Post Syndicated from Yee Fei Ooi original https://aws.amazon.com/blogs/security/how-to-automate-the-review-and-validation-of-permissions-for-users-and-groups-in-aws-iam-identity-center/

AWS IAM Identity Center (successor to AWS Single Sign-On) is widely used by organizations to centrally manage federated access to their Amazon Web Services (AWS) environment. As organizations grow, it’s crucial that they maintain control of access to their environment and conduct regular reviews of existing granted permissions to maintain a good security posture. With continuous movement of users among projects and teams within an organization, there are constant updates in groups and permission sets. Given the frequency of updates, it’s important for organizations to maintain the integrity of the identity entities and promote visibility into their associated permissions within IAM Identity Center.

Performing an audit of permissions assignment through the IAM Identity Center Management Console can be an arduous and time-consuming task, especially for customers managing a significant number of AWS accounts. This blog post addresses the following concerns faced by security administrators:

• How to maintain control over permissions and efficiently conduct thorough audits.
• How to regularly review granted permissions to uphold the principle of least privilege.

In this blog post, we show you how to automate your IAM Identity Center users and groups permission review process with AWS SDK and AWS serverless services. The solution also includes how to schedule the review process based on preferred frequency and generating a business-specific access and permission review report.

By using AWS serverless services and AWS SDK, you can create an automated workflow to retrieve the latest permission sets of your identities in IAM Identity Center and extract them as a report. Amazon EventBridge scheduling allows you to set customized schedules to launch the automation process. AWS Lambda functions are used in data retrieval, data transformation, and report generation, and Amazon DynamoDB tables are used for storing raw unstructured data.

We show you how to build an automated solution using AWS SDK, AWS Step Functions, Lambda, DynamoDB, EventBridge, Amazon Simple Storage Service (Amazon S3), and Amazon Simple Notification Service (Amazon SNS) to review the IAM Identity Center instance that you specify. The review includes retrieving attached permission policies (inline, AWS managed, and customer managed) based on the assigned identity.

Note: This solution will incur costs based on the AWS services used.

Prerequisites

In your own AWS environment, make sure that you have the following:

• An IAM Identity Center instance set up in the account
• IAM Identity Center instance metadata that you want to perform the analysis on:
  • The IAM Identity Center instance identityStoreId – example: d-xxxxxxxxxx
  • The IAM Identity Center instance instanceArn – example: arn:aws:sso:::instance/ssoins-xxxxxxxxxx
• Access and permission to deploy the related AWS services mentioned previously in AWS CloudFormation.
  
  

  Note: This solution is expected to deploy in the account where your IAM Identity Center instance is being set up. If you want to deploy in other accounts, you need to establish cross-account access for the IAM roles of the relevant services mentioned previously.

• AWS SAM CLI installed. You will deploy the solution using AWS Serverless Application Model (AWS SAM). To learn more about how AWS SAM works, see the AWS Serverless Application Model (AWS SAM) specification.

Solution overview

In this section, we discuss the steps to set up solution. We provide a CloudFormation template that you can use to set up the required services and Lambda functions. Figure 1 illustrates the architecture of the solution.

The solution is deployed using AWS SAM, which is an open-sourced framework for building serverless applications. AWS SAM helps to organize related components and operate on a single stack. When used together with the SAM CLI, it’s a useful tool for developing, testing, and building serverless applications on AWS.

To generate the report, the solution uses the following steps:

• The EventBridge Scheduler is configured to launch the Step Functions based on the frequency of the cron job stated. The user can also manually launch the review as needed.
• After the Step Functions are launched, the dataExtractionFunction Lambda function retrieves data from IAM Identity Center and stores it in two separate DynamoDB tables, fullPermissionSetsWithGroupTable and userWithGroupTable.
• Step Functions will then launch the dataTransformLoadFunction Lambda function, which retrieves the data from both DynamoDB tables to perform data transformation for report generation.
• The permission review report is stored in an S3 bucket and notification of completion is sent to the stakeholders.

Deploy the solution

1. Make sure that you have AWS SAM CLI installed.
2. Clone the GitHub repository. Open a CLI window and run
   git clone https://github.com/aws-samples/aws-iam-identity-center-permission-policies-analyzer.git
3. Navigate to root directory of the GitHub repository by running cd aws-iam-identity-center-permission-policies-analyzer
4. Run sam deploy ‐‐guided and follow the step-by-step instructions to indicate the deployment details such as the desired CloudFormation stack name, AWS Region and other details as shown in Figure 2.
    
   

   Figure 2: Configure SAM deploy

5. As shown in Figure 2, you receive confirmation that the required resources have been created. AWS SAM creates a default S3 bucket to store the necessary resources and then proceeds to the deployment prompt. Enter y to deploy and wait for deployment to complete.
6. After deployment is complete, you should see the following output: Successfully created/updated stack – {StackName} in {AWSRegion}. You can review the resources and stack in your CloudFormation console as shown in Figure 3.
    
