web——web4(80)——Bugku

Myth丶恋晨 2023-02-28 01:28 12阅读 0赞

## 0×00 靶场链接 ##

[http://123.206.87.240:8002/web4/][http_123.206.87.240_8002_web4]

##    0×01 题目描述 ##

看看源代码吧

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70][]

就是一个填写框

##    0×02 解题过程 ##

根据提示查看源代码

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 1][]

<html>
    <title>BKCTF-WEB4</title>
    <body>
    <div style="display:none;"></div>
    <form action="index.php" method="post" >
    看看源代码？<br>
    <br>
    <script>
    var p1 = '%66%75%6e%63%74%69%6f%6e%20%63%68%65%63%6b%53%75%62%6d%69%74%28%29%7b%76%61%72%20%61%3d%64%6f%63%75%6d%65%6e%74%2e%67%65%74%45%6c%65%6d%65%6e%74%42%79%49%64%28%22%70%61%73%73%77%6f%72%64%22%29%3b%69%66%28%22%75%6e%64%65%66%69%6e%65%64%22%21%3d%74%79%70%65%6f%66%20%61%29%7b%69%66%28%22%36%37%64%37%30%39%62%32%62';
    var p2 = '%61%61%36%34%38%63%66%36%65%38%37%61%37%31%31%34%66%31%22%3d%3d%61%2e%76%61%6c%75%65%29%72%65%74%75%72%6e%21%30%3b%61%6c%65%72%74%28%22%45%72%72%6f%72%22%29%3b%61%2e%66%6f%63%75%73%28%29%3b%72%65%74%75%72%6e%21%31%7d%7d%64%6f%63%75%6d%65%6e%74%2e%67%65%74%45%6c%65%6d%65%6e%74%42%79%49%64%28%22%6c%65%76%65%6c%51%75%65%73%74%22%29%2e%6f%6e%73%75%62%6d%69%74%3d%63%68%65%63%6b%53%75%62%6d%69%74%3b';
    eval(unescape(p1) + unescape('%35%34%61%61%32' + p2));
    </script>
    
    <input type="input" name="flag" id="flag" /> 
    <input type="submit" name="submit" value="Submit" />
    </form>
    </body>
    </html>

p1，p2似乎都是URL编码，就在线解码一下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 3][]

p1，p2解码后

function checkSubmit(){var a=document.getElementById("password");if("undefined"!=typeof a){if("67d709b2b
    
    aa648cf6e87a7114f1"==a.value)return!0;alert("Error");a.focus();return!1}}document.getElementById("levelQuest").onsubmit=checkSubmit;

然后把整段源代码整合一下如下

<html>
    <title>BKCTF-WEB4</title>
    <body>
    <div style="display:none;"></div>
    <form action="index.php" method="post" >
    看看源代码？<br>
    <br>
    <script>
    var p1 = ' function checkSubmit()
    {
    var a=document.getElementById("password");
       if("undefined"!=typeof a)
       {
         if("67d709b2b';
    var p2 = ' aa648cf6e87a7114f1"==a.value)
         return!0;
         alert("Error");
         a.focus();
         return!1
       }
    }
        document.getElementById("levelQuest").onsubmit=checkSubmit;';
    eval(unescape(p1) + unescape('54aa2' + p2));
    </script>
    
    <input type="input" name="flag" id="flag" /> 
    <input type="submit" name="submit" value="Submit" />
    </form>
    </body>
    </html>

然后进行一下代码审计，发现最重要的一句代码是这一句

eval(unescape(p1) + unescape('54aa2' + p2));

意思是将p1解码+‘54aa2’+p2解码

> 即67d709b2b54aa2aa648cf6e87a7114f1

输入到框中即可得到flag

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 4][]

##    0×03 知识点 ##

[URL编码][URL]

[http_123.206.87.240_8002_web4]: http://123.206.87.240:8002/web4/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70]: /images/20230209/79d845d3e17042fc9e70e534988fda4f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 1]: /images/20230209/576d1d5b61854565891a4e57d4e25702.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 2]: /images/20230209/ddf10ef6e6c04f58a928bb4950489d3b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 3]: /images/20230209/cd59569e8a3d412b90ea4055397cf3cc.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk2NTU5Nw_size_16_color_FFFFFF_t_70 4]: /images/20230209/14e4a8b88a0c4af4831537668a9d2323.png
[URL]: https://www.runoob.com/tags/html-urlencode.html