Using AWS KMS with AWS SSM Parameter Store

Introduction

Welcome to a simplified guide on leveraging AWS Key Management Service (KMS) with the Systems Manager (SSM) Parameter Store. Let's dive into an easy-to-follow explanation that demystifies the concepts and technicalities involved.

What Are We Talking About?

Before we get into the nitty-gritty, let's clarify what AWS KMS and SSM Parameter Store are:

• AWS Key Management Service (KMS): A managed service that makes it easy for us to create and manage cryptographic keys used to encrypt data. KMS is about securing our data by ensuring only authorized users and applications can access it.

• SSM Parameter Store: A component of AWS Systems Manager that provides secure, hierarchical storage for configuration data and secrets like passwords, database strings, and license codes. It's your go-to for keeping sensitive information safe and sound.

The Connection: Secure Strings in SSM Parameter Store

When storing sensitive data in SSM Parameter Store, we will likely use what's called a "Secure String" parameter. These parameters are encrypted, and that's where KMS comes into play. KMS handles the encryption and decryption of these Secure String values, ensuring they're kept under wraps unless we have the necessary permissions to access them.

Two Types of Secure String Parameters

1. Standard Secure Strings: Here, all parameters are encrypted using the same AWS KMS key. This is a straightforward approach and is suitable for many use cases where a single layer of encryption suffices.

2. Advanced Secure Strings: For an extra layer of security, each parameter is encrypted with a unique data key, a method known as Envelope Encryption. This is particularly useful for highly sensitive data that requires stringent security measures.

Choosing Your KMS Key

When we create a Secure String parameter in SSM Parameter Store, we have two options regarding the encryption key:

• Use the AWS Managed Key (aws/ssm): If yoweu prefer not to manage our own keys, we can use the default key provided by AWS. It's a simpler option but offers less flexibility in terms of key management.

• Specify a KMS Key: We can select a specific KMS key that we've created in AWS KMS. This is a great way to maintain control over who has access to the key and, by extension, the data.

Important Notes

• Symmetric KMS Keys Only: It's crucial to note that SSM Parameter Store works exclusively with symmetric KMS keys. These keys are used for both encryption and decryption processes, unlike asymmetric keys that use a pair of related keys (public and private).

• Encryption Process: The actual encryption and decryption of your Secure String parameters occur within AWS KMS. This means that our data is encrypted before it's stored in the Parameter Store and decrypted when we access it, all seamlessly handled by KMS.

• Access Permissions: To access an encrypted parameter, we need permission for both the parameter itself in SSM Parameter Store and the KMS key used for encryption. This dual-layer of permission ensures that only authorized users can access sensitive data.

Conclusion

Understanding how AWS KMS and SSM Parameter Store work together to secure our data is fundamental, especially for those preparing for AWS exams or managing sensitive application configurations. By grasping the basics of Secure String parameters, encryption types, and the importance of managing access permissions, we're well on our way to mastering the use of these powerful AWS services. Remember, the choice between standard and advanced encryption types, as well as which KMS key to use, depends on your specific security requirements and management preferences.