<?php
+
/**
* Experimental captcha plugin framework.
* Not intended as a real production captcha system; derived classes
* can extend the base to produce their fancy images in place of the
* text-based test output here.
*
- * Copyright (C) 2005, 2006 Brion Vibber <brion@pobox.com>
+ * Copyright (C) 2005-2007 Brion Vibber <brion@wikimedia.org>
* http://www.mediawiki.org/
*
* This program is free software; you can redistribute it and/or modify
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
* http://www.gnu.org/copyleft/gpl.html
*
- * @package MediaWiki
- * @subpackage Extensions
+ * @addtogroup Extensions
*/
if ( defined( 'MEDIAWIKI' ) ) {
global $wgExtensionFunctions, $wgGroupPermissions;
$wgExtensionFunctions[] = 'ceSetup';
+$wgExtensionCredits['other'][] = array(
+ 'name' => 'ConfirmEdit',
+ 'author' => 'Brion Vibber',
+ 'url' => 'http://www.mediawiki.org/wiki/Extension:ConfirmEdit',
+ 'description' => 'Simple captcha implementation',
+);
+
+# Internationalisation file
+require_once( 'ConfirmEdit.i18n.php' );
/**
* The 'skipcaptcha' permission key can be given out to
$wgCaptchaClass = 'SimpleCaptcha';
/**
- * Currently the captcha works only for page edits.
+ * Actions which can trigger a captcha
*
* If the 'edit' trigger is on, *every* edit will trigger the captcha.
* This may be useful for protecting against vandalbot attacks.
* edits that include URLs that aren't in the current version of the page.
* This should catch automated linkspammers without annoying people when
* they make more typical edits.
+ *
+ * The captcha code should not use $wgCaptchaTriggers, but CaptchaTriggers()
+ * which also takes into account per namespace triggering.
*/
$wgCaptchaTriggers = array();
$wgCaptchaTriggers['edit'] = false; // Would check on every edit
+$wgCaptchaTriggers['create'] = false; // Check on page creation.
$wgCaptchaTriggers['addurl'] = true; // Check on edits that add URLs
$wgCaptchaTriggers['createaccount'] = true; // Special:Userlogin&type=signup
+$wgCaptchaTriggers['badlogin'] = true; // Special:Userlogin after failure
+
+/**
+ * You may wish to apply special rules for captcha triggering on some namespaces.
+ * $wgCaptchaTriggersOnNamespace[<namespace id>][<trigger>] forces an always on /
+ * always off configuration with that trigger for the given namespace.
+ * Leave unset to use the global options ($wgCaptchaTriggers).
+ *
+ * Shall not be used with 'createaccount' (it is not checked).
+ */
+$wgCaptchaTriggersOnNamespace = array();
+
+#Example:
+#$wgCaptchaTriggersOnNamespace[NS_TALK]['create'] = false; //Allow creation of talk pages without captchas.
+#$wgCaptchaTriggersOnNamespace[NS_PROJECT]['edit'] = true; //Show captcha whenever editing Project pages.
+
+/**
+ * Indicate how to store per-session data required to match up the
+ * internal captcha data with the editor.
+ *
+ * 'CaptchaSessionStore' uses PHP's session storage, which is cookie-based
+ * and may fail for anons with cookies disabled.
+ *
+ * 'CaptchaCacheStore' uses $wgMemc, which avoids the cookie dependency
+ * but may be fragile depending on cache configuration.
+ */
+global $wgCaptchaStorageClass;
+$wgCaptchaStorageClass = 'CaptchaSessionStore';
+/**
+ * Number of seconds a captcha session should last in the data cache
+ * before expiring when managing through CaptchaCacheStore class.
+ *
+ * Default is a half hour.
+ */
+global $wgCaptchaSessionExpiration;
+$wgCaptchaSessionExpiration = 30 * 60;
+
+/**
+ * Number of seconds after a bad login that a captcha will be shown to
+ * that client on the login form to slow down password-guessing bots.
+ *
+ * Has no effect if 'badlogin' is disabled in $wgCaptchaTriggers or
+ * if there is not a caching engine enabled.
+ *
+ * Default is five minutes.
