/wp-content/mu-plugins/math-comment-spam-protection.php

<?php

/*

Plugin Name: Math Comment Spam Protection

Plugin URI: http://sw-guide.de/wordpress/comment-spam-protection-plugin/

Description: Asks the visitor making the comment to answer a simple math question. This is intended to prove that the visitor is a human being and not a spam robot. Example of such question: <em>What is the sum of 2 and 9</em>?

Version: 2.0

Author: Michael Woehrer

Author URI: http://sw-guide.de/

*/



/*	----------------------------------------------------------------------------

 	    ____________________________________________________

       |                                                    |

       |           Math Comment Spam Protection             |

       |                © Michael Woehrer                   |

       |____________________________________________________|



	© Copyright 2006  Michael Woehrer  (michael dot woehrer at gmail dot com)



    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.



	----------------------------------------------------------------------------



	ACKNOWLEDGEMENTS:

	- Thanks to Steven Herod (http://www.herod.net/) for his plugin

	  "Did You Pass Math?". I took his idea and extended/improved it by

	  writing a plugin on my own. 



	----------------------------------------------------------------------------



	INSTALLATION, USAGE:

	Visit the plugin's homepage.



	----------------------------------------------------------------------------

	

*/







/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	Get settings

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

$mcsp_opt = get_option('plugin_mathcommentspamprotection');





/*******************************************************************************

 * Generate math question

 ******************************************************************************/

function math_comment_spam_protection() {



	global $mcsp_opt;

	

	// Get numbers in array

	$num_array = mcsp_aux_numbers_to_array($mcsp_opt['mcsp_opt_numbers']);



	// Get random keys

	$rand_keys = array_rand($num_array, 2);



	// Operands for displaying...

	$mcsp_info['operand1'] = $num_array[$rand_keys[0]];

	$mcsp_info['operand2'] = $num_array[$rand_keys[1]];





	// Calculate result

	$result = $rand_keys[0] + $rand_keys[1];

	$mcsp_info['result'] = mcsp_aux_generate_hash($result, date(j));

	

	return $mcsp_info;



}





/*******************************************************************************

 * Input validation. We use the special function to generate an encryption value

 * since we want to avoid the usage of cookies.  

 ******************************************************************************/

function mcsp_check_input($comment_data) {



	global $user_ID, $mcsp_opt;





    if ( !isset($user_ID) ) {	// Do not check if the user is registered.

		

		if ( $comment_data['comment_type'] == '' ) { // Do not check trackbacks/pingbacks



			// Get result

			$value_result = $_POST[ $mcsp_opt['mcsp_opt_fieldname_mathresult'] ];



			// Get value user has entered

			$value_entered = $_POST[ $mcsp_opt['mcsp_opt_fieldname_useranswer'] ];

			$value_entered = preg_replace('/[^0-9]/','',$value_entered);	// Remove everything except numbers



			if ($value_entered == '') {



				// Case 1: User has not entered an answer at all:



				die( __(stripslashes($mcsp_opt['mcsp_opt_msg_no_answer'])) );







			} elseif ( $value_result != mcsp_aux_generate_hash($value_entered, date(j)) ) {



				if ( ( date('G') <= 1 ) AND ( $value_result == mcsp_aux_generate_hash($value_entered, (intval(date(j))-1) ) )  ) {



					// User has just passed midnight while writing the comment. We consider

					// the time between 0:00 and 1:59 still as the day before to avoid

					// error messages if user visited page on 23:50 but pressed the "Submit Comment"

					// button on 0:15.



				} else {



					// Case 2: User has entered a wrong answer:



					die( __(stripslashes($mcsp_opt['mcsp_opt_msg_wrong_answer'])) );

				

				}

				

			}

			

		}



	}



	return $comment_data;



}



/*******************************************************************************

 * Generate hash

 ******************************************************************************/

function mcsp_aux_generate_hash($inputstring, $day) {





	// Add IP address:

	//  	[ not use for now... if users using dial-up connections, disconnect when writing

	//	  	  the comment and re-connect again, they will get a new IP address. ]

	// $inputstring .= getenv('REMOTE_ADDR');





	// Add name of the weblog:

	$inputstring .= get_bloginfo('name');

	// Add date:

