<?php
/*
 * Author: Ryan Gilfether
 * URL: http://www.gilfether.com/phpCrypt
 * Date: March 26, 2013
 * Copyright (C) 2013 Ryan Gilfether
 *
 * This file is part of phpCrypt
 *
 * phpCrypt is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

namespace PHP_Crypt;

/**
 * A base class that should not be used directly. It is intended as a base
 * object that should be extended and provides tools that child objects may use.
 *
 * @author Ryan Gilfether
 * @link http://www.gilfether.com/phpcrypt
 * @copyright 2013 Ryan Gilfether
 */
class Core
{
	/** @type integer HASH_LEN The length of md5() hash string */
	const HASH_LEN = 16;


	/**
	 * Constructor
	 *
	 */
	protected function __construct()
	{

	}


	/**
	 * Destructor
	 *
	 */
	protected function __destruct()
	{

	}


	/**
	 * Convert hexidecimal to a binary string (ex: "00110110")
	 *
	 * @param string $hex A string containing a hexidecimal number
	 * @return string A string representation of a binary
	 */
	public static function hex2Bin($hex)
	{
		// if we do not have an even number of hex characters
		// append a 0 to the beginning to make it even
		if(strlen($hex) % 2)
			$hex = "0$hex";

		$parts = str_split($hex, 2);
		$parts = array_map(function($v) {
				$v = base_convert($v, 16, 2);
				return str_pad($v, 8, "0", STR_PAD_LEFT);
		}, $parts);

		return implode("", $parts);
	}


	/**
	 * Convert hex to a string
	 *
	 * @param string $hex A string representation of Hex (IE: "1a2b3c" not 0x1a2b3c)
	 * @return string a string
	 */
	public static function hex2Str($hex)
	{
		// php version >= 5.4 have a hex2bin function, use it
		// if it exists
		if(function_exists("hex2bin"))
			return hex2bin($hex);

		$parts = str_split($hex, 2);
		$parts = array_map(function($v) {
				return chr(Core::hex2Dec($v));
		}, $parts);

		return implode("", $parts);
	}


	/**
	 * Converts Hex to Decimal
	 * This function just calls php's hexdec() function,  but I
	 * encapsulated it in this function to keep things uniform
	 * and have all possible conversion function available in
	 * the Cipher class
	 *
	 * @param string $hex A hex number to convert to decimal
	 * @return integer A decimal number
	 */
	public static function hex2Dec($hex)
	{
		return hexdec($hex);
	}


	/**
	 * Convert binary string (ie 00110110) to hex
	 *
	 * @param string $bin A binary string
	 * @return string A string representation of hexidecimal number
	 */
	public static function bin2Hex($bin)
	{
		$parts = str_split($bin, 8);

		$parts = array_map(function($v) {
			$v = str_pad($v, 8, "0", STR_PAD_LEFT);
			$v = dechex(bindec($v));
			return str_pad($v, 2, "0", STR_PAD_LEFT);
		}, $parts);

		return implode("", $parts);
	}


	/**
	 * Converts a binary representation (ie 01101011)  back to a string
	 *
	 * @param string $bin a binary representation string
	 * @return string A string of characters representing the binary
	 */
	public static function bin2Str($bin)
	{
		$hex = self::bin2Hex($bin);
		return self::hex2Str($hex);
	}


	/**
	 * Convert a binary string (ie: 01101011) to a decimal number
	 *
	 * @param string A string representation of a binary number
	 * @return integer The number converted from the binary string
	 */
	public static function bin2Dec($bin)
	{
		return bindec($bin);
	}


	/**
	 * Convert a string to hex
	 * This function calls the PHP bin2hex(), and is here
	 * for consistency with the other string functions
	 *
	 * @param string $str A string
	 * @return string A string representation of hexidecimal number
	 */
	public static function str2Hex($str)
	{
		return bin2hex($str);
	}


	/**
	 * Convert a string of characters to a decimal number
	 *
	 * @param string $str The string to convert to decimal
	 * @return integer The integer converted from the string
	 */
	public static function str2Dec($str)
	{
		$hex = self::str2Hex($str);
		return self::hex2Dec($hex);
	}


	/**
	 * Converts a string to binary representation (ie 01101011)
	 *
	 * @param string $str A string
	 * @return string A binary representation of the the string
	 */
	public static function str2Bin($str)
	{
		$hex = self::str2Hex($str);
		$parts = str_split($hex, 2);