+ */
+global $wgCaptchaBadLoginExpiration;
+$wgCaptchaBadLoginExpiration = 5 * 60;
/**
* Allow users who have confirmed their e-mail addresses to post
* Regex to whitelist URLs to known-good sites...
* For instance:
* $wgCaptchaWhitelist = '#^https?://([a-z0-9-]+\\.)?(wikimedia|wikipedia)\.org/#i';
+ * Local admins can define a whitelist under [[MediaWiki:captcha-addurl-whitelist]]
*/
$wgCaptchaWhitelist = false;
+/**
+ * Additional regexes to check for. Use full regexes; can match things
+ * other than URLs such as junk edits.
+ *
+ * If the new version matches one and the old version doesn't,
+ * toss up the captcha screen.
+ *
+ * @fixme Add a message for local admins to add items as well.
+ */
+$wgCaptchaRegexes = array();
+
+/** Register special page */
+global $wgSpecialPages;
+$wgSpecialPages['Captcha'] = array( /*class*/ 'SpecialPage', /*name*/'Captcha', /*restriction*/ '',
+ /*listed*/ false, /*function*/ false, /*file*/ false );
+
/**
* Set up message strings for captcha utilities.
*/
function ceSetup() {
- global $wgMessageCache, $wgHooks, $wgCaptcha, $wgCaptchaClass;
- $wgMessageCache->addMessages( array(
- 'captcha-short' =>
- "Your edit includes new URL links; as a protection against automated " .
- "spam, you'll need to type in the words that appear in this image:\n" .
- "<br />([[Special:Captcha/help|What is this?]])",
- 'captchahelp-title' =>
- 'Captcha help',
- 'captchahelp-text' =>
- "Web sites that accept postings from the public, like this wiki, " .
- "are often abused by spammers who use automated tools to post their " .
- "links to many sites. While these spam links can be removed, they " .
- "are a significant nuisance." .
- "\n\n" .
- "Sometimes, especially when adding new web links to a page, " .
- "the wiki may show you an image of colored or distorted text and " .
- "ask you to type the words shown. Since this is a task that's hard " .
- "to automate, it will allow most real humans to make their posts " .
- "while stopping most spammers and other robotic attackers." .
- "\n\n" .
- "Unfortunately this may inconvenience users with limited vision or " .
- "using text-based or speech-based browsers. At the moment we do not " .
- "have an audio alternative available. Please contact the site " .
- "administrators for assistance if this is unexpectedly preventing " .
- "you from making legitimate posts." .
- "\n\n" .
- "Hit the 'back' button in your browser to return to the page editor.",
- 'captcha-createaccount' =>
- "As a protection against automated spam, you'll need to type in the " .
- "words that appear in this image to register an account:\n" .
- "<br />([[Special:Captcha/help|What is this?]])",
- 'captcha-createaccount-fail' =>
- "Incorrect or missing confirmation code." ) );
-
- SpecialPage::addPage( new SpecialPage( 'Captcha', false,
- /*listed*/ false, /*function*/ false, /*file*/ false ) );
-
+ # Add messages
+ global $wgMessageCache, $wgConfirmEditMessages;
+ foreach( $wgConfirmEditMessages as $lang => $messages )
+ $wgMessageCache->addMessages( $messages, $lang );
+
+ global $wgHooks, $wgCaptcha, $wgCaptchaClass, $wgSpecialPages;
$wgCaptcha = new $wgCaptchaClass();
$wgHooks['EditFilter'][] = array( &$wgCaptcha, 'confirmEdit' );
-
+
$wgHooks['UserCreateForm'][] = array( &$wgCaptcha, 'injectUserCreate' );
$wgHooks['AbortNewAccount'][] = array( &$wgCaptcha, 'confirmUserCreate' );
+
+ $wgHooks['LoginAuthenticateAudit'][] = array( &$wgCaptcha, 'triggerUserLogin' );
+ $wgHooks['UserLoginForm'][] = array( &$wgCaptcha, 'injectUserLogin' );
+ $wgHooks['AbortLogin'][] = array( &$wgCaptcha, 'confirmUserLogin' );
+
+ global $wgGroupPermissions, $wgCaptchaTriggers;
+ if( !$wgGroupPermissions['*']['read'] && $wgCaptchaTriggers['badlogin'] ) {
+ // We need to ensure that the captcha interface is accessible
+ // so that unauthenticated users can actually get in after a
+ // mistaken password typing.
