/securimage.php

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<?php

// error_reporting(E_ALL); ini_set('display_errors', 1); // uncomment this line for debugging

/**
 * Project:  Securimage: A PHP class dealing with CAPTCHA images, audio, and validation
 * File:     securimage.php
 *
 * Copyright (c) 2018, Drew Phillips
 * All rights reserved.
 *
 * 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.
 *
 * 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 HOLDER 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.
 *
 * Any modifications to the library should be indicated clearly in the source code
 * to inform users that the changes are not a part of the original software.
 *
 * @link https://www.phpcaptcha.org Securimage Homepage
 * @link https://www.phpcaptcha.org/latest.zip Download Latest Version
 * @link https://github.com/dapphp/securimage GitHub page
 * @link https://www.phpcaptcha.org/Securimage_Docs/ Online Documentation
 * @copyright 2018 Drew Phillips
 * @author Drew Phillips <drew@drew-phillips.com>
 * @version 3.6.8 (May 2020)
 * @package Securimage
 *
 */

/**

 ChangeLog
 3.6.8
 - Ability to fix open_basedir warning by setting Securimage::$lame_binary_path = ''; (#63)
 - Fix division by zero if captcha length is 1 (#88)
 - Add options to getCaptchaHtml input_required (#82) and js_url (#95)
 - PHP 7.3/7.4 compat fixes (#101)
 - Project status: https://github.com/dapphp/securimage/issues/99
 - Improve handling of multi-byte wordlists (#87)

 3.6.7
 - Merge changes from 4.0.1-nextgen
 - Increase captcha difficulty
 - Add setting "use_text_angles". Enable to select a random angle and step value and draw each character at an angle in a step like fashion
 - Add setting "use_random_spaces". Enable to insert 1-3 spaces between a random group of letters some of the time
 - Add setting "use_random_baseline". Enable to draw letters at a random height instead of centered.  Each character's baseline is a step up or down from the previous (not totally random)
 - Add setting "use_random_boxes". Enable to draw a bounding box around one or more characters at random
 - Improve performance of captcha generation when using distortion (perturbation) and noise (noise_level)
 - Enable image anti-aliasing
 - Make all text functions multibyte safe when using UTF-8 or other encodings for charsets and wordlists (using mbstring)

 3.6.6
 - Not critical: Fix potential HTML injection in example form via HTTP_USER_AGENT (CVE-2017-14077)

 3.6.5
 - Fix regex in replaceElements in securimage.js
 - Update examples
 - Exclude certain examples from Git autogenerated archives

 3.6.4
 - Fix XSS vulnerability in example_form.ajax.php (Discovered by RedTeam. advisory rt-sa-2016-002)
 - Update example_form.ajax.php to use Securimage::getCaptchaHtml()

 3.6.3
 - Add support for multibyte wordlist files
 - Fix code generation issues with UTF-8 charsets
 - Add parameter to getCaptchaHtml() method to control display components of captcha HTML
 - Fix database audio storage issue with multiple namespaces

 3.6.2
 - Support HTTP range requests with audio playback (iOS requirement)
 - Add optional config.inc.php for storing global configuration settings

 3.6.1
 - Fix copyElement bug in securimage.js for IE Flash fallback

 3.6
 - Implement CAPTCHA audio using HTML5 <audio> with optional Flash fallback
 - Support MP3 audio using LAME MP3 Encoder (Internet Explorer 9+ does not support WAV format in <audio> tags)
 - Add getCaptchaHtml() options to support full framework integration (ruifil)

 3.5.4
 - Fix email validation code in example form files
 - Fix backslashes in getCaptchaHtml for img attribute on Windows systems

 3.5.3
 - Add options for audio button to getCaptchaHtml(), fix urlencoding of flash parameters that was breaking button

 3.5.2

 - Add Securimage::getCaptchaHtml() for getting automatically generated captcha html code
 - Option for using SoX to add effects to captcha audio to make identification by neural networks more difficult
 - Add setNamespace() method
 - Add getTimeToSolve() method
 - Add session_status() check so session still starts if one had previously been opened and closed
 - Add .htaccess file to audio directory to deny access; update audio files
 - Option to skip checking of database tables during connection
 - Add composer.json to package, submit to packagist
 - Add font_ratio variable to determine size of font (github.com/wilkor)
 - Add hint if sqlite3 database is not writeable.  Improve database error handling, add example database options to securimage_play.php
 - Fixed issue regarding database storage and math captcha breaking audio output (github.com/SoftwareAndOutsourcing)

 3.5.1
 - Fix XSS vulnerability in example_form.php (discovered by Gjoko Krstic - <gjoko@zeroscience.mk>)

 3.5
 - Release new version
 - MB string support for charlist
 - Modify audio file path to use language directories
 - Changed default captcha appearance

 3.2RC4
 - Add MySQL, PostgreSQL, and SQLite3 support for database storage
 - Deprecate "use_sqlite_db" option and remove SQLite2/sqlite_* functions
 - Add new captcha type that displays 2 dictionary words on one image
 - Update examples

 3.2RC3
 - Fix canSendHeaders() check which was breaking if a PHP startup error was issued

 3.2RC2
 - Add error handler (https://github.com/dapphp/securimage/issues/15)
 - Fix flash examples to use the correct value name for audio parameter

 3.2RC1
 - New audio captcha code.  Faster, fully dynamic audio, full WAV support
   (Paul Voegler, Drew Phillips) <http://voegler.eu/pub/audio>
 - New Flash audio streaming button.  User defined image and size supported
 - Additional options for customizing captcha (noise_level, send_headers,
   no_exit, no_session, display_value
 - Add captcha ID support.  Uses sqlite and unique captcha IDs to track captchas,
   no session used
 - Add static methods for creating and validating captcha by ID
 - Automatic clearing of old codes from SQLite database

