<?php
/**
 * @package   FOF
 * @copyright Copyright (c)2010-2021 Nicholas K. Dionysopoulos / Akeeba Ltd
 * @license   GNU General Public License version 2, or later
 */

namespace FOF40\IP;

defined('_JEXEC') || die;

/**
 * IP address helper
 *
 * Makes sure that we get the real IP of the user
 */
class IPHelper
{
	/**
	 * The IP address of the current visitor
	 *
	 * @var   string
	 */
	protected static $ip;

	/**
	 * Should I allow IP overrides through X-Forwarded-For or Client-Ip HTTP headers?
	 *
	 * @var    bool
	 */
	protected static $allowIpOverrides = true;

	/**
	 * See self::detectAndCleanIP and setUseFirstIpInChain
	 *
	 * If this is enabled (default) self::detectAndCleanIP will return the FIRST IP in case there is an IP chain coming
	 * for example from an X-Forwarded-For HTTP header. When set to false it will simulate the old behavior in FOF up to
	 * and including 3.1.1 which returned the LAST IP in the list.
	 *
	 * @var   bool
	 */
	protected static $useFirstIpInChain = true;

	/**
	 * List of headers we should check to know if the user is behind a proxy. PLEASE NOTE: ORDER MATTERS!
	 *
	 * @var array
	 */
	protected static $proxyHeaders = [
		'HTTP_CF_CONNECTING_IP',        // CloudFlare
		'HTTP_X_FORWARDED_FOR',         // Standard for transparent proxy (e.g. NginX)
		'HTTP_X_SUCURI_CLIENTIP',       // Sucuri firewall uses its own header
	];

	/**
	 * Set the $useFirstIpInChain flag. See above.
	 *
	 * @param   bool  $value
	 */
	public static function setUseFirstIpInChain(bool $value = true): void
	{
		self::$useFirstIpInChain = $value;
	}

	/**
	 * Getter for the list of proxy headers we can check
	 *
	 * @return array
	 */
	public static function getProxyHeaders(): array
	{
		return static::$proxyHeaders;
	}

	/**
	 * Get the current visitor's IP address
	 *
	 * @return string
	 */
	public static function getIp(): string
	{
		if (is_null(static::$ip))
		{
			$ip = self::detectAndCleanIP();

			if (!empty($ip) && ($ip != '0.0.0.0') && function_exists('inet_pton') && function_exists('inet_ntop'))
			{
				$myIP = @inet_pton($ip);

				if ($myIP !== false)
				{
					$ip = inet_ntop($myIP);
				}
			}

			static::setIp($ip);
		}

		return static::$ip;
	}

	/**
	 * Set the IP address of the current visitor
	 *
	 * @param   string  $ip
	 *
	 * @return  void
	 */
	public static function setIp(string $ip): void
	{
		static::$ip = $ip;
	}

	/**
	 * Checks if an IP is contained in a list of IPs or IP expressions
	 *
	 * @param   string        $ip       The IPv4/IPv6 address to check
	 * @param   array|string  $ipTable  An IP expression (or a comma-separated or array list of IP expressions) to
	 *                                  check against
	 *
	 * @return  boolean  True if it's in the list
	 */
	public static function IPinList(string $ip, $ipTable = ''): bool
	{
		// No point proceeding with an empty IP list
		if (empty($ipTable))
		{
			return false;
		}

		// If the IP list is not an array, convert it to an array
		if (!is_array($ipTable))
		{
			if (strpos($ipTable, ',') !== false)
			{
				$ipTable = explode(',', $ipTable);
				$ipTable = array_map(function ($x) {
					return trim($x);
				}, $ipTable);
			}
			else
			{
				$ipTable = trim($ipTable);
				$ipTable = [$ipTable];
			}
		}

		// If no IP address is found, return false
		if ($ip == '0.0.0.0')
		{
			return false;
		}

		// If no IP is given, return false
		if (empty($ip))
		{
			return false;
		}

		// Sanity check
		if (!function_exists('inet_pton'))
		{
			return false;
		}

		// Get the IP's in_adds representation
		$myIP = @inet_pton($ip);

