[WeChall] The Guestbook

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The Guestbook (Exploit, PHP, MySQL)

The Guestbook

This time you have to exploit a small guestbook to retrieve the admin password.
Again you are given the guestbook sourcecode, also as highlighted version.
Currently there is no way to register or login to the guestbook tables, but an admin account already exists.
The solution is the Admin password, case sensitive.

Note: Every session gets it own guestbook to play with. However you should clear your guestbook when you are done, as your entries can be read by skilled players.

GeSHi`ed php code for gbook.php.inc

<?php
/**
 * Get the database instance
 * @return GDO_Database
 */function gbook_db()
{
        static $gbdb = true;
        if ($gbdb === true)
        {                $gbdb = gdo_db_instance('localhost', CHALL_GBOOK_USER, CHALL_GBOOK_PASS, CHALL_GBOOK_DB);
                $gbdb->setLogging(false); // Disable annoying logs. 
                $gbdb->setEMailOnError(false); // Disable annoying emails.
        }
        return $gbdb;}
 
/**
 * Create the 2 tables for the challenge.
 */function gbook_createTables()
{
        $db = gbook_db();
        
        // user table can not get populated, but an admin account exists        $query =
                "CREATE TABLE IF NOT EXISTS gbook_user ( ".
                "gbu_id        INT(11)     UNSIGNED PRIMARY KEY, ". # Guestbook userid
                "gbu_name      VARCHAR(63) CHARACTER SET ASCII COLLATE ascii_general_ci, ". # Guestbook username
                "gbu_password  VARCHAR(255) CHARACTER SET ASCII COLLATE ascii_bin ) "; # Guestbook password <-- You need the password for username Admin        $db->queryWrite($query);
        
        // the guestbook messages table
        $query =
                "CREATE TABLE IF NOT EXISTS gbook_book ( ".                "gbb_sessid   CHAR(16)     CHARACTER SET ASCII COLLATE ascii_bin, ". # Every wechall user gets his own guestbook, so you maybe can`t spoil it that easily.
                "gbb_uid      INT(11)      UNSIGNED, ". # GB userid (currently unused)
                "gbb_time     INT(11)      UNSIGNED, ". # Timestamp
                "gbb_ip       VARCHAR(32)  CHARACTER SET ASCII COLLATE ascii_bin, ".       # IP
                "gbb_msg      TEXT         CHARACTER SET utf8  COLLATE utf8_general_ci, ". # Message                "INDEX(gbb_sessid) )";
        $db->queryWrite($query);
}
 
/** * Cleanup very old messages.
 */
function gbook_cleanup()
{
        $db = gbook_db();        $cut = time() - GWF_TIME::ONE_DAY * 2;
        $query = "DELETE FROM gbook_book WHERE gbb_time<$cut";
        return $db->queryWrite($query);
}
 /**
 * Generate a unique ID, so guests can also play this challenge. Every player gets his own guestbook.
 * This part is unimportant for the challenge!
 */
function gbook_playerID($reset=false){
        return GWF_Session::getSessID(); # new session == new game
}
 
/** * Get IP
 */
function gbook_getIP()
{
        if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {                return $_SERVER['HTTP_X_FORWARDED_FOR'];
        }
        elseif (isset($_SERVER['HTTP_VIA'])) { 
                return $_SERVER['HTTP_VIA'];
        }        else {
                return $_SERVER['REMOTE_ADDR'];
        }
}
  
/**
 * Insert a message for current player.
 * @param int $userid
 * @param string $message */
function gbook_insertMessage($userid, $message)
{
        $db = gbook_db();
                $message = trim($message);
        $len = strlen($message);
        
        if ($len <= 3) {
                echo GWF_HTML::error('The Guestbook', 'Your message is too short.');                return false;
        }
        
        if ($len > 256) {
                echo GWF_HTML::error('The Guestbook', 'Your message is too long.');                return false;
        }
 
        # insert the entry      
        $playerid = gbook_playerID(true); // Current Player        $userid = 0; # guestbook has no login yet.
        $time = time();
        $ip = gbook_getIP();
        $message = GDO::escape($message); 
        $query = "INSERT INTO gbook_book VALUES('$playerid', $userid, $time, '$ip', '$message')";        if (false === $db->queryWrite($query)) {
                echo GWF_HTML::err('ERR_DATABASE', array(__FILE__, __LINE__));
                return false;
        }
                echo GWF_HTML::message('The Guestbook', 'Your entry has been added.');
        return true;
}
 
/** * Manually clear the guestbook for current player.
 */
function gbook_clear()
{
        $db = gbook_db();        $playerid = gbook_playerID();
        $query = "DELETE FROM gbook_book WHERE gbb_sessid='$playerid'";
        return $db->queryWrite($query);
}
 /**
 * Get Form to sign guestbook.
 */
function gbook_form()
{        return sprintf('<form action="index.php" method="post"><textarea name="message" rows="12" cols="40"></textarea><input type="submit" name="sign" value="Sign Guestbook" /><input type="submit" name="clear" value="Clear Guestbook" /></form>');
}
 
/**
 * Display guestbook of current player. */
function gbook_display()
{
        $db = gbook_db();
                $playerid = gbook_playerID();
        
        $query = "SELECT * FROM gbook_book WHERE gbb_sessid='$playerid'";
        if (false === ($result = $db->queryAll($query))) {
                return GWF_HTML::err('ERR_DATABASE', array(__FILE__, __LINE__));        }
        
        echo '<h3>Your Guestbook</h3>'.PHP_EOL;
        
        echo GWF_Table::start();        foreach ($result as $row)
        {
                $rs = GWF_Table::rowStart();
                $re = GWF_Table::rowEnd();
                $username = GWF_HTML::lang('guest');                echo $rs;
                echo sprintf('<td>%s - %s - %s</td>', GWF_Time::displayTimestamp($row['gbb_time']), $username, $row['gbb_ip']).PHP_EOL;
                echo $re;
                echo $rs;
                echo sprintf('<td>%s</td>', GWF_HTML::display($row['gbb_msg'])).PHP_EOL;                echo $re;
        }
        echo GWF_Table::end();
}
?>