<?php

/************************************************************\

*

*		freeCap v1.4.1 Copyright 2005 Howard Yeend

*		www.puremango.co.uk

*

*    This file is part of freeCap.

*

*    freeCap 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 2 of the License, or

*    (at your option) any later version.

*

*    freeCap 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 freeCap; if not, write to the Free Software

*    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*

*

\************************************************************/

/**

 * A port of the freeCap captcha engine to Enano.

 */

class captcha_engine_freecap extends captcha_base

{

  var $site_tags = array();

  var $tag_pos = 0;

  var $rand_func = "mt_rand";

  var $seed_func = "mt_srand";

  var $hash_func = "sha1";

  var $output = "png";

  var $use_dict = false;

  var $dict_location = "";

  var $max_word_length = 7;

  var $col_type = 1;

  var $max_attempts = 20;

  var $font_locations = Array();

  var $bg_type = 3;

  var $blur_bg = false;

  var $bg_images = Array();

  var $merge_type = 0;

  var $morph_bg = true;

  var $im, $im2, $im3;

  var $font_size = 36;

  var $debug = false;

  function __construct($s, $r = false)

  {

    parent::__construct($s, $r);

    // try to avoid the 'free p*rn' method of CAPTCHA circumvention

    // see en.wikipedia.org/wiki/CAPTCHA for more info

    // $this->site_tags[0] = "To avoid spam, please do NOT enter the text if";

    // $this->site_tags[1] = "this site is not puremango.co.uk";

    // or more simply:

    // $site_tags[0] = "for use only on puremango.co.uk";

    // reword or add lines as you please

    // or if you don't want any text:

    $this->site_tags = array();

    // where to write the above:

    // 0=top

    // 1=bottom

    // 2=both

    $this->tag_pos = 1;

    // functions to call for random number generation

    // mt_rand produces 'better' random numbers

    // but if your server doesn't support it, it's fine to use rand instead

    $this->rand_func = "mt_rand";

    $this->seed_func = "mt_srand";

    // which type of hash to use?

    // possible values: "sha1", "md5", "crc32"

    // sha1 supported by PHP4.3.0+

    // md5 supported by PHP3+

    // crc32 supported by PHP4.0.1+

    $this->hash_func = $this->session_fetch('hash_func', 'sha1');

    // store in session so can validate in form processor

    // image type:

    // possible values: "jpg", "png", "gif"

    // jpg doesn't support transparency (transparent bg option ends up white)

    // png isn't supported by old browsers (see http://www.libpng.org/pub/png/pngstatus.html)

    // gif may not be supported by your GD Lib.

    $this->output = "png";

    // 0=generate pseudo-random string, true=use dictionary

    // dictionary is easier to recognise

    // - both for humans and computers, so use random string if you're paranoid.

    $this->use_dict = false;

    // if your server is NOT set up to deny web access to files beginning ".ht"

    // then you should ensure the dictionary file is kept outside the web directory

    // eg: if www.foo.com/index.html points to c:\website\www\index.html

    // then the dictionary should be placed in c:\website\dict.txt

    // test your server's config by trying to access the dictionary through a web browser

    // you should NOT be able to view the contents.

    // can leave this blank if not using dictionary

    $this->dict_location = ENANO_ROOT . "/includes/captcha/dicts/default.php";

    // used to calculate image width, and for non-dictionary word generation

    $this->max_word_length = 7;

    // text colour

    // 0=one random colour for all letters

    // 1=different random colour for each letter

    $this->col_type = 1;

    // maximum times a user can refresh the image

    // on a 6500 word dictionary, I think 15-50 is enough to not annoy users and make BF unfeasble.

    // further notes re: BF attacks in "avoid brute force attacks" section, below

    // on the other hand, those attempting OCR will find the ability to request new images

    // very useful; if they can't crack one, just grab an easier target...

    // for the ultra-paranoid, setting it to <5 will still work for most users

    $this->max_attempts = 20;

    // list of fonts to use

    // font size should be around 35 pixels wide for each character.

