Feb 08, 2024
16 min read

AWS Lambda Secrets Manager Best Practices

AWS Lambda Secrets Manager Best Practices
Learn how to securely manage sensitive data like API keys and database credentials for AWS Lambda using Secrets Manager.

AWS Lambda runs your code in response to events, such as changes in data values and application state or user actions, without requiring you to manage servers.

Lambda functions reduce the burden of managing the application environment; however, they also come with secret management challenges. Secrets, in this context, refer to sensitive data like API keys, database credentials, and encryption keys, which are essential for the secure functioning of software. Managing these secrets is vital in serverless environments for a few key reasons:

  • Security: With serverless, your code is distributed and executed in a highly dynamic environment. Keeping secrets secure in this setting is crucial to prevent data breaches.
  • Scalability: As your application grows, efficiently managing secrets becomes challenging.
  • Compliance: Many applications must adhere to regulatory standards that mandate strict handling of sensitive information.

This article will explore the process of managing secrets in AWS Lambda. It will provide the best practices, examples, and tools to handle sensitive data securely and select the right Lambda secrets manager for your use case.

Summary of AWS Lambda Secrets Manager concepts

The table below summarizes the essential Lambda secrets manager concepts this article will explore in more detail.

Using secrets management in serverless functions

Managing sensitive information such as API keys, database credentials, and inter-service authentication tokens is crucial to securing your application and customer data. Let's explore how to handle these secrets in different serverless scenarios.

Managing API keys for external access

When serverless functions like AWS Lambda interact with external APIs (e.g., third-party services or different parts of your application), they often require API keys for authentication. These keys need to be managed securely to prevent unauthorized access.

  • Storage and retrieval: Instead of embedding API keys directly in the function's code, store them in a secure location like AWS Secrets Manager or AWS Parameter Store. When the function executes, it dynamically retrieves the key, ensuring it isn't exposed in the codebase or logs.
  • Rotation and access control: Regularly rotate these keys and strictly control who and what can access them. This minimizes the risk if a key gets exposed or compromised.

Handling database credentials

Database connections are standard in serverless applications. Securing the database credentials (like username and password) is essential to prevent unauthorized data access.

  • Secure storage: Store database credentials in a secure, centralized secrets management tool. This centralization aids in tracking and auditing access to these credentials.
  • Dynamic retrieval: Configure your serverless function to retrieve these credentials dynamically at runtime. This approach ensures that credentials are not stored in a static configuration file or code, reducing the risk of exposure. It also aids in secret rotation and prevents the need for code and configuration changes within infrastructure and applications, preventing potential downtime or security vulnerabilities.

Inter-service authentication

In a serverless architecture, functions often must communicate with other services within the same application, such as a storage cloud service like S3 or an internal microservice. This requires secure authentication mechanisms to ensure only authorized functions and services can interact.

  • Short-lived credentials: Use short-lived tokens or credentials for inter-service communication. This minimizes the window of opportunity for any unauthorized access.
  • Identity-based access: Leverage identity-based access mechanisms like AWS Identity and Access Management (IAM) roles. Assign these roles to your Lambda functions to control what resources each function can access within your AWS environment.
  • Encryption and secure channels: Ensure all communications between services are encrypted and transmitted over secure channels. This prevents interception and unauthorized access to the data being transmitted.

Additionally, teams should account for these practical considerations:

  • Automated rotation: Automate the rotation of secrets to reduce the risk of using stale or compromised credentials.
  • Auditing and monitoring: Implement logging and monitoring to track when and how secrets are accessed. This helps in identifying unusual patterns that might indicate a breach.
  • Principle of least privilege: Adhere to the principle of least privilege, ensuring that each function or service has access to the secrets necessary for its operation.

By adopting these practices, you can effectively manage secrets in serverless functions, maintaining your applications' security and integrity in a serverless environment.

Six types of Lambda secrets and parameters

Knowing the different kinds of secrets and parameters your functions might use is essential to selecting the right Lambda secrets manager solution. These secrets and parameters are critical for the secure and efficient operation of your serverless applications.

The table below explains the six most important types of Lambda secrets and parameters.