+ global $wgWhitelistRead;
+ $image = Title::makeTitle( NS_SPECIAL, 'Captcha/image' );
+ $help = Title::makeTitle( NS_SPECIAL, 'Captcha/help' );
+ $wgWhitelistRead[] = $image->getPrefixedText();
+ $wgWhitelistRead[] = $help->getPrefixedText();
+ }
}
/**
}
class SimpleCaptcha {
+ function SimpleCaptcha() {
+ global $wgCaptchaStorageClass;
+ $this->storage = new $wgCaptchaStorageClass;
+ }
+
/**
* Insert a captcha prompt into the edit form.
* This sample implementation generates a simple arithmetic operation;
$a = mt_rand(0, 100);
$b = mt_rand(0, 10);
$op = mt_rand(0, 1) ? '+' : '-';
-
+
$test = "$a $op $b";
$answer = ($op == '+') ? ($a + $b) : ($a - $b);
-
+
$index = $this->storeCaptcha( array( 'answer' => $answer ) );
-
+
return "<p><label for=\"wpCaptchaWord\">$test</label> = " .
wfElement( 'input', array(
'name' => 'wpCaptchaWord',
'id' => 'wpCaptchaId',
'value' => $index ) );
}
-
+
/**
* Insert the captcha prompt into an edit form.
* @param OutputPage $out
*/
function editCallback( &$out ) {
- $out->addWikiText( wfMsg( "captcha-short" ) );
+ $out->addWikiText( $this->getMessage( $this->action ) );
$out->addHTML( $this->getForm() );
}
-
+
+ /**
+ * Show a message asking the user to enter a captcha on edit
+ * The result will be treated as wiki text
+ *
+ * @param $action Action being performed
+ * @return string
+ */
+ function getMessage( $action ) {
+ $name = 'captcha-' . $action;
+ $text = wfMsg( $name );
+ # Obtain a more tailored message, if possible, otherwise, fall back to
+ # the default for edits
+ return wfEmptyMsg( $name, $text ) ? wfMsg( 'captcha-edit' ) : $text;
+ }
+
/**
* Inject whazawhoo
* @fixme if multiple thingies insert a header, could break
if( $wgCaptchaTriggers['createaccount'] ) {
$template->set( 'header',
"<div class='captcha'>" .
- $wgOut->parse( wfMsg( 'captcha-createaccount' ) ) .
+ $wgOut->parse( $this->getMessage( 'createaccount' ) ) .
+ $this->getForm() .
+ "</div>\n" );
+ }
+ return true;
+ }
+
+ /**
+ * Inject a captcha into the user login form after a failed
+ * password attempt as a speedbump for mass attacks.
+ * @fixme if multiple thingies insert a header, could break
+ * @param SimpleTemplate $template
+ * @return bool true to keep running callbacks
+ */
+ function injectUserLogin( &$template ) {
+ if( $this->isBadLoginTriggered() ) {
+ global $wgOut;
+ $template->set( 'header',
+ "<div class='captcha'>" .
+ $wgOut->parse( $this->getMessage( 'badlogin' ) ) .
$this->getForm() .
"</div>\n" );
}
return true;
}
+ /**
+ * When a bad login attempt is made, increment an expiring counter
+ * in the memcache cloud. Later checks for this may trigger a
+ * captcha display to prevent too many hits from the same place.
+ * @param User $user
+ * @param string $password
+ * @param int $retval authentication return value
+ * @return bool true to keep running callbacks
+ */
+ function triggerUserLogin( $user, $password, $retval ) {
+ global $wgCaptchaTriggers, $wgCaptchaBadLoginExpiration, $wgMemc;
+ if( $retval == LoginForm::WRONG_PASS && $wgCaptchaTriggers['badlogin'] ) {
+ $key = $this->badLoginKey();
+ $count = $wgMemc->get( $key );
+ if( !$count ) {
+ $wgMemc->add( $key, 0, $wgCaptchaBadLoginExpiration );
+ }
+ $count = $wgMemc->incr( $key );
+ }
+ return true;
+ }
+
+ /**
+ * Check if a bad login has already been registered for this
+ * IP address. If so, require a captcha.