    // you can use my GD fontmaker script at www.puremango.co.uk to create your own fonts

    // There are other programs to can create GD fonts, but my script allows a greater

    // degree of control over exactly how wide each character is, and is therefore

    // recommended for 'special' uses. For normal use of GD fonts,

    // the GDFontGenerator @ http://www.philiplb.de is excellent for convering ttf to GD

    // the fonts included with freeCap *only* include lowercase alphabetic characters

    // so are not suitable for most other uses

    // to increase security, you really should add other fonts

    $this->font_locations = Array(

        //ENANO_ROOT . "/includes/captcha/fonts/assimila.ttf",

        //ENANO_ROOT . "/includes/captcha/fonts/elephant.ttf",

        //ENANO_ROOT . "/includes/captcha/fonts/swash_normal.ttf",

        //ENANO_ROOT . "/includes/captcha/fonts/.ttf",

        //ENANO_ROOT . "/includes/captcha/fonts/trekker_regular.ttf"

        ENANO_ROOT . "/includes/captcha/fonts/FreeMonoBold.ttf",

        ENANO_ROOT . "/includes/captcha/fonts/FreeSerifBold.ttf",

        ENANO_ROOT . "/includes/captcha/fonts/LiberationSans-Bold.ttf",

      );

    // background:

    // 0=transparent (if jpg, white)

    // 1=white bg with grid

    // 2=white bg with squiggles

    // 3=morphed image blocks

    // 'random' background from v1.3 didn't provide any extra security (according to 2 independent experts)

    // many thanks to http://ocr-research.org.ua and http://sam.zoy.org/pwntcha/ for testing

    // for jpgs, 'transparent' is white

    $this->bg_type = 3;

    // should we blur the background? (looks nicer, makes text easier to read, takes longer)

    $this->blur_bg = false;

    // for bg_type 3, which images should we use?

    // if you add your own, make sure they're fairly 'busy' images (ie a lot of shapes in them)

    $this->bg_images = Array(

        ENANO_ROOT . "/includes/captcha/pics/freecap_im1.jpg",

        ENANO_ROOT . "/includes/captcha/pics/freecap_im2.jpg",

        ENANO_ROOT . "/includes/captcha/pics/freecap_im3.jpg",

        ENANO_ROOT . "/includes/captcha/pics/freecap_im4.jpg",

        ENANO_ROOT . "/includes/captcha/pics/allyourbase.jpg"

      );

    // for non-transparent backgrounds only:

    // if 0, merges CAPTCHA with bg

    // if 1, write CAPTCHA over bg

    $this->merge_type = 0;

    // should we morph the bg? (recommend yes, but takes a little longer to compute)

    $this->morph_bg = true;

    // you shouldn't need to edit anything below this, but it's extensively commented if you do want to play

    // have fun, and email me with ideas, or improvements to the code (very interested in speed improvements)

    // hope this script saves some spam :-)

  }

  //////////////////////////////////////////////////////

  ////// Functions:

  //////////////////////////////////////////////////////

  function make_seed() {

  // from http://php.net/srand

      list($usec, $sec) = explode(' ', microtime());

      return (float) $sec + ((float) $usec * 100000);

  }

  function rand_color() {

    $rf =& $this->rand_func;

    if($this->bg_type==3)

    {

      // needs darker colour..

      return $rf(10,100);

    } else {

      return $rf(60,170);

    }

  }

  function myImageBlur($im)

  {

    // w00t. my very own blur function

    // in GD2, there's a gaussian blur function. bunch of bloody show-offs... :-)

    $width = imagesx($im);

    $height = imagesy($im);

    $temp_im = ImageCreateTrueColor($width,$height);

    $bg = ImageColorAllocate($temp_im,150,150,150);

    // preserves transparency if in orig image

    ImageColorTransparent($temp_im,$bg);

    // fill bg

    ImageFill($temp_im,0,0,$bg);

    // anything higher than 3 makes it totally unreadable

    // might be useful in a 'real' blur function, though (ie blurring pictures not text)

    $distance = 1;

    // use $distance=30 to have multiple copies of the word. not sure if this is useful.