		// If the IP is in an unrecognisable format, quite
		if ($myIP === false)
		{
			return false;
		}

		$ipv6 = self::isIPv6($ip);

		foreach ($ipTable as $ipExpression)
		{
			$ipExpression = trim($ipExpression);

			// Inclusive IP range, i.e. 123.123.123.123-124.125.126.127
			if (strstr($ipExpression, '-'))
			{
				[$from, $to] = explode('-', $ipExpression, 2);

				if ($ipv6 && (!self::isIPv6($from) || !self::isIPv6($to)))
				{
					// Do not apply IPv4 filtering on an IPv6 address
					continue;
				}
				elseif (!$ipv6 && (self::isIPv6($from) || self::isIPv6($to)))
				{
					// Do not apply IPv6 filtering on an IPv4 address
					continue;
				}

				$from = @inet_pton(trim($from));
				$to   = @inet_pton(trim($to));

				// Sanity check
				if (($from === false) || ($to === false))
				{
					continue;
				}

				// Swap from/to if they're in the wrong order
				if ($from > $to)
				{
					[$from, $to] = [$to, $from];
				}

				if (($myIP >= $from) && ($myIP <= $to))
				{
					return true;
				}
			}
			// Netmask or CIDR provided
			elseif (strstr($ipExpression, '/'))
			{
				$binaryip = self::inet_to_bits($myIP);

				[$net, $maskbits] = explode('/', $ipExpression, 2);
				if ($ipv6 && !self::isIPv6($net))
				{
					// Do not apply IPv4 filtering on an IPv6 address
					continue;
				}
				elseif (!$ipv6 && self::isIPv6($net))
				{
					// Do not apply IPv6 filtering on an IPv4 address
					continue;
				}
				elseif ($ipv6 && strstr($maskbits, ':'))
				{
					// Perform an IPv6 CIDR check
					if (self::checkIPv6CIDR($myIP, $ipExpression))
					{
						return true;
					}

					// If we didn't match it proceed to the next expression
					continue;
				}
				elseif (!$ipv6 && strstr($maskbits, '.'))
				{
					// Convert IPv4 netmask to CIDR
					$long     = ip2long($maskbits);
					$base     = ip2long('255.255.255.255');
					$maskbits = 32 - log(($long ^ $base) + 1, 2);
				}

				// Convert network IP to in_addr representation
				$net = @inet_pton($net);

				// Sanity check
				if ($net === false)
				{
					continue;
				}

				// Get the network's binary representation
				$binarynet            = self::inet_to_bits($net);
				$expectedNumberOfBits = $ipv6 ? 128 : 24;
				$binarynet            = str_pad($binarynet, $expectedNumberOfBits, '0', STR_PAD_RIGHT);

				// Check the corresponding bits of the IP and the network
				$ip_net_bits = substr($binaryip, 0, $maskbits);
				$net_bits    = substr($binarynet, 0, $maskbits);

				if ($ip_net_bits === $net_bits)
				{
					return true;
				}
			}
			elseif ($ipv6)
			{
				$ipExpression = trim($ipExpression);

				if (!self::isIPv6($ipExpression))
				{
					continue;
				}

				$ipCheck = @inet_pton($ipExpression);

				if ($ipCheck === false)
				{
					continue;
				}

				if ($ipCheck === $myIP)
				{
					return true;
				}
			}
			else
			{
				// Standard IPv4 address, i.e. 123.123.123.123 or partial IP address, i.e. 123.[123.][123.][123]
				$dots = 0;
				if (substr($ipExpression, -1) == '.')
				{
					// Partial IP address. Convert to CIDR and re-match
					foreach (count_chars($ipExpression, 1) as $i => $val)
					{
						if ($i == 46)
						{
							$dots = $val;
						}
					}

					$netmask = '255.255.255.255';

					switch ($dots)
					{
						case 1:
							$netmask      = '255.0.0.0';
							$ipExpression .= '0.0.0';
							break;

						case 2:
							$netmask      = '255.255.0.0';
							$ipExpression .= '0.0';
							break;

						case 3:
							$netmask      = '255.255.255.0';
							$ipExpression .= '0';
							break;

						default:
							$dots = 0;
					}

					if ($dots)
					{
						$binaryip = self::inet_to_bits($myIP);