		$parts = array_map(function($v) {
			return Core::hex2Bin($v);
		}, $parts);

		return implode("", $parts);
	}


	/**
	 * Converts Decimal to Hex
	 * This function just calls php's dechex() function,  but I
	 * encapsulated it in this function to keep things uniform
	 * and have all possible conversion function available in
	 * the Cipher class
	 *
	 * The parameter $req_bytes will pad the return hex with NULL (00)
	 * until the hex represents the number of bytes given to $req_bytes
	 * This is because dechex() drops null bytes from the Hex, which may
	 * be needed in some cases
	 *
	 * @param integer $dec A decimal number to convert
	 * @param integer $req_bytes Optional, forces the string to be at least
	 *	$req_bytes in size, this is needed because on occasion left most null bytes
	 *	are dropped in dechex(), causing the string to have a shorter byte
	 *	size than the initial integer.
	 * @return string A hexidecimal representation of the decimal number
	 */
	public static function dec2Hex($dec, $req_bytes = 0)
	{
		$hex = dechex($dec);

		// if we do not have an even number of hex characters
		// append a 0 to the beginning. dechex() drops leading 0's
		if(strlen($hex) % 2)
			$hex = "0$hex";

		// if the number of bytes in the hex is less than
		// what we need it to be, add null bytes to the
		// front of the hex to padd it to the required size
		if(($req_bytes * 2) > strlen($hex))
			$hex = str_pad($hex, ($req_bytes * 2), "0", STR_PAD_LEFT);

		return $hex;
	}


	/**
	 * Converts Decimal to Binary
	 * This function just calls php's decbin() function,  but I
	 * encapsulated it in this function to keep things uniform
	 * and have all possible conversion function available in
	 * the Cipher class
	 *
	 * @param integer $dec A decimal number to convert
	 * @param integer $req_bytes Optional, forces the string to be at least
	 *	$req_bytes in size, this is needed because on occasion left most null bytes
	 *	are dropped in dechex(), causing the string to have a shorter byte
	 *	size than the initial integer.
	 * @return string A binary representation of the decimal number
	 */
	public static function dec2Bin($dec, $req_bytes = 0)
	{
		$hex = self::dec2Hex($dec, $req_bytes);
		return self::hex2Bin($hex);
	}


	/**
	 * Convert a decimal to a string of bytes
	 *
	 * @param integer $dec A decimal number
	 * @param integer $req_bytes Optional, forces the string to be at least
	 *	$req_bytes in size, this is needed because on occasion left most null bytes
	 *	are dropped in dechex(), causing the string to have a shorter byte
	 *	size than the initial integer.
	 * @return string A string with the number of bytes equal to $dec
	 */
	public static function dec2Str($dec, $req_bytes = 0)
	{
		$hex = self::dec2Hex($dec, $req_bytes);
		return self::hex2Str($hex);
	}


	/**
	 * XORs two binary strings (representation of binary, ie 01101011),
	 * assumed to be equal length
	 *
	 * @param string $a A string that represents binary
	 * @param string $b A string that represents binary
	 * @return string A representation of binary
	 */
	public static function xorBin($a, $b)
	{
		$len_a = strlen($a);
		$len_b = strlen($b);
		$width = $len_a;

		// first determine if the two binary strings are the same length,
		// and if not get them to the same length
		if($len_a > $len_b)
		{
			$width = $len_a;
			$b = str_pad($b, $width, "0", STR_PAD_LEFT);
		}
		else if($len_a < $len_b)
		{
			$width = $len_b;
			$a = str_pad($a, $width, "0", STR_PAD_LEFT);
		}

		// fortunately PHP knows how to XOR each byte in a string
		// so we don't have to loop to do it
		$bin = self::bin2Str($a) ^ self::bin2Str($b);
		return self::str2Bin($bin);
	}


	/**
	 * ExclusiveOR hex values. Supports an unlimited number of parameters.
	 * The values are string representations of hex values
	 * IE: "0a1b2c3d" not 0x0a1b2c3d
	 *
	 * @param string Unlimited number parameters, each a string representation of hex
	 * @return string A string representation of the result in Hex
	 */
	public static function xorHex()
	{
		$hex   = func_get_args();
		$count = func_num_args();

		// we need a minimum of 2 values
		if($count < 2)
			return false;

		// first get all hex values to an even number
		array_walk($hex, function(&$val, $i){
			if(strlen($val) % 2)
				$val = "0".$val;
		});

