Serverless Authorization: A Practical Guide

Gilad David Maayan
Published 05/04/2023
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Serverless Authorization - A Practical GuideServerless authorization refers to a method of securing serverless applications, where the underlying infrastructure is managed by a cloud provider and runs functions in response to events. This authorization process ensures that only authorized users or systems can access the resources, data, or functions in the serverless application.

Serverless authorization is important because it protects against unauthorized access, data breaches, and other security threats to serverless applications. Additionally, serverless authorization helps enforce access control policies, ensuring that users can only perform actions that are authorized based on their role or permissions.

By implementing proper serverless authorization, organizations can meet security and compliance requirements, such as data privacy regulations, and provide a secure environment for their customers and users.

Serverless authorization can also help with serverless monitoring and debugging by providing auditable logs of who accessed the application and what actions they performed. This can provide valuable insights into the behavior of the application and help identify any potential security threats. By tracking access to specific resources, serverless authorization can help with debugging by providing a clear view of the source of the problem, such as incorrect permissions setting or a misconfigured function. These logs can also be used for troubleshooting and performance analysis to optimize the serverless application.

Serverless Authorization with AWS Lambda

When building a serverless application with AWS Lambda, you can use API Gateway as-is or create a custom authorizer to implement authorization. Custom authorizers are a type of Lambda function that you create and connect to API Gateway to control access to an API. It allows you to implement fine-grained authentication and authorization logic, beyond what is provided by API Gateway alone, by allowing you to verify incoming API requests and determine whether they should be allowed or denied.

Using a custom authorizer in a serverless application built with AWS Lambda provides several benefits:

  • Fine-grained authorization: Custom authorizers allow for precise control over which users or applications can access which resources. This level of control is not possible with the default AWS security mechanisms.
  • Reusability: It can be used across multiple API endpoints, making it easy to apply the same security logic to different parts of the application.
  • Improved performance: It runs as a separate Lambda function, so it won’t impact the performance of the main application. This can be especially important in high-traffic environments where response times must be fast.
  • Better security: Custom authorizers provide an additional layer of security that can help protect against unauthorized access to sensitive data. They also allow for the implementation of custom security logic, such as rate limiting, that can help prevent against security threats like denial-of-service attacks.
  • Decoupled security logic: The security logic of an application can be separated from its business logic. This makes it easier to maintain and evolve the security of an application over time without having to modify its core code.



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Lambda Authorizer Auth Workflow

Here is a diagram illustrating the typical authorization workflow of a Lambda authorizer.


The authorization workflow of a Lambda authorizer in API Gateway typically involves the following steps:

  1. API request: A client sends a request to an API endpoint.
  2. API Gateway trigger: The request triggers API Gateway, which is configured to use a Lambda authorizer.
  3. Lambda authorizer invocation: API Gateway invokes the Lambda authorizer function, passing along information about the incoming request.
  4. Authorization logic: The Lambda authorizer function implements the authorization logic, such as checking the request against a database of authorized users or validating an API key.
  5. Authorization response: The Lambda authorizer function returns an authorization response to API Gateway, indicating whether the request is authorized or not.
  6. API response: Based on the authorization response from the Lambda authorizer, API Gateway either allows or denies the incoming request. If the request is allowed, API Gateway invokes the associated API method (e.g., a Lambda function) that generates a response. If the request is denied, AWS API Gateway will return an error response to the client.

Tutorial: Configure a Lambda Authorizer Using the API Gateway Console

Once you’ve created a Lambda function and verified that it is working, you can configure the Lambda authorizer using the following steps:

  1. Create a new Lambda function: Log in to the Management Console and go to the Lambda service. Create a new function, choosing the Author from scratch option and selecting a runtime that’s compatible with your authorizer logic (e.g., Node.js). Name and save your function.
  2. Implement your authorization logic: In the code editor, implement your authorization logic using the runtime you selected. The code should return a policy document indicating whether the incoming request is authorized or not.
  3. Create a new API: Go to API Gateway and create a new API. Choose the REST API option and select Create API.
  4. Create an API resource: In the Create new API wizard, create a new resource for your API by clicking the Create Resource button.
  5. Create a new method: In the Actions menu, select Create Method and choose the HTTP method (e.g., GET, POST) for your API endpoint. Then, choose Lambda Function for the “integration type” and select the region where your Lambda function was created.
  6. Add your Lambda function: In the Lambda Function configuration section, enter the Lambda function’s name and click Save.
  7. Configure the authorizer: In the Authorization section, choose Lambda Authorizer as the type and select the name of your Lambda authorizer function.
  8. Deploy your API: In the Actions menu, select Deploy API and choose a deployment stage. Give your deployment a name and click Deploy.
  9. Test your API: In the Stages section, click on the named deployment stage to see your API’s invocation URL. Use this URL to send a test request to your API and verify that your authorizer is working as expected.

That’s it! You’ve successfully configured a Lambda authorizer for your API Gateway API. You can now use your authorizer to control the use of your API and implement custom authorization logic.

Note: The steps in this tutorial provide a basic overview of the process for configuring a Lambda authorizer. Depending on your use case, you may need to perform additional configuration steps, such as setting up a custom domain name for your API or adding additional security measures like SSL certificates.


In conclusion, serverless authorization is a key aspect of building secure, scalable, and cost-effective APIs in a cloud-based environment. By leveraging the benefits of serverless computing, organizations can ensure that their APIs are protected against unauthorized access, while also benefiting from improved security, scalability, flexibility, and cost-effectiveness.

With the help of this guide, developers can now easily implement serverless authorization using AWS Lambda and API Gateway, and start building secure, high-performing APIs that meet the demands of their users.


About the Author

Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Imperva, Samsung NEXT, NetApp and Check Point, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership. Today he heads Agile SEO, the leading marketing agency in the technology industry. Connect with him on LinkedIn.


Disclaimer: The author is completely responsible for the content of this article. The opinions expressed are their own and do not represent IEEE’s position nor that of the Computer Society nor its Leadership.