All posts by Mathangi Ramesh

IAM Access Analyzer makes it simpler to author and validate role trust policies

Post Syndicated from Mathangi Ramesh original https://aws.amazon.com/blogs/security/iam-access-analyzer-makes-it-simpler-to-author-and-validate-role-trust-policies/

AWS Identity and Access Management (IAM) Access Analyzer provides many tools to help you set, verify, and refine permissions. One part of IAM Access Analyzer—policy validation—helps you author secure and functional policies that grant the intended permissions. Now, I’m excited to announce that AWS has updated the IAM console experience for role trust policies to make it simpler for you to author and validate the policy that controls who can assume a role. In this post, I’ll describe the new capabilities and show you how to use them as you author a role trust policy in the IAM console.

Overview of changes

A role trust policy is a JSON policy document in which you define the principals that you trust to assume the role. The principals that you can specify in the trust policy include users, roles, accounts, and services. The new IAM console experience provides the following features to help you set the right permissions in the trust policy:

  • An interactive policy editor prompts you to add the right policy elements, such as the principal and the allowed actions, and offers context-specific documentation.
  • As you author the policy, IAM Access Analyzer runs over 100 checks against your policy and highlights issues to fix. This includes new policy checks specific to role trust policies, such as a check to make sure that you’ve formatted your identity provider correctly. These new checks are also available through the IAM Access Analyzer policy validation API.
  • Before saving the policy, you can preview findings for the external access granted by your trust policy. This helps you review external access, such as access granted to a federated identity provider, and confirm that you grant only the intended access when you create the policy. This functionality was previously available through the APIs, but now it’s also available in the IAM console.

In the following sections, I’ll walk you through how to use these new features.

Example scenario

For the walkthrough, consider the following example, which is illustrated in Figure 1. You are a developer for Example Corp., and you are working on a web application. You want to grant the application hosted in one account—the ApplicationHost account—access to data in another account—the BusinessData account. To do this, you can use an IAM role in the BusinessData account to grant temporary access to the application through a role trust policy. You will grant a role in the ApplicationHost account—the PaymentApplication role—to access the BusinessData account through a role—the ApplicationAccess role. In this example, you create the ApplicationAccess role and grant cross-account permissions through the trust policy by using the new IAM console experience that helps you set the right permissions.

Figure 1: Visual explanation of the scenario

Figure 1: Visual explanation of the scenario

Create the role and grant permissions through a role trust policy with the policy editor

In this section, I will show you how to create a role trust policy for the ApplicationAccess role to grant the application access to the data in your account through the policy editor in the IAM console.

To create a role and grant access

  1. In the BusinessData account, open the IAM console, and in the left navigation pane, choose Roles.
  2. Choose Create role, and then select Custom trust policy, as shown in Figure 2.
    Figure 2: Select "Custom trust policy" when creating a role

    Figure 2: Select “Custom trust policy” when creating a role

  3. In the Custom trust policy section, for 1. Add actions for STS, select the actions that you need for your policy. For example, to add the action sts:AssumeRole, choose AssumeRole.
    Figure 3: JSON role trust policy

    Figure 3: JSON role trust policy

  4. For 2. Add a principal, choose Add to add a principal.
  5. In the Add principal box, for Principal type, select IAM roles. This populates the ARN field with the format of the role ARN that you need to add to the policy, as shown in Figure 4.
    Figure 4: Add a principal to your role trust policy

    Figure 4: Add a principal to your role trust policy

  6. Update the role ARN template with the actual account and role information, and then choose Add principal. In our example, the account is ApplicationHost with an AWS account number of 111122223333, and the role is PaymentApplication role. Therefore, the role ARN is arn:aws:iam:: 111122223333: role/PaymentApplication. Figure 5 shows the role trust policy with the action and principal added.
    Figure 5: Sample role trust policy

    Figure 5: Sample role trust policy

  7. (Optional) To add a condition, for 3. Add a condition, choose Add, and then complete the Add condition box according to your needs.

Author secure policies by reviewing policy validation findings

As you author the policy, you can see errors or warnings related to your policy in the policy validation window, which is located below the policy editor in the console. With this launch, policy validation in IAM Access Analyzer includes 13 new checks focused on the trust relationship for the role. The following are a few examples of these checks and how to address them:

  • Role trust policy unsupported wildcard in principal – you can’t use a * in your role trust policy.
  • Invalid federated principal syntax in role trust policy – you need to fix the format of the identity provider.
  • Missing action for condition key – you need to add the right action for a given condition, such as the sts:TagSession when there are session tag conditions.

For a complete list of checks, see Access Analyzer policy check reference.