						// Convert netmask to CIDR
						$long     = ip2long($netmask);
						$base     = ip2long('255.255.255.255');
						$maskbits = 32 - log(($long ^ $base) + 1, 2);

						$net = @inet_pton($ipExpression);

						// Sanity check
						if ($net === false)
						{
							continue;
						}

						// Get the network's binary representation
						$binarynet            = self::inet_to_bits($net);
						$expectedNumberOfBits = $ipv6 ? 128 : 24;
						$binarynet            = str_pad($binarynet, $expectedNumberOfBits, '0', STR_PAD_RIGHT);

						// Check the corresponding bits of the IP and the network
						$ip_net_bits = substr($binaryip, 0, $maskbits);
						$net_bits    = substr($binarynet, 0, $maskbits);

						if ($ip_net_bits === $net_bits)
						{
							return true;
						}
					}
				}
				if (!$dots)
				{
					$ip = @inet_pton(trim($ipExpression));
					if ($ip == $myIP)
					{
						return true;
					}
				}
			}
		}

		return false;
	}

	/**
	 * Works around the REMOTE_ADDR not containing the user's IP
	 */
	public static function workaroundIPIssues(): void
	{
		$ip = self::getIp();

		if (array_key_exists('REMOTE_ADDR', $_SERVER) && ($_SERVER['REMOTE_ADDR'] == $ip))
		{
			return;
		}

		if (array_key_exists('REMOTE_ADDR', $_SERVER))
		{
			$_SERVER['FOF_REMOTE_ADDR'] = $_SERVER['REMOTE_ADDR'];
		}
		elseif (function_exists('getenv'))
		{
			if (getenv('REMOTE_ADDR'))
			{
				$_SERVER['FOF_REMOTE_ADDR'] = getenv('REMOTE_ADDR');
			}
		}

		$_SERVER['REMOTE_ADDR'] = $ip;
	}

	/**
	 * Should I allow the remote client's IP to be overridden by an X-Forwarded-For or Client-Ip HTTP header?
	 *
	 * @param   bool  $newState  True to allow the override
	 *
	 * @return  void
	 */
	public static function setAllowIpOverrides(bool $newState): void
	{
		self::$allowIpOverrides = $newState;
	}

	/**
	 * Is it an IPv6 IP address?
	 *
	 * @param   string  $ip  An IPv4 or IPv6 address
	 *
	 * @return  boolean  True if it's IPv6
	 */
	protected static function isIPv6(string $ip): bool
	{
		return strstr($ip, ':') !== false;
	}

	/**
	 * Gets the visitor's IP address. Automatically handles reverse proxies
	 * reporting the IPs of intermediate devices, like load balancers. Examples:
	 * https://www.akeeba.com/support/admin-tools/13743-double-ip-adresses-in-security-exception-log-warnings.html
	 * http://stackoverflow.com/questions/2422395/why-is-request-envremote-addr-returning-two-ips
	 * The solution used is assuming that the first IP address is the external one (unless $useFirstIpInChain is set to
	 * false)
	 *
	 * @return  string
	 */
	protected static function detectAndCleanIP(): string
	{
		$ip = static::detectIP();

		if ((strstr($ip, ',') !== false) || (strstr($ip, ' ') !== false))
		{
			$ip  = str_replace(' ', ',', $ip);
			$ip  = str_replace(',,', ',', $ip);
			$ips = explode(',', $ip);
			$ip  = '';

			// Loop until we're running out of parts or we have a hit
			while ($ips)
			{
				$ip = array_shift($ips);
				$ip = trim($ip);

				if (self::$useFirstIpInChain)
				{
					return self::cleanIP($ip);
				}
			}
		}

		return self::cleanIP($ip);
	}

	protected static function cleanIP(string $ip): string
	{
		$ip = trim($ip);
		$ip = strtoupper($ip);

