Implementation of proper data validation for HTML code
import express from 'express';
const app = express();
app.post('/api/data', (req, res) => {
const { htmlCode } = req.body;
res.send(`${htmlCode}`);
});
app.listen(3000, () => {
console.log('Server is running on port 3000');
});
The vulnerability in this code is a lack of data validation for the
htmlCode field that is received in the request body. This field is directly used to construct an HTML response without any validation or sanitization.
This means that an attacker can inject arbitrary HTML code into the
htmlCode field, which will be rendered as part of the response. This can lead to various security issues, including:
1. Cross-Site Scripting (XSS): An attacker can inject malicious scripts that will be executed by the victim's browser, allowing them to steal sensitive information, perform actions on behalf of the user, or modify the content of the page.
2. Log File Injection: An attacker can inject special characters that can manipulate log files, potentially leading to unauthorized access or information disclosure.
3. Remote Command Execution: By injecting specific commands, an attacker can execute arbitrary code on the server, leading to complete compromise of the system.
4. Insecure File Fetching: An attacker can inject URLs to fetch arbitrary files from external sources, potentially leading to the execution of malicious content or unauthorized access to sensitive files.
Additionally, the vulnerability allows an attacker to create delivery requests for non-existent QR codes. This is because the code does not validate the
idQR field, which accepts text strings with random characters. This can lead to unnecessary processing and resource consumption.
To mitigate this vulnerability, it is recommended to implement server-side data validation and sanitization. This can include:
1. Validating the data type and format of the
htmlCode field to ensure it contains only safe and expected content.
2. Sanitizing the
htmlCode field to remove any potentially malicious HTML tags or scripts.
3. Implementing proper input validation and filtering for the
idQR field to only accept valid input and prevent unnecessary processing.
By implementing these measures, the code can prevent the injection of malicious HTML code and ensure the security and integrity of the application.
import express from 'express';
import { sanitize } from 'sanitize-html';
const app = express();
app.use(express.json());
app.post('/api/data', (req, res) => {
const { htmlCode } = req.body;
// Sanitize the HTML code
const sanitizedHtmlCode = sanitize(htmlCode);
res.send(`${sanitizedHtmlCode}`);
});
app.listen(3000, () => {
console.log('Server is running on port 3000');
});
The fixed code addresses the vulnerability by implementing data validation on the server side. Here's how the code works:
1. The code imports the necessary modules, including the
express framework and the
sanitize-html library for sanitizing HTML code.
2. An instance of the Express application is created using
express().
3. The application is configured to parse JSON data using
express.json() middleware.
4. A POST route is defined at
/api/data to handle incoming requests.
5. Inside the route handler, the HTML code is extracted from the request body using destructuring assignment and stored in the
htmlCode variable.
6. The
sanitize function from the
sanitize-html library is used to sanitize the HTML code. This function removes any potentially dangerous elements or attributes from the code.
7. The sanitized HTML code is then wrapped in a
<div> element and sent as the response using the
res.send() method.
8. The server is started and listens on port 3000.
By using the
sanitize-html library to sanitize the HTML code, the fixed code ensures that any potentially malicious code is removed before it is rendered on the site. This prevents the injection of valid HTML code that could be interpreted by the receiving site.