 3.0.3Beta
 - Add improved mixing function to WavFile class (Paul Voegler)
 - Improve performance and security of captcha audio (Paul Voegler, Drew Phillips)
 - Add option to use random file as background noise in captcha audio
 - Add new securimage options for audio files

 3.0.2Beta
 - Fix issue with session variables when upgrading from 2.0 - 3.0
 - Improve audio captcha, switch to use WavFile class, make mathematical captcha audio work

 3.0.1
 - Bugfix: removed use of deprecated variable in addSignature method that would cause errors with display_errors on

 3.0
 - Rewrite class using PHP5 OOP
 - Remove support for GD fonts, require FreeType
 - Remove support for multi-color codes
 - Add option to make codes case-sensitive
 - Add namespaces to support multiple captchas on a single page or page specific captchas
 - Add option to show simple math problems instead of codes
 - Remove support for mp3 files due to vulnerability in decoding mp3 audio files
 - Create new flash file to stream wav files instead of mp3
 - Changed to BSD license

 2.0.2
 - Fix pathing to make integration into libraries easier (Nathan Phillip Brink ohnobinki@ohnopublishing.net)

 2.0.1
 - Add support for browsers with cookies disabled (requires php5, sqlite) maps users to md5 hashed ip addresses and md5 hashed codes for security
 - Add fallback to gd fonts if ttf support is not enabled or font file not found (Mike Challis http://www.642weather.com/weather/scripts.php)
 - Check for previous definition of image type constants (Mike Challis)
 - Fix mime type settings for audio output
 - Fixed color allocation issues with multiple colors and background images, consolidate allocation to one function
 - Ability to let codes expire after a given length of time
 - Allow HTML color codes to be passed to Securimage_Color (suggested by Mike Challis)

 2.0.0
 - Add mathematical distortion to characters (using code from HKCaptcha)
 - Improved session support
 - Added Securimage_Color class for easier color definitions
 - Add distortion to audio output to prevent binary comparison attack (proposed by Sven "SavageTiger" Hagemann [insecurity.nl])
 - Flash button to stream mp3 audio (Douglas Walsh www.douglaswalsh.net)
 - Audio output is mp3 format by default
 - Change font to AlteHaasGrotesk by yann le coroller
 - Some code cleanup

 1.0.4 (unreleased)
 - Ability to output audible codes in mp3 format to stream from flash

 1.0.3.1
 - Error reading from wordlist in some cases caused words to be cut off 1 letter short

 1.0.3
 - Removed shadow_text from code which could cause an undefined property error due to removal from previous version

 1.0.2
 - Audible CAPTCHA Code wav files
 - Create codes from a word list instead of random strings

 1.0
 - Added the ability to use a selected character set, rather than a-z0-9 only.
 - Added the multi-color text option to use different colors for each letter.
 - Switched to automatic session handling instead of using files for code storage
 - Added GD Font support if ttf support is not available.  Can use internal GD fonts or load new ones.
 - Added the ability to set line thickness
 - Added option for drawing arced lines over letters
 - Added ability to choose image type for output

 */


/**
 * Securimage CAPTCHA Class.
 *
 * A class for creating and validating secure CAPTCHA images and audio.
 *
 * The class contains many options regarding appearance, security, storage of
 * captcha data and image/audio generation options.
 *
 * @package    Securimage
 * @subpackage classes
 * @author     Drew Phillips <drew@drew-phillips.com>
 *
 */
class Securimage
{
    // All of the public variables below are securimage options
    // They can be passed as an array to the Securimage constructor, set below,
    // or set from securimage_show.php and securimage_play.php

    /**
     * Constant for rendering captcha as a JPEG image
     * @var int
     */
    const SI_IMAGE_JPEG = 1;

    /**
     * Constant for rendering captcha as a PNG image (default)
     * @var int
     */

    const SI_IMAGE_PNG  = 2;
    /**
     * Constant for rendering captcha as a GIF image
     * @var int
     */
    const SI_IMAGE_GIF  = 3;

    /**
     * Constant for generating a normal alphanumeric captcha based on the
     * character set
     *
     * @see Securimage::$charset charset property
     * @var int
     */
    const SI_CAPTCHA_STRING     = 0;

    /**
     * Constant for generating a captcha consisting of a simple math problem
     *
     * @var int
     */
    const SI_CAPTCHA_MATHEMATIC = 1;

    /**
     * Constant for generating a word based captcha using 2 words from a list
     *
     * @var int
     */
    const SI_CAPTCHA_WORDS      = 2;

    /**
     * MySQL option identifier for database storage option
     *
     * @var string
     */
    const SI_DRIVER_MYSQL   = 'mysql';

    /**
     * PostgreSQL option identifier for database storage option
     *
     * @var string
     */
    const SI_DRIVER_PGSQL   = 'pgsql';

    /**
     * SQLite option identifier for database storage option
     *
     * @var string
     */
    const SI_DRIVER_SQLITE3 = 'sqlite';

    /**
     * getCaptchaHtml() display constant for HTML Captcha Image
     *
     * @var integer
     */
    const HTML_IMG   = 1;

    /**
     * getCaptchaHtml() display constant for HTML5 Audio code
     *
     * @var integer
     */
    const HTML_AUDIO = 2;

    /**
     * getCaptchaHtml() display constant for Captcha Input text box
     *
     * @var integer
     */
    const HTML_INPUT = 4;

