Using IAM securely

Introduction

This page recommends security best practices that you should keep in mind when using IAM.

This page is designed for users who are proficient with IAM. If you are just starting out with IAM, these instructions will not teach you how to use it; instead, new users should start with the IAM Quickstart.

Least privilege

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For security-critical resources, avoid basic roles, such as (roles/owner, roles/editor, and roles/viewer). Instead, grant predefined roles to allow the least-permissive access necessary.
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Grant basic roles in the following cases:
  • When the Google Cloud service does not provide a predefined role. See the predefined roles table for a list of all available predefined roles.
  • When you want to grant broader permissions for a project. This often happens when you're granting permissions in development or test environments.
  • When you work in a small team where the team members don't need granular permissions.
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Treat each component of your application as a separate trust boundary. If you have multiple services that require different permissions, create a separate service account for each of the services, then grant only the required permissions to each service account.
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Remember that the policies for child resources inherit from the policies for their parent resources. For example, if the policy for a project grants a user the ability to administer Compute Engine virtual machine (VM) instances, then the user can administer any Compute Engine VM in that project, regardless of the policy you set on each VM.
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Grant roles at the smallest scope needed. For example, if a user only needs access to publish Pub/Sub topics, grant the Publisher role to the user for that topic.
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Specify which members can act as service accounts. Users who are granted the Service Account Actor role for a service account can access all the resources for which the service account has access. Therefore, be cautious when granting the Service Account Actor role to a user.
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Specify who has access to create and manage service accounts in your project.
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Granting the Project IAM Admin and Folder IAM Admin predefined roles will allow access to modify IAM policies without also allowing direct read, write, and administrative access to all resources.

Granting the Owner (roles/owner) role to a member will allow them to access and modify almost all resources, including modifying IAM policies. This amount of privilege is potentially risky. Grant the Owner (roles/owner) role only when (nearly) universal access is required.

Service accounts and service account keys

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Rotate your service account keys using the IAM service account API. You can rotate a key by creating a new key, switching applications to use the new key and then deleting old key. Use the serviceAccount.keys.create() method and serviceAccount.keys.delete() method together to automate the rotation.
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Implement processes to manage user-managed service account keys.
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Be careful not to confuse encryption keys with service account keys. Encryption keys are typically used to encrypt data and service account keys are used for secure access to Google Cloud APIs.
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Do not delete service accounts that are in use by running instances. This could result in all or parts of your application to fail if you have not transitioned to using an alternative service account first.
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Use the display name of a service account to keep track of what they are used for and what permissions they should have.
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Don't check in the service account keys into the source code or leave them in the Downloads directory.

Auditing

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Use logs from Cloud Audit Logs to regularly audit changes to your IAM policy.
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Export audit logs to Cloud Storage to store your logs for long periods of time.
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Audit who has the ability to change your IAM policies on your projects.
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Manage access to logs using Logging roles.
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Apply the same access policies to the Google Cloud resource that you use to export logs as applied to the logs viewer.
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Use logs from Cloud Audit Logs to regularly audit access to service account keys.

Policy management

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Set organization-level IAM policies to grant access to all projects in your organization.
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Grant roles to a Google group instead of individual users when possible. It is easier to add members to and remove members from a Google group instead of updating an IAM policy to add or remove users.
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If you need to grant multiple roles to allow a particular task, create a Google group, grant the roles to that group, and then add users to that group.