What is the most accurate way to retrieve a user's correct IP address in PHP?
Here is a shorter, cleaner way to get the IP address:
function get_ip_address(){
foreach (array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR') as $key){
if (array_key_exists($key, $_SERVER) === true){
foreach (explode(',', $_SERVER[$key]) as $ip){
$ip = trim($ip); // just to be safe
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false){
return $ip;
}
}
}
}
}
Your code seems to be pretty complete already, I cannot see any possible bugs in it (aside from the usual IP caveats), I would change the validate_ip()
function to rely on the filter extension though:
public function validate_ip($ip)
{
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) === false)
{
return false;
}
self::$ip = sprintf('%u', ip2long($ip)); // you seem to want this
return true;
}
Also your HTTP_X_FORWARDED_FOR
snippet can be simplified from this:
// check for IPs passing through proxies
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
{
// check if multiple ips exist in var
if (strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ',') !== false)
{
$iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
foreach ($iplist as $ip)
{
if ($this->validate_ip($ip))
return $ip;
}
}
else
{
if ($this->validate_ip($_SERVER['HTTP_X_FORWARDED_FOR']))
return $_SERVER['HTTP_X_FORWARDED_FOR'];
}
}
To this:
// check for IPs passing through proxies
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
{
$iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
foreach ($iplist as $ip)
{
if ($this->validate_ip($ip))
return $ip;
}
}
You may also want to validate IPv6 addresses.
Even then however, getting a user's real IP address is going to be unreliable. All they need to do is use an anonymous proxy server (one that doesn't honor the headers for http_x_forwarded_for
, http_forwarded
, etc) and all you get is their proxy server's IP address.
You can then see if there is a list of proxy server IP addresses that are anonymous, but there is no way to be sure that is 100% accurate as well and the most it'd do is let you know it is a proxy server. And if someone is being clever, they can spoof headers for HTTP forwards.
Let's say I don't like the local college. I figure out what IP addresses they registered, and get their IP address banned on your site by doing bad things, because I figure out you honor the HTTP forwards. The list is endless.
Then there is, as you guessed, internal IP addresses such as the college network I metioned before. A lot use a 10.x.x.x format. So all you would know is that it was forwarded for a shared network.
Then I won't start much into it, but dynamic IP addresses are the way of broadband anymore. So. Even if you get a user IP address, expect it to change in 2 - 3 months, at the longest.
We use:
/**
* Get the customer's IP address.
*
* @return string
*/
public function getIpAddress() {
if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
return $_SERVER['HTTP_CLIENT_IP'];
} else if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$ips = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
return trim($ips[count($ips) - 1]);
} else {
return $_SERVER['REMOTE_ADDR'];
}
}
The explode on HTTP_X_FORWARDED_FOR is because of weird issues we had detecting IP addresses when Squid was used.