   

   Figure 3: CloudFormation console view of deployed stack

   The CloudFormation template specifies the cron schedule on the first day of each month at 0800 UTC +8 by default. You can update the schedule based on your preference by following steps 7 and 8.

7. Open the EventBridge console. In the navigation pane, under Scheduler, choose Schedules. Check the box next to {StackName}-monthlySchedule-{RandomID} and choose Edit.
    
   

   Figure 4: EventBridge schedule console

8. At Step 1, under the Schedule pattern segment, enter your preferred scheduling. To learn about the different types of EventBridge scheduling, see Schedule types on EventBridge Scheduler. For this example, you use a recurring type of schedule using cron expression. Update to your preferred schedule and time zone and choose Next.
    
   

   Figure 5: EventBridge Schedule edit console Step 1 – Specify schedule detail

9. Check the email address you entered during the deployment stage of this solution for an email sent by [email protected], similar to what you see in Figure 6. Follow the steps in the email to confirm the Amazon SNS topic subscription.
    
   

   Figure 6: Example email from Amazon SNS for subscription confirmation

Manually launch the review

After you’ve updated the schedule, the review process runs on the specified timing and frequency. You can manually launch the review immediately after you’ve deployed the solution, or at a time outside of the schedule on an as-needed basis.

1. To manually launch the review, open the Step Functions console,
2. Select the state machine monthlyUserPermissionAssessment-{randomID} and choose Start execution.
    
   

   Figure 7: Start execution for monthlyUserPermissionAssessment state machine

3. Enter the following event pattern and choose Start execution.

   {
     "identityStoreId": "d-xxxxxxxxxx",
     "instanceArn": "arn:aws:sso:::instance/ssoins-xxxxxxxxxx",
     "ssoDeployedRegion": "YOUR_SSO_DEPLOYED_REGION" 
   }

   Note: The format and keyword format are important to run the Step Functions successfully.

When the process starts, the execution page opens and you can follow the process. The flow turns green when each step has been completed successfully. You can also review Events and check the Lambda functions or logs if you need to troubleshoot or refer to the details.

Notification from each successful review

After each successful execution, you should receive an email notification at the email you specified in the Amazon SNS topic. You can then retrieve the report from the S3 bucket with the bucket name {StackName}-monthlyre-{AccountID}. Your report is stored according to the object key name specified in the email. An example of the email notification is shown in Figure 10.

You can download the report in CSV format from the S3 bucket. The headers of the report are:

User:	Username
PrincipalId:	An identifier for an object in IAM Identity Center, such as a user or group
PrincipalType:	USER or GROUP
GroupName:	Group’s display name value (if PrincipalType is GROUP)
AccountIdAssignment:	Identifier of the AWS account assigned with the specified permission set
PermissionSetARN:	ARN of the permission set
PermissionSetName:	Name of the permission set
Inline Policy:	Inline policy that is attached to the permission set
Customer Managed Policy:	Specifies the names and paths of the customer managed policies that you have attached to your permission set
AWS Managed Policy:	Details of the AWS managed policy
Permission Boundary:	Permission boundary details (Customer Managed Policy Reference and/or AWS managed policy ARN)

From the report, you can determine whether a user is assigned to an account individually or as part of a group, along with the corresponding permission sets. The report also includes details on inline policy, AWS managed policy, customer managed policy, and the permission boundaries attached to the permission set. Inline policies and AWS managed policies are presented in JSON format. However, for customer managed policies and permission boundaries, to keep the solution simple, the generated report provides only basic information on the policies that you’ve attached to the permission set. You can log in to the respective accounts to view the policies in full JSON format through the AWS IAM console.

[Optional] Customize the user notification email

If you want to customize the email notification subject and content, you can do so by editing the Lambda function {StackName}-dataTransformLoadFunction-{RandomID}. Scroll down to the bottom of the source code and edit the sns_message and Subject accordingly.

Clean up the resources

To clean up the resources that you created for this example:

1. Empty your S3 bucket. Open the Amazon S3 console, search for the bucket name and choose Empty. Follow the instructions on screen to empty it.
2. Delete the CloudFormation stack by either:
   1. Using the CloudFormation console to delete the stack, or
   2. Using the AWS SAM CLI to run sam delete in your terminal. Follow the instructions and enter y when prompted to delete the stack.

Conclusion

In this post, you learned how to deploy a solution that simplifies the review and analysis of IAM permissions granted to IAM Identity Center with an automated flow. You also learned about customization that you can set up to fit your team’s needs and preferences.

If you have feedback about this post, submit comments in the Comments section. If you have questions about this post, start a new thread on the AWS Security, Identity, & Compliance re:Post or contact AWS Support.

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