+ * @return bool
+ * @access private
+ */
+ function isBadLoginTriggered() {
+ global $wgMemc;
+ return intval( $wgMemc->get( $this->badLoginKey() ) ) > 0;
+ }
+
+ /**
+ * Internal cache key for badlogin checks.
+ * @return string
+ * @access private
+ */
+ function badLoginKey() {
+ return wfMemcKey( 'captcha', 'badlogin', 'ip', wfGetIP() );
+ }
+
/**
* Check if the submitted form matches the captcha session data provided
* by the plugin when the form was generated.
function keyMatch( $request, $info ) {
return $request->getVal( 'wpCaptchaWord' ) == $info['answer'];
}
-
+
// ----------------------------------
-
+
+ /**
+ * @param EditPage $editPage
+ * @param string $action (edit/create/addurl...)
+ * @return bool true if action triggers captcha on editPage's namespace
+ */
+ function captchaTriggers( &$editPage, $action) {
+ global $wgCaptchaTriggers, $wgCaptchaTriggersOnNamespace;
+ //Special config for this NS?
+ if (isset( $wgCaptchaTriggersOnNamespace[$editPage->mTitle->getNamespace()][$action] ) )
+ return $wgCaptchaTriggersOnNamespace[$editPage->mTitle->getNamespace()][$action];
+
+ return ( !empty( $wgCaptchaTriggers[$action] ) ); //Default
+ }
+
+
/**
* @param EditPage $editPage
* @param string $newtext
*/
function shouldCheck( &$editPage, $newtext, $section ) {
$this->trigger = '';
-
+
global $wgUser;
if( $wgUser->isAllowed( 'skipcaptcha' ) ) {
wfDebug( "ConfirmEdit: user group allows skipping captcha\n" );
return false;
}
-
+
global $wgEmailAuthentication, $ceAllowConfirmedEmail;
if( $wgEmailAuthentication && $ceAllowConfirmedEmail &&
$wgUser->isEmailConfirmed() ) {
wfDebug( "ConfirmEdit: user has confirmed mail, skipping captcha\n" );
return false;
}
-
- global $wgCaptchaTriggers;
- if( !empty( $wgCaptchaTriggers['edit'] ) ) {
+
+ if( $this->captchaTriggers( $editPage, 'edit' ) ) {
// Check on all edits
+ global $wgUser, $wgTitle;
+ $this->trigger = sprintf( "edit trigger by '%s' at [[%s]]",
+ $wgUser->getName(),
+ $wgTitle->getPrefixedText() );
+ $this->action = 'edit';
wfDebug( "ConfirmEdit: checking all edits...\n" );
return true;
}
-
- if( !empty( $wgCaptchaTriggers['addurl'] ) ) {
+
+ if( $this->captchaTriggers( $editPage, 'create' ) && !$editPage->mTitle->exists() ) {
+ //Check if creating a page
+ global $wgUser, $wgTitle;
+ $this->trigger = sprintf( "Create trigger by '%s' at [[%s]]",
+ $wgUser->getName(),
+ $wgTitle->getPrefixedText() );
+ $this->action = 'create';
+ wfDebug( "ConfirmEdit: checking on page creation...\n" );
+ return true;
+ }
+
+ if( $this->captchaTriggers( $editPage, 'addurl' ) ) {
// Only check edits that add URLs
$oldtext = $this->loadText( $editPage, $section );
-
+
$oldLinks = $this->findLinks( $oldtext );
$newLinks = $this->findLinks( $newtext );
$unknownLinks = array_filter( $newLinks, array( &$this, 'filterLink' ) );
-
+
$addedLinks = array_diff( $unknownLinks, $oldLinks );
$numLinks = count( $addedLinks );
-
+
if( $numLinks > 0 ) {
global $wgUser, $wgTitle;
$this->trigger = sprintf( "%dx url trigger by '%s' at [[%s]]: %s",
$wgUser->getName(),
$wgTitle->getPrefixedText(),
implode( ", ", $addedLinks ) );
+ $this->action = 'addurl';
return true;
}
}
-
+
+ global $wgCaptchaRegexes;
+ if( !empty( $wgCaptchaRegexes ) ) {
