What is the most accurate way to retrieve a user's correct IP address in PHP?
I know there are a plethora of $_SERVER variables headers available for IP address retrieval. I was wondering if there is a general consensus as to how to most accurately retrieve a user's real IP address (well knowing no method is perfect) using said variables?
I spent some time trying to find an in depth solution and came up with the following code based on a number of sources. I would love it if somebody could please poke holes in the answer or shed some light on something perhaps more accurate.
edit includes optimizations from @Alix
/**
* Retrieves the best guess of the client's actual IP address.
* Takes into account numerous HTTP proxy headers due to variations
* in how different ISPs handle IP addresses in headers between hops.
*/
public function get_ip_address() {
// Check for shared internet/ISP IP
if (!empty($_SERVER['HTTP_CLIENT_IP']) && $this->validate_ip($_SERVER['HTTP_CLIENT_IP']))
return $_SERVER['HTTP_CLIENT_IP'];
// Check for IPs passing through proxies
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
// Check if multiple IP addresses exist in var
$iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
foreach ($iplist as $ip) {
if ($this->validate_ip($ip))
return $ip;
}
}
}
if (!empty($_SERVER['HTTP_X_FORWARDED']) && $this->validate_ip($_SERVER['HTTP_X_FORWARDED']))
return $_SERVER['HTTP_X_FORWARDED'];
if (!empty($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']) && $this->validate_ip($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']))
return $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];
if (!empty($_SERVER['HTTP_FORWARDED_FOR']) && $this->validate_ip($_SERVER['HTTP_FORWARDED_FOR']))
return $_SERVER['HTTP_FORWARDED_FOR'];
if (!empty($_SERVER['HTTP_FORWARDED']) && $this->validate_ip($_SERVER['HTTP_FORWARDED']))
return $_SERVER['HTTP_FORWARDED'];
// Return unreliable IP address since all else failed
return $_SERVER['REMOTE_ADDR'];
}
/**
* Ensures an IP address is both a valid IP address and does not fall within
* a private network range.
*
* @access public
* @param string $ip
*/
public function validate_ip($ip) {
if (filter_var($ip, FILTER_VALIDATE_IP,
FILTER_FLAG_IPV4 |
FILTER_FLAG_IPV6 |
FILTER_FLAG_NO_PRIV_RANGE |
FILTER_FLAG_NO_RES_RANGE) === false)
return false;
self::$ip = $ip;
return true;
}
Words of Warning (update)
REMOTE_ADDR still represents the most reliable source of an IP address. The other $_SERVER variables mentioned here can be spoofed by a remote client very easily. The purpose of this solution is to attempt to determine the IP address of a client sitting behind a proxy. For your general purposes, you might consider using this in combination with the IP address returned directly from $_SERVER['REMOTE_ADDR'] and storing both.
For 99.9% of users this solution will suit your needs perfectly. It will not protect you from the 0.1% of malicious users looking to abuse your system by injecting their own request headers. If relying on IP addresses for something mission critical, resort to REMOTE_ADDR and don't bother catering to those behind a proxy.
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 $_SERVER['REMOTE_ADDR'];
}
}
The explode on HTTP_X_FORWARDED_FOR is because of weird issues we had detecting IP addresses when Squid was used.
My answer is basically just a polished, fully-validated, and fully-packaged, version of @AlixAxel's answer:
<?php
/* Get the 'best known' client IP. */
if (!function_exists('getClientIP'))
{
function getClientIP()
{
if (isset($_SERVER["HTTP_CF_CONNECTING_IP"]))
{
$_SERVER['REMOTE_ADDR'] = $_SERVER["HTTP_CF_CONNECTING_IP"];
};
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))
{
foreach (explode(',', $_SERVER[$key]) as $ip)
{
$ip = trim($ip);
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false)
{
return $ip;
};
};
};
};
return false;
};
};
$best_known_ip = getClientIP();
if(!empty($best_known_ip))
{
$ip = $clients_ip = $client_ip = $client_IP = $best_known_ip;
}
else
{
$ip = $clients_ip = $client_ip = $client_IP = $best_known_ip = '';
};
?>
Changes:
It simplifies the function name (with 'camelCase' formatting style).
It includes a check to make sure the function isn't already declared in another part of your code.
It takes into account 'CloudFlare' compatibility.
It initializes multiple "IP-related" variable names to the returned value, of the 'getClientIP' function.
It ensures that if the function doesn't return a valid IP address, all the variables are set to a empty string, instead of
null.It's only (45) lines of code.