<?php

/*

 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between

 * Version 1.1.2 (Caoineag alpha 2)

 * Copyright (C) 2006-2007 Dan Fuhry

 * diffiehellman.php - Diffie Hellman key exchange and supporting functions

 *

 * This program is Free Software; you can redistribute and/or modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2 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 details.

 */

/**

 * Class to handle math operations that require the use of >32-bit integers.

 */

class EnanoMath

{

  var $api = 'gmp';

  var $limb = 16;

  function __construct()

  {

    /*

    // big_int support is untested.

    if ( extension_loaded('big_int') )

    {

      $this->api = 'bigint';

    }

    else

    */

    if ( function_exists('gmp_init') )

    {

      $this->api = 'gmp';

    }

    else if ( function_exists('bcpow') )

    {

      $this->api = 'bcmath';

    }

    else

    {

      throw new Exception('dh_err_not_supported');

    }

  }

  function powmod($base, $pow, $mod)

  {

    switch($this->api)

    {

      case 'bigint':

        return ( pow($base, $pow) % $mod );

        break;

      case 'gmp':

        return ( function_exists('gmp_powm') ) ? gmp_powm($base, $pow, $mod) : gmp_mod(gmp_pow($base, $pow), $mod);

        break;

      case 'bcmath':

        return ( function_exists('bcpowmod') ) ? bcpowmod($base, $pow, $mod) : bcmod( bcpow($base, $pow), $mod );

        break;

    }

  }

  function random($len)

  {

    switch($this->api)

    {

      case 'gmp':

        return gmp_random($len);

        break;

      case 'bcmath':

        return $this->_bcmath_random($len);

        break;

      case 'bigint':

        return $this->_bigint_random($len);

        break;

    }

  }

  function _bcmath_random($len)

  {

    $len = ( $this->limb / 2 ) * $len;

    $chars = '0123456789abcdef';

    $ret = '';

    for ( $i = 0; $i < $len; $i++ )

    {

      $chid = mt_rand ( 0, strlen($chars) - 1 );

      $chr = $chars{$chid};

      $ret .= $chr;

    }

    return $this->basecon($ret, 16, 10);

  }

  function _bigint_random($len)

  {

    $len = ( $this->limb / 2 ) * $len;

    $chars = '0123456789abcdef';

    $ret = '';

    for ( $i = 0; $i < $len; $i++ )

    {

      $chid = mt_rand ( 0, strlen($chars) - 1 );

      $chr = $chars{$chid};

      $ret .= $chr;

    }

    return $this->basecon($ret, 16, 10);

  }

  function basecon($int, $from, $to)

  {

    switch($this->api)

    {

      case 'gmp':

        return gmp_strval(gmp_init($int, $from), $to);

        break;

      case 'bcmath':

        return $this->_bcmath_baseconv($int, $from, $to);

        break;

      case 'bigint':

        return base_convert($int, $from, $to);

        break;

    }

  }

  function str($res, $base = 10)

  {

    switch($this->api)

    {

      case 'bigint':

      case 'bcmath':

        return strval($this->basecon($res, 10, $base));

        break;

      case 'gmp':

        return gmp_strval($res, $base);

        break;

    }

  }

  function compare($v1, $v2)

  {

    switch($this->api)

    {

      case 'bigint':

        return ( $v1 === $v2 );

        break;

      case 'bcmath':

        return ( bccomp($v1, $v2) === 0 );

        break;

      case 'gmp':

        return ( gmp_cmp($v1, $v2) === 0 );

        break;

    }

  }

  function _bcmath_baseconv($int, $from, $to)

  {

    if ( $from != 10 )

      $int = $this->_bcmath_base2dec($int, $from);

    if ( $to != 10 )

      $int = $this->_bcmath_dec2base($int, $to);

    return $int;

  }

  // from us.php.net/bc:

  // convert a decimal value to any other base value

  function _bcmath_dec2base($dec,$base,$digits=FALSE) {

      if($base<2 or $base>256) die("Invalid Base: ".$base);

      bcscale(0);

      $value="";

      if(!$digits) $digits=$this->_bcmath_digits($base);

      while($dec>$base-1) {

          $rest=bcmod($dec,$base);

          $dec=bcdiv($dec,$base);

          $value=$digits[$rest].$value;

      }

      $value=$digits[intval($dec)].$value;

      return (string) $value;

  }

  // convert another base value to its decimal value

  function _bcmath_base2dec($value,$base,$digits=FALSE) {

      if($base<2 or $base>256) die("Invalid Base: ".$base);

      bcscale(0);

      if($base<37) $value=strtolower($value);

      if(!$digits) $digits=$this->_bcmath_digits($base);

