The requirement is to update the infrastructure to ensure that only the Lambda function's execution role can access the values in Secrets Manager. The solution must apply the principle of least privilege, which means granting the minimum permissions necessary to perform a task.
To do this, the DevOps engineer needs to use the following steps:
Create a KMS customer managed key that trusts Secrets Manager and allows the Lambda function's execution role to decrypt. A customer managed key is a symmetric encryption key that is fully managed by the customer. The customer can define the key policy, which specifies who can use and manage the key. By creating a customer managed key, the DevOps engineer can restrict the decryption permission to only the Lambda function's execution role, and prevent other principals from accessing the secret values. The customer managed key also needs to trust Secrets Manager, which means allowing Secrets Manager to use the key to encrypt and decrypt secrets on behalf of the customer.
Update Secrets Manager to use the new customer managed key. Secrets Manager allows customers to choose which KMS key to use for encrypting each secret. By default, Secrets Manager uses the default KMS key for Secrets Manager, which is a service-managed key that is shared by all customers in the same AWS Region.
By updating Secrets Manager to use the new customer managed key, the DevOps engineer can ensure that only the Lambda function's execution role can decrypt the secret values using that key.
Ensure that the Lambda function's execution role has the KMS permissions scoped on the resource level. The Lambda function's execution role is an IAM role that grants permissions to the Lambda function to access AWS services and resources. The role needs to have KMS permissions to use the customer managed key for decryption. However, to apply the principle of least privilege, the role should have the permissions scoped on the resource level, which means specifying the ARN of the customer managed key as a condition in the IAM policy statement. This way, the role can only use that specific key and not any other KMS keys in the account.

Configure AWS Systems Manager on Each Instance:
AWS Systems Manager provides a unified interface for managing AWS resources. Install the Systems Manager agent on each EC2 instance to enable inventory management and other features.
Use AWS Systems Manager Inventory:
Systems Manager Inventory collects metadata about your instances and the software installed on them. This data includes information about applications, network configurations, and more.
Enable Systems Manager Inventory on all EC2 instances to gather detailed information about installed applications.
Use Systems Manager Resource Data Sync to Synchronize and Store Findings in an Amazon S3 Bucket:
Resource Data Sync aggregates inventory data from multiple accounts and regions into a single S3 bucket, making it easier to query and analyze the data.
Configure Resource Data Sync to automatically transfer inventory data to an S3 bucket for centralized storage.
Create an AWS Lambda Function that Runs When New Objects are Added to the S3 Bucket:
Use an S3 event to trigger a Lambda function whenever new inventory data is added to the S3 bucket.
The Lambda function can parse the inventory data and check for the presence of prohibited applications.
Configure the Lambda Function to Identify Prohibited Applications:
The Lambda function should be programmed to scan the inventory data for any known prohibited applications and generate alerts or take appropriate actions if such applications are found.
Example Lambda function in Python
import json
import boto3
def lambda_handler(event, context):
s3 = boto3.client('s3')
bucket = event['Records'][0]['s3']['bucket']['name']
key = event['Records'][0]['s3']['object']['key']
response = s3.get_object(Bucket=bucket, Key=key)
inventory_data = json.loads(response['Body'].read().decode('utf-8'))
prohibited_apps = ['app1', 'app2']
for instance in inventory_data['Instances']:
for app in instance['Applications']:
if app['Name'] in prohibited_apps:
# Send notification or take action
print(f"Prohibited application found: {app['Name']} on instance {instance['InstanceId']}") return {'statusCode': 200, 'body': json.dumps('Check completed')} By leveraging AWS Systems Manager Inventory, Resource Data Sync, and Lambda, this solution provides an efficient and automated way to audit EC2 instances for prohibited applications.
References:
AWS Systems Manager Inventory
AWS Systems Manager Resource Data Sync
S3 Event Notifications
AWS Lambda

https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/SubscriptionFilters.html

AWS Secrets Manager is a secrets management service that helps you protect access to your applications, services, and IT resources. This service enables you to easily rotate, manage, and retrieve database credentials, API keys, and other secrets throughout their lifecycle. Using Secrets Manager, you can secure and manage secrets used to access resources in the AWS Cloud, on third-party services, and on-premises. SSM parameter store and AWS Secret manager are both a secure option. However, Secrets manager is more flexible and has more options like password generation. Reference: https://www.1strategy.com/blog/2019/02
/28/aws-parameter-store-vs-aws-secrets-manager/

https://docs.aws.amazon.com/singlesignon/latest/userguide/configure-abac.html