Introduction

In this tutorial, our goal is to help you understand how to secure your serverless applications. Serverless applications, due to their distributed nature, have unique security challenges and considerations. We will walk through several best practices and techniques to help ensure the security of your serverless apps.

By the end of this tutorial, you will learn:

• What serverless application security entails
• How to implement authentication and authorization
• How to manage dependencies securely
• And how to handle error and exception securely

This tutorial assumes that you have a basic understanding of serverless architecture and experience with a serverless platform like AWS Lambda, Google Cloud Functions, or Azure Functions.

Step-by-Step Guide

1. Implementing Authentication and Authorization

One of the first steps in securing serverless applications is to ensure only authenticated and authorized users can access your functions.

For authentication, consider using JWT (JSON Web Tokens) or integrating a service like AWS Cognito or Auth0. This ensures that only authenticated users can access your application.

For authorization, ensure that authenticated users can only access resources and operations they're permitted to. This is typically implemented using IAM (Identity and Access Management) roles.

2. Dependency Management

Dependencies can be a common source of vulnerabilities in serverless applications. Always be sure to:

• Use the latest versions of your dependencies to ensure you have the most recent security patches
• Regularly check for and update any dependencies with known vulnerabilities
• Follow the principle of least privilege in your dependencies. Only give them the permissions they need to function

3. Error and Exception Handling

Poorly handled errors can expose sensitive information. Always catch and handle exceptions, and log errors for debugging purposes. However, never expose stack traces to the end user.

Code Examples

1. Authentication with JWT

const jwt = require('jsonwebtoken');

exports.handler = function(event, context, callback) {
    const token = event.authorizationToken;

    // Verify the JWT token
    jwt.verify(token, 'your-secret-key', function(err, decoded) {
        if (err) {
            callback('Unauthorized');
        } else {
            callback(null, generatePolicy(decoded, 'Allow', event.methodArn));
        }
    });
};

// Helper function to generate an IAM policy
function generatePolicy(principalId, effect, resource) {
    const authResponse = {};
    authResponse.principalId = principalId;
    if (effect && resource) {
        const policyDocument = {};
        policyDocument.Version = '2012-10-17';
        policyDocument.Statement = [];
        const statementOne = {};
        statementOne.Action = 'execute-api:Invoke';
        statementOne.Effect = effect;
        statementOne.Resource = resource;
        policyDocument.Statement[0] = statementOne;
        authResponse.policyDocument = policyDocument;
    }
    return authResponse;
}

In the above example, we use the jsonwebtoken library to verify the JWT token. If the token is valid, we generate an IAM policy allowing the user to invoke the API.

Summary

In this tutorial, we covered how to secure serverless applications. We discussed authentication and authorization, secure dependency management, and safe error handling.

To further your learning, explore topics such as data encryption, secure environment variables, and logging and monitoring for serverless applications. You can also review the security best practices provided by your serverless platform provider.

Practice Exercises

1. Implement an IAM role that only allows a Lambda function to write to a specific S3 bucket in your AWS account.

2. Update the JWT authentication example to use a secret key stored securely (e.g., using AWS Secrets Manager or environment variables).

3. Implement error handling for a Lambda function that hides the stack trace from the end user but logs it for debugging purposes.

Remember, practice is key to mastering any concept. Happy coding!