+ // Custom regex checks
+ $oldtext = $this->loadText( $editPage, $section );
+
+ foreach( $wgCaptchaRegexes as $regex ) {
+ $newMatches = array();
+ if( preg_match_all( $regex, $newtext, $newMatches ) ) {
+ $oldMatches = array();
+ preg_match_all( $regex, $oldtext, $oldMatches );
+
+ $addedMatches = array_diff( $newMatches[0], $oldMatches[0] );
+
+ $numHits = count( $addedMatches );
+ if( $numHits > 0 ) {
+ global $wgUser, $wgTitle;
+ $this->trigger = sprintf( "%dx %s at [[%s]]: %s",
+ $numHits,
+ $regex,
+ $wgUser->getName(),
+ $wgTitle->getPrefixedText(),
+ implode( ", ", $addedMatches ) );
+ $this->action = 'edit';
+ return true;
+ }
+ }
+ }
+ }
+
return false;
}
-
+
/**
* Filter callback function for URL whitelisting
+ * @param string url to check
* @return bool true if unknown, false if whitelisted
* @access private
*/
function filterLink( $url ) {
global $wgCaptchaWhitelist;
- return !( $wgCaptchaWhitelist && preg_match( $wgCaptchaWhitelist, $url ) );
+ $source = wfMsgForContent( 'captcha-addurl-whitelist' );
+
+ $whitelist = wfEmptyMsg( 'captcha-addurl-whitelist', $source )
+ ? false
+ : $this->buildRegexes( explode( "\n", $source ) );
+
+ $cwl = $wgCaptchaWhitelist !== false ? preg_match( $wgCaptchaWhitelist, $url ) : false;
+ $wl = $whitelist !== false ? preg_match( $whitelist, $url ) : false;
+
+ return !( $cwl || $wl );
}
-
+
+ /**
+ * Build regex from whitelist
+ * @param string lines from [[MediaWiki:Captcha-addurl-whitelist]]
+ * @return string Regex or bool false if whitelist is empty
+ * @access private
+ */
+ function buildRegexes( $lines ) {
+ # Code duplicated from the SpamBlacklist extension (r19197)
+
+ # Strip comments and whitespace, then remove blanks
+ $lines = array_filter( array_map( 'trim', preg_replace( '/#.*$/', '', $lines ) ) );
+
+ # No lines, don't make a regex which will match everything
+ if ( count( $lines ) == 0 ) {
+ wfDebug( "No lines\n" );
+ return false;
+ } else {
+ # Make regex
+ # It's faster using the S modifier even though it will usually only be run once
+ //$regex = 'http://+[a-z0-9_\-.]*(' . implode( '|', $lines ) . ')';
+ //return '/' . str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $regex) ) . '/Si';
+ $regexes = '';
+ $regexStart = '/http:\/\/+[a-z0-9_\-.]*(';
+ $regexEnd = ')/Si';
+ $regexMax = 4096;
+ $build = false;
+ foreach( $lines as $line ) {
+ // FIXME: not very robust size check, but should work. :)
+ if( $build === false ) {
+ $build = $line;
+ } elseif( strlen( $build ) + strlen( $line ) > $regexMax ) {
+ $regexes .= $regexStart .
+ str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $build) ) .
+ $regexEnd;
+ $build = $line;
+ } else {
+ $build .= '|' . $line;
+ }
+ }
+ if( $build !== false ) {
+ $regexes .= $regexStart .
+ str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $build) ) .
+ $regexEnd;
+ }
+ return $regexes;
+ }
+ }
+
/**
* The main callback run on edit attempts.
* @param EditPage $editPage
return false;
}
} else {
- wfDebug( "ConfirmEdit: no new links.\n" );
+ wfDebug( "ConfirmEdit: no need to show captcha.\n" );
return true;
}
}
-
+
/**
* Hook for user creation form submissions.
* @param User $u
return true;
}
+ /**
+ * Hook for user login form submissions.