    /**
     * getCaptchaHtml() display constant for Captcha Text HTML label
     *
     * @var integer
     */
    const HTML_INPUT_LABEL = 8;

    /**
     * getCaptchaHtml() display constant for HTML Refresh button
     *
     * @var integer
     */
    const HTML_ICON_REFRESH = 16;

    /**
     * getCaptchaHtml() display constant for all HTML elements (default)
     *
     * @var integer
     */
    const HTML_ALL = 0xffffffff;

    /*%*********************************************************************%*/
    // Properties

    /**
     * The width of the captcha image
     * @var int
     */
    public $image_width = 215;

    /**
     * The height of the captcha image
     * @var int
     */
    public $image_height = 80;

    /**
     * Font size is calculated by image height and this ratio.  Leave blank for
     * default ratio of 0.4.
     *
     * Valid range: 0.1 - 0.99.
     *
     * Depending on image_width, values > 0.6 are probably too large and
     * values < 0.3 are too small.
     *
     * @var float
     */
    public $font_ratio;

    /**
     * The type of the image, default = png
     *
     * @see Securimage::SI_IMAGE_PNG SI_IMAGE_PNG
     * @see Securimage::SI_IMAGE_JPEG SI_IMAGE_JPEG
     * @see Securimage::SI_IMAGE_GIF SI_IMAGE_GIF
     * @var int
     */
    public $image_type   = self::SI_IMAGE_PNG;

    /**
     * The background color of the captcha
     * @var Securimage_Color|string
     */
    public $image_bg_color = '#ffffff';

    /**
     * The color of the captcha text
     * @var Securimage_Color|string
     */
    public $text_color     = '#707070';

    /**
     * The color of the lines over the captcha
     * @var Securimage_Color|string
     */
    public $line_color     = '#707070';

    /**
     * The color of the noise that is drawn
     * @var Securimage_Color|string
     */
    public $noise_color    = '#707070';

    /**
     * How transparent to make the text.
     *
     * 0 = completely opaque, 100 = invisible
     *
     * @var int
     */
    public $text_transparency_percentage = 20;

    /**
     * Whether or not to draw the text transparently.
     *
     * true = use transparency, false = no transparency
     *
     * @var bool
     */
    public $use_transparent_text         = true;

    /**
     * The length of the captcha code
     * @var int
     */
    public $code_length    = 6;

    /**
     * Display random spaces in the captcha text on the image
     *
     * @var bool true to insert random spacing between groups of letters
     */
    public $use_random_spaces  = false;

    /**
     * Draw each character at an angle with random starting angle and increase/decrease per character
     * @var bool true to use random angles, false to draw each character normally
     */
    public $use_text_angles = false;

    /**
     * Instead of centering text vertically in the image, the baseline of each character is
     * randomized in such a way that the next character is drawn slightly higher or lower than
     * the previous in a step-like fashion.
     *
     * @var bool true to use random baselines, false to center text in image
     */
    public $use_random_baseline = false;

    /**
     * Draw a bounding box around some characters at random.  20% of the time, random boxes
     * may be drawn around 0 or more characters on the image.
     *
     * @var bool  true to randomly draw boxes around letters, false not to
     */
    public $use_random_boxes = false;

    /**
     * Whether the captcha should be case sensitive or not.
     *
     * Not recommended, use only for maximum protection.
     *
     * @var bool
     */
    public $case_sensitive = false;

    /**
     * The character set to use for generating the captcha code
     * @var string
     */
    public $charset        = 'abcdefghijkmnopqrstuvwxzyABCDEFGHJKLMNPQRSTUVWXZY0123456789';

    /**
     * How long in seconds a captcha remains valid, after this time it will be
     * considered incorrect.
     *
     * @var int
     */
    public $expiry_time    = 900;

    /**
     * The session name securimage should use.
     *
     * Only use if your application uses a custom session name (e.g. Joomla).
     * It is recommended to set this value here so it is used by all securimage
     * scripts (i.e. securimage_show.php)
     *
     * @var string
     */
    public $session_name   = null;

    /**
     * true to use the wordlist file, false to generate random captcha codes
     * @var bool
     */
    public $use_wordlist   = false;

    /**
     * The level of distortion.
     *
     * 0.75 = normal, 1.0 = very high distortion
     *
     * @var double
     */
    public $perturbation = 0.85;

    /**
     * How many lines to draw over the captcha code to increase security
     * @var int
     */
    public $num_lines    = 5;

    /**
     * The level of noise (random dots) to place on the image, 0-10
     * @var int
     */
    public $noise_level  = 2;

    /**
     * The signature text to draw on the bottom corner of the image
     * @var string
     */
    public $image_signature = '';

    /**
     * The color of the signature text
     * @var Securimage_Color|string
     */
    public $signature_color = '#707070';

    /**
     * The path to the ttf font file to use for the signature text.
     * Defaults to $ttf_file (AHGBold.ttf)
     *
     * @see Securimage::$ttf_file
     * @var string
     */
    public $signature_font;

    /**
     * No longer used.
     *
     * Use an SQLite database to store data (for users that do not support cookies)
     *
     * @var bool
     * @see Securimage::$database_driver database_driver property
     * @deprecated 3.2RC4
     */
    public $use_sqlite_db = false;

    /**
     * Use a database backend for code storage.
     * Provides a fallback to users with cookies disabled.
     * Required when using captcha IDs.
     *
     * @see Securimage::$database_driver
     * @var bool
     */
    public $use_database = false;

    /**
     * Whether or not to skip checking if Securimage tables exist when using a
     * database.
     *
     * Turn this to true once database functionality is working to improve
     * performance.
     *
     * @var bool true to not check if captcha_codes tables are set up, false
     * to check (and create if necessary)
     */
    public $skip_table_check = false;