      $size=strlen($value);

      $dec="0";

      for($loop=0;$loop<$size;$loop++) {

          $element=strpos($digits,$value[$loop]);

          $power=bcpow($base,$size-$loop-1);

          $dec=bcadd($dec,bcmul($element,$power));

      }

      return (string) $dec;

  }

  function _bcmath_digits($base) {

      if($base>64) {

          $digits="";

          for($loop=0;$loop<256;$loop++) {

              $digits.=chr($loop);

          }

      } else {

          $digits ="0123456789abcdefghijklmnopqrstuvwxyz";

          $digits.="ABCDEFGHIJKLMNOPQRSTUVWXYZ-_";

      }

      $digits=substr($digits,0,$base);

      return (string) $digits;

  }

}

/**

 * The Diffie-Hellman key exchange protocol

 */

$GLOBALS['_math'] = new EnanoMath();

// Our prime number as a base for operations.

$GLOBALS['dh_prime'] = '82818079787776757473727170696867666564636261605958575655545352515049484746454443424140393837363534333231302928272625242322212019181716151413121110987654321';

// g, a primitive root used as an exponent

// (2 and 5 are acceptable, but BigInt is faster with odd numbers)

$GLOBALS['dh_g'] = '5';

/**

 * Generates a Diffie-Hellman private key

 * @return string(BigInt)

 */

function dh_gen_private()

{

  global $_math;

  return $_math->random(256);

}

/**

 * Calculates the public key from the private key

 * @param string(BigInt)

 * @return string(BigInt)

 */

function dh_gen_public($b)

{

  global $_math, $dh_g, $dh_prime;

  return $_math->powmod($dh_g, $b, $dh_prime);

}

/**

 * Calculates the shared secret.

 * @param string(BigInt) Our private key

 * @param string(BigInt) Remote party's public key

 * @return string(BigInt)

 */

function dh_gen_shared_secret($a, $B)

{

  global $_math, $dh_g, $dh_prime;

  return $_math->powmod($B, $a, $dh_prime);

}

/*

SHA-256 algorithm - ported from Javascript

Copyright (c) 2003-2004, Angel Marin

All rights reserved.

Portions copyright (c) 2008 Dan Fuhry.

Redistribution and use in source and binary forms, with or without modification,

are permitted provided that the following conditions are met:

 * Redistributions of source code must retain the above copyright notice, this

   list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright notice,

   this list of conditions and the following disclaimer in the documentation

   and/or other materials provided with the distribution.

 * Neither the name of the <ORGANIZATION> nor the names of its contributors may

   be used to endorse or promote products derived from this software without

   specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,

BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE

OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

OF THE POSSIBILITY OF SUCH DAMAGE.

*/

class SHA256

{

  var $chrsz = 8;  /* bits per input character. 8 - ASCII; 16 - Unicode  */

  function safe_add ($x, $y) {

    $lsw = ($x & 0xFFFF) + ($y & 0xFFFF);

    $msw = ($x >> 16) + ($y >> 16) + ($lsw >> 16);

    return ($msw << 16) | ($lsw & 0xFFFF);

  }

  function rshz($X, $n)

  {

    // equivalent to $X >>> $n in javascript

    // pulled from http://www.tapouillo.com/firefox_extension/sourcecode.txt, public domain

    $z = hexdec(80000000); 

    if ($z & $X) 

    { 

        $X = ($X>>1); 

        $X &= (~$z); 

        $X |= 0x40000000; 

        $X = ($X>>($n-1)); 

    } 

    else 

    { 

        $X = ($X>>$n); 

    } 

    return $X; 

  }

  function S ($X, $n) {return ( $this->rshz($X, $n) ) | ($X << (32 - $n));}

  function R ($X, $n) {return ( $this->rshz($X, $n) );}

  function Ch($x, $y, $z)  {return (($x & $y) ^ ((~$x) & $z));}

  function Maj($x, $y, $z) {return (($x & $y) ^ ($x & $z) ^ ($y & $z));}

  function Sigma0256($x) {return ($this->S($x, 2)  ^ $this->S($x, 13) ^ $this->S($x, 22));}

  function Sigma1256($x) {return ($this->S($x, 6)  ^ $this->S($x, 11) ^ $this->S($x, 25));}

  function Gamma0256($x) {return ($this->S($x, 7)  ^ $this->S($x, 18) ^ $this->R($x, 3));}

  function Gamma1256($x) {return ($this->S($x, 17) ^ $this->S($x, 19) ^ $this->R($x, 10));}

