0x01 背景
现在的WEB程序基本都有对SQL注入的全局过滤,像PHP开启了GPC或者在全局文件common.php上使用addslashes()函数对接收的参数进行过滤,尤其是单引号。二次注入也是一种比较常见的注入,它涉及到入库和出库。因为有全局转义所以入库的时候:
Insert into table (username) values (‘hack\’’);
这样入库后转义符就会消失变成了hack’,这样如果hack’出库被带入查询的话就会成功的引入了单引号导致注入。
漏洞来源于乌云:
http://www.wooyun.org/bugs/wooyun-2014-068362
0x02 环境搭建
看背景我们使用了低版本的74cms程序,版本为3.4(20140310)
①源码网上可以搜到,我打包了一份: http://pan.baidu.com/s/1c1mLCru
②解压到www的74cms(20140310)目录下,浏览器访问http://localhost/74cms(20140310)),然后按照提示一步步安装即可,安装遇到问题请自行百度或谷歌,成功后访问如下图:
0x03 漏洞分析
Part1:源码结构
源码的结构比较清晰,应该是审计过最清晰的结构了,主要有下面三块内容:
index.php引入了common.inc.php文件,我们跟进common.inc.php,发现了处理gpc的函数:
if (!empty($_GET)){$_GET = addslashes_deep($_GET);}if (!empty($_POST)){$_POST = addslashes_deep($_POST);}$_COOKIE = addslashes_deep($_COOKIE);$_REQUEST = addslashes_deep($_REQUEST);
可以看到,服务端处理GET和POST请求的变量时都会做addslashes处理。
Part2:审计过程
1.首先在个人发布简历处:
elseif ($act=='make4_save'){$resume_education=get_resume_education($_SESSION['uid'],$_REQUEST['pid']);if (count($resume_education)>=6) showmsg('教育经历不能超过6条!',1,$link);$setsqlarr['uid']=intval($_SESSION['uid']);$setsqlarr['pid']=intval($_REQUEST['pid']);if ($setsqlarr['uid']==0 || $setsqlarr['pid']==0 ) showmsg('参数错误!',1);$setsqlarr['start']=trim($_POST['start'])?$_POST['start']:showmsg('请填写开始时间!',1,$link);$setsqlarr['endtime']=trim($_POST['endtime'])?$_POST['endtime']:showmsg('请填写结束时间!',1,$link);$setsqlarr['school']=trim($_POST['school'])?$_POST['school']:showmsg('请填写学校名称!',1,$link);$setsqlarr['speciality']=trim($_POST['speciality'])?$_POST['speciality']:showmsg('请填写专业名称!',1,$link);$setsqlarr['education']=trim($_POST['education'])?$_POST['education']:showmsg('请选择获得学历!',1,$link);$setsqlarr['education_cn']=trim($_POST['education_cn'])?$_POST['education_cn']:showmsg('请选择获得学历!',1,$link); //看到这里有个插入表“qs_resume_education”的操作,将教育背景相关的字段入库 if (inserttable(table('resume_education'),$setsqlarr)) { check_resume($_SESSION['uid'],intval($_REQUEST['pid']));
2.这里看到insert入库了,可以尝试加个单引号,入库后就会消除转义字符。我们先继续跟进inserttables后的check_resume函数
//检查简历的完成程度function check_resume($uid,$pid){global $db,$timestamp,$_CFG;$uid=intval($uid);$pid=intval($pid);$percent=0;$resume_basic=get_resume_basic($uid,$pid);$resume_intention=$resume_basic['intention_jobs'];$resume_specialty=$resume_basic['specialty'];//获取教育经历,出数据库了$resume_education=get_resume_education($uid,$pid);if (!empty($resume_basic))$percent=$percent+15;if (!empty($resume_intention))$percent=$percent+15;if (!empty($resume_specialty))$percent=$percent+15;if (!empty($resume_education))$percent=$percent+15;if ($resume_basic['photo_img'] && $resume_basic['photo_audit']=="1" && $resume_basic['photo_display']=="1"){$setsqlarr['photo']=1;}else{$setsqlarr['photo']=0;}if ($percent<60){ $setsqlarr['complete_percent']=$percent; $setsqlarr['complete']=2;}else{ $resume_work=get_resume_work($uid,$pid); $resume_training=get_resume_training($uid,$pid); $resume_photo=$resume_basic['photo_img']; if (!empty($resume_work))$percent=$percent+13; if (!empty($resume_training))$percent=$percent+13; if (!empty($resume_photo))$percent=$percent+14; $setsqlarr['complete']=1; $setsqlarr['complete_percent']=$percent; require_once(QISHI_ROOT_PATH.'include/splitword.class.php'); $sp = new SPWord(); $setsqlarr['key']=$resume_basic['intention_jobs'].$resume_basic['recentjobs'].$resume_basic['specialty']; $setsqlarr['key']="{$resume_basic['fullname']} ".$sp->extracttag($setsqlarr['key']); $setsqlarr['key']=str_replace(","," ",$resume_basic['intention_jobs'])." {$setsqlarr['key']} {$resume_basic['education_cn']}"; $setsqlarr['key']=$sp->pad($setsqlarr['key']); if (!empty($resume_education)) { //遍历教育经历所有字段,加入到数组里 foreach($resume_education as $li) { $setsqlarr['key']="{$li['school']} {$setsqlarr['key']} {$li['speciality']}"; } } $setsqlarr['refreshtime']=$timestamp;}//这里对教育经历做了次更新操作,二次注入由此产生!updatetable(table('resume'),$setsqlarr,"uid='{$uid}' AND id='{$pid}'");updatetable(table('resume_tmp'),$setsqlarr,"uid='{$uid}' AND id='{$pid}'");
3.我们填写一份简历简单试验下,在教育经历处学校名称字段填写aa’
保存后发现报错语句:
0x04 漏洞证明
构造获取数据库用户相关信息的POC:
查看简历发现简历姓名变成了root@localhost:
查看sql语句发现更新语句是成功执行的:
最后,有兴趣的同学可以继续获取其它的管理员账户等相关字段的信息。
原文地址:
http://www.cnbraid.com/2016/02/19/sql3/

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