To review and fix policy validation findings

  1. In the policy validation window, do the following:
    • Choose the Security tab to check if your policy is overly permissive.
    • Choose the Errors tab to review any errors associated with the policy.
    • Choose the Warnings tab to review if aspects of the policy don’t align with AWS best practices.
    • Choose the Suggestions tab to get recommendations on how to improve the quality of your policy.
    Figure 6: Policy validation window in IAM Access Analyzer with a finding for your policy

    Figure 6: Policy validation window in IAM Access Analyzer with a finding for your policy

  2. For each finding, choose Learn more to review the documentation associated with the finding and take steps to fix it. For example, Figure 6 shows the error Mismatched Action For Principal. To fix the error, remove the action sts:AssumeRoleWithWebIdentity.

Preview external access by reviewing cross-account access findings

IAM Access Analyzer also generates findings to help you assess if a policy grants access to external entities. You can review the findings before you create the policy to make sure that the policy grants only intended access. To preview the findings, you create an analyzer and then review the findings.

To preview findings for external access

  1. Below the policy editor, in the Preview external access section, choose Go to Access Analyzer, as shown in Figure 7.

    Note: IAM Access Analyzer is a regional service, and you can create a new analyzer in each AWS Region where you operate. In this situation, IAM Access Analyzer looks for an analyzer in the Region where you landed on the IAM console. If IAM Access Analyzer doesn’t find an analyzer there, it asks you to create an analyzer.

    Figure 7: Preview external access widget without an analyzer

    Figure 7: Preview external access widget without an analyzer

  2. On the Create analyzer page, do the following to create an analyzer:
    • For Name, enter a name for your analyzer.
    • For Zone of trust, select the correct account.
    • Choose Create analyzer.
    Figure 8: Create an analyzer to preview findings

    Figure 8: Create an analyzer to preview findings

  3. After you create the analyzer, navigate back to the role trust policy for your role to review the external access granted by this policy. The following figure shows that external access is granted to PaymentApplication.
    Figure 9: Preview finding

    Figure 9: Preview finding

  4. If the access is intended, you don’t need to take any action. In this example, I want the PaymentApplication role in the ApplicationHost account to assume the role that I’m creating.
  5. If the access is unintended, resolve the finding by updating the role ARN information.
  6. Select Next and grant the required IAM permissions for the role.
  7. Name the role ApplicationAccess, and then choose Save to save the role.

Now the application can use this role to access the BusinessData account.

Conclusion

By using the new IAM console experience for role trust policies, you can confidently author policies that grant the intended access. IAM Access Analyzer helps you in your least-privilege journey by evaluating the policy for potential issues to make it simpler for you to author secure policies. IAM Access Analyzer also helps you preview external access granted through the trust policy to help ensure that the granted access is intended. To learn more about how to preview IAM Access Analyzer cross-account findings, see Preview access in the documentation. To learn more about IAM Access Analyzer policy validation checks, see Access Analyzer policy validation. These features are also available through APIs.

If you have feedback about this post, submit comments in the Comments section below. If you have questions about this post, start a new thread at AWS IAM re:Post or contact AWS Support.

Mathangi Ramesh

Mathangi Ramesh

Mathangi is the product manager for AWS Identity and Access Management. She enjoys talking to customers and working with data to solve problems. Outside of work, Mathangi is a fitness enthusiast and a Bharatanatyam dancer. She holds an MBA degree from Carnegie Mellon University.

Use IAM Access Analyzer to generate IAM policies based on access activity found in your organization trail

Post Syndicated from Mathangi Ramesh original https://aws.amazon.com/blogs/security/use-iam-access-analyzer-to-generate-iam-policies-based-on-access-activity-found-in-your-organization-trail/

In April 2021, AWS Identity and Access Management (IAM) Access Analyzer added policy generation to help you create fine-grained policies based on AWS CloudTrail activity stored within your account. Now, we’re extending policy generation to enable you to generate policies based on access activity stored in a designated account. For example, you can use AWS Organizations to define a uniform event logging strategy for your organization and store all CloudTrail logs in your management account to streamline governance activities. You can use Access Analyzer to review access activity stored in your designated account and generate a fine-grained IAM policy in your member accounts. This helps you to create policies that provide only the required permissions for your workloads.

Customers that use a multi-account strategy consolidate all access activity information in a designated account to simplify monitoring activities. By using AWS Organizations, you can create a trail that will log events for all Amazon Web Services (AWS) accounts into a single management account to help streamline governance activities. This is sometimes referred to as an organization trail. You can learn more from Creating a trail for an organization. With this launch, you can use Access Analyzer to generate fine-grained policies in your member account and grant just the required permissions to your IAM roles and users based on access activity stored in your organization trail.

When you request a policy, Access Analyzer analyzes your activity in CloudTrail logs and generates a policy based on that activity. The generated policy grants only the required permissions for your workloads and makes it easier for you to implement least privilege permissions. In this blog post, I’ll explain how to set up the permissions for Access Analyzer to access your organization trail and analyze activity to generate a policy. To generate a policy in your member account, you need to grant Access Analyzer limited cross-account access to access the Amazon Simple Storage Service (Amazon S3) bucket where logs are stored and review access activity.

