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<?php
/**
* Elgg captcha plugin
*
* @package ElggCaptcha
*/
register_elgg_event_handler('init','system','captcha_init');
function captcha_init() {
// Register page handler for captcha functionality
elgg_register_page_handler('captcha', 'captcha_page_handler');
// Extend CSS
elgg_extend_view('css', 'captcha/css');
// Number of background images
elgg_set_config('captcha_num_bg', 5);
// Default length
elgg_set_config('captcha_length', 5);
elgg_register_plugin_hook_handler('register', 'user', 'captcha_verify_action_hook');
elgg_register_plugin_hook_handler('action', 'user/requestnewpassword', 'captcha_verify_action_hook');
}
function captcha_page_handler($page) {
if (isset($page[0])) {
set_input('captcha_token', $page[0]);
}
include(elgg_get_plugins_path() . "captcha/captcha.php");
}
/**
* Generate a token to act as a seed value for the captcha algorithm.
*/
function captcha_generate_token() {
return md5(generate_action_token(time()).rand()); // Use action token plus some random for uniqueness
}
/**
* Generate a captcha based on the given seed value and length.
*
* @param string $seed_token
* @return string
*/
function captcha_generate_captcha($seed_token) {
/*
* We generate a token out of the random seed value + some session data,
* this means that solving via pr0n site or indian cube farm becomes
* significantly more tricky (we hope).
*
* We also add the site secret, which is unavailable to the client and so should
* make it very very hard to guess values before hand.
*
*/
return strtolower(substr(md5(generate_action_token(0) . $seed_token), 0, elgg_get_config('captcha_length')));
}
/**
* Verify a captcha based on the input value entered by the user and the seed token passed.
*
* @param string $input_value
* @param string $seed_token
* @return bool
*/
function captcha_verify_captcha($input_value, $seed_token) {
if (strcasecmp($input_value, captcha_generate_captcha($seed_token)) == 0) {
return true;
}
return false;
}
/**
* Listen to the action plugin hook and check the captcha.
*
* @param unknown_type $hook
* @param unknown_type $entity_type
* @param unknown_type $returnvalue
* @param unknown_type $params
*/
function captcha_verify_action_hook($hook, $entity_type, $returnvalue, $params) {
$token = get_input('captcha_token');
$input = get_input('captcha_input');
if (($token) && (captcha_verify_captcha($input, $token))) {
return true;
}
register_error(elgg_echo('captcha:captchafail'));
// forward to referrer or else action code sends to front page
forward(REFERER);
return false;
}
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