	$inputstring .= $day . date('ny');





	// Get MD5 and reverse it

	$enc = strrev(md5($inputstring));

	// Get only a few chars out of the string

	$enc = substr($enc, 26, 1) . substr($enc, 10, 1) . substr($enc, 23, 1) . substr($enc, 3, 1) . substr($enc, 19, 1);

		

	// Return result

	return $enc; 



}





/*******************************************************************************

 * Apply plugin

 ******************************************************************************/

add_filter('preprocess_comment', 'mcsp_check_input', 0);







##################################################################################################################################



/*******************************************************************************

 * Admin

*******************************************************************************/



// Add admin menu

function mcsp_add_options_to_admin() {

    if (function_exists('add_options_page')) {

		add_options_page('Math Comment Spam', 'Math Comment Spam', 8, basename(__FILE__), 'mcsp_options_subpanel');

    }

}



// This will add the new item, 'Math Comment Spam', to the Options menu.

function mcsp_options_subpanel() {



	/* Lets add some default options if they don't exist

			If an option with the specified name already exists, no changes are made to its value

			or to the database as a whole. add_option() can only add options, not alter them.*/



	$tmp_noanswer =	'<p align="center">

<strong>Error:</strong> Please press the back button and fill the required field for spam protection.

</p>';

	$tmp_wronganswer = '<p align="center">

<strong>Error:</strong> You have entered the wrong sum in the spam protection field.

<br />Press the back button and try again.

</p>';

	$optionarray_def = array(

		'mcsp_opt_numbers'				=> '1~1, 2~2, 3~3, 4~4, 5~5, 6~6, 7~7, 8~8, 9~9, 10~10',

		'mcsp_opt_msg_no_answer' 		=> $tmp_noanswer,

		'mcsp_opt_msg_wrong_answer' 	=> $tmp_wronganswer,

		'mcsp_opt_fieldname_useranswer' => 'mcspvalue',

		'mcsp_opt_fieldname_mathresult' => 'mcspinfo',

		);

	add_option('plugin_mathcommentspamprotection', $optionarray_def, 'Math Comment Spam Protection Plugin Options');



	/* Check form submission and update options if no error occurred */

	if (isset($_POST['submit']) ) {

		$optionarray_update = array (

			'mcsp_opt_numbers' 				=> mcsp_aux_numbers_input_formatting($_POST['mcsp_opt_numbers']),

			'mcsp_opt_msg_no_answer'		=> $_POST['mcsp_opt_msg_no_answer'],

			'mcsp_opt_msg_wrong_answer' 	=> $_POST['mcsp_opt_msg_wrong_answer'],

			'mcsp_opt_fieldname_useranswer' => mcsp_aux_fieldname_formatting($_POST['mcsp_opt_fieldname_useranswer']),

			'mcsp_opt_fieldname_mathresult' => mcsp_aux_fieldname_formatting($_POST['mcsp_opt_fieldname_mathresult'])

		);

		update_option('plugin_mathcommentspamprotection', $optionarray_update);



	}



	/* Get options */

	$optionarray_def = get_option('plugin_mathcommentspamprotection');



	

?>



<!-- ############################## BEGIN: ADMIN OPTIONS ################### -->

<div class="wrap">



	<h2>Math Comment Spam Protection Options</h2>

	<p>For details, visit the <a title="Math Comment Spam Protection Plugin" href="http://sw-guide.de/wordpress/math-comment-spam-protection-plugin/">plugin's homepage</a>.



	<form name="form1" method="post" action="<?php echo $_SERVER['PHP_SELF'] . '?page=' . basename(__FILE__); ?>&updated=true">





	<!-- ****************** Operands ****************** -->

	<fieldset class="options">

		<legend>Used Operands</legend>

		<p style="margin-left: 25px; color: #555; font-size: .85em;">

			Enter the numbers to be used. Use the number on the left side, tilde (~) as separator and then the term to display.

			Separate values with comma (,).

