Use custom organization policies for allow policies (original) (raw)

This page shows you how to use Organization Policy Service custom constraints to restrict specific operations on the following Google Cloud resources:

• iam.googleapis.com/AllowPolicy

To learn more about Organization Policy, seeCustom organization policies.

About organization policies and constraints

The Google Cloud Organization Policy Service gives you centralized, programmatic control over your organization's resources. As theorganization policy administrator, you can define an organization policy, which is a set of restrictions called constraints that apply to Google Cloud resources and descendants of those resources in theGoogle Cloud resource hierarchy. You can enforce organization policies at the organization, folder, or project level.

Organization Policy provides built-in managed constraintsfor various Google Cloud services. However, if you want more granular, customizable control over the specific fields that are restricted in your organization policies, you can also create custom constraints and use those custom constraints in an organization policy.

Policy inheritance

By default, organization policies are inherited by the descendants of the resources on which you enforce the policy. For example, if you enforce a policy on a folder, Google Cloud enforces the policy on all projects in the folder. To learn more about this behavior and how to change it, refer toHierarchy evaluation rules.

Benefits

You can use custom organization policies that reference IAM attributes to control how your allow policies can be modified. Specifically, you can control the following:

• Who can be granted roles
• Who can have their roles revoked
• Which roles can be granted
• Which roles can be revoked

For example, you can prevent roles that contain the word admin from being granted to principals whose email addresses end in @gmail.com.

Limitations

• Custom organization policies in dry-run mode that reference IAM attributes have some limitations. Namely, audit logs for violations that involve the setIamPolicy method might be missing the following fields:
  • resourceName
  • serviceName
  • methodName
• Audit logs aren't generated for all IAM-related custom organization policy violations. Namely, if a custom organization policy causes a setIamPolicy operation on the organization resource to fail, then Google Cloud doesn't generate an audit log for that event.
• Custom organization policies that reference IAM attributes don't affect the following:
  • Default grants by Cloud Storage ACLs.
  • Automatic role grants for Cloud Storage convenience values andBigQuery default dataset access.
  • Roles granted by default allow policies—for example, a project creator automatically being granted the Owner role (roles/owner) on the project.
• Users can be sent invitations to become owners, even if you have a custom organization policy that prevents the Owner role (roles/owner) from being granted. However, while the custom organization policy doesn't prevent an invitation from being sent, it does prevent invited users from being granted the Owner role. If invited users try to accept the invitation, they'll encounter an error and won't be granted the Owner role.
• Some actions in Google Cloud, such as creating resources or enabling APIs, involve automatically granting a role to a service agent or default service account. If an action involves automatically granting a role and an organization policy prevents that role from being granted, then the entire operation might fail.
  If you encounter this issue, you can usetagsto temporarily disable the constraint that prevents the role grant. Then, perform the action. After the action finishes, re-enable the constraint.

Before you begin

• If you want to test out custom organization policies that reference IAM resources, create a new project. Testing these organization policies in an existing project could disrupt security workflows.
  1. In the Google Cloud console, go to the project selector page.
     Go to project selector
  2. Select or create a Google Cloud project.
     Roles required to select or create a project
     • Select a project: Selecting a project doesn't require a specific IAM role—you can select any project that you've been granted a role on.
     • Create a project: To create a project, you need the Project Creator role (roles/resourcemanager.projectCreator), which contains theresourcemanager.projects.create permission. Learn how to grant roles.

Required roles

To get the permissions that you need to manage organization policies, ask your administrator to grant you the following IAM roles:

• Organization Policy Administrator (roles/orgpolicy.policyAdmin) on the organization
• Test the organization policies described on this page:Project IAM Admin (roles/resourcemanager.projectIamAdmin) on the project

For more information about granting roles, see Manage access to projects, folders, and organizations.

