Restricting service account usage

The Resource Manager provides constraints that can be used in organization policies to limit the usage of Identity and Access Management (IAM) service accounts.

Many of these constraints determine whether service accounts and other resources can be created or configured in specific ways. These constraints are not retroactive; they do not affect previously created and configured service accounts.

Before you begin

You must have permission to modify organization policies to set constraints. For example, the orgpolicy.policyAdmin role has permission to set organization policy constraints. Read the Using Constraints page to learn more about managing policies at the organization level.

Managed constraints

The following constraints are types of managed constraint, which are set to true or false. Managed constraints are predefined constraints that are built on the custom organization policy platform.

To learn how to create organization policies that enforce managed constraints, see Using managed constraints in an organization policy.

Prevent the Owner and Editor role from being granted to default service accounts

Some Google Cloud services automatically create default service accounts. When a default service account is created, it is automatically granted the Editor role (roles/editor) on your project. Someone might also choose to grant a highly privileged role, like the Editor role or Owner role (roles/owner), to a default service account at a later time.

The Editor and Owner roles are highly privileged basic roles. You shouldn't grant them to any principal in production, including default service accounts.

To prevent default service accounts from being granted the Editor or Owner roles, use the iam.managed.preventPrivilegedBasicRolesForDefaultServiceAccounts managed constraint. This constraint prevents default service accounts from ever being granted the Editor or Owner roles, either automatically or manually.

Boolean constraints

The following constraints are types of boolean constraint, which are set to true or false.

Disable automatic role grants to default service accounts

Some Google Cloud services automatically create default service accounts. When a default service account is created, it is automatically granted the Editor role (roles/editor) on your project.

To improve security, we strongly recommend that you disable the automatic role grant. Use the iam.automaticIamGrantsForDefaultServiceAccounts boolean constraint to disable the automatic role grant.

Disable service account creation

You can use the iam.disableServiceAccountCreation boolean constraint to disable the creation of new service accounts. This allows you to centralize management of service accounts while not restricting the other permissions your developers have on projects.

If you enforce this constraint in a project, then some Google Cloud services cannot automatically create default service accounts. As a result, if the project runs workloads that need to impersonate a service account, the project might not contain a service account that the workload can use. To address this issue, you can enable service account impersonation across projects. When you enable this feature, you can create service accounts in a centralized project, then attach the service accounts to resources in other projects.

For more information about organizing service accounts, see Where to create service accounts.

Disable service account key creation

You can use the iam.disableServiceAccountKeyCreation boolean constraint to disable the creation of new external service account keys and Cloud Storage HMAC keys. This lets you control the use of unmanaged long-term credentials for service accounts. When this constraint is set, user-managed credentials cannot be created for service accounts in projects affected by the constraint.

Disable service account key upload

You can use the iam.disableServiceAccountKeyUpload boolean constraint to disable the upload of external public keys to service accounts. When this constraint is set, users cannot upload public keys to service accounts in projects affected by the constraint.

Disable attachment of service accounts to resources in other projects

Each service account is located in a project. You can use the iam.disableCrossProjectServiceAccountUsage boolean constraint to prevent service accounts in a project from being attached to resources in other projects.

If you want to allow service accounts to be used across projects, see Enabling service account impersonation across projects.

Restrict removal of project liens when service accounts are used across projects

When you allow a project's service accounts to be attached to resources in other projects, IAM adds a project lien that prevents you from deleting the project. By default, anyone who has the resourcemanager.projects.updateLiens permission on the project can delete the lien.

If you enforce the iam.restrictCrossProjectServiceAccountLienRemoval boolean constraint, then principals can delete the lien only if they have the resourcemanager.projects.updateLiens permission on the organization.

We recommend enforcing this constraint if any of your projects allow service account impersonation across projects.

Disable workload identity cluster creation

You can use the iam.disableWorkloadIdentityClusterCreation boolean constraint to require that any new Google Kubernetes Engine clusters have the Workload Identity feature disabled at the time of their creation. If you want to tightly control service account access in your organization, you may want to disable Workload Identity in addition to service account creation and service account key creation.

Existing GKE clusters with Workload Identity enabled will not be affected, and will continue to work as normal.

Enforcing a boolean constraint

Console

To set an organization policy that enforces a constraint to restrict service account usage:

In the Google Cloud console, go to the Organization policies page.