Generate a policy for a role based on its access activity in the organization trail

In this example, you will set fine-grained permissions for a role used in a development account. The example assumes that your company uses Organizations and maintains an organization trail that logs all events for all AWS accounts in the organization. The logs are stored in an S3 bucket in the management account. You can use Access Analyzer to generate a policy based on the actions required by the role. To use Access Analyzer, you must first update the permissions on the S3 bucket where the CloudTrail logs are stored, to grant access to Access Analyzer.

To grant permissions for Access Analyzer to access and review centrally stored logs and generate policies

  1. Sign in to the AWS Management Console using your management account and go to S3 settings.
  2. Select the bucket where the logs from the organization trail are stored.
  3. Change object ownership to bucket owner preferred. To generate a policy, all of the objects in the bucket must be owned by the bucket owner.
  4. Update the bucket policy to grant cross-account access to Access Analyzer by adding the following statement to the bucket policy. This grants Access Analyzer limited access to the CloudTrail data. Replace the <organization-bucket-name>, and <organization-id> with your values and then save the policy. 
    {
    "Version": "2012-10-17",
    "Statement": 
    [
    {
        "Sid": "PolicyGenerationPermissions",
        "Effect": "Allow",
        "Principal": {
            "AWS": "*"
        },
        "Action": [
            "s3:GetObject",
            "s3:ListBucket"
        ],
        "Resource": [
            "arn:aws:s3:::<organization-bucket-name>",
            "arn:aws:s3:::my-organization-bucket/AWSLogs/o-exampleorgid/${aws:PrincipalAccount}/*
"
        ],
        "Condition": {
"StringEquals":{
"aws:PrincipalOrgID":"<organization-id>"
},

            "StringLike": {"aws:PrincipalArn":"arn:aws:iam::${aws:PrincipalAccount}:role/service-role/AccessAnalyzerMonitorServiceRole*"            }
        }
    }
    ]
}

By using the preceding statement, you’re allowing listbucket and getobject for the bucket my-organization-bucket-name if the role accessing it belongs to an account in your Organizations and has a name that starts with AccessAnalyzerMonitorServiceRole. Using aws:PrincipalAccount in the resource section of the statement allows the role to retrieve only the CloudTrail logs belonging to its own account. If you are encrypting your logs, update your AWS Key Management Service (AWS KMS) key policy to grant Access Analyzer access to use your key.

Now that you’ve set the required permissions, you can use the development account and the following steps to generate a policy.

To generate a policy in the AWS Management Console

  1. Use your development account to open the IAM Console, and then in the navigation pane choose Roles.
  2. Select a role to analyze. This example uses AWS_Test_Role.
  3. Under Generate policy based on CloudTrail events, choose Generate policy, as shown in Figure 1.
     
    Figure 1: Generate policy from the role detail page

    Figure 1: Generate policy from the role detail page

  4. In the Generate policy page, select the time window for which IAM Access Analyzer will review the CloudTrail logs to create the policy. In this example, specific dates are chosen, as shown in Figure 2.
     
    Figure 2: Specify the time period

    Figure 2: Specify the time period

  5. Under CloudTrail access, select the organization trail you want to use as shown in Figure 3.

    Note: If you’re using this feature for the first time: select create a new service role, and then choose Generate policy.

    This example uses an existing service role “AccessAnalyzerMonitorServiceRole_MBYF6V8AIK.”
     

    Figure 3: CloudTrail access

    Figure 3: CloudTrail access

  6. After the policy is ready, you’ll see a notification on the role page. To review the permissions, choose View generated policy, as shown in Figure 4.
     
    Figure 4: Policy generation progress

    Figure 4: Policy generation progress

After the policy is generated, you can see a summary of the services and associated actions in the generated policy. You can customize it by reviewing the services used and selecting additional required actions from the drop down. To refine permissions further, you can replace the resource-level placeholders in the policies to restrict permissions to just the required access. You can learn more about granting fine-grained permissions and creating the policy as described in this blog post.

Conclusion

Access Analyzer makes it easier to grant fine-grained permissions to your IAM roles and users by generating IAM policies based on the CloudTrail activity centrally stored in a designated account such as your AWS Organizations management accounts. To learn more about how to generate a policy, see Generate policies based on access activity in the IAM User Guide.

If you have feedback about this blog post, submit comments in the Comments section below. If you have questions about this blog post, start a new thread on the IAM forum or contact AWS Support.

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Mathangi Ramesh

Mathangi Ramesh

Mathangi is the product manager for AWS Identity and Access Management. She enjoys talking to customers and working with data to solve problems. Outside of work, Mathangi is a fitness enthusiast and a Bharatanatyam dancer. She holds an MBA degree from Carnegie Mellon University.