+ * @param User $u
+ * @param string $message
+ * @return bool true to continue, false to abort user creation
+ */
+ function confirmUserLogin( $u, $pass, &$retval ) {
+ if( $this->isBadLoginTriggered() ) {
+ $this->trigger = "post-badlogin login '" . $u->getName() . "'";
+ if( !$this->passCaptcha() ) {
+ $message = wfMsg( 'captcha-badlogin-fail' );
+ // Emulate a bad-password return to confuse the shit out of attackers
+ $retval = LoginForm::WRONG_PASS;
+ return false;
+ }
+ }
+ return true;
+ }
+
/**
* Given a required captcha run, test form input for correct
* input on the open session.
return false;
}
}
-
+
/**
* Log the status and any triggering info for debugging or statistics
* @param string $message
function log( $message ) {
wfDebugLog( 'captcha', 'ConfirmEdit: ' . $message . '; ' . $this->trigger );
}
-
+
/**
* Generate a captcha session ID and save the info in PHP's session storage.
* (Requires the user to have cookies enabled to get through the captcha.)
// Assign random index if we're not udpating
$info['index'] = strval( mt_rand() );
}
- $_SESSION['captcha' . $info['index']] = $info;
+ $this->storage->store( $info['index'], $info );
return $info['index'];
}
-
+
/**
* Fetch this session's captcha info.
* @return mixed array of info, or false if missing
function retrieveCaptcha() {
global $wgRequest;
$index = $wgRequest->getVal( 'wpCaptchaId' );
- if( isset( $_SESSION['captcha' . $index] ) ) {
- return $_SESSION['captcha' . $index];
- } else {
- return false;
- }
+ return $this->storage->retrieve( $index );
}
-
+
/**
* Clear out existing captcha info from the session, to ensure
* it can't be reused.
*/
function clearCaptcha( $info ) {
- unset( $_SESSION['captcha' . $info['index']] );
+ $this->storage->clear( $info['index'] );
}
-
+
/**
* Retrieve the current version of the page or section being edited...
* @param EditPage $editPage
}
}
}
-
+
/**
* Extract a list of all recognized HTTP links in the text.
* @param string $text
* @return array of strings
*/
function findLinks( $text ) {
- $regex = '/((?:' . HTTP_PROTOCOLS . ')' . EXT_LINK_URL_CLASS . '+)/';
-
- if( preg_match_all( $regex, $text, $matches, PREG_PATTERN_ORDER ) ) {
- return $matches[1];
- } else {
- return array();
- }
+ global $wgParser, $wgTitle, $wgUser;
+
+ $options = new ParserOptions();
+ $text = $wgParser->preSaveTransform( $text, $wgTitle, $wgUser, $options );
+ $out = $wgParser->parse( $text, $wgTitle, $options );
+
+ return array_keys( $out->getExternalLinks() );
}
-
+
/**
* Show a page explaining what this wacky thing is.
*/
global $wgOut, $ceAllowConfirmedEmail;
$wgOut->setPageTitle( wfMsg( 'captchahelp-title' ) );
$wgOut->addWikiText( wfMsg( 'captchahelp-text' ) );
+ if ( $this->storage->cookiesNeeded() ) {
+ $wgOut->addWikiText( wfMsg( 'captchahelp-cookies-needed' ) );
+ }
+ }
+
+}
+
+class CaptchaSessionStore {
+ function store( $index, $info ) {
+ $_SESSION['captcha' . $info['index']] = $info;
+ }
+
+ function retrieve( $index ) {
+ if( isset( $_SESSION['captcha' . $index] ) ) {
+ return $_SESSION['captcha' . $index];
+ } else {
+ return false;
+ }
}
+ function clear( $index ) {
+ unset( $_SESSION['captcha' . $index] );
+ }
+
+ function cookiesNeeded() {
+ return true;
+ }
+}
+
+class CaptchaCacheStore {
+ function store( $index, $info ) {
+ global $wgMemc, $wgCaptchaSessionExpiration;
+ $wgMemc->set( wfMemcKey( 'captcha', $index ), $info,
+ $wgCaptchaSessionExpiration );
+ }
+
+ function retrieve( $index ) {
+ global $wgMemc;
+ $info = $wgMemc->get( wfMemcKey( 'captcha', $index ) );
+ if( $info ) {
+ return $info;
+ } else {
+ return false;
+ }
+ }
+
+ function clear( $index ) {
+ global $wgMemc;
+ $wgMemc->delete( wfMemcKey( 'captcha', $index ) );
+ }
+
+ function cookiesNeeded() {
+ return false;
+ }
}
} # End invocation guard
-?>
+
ToastFreeware / toast / cookiecaptcha.git / blobdiff