    // blur by merging with itself at different x/y offsets:

    ImageCopyMerge($temp_im, $im, 0, 0, 0, $distance, $width, $height-$distance, 70);

    ImageCopyMerge($im, $temp_im, 0, 0, $distance, 0, $width-$distance, $height, 70);

    ImageCopyMerge($temp_im, $im, 0, $distance, 0, 0, $width, $height, 70);

    ImageCopyMerge($im, $temp_im, $distance, 0, 0, 0, $width, $height, 70);

    // remove temp image

    ImageDestroy($temp_im);

    return $im;

  }

  function sendImage($pic)

  {

    // output image with appropriate headers

    global $output,$im,$im2,$im3;

    // ENANO - obfuscation technique disabled

    // (this is for ethical reasons - ask dan at enanocms.org for information on why)

    // Basically it outputs an X-Captcha header showing freeCap version, etc. Unnecessary

    // header(base64_decode("WC1DYXB0Y2hhOiBmcmVlQ2FwIDEuNCAtIHd3dy5wdXJlbWFuZ28uY28udWs="));

    if ( $this->debug )

    {

      $x = imagesx($pic) - 70;

      $y = imagesy($pic) - 20;

      $code = $this->get_code();

      $red = ImageColorAllocateAlpha($pic, 0xAA, 0, 0, 72);

      ImageString($pic, 5, $x, $y, $code, $red);

      ImageString($pic, 5, 5, $y, "[debug mode]", $red);

    }

    switch($this->output)

    {

      // add other cases as desired

      case "jpg":

        header("Content-Type: image/jpeg");

        ImageJPEG($pic);

        break;

      case "gif":

        header("Content-Type: image/gif");

        ImageGIF($pic);

        break;

      case "png":

      default:

        header("Content-Type: image/png");

        ImagePNG($pic);

        break;

    }

    // kill GD images (removes from memory)

    ImageDestroy($this->im);

    ImageDestroy($this->im2);

    ImageDestroy($pic);

    if(!empty($this->im3))

    {

      ImageDestroy($this->im3);

    }

    exit();

  }

  function make_image()

  {

    //////////////////////////////////////////////////////

    ////// Create Images + initialise a few things

    //////////////////////////////////////////////////////

    // seed random number generator

    // PHP 4.2.0+ doesn't need this, but lower versions will

    $this->seed_func($this->make_seed());

    // how faded should the bg be? (100=totally gone, 0=bright as the day)

    // to test how much protection the bg noise gives, take a screenshot of the freeCap image

    // and take it into a photo editor. play with contrast and brightness.

    // If you can remove most of the bg, then it's not a good enough percentage

    switch($this->bg_type)

    {

      case 0:

        break;

      case 1:

      case 2:

        $bg_fade_pct = 65;

        break;

      case 3:

        $bg_fade_pct = 50;

        break;

    }

    // slightly randomise the bg fade

    $bg_fade_pct += $this->rand_func(-2,2);

    // read each font and get font character widths

    // $font_widths = Array();

    // for($i=0 ; $i<sizeof($this->font_locations) ; $i++)

    // {

    //   $handle = fopen($this->font_locations[$i],"r");

    //   // read header of GD font, up to char width

    //   $c_wid = fread($handle,15);

    //   $font_widths[$i] = ord($c_wid{8})+ord($c_wid{9})+ord($c_wid{10})+ord($c_wid{11});

    //   fclose($handle);

    // }

    // modify image width depending on maximum possible length of word

    // you shouldn't need to use words > 6 chars in length really.

    $width = ($this->max_word_length*($this->font_size+10)+75);

    $height = 90;

    $this->im = ImageCreateTrueColor($width, $height);

    $this->im2 = ImageCreateTrueColor($width, $height);

    ////////////////////////////////////////////////////////

    // GENERATE IMAGE                                     //

    ////////////////////////////////////////////////////////

    $word = $this->get_code();

    // save hash of word for comparison

    // using hash so that if there's an insecurity elsewhere (eg on the form processor),

    // an attacker could only get the hash

    // also, shared servers usually give all users access to the session files

    // echo `ls /tmp`; and echo `more /tmp/someone_elses_session_file`; usually work

    // so even if your site is 100% secure, someone else's site on your server might not be