		$res = 0;
		for($i = 0; $i < $count; ++$i)
		{
			// if this is the first loop, set the 'result' to the first
			// hex value
			if($i == 0)
				$res = $hex[0];
			else
			{
				// to make the code easier to follow
				$h1 = $res;
				$h2 = $hex[$i];

				// get lengths
				$len1 = strlen($h1);
				$len2 = strlen($h2);

				// now check that both hex values are the same length,
				// if not pad them with 0's until they are
				if($len1 > $len2)
					$h2 = str_pad($h2, $len1, "0", STR_PAD_LEFT);
				else if($len1 < $len2)
					$h1 = str_pad($h1, $len2, "0", STR_PAD_LEFT);

				// PHP knows how to XOR each byte in a string, so convert the
				// hex to a string, XOR, and convert back
				$res = self::hex2Str($h1) ^ self::hex2Str($h2);
				$res = self::str2Hex($res);
			}
		}

		return $res;
	}


	/**
	 * Forces an integer to be signed
	 *
	 * @param integer $int An integer
	 * @return integer An signed integer
	 */
	public static function sInt($int)
	{
		$arr = unpack("i", pack("i", $int));
		return $arr[1];
	}


	/**
	 * Forces an integer to be unsigned
	 *
	 * @param integer $int A signed integer
	 * @return integer An unsigned integer
	 */
	public static function uInt($int)
	{
		$arr = unpack("I", pack("I", $int));
		$ret = $arr[1];

		// On 32 bit platforms unpack() and pack() do not convert
		// from signed to unsigned properly all the time, it will return
		// the same negative number given to it, the work around is
		// to use sprintf().
		// Tested with php 5.3.x on Windows XP & Linux 32bit
		if($ret < 0)
			$ret = sprintf("%u", $ret) + 0; // convert from string to int

		return $ret;
	}


	/**
	 * Forces an integer to be a 32 bit signed integer
	 *
	 * @param integer $int An integer
	 * @return integer An signed 32 bit integer
	 */
	public static function sInt32($int)
	{
		if(PHP_INT_SIZE === 4) // 32 bit
			return self::sInt($int);
		else // PHP_INT_SIZE === 8 // 64 bit
		{
			$arr = unpack("l", pack("l", $int));
			return $arr[1];
		}
	}


	/**
	 * Force an integer to be a 32 bit unsigned integer
	 *
	 * @param integer $int An integer
	 * @return integer An unsigned 32 bit integer
	 */
	public static function uInt32($int)
	{
		if(PHP_INT_SIZE === 4) // 32 bit
			return self::uInt($int);
		else // PHP_INT_SIZE === 8  // 64 bit
		{
			$arr = unpack("L", pack("L", $int));
			return $arr[1];
		}
	}


	/**
	 * Converts an integer to the value for an signed char
	 *
	 * @param integer $int The integer to convert to a signed char
	 * @return integer A signed integer, representing a signed char
	 */
	public static function sChar($int)
	{
		$arr = unpack("c", pack("c", $int));
		return $arr[1];
	}


	/**
	 * Converts an integer to the value for an unsigned char
	 *
	 * @param integer $int The integer to convert to a unsigned char
	 * @return integer An unsigned integer, representing a unsigned char
	 */
	public static function uChar($int)
	{
		$arr = unpack("C", pack("C", $int));
		return $arr[1];
	}


	/**
	 * Rotates bits Left, appending the bits pushed off the left onto the right
	 *
	 * @param integer $n The integer to rotate bits to the left
	 * @param integer $shifts The number of shifts left to make
	 * @return integer The resulting value from the rotation
	 */
	public static function rotBitsLeft32($i, $shifts)
	{
		if($shifts <= 0)
			return $i;

		$shifts &= 0x1f; /* higher rotates would not bring anything */

		// this is causing problems on 32 bit platform
		//return self::uInt32(($i << $shifts) | ($i >> (32 - $shifts)));

		// so lets cheat: convert to binary string, rotate left, and
		// convert back to decimal
		$i = self::dec2Bin(self::uInt32($i), 4);
		$i = substr($i, $shifts).substr($i, 0, $shifts);
		return self::bin2Dec($i);

	}


	/**
	 * Rotates bits right, appending the bits pushed off the right onto the left
	 *
	 * @param integer $n The integer to rotate bits to the right
	 * @param integer $shifts The number of shifts right to make
	 * @return integer The resulting value from the rotation
	 */
	public static function rotBitsRight32($i, $shifts)
	{
		if($shifts <= 0)
			return $i;