These predefined roles contain the permissions required to manage organization policies. To see the exact permissions that are required, expand the Required permissions section:

Required permissions

The following permissions are required to manage organization policies:

• orgpolicy.* on the organization
• Test the organization policies described on this page: resourcemanager.projects.setIamPolicy on the project

You might also be able to get these permissions with custom roles or other predefined roles.

Set up a custom constraint

A custom constraint is defined in a YAML file by the resources, methods, conditions, and actions that are supported by the service on which you are enforcing the organization policy. Conditions for your custom constraints are defined usingCommon Expression Language (CEL). For more information about how to build conditions in custom constraints using CEL, see the CEL section ofCreating and managing custom constraints.

Console

To create a custom constraint, do the following:

1. In the Google Cloud console, go to the Organization policies page.
   Go to Organization policies
2. From the project picker, select the project that you want to set the organization policy for.
3. Click Custom constraint.
4. In the Display name box, enter a human-readable name for the constraint. This name is used in error messages and can be used for identification and debugging. Don't use PII or sensitive data in display names because this name could be exposed in error messages. This field can contain up to 200 characters.
5. In the Constraint ID box, enter the name that you want for your new custom constraint. A custom constraint can only contain letters (including upper and lowercase) or numbers, for example custom.disableGkeAutoUpgrade. This field can contain up to 70 characters, not counting the prefix (custom.), for example,organizations/123456789/customConstraints/custom. Don't include PII or sensitive data in your constraint ID, because it could be exposed in error messages.
6. In the Description box, enter a human-readable description of the constraint. This description is used as an error message when the policy is violated. Include details about why the policy violation occurred and how to resolve the policy violation. Don't include PII or sensitive data in your description, because it could be exposed in error messages. This field can contain up to 2000 characters.
7. In the Resource type box, select the name of the Google Cloud REST resource containing the object and field that you want to restrict—for example,container.googleapis.com/NodePool. Most resource types support up to 20 custom constraints. If you attempt to create more custom constraints, the operation fails.
8. Under Enforcement method, select whether to enforce the constraint on a RESTCREATE method or on both CREATE and UPDATE methods. If you enforce the constraint with the UPDATE method on a resource that violates the constraint, changes to that resource are blocked by the organization policy unless the change resolves the violation.

Not all Google Cloud services support both methods. To see supported methods for each service, find the service in Supported services.

1. To define a condition, click Edit condition.
   1. In the Add condition panel, create a CEL condition that refers to a supported service resource, for example, resource.management.autoUpgrade == false. This field can contain up to 1000 characters. For details about CEL usage, see Common Expression Language. For more information about the service resources you can use in your custom constraints, see Custom constraint supported services.
   2. Click Save.
2. Under Action, select whether to allow or deny the evaluated method if the condition is met.

The deny action means that the operation to create or update the resource is blocked if the condition evaluates to true.

The allow action means that the operation to create or update the resource is permitted only if the condition evaluates to true. Every other case except ones explicitly listed in the condition is blocked.

1. Click Create constraint.

When you have entered a value into each field, the equivalent YAML configuration for this custom constraint appears on the right.

gcloud

1. To create a custom constraint, create a YAML file using the following format:

   name: organizations/ORGANIZATION_ID/customConstraints/CONSTRAINT_NAME resourceTypes:

   • RESOURCE_NAME methodTypes:
   • CREATE

• UPDATE condition: "CONDITION" actionType: ACTION displayName: DISPLAY_NAME description: DESCRIPTION

Replace the following:

• ORGANIZATION_ID: your organization ID, such as123456789.
• CONSTRAINT_NAME: the name that you want for your new custom constraint. A custom constraint can only contain letters (including upper and lowercase) or numbers, for example, custom.denyProjectIAMAdmin. This field can contain up to 70 characters.
• RESOURCE_NAME: the fully qualified name of the Google Cloud resource containing the object and field that you want to restrict. For example,iam.googleapis.com/AllowPolicy.
• CONDITION: a CEL condition that is written against a representation of a supported service resource. This field can contain up to 1000 characters. For example,`resource.bindings.exists(binding, RoleNameMatches(binding.role, ['roles/resourcemanager.projectIamAdmin']))`.