Go to Organization policies
From the project picker, select the organization for which you want to restrict service account usage.
Click one of the service account usage boolean constraints listed on this page.
Click Manage policy.
Under Applies to, select Override parent's policy.
Click Add a rule.
Under Enforcement, select On.
To enforce the policy, click Set policy.

gcloud

Policies can be set through the Google Cloud CLI.

To restrict service account usage, run the following command:

gcloud resource-manager org-policies enable-enforce \
    --organization 'ORGANIZATION_ID' \
    BOOLEAN_CONSTRAINT

Where BOOLEAN_CONSTRAINT is the boolean constraint you want to enforce.

To disable enforcement, the same command can be issued with the

disable-enforce

command.

To learn about using constraints in organization policies, see Using Constraints.

Example policy with boolean constraint

The following code snippet shows an organization policy that enforces the iam.disableServiceAccountCreation boolean constraint, which prevents service accounts from being created:

name: organizations/012345678901/policies/iam.disableServiceAccountCreation
spec:
  rules:
  - enforce: true

List constraints

The following constraints are types of list constraint, which are set to a list of values.

Extend lifetime of OAuth 2.0 access tokens

You can create an OAuth 2.0 access token that provides short-lived credentials for a service account. By default, the maximum lifetime of an access token is 1 hour (3,600 seconds). However, you can extend the maximum lifetime to 12 hours. To do so, identify the service accounts that need an extended lifetime for access tokens, then add these service accounts to an organization policy that includes the constraints/iam.allowServiceAccountCredentialLifetimeExtension list constraint.

Limit lifetime of service account keys

A service account key lets you authenticate a request as a service account. By default, service account keys never expire. You can change this default by setting an expiry time for all newly created keys in your project, folder, or organization.

To set an expiry time, use the constraints/iam.serviceAccountKeyExpiryHours list constraint to specify the number of hours for which a newly created key is valid. After this amount of time, the service account key expires, and you can no longer use it.

This list constraint accepts the following ALLOW values; it does not accept DENY values. As a best practice, use the shortest expiry time that meets your needs:

1h: 1 hour
8h: 8 hours
24h: 24 hours (1 day)
168h: 168 hours (7 days)
336h: 336 hours (14 days)
720h: 720 hours (30 days)
1440h: 1,440 hours (60 days)
2160h: 2,160 hours (90 days)

The constraints/iam.serviceAccountKeyExpiryHours constraint can't be merged with a parent policy. To enforce this constraint, you must either replace or inherit the parent policy.

Specify allowed external identity providers

If you use workload identity federation, which lets external identities access Google Cloud resources, you can specify which external identity providers are allowed. By default, all providers are allowed. To set a limit, use the constraints/iam.workloadIdentityPoolProviders list constraint to specify URIs for the allowed providers, using the following formats:

Amazon Web Services (AWS): https://sts.amazonaws.com

To limit which AWS accounts are allowed, use the constraints/iam.workloadIdentityPoolAwsAccounts list constraint as described on this page.
Microsoft Azure: https://sts.windows.net/azure-tenant-id
Other identity providers that support OpenID Connect (OIDC): Use the issuer URI from your identity provider.

Specify allowed AWS accounts

If you use workload identity federation, which lets external identities access Google Cloud resources, you can specify which AWS accounts are allowed to access your resources. By default, workloads from any AWS account are allowed to access your Google Cloud resources. To limit which AWS accounts are allowed, use the constraints/iam.workloadIdentityPoolAwsAccounts list constraint to specify a list of allowed account IDs.

Automatically disable exposed service account keys

Google Cloud occasionally detects that a particular service account key has been exposed—for example, it might detect a key in a public repository. To specify what Google Cloud does with these keys, use the iam.serviceAccountKeyExposureResponse list constraint.

This list constraint accepts the following ALLOW values; it doesn't accept DENY values.

DISABLE_KEY: If Google Cloud detects an exposed key, it will automatically disable the key. It also creates a Cloud Audit Logs event and sends a notification about the exposed key to project owners and security contacts.

Note: Starting on June 16, 2024, if you don't set a value for this constraint, Google Cloud will default to the behavior described for DISABLE_KEY.
WAIT_FOR_ABUSE: Google Cloud won't proactively disable exposed keys. However, Google Cloud might still disable exposed keys if they're used in ways that adversely affect the platform. Regardless of whether the exposed key is disabled, Google Cloud creates a Cloud Audit Logs event and sends a notification about the exposed key to project owners and security contacts.

