adding authorizers and cors to CloudFormation json

ONLINECAST

3 min read

·

06-10-2024

7

0

Share

Securing Your API with Authorizers and CORS in CloudFormation

Building a secure and accessible API is paramount in today's cloud-centric world. This involves two crucial elements: authorization, which controls who can access your API resources, and CORS (Cross-Origin Resource Sharing), which enables secure communication between your API and different origins (e.g., websites).

This article guides you through implementing both authorizers and CORS configurations directly within your CloudFormation JSON templates, ensuring a robust and secure API setup.

The Problem: Securing Your API and Enabling Cross-Origin Access

Imagine you've deployed a fantastic new API, but you need to restrict access to specific users or functionalities. You also want to allow websites from different domains to interact with your API securely. Manually configuring these settings can be tedious and prone to errors.

This is where CloudFormation comes in. By using CloudFormation templates, we can automate the process of configuring authorizers and CORS, simplifying the deployment and ensuring consistency.

The Solution: CloudFormation to the Rescue

Let's take a look at a simple example of how to implement authorizers and CORS in CloudFormation:

Resources:
  MyAPI:
    Type: 'AWS::Serverless::Api'
    Properties:
      Name: MyAPI
      DefinitionBody:
        openapi: 3.0.1
        info:
          title: My API
          version: 1.0.0
        paths:
          /my-resource:
            get:
              x-amazon-apigateway-integration:
                httpMethod: GET
                integrationType: aws_proxy
                uri: arn:aws:apigateway:REGION:ACCOUNT_ID:restapis/API_ID/my-lambda-function
                passthroughBehavior: when_no_match
              authorizer: MyAuthorizer
  MyAuthorizer:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: index.handler
      Runtime: nodejs18.x
      CodeUri: s3://my-bucket/my-authorizer-code.zip
      Policies:
        - AWSLambdaBasicExecutionRole
  MyCorsConfig:
    Type: 'AWS::Serverless::Api'
    Properties:
      Name: MyAPI
      CorsConfiguration:
        AllowOrigins:
          - https://www.example.com
          - https://www.another-example.com
        AllowMethods:
          - GET
          - POST
        AllowHeaders:
          - Content-Type
          - Authorization
        AllowCredentials: true

Explanation:

1. Authorizer (MyAuthorizer): We define a Lambda function (MyAuthorizer) as an authorizer for the API. This function will be responsible for validating user credentials and granting access based on the result.
2. API Gateway Integration (/my-resource): The x-amazon-apigateway-integration property specifies that the /my-resource endpoint will be integrated with a Lambda function (my-lambda-function). We also configure the authorizer property to use MyAuthorizer for authentication.
3. CORS Configuration (MyCorsConfig): We create a separate CloudFormation resource MyCorsConfig that specifically configures CORS for our API. This allows you to specify the origins, methods, headers, and credentials that are allowed for cross-origin requests.

Key Insights and Considerations

• Authorizer Types: AWS API Gateway offers different authorizer types like Lambda authorizers, Cognito user pools, and IAM authorizers, each catering to different use cases. Choose the best option based on your security needs and existing infrastructure.
• CORS Flexibility: You can set up CORS rules at the API level, resource level, or even method level, offering granular control over cross-origin access.
• Security Best Practices: Always follow security best practices when implementing authorizers and CORS. For instance, use strong authentication mechanisms and avoid granting unnecessary permissions.
• CloudFormation Benefits: Using CloudFormation for these configurations brings numerous advantages:
  • Automation: Simplifies deployment and ensures consistency across environments.
  • Version Control: Tracks changes to your API security settings.
  • Infrastructure as Code: Allows for easy replication and updates.

Conclusion

By leveraging CloudFormation, you can effectively manage authorizers and CORS configurations for your API, enhancing security and accessibility without sacrificing simplicity. This approach ensures a robust and scalable API infrastructure that adapts to your evolving security requirements.

Further Exploration:

• AWS API Gateway Authorizer Documentation: https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-integrate-with-authorizers.html
• AWS API Gateway CORS Documentation: https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-cors.html
• CloudFormation Template Examples: https://github.com/aws-samples/serverless-application-model/tree/master/examples