			<br />Examples: 

			<br />&nbsp;-&nbsp;<em>1~one, 2~two, 3~three, 4~four, 5~five, 6~six, 7~seven, 8~eight, 9~nine, 10~ten</em>

			<br />&nbsp;-&nbsp;<em>1~1, 2~2, 3~3, 4~4, 5~5, 6~6, 7~7, 8~8, 9~9, 10~10</em>

		</p>

		<textarea style="margin-left: 25px" name="mcsp_opt_numbers" id="mcsp_opt_numbers" cols="100%" rows="2"><?php 

			echo htmlspecialchars(stripslashes(mcsp_aux_numbers_input_formatting($optionarray_def['mcsp_opt_numbers'])));

		?></textarea>

	</fieldset>



	<!-- ****************** Field Names ****************** -->

	<fieldset class="options">

		<legend>Field Names</legend>

		<p style="margin-left: 25px; color: #555; font-size: .85em;">

			<label for="mcsp_opt_fieldname_useranswer">Name of field for user's answer:</label>

			<br /><input name="mcsp_opt_fieldname_useranswer" type="text" id="mcsp_opt_fieldname_useranswer" value="<?php echo $optionarray_def['mcsp_opt_fieldname_useranswer']; ?>" size="30" />

			<br />

			<label for="mcsp_opt_fieldname_mathresult">Name of hidden field that contains the hash:</label>

			<br /><input name="mcsp_opt_fieldname_mathresult" type="text" id="mcsp_opt_fieldname_mathresult" value="<?php echo $optionarray_def['mcsp_opt_fieldname_mathresult']; ?>" size="30" />

		</p>

	</fieldset>









	<!-- ****************** Error Messages ****************** -->

	<fieldset class="options">

		<legend>Error Messages</legend>



		<!-- No Answer -->

		<p style="margin-left: 25px; color: #555; font-size: .85em;">

			Error message being displayed in case of no answer (empty field) / not entered a number:

		</p>

		<textarea style="margin-left: 25px" name="mcsp_opt_msg_no_answer" id="mcsp_opt_msg_no_answer" cols="100%" rows="3"><?php 

			echo htmlspecialchars(stripslashes($optionarray_def['mcsp_opt_msg_no_answer']));

		?></textarea>



		<!-- Wrong Answer -->

		<p style="margin-left: 25px; color: #555; font-size: .85em;">

			Error message being displayed in case of a wrong answer:

		</p>

		<textarea style="margin-left: 25px" name="mcsp_opt_msg_wrong_answer" id="mcsp_opt_msg_wrong_answer" cols="100%" rows="3"><?php 

			echo htmlspecialchars(stripslashes($optionarray_def['mcsp_opt_msg_wrong_answer']));

		?></textarea>



	</fieldset>









	<div class="submit">

		<input type="submit" name="submit" value="<?php _e('Update Options') ?> &raquo;" />

	</div>



	</form>



	<p style="text-align: center; font-size: .85em;">&copy; Copyright 2006&nbsp;&nbsp;<a href="http://sw-guide.de">Michael W&ouml;hrer</a></p>



</div> <!-- [wrap] -->

<!-- ############################## END: ADMIN OPTIONS ##################### -->





<?php





} // function mcsp_options_subpanel





function mcsp_aux_numbers_input_formatting($input) {

	// Formats the input of the numbers...

	$result = str_replace(' ', '', $input);	// Strip whitespace

	$result = preg_replace('/,/', ', ', $result); // Add whitespace after comma

	$result = preg_replace('/(\r\n|\n|\r)/', '', $result); // Strip line breaks

	return $result;

}



function mcsp_aux_numbers_to_array($input) {

	// Converts the input string, e.g. "1~one, 2~two, 3~three, 4~four, ..." 

	// into an array, e.g.: Array([1] => one, [2] => two, [3] => three, ...)



	$input = str_replace(' ', '', $input);	// Strip whitespace

	$sourcearray = explode(',', $input);	// Create array



	foreach ($sourcearray as $loopval) {

		$temparr = explode('~', $loopval);

		$targetarray[$temparr[0]] = $temparr[1];

	}

	return $targetarray;

}



function mcsp_aux_fieldname_formatting($input) {



	// Clean the input values for the field names...

	$return = preg_replace('/[^a-zA-Z0-9_\-]/', '', $input);

	

	return $return;



}





/* =============================================================================

   Apply the admin menu

============================================================================= */



add_action('admin_menu', 'mcsp_add_options_to_admin');



?>