    /**
     * Database driver to use for database support.
     * Allowable values: *mysql*, *pgsql*, *sqlite*.
     * Default: sqlite
     *
     * @var string
     */
    public $database_driver = self::SI_DRIVER_SQLITE3;

    /**
     * Database host to connect to when using mysql or postgres
     *
     * On Linux use "localhost" for Unix domain socket, otherwise uses TCP/IP
     *
     * Does not apply to SQLite
     *
     * @var string
     */
    public $database_host   = 'localhost';

    /**
     * Database username for connection (mysql, postgres only)
     * Default is an empty string
     *
     * @var string
     */
    public $database_user   = '';

    /**
     * Database password for connection (mysql, postgres only)
     * Default is empty string
     *
     * @var string
     */
    public $database_pass   = '';

    /**
     * Name of the database to select (mysql, postgres only)
     *
     * @see Securimage::$database_file for SQLite
     * @var string
     */
    public $database_name   = '';

    /**
     * Database table where captcha codes are stored
     *
     * Note: Securimage will attempt to create this table for you if it does
     * not exist.  If the table cannot be created, an E_USER_WARNING is emitted
     *
     * @var string
     */
    public $database_table  = 'captcha_codes';

    /**
     * Fully qualified path to the database file when using SQLite3.
     *
     * This value is only used when $database_driver == sqlite and does
     * not apply when no database is used, or when using MySQL or PostgreSQL.
     *
     * On *nix, file must have permissions of 0666.
     *
     * **Make sure the directory containing this file is NOT web accessible**
     *
     * @var string
     */
    public $database_file;

    /**
     * The type of captcha to create.
     *
     * Either alphanumeric based on *charset*, a simple math problem, or an
     * image consisting of 2 words from the word list.
     *
     * @see Securimage::SI_CAPTCHA_STRING SI_CAPTCHA_STRING
     * @see Securimage::SI_CAPTCHA_MATHEMATIC SI_CAPTCHA_MATHEMATIC
     * @see Securimage::SI_CAPTCHA_WORDS SI_CAPTCHA_WORDS
     * @see Securimage::$charset charset property
     * @see Securimage::$wordlist_file wordlist_file property
     * @var int
     */
    public $captcha_type  = self::SI_CAPTCHA_STRING; // or self::SI_CAPTCHA_MATHEMATIC, or self::SI_CAPTCHA_WORDS;

    /**
     * The captcha namespace used for having multiple captchas on a page or
     * to separate captchas from differen forms on your site.
     * Example:
     *
     *     <?php
     *     // use <img src="securimage_show.php?namespace=contact_form">
     *     // or manually in securimage_show.php
     *     $img->setNamespace('contact_form');
     *
     *     // in form validator
     *     $img->setNamespace('contact_form');
     *     if ($img->check($code) == true) {
     *         echo "Valid!";
     *     }
     *
     * @var string
     */
    public $namespace;

    /**
     * The TTF font file to use to draw the captcha code.
     *
     * Leave blank for default font AHGBold.ttf
     *
     * @var string
     */
    public $ttf_file;

    /**
     * The path to the wordlist file to use.
     *
     * Leave blank for default words/words.txt
     *
     * @var string
     */
    public $wordlist_file;

    /**
     * Character encoding of the wordlist file.
     * Requires PHP Multibyte String (mbstring) support.
     * Allows word list to contain characters other than US-ASCII (requires compatible TTF font).
     *
     * @var string The character encoding (e.g. UTF-8, UTF-7, EUC-JP, GB2312)
     * @see http://php.net/manual/en/mbstring.supported-encodings.php
     * @since 3.6.3
     */
    public $wordlist_file_encoding = null;

    /**
     * The directory to scan for background images, if set a random background
     * will be chosen from this folder
     *
     * @var string
     */
    public $background_directory;

    /**
     * No longer used
     *
     * The path to the SQLite database file to use
     *
     * @deprecated 3.2RC4
     * @see Securimage::$database_file database_file property
     * @var string
     */
    public $sqlite_database;

    /**
     * The path to the audio files to be used for audio captchas.
     *
     * Can also be set in securimage_play.php
     *
     * Example:
     *
     *     $img->audio_path = '/home/yoursite/public_html/securimage/audio/en/';
     *
     * @var string
     */
    public $audio_path;

    /**
     * Use SoX (The Swiss Army knife of audio manipulation) for audio effects
     * and processing.
     *
     * Using SoX should make it more difficult for bots to solve audio captchas
     *
     * @see Securimage::$sox_binary_path sox_binary_path property
     * @var bool true to use SoX, false to use PHP
     */
    public $audio_use_sox = false;

    /**
     * The path to the SoX binary on your system
     *
     * @var string
     */
    public $sox_binary_path = '/usr/bin/sox';

    /**
     * The path to the lame (mp3 encoder) binary on your system
     * Static so that Securimage::getCaptchaHtml() has access to this value.
     *
     * @since 3.6
     * @var string
     */
    public static $lame_binary_path = '/usr/bin/lame';

    /**
     * The path to the directory containing audio files that will be selected
     * randomly and mixed with the captcha audio.
     *
     * @var string
     */
    public $audio_noise_path;

    /**
     * Whether or not to mix background noise files into captcha audio
     *
     * Mixing random background audio with noise can help improve security of
     * audio captcha.
     *
     * Default: securimage/audio/noise
     *
     * @since 3.0.3
     * @see Securimage::$audio_noise_path audio_noise_path property
     * @var bool true = mix, false = no
     */
    public $audio_use_noise;

