ectf2022 | CYB3RM3

eCTF'22 : 24h
05/03/22 - 06/03/22

CTF Scoreboard https://ectf.nitk.ac.in/scoreboard
CTF Challenges https://ectf.nitk.ac.in/challenges

Final Score

DATE : 05/03/22 10h30 UTC+1, to 06/03/22 10h30 UTC+1.

FINAL SCORE : 1854

SCOREBOARD : 89/311

My CTF playing time : 05/03/22 10h30 to 05/03/22 18h

Modo : Solo (pseudo : R3X, Team : eCTF_R3X)

I finished in 89th position out of 311 for this CTF challenge :

I solved the following chalenges :

Here's a view a the available challenges (except Blue Team challenges which were no longer available post event) :

I'll put only challenges i got through in the next sections.

Easypeasy - Join our Discord

SCORE: 50

Looking for an interesting channel :

Here we go, i get the first easy flag : CTF{Welcome_to_ectf22}

Easypeasy - Sanity Check

SCORE: 50

The flag appears to us directly : CTF{Welcome}

Web - You're too blind to see

SCORE: 300

RESSOURCE : website link : https://chinmayasharma-hue.github.io/CTF2022.gitbhub.io/

Open the link of the website :

Ok, let's look for the source :

<html>
<!-- bmV2ZXJnb25uYWxldHlvdWRvd24wMTIyQGdtYWlsLmNvbSBrbm93cyB0aGUgcGFzc3dvcmQ -->
<head>
    <title>Login Form</title>
    <link rel="stylesheet" href="css/style.css">
</head>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/forge/0.8.2/forge.all.min.js"></script>

<script type="text/Javascript">
    function generateHash(plainText) {
        var md = forge.md.sha256.create();
        md.start();
        md.update(plainText, "utf8");
        var hashText = md.digest().toHex();
        return hashText;
    }
    const loginForm = document.getElementById("login");
    const loginButton = document.getElementById("login-form-submit");

    function checkLogDetails() {
        var username = document.getElementById("Uname").value;
        var password = document.getElementById("Pass").value;
        if (username == "Rick Astley" && generateHash(password) == "1b638a7a9a56a4485ebd95816d1d8abf0576cdbf39854c6dd5cb47c3c53f48be") {
            redirect_site = 'redirect'+ password + '.html';
            window.open(redirect_site, '_blank');
        } else {
            window.open('https://www.youtube.com/watch?v=dQw4w9WgXcQ');
        }
    }
</script>

<body>
    <h2>Login Page</h2>
    <div align="center" class='login'>
        <form id="login" method="get" onsubmit="checkLogDetails()">
            <label><b>User Name
                </b>
            </label><br><br>
            <input type="text" name="Uname" id="Uname" placeholder="Username">
            <br><br>
            <label>
                <b>Password</b>
            </label><br><br>
            <input type="Password" name="Pass" id="Pass" placeholder="Password">
            <br><br><br><br>
            <input type="submit" value="Login" id="login-form-submit">
            <br><br>
        </form>
    </div>
</body>

</html>

Found a comment to seems to be Base64 :

It's said that "[email protected]" knows the password. Let's write an email to this person asking the flag :

I got the flag : CTF{never_gonna_say_goodbye}

Web - Hack the Auth

SCORE: 300

RESSOURCE : website link : https://wec-ctf-2022-web.herokuapp.com/q1

Let's take a look at this website :

It's a relatively simple page, what is his source :

<!DOCTYPE html>
<html>
   <head>
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <title>WEC</title>
   </head>
<body>
    <div> Hello world </div>

    <input type="text" name="username" placeholder="username">
    <input type="password" name="password" placeholder="password">
    <button onclick="userAuthentication()">Login</button>
    <script type="text/javascript">
        var sha256 = function sha256(ascii) {
            function rightRotate(value, amount) {
                return (value>>>amount) | (value<<(32 - amount));
            };
            
            var mathPow = Math.pow;
            var maxWord = mathPow(2, 32);
            var lengthProperty = 'length'
            var i, j;
            var result = ''
        
            var words = [];
            var asciiBitLength = ascii[lengthProperty]*8;

            var hash = sha256.h = sha256.h || [];
            var k = sha256.k = sha256.k || [];
            var primeCounter = k[lengthProperty];

        
            var isComposite = {};
            for (var candidate = 2; primeCounter < 64; candidate++) {
                if (!isComposite[candidate]) {
                    for (i = 0; i < 313; i += candidate) {
                        isComposite[i] = candidate;
                    }
                    hash[primeCounter] = (mathPow(candidate, .5)*maxWord)|0;
                    k[primeCounter++] = (mathPow(candidate, 1/3)*maxWord)|0;
                }
            }
            