    // hence, even if attackers can read the session file, they can't get the freeCap word

    // (though most hashes are easy to brute force for simple strings)

    //////////////////////////////////////////////////////

    ////// Fill BGs and Allocate Colours:

    //////////////////////////////////////////////////////

    // set tag colour

    // have to do this before any distortion

    // (otherwise colour allocation fails when bg type is 1)

    $tag_col = ImageColorAllocate($this->im,10,10,10);

    $site_tag_col2 = ImageColorAllocate($this->im2,0,0,0);

    // set debug colours (text colours are set later)

    $debug = ImageColorAllocate($this->im, 255, 0, 0);

    $debug2 = ImageColorAllocate($this->im2, 255, 0, 0);

    // set background colour (can change to any colour not in possible $text_col range)

    // it doesn't matter as it'll be transparent or coloured over.

    // if you're using bg_type 3, you might want to try to ensure that the color chosen

    // below doesn't appear too much in any of your background images.

    $bg = ImageColorAllocate($this->im, 254, 254, 254);

    $bg2 = ImageColorAllocate($this->im2, 254, 254, 254);

    // set transparencies

    ImageColorTransparent($this->im,$bg);

    // im2 transparent to allow characters to overlap slightly while morphing

    ImageColorTransparent($this->im2,$bg2);

    // fill backgrounds

    ImageFill($this->im,0,0,$bg);

    ImageFill($this->im2,0,0,$bg2);

    if($this->bg_type!=0)

    {

      // generate noisy background, to be merged with CAPTCHA later

      // any suggestions on how best to do this much appreciated

      // sample code would be even better!

      // I'm not an OCR expert (hell, I'm not even an image expert; puremango.co.uk was designed in MsPaint)

      // so the noise models are based around my -guesswork- as to what would make it hard for an OCR prog

      // ideally, the character obfuscation would be strong enough not to need additional background noise

      // in any case, I hope at least one of the options given here provide some extra security!

      $this->im3 = ImageCreateTrueColor($width,$height);

      $temp_bg = ImageCreateTrueColor($width*1.5,$height*1.5);

      $bg3 = ImageColorAllocate($this->im3,255,255,255);

      ImageFill($this->im3,0,0,$bg3);

      $temp_bg_col = ImageColorAllocate($temp_bg,255,255,255);

      ImageFill($temp_bg,0,0,$temp_bg_col);

      // we draw all noise onto temp_bg

      // then if we're morphing, merge from temp_bg to im3

      // or if not, just copy a $widthx$height portion of $temp_bg to $this->im3

      // temp_bg is much larger so that when morphing, the edges retain the noise.

      if($this->bg_type==1)

      {

        // grid bg:

        // draw grid on x

        for($i=$this->rand_func(6,20) ; $i<$width*2 ; $i+=$this->rand_func(10,25))

        {

          ImageSetThickness($temp_bg,$this->rand_func(2,6));

          $text_r = $this->rand_func(100,150);

          $text_g = $this->rand_func(100,150);

          $text_b = $this->rand_func(100,150);

          $text_colour3 = ImageColorAllocate($temp_bg, $text_r, $text_g, $text_b);

          ImageLine($temp_bg,$i,0,$i,$height*2,$text_colour3);

        }

        // draw grid on y

        for($i=$this->rand_func(6,20) ; $i<$height*2 ; $i+=$this->rand_func(10,25))

        {

          ImageSetThickness($temp_bg,$this->rand_func(2,6));

          $text_r = $this->rand_func(100,150);

          $text_g = $this->rand_func(100,150);

          $text_b = $this->rand_func(100,150);

          $text_colour3 = ImageColorAllocate($temp_bg, $text_r, $text_g, $text_b);

          ImageLine($temp_bg,0,$i,$width*2, $i ,$text_colour3);

        }

      } else if($this->bg_type==2) {

        // draw squiggles!