    /**
     * The method and threshold (or gain factor) used to normalize the mixing
     * with background noise.
     *
     * See http://www.voegler.eu/pub/audio/ for more information.
     *
     * Default: 0.6
     *
     * Valid:
     *     >= 1
     *     Normalize by multiplying by the threshold (boost - positive gain).
     *     A value of 1 in effect means no normalization (and results in clipping).
     *
     *     <= -1
     *     Normalize by dividing by the the absolute value of threshold (attenuate - negative gain).
     *     A factor of 2 (-2) is about 6dB reduction in volume.
     *
     *     [0, 1)  (open inverval - not including 1)
     *     The threshold above which amplitudes are comressed logarithmically.
     *     e.g. 0.6 to leave amplitudes up to 60% "as is" and compressabove.
     *
     *     (-1, 0) (open inverval - not including -1 and 0)
     *     The threshold above which amplitudes are comressed linearly.
     *     e.g. -0.6 to leave amplitudes up to 60% "as is" and compress above.
     *
     * @since 3.0.4
     * @var float
     */
    public $audio_mix_normalization = 0.8;

    /**
     * Whether or not to degrade audio by introducing random noise.
     *
     * Current research shows this may not increase the security of audible
     * captchas.
     *
     * Default: true
     *
     * @since 3.0.3
     * @var bool
     */
    public $degrade_audio;

    /**
     * Minimum delay to insert between captcha audio letters in milliseconds
     *
     * @since 3.0.3
     * @var float
     */
    public $audio_gap_min = 0;

    /**
     * Maximum delay to insert between captcha audio letters in milliseconds
     *
     * @since 3.0.3
     * @var float
     */
    public $audio_gap_max = 3000;

    /**
     * The file path for logging errors from audio (default __DIR__)
     *
     * @var string|null
     */
    public $log_path = null;

    /**
     * The name of the log file for logging audio errors
     *
     * @var string|null (defualt si_error.log)
     */
    public $log_file = null;

    /**
     * Captcha ID if using static captcha
     * @var string Unique captcha id
     */
    protected static $_captchaId = null;

    /**
     * The GD image resource of the captcha image
     *
     * @var resource
     */
    protected $im;

    /**
     * A temporary GD image resource of the captcha image for distortion
     *
     * @var resource
     */
    protected $tmpimg;

    /**
     * The background image GD resource
     * @var string
     */
    protected $bgimg;

    /**
     * Scale factor for magnification of distorted captcha image
     *
     * @var int
     */
    protected $iscale = 2;

    /**
     * Absolute path to securimage directory.
     *
     * This is calculated at runtime
     *
     * @var string
     */
    public $securimage_path = null;

    /**
     * The captcha challenge value.
     *
     * Either the case-sensitive/insensitive word captcha, or the solution to
     * the math captcha.
     *
     * @var string|bool Captcha challenge value
     */
    protected $code;

    /**
     * The display value of the captcha to draw on the image
     *
     * Either the word captcha or the math equation to present to the user
     *
     * @var string Captcha display value to draw on the image
     */
    protected $code_display;

    /**
     * Alternate text to draw as the captcha image text
     *
     * A value that can be passed to the constructor that can be used to
     * generate a captcha image with a given value.
     *
     * This value does not get stored in the session or database and is only
     * used when calling Securimage::show().
     *
     * If a display_value was passed to the constructor and the captcha image
     * is generated, the display_value will be used as the string to draw on
     * the captcha image.
     *
     * Used only if captcha codes are generated and managed by a 3rd party
     * app/library
     *
     * @var string Captcha code value to display on the image
     */
    public $display_value;

    /**
     * Captcha code supplied by user [set from Securimage::check()]
     *
     * @var string
     */
    protected $captcha_code;

    /**
     * Time (in seconds) that the captcha was solved in (correctly or incorrectly).
     *
     * This is from the time of code creation, to when validation was attempted.
     *
     * @var int
     */
    protected $_timeToSolve = 0;

    /**
     * Flag that can be specified telling securimage not to call exit after
     * generating a captcha image or audio file
     *
     * @var bool If true, script will not terminate; if false script will terminate (default)
     */
    protected $no_exit;

    /**
     * Flag indicating whether or not a PHP session should be started and used
     *
     * @var bool If true, no session will be started; if false, session will be started and used to store data (default)
     */
    protected $no_session;

    /**
     * Flag indicating whether or not HTTP headers will be sent when outputting
     * captcha image/audio
     *
     * @var bool If true (default) headers will be sent, if false, no headers are sent
     */
    protected $send_headers;

    /**
     * PDO connection when a database is used
     *
     * @var PDO|bool
     */
    protected $pdo_conn;

    /**
     * The GD color for the background color
     *
     * @var int
     */
    protected $gdbgcolor;

    /**
     * The GD color for the text color
     *
     * @var int
     */
    protected $gdtextcolor;

    /**
     * The GD color for the line color
     *
     * @var int
     */
    protected $gdlinecolor;

    /**
     * The GD color for the signature text color
     *
     * @var int
     */
    protected $gdsignaturecolor;

    /**
     * Create a new securimage object, pass options to set in the constructor.
     *
     * The object can then be used to display a captcha, play an audible captcha, or validate a submission.
     *
     * @param array $options  Options to initialize the class.  May be any class property.
     *
     *     $options = array(
     *         'text_color' => new Securimage_Color('#013020'),
     *         'code_length' => 5,
     *         'num_lines' => 5,
     *         'noise_level' => 3,
     *         'font_file' => Securimage::getPath() . '/custom.ttf'
     *     );
     *
     *     $img = new Securimage($options);
     *
     */
    public function __construct($options = array())
    {
        $this->securimage_path = dirname(__FILE__);

        if (!is_array($options)) {
            trigger_error(
                    '$options passed to Securimage::__construct() must be an array.  ' .
                    gettype($options) . ' given',
                    E_USER_WARNING
            );
            $options = array();
        }

        if (function_exists('mb_internal_encoding')) {
            mb_internal_encoding('UTF-8');
        }