            ascii += '\x80'
            while (ascii[lengthProperty]%64 - 56) ascii += '\x00' 
            for (i = 0; i < ascii[lengthProperty]; i++) {
                j = ascii.charCodeAt(i);
                if (j>>8) return;
                words[i>>2] |= j << ((3 - i)%4)*8;
            }
            words[words[lengthProperty]] = ((asciiBitLength/maxWord)|0);
            words[words[lengthProperty]] = (asciiBitLength)

            for (j = 0; j < words[lengthProperty];) {
                var w = words.slice(j, j += 16);
                var oldHash = hash;
                hash = hash.slice(0, 8);
                
                for (i = 0; i < 64; i++) {
                    var i2 = i + j;

                    var w15 = w[i - 15], w2 = w[i - 2];

                    var a = hash[0], e = hash[4];
                    var temp1 = hash[7]
                        + (rightRotate(e, 6) ^ rightRotate(e, 11) ^ rightRotate(e, 25)) 
                        + ((e&hash[5])^((~e)&hash[6])) 
                        + k[i]
                        + (w[i] = (i < 16) ? w[i] : (
                                w[i - 16]
                                + (rightRotate(w15, 7) ^ rightRotate(w15, 18) ^ (w15>>>3)) 
                                + w[i - 7]
                                + (rightRotate(w2, 17) ^ rightRotate(w2, 19) ^ (w2>>>10)) 
                            )|0
                        );
                    var temp2 = (rightRotate(a, 2) ^ rightRotate(a, 13) ^ rightRotate(a, 22)) 
                        + ((a&hash[1])^(a&hash[2])^(hash[1]&hash[2])); 
                    
                    hash = [(temp1 + temp2)|0].concat(hash); 
                    hash[4] = (hash[4] + temp1)|0;
                }
                
                for (i = 0; i < 8; i++) {
                    hash[i] = (hash[i] + oldHash[i])|0;
                }
            }
            
            for (i = 0; i < 8; i++) {
                for (j = 3; j + 1; j--) {
                    var b = (hash[i]>>(j*8))&255;
                    result += ((b < 16) ? 0 : '') + b.toString(16);
                }
            }
            return result;
        };

        var userAuthentication = function() {
            var username = document.getElementsByName('username')[0].value;
            var password = document.getElementsByName('password')[0].value;
            var hash = sha256(password);
            if(hash === "dfbec338b51c5643ba481625e1075236d3a9a07fbd6393763f253e99024958a4" && username === "admin") {
                window.location = "./q1?username=admin&password=" + password;
            } else {
                alert("Invalid username or password");
            }
        };
    </script>
</body></html>

There is an interesting "userAuthentication" function directly in the webpoge. Can we tried to get the clear text of the hash ?

Yes, Crackstation knows this hash :

So i can used the harcode username and the found password to log on the form :

Ok, seems there is one more thing to do. Checked the cookies :

I found the flag there : CTF{SHA256_AND_WEB}

Web - Favourite Website

SCORE: 300

RESSOURCE : website link : https://wec-ctf-2022-web.herokuapp.com/q2

What's the webiste looks :

ok, let's refresh the pages several times to see what does the counter :

Ok, what's up in the cookies ?

Ok, it's all base64 message, let's decode those :

Tired of finding cookies?f9a2a23e-5333-4916-9a6d-a2f8c06bb75a
ÃÜ
[...]
WEC NITK CTF is the best
[...]
still cannot solve this task?times=00000007&id=0075a5e8-e60f-4377-859e-d27f149b0c537
[...]

One of the cookies seems intersting. Let's modify this cookie with ?times=12893422 :

Then refreshed the page :

Flag : CTF{C@@kie$_@re_the_be$t}

Osint - Vacation

SCORE: 200

I turn a lot with no success until i found the @tig3r_and_b3ar on google as an Instagram account.

Only one photo, but nothing interesting.

Checking followers : 6, time loss.

Checking the following : 1 account "ashlynbardot" who is a Photographer. Seems i found the right person. The profile say "contact me at [email protected]".

Like the previous challenge with the email, i sent this email address an hello mail too :

It gives me the flag as intended : CTF{f0und_th3_fl@g}

RE-pwn - Ligts off

SCORE: 300

RESSOURCE :

nc40.114.6.1675555

main.c

Let's see the chall :

┌──(kali㉿kali)-[~]
└─$ nc 40.114.6.167 5555
Starting!
Provide Your Magic Key:

2665
ACCESS DENIED

By trial error for some values :

┌──(kali㉿kali)-[~]
└─$ nc 40.114.6.167 5555
Starting!
Provide Your Magic Key:
0
ACCESS GRANTED O_o
CTF{L1Ghts=O}

Flag : CTF{L1Ghts=O}

Let's move to the next challenge.

Crypto - TVA's Trap

SCORE : 300

RESSOURCE : 8-6-4.txt

Opened the txt file :

After trying multiple recipe in Cyberchef, i saw that 3 Base64 decode give me a result looking more to something sweeet. So i continue with 8 base64 decode :