Leveraging AWS Secrets Manager and Parameter Store to manage Lambda secrets

Using AWS Secrets Manager to inject secrets into AWS Lambda functions involves several steps. First, you store your secret in the AWS Secrets Manager. Then, you write Lambda function code to retrieve the secret at runtime. The following is a real-world example in Python, demonstrating how to retrieve a secret from AWS Secrets Manager within a Lambda function:

Step 1: Store Your Secret in AWS Secrets Manager

  1. Log in to the AWS Management Console.
  2. Go to the AWS Secrets Manager service.
  3. Store a new secret (e.g., a database password or an API key).
  4. Note the secret's name or ARN (Amazon Resource Name) after storing it.

Step 2: Set Up IAM Permissions

Ensure your Lambda function's execution role has permission to access the secret. You can attach a policy like the following to the Lambda execution role:

Replace region, account-id, and your-secret-name with your actual AWS region, account ID, and the secret name or ARN.

Step 3: Write Lambda Function Code

Here's a sample Python Lambda function that retrieves a secret from AWS Secrets Manager:

Replace your-secret-name and your-aws-region with your secret's name and AWS region. This function fetches the secret and then uses it (e.g., as a database password).

Important notes

  • The example uses the boto3 AWS SDK for Python. Ensure your Lambda execution environment has boto3 installed.
  • This approach retrieves the secret value each time the Lambda function is invoked. For optimization, consider caching secrets, but be cautious of the security implications.
  • Always handle secrets securely and avoid logging them or exposing them in error messages.

You can find more information about retrieving Lambda secrets using AWS Secrets Manager in this reference guide provided by AWS.

AWS Secrets Manager limitations

AWS Secrets Manager is a powerful tool for managing, retrieving, and rotating secrets needed by applications and services. However, like any technology, it comes with its own set of limitations and considerations that are important to be aware of. Understanding these limitations can help plan and implement an effective Lambda secrets manager strategy.

Cost can increase quickly

While AWS Secrets Manager is a versatile and secure solution for managing secrets, it's essential to consider its cost implications. The service operates on a pay-per-use model, charging based on the number of secrets and the frequency of access requests. This could lead to significant costs, especially for applications with many secrets or those requiring frequent access. Additionally, each secret in Secrets Manager has a size limit of 64 KB, which might necessitate alternative storage solutions or strategies for more extensive data. Also, regarding cost, AWS Secrets Manager lacks built-in auditing without additional fees in the form of AWS Cloudtrail. This extra service adds another layer of complexity to a simple solution.

Secret rotation is challenging

Another aspect to consider is the complexity involved in setting up secret rotations. AWS Secrets Manager supports automatic rotation for a limited number of services. If you want to configure automatic secret rotation for the other AWS services or non-AWS resources, it requires implementing a custom AWS Lambda function. This setup can be intricate and needs ongoing maintenance. Furthermore, AWS Secrets Manager may only be available in some AWS regions, which could be a limitation for organizations needing to store secrets in specific geographical locations due to compliance or latency issues.

Integration with third parties is lacking

Integration with third-party applications and services can also present challenges, as not all have built-in support for AWS Secrets Manager. This might require additional development efforts for integration. Moreover, the service provides limited historical data for each secret, primarily covering the secret’s value and metadata changes. This limitation could be significant for organizations that need detailed audit trails for compliance.

High configuration complexity

The complexity of configuring IAM policies for securing access to secrets is another vital consideration. Incorrect configuration can lead to excessive or insufficient access and security risks or operational issues. Additionally, being an AWS-specific service, Secrets Manager might pose a challenge if an organization migrates to a different cloud provider or an on-premises environment, necessitating a change in the secrets management solution. Lastly, as a cloud-based service, AWS Secrets Manager can only be as reliable as its underlying infrastructure. If an AWS region goes down, so does your secret access, jeopardizing your applications’ uptime.

While AWS Secrets Manager offers robust features for secret management, it's crucial to consider these limitations in terms of cost, size limitations, rotation complexity, regional availability, third-party integration, historical data, IAM policy management, dependency on the AWS environment, and the need for internet access. These factors play a significant role in determining the suitability of AWS Secrets Manager for specific applications and organizational requirements.

How Doppler secrets management integrates seamlessly with AWS native tools

Doppler represents a significant advancement in secrets management, particularly for serverless applications like AWS Lambda. It's a centralized secrets management platform that simplifies how developers handle sensitive information across their applications.

What sets Doppler apart is its ability to seamlessly integrate with AWS native tools, providing an efficient bridge between the flexibility of serverless functions and the need for secure, manageable secrets. This integration allows developers to automate the syncing of secrets between Doppler and AWS services, ensuring the latest credentials and configurations are constantly used. The platform also offers enhanced security features, including robust encryption and access controls, which are critical for safeguarding sensitive information in cloud-based applications.