        $bg3 = ImageColorAllocate($this->im3,255,255,255);

        ImageFill($this->im3,0,0,$bg3);

        ImageSetThickness($temp_bg,4);

        for($i=0 ; $i<strlen($word)+1 ; $i++)

        {

          $text_r = $this->rand_func(100,150);

          $text_g = $this->rand_func(100,150);

          $text_b = $this->rand_func(100,150);

          $text_colour3 = ImageColorAllocate($temp_bg, $text_r, $text_g, $text_b);

          $points = Array();

          // draw random squiggle for each character

          // the longer the loop, the more complex the squiggle

          // keep random so OCR can't say "if found shape has 10 points, ignore it"

          // each squiggle will, however, be a closed shape, so OCR could try to find

          // line terminations and start from there. (I don't think they're that advanced yet..)

          for($j=1 ; $j<$this->rand_func(5,10) ; $j++)

          {

            $points[] = $this->rand_func(1*(20*($i+1)),1*(50*($i+1)));

            $points[] = $this->rand_func(30,$height+30);

          }

          ImagePolygon($temp_bg,$points,intval(sizeof($points)/2),$text_colour3);

        }

      } else if($this->bg_type==3) {

        // take random chunks of $this->bg_images and paste them onto the background

        for($i=0 ; $i<sizeof($this->bg_images) ; $i++)

        {

          // read each image and its size

          $temp_im[$i] = ImageCreateFromJPEG($this->bg_images[$i]);

          $temp_width[$i] = imagesx($temp_im[$i]);

          $temp_height[$i] = imagesy($temp_im[$i]);

        }

        $blocksize = $this->rand_func(20,60);

        for($i=0 ; $i<$width*2 ; $i+=$blocksize)

        {

          // could randomise blocksize here... hardly matters

          for($j=0 ; $j<$height*2 ; $j+=$blocksize)

          {

            $this->image_index = $this->rand_func(0,sizeof($temp_im)-1);

            $cut_x = $this->rand_func(0,$temp_width[$this->image_index]-$blocksize);

            $cut_y = $this->rand_func(0,$temp_height[$this->image_index]-$blocksize);

            ImageCopy($temp_bg, $temp_im[$this->image_index], $i, $j, $cut_x, $cut_y, $blocksize, $blocksize);

          }

        }

        for($i=0 ; $i<sizeof($temp_im) ; $i++)

        {

          // remove bgs from memory

          ImageDestroy($temp_im[$i]);

        }

        // for debug:

        //sendImage($temp_bg);

      }

      // for debug:

      //sendImage($this->im3);

      if($this->morph_bg)

      {

        // morph background

        // we do this separately to the main text morph because:

        // a) the main text morph is done char-by-char, this is done across whole image

        // b) if an attacker could un-morph the bg, it would un-morph the CAPTCHA

        // hence bg is morphed differently to text

        // why do we morph it at all? it might make it harder for an attacker to remove the background

        // morph_chunk 1 looks better but takes longer

        // this is a different and less perfect morph than the one we do on the CAPTCHA

        // occasonally you get some dark background showing through around the edges

        // it doesn't need to be perfect as it's only the bg.

        $morph_chunk = $this->rand_func(1,5);

        $morph_y = 0;

        for($x=0 ; $x<$width ; $x+=$morph_chunk)

        {

          $morph_chunk = $this->rand_func(1,5);

          $morph_y += $this->rand_func(-1,1);

          ImageCopy($this->im3, $temp_bg, $x, 0, $x+30, 30+$morph_y, $morph_chunk, $height*2);

        }

        ImageCopy($temp_bg, $this->im3, 0, 0, 0, 0, $width, $height);

        $morph_x = 0;

        for($y=0 ; $y<=$height; $y+=$morph_chunk)

        {

          $morph_chunk = $this->rand_func(1,5);

          $morph_x += $this->rand_func(-1,1);

          ImageCopy($this->im3, $temp_bg, $morph_x, $y, 0, $y, $width, $morph_chunk);

        }

      } else {

        // just copy temp_bg onto im3

        ImageCopy($this->im3,$temp_bg,0,0,30,30,$width,$height);

      }

      ImageDestroy($temp_bg);

      if($this->blur_bg)

      {

        $this->myImageBlur($this->im3);