When Google Cloud detects a exposed key or disables an exposed key, it also does the following:

Generates Cloud Audit Logs events.
- When Google Cloud detects that a key has been exposed, an abuse event is created in the Abuse Event logs.
- When Google Cloud disables a key, the audit logs contain the disable action by principal gcp-compromised-key-response@system.gserviceaccount.com.
Sets the extendedStatus.value field of the exposed or disabled key. The extended status field includes the location where the leak was detected.

We strongly recommend that you set this constraint to DISABLE_KEY. Setting this constraint to WAIT_FOR_ABUSE increases the risk that exposed keys will be misused.

If you do decide to set the constraint to WAIT_FOR_ABUSE, we recommend that you subscribe to Cloud Audit Logs events, review your security contact information in Essential Contacts, and ensure that your security contacts respond to notifications in a timely manner.

The iam.serviceAccountKeyExposureResponse constraint can't be merged with a parent policy. To enforce this constraint, you must replace the parent policy.

Setting a list constraint

Console

To set an organization policy that contains a list constraint:

In the Google Cloud console, go to the Organization policies page.

Go to Organization policies
From the project picker, select the resource for which you want to set the organization policy.
On the Organization policies page, select a constraint from the list. The Policy details page for that constraint appears.
To update the organization policy for this resource, click Manage policy.
Under Policy enforcement, select an enforcement option:
- To merge and evaluate your organization policies together, select Merge with parent. For more information about inheritance and the resource hierarchy, see Understanding hierarchy evaluation.
- To override policies inherited from a parent resource, select Replace.
Click Add a rule.
Under Policy values, select Custom.
Under Policy type, select Allow.
Under Custom values, enter the first value for the list constraint.
1. If you want to add more values, click Add value to create more rows, and add one value to each row.
When you have finished adding values, click Done.
To enforce the policy, click Set policy.

gcloud

Policies can be set through the Google Cloud CLI:

gcloud resource-manager org-policies allow \
    CONSTRAINT_NAME \
    VALUE_1 [VALUE_N ...] \
    --organization=ORGANIZATION_ID \

Replace the following values:

CONSTRAINT_NAME: The name of the list constraint. For example, constraints/iam.allowServiceAccountCredentialLifetimeExtension.
VALUE_1, VALUE_N...: Values for the list constraint.

To learn about using constraints in organization policies, see Using Constraints.

Example policy with list constraint

The following code snippet shows an organization policy that enforces the iam.allowServiceAccountCredentialLifetimeExtension list constraint, which extends the maximum lifetime of OAuth 2.0 access tokens for listed service accounts:

name: organizations/012345678901/policies/iam.allowServiceAccountCredentialLifetimeExtension
spec:
  rules:
  - values:
      allowedValues:
      - SERVICE_ACCOUNT_ADDRESS

Error messages

Disable service account creation

If iam.disableServiceAccountCreation is enforced, creating a service account will fail with the error:

FAILED_PRECONDITION: Service account creation is not allowed on this project.

Disable service account key creation

If iam.disableServiceAccountKeyCreation is enforced, creating a service account will fail with the error:

FAILED_PRECONDITION: Key creation is not allowed on this service account.

Disable workload identity cluster creation

If iam.disableWorkloadIdentityClusterCreation is enforced, creating a GKE cluster with Workload Identity enabled will fail with the error:

FAILED_PRECONDITION: Workload Identity is disabled by the organization
policy constraints/iam.disableWorkloadIdentityClusterCreation. Contact your
administrator to enable this feature.

Troubleshooting known issues

Default service accounts

Applying the iam.disableServiceAccountCreation constraint will prevent the creation of service accounts in that project. This limitation also affects Google Cloud services that, when enabled, automatically create default service accounts in the project, such as:

Compute Engine
GKE
App Engine
Dataflow

If the iam.disableServiceAccountCreation constraint is applied, attempting to enable these services will fail because their default service accounts cannot be created.

To resolve this issue:

Temporarily remove the iam.disableServiceAccountCreation constraint.
Enable the desired services.
Create any other desired service accounts.
Finally, re-apply the constraint.