Configuring OpenID Connect for AWS

This document outlines the steps required to configure Pulumi to use OpenID Connect to authenticate with AWS. OIDC in AWS uses a web identity provider to assume an IAM role. Access to the IAM role is authorized using a trust policy that validates the contents of the OIDC token issued by the Pulumi Cloud.

Prerequisites

• You must have sufficient AWS IAM privileges to create identity providers and IAM roles.

Create the identity provider

1. In the navigation pane of the IAM console, choose Identity providers, and then choose Add provider.
2. In the Provider type section, click the radio button next to OpenID Connect.
3. For the Provider URL, provide the following URL: https://api.pulumi.com/oidc
4. For the Audience field, the value is the name of your Pulumi organization prefixed with aws: (e.g. aws:{org}). Then click Add provider.
   For the default project, the audience will use just the Pulumi organization name. This is to prevent regressions for legacy environments.

Configure the IAM role

Once you have created the identity provider, you will see a notification at the top of your screen prompting you to assign an IAM role.

1. Click the Assign role button.
2. Select the Create a new role option, then click Next.
3. On the IAM Create role page, ensure the Web identity radio button is selected.
4. In the Web identity section:
   • Select api.pulumi.com/oidc under Identity provider.
   • Select the name of your Pulumi organization under Audience. Then click Next.
5. On the Add permissions page, select the permissions that you want to grant to your Pulumi service. Then click Next.
6. Provide a name and optional description for the IAM role. Then click Create role.

Review trust policy

Next, select the trust relationships tab, which is where the trust policy of the role is defined.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Federated": "arn:aws:iam::123456789012:oidc-provider/api.pulumi.com/oidc"
            },
            "Action": "sts:AssumeRoleWithWebIdentity",
            "Condition": {
                "StringEquals": {
                    "api.pulumi.com/oidc:aud": "aws:<pulumi-org-name>"
                }
            }
        }
    ]
}

This definition currently allows any Pulumi service to assume this role, but only if the request comes from your organization. You can edit this policy to further limit access to this role to just the Pulumi ESC service, and you can make it even more granular by limiting access to a specific environment. For more detailed configuration for how you can set fine grained access control, see the following customizing claims documenation.

Before you log out of the AWS console, make sure to make a note of your role’s ARN value as you will need it in the next step.

Configure ESC for OIDC

To configure OIDC for Pulumi ESC, create a new environment in the Pulumi Console. Make sure that you have the correct organization selected in the left-hand navigation menu. Then:

1. Click the Environments link.

2. Click the Create environment button.

3. Provide a project to create your new environment in and a name for your environment.

4. Click the Create environment button.

5. You will be presented with a split-pane editor. Delete the default placeholder content in the editor and replace it with the following code:

   values:
     aws:
       login:
         fn::open::aws-login:
           oidc:
             duration: 1h
             roleArn: <your-oidc-iam-role-arn>
             sessionName: pulumi-environments-session
     environmentVariables:
       AWS_ACCESS_KEY_ID: ${aws.login.accessKeyId}
       AWS_SECRET_ACCESS_KEY: ${aws.login.secretAccessKey}
       AWS_SESSION_TOKEN: ${aws.login.sessionToken}
   

6. Replace <your-oidc-iam-role-arn> with the value from the previous steps.

7. Scroll to the bottom of the page and click Save.

You can validate that your configuration is working by running either of the following:

• esc open <your-org>/<your-project>/<your-environment> command of the ESC CLI
• pulumi env open <your-org>/<your-project>/<your-environment> command of the Pulumi CLI

Make sure to replace <your-org>, <your-project>, and <your-environment> with the values of your Pulumi organization, project, and environment file respectively. You should see output similar to the following:

{
  "aws": {
    "login": {
      "accessKeyId": "ASIA....",
      "secretAccessKey": "rtBS....",
      "sessionToken": "Fwo...."
    }
  },
  "environmentVariables": {
    "AWS_ACCESS_KEY_ID": "ASIA....",
    "AWS_SECRET_ACCESS_KEY": "rtBS....",
    "AWS_SESSION_TOKEN": "Fwo...."
  }
}

Subject claim customization

You can customize the subject claim in the OIDC token to control which Pulumi environments or users are allowed to assume a given IAM role. This allows for more granular access control than the default organization-level permissions.

By default, the subject claim has the following format:

pulumi:environments:org:<organization name>:env:<project name>/<environment name>

To customize the subject, use the subjectAttributes property in your environment configuration. This produces a subject with the prefix:

pulumi:environments:pulumi.organization.login:{ORGANIZATION_NAME}

Subject claim example

Consider the following ESC definition for project/development environment opened by user personA:

values:
  aws:
    login:
      fn::open::aws-login:
        oidc:
          ...
          subjectAttributes:
            - currentEnvironment.name
            - pulumi.user.login

The OIDC subject claim for this environment would be pulumi:environments:pulumi.organization.login:contoso:currentEnvironment.name:project/development:pulumi.user.login:personA. The role may only be assumed by project/development environment and user personA within the contoso organization:

"Condition": {
  "StringEquals": {
    "api.pulumi.com/oidc:aud": "aws:contoso",
    "api.pulumi.com/oidc:sub": "pulumi:environments:pulumi.organization.login:contoso:currentEnvironment.name:project/development:pulumi.user.login:personA"
  }
}

The subject always contains the prefix pulumi:environments:pulumi.organization.login:{ORGANIZATION_NAME} and every key configured will be appended to this prefix. The list of all possible options for subjectAttributes are:

• rootEnvironment.name: the name of the environment that is opened first. This root environment in turn opens other imported environments
• currentEnvironment.name: the full name (including the project) of the environment where the ESC login provider and subjectAttributes are defined
• pulumi.user.login: the login identifier of the user opening the environment
• pulumi.organization.login: the login identifier of the organization

When importing multiple environments into Pulumi IaC Stack Config, each environment is resolved separately. For example, if you import multiple environments into your Pulumi Stack with rootEnvironment.name attribute defined in all of them, then each rootEnvironment.name will resolve to the environment name where it is defined.