  function core_sha256 ($m, $l) {

      $K = Array(0x428A2F98,0x71374491,0xB5C0FBCF,0xE9B5DBA5,0x3956C25B,0x59F111F1,0x923F82A4,0xAB1C5ED5,0xD807AA98,0x12835B01,0x243185BE,0x550C7DC3,0x72BE5D74,0x80DEB1FE,0x9BDC06A7,0xC19BF174,0xE49B69C1,0xEFBE4786,0xFC19DC6,0x240CA1CC,0x2DE92C6F,0x4A7484AA,0x5CB0A9DC,0x76F988DA,0x983E5152,0xA831C66D,0xB00327C8,0xBF597FC7,0xC6E00BF3,0xD5A79147,0x6CA6351,0x14292967,0x27B70A85,0x2E1B2138,0x4D2C6DFC,0x53380D13,0x650A7354,0x766A0ABB,0x81C2C92E,0x92722C85,0xA2BFE8A1,0xA81A664B,0xC24B8B70,0xC76C51A3,0xD192E819,0xD6990624,0xF40E3585,0x106AA070,0x19A4C116,0x1E376C08,0x2748774C,0x34B0BCB5,0x391C0CB3,0x4ED8AA4A,0x5B9CCA4F,0x682E6FF3,0x748F82EE,0x78A5636F,0x84C87814,0x8CC70208,0x90BEFFFA,0xA4506CEB,0xBEF9A3F7,0xC67178F2);

      $HASH = Array(0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19);

      $W = Array(64);

      /* append padding */

      $m[$l >> 5] |= 0x80 << (24 - $l % 32);

      $m[(($l + 64 >> 9) << 4) + 15] = $l;

      for ( $i = 0; $i<count($m); $i+=16 ) {

          $a = $HASH[0];

          $b = $HASH[1];

          $c = $HASH[2];

          $d = $HASH[3];

          $e = $HASH[4];

          $f = $HASH[5];

          $g = $HASH[6];

          $h = $HASH[7];

          for ( $j = 0; $j<64; $j++)

          {

              if ( $j < 16 )

              {

                $W[$j] = ( isset($m[$j + $i]) ) ? $m[$j + $i] : 0;

              }

              else

              {

                $W[$j] = $this->safe_add(

                  $this->safe_add(

                    $this->safe_add(

                      $this->Gamma1256($W[$j - 2]), $W[$j - 7]),

                    $this->Gamma0256($W[$j - 15])),

                  $W[$j - 16]);

              }

              $T1 = $this->safe_add(

                $this->safe_add(

                  $this->safe_add(

                    $this->safe_add($h, $this->Sigma1256($e)

                      ),

                    $this->Ch($e, $f, $g)),

                  $K[$j]),

                $W[$j]);

              $T2 = $this->safe_add($this->Sigma0256($a), $this->Maj($a, $b, $c));

              $h = $g;

              $g = $f;

              $f = $e;

              $e = $this->safe_add($d, $T1);

              $d = $c;

              $c = $b;

              $b = $a;

              $a = $this->safe_add($T1, $T2);

          }

          $HASH[0] = $this->safe_add($a, $HASH[0]);

          $HASH[1] = $this->safe_add($b, $HASH[1]);

          $HASH[2] = $this->safe_add($c, $HASH[2]);

          $HASH[3] = $this->safe_add($d, $HASH[3]);

          $HASH[4] = $this->safe_add($e, $HASH[4]);

          $HASH[5] = $this->safe_add($f, $HASH[5]);

          $HASH[6] = $this->safe_add($g, $HASH[6]);

          $HASH[7] = $this->safe_add($h, $HASH[7]);

      }

      return $HASH;

  }

  function str2binb ($str) {

    $bin = Array();

    for ( $i = 0; $i < strlen($str); $i++ )

    {

      $byte = ord($str{$i});

      $block = floor($i / 4);

      $stage = $i % 4;

      if ( $stage == 0 )

      {

        $bin[$block] = $byte;

      }

      else

      {

        $bin[$block] <<= 8;

        $bin[$block] |= $byte;

      }

    }

    while ( $stage < 3 )

    {

      $stage++;

      $bin[$block] <<= 8;

    }

    return $bin;

  }

  function byte2hex($byte)

  {

    $b = dechex(ord($byte));

    return ( strlen($b) < 2 ) ? "0$b" : $b;

  }

  function binb2hex ($binarray) {

    $hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase */

    $hex_tab = $hexcase ? "0123456789ABCDEF" : "0123456789abcdef";

    $str = "";