0.0/16') == true) {
        print "you're in the 10.2 subnet\n"; 
    }
}


#Also working with IP array and/or CIDR array
#If IP array is given then return an array containing IP (keys) matching CIDR (values)
$result=cidr_match($ips,['20.2.0.0/16','10.2.0.0/15']);
foreach($result as $ip => $cidr){
print "$ip is in the $cidr subnet\n"; 
}

You can compile your own function using these examples, hope these few lines have helped you…

Questions:
Answers:
function cidr_match($ipStr, $cidrStr) {
  $ip = ip2long($ipStr);
  $cidrArr = split('/',$cidrStr);
  $maskIP = ip2long($cidrArr[0]);
  $maskBits = 32 - $cidrArr[1];
  return (($ip>>$maskBits) == ($maskIP>>$maskBits));
}

Questions:
Answers:

Just a note, Alnitak’s answer works 32/64 bit.

Here is a cooked version of it, for quick spam protection based on country IP lists that you can get everywhere. google for country ip list or country ip block (Have to give one here, really difficult to find it in that sites page navigation:Country ip block generator)

Copy-paste your cidr ip list to string $cidrs. And put this code just before page html, possibly in the header.php file.

Can also be used to filter adsense use in page templates based on country.

This is only a in-the-middle-of-the-night-urgency solution. Sometimes one needs to come up with something like this for a client quickly yesterday, so here it is.

//++++++++++++++++++++++
//COUNTRY SPAM PROTECTOR
//speed: ~5ms @ 2000 cidrs
//comments start with #
//++++++++++++++++++++++
$cidrs=
'
#yourcountry
1.3.4.5/21
#mycountry
6.7.8.9/20
';
//$cidrs.="\n".'123.12.12.12/32';//test, your ip
$cidrs_ar=preg_split('/\s+/',$cidrs,-1,PREG_SPLIT_NO_EMPTY);
$ip=@$_SERVER['REMOTE_ADDR'];
$iplong=ip2long($ip);
//var_export($cidrs_ar);var_export($ip);var_export($iplong);
if($iplong)
  foreach($cidrs_ar as $cidr)
    {
    $ar=explode ('/', $cidr);
    $netiplong=ip2long($ar[0]);
    if($netiplong===false) continue;
    $mask=intval(@$ar[1]);
    if(!$mask) continue;
    $bitmask=-1 <<(32-$mask);
    if(($iplong & $bitmask) == ($netiplong & $bitmask))
        {
        header('Location: http://www.someotherwebsite.com/',true,303);
        exit;
        }
    }

Questions:
Answers:

You also can use Net_IPv4 PEAR library.

function cidr_match($ip, $net){
  include_once("Net/IPv4.php");
  $objIP = new Net_IPv4();
  return $objIP->ipInNetwork($ip, $net);
}

Questions:
Answers:

Perhaps it is useful to someone.

Convert bit mask into IP mask:

// convert 12 => 255.240.0.0
// ip2long('255.255.255.255') == -1
$ip = long2ip((-1 << (32 - $bit)) & -1);

Convert IP mask into bit mask:

// convert 255.240.0.0 => 12

// is valid IP
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) === false) {
    throw new \InvalidArgumentException(sprintf('Invalid IP "%s".', $ip));
}

// convert decimal to binary
$mask = '';
foreach (explode('.', $ip) as $octet) {
    $mask .= str_pad(decbin($octet), 8, '0', STR_PAD_LEFT);
}

// check mask
if (strpos('01', $mask) !== false) {
    // valid   11111111111111111111111100000000 -> 255.255.255.0
    // invalid 11111111111111111111111100000001 -> 255.255.255.1
    throw new \InvalidArgumentException(sprintf('IP mask "%s" is not valid.', $ip));
}

$bit = substr_count($mask, '1'); // bit mask

Questions:
Answers:

I want to have you look at my few lines. The examples that people suggested before me don’t seem to work. One reason being, as far as I understand it, is that CIDR mask bits are binary numbers, so the bit shift must be done on a binary number. I have tried converting the long IP’s into binaries, but ran into a max binary number limit.
OK, here my few lines … I await your comments.

function cidr_match($ipStr, $cidrStr) {

$ipStr = explode('.', $ipStr);
foreach ($ipStr as $key => $val) {
    $ipStr[$key] = str_pad(decbin($val), 8, '0', STR_PAD_LEFT);
    }
$ip = '';
foreach ($ipStr as $binval) {
    $ip = $ip . $binval;
    }

$cidrArr = explode('/',$cidrStr);

$maskIP = explode('.', $cidrArr[0]);
foreach ($maskIP as $key => $val) {
    $maskIP[$key] = str_pad(decbin($val), 8, '0', STR_PAD_LEFT);
    }
$maskIP = '';
foreach ($ipStr as $binval) {
    $maskIP = $maskIP . $binval;
    }
$maskBits = 32 - $cidrArr[1];
return (($ip>>$maskBits) == ($maskIP>>$maskBits));  
}

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