IAM tutorial: Use SAML session tags for ABAC

Attribute-based access control (ABAC) is an authorization strategy that defines permissions based on attributes. In AWS, these attributes are called tags. You can attach tags to IAM resources, including IAM entities (users or roles), and to AWS resources. When the entities are used to make requests to AWS, they become principals and those principals include tags.

You can also pass session tags when you assume a role or federate a user. You can then define policies that use tag condition keys to grant permissions to your principals based on their tags. When you use tags to control access to your AWS resources, you allow your teams and resources to grow with fewer changes to AWS policies. ABAC policies are more flexible than traditional AWS policies, which require you to list each individual resource. For more information about ABAC and its advantage over traditional policies, see Define permissions based on attributes with ABAC authorization.

If your company uses a SAML-based identity provider (IdP) to manage corporate user identities, you can use SAML attributes for fine-grained access control in AWS. Attributes can include cost center identifiers, user email addresses, department classifications, and project assignments. When you pass these attributes as session tags, you can then control access to AWS based on these session tags.

To complete the ABAC tutorial by passing SAML attributes to your session principal, complete the tasks in IAM tutorial: Define permissions to access AWS resources based on tags, with the changes that are included in this topic.

Prerequisites

To perform the steps to use SAML session tags for ABAC, you must already have the following:

Step 1: Create test users

Skip the instructions in Step 1: Create test users. Because your identities are defined in your provider, it's not necessary for you to add IAM users for your employees.

Step 2: Create the ABAC policy

Follow the instructions in Step 2: Create the ABAC policy to create the specified managed policy in IAM.

Step 3: Create and configure the SAML role

When you use the ABAC tutorial for SAML, you must perform additional steps to create the role, configure the SAML IdP, and enable AWS Management Console access. For more information, see Step 3: Create roles.

Step 3A: Create the SAML role

Create a single role that trusts your SAML identity provider and the test-session-tags user that you created in step 1. The ABAC tutorial uses separate roles with different role tags. Because you are passing session tags from your SAML IdP, you need only one role. To learn how to create a SAML-based role, see Create a role for SAML 2.0 federation (console).

Name the role access-session-tags. Attach the access-same-project-team permissions policy to the role. Edit the role trust policy to use the following policy. For detailed instructions on how to edit the trust relationship of a role, see Update a role trust policy .

The following role trust policy allows your SAML identity provider and the test-session-tags user to assume the role. When they assume the role, they must pass the three specified session tags. The sts:TagSession action is required to allow passing session tags.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowSamlIdentityAssumeRole",
            "Effect": "Allow",
            "Action": [
                "sts:AssumeRoleWithSAML",
                "sts:TagSession"
            ],
            "Principal": {"Federated":"arn:aws:iam::123456789012:saml-provider/ExampleCorpProvider"},
            "Condition": {
                "StringLike": {
                    "aws:RequestTag/cost-center": "*",
                    "aws:RequestTag/access-project": "*",
                    "aws:RequestTag/access-team": [
                        "eng",
                        "qas"
                    ]
                },
                "StringEquals": {"SAML:aud": "https://signin.aws.amazon.com/saml"}
            }
        }
    ]
}

The AllowSamlIdentityAssumeRole statement allows members of the Engineering and Quality Assurance teams to assume this role when they federate into AWS from the Example Corporation IdP. The ExampleCorpProvider SAML provider is defined in IAM. The administrator has already set up the SAML assertion to pass the three required session tags. The assertion can pass additional tags, but these three must be present. The identity's attributes can have any value for the cost-center and access-project tags. However, the access-team attribute value must match eng or qas to indicate that the identity is on the Engineering or Quality Assurance team.

Step 3B: Configure the SAML IdP

Configure your SAML IdP to pass the cost-center, access-project, and access-team attributes as session tags. For more information, see Passing session tags using AssumeRoleWithSAML.

To pass these attributes as session tags, include the following elements in your SAML assertion.

<Attribute Name="https://aws.amazon.com/SAML/Attributes/PrincipalTag:cost-center">
  <AttributeValue>987654</AttributeValue>
</Attribute>
<Attribute Name="https://aws.amazon.com/SAML/Attributes/PrincipalTag:access-project">
  <AttributeValue>peg</AttributeValue>
</Attribute>
<Attribute Name="https://aws.amazon.com/SAML/Attributes/PrincipalTag:access-team">
  <AttributeValue>eng</AttributeValue>
</Attribute>

Step 3C: Enable console access

Enable console access for your federated SAML users. For more information, see Enabling SAML 2.0 federated users to access the AWS Management Console.

Step 4: Test creating secrets

Federate into the AWS Management Console using the access-session-tags role. For more information, see Enabling SAML 2.0 federated users to access the AWS Management Console. Then follow the instructions in Step 4: Test creating secrets to create secrets. Use different SAML identities with attributes to match the tags that are indicated in the ABAC tutorial. For more information, see Step 4: Test creating secrets.

Step 5: Test viewing secrets

Follow the instructions in Step 5: Test viewing secrets to view the secrets that you created in the previous step. Use different SAML identities with attributes to match the tags that are indicated in the ABAC tutorial.

Step 6: Test scalability

Follow the instructions in Step 6: Test scalability to test scalability. Do this by adding a new identity in your SAML-based IdP with the following attributes:

Step 7: Test updating and deleting secrets

Follow the instructions in Step 7: Test updating and deleting secrets to update and delete secrets. Use different SAML identities with attributes to match the tags that are indicated in the ABAC tutorial.

Summary

You've now successfully completed all of the steps necessary to use SAML session tags and resource tags for permissions management.