5 Application Security Tips for Developers
Tags: programming, security, webdev
Published: 2023-01-20 13:40:50

As a developer, it is essential to ensure the applications you build are secure and protect sensitive data from potential attacks. Today it's more important than ever to be aware of the latest security threats and best practices. 

However, it can be difficult to know where to start. That's why I've compiled a list of the top five application security tips for developers to keep in mind when creating your next application. By following these tips, you can help ensure that your applications are secure and that sensitive data is protected from potential threats.

## 1. Input Validation

One of the most common ways that attackers can exploit vulnerabilities in an application is by injecting malicious code into input fields. To prevent this, ensure that all user input is properly validated and sanitized before it is used in any database queries or other sensitive operations. For example, using prepared statements in SQL can help prevent SQL injection attacks.

```javascript
//Example of prepared statement in Node.js
const mysql = require('mysql');
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'password',
  database: 'mydb'
});

connection.connect();

const userId = 1;
const sql = 'SELECT * FROM users WHERE id = ?';
connection.query(sql, [userId], function (error, results, fields) {
  if (error) throw error;
  console.log('The user is: ', results[0]);
});

connection.end();
```

In the above example, the user input (userId) is passed as a parameter to the prepared statement, rather than being concatenated into the SQL query string, which helps prevent SQL injection attacks.

Other types of attacks that can be prevented by input validation are cross-site scripting (XSS) attacks, command injection attacks, path traversal attacks, and many more.

Read more: [3 Quick Tips for Input Validation](https://dev.to/dennistraub/3-quick-tips-for-input-validation-25jn)

### 2. Secure Communications

Any sensitive data that is transmitted between the client and server, or between different parts of the application, must be properly encrypted to prevent eavesdropping or tampering. This includes data transmitted via HTTP, HTTPS, or other protocols. For example, use HTTPS instead of HTTP to encrypt all communication between the browser and the server.

```javascript
//Example of creating a HTTPS server in Node.js
const https = require('https');
const fs = require('fs');

const options = {
  key: fs.readFileSync('server.key'),
  cert: fs.readFileSync('server.crt')
};

https.createServer(options, (req, res) => {
  res.writeHead(200);
  res.end('Hello World\n');
}).listen(8000);
```

In this example, a private key and certificate are used to create an HTTPS server, which encrypts all communication between the browser and the server.

It is important to note that a production-ready HTTPS server would need a valid signed certificate from a trusted certificate authority (CA). The above example uses a self-signed certificate for demonstration purposes only.

### 3. Access Control

Ensure that only authorized users have access to sensitive data or functionality within the application. This can be accomplished by implementing role-based access control, where different users have different levels of access based on their role within the organization. For example, use JWT token based authentication and authorization to ensure that only authenticated users can access the application's sensitive functionality.

```javascript
//Example of JWT token based authentication in Node.js
const jwt = require('jsonwebtoken');
const secret = 'mysecretkey';

const token = jwt.sign({ user: 'myuser' }, secret);
console.log(token);

const decoded = jwt.verify(token, secret);
console.log(decoded);
```

In the above example, a JWT token is generated for a user and is signed with a secret key. The token is then verified by the server and the user is granted access to the application's sensitive functionality.

It is important to note that this is a basic example and a production-ready authentication system would need to handle other security considerations such as token refresh, revocation and storage of secrets.

### 4. Error Handling

Properly handling errors and exceptions can prevent attackers from gaining access to sensitive information or exploiting vulnerabilities in the application. For example, make sure that stack traces or other pieces of debugging information are not displayed to the user in the event of an error or exception.

```javascript
//Example of error handling in Node.js
try {
   // code that may throw an exception
   const result = someFunction();
   if (!result) {
       throw new Error('someFunction returned false');
   }
   // continue with application logic
} catch(err) {
   // handle the exception
   console.log(err);
   res.status(500).send('Internal Server Error');
}
```

In the above example, the code that may throw an exception is wrapped in a try-catch block. If an exception is thrown, it is caught and handled by the catch block. This way, the user is not presented with any sensitive debugging information and instead receives a standardized message.

### 5 Regularly Update and Patch

Keep your application and its dependencies up to date with the latest security patches and updates. This will help to prevent known vulnerabilities from being exploited. For example, use a dependency manager like npm, pip or composer to keep your application dependencies up to date.

```bash
# Example of updating dependencies in Node.js using npm
npm update

# Example of updating dependencies in Python using pip
pip install --upgrade package-name

# Example of updating dependencies in PHP using composer
composer update
```

In the above examples, the dependencies are updated using the package manager of the respective programming language. This ensures that the application is using the latest versions of the dependencies which often include security patches.

## Summary

In conclusion, following these application security tips will help to ensure that the applications you build are secure and protect sensitive data from potential attacks. 

Keep in mind that security should always be a part of the development process and not an afterthought. The earlier you start thinking about security, the more effective it will be. Security is not just a one-time effort, but an ongoing process. 

As a developer, you should stay vigilant and keep your skills sharp by following the latest industry developments in application security. The key is to not just rely on a single security measure but to implement a combination of different techniques to ensure the safety of your application.

Do you have any security tips for developers? Let me know in the comments below 👇

Learn more: [3 Quick Tips for Input Validation](https://dev.to/dennistraub/3-quick-tips-for-input-validation-25jn)