        // check for and load settings from custom config file
        $config_file = null;

        if (file_exists(dirname(__FILE__) . '/config.inc.php')) {
            $config_file = dirname(__FILE__) . '/config.inc.php';
        }
        if (isset($options['config_file']) && file_exists($options['config_file'])) {
            $config_file = $options['config_file'];
        }

        if ($config_file) {
            $settings = include $config_file;

            if (is_array($settings)) {
                $options = array_merge($settings, $options);
            }
        }

        if (is_array($options) && sizeof($options) > 0) {
            foreach($options as $prop => $val) {
                if ($prop == 'captchaId') {
                    Securimage::$_captchaId = $val;
                    $this->use_database     = true;
                } else if ($prop == 'use_sqlite_db') {
                    trigger_error("The use_sqlite_db option is deprecated, use 'use_database' instead", E_USER_NOTICE);
                } else {
                    $this->$prop = $val;
                }
            }
        }

        $this->image_bg_color  = $this->initColor($this->image_bg_color,  '#ffffff');
        $this->text_color      = $this->initColor($this->text_color,      '#616161');
        $this->line_color      = $this->initColor($this->line_color,      '#616161');
        $this->noise_color     = $this->initColor($this->noise_color,     '#616161');
        $this->signature_color = $this->initColor($this->signature_color, '#616161');

        if (is_null($this->ttf_file)) {
            $this->ttf_file = $this->securimage_path . '/AHGBold.ttf';
        }

        $this->signature_font = $this->ttf_file;

        if (is_null($this->wordlist_file)) {
            $this->wordlist_file = $this->securimage_path . '/words/words.txt';
        }

        if (is_null($this->database_file)) {
            $this->database_file = $this->securimage_path . '/database/securimage.sq3';
        }

        if (is_null($this->audio_path)) {
            $this->audio_path = $this->securimage_path . '/audio/en/';
        }

        if (is_null($this->audio_noise_path)) {
            $this->audio_noise_path = $this->securimage_path . '/audio/noise/';
        }

        if (is_null($this->audio_use_noise)) {
            $this->audio_use_noise = true;
        }

        if (is_null($this->degrade_audio)) {
            $this->degrade_audio = true;
        }

        if (is_null($this->code_length) || (int)$this->code_length < 1) {
            $this->code_length = 6;
        }

        if (is_null($this->perturbation) || !is_numeric($this->perturbation)) {
            $this->perturbation = 0.75;
        }

        if (is_null($this->namespace) || !is_string($this->namespace)) {
            $this->namespace = 'default';
        }

        if (is_null($this->no_exit)) {
            $this->no_exit = false;
        }

        if (is_null($this->no_session)) {
            $this->no_session = false;
        }

        if (is_null($this->send_headers)) {
            $this->send_headers = true;
        }

        if (is_null($this->log_path)) {
            $this->log_path = __DIR__;
        }

        if (is_null($this->log_file)) {
            $this->log_file = 'securimage.error_log';
        }

        if ($this->no_session != true) {
            // Initialize session or attach to existing
            if ( session_id() == '' || (function_exists('session_status') && PHP_SESSION_NONE == session_status()) ) { // no session has been started yet (or it was previousy closed), which is needed for validation
                if (!is_null($this->session_name) && trim($this->session_name) != '') {
                    session_name(trim($this->session_name)); // set session name if provided
                }
                session_start();
            }
        }
    }

    /**
     * Return the absolute path to the Securimage directory.
     *
     * @return string The path to the securimage base directory
     */
    public static function getPath()
    {
        return dirname(__FILE__);
    }

    /**
     * Generate a new captcha ID or retrieve the current ID (if exists).
     *
     * @param bool $new If true, generates a new challenge and returns and ID.  If false, the existing captcha ID is returned, or null if none exists.
     * @param array $options Additional options to be passed to Securimage.
     *   $options must include database settings if they are not set directly in securimage.php
     *
     * @return null|string Returns null if no captcha id set and new was false, or the captcha ID
     */
    public static function getCaptchaId($new = true, array $options = array())
    {
        if (is_null($new) || (bool)$new == true) {
            $id = sha1(uniqid($_SERVER['REMOTE_ADDR'], true));
            $opts = array('no_session'    => true,
                          'use_database'  => true);
            if (sizeof($options) > 0) $opts = array_merge($options, $opts);
            $si = new self($opts);
            Securimage::$_captchaId = $id;
            $si->createCode();

            return $id;
        } else {
            return Securimage::$_captchaId;
        }
    }

    /**
     * Validate a captcha code input against a captcha ID
     *
     * @param string $id       The captcha ID to check
     * @param string $value    The captcha value supplied by the user
     * @param array  $options  Array of options to construct Securimage with.
     *   Options must include database options if they are not set in securimage.php
     *
     * @see Securimage::$database_driver
     * @return bool true if the code was valid for the given captcha ID, false if not or if database failed to open
     */
    public static function checkByCaptchaId($id, $value, array $options = array())
    {
        $opts = array('captchaId'    => $id,
                      'no_session'   => true,
                      'use_database' => true);

        if (sizeof($options) > 0) $opts = array_merge($options, $opts);

