AWS Certified Security – Specialty — Question 329

An Amazon API Gateway API invokes an AWS Lambda function that needs to interact with a software-as-a-service (SaaS) platform. A unique client token is generated in the SaaS platform to grant access to the Lambda function. A security engineer needs to design a solution to encrypt the access token at rest and pass the token to the Lambda function at runtime.

Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Store the client token as a secret in AWS Secrets Manager. Use the AWS SDK to retrieve the secretin the Lambda function.
• B. Configure a token-based Lambda authorizer in API Gateway.
• C. Store the client token as a SecureString parameter in AWS Systems Manager Parameter Store. Use the AWS SDK to retrieve the value of the SecureString parameter in the Lambda function.
• D. Use AWS Key Management Service (AWS KMS) to encrypt the client token. Pass the token to the Lambda function at runtime through an environment variable.

Correct answer: C

Explanation

AWS Systems Manager Parameter Store with a SecureString parameter provides secure, encrypted storage of sensitive tokens at rest using AWS KMS, and standard parameters are offered at no additional charge, making it the most cost-effective solution. AWS Secrets Manager is more expensive because it charges a flat monthly fee per secret in addition to API request fees. Using environment variables with AWS KMS or setting up an API Gateway authorizer are either less secure, more complex to manage, or do not address the integration requirements between the Lambda function and the external SaaS platform.