<?php
/******************************************************************
Projectname: CAPTCHA 2
Version: 0.9
Author: Cristian Navalici cristian.navalici at gmail dot com
Last modified: 22-feb-2007
Copyright (C): 2007 Cristian Navalici, All Rights Reserved
* GNU General Public License (Version 2, June 1991)
*
* This program 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.
*
* 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.
Description:
This class can generate CAPTCHAs, see README for more details!
28.02.2007 - added Windows specifications for MCRYPT_RAND
******************************************************************/
class Captcha {
// here you can make some adjustments
private $font_size = 24; // if GD2 in points / GD1 in pixels
private $font = 'gibberish.ttf';
private $img_height = 70;
private $save_path = 'gdtest'; // without trailing slash
private $secret_key = 'Insert a complicated string here';
private $use_windows = 0; // 1 - if you'll use windows 0 - if don't
// until here
private $gd_enabled = true;
private $allow_jpg_output = false;
private $allow_png_output = false;
private $length;
//======================================================================
// CONSTRUCTOR
//======================================================================
function __construct ($length = 6, $type = 'png', $letter = '') {
$check_gd = gd_info();
if (!$check_gd['GD Version']) {
$this->gd_enabled = false;
}
// check for JPG capability
if ($check_gd['JPG Support']) {
$this->allow_jpg_output = true;
}
// check for PNG capability
if ($check_gd['PNG Support']) {
$this->allow_png_output = true;
}
if(!session_id()){
session_start();
} else {
session_regenerate_id();
}
}
//======================================================================
// MAIN FUNCTION: createCaptcha
// create a captcha image based on supplied arguments
// if GD is not enabled it switch to TEXT MODE
//
// @arg: $length (int) - length of generated string
// $type (string) - type of generated picture (jpg or png)
// $draw_lines (bool) - optional lines on picture
// @return: none (picture saved)
//======================================================================
public function createCaptcha($length = 6, $type = 'png', $draw_lines = 'true') {
if ($this->gd_enabled) {
$img_length = $length * ($this->font_size+5);
$image = imagecreatetruecolor($img_length, $this->img_height) or die("Cannot Initialize new GD image stream");;
// ----- TRANSFORMATIONS PART -----------------------------------
// set background
$bgcolor = imagecolorallocate($image, 255, 255, 255);
imagefill($image,0,0,$bgcolor);
$random_pixels = $img_length * $this->img_height / 2;
for ($i = 0; $i < $random_pixels; $i++) {
$color_pixel = ImageColorAllocate($image, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
ImageSetPixel($image, rand(0, $img_length), rand(0, $this->img_height), $color_pixel);
}
// smooth image
imagefilter($image, IMG_FILTER_SMOOTH, 10);
// add text
$gens = $this->stringGenerator($length);
for ($i = 0 ; $i < $length ; $i++) {
$stringcolor = imagecolorallocate($image, mt_rand(0, 180), mt_rand(0, 100), mt_rand(0, 180));
imagettftext($image, $this->font_size, mt_rand(-40,40), 10 + (($this->font_size + 4) * $i), mt_rand(40, 60),
$stringcolor,
$this->font,
$gens{$i});
}
// default draw lines
if ((bool)$draw_lines) {
$img = $this->drawLines ($image, $img_length);
} else {
$img = $image;
}
// ----- EOS TRANSFORMATIONS PART -----------------------------------
//create name for saved files (must be unique)
$sname = $this->save_path .'/'. substr(time(), -5);
// if you want a jpeg or png but the option is not available
// automated change to the other type
if ((!$this->allow_jpg_output) && (!$this->allow_png_output)) {
echo "We have a problem! We can't save jpg or png either. Check your GD configuration.";
exit (0);
} else {
if ($type == 'jpeg') {
if ($this->allow_jpg_output) {
$sname .= '.jpg';
imagejpeg($img, $sname);
} else {
$sname .= '.png';
imagepng($img, $sname);
}
} elseif ($type == 'png') {
if ($this->allow_png_output) {
$sname .= '.png';
imagepng($img, $sname);
} else {
$sname .= '.jpg';
imagejpeg($img, $sname);
}
}
} // if-else
$_SESSION['savedfile'] = $sname;
imagedestroy($img);
} else {
// if GD in not installed we switch to text mode