Doppler's integration with AWS is streamlined and user-friendly. It allows developers to sync secrets directly to AWS Secrets Manager and AWS Parameter Store, making them readily accessible to Lambda functions and other AWS services. This integration simplifies the workflow for deploying and updating secrets, reducing the manual effort involved in secret management. With Doppler, changes made to secrets are automatically and securely pushed to AWS services, ensuring that serverless functions always access the most current and secure information. This automated syncing eliminates the risk of outdated or inconsistent secrets across different application parts, a common challenge in cloud environments.

Developers can automatically synchronize secrets with their applications in real time using the Doppler CLI. Any update to a secret in Doppler is instantly propagated to the application without requiring a manual update or redeployment. This dynamic injection is particularly beneficial in serverless architectures where functions may be ephemeral and must access the most current secrets upon each invocation.

Doppler enhances security by providing a single, centralized platform for managing all secrets. This centralization reduces the complexity and potential for error in handling secrets across multiple tools or manual processes. Doppler’s interface is intuitive, enabling easy management of secrets, including creating, updating, and revoking access as needed. It also offers detailed access logs and auditing capabilities, vital for compliance and tracking suspicious activities. Doppler’s security features also extend to encryption in transit and at rest, ensuring that secrets are always protected. By integrating Doppler with AWS, developers can achieve higher security and efficiency in managing secrets, making it a valuable tool for any serverless application running on AWS.

Avoiding common Lambda secrets manager mistakes

In using AWS Lambda and AWS Secrets Manager, certain best practices are essential to ensure security and operational efficiency, helping avoid common pitfalls.

Never hardcode secrets

One of the most critical practices is to avoid hardcoding secrets in the Lambda function's code or configuration files. Hardcoding exposes sensitive information to security risks and complicates the process of secret rotation. Instead, the recommended approach is to securely store secrets in AWS Secrets Manager and retrieve them dynamically in Lambda functions. This enhances security and simplifies updates, as changes in Secrets Manager are automatically reflected in the Lambda functions. Alongside this, implementing the principle of least privilege is crucial. Lambda functions should be assigned only the necessary permissions to perform their tasks, specifically, the permissions needed to access secrets from Secrets Manager. Regularly reviewing and adjusting these permissions as per the changing requirements ensures minimal exposure to security vulnerabilities.

Regularly rotate secrets

Another key practice is the regular rotation of secrets. Frequently changing secrets reduces the risk of exposure and limits the impact of any compromised secret. Utilizing AWS Secrets Manager's automatic rotation feature and configuring Lambda functions to adapt to secret changes ensures that your secrets are regularly refreshed, thereby enhancing security. Alongside this, monitoring access to secrets is vital. This involves enabling logging and monitoring for AWS Secrets Manager and Lambda functions using tools like AWS CloudTrail and Amazon CloudWatch. Monitoring helps quickly identify and respond to unusual activities or potential security incidents.

Encrypt and test secrets in all environments

Finally, encryption and testing in controlled environments must be considered. Ensuring that secrets in AWS Secrets Manager are encrypted using AWS Key Management Service (KMS) adds a layer of security. Lambda functions should be configured to handle encrypted data appropriately. Additionally, implementing a staged approach to changes is crucial. Testing updates to Lambda functions and secrets in a controlled environment, such as a development or staging environment, before deploying to production helps identify potential issues early on. This approach reduces the risk of disruptions in the production environment, ensuring a smoother and more secure operational flow.

By adhering to these best practices, organizations can significantly mitigate the risks of managing secrets and running serverless functions, leading to a more secure and robust AWS cloud environment.


Effectively managing AWS Lambda secrets is crucial for the security and efficiency of serverless applications. This involves understanding and categorizing different types of secrets, such as API keys, database credentials, encryption keys, and OAuth credentials, along with environment-specific configurations. While AWS Secrets Manager and Parameter Store provide robust solutions for storing and retrieving these secrets, they come with challenges like cost, throttling, rotation complexity, and limited multi-region support.

Alternatives like the Doppler solution offer centralized management with seamless AWS integration, enhancing security and simplification. To avoid common pitfalls, it's essential to adhere to best practices like avoiding hardcoded secrets, applying the principle of least privilege, regularly rotating secrets, monitoring access, using encryption, and thoroughly testing changes. By embracing these strategies, developers can ensure the secure and effective management of sensitive data in their serverless environments.