        $si = new self($opts);

        if ($si->openDatabase()) {
            $code = $si->getCodeFromDatabase();

            if (is_array($code)) {
                $si->code         = $code['code'];
                $si->code_display = $code['code_disp'];
            }

            if ($si->check($value)) {
                $si->clearCodeFromDatabase();

                return true;
            } else {
                return false;
            }
        } else {
            return false;
        }
    }


    /**
     * Generates a new challenge and serves a captcha image.
     *
     * Appropriate headers will be sent to the browser unless the *send_headers* option is false.
     *
     * @param string $background_image The absolute or relative path to the background image to use as the background of the captcha image.
     *
     *     $img = new Securimage();
     *     $img->code_length = 6;
     *     $img->num_lines   = 5;
     *     $img->noise_level = 5;
     *
     *     $img->show(); // sends the image and appropriate headers to browser
     *     exit;
     */
    public function show($background_image = '')
    {
        set_error_handler(array(&$this, 'errorHandler'));

        if($background_image != '' && is_readable($background_image)) {
            $this->bgimg = $background_image;
        }

        $this->doImage();
    }

    /**
     * Checks a given code against the correct value from the session and/or database.
     *
     * @param string $code  The captcha code to check
     *
     *     $code = $_POST['code'];
     *     $img  = new Securimage();
     *     if ($img->check($code) == true) {
     *         $captcha_valid = true;
     *     } else {
     *         $captcha_valid = false;
     *     }
     *
     * @return bool true if the given code was correct, false if not.
     */
    public function check($code)
    {
        if (!is_string($code)) {
            trigger_error("The \$code parameter passed to Securimage::check() must be a string, " . gettype($code) . " given", E_USER_NOTICE);
            $code = '';
        }

        $this->code_entered = $code;
        $this->validate();
        return $this->correct_code;
    }

    /**
     * Returns HTML code for displaying the captcha image, audio button, and form text input.
     *
     * Options can be specified to modify the output of the HTML.  Accepted options:
     *
     *     'securimage_path':
     *         Optional: The URI to where securimage is installed (e.g. /securimage)
     *     'show_image_url':
     *         Path to the securimage_show.php script (useful when integrating with a framework or moving outside the securimage directory)
     *         This will be passed as a urlencoded string to the <img> tag for outputting the captcha image
     *     'audio_play_url':
     *         Same as show_image_url, except this indicates the URL of the audio playback script
     *     'image_id':
     *          A string that sets the "id" attribute of the captcha image (default: captcha_image)
     *     'image_alt_text':
     *         The alt text of the captcha image (default: CAPTCHA Image)
     *     'show_audio_button':
     *         true/false  Whether or not to show the audio button (default: true)
     *     'disable_flash_fallback':)
     *         Allow only HTML5 audio and disable Flash fallback
     *     'show_refresh_button':
     *         true/false  Whether or not to show a button to refresh the image (default: true)
     *     'audio_icon_url':
     *         URL to the image used for showing the HTML5 audio icon
     *     'js_url':
     *         URL to the javascript file
     *     'icon_size':
     *         Size (for both height & width) in pixels of the audio and refresh buttons
     *     'show_text_input':
     *         true/false  Whether or not to show the text input for the captcha (default: true)
     *     'refresh_alt_text':
     *         Alt text for the refresh image (default: Refresh Image)
     *     'refresh_title_text':
     *         Title text for the refresh image link (default: Refresh Image)
     *     'input_id':
     *         A string that sets the "id" attribute of the captcha text input (default: captcha_code)
     *     'input_name':
     *         A string that sets the "name" attribute of the captcha text input (default: same as input_id)
     *     'input_text':
     *         A string that sets the text of the label for the captcha text input (default: Type the text:)
     *     'input_attributes':
     *         An array of additional HTML tag attributes to pass to the text input tag (default: empty)
     *     'image_attributes':
     *         An array of additional HTML tag attributes to pass to the captcha image tag (default: empty)
     *     'error_html':
     *         Optional HTML markup to be shown above the text input field
     *     'namespace':
     *         The optional captcha namespace to use for showing the image and playing back the audio. Namespaces are for using multiple captchas on the same page.
     *
     * @param array $options Array of options for modifying the HTML code.
     * @param int   $parts Securiage::HTML_* constant controlling what component of the captcha HTML to display
     *
     * @return string  The generated HTML code for displaying the captcha
     */
    public static function getCaptchaHtml($options = array(), $parts = Securimage::HTML_ALL)
    {
        static $javascript_init = false;

        if (!isset($options['securimage_path'])) {
            $docroot = (isset($_SERVER['DOCUMENT_ROOT'])) ? $_SERVER['DOCUMENT_ROOT'] : substr($_SERVER['SCRIPT_FILENAME'], 0, -strlen($_SERVER['SCRIPT_NAME']));
            $docroot = realpath($docroot);
            $sipath  = dirname(__FILE__);
            $securimage_path = str_replace($docroot, '', $sipath);
        } else {
            $securimage_path = $options['securimage_path'];
        }