echo $this->stringGenerator($length);
}// ifelse ($gd_enabled)
}
//======================================================================
// SHOW CAPTCHA
// function to show captcha image on website page
//
// @arg: none
// @return: echo image
//======================================================================
public function showCaptcha() {
echo "<img src='" .$_SESSION['savedfile']. "' border='0' alt='captcha code' title='captcha code' />";
}
//======================================================================
// VERIFY CAPTCHA
//
// @arg: $txt (string) - entered string from user
// @return: bool (true / false)
//======================================================================
public function verifyCaptcha($txt) {
// remove generated image
if (is_file($_SESSION['savedfile'])) unlink ($_SESSION['savedfile']);
// DECRYPTION PART
$decrypted_data = $this->cryptDecrypt($_SESSION['captcha'], 'DECRYPT');
return (strcmp ($txt, $decrypted_data) == 0) ? true : false;
}
//============================================================================================
// P R I V A T E F U N C T I O N S
//============================================================================================
//======================================================================
// STRING GENERATOR
// generates a random string of alphanumerics for captcha
//
// @arg: $length (integer) - length of generated string
// @return: $gen_string (string) - generated string (mixture of alphanumerics)
//======================================================================
private function stringGenerator($length) {
// mix some letters and some digits
$alphanumerics = array_merge(range('A', 'Z'), range(2, 9));
$alphanumerics_len = count($alphanumerics) - 1;
$gen_string = '';
for ($i = 0; $i < $length; $i++) {
$gen_string .= $alphanumerics[mt_rand(0, $alphanumerics_len)];
}
// ENCRYPTION PART
$encrypted_data = $this->cryptDecrypt($gen_string, 'CRYPT');
$_SESSION['captcha'] = $encrypted_data;
return $gen_string;
}
//======================================================================
// DRAW SOME LINES ON PICTURE
// draw some lines to image to make it more complicated
//
// @arg: $image (resource)
// $imagelength (int)
// @return: $image (resource) - an image painted with lines
//======================================================================
private function drawLines($image, $imagelength) {
for ($i =0 ; $i<4 ; $i++) {
// define random colors for lines
$cColor = imagecolorallocate($image,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
// first coodinates are in the first half of image
$x0coordonate = mt_rand (0, 0.5 * $imagelength);
$y0coordonate = mt_rand (0, $this->img_height);
// second coodinates are in the second half of image
$x1coordonate = mt_rand (0.5 * $imagelength,$imagelength);
$y1coordonate = mt_rand (0, $this->img_height);
imageline ($image, $x0coordonate, $y0coordonate, $x1coordonate, $y1coordonate,$cColor );
imageline ($image, $x0coordonate-1, $y0coordonate-1, $x1coordonate-1, $y1coordonate-1,$cColor );
}
return $image;
}
//======================================================================
// CRYPT OR DECRYPT A STRING
//
// we encrypt the string with libmcrypt > 2.4.x
// @arg: $txt (string) string in clear text
// $flag (constant) CRYPT | DECRYPT
// @return: $result (string) encoded string
//======================================================================
private function cryptDecrypt($txt, $flag) {
$td = mcrypt_module_open('tripledes', '', 'ecb', '');
// windows OS supports only MCRYPT_RAND
if (!$this->use_windows) {
$iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_DEV_RANDOM);
} else {
srand ( ( (int) ( (double) microtime() * 1000003)) ); // good seed 1000003 is prime number
$iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
}
$ks = mcrypt_enc_get_key_size($td);
$key = substr(md5($this->secret_key), 0, $ks);
// Intialize encryption
mcrypt_generic_init($td, $key, $iv);
switch ($flag) {
case 'CRYPT': $result = mcrypt_generic($td, $txt); break;
case 'DECRYPT': $result = trim (mdecrypt_generic($td, $txt)); break;
}
// Terminate encryption handler
mcrypt_generic_deinit($td);
mcrypt_module_close($td);
return $result;
}
} // EOF class
?>
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