1 files changed, 101 insertions, 0 deletions
diff --git a/mod/captcha/start.php b/mod/captcha/start.php
new file mode 100644
index 000000000..f451ffcc6
--- /dev/null
+++ b/mod/captcha/start.php
@@ -0,0 +1,101 @@
+<?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;
+}