Securely Managing Secrets in Serverless Applications with AWS Secrets Manager

Serverless applications have gained significant popularity in modern application development due to their cost efficiency, scalability, and ease of management. However, managing sensitive data such as API keys, database credentials, and other secrets in a serverless environment requires careful attention. Embedding secrets directly in your application code is a significant security risk and can lead to unintended consequences.

This is where AWS Secrets Manager steps in—a powerful service that securely stores, retrieves, and rotates secrets, ensuring your serverless application remains secure without compromising performance.

In this blog, we’ll explore how to securely manage secrets in serverless applications using AWS Secrets Manager, along with best practices and a step-by-step walkthrough for integrating it with AWS Lambda.

The Importance of Secure Secret Management

Secrets such as database credentials, API tokens, and encryption keys are the backbone of secure application operations. Mismanagement of secrets can expose your application to:

1. Unauthorized access to resources.
2. Compliance violations.
3. Data breaches or leaks.

AWS Secrets Manager addresses these challenges by providing a centralized way to store, access, and rotate secrets securely.

An Overview of AWS Secrets Manager

AWS Secrets Manager is a managed service that helps you:

1. Securely Store Secrets: Encrypted at rest and in transit using AWS Key Management Service (KMS).
2. Retrieve Secrets Programmatically: Using APIs or SDKs within your applications.
3. Automatically Rotate Secrets: For AWS services like RDS or other databases integrated with Secrets Manager.
4. Audit Access: Integrated with AWS CloudTrail for monitoring and tracking.

Use Cases of AWS Secrets Manager in Serverless Applications

In a typical serverless architecture, secrets are often needed for:

1. Accessing Databases: Storing database credentials securely for applications using AWS Lambda functions.
2. Third-party API Authentication: Safeguarding API keys for external service integrations.
3. Encryption Keys: Securing sensitive data using encryption and managing access to the keys.

AWS Secrets Manager helps serverless applications access these secrets efficiently while adhering to best security practices.

Step-by-Step Guide to Using AWS Secrets Manager with AWS Lambda

Let’s walk through the process of securely storing and retrieving secrets in a serverless application using AWS Lambda.

Storing a Secret in AWS Secrets Manager

1. Go to the AWS Management Console and navigate to Secrets Manager.
2. Click Store a new secret.
3. Choose the type of secret you want to store:
• Credentials for RDS databases.
• API keys for third-party services.
• Custom secret key-value pairs.
4. Enter the secret information and select the Encryption Key (Default or a custom KMS key).
5. Provide a Secret Name (e.g., myApp/DBCredentials) and optional tags.
6. Configure automatic rotation (optional but recommended for databases).
7. Save the secret.

Adding IAM Permissions for Lambda to Access Secrets

Your Lambda function requires permission to retrieve secrets from Secrets Manager. Update the IAM role associated with your Lambda function to include the following policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "secretsmanager:GetSecretValue"
      ],
      "Resource": "arn:aws:secretsmanager:region:account-id:secret:myApp/DBCredentials-*"
    }
  ]
}

This grants your Lambda function read access to the specified secret.

Fetching Secrets Programmatically in a Lambda Function

In your Node.js Lambda function, use the AWS SDK to fetch the secret.
Here’s an example:

import { GetSecretValueCommand, SecretsManagerClient, } from "@aws-sdk/client-secrets-manager";

const secretsManagerClient = new SecretsManagerClient();

export const handler = async (event: any) => {
  try {
    // Fetch the secret value
    const secretValue = await secretsManagerClient.send(
      new GetSecretValueCommand({
        SecretId: 'myApp/DBCredentials',
      }),
    );
    if ('SecretString' in secretValue) {
      const SecretString = secretValue.SecretString;
      console.log('Retrieved secret:', SecretString);

      // Use the secret (e.g., connect to a database)
      return { statusCode: 200, body: 'Secret retrieved successfully in String format' };
    } else if ('SecretBinary' in secretValue) {
      const SecretBinary = secretValue.SecretBinary;
      console.log('Retrieved secret:', SecretBinary);
      
      // Use the secret (e.g., connect to a database)
      return { statusCode: 500, body: 'Secret retrieved successfully in Binary format' };
    }
    else {
      return { statusCode: 500, body: 'Failed to retrieve secret' };
    }
  } catch (error) {
    console.error('Error retrieving secret:', error);
    return { statusCode: 500, body: 'Error retrieving secret' };
  }
};

Testing the Lambda Function

1. Deploy the Lambda function to your AWS account.
2. Trigger the function manually or integrate it into an event source such as API Gateway or an S3 bucket.
3. Verify the secret retrieval in your logs via AWS CloudWatch.

Rotating Secrets for Improved Security

If your secret is tied to an RDS database, configure automatic rotation in Secrets Manager:

1. Enable rotation for your secret.
2. Use the built-in Lambda rotation function or create a custom rotation Lambda.
3. Test the rotation to ensure the updated credentials work seamlessly.

Best Practices for Secrets Management

1. Avoid Hardcoding Secrets: Never store sensitive information directly in application code or environment variables.
2. Use Least Privilege Access: Only grant necessary permissions to your Lambda function for accessing specific secrets.
3. Enable Automatic Rotation: Regularly rotate secrets to minimize the risk of compromised credentials.
4. Audit Secret Access: Use AWS CloudTrail to monitor and log access to your secrets.
5. Encrypt Secrets with KMS: Use custom KMS keys for additional security.
6. Integrate with CI/CD: Use automated pipelines to manage secrets securely across environments.

Benefits of AWS Secrets Manager in Serverless Applications

1. Enhanced Security: Secrets are encrypted and stored securely, reducing the risk of leaks.
2. Centralized Management: Manage all application secrets in one place.
3. Automatic Rotation: Save time by automating credential updates.
4. Integration with AWS Services: Easily integrate with Lambda, RDS, ECS, and more.
5. Scalability: Designed for high availability and low latency.

Example: Real-World Use Case

Scenario: A serverless application using AWS Lambda needs secure database credentials for an RDS instance.

Solution:

1. Store the credentials in Secrets Manager.
2. Grant the Lambda function permissions to retrieve the secret.
3. Enable automatic rotation for the secret, ensuring the application always has up-to-date credentials.

This approach eliminates the need for hardcoding secrets and ensures secure access control.

Conclusion

AWS Secrets Manager simplifies the complexities of managing sensitive data in serverless applications, allowing developers to focus on building features without compromising security. By integrating Secrets Manager with AWS Lambda, you can ensure your applications are secure, scalable, and maintainable.

Ready to secure your serverless applications? Start using AWS Secrets Manager today and take your cloud security practices to the next level!