Now supporting GitHub public IPs in CIDR notation using IP to CIDR matching. GitHub public ips have also been updated to include the IPS in CIDR notation as stated on 'WebHook URLs settings page', see new screenshot on the README, and https://help.github.com/articles/what-ip-addresses-does-github-use-that-i-should-whitelist

Author: Ollie Rattue

class.GitHubHook.php

@@ -37,10 +37,9 @@ class GitHubHook
   private $_branches = array();
 
   /**
-   * @var array GitHub's IP addresses for hooks.
-   * @since 1.1
+   * @var array GitHub's public IP addresses for hooks (CIDR notation).
    */
-  private $_ips = array('54.235.183.49', '54.235.183.23', '54.235.118.251', '54.235.120.57', '54.235.120.61', '54.235.120.62');
+  private $_github_public_cidrs = array('207.97.227.253/32', '50.57.128.197/32', '108.171.174.178/32', '50.57.231.61/32', '204.232.175.64/27', '192.30.252.0/22');
 
   /**
    * Constructor.
@@ -79,6 +78,39 @@ private function _notFound($reason = NULL) {
     exit;
   }
 
+  /**
+   * IP in CIDRs Match - checks whether an IP exists within an array of CIDR ranges.
+   * @link - http://stackoverflow.com/questions/10243594/find-whether-a-given-ip-exists-in-cidr-or-not?lq=1
+   * @param string $ip - IP address in '127.0.0.1' format
+   * @param array $cidrs - array storing CIDRS in 192.168.1.20/27 format.
+   * @return bool
+   */
+  private function ip_in_cidrs($ip, $cidrs) {
+	$ipu = explode('.', $ip);
+		
+	foreach ($ipu as &$v) {
+		$v = str_pad(decbin($v), 8, '0', STR_PAD_LEFT);
+	}
+		
+	$ipu = join('', $ipu);
+	$result = FALSE;
+		
+	foreach ($cidrs as $cidr) {
+		$parts = explode('/', $cidr);
+		$ipc = explode('.', $parts[0]);
+		
+		foreach ($ipc as &$v) $v = str_pad(decbin($v), 8, '0', STR_PAD_LEFT); {
+			$ipc = substr(join('', $ipc), 0, $parts[1]);
+			$ipux = substr($ipu, 0, $parts[1]);
+			$result = ($ipc === $ipux);				
+		}
+			
+		if ($result) break;
+	}
+		
+	return $result;
+  }
+	
   /**
    * Enable log of debug messages.
    * @since 1.0
@@ -120,7 +152,8 @@ public function log($message) {
    * @since 1.0
    */
   public function deploy() {
-    if (in_array($this->_remoteIp, $this->_ips)) {
+	// Check the remote is a whitelisted GitHub public ip.
+    if ($this->ip_in_cidrs($this->_remote_ip, $this->_github_public_cidrs)) {
       foreach ($this->_branches as $branch) {
         if ($this->_payload->ref == 'refs/heads/' . $branch['name']) {
 
@@ -129,6 +162,7 @@ public function deploy() {
         }
       }
     } else {
+	  // IP of remote is invalid.
       $this->_notFound('IP address not recognized: ' . $this->_remoteIp);
     }
   }