        $show_image_url    = (isset($options['show_image_url'])) ? $options['show_image_url'] : null;
        $image_id          = (isset($options['image_id'])) ? $options['image_id'] : 'captcha_image';
        $image_alt         = (isset($options['image_alt_text'])) ? $options['image_alt_text'] : 'CAPTCHA Image';
        $show_audio_btn    = (isset($options['show_audio_button'])) ? (bool)$options['show_audio_button'] : true;
        $disable_flash_fbk = (isset($options['disable_flash_fallback'])) ? (bool)$options['disable_flash_fallback'] : false;
        $show_refresh_btn  = (isset($options['show_refresh_button'])) ? (bool)$options['show_refresh_button'] : true;
        $refresh_icon_url  = (isset($options['refresh_icon_url'])) ? $options['refresh_icon_url'] : null;
        $audio_but_bg_col  = (isset($options['audio_button_bgcol'])) ? $options['audio_button_bgcol'] : '#ffffff';
        $audio_icon_url    = (isset($options['audio_icon_url'])) ? $options['audio_icon_url'] : null;
        $loading_icon_url  = (isset($options['loading_icon_url'])) ? $options['loading_icon_url'] : null;
        $icon_size         = (isset($options['icon_size'])) ? $options['icon_size'] : 32;
        $audio_play_url    = (isset($options['audio_play_url'])) ? $options['audio_play_url'] : null;
        $audio_swf_url     = (isset($options['audio_swf_url'])) ? $options['audio_swf_url'] : null;
        $js_url            = (isset($options['js_url'])) ? $options['js_url'] : null;
        $show_input        = (isset($options['show_text_input'])) ? (bool)$options['show_text_input'] : true;
        $refresh_alt       = (isset($options['refresh_alt_text'])) ? $options['refresh_alt_text'] : 'Refresh Image';
        $refresh_title     = (isset($options['refresh_title_text'])) ? $options['refresh_title_text'] : 'Refresh Image';
        $input_text        = (isset($options['input_text'])) ? $options['input_text'] : 'Type the text:';
        $input_id          = (isset($options['input_id'])) ? $options['input_id'] : 'captcha_code';
        $input_name        = (isset($options['input_name'])) ? $options['input_name'] :  $input_id;
        $input_required    = (isset($options['input_required'])) ? (bool)$options['input_required'] : true;
        $input_attrs       = (isset($options['input_attributes'])) ? $options['input_attributes'] : array();
        $image_attrs       = (isset($options['image_attributes'])) ? $options['image_attributes'] : array();
        $error_html        = (isset($options['error_html'])) ? $options['error_html'] : null;
        $namespace         = (isset($options['namespace'])) ? $options['namespace'] : '';

        $rand              = md5(uniqid($_SERVER['REMOTE_PORT'], true));
        $securimage_path   = rtrim($securimage_path, '/\\');
        $securimage_path   = str_replace('\\', '/', $securimage_path);

        $image_attr = '';
        if (!is_array($image_attrs)) $image_attrs = array();
        if (!isset($image_attrs['style'])) $image_attrs['style'] = 'float: left; padding-right: 5px';
        $image_attrs['id']  = $image_id;

        $show_path = $securimage_path . '/securimage_show.php?';
        if ($show_image_url) {
            if (parse_url($show_image_url, PHP_URL_QUERY)) {
                $show_path = "{$show_image_url}&";
            } else {
                $show_path = "{$show_image_url}?";
            }
        }
        if (!empty($namespace)) {
            $show_path .= sprintf('namespace=%s&amp;', $namespace);
        }
        $image_attrs['src'] = $show_path . $rand;

        $image_attrs['alt'] = $image_alt;

        foreach($image_attrs as $name => $val) {
            $image_attr .= sprintf('%s="%s" ', $name, htmlspecialchars($val));
        }

        $swf_path  = $securimage_path . '/securimage_play.swf';
        $play_path = $securimage_path . '/securimage_play.php?';
        $icon_path = $securimage_path . '/images/audio_icon.png';
        $load_path = $securimage_path . '/images/loading.png';
        $js_path   = $securimage_path . '/securimage.js';

        if (!empty($audio_icon_url)) {
            $icon_path = $audio_icon_url;
        }

        if (!empty($loading_icon_url)) {
            $load_path = $loading_icon_url;
        }

        if (!empty($audio_play_url)) {
            if (parse_url($audio_play_url, PHP_URL_QUERY)) {
                $play_path = "{$audio_play_url}&";
            } else {
                $play_path = "{$audio_play_url}?";
            }
        }

        if (!empty($namespace)) {
            $play_path .= sprintf('namespace=%s&amp;', $namespace);
        }

        if (!empty($audio_swf_url)) {
            $swf_path = $audio_swf_url;
        }

        if (!empty($js_url)) {
            $js_path = $js_url;
        }

        $audio_obj = $image_id . '_audioObj';
        $html      = '';

        if ( ($parts & Securimage::HTML_IMG) > 0) {
            $html .= sprintf('<img %s/>', $image_attr);
        }

        if ( ($parts & Securimage::HTML_AUDIO) > 0 && $show_audio_btn) {
            // html5 audio
            $html .= sprintf('<div id="%s_audio_div">', $image_id) . "\n" .
                     sprintf('<audio id="%s_audio" preload="none" style="display: none">', $image_id) . "\n";

            // check for existence and executability of LAME binary
            // prefer mp3 over wav by sourcing it first, if available
            if (!empty(Securimage::$lame_binary_path) && is_executable(Securimage::$lame_binary_path)) {
                $html .= sprintf('<source id="%s_source_mp3" src="%sid=%s&amp;format=mp3" type="audio/mpeg">', $image_id, $play_path, uniqid()) . "\n";
            }

            // output wav source
            $html .= sprintf('<source id="%s_source_wav" src="%sid=%s" type="audio/wav">', $image_id, $play_path, uniqid()) . "\n";

            // flash audio button
            if (!$disable_flash_fbk) {
                $html .= sprintf('<object type="application/x-shockwave-flash" data="%s?bgcol=%s&amp;icon_file=%s&amp;audio_file=%s" height="%d" width="%d">',
                        htmlspecialchars($swf_path),
                        urlencode($audio_but_bg_col),
                        urlencode($icon_…

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