3.2.3. Serverless Security (Lambda Permissions, API Gateway Authorization)
First Principle: Securing serverless applications involves strictly controlling permissions for Lambda functions (execution roles) and implementing robust authorization for API Gateway endpoints, ensuring least privilege and secure access.
Serverless applications (e.g., AWS Lambda and Amazon API Gateway) shift much of the underlying infrastructure security responsibility to AWS. However, security specialists are still responsible for configuring access and permissions for their application code and endpoints.
Key Security Best Practices for Serverless Applications:
- Lambda Permissions (Execution Role):
- Concept: Each Lambda function requires an IAM execution role that grants it the permissions it needs to access other AWS services (e.g., read from DynamoDB, write to S3).
- Implementation: Apply the Principle of Least Privilege by granting only the essential permissions (e.g.,
dynamodb:GetItemon a specific table).
- API Gateway Authorization:
- Purpose: Control who can access your API Gateway endpoints.
- Options:
- IAM Authorization: For internal APIs accessed by IAM users or roles.
- Amazon Cognito User Pool Authorizers: For public-facing APIs with user authentication.
- Lambda Authorizers (Custom Authorizers): For highly customized authorization logic.
- Secure Secrets Management: Use AWS Secrets Manager or AWS Systems Manager Parameter Store for application secrets.
- VPC Integration: Configure Lambda functions to run within a VPC for private access to resources and outbound internet control.
Scenario: You are securing a serverless application with an API Gateway frontend and Lambda functions as its backend. The Lambda functions need to access sensitive data in DynamoDB, and the API Gateway needs to authenticate users.
Reflection Question: How does securing serverless applications by strictly controlling Lambda permissions (execution roles with least privilege) and implementing robust authorization for API Gateway endpoints (e.g., Cognito Authorizers) fundamentally protect your application's execution environment and data?