		$shifts &= 0x1f; /* higher rotates would not bring anything */

		// this might cause problems on 32 bit platforms since rotBitsLeft32 was
		// having a problem with some bit shifts on 32 bits
		// return self::uInt32(($i >> $shifts) | ($i << (32 - $shifts)));

		// so lets cheat: convert to binary string, rotate right,
		// and convert back to decimal
		$i = self::dec2Bin($i, 4);
		$i = substr($i, (-1 * $shifts)).substr($i, 0, (-1 * $shifts));
		return self::bin2Dec($i);
	}


	/**
	 * Create a string of random bytes, used for creating an IV
	 * and a random key. See PHP_Crypt::createKey() and PHP_Crypt::createIV()
	 * There are 4 ways to auto generate random bytes by setting $src parameter
	 * PHP_Crypt::RAND - Default, uses mt_rand()
	 * PHP_Crypt::RAND_DEV_RAND - Unix only, uses /dev/random
	 * PHP_Crypt::RAND_DEV_URAND - Unix only, uses /dev/urandom
	 * PHP_Crypt::RAND_WIN_COM - Windows only, uses Microsoft's CAPICOM SDK
	 *
	 * @param string $src Optional, Use the $src to create the random bytes
	 * 	by default PHP_Crypt::RAND is used when $src is not specified
	 * @param integer $byte_len The length of the byte string to create
	 * @return string A random string of bytes
	 */
	public static function randBytes($src = PHP_Crypt::RAND, $byte_len = PHP_Crypt::RAND_DEFAULT_SZ)
	{
		$bytes = "";
		$err_msg = "";

		if($src == PHP_Crypt::RAND_DEV_RAND)
		{
			if(file_exists(PHP_Crypt::RAND_DEV_RAND))
				$bytes = file_get_contents(PHP_CRYPT::RAND_DEV_RAND, false, null, 0, $byte_len);
			else
				$err_msg = PHP_Crypt::RAND_DEV_RAND." not found";
		}
		else if($src == PHP_Crypt::RAND_DEV_URAND)
		{
			if(file_exists(PHP_Crypt::RAND_DEV_URAND))
				$bytes = file_get_contents(PHP_CRYPT::RAND_DEV_URAND, false, null, 0, $byte_len);
			else
				$err_msg = PHP_Crypt::RAND_DEV_URAND." not found";
		}
		else if($src == PHP_Crypt::RAND_WIN_COM)
		{
			if(extension_loaded('com_dotnet'))
			{
				// http://msdn.microsoft.com/en-us/library/aa388176(VS.85).aspx
				try
				{
					// request a random number in $byte_len bytes, returned
					// as base_64 encoded string. This is because PHP munges the
					// binary data on Windows
					$com = @new \COM("CAPICOM.Utilities.1");
					$bytes = $com->GetRandom($byte_len, 0);
				}
				catch(Exception $e)
				{
					$err_msg  = "Windows COM exception: ".$e->getMessage();
				}

				if(!$bytes)
					$err_msg  = "Windows COM failed to create random string of bytes";
			}
			else
				$err_msg = "The COM_DOTNET extension is not loaded";
		}

		// trigger a warning if something went wrong
		if($err_msg != "")
			trigger_error("$err_msg. Defaulting to PHP_Crypt::RAND", E_USER_WARNING);

		// if the random bytes where not created properly or PHP_Crypt::RAND was
		// passed as the $src param, create the bytes using mt_rand(). It's not
		// the most secure option but we have no other choice
		if(strlen($bytes) < $byte_len)
		{
			$bytes = "";

			// md5() hash a random number to get a 16 byte string, keep looping
			// until we have a string as long or longer than the ciphers block size
			for($i = 0; ($i * self::HASH_LEN) < $byte_len; ++$i)
				$bytes .= md5(mt_rand(), true);
		}

		// because $bytes may have come from mt_rand() or /dev/urandom which are not
		// cryptographically secure, lets add another layer of 'randomness' before
		// the final md5() below
		$bytes = str_shuffle($bytes);

		// md5() the $bytes to add extra randomness. Since md5() only returns
		// 16 bytes, we may need to loop to generate a string of $bytes big enough for
		// some ciphers which have a block size larger than 16 bytes
		$tmp = "";
		$loop = ceil(strlen($bytes) / self::HASH_LEN);
		for($i = 0; $i < $loop; ++$i)
			$tmp .= md5(substr($bytes, ($i * self::HASH_LEN), self::HASH_LEN), true);

		// grab the number of bytes equal to the requested $byte_len
		return substr($tmp, 0, $byte_len);
	}
}
?>