		/**
		 * Work around IPv4-mapped addresses.
		 *
		 * IPv4 addresses may be embedded in an IPv6 address. This is always 80 zeroes, 16 ones and the IPv4 address.
		 * In all possible IPv6 notations this is:
		 * 0:0:0:0:0:FFFF:192.168.1.1
		 * ::FFFF:192.168.1.1
		 * ::FFFF:C0A8:0101
		 *
		 * @see http://www.tcpipguide.com/free/t_IPv6IPv4AddressEmbedding-2.htm
		 */
		if ((strpos($ip, '::FFFF:') === 0) || (strpos($ip, '0:0:0:0:0:FFFF:') === 0))
		{
			// Fast path: the embedded IPv4 is in decimal notation.
			if (strstr($ip, '.') !== false)
			{
				return substr($ip, strrpos($ip, ':') + 1);
			}

			// Get the embedded IPv4 (in hex notation)
			$ip = substr($ip, strpos($ip, ':FFFF:') + 6);
			// Convert each 16-bit WORD to decimal
			[$word1, $word2] = explode(':', $ip);
			$word1  = hexdec($word1);
			$word2  = hexdec($word2);
			$longIp = $word1 * 65536 + $word2;

			return long2ip($longIp);
		}

		return $ip;
	}

	/**
	 * Gets the visitor's IP address
	 *
	 * @return  string
	 */
	protected static function detectIP(): string
	{
		// Normally the $_SERVER superglobal is set
		if (isset($_SERVER))
		{
			// Do we have IP overrides enabled?
			if (static::$allowIpOverrides)
			{
				// If so, check for every proxy header
				foreach (static::$proxyHeaders as $header)
				{
					if (array_key_exists($header, $_SERVER))
					{
						return $_SERVER[$header];
					}
				}
			}

			// CLI applications
			if (!array_key_exists('REMOTE_ADDR', $_SERVER))
			{
				return '';
			}

			// Normal, non-proxied server or server behind a transparent proxy
			return $_SERVER['REMOTE_ADDR'];
		}

		// This part is executed on PHP running as CGI, or on SAPIs which do
		// not set the $_SERVER superglobal
		// If getenv() is disabled, you're screwed
		if (!function_exists('getenv'))
		{
			return '';
		}

		// Do we have IP overrides enabled?
		if (static::$allowIpOverrides)
		{
			// If so, check for every proxy header
			foreach (static::$proxyHeaders as $header)
			{
				if (getenv($header))
				{
					return getenv($header);
				}
			}
		}

		// Normal, non-proxied server or server behind a transparent proxy
		if (getenv('REMOTE_ADDR'))
		{
			return getenv('REMOTE_ADDR');
		}

		// Catch-all case for broken servers and CLI applications
		return '';
	}

	/**
	 * Converts inet_pton output to bits string
	 *
	 * @param   string  $inet  The in_addr representation of an IPv4 or IPv6 address
	 *
	 * @return  string
	 */
	protected static function inet_to_bits(string $inet): string
	{
		$unpacked = strlen($inet) == 4 ? unpack('C4', $inet) : unpack('C16', $inet);

		$binaryip = '';

		foreach ($unpacked as $byte)
		{
			$binaryip .= str_pad(decbin($byte), 8, '0', STR_PAD_LEFT);
		}

		return $binaryip;
	}

	/**
	 * Checks if an IPv6 address $ip is part of the IPv6 CIDR block $cidrnet
	 *
	 * @param   string  $ip       The IPv6 address to check, e.g. 21DA:00D3:0000:2F3B:02AC:00FF:FE28:9C5A
	 * @param   string  $cidrnet  The IPv6 CIDR block, e.g. 21DA:00D3:0000:2F3B::/64
	 *
	 * @return  bool
	 */
	protected static function checkIPv6CIDR(string $ip, string $cidrnet): bool
	{
		$ip       = inet_pton($ip);
		$binaryip = self::inet_to_bits($ip);

		[$net, $maskbits] = explode('/', $cidrnet);
		$net       = inet_pton($net);
		$binarynet = self::inet_to_bits($net);

		$ip_net_bits = substr($binaryip, 0, $maskbits);
		$net_bits    = substr($binarynet, 0, $maskbits);

		return $ip_net_bits === $net_bits;
	}
}
