A+

漏洞影响范围：

phpMyAdmin 4.8.0和4.8.1

漏洞分析：

index.php 55-63行

if (! empty($_REQUEST['target'])
    && is_string($_REQUEST['target'])
    && ! preg_match('/^index/', $_REQUEST['target'])
    && ! in_array($_REQUEST['target'], $target_blacklist)
    && Core::checkPageValidity($_REQUEST['target']) 
) {
    include $_REQUEST['target'];
    exit;
}

这里需要满足如下5个条件便可以执行包含文件代码include $_REQUEST['target'];

1.$_REQUEST['target']不为空
2.$_REQUEST['target']是字符串
3.$_REQUEST['target']开头不是index
4.$_REQUEST['target']不在$target_blacklist中
5.Core::checkPageValidity($_REQUEST['target'])为真

定位到checkPageValidity函数在Core.php 443-476行

public static function checkPageValidity(&$page, array $whitelist = [])
    {
        if (empty($whitelist)) {
            $whitelist = self::$goto_whitelist;
        }
        if (! isset($page) || !is_string($page)) {
            return false;
        }

        if (in_array($page, $whitelist)) {
            return true;
        }

        $_page = mb_substr(
            $page,
            0,
            mb_strpos($page . '?', '?')
        );
        if (in_array($_page, $whitelist)) {
            return true;
        }

        $_page = urldecode($page);
        $_page = mb_substr(
            $_page,
            0,
            mb_strpos($_page . '?', '?')
        );
        if (in_array($_page, $whitelist)) {
            return true;
        }

        return false;
    }

一开始没有$whitelist，所以$whitelist被赋值为self::$goto_whitelist，追踪一下$goto_whitelist

public static $goto_whitelist = array(
        'db_datadict.php',
        'db_sql.php',
        'db_events.php',
        'db_export.php',
        'db_importdocsql.php',
        'db_multi_table_query.php',
        'db_structure.php',
        'db_import.php',
        'db_operations.php',
        'db_search.php',
        'db_routines.php',
        'export.php',
        'import.php',
        'index.php',
        'pdf_pages.php',
        'pdf_schema.php',
        'server_binlog.php',
        'server_collations.php',
        'server_databases.php',
        'server_engines.php',
        'server_export.php',
        'server_import.php',
        'server_privileges.php',
        'server_sql.php',
        'server_status.php',
        'server_status_advisor.php',
        'server_status_monitor.php',
        'server_status_queries.php',
        'server_status_variables.php',
        'server_variables.php',
        'sql.php',
        'tbl_addfield.php',
        'tbl_change.php',
        'tbl_create.php',
        'tbl_import.php',
        'tbl_indexes.php',
        'tbl_sql.php',
        'tbl_export.php',
        'tbl_operations.php',
        'tbl_structure.php',
        'tbl_relation.php',
        'tbl_replace.php',
        'tbl_row_action.php',
        'tbl_select.php',
        'tbl_zoom_select.php',
        'transformation_overview.php',
        'transformation_wrapper.php',
        'user_password.php',
    );

再次回到checkPageValidity函数里面知道传入的参数$page必须在上面的白名单里面才会返回true，考虑到可能会带有参数，所以有了下面的判断

$_page = mb_substr(
            $page,
            0,
            mb_strpos($page . '?', '?')
        );
        if (in_array($_page, $whitelist)) {
            return true;
        }

        $_page = urldecode($page);
        $_page = mb_substr(
            $_page,
            0,
            mb_strpos($_page . '?', '?')
        );
        if (in_array($_page, $whitelist)) {
            return true;
        }

        return false;

mb_strpos：是一个定位函数，获取指定的字符在一个字符串中首次出现的位置

mb_substr：截取指定字符串中某一段

$_page传入的是?之前的内容，如果$_page在白名单中则返回true
例如传入?target=db_datadict.php%253f，%253f开始服务器自动解码一次为%3f，然后urldecode函数再解码一次为?，则满足截取?之前的内容在白名单中，返回true。而在index.php中只解码一次为db_datadict.php%3f，然后进行包含