Securing AWS APIs

What are AWS APIs?

AWS APIs (Application Programming Interfaces) are a set of programming instructions and standards for accessing AWS services. These APIs allow developers to interact programmatically with AWS services, such as EC2, S3, RDS, and more, to automate tasks, manage resources, and integrate AWS capabilities into applications.

How to Control Your Application’s Access to AWS APIs

Controlling your application’s access to AWS APIs involves several strategies to ensure security, manageability, and compliance. Here are the key components and methods to control access:

1. IAM Policies

IAM (Identity and Access Management) policies are used to define permissions for AWS services and resources. These policies control what actions are allowed or denied for users, groups, roles, and services.

  • Identity-Based Policies: Attach policies to IAM users, groups, or roles to specify what actions they can perform.
    • Example: Allow an application role to access S3 buckets.
  • Resource-Based Policies: Attach policies directly to AWS resources like S3 buckets, Lambda functions, or SQS queues.
    • Example: Allow cross-account access to an S3 bucket.

2. IAM Roles and Temporary Security Credentials

Use IAM roles to grant temporary access to AWS resources. Roles are assumed by trusted entities (users, applications, services) and provide temporary security credentials.

  • AssumeRole: Applications can assume roles to gain temporary access to resources.
  • STS (Security Token Service): Obtain temporary security credentials using AWS STS APIs.

3. API Gateway

AWS API Gateway is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs.

  • Usage Plans and API Keys: Control access to APIs using API keys and usage plans. Define quotas and rate limits to manage consumption.
  • Lambda Authorizers: Custom authorizers that use Lambda functions to control access based on custom logic.
  • Resource Policies: Attach resource policies to APIs to control access based on IP addresses, VPCs, or other AWS accounts.

4. VPC Endpoints and PrivateLink

VPC (Virtual Private Cloud) endpoints allow you to privately connect your VPC to supported AWS services and VPC endpoint services.

  • Interface Endpoints: Connect to AWS services using private IP addresses within your VPC.
  • Gateway Endpoints: Use for services like S3 and DynamoDB to route traffic within the AWS network.

5. Service Control Policies (SCPs)

SCPs are used in AWS Organizations to define the maximum permissions for accounts within the organization.

  • Restrict Access: Use SCPs to restrict access to specific services or actions for all accounts within an organizational unit (OU).
  • Mandatory Policies: Ensure compliance by enforcing mandatory policies across multiple accounts.

6. Monitoring and Auditing

Ensure you have mechanisms in place to monitor and audit API usage.

  • AWS CloudTrail: Enable CloudTrail to log API calls made in your AWS account. This provides visibility into who did what and when.
  • AWS Config: Use AWS Config to monitor changes in configurations and compliance with policies.
  • Amazon CloudWatch: Monitor API usage and performance metrics. Set up alarms and notifications for unusual activities.

7. Application-Level Controls

Implement additional controls within your application code.

  • SDKs and Libraries: Use AWS SDKs and libraries to handle API requests securely.
  • Environment Variables: Store and manage sensitive information like API keys and access credentials using environment variables.
  • Secrets Manager and Parameter Store: Use AWS Secrets Manager or AWS Systems Manager Parameter Store to securely manage sensitive information.

Example Scenarios

Scenario 1: Controlling Access Using IAM Roles and Policies


  1. Create an IAM Role: Define a role with specific permissions needed by your application.
  2. Attach Policies: Attach identity-based policies to the role.
  3. Assume Role in Application: Configure your application to assume the role and use the temporary security credentials.

Example Policy:

  • Allow the role to list and read objects from an S3 bucket.

Scenario 2: API Gateway with Lambda Authorizer


  1. Create an API Gateway: Define an API with required methods.
  2. Configure Lambda Authorizer: Implement a Lambda function to authorize requests based on custom logic.
  3. Deploy API: Secure the API with resource policies and usage plans.

Example Use Case:

  • Allow access to the API only for requests coming from specific IP addresses.


Controlling your application’s access to AWS APIs involves a combination of IAM policies, roles, API Gateway features, VPC endpoints, service control policies, monitoring, and application-level controls. By implementing these strategies, you can ensure secure, manageable, and compliant access to AWS resources, protecting your application and data from unauthorized access and misuse.