For more information about the resources available to write conditions against, seeSupported resources.

• ACTION: the action to take if the condition is met. Possible values are ALLOW andDENY.

The allow action means that if the condition evaluates to true, the operation to create or update the resource is permitted. This also means that every other case except the one explicitly listed in the condition is blocked.

The deny action means that if the condition evaluates to true, the operation to create or update the resource is blocked.

• DISPLAY_NAME: a human-friendly name for the constraint. This field can contain up to 200 characters.
• DESCRIPTION: a human-friendly description of the constraint to display as an error message when the policy is violated. This field can contain up to 2000 characters.

1. After you have created the YAML file for a new custom constraint, you must set it up to make it available for organization policies in your organization. To set up a custom constraint, use the gcloud org-policies set-custom-constraint command:

    gcloud org-policies set-custom-constraint CONSTRAINT_PATH

Replace CONSTRAINT_PATH with the full path to your custom constraint file. For example, /home/user/customconstraint.yaml.

After this operation is complete, your custom constraints are available as organization policies in your list of Google Cloud organization policies.

1. To verify that the custom constraint exists, use the gcloud org-policies list-custom-constraints command:

   gcloud org-policies list-custom-constraints --organization=ORGANIZATION_ID

Replace ORGANIZATION_ID with the ID of your organization resource.

For more information, see Viewing organization policies.

Enforce a custom organization policy

You can enforce a constraint by creating an organization policy that references it, and then applying that organization policy to a Google Cloud resource.

Console

1. In the Google Cloud console, go to the Organization policies page.
   Go to Organization policies
2. From the project picker, select the project that you want to set the organization policy for.
3. From the list on the Organization policies page, select your constraint to view the Policy details page for that constraint.
4. To configure the organization policy for this resource, click Manage policy.
5. On the Edit policy page, select Override parent's policy.
6. Click Add a rule.
7. In the Enforcement section, select whether this organization policy is enforced or not.
8. Optional: To make the organization policy conditional on a tag, clickAdd condition. Note that if you add a conditional rule to an organization policy, you must add at least one unconditional rule or the policy cannot be saved. For more information, see Setting an organization policy with tags.
9. Click Test changes to simulate the effect of the organization policy. For more information, see Test organization policy changes with Policy Simulator.
10. To enforce the organization policy in dry-run mode, click Set dry run policy. For more information, see Create an organization policy in dry-run mode.
11. After you verify that the organization policy in dry-run mode works as intended, set the live policy by clicking Set policy.

gcloud

1. To create an organization policy with boolean rules, create a policy YAML file that references the constraint:

    name: projects/PROJECT_ID/policies/CONSTRAINT_NAME
    spec:
      rules:
      - enforce: true
    
    dryRunSpec:
      rules:
      - enforce: true

Replace the following:

• PROJECT_ID: the project that you want to enforce your constraint on.
• CONSTRAINT_NAME: the name you defined for your custom constraint. For example, custom.denyProjectIAMAdmin.

1. To enforce the organization policy indry-run mode, run the following command with the dryRunSpec flag:

    gcloud org-policies set-policy POLICY_PATH \
      --update-mask=dryRunSpec

Replace POLICY_PATH with the full path to your organization policy YAML file. The policy requires up to 15 minutes to take effect.

1. After you verify that the organization policy in dry-run mode works as intended, set the live policy with the org-policies set-policy command and the spec flag:

    gcloud org-policies set-policy POLICY_PATH \
      --update-mask=spec

Replace POLICY_PATH with the full path to your organization policy YAML file. The policy requires up to 15 minutes to take effect.

Test the custom organization policy

Optionally, you can test the organization policy by setting the policy and then trying to take an action that the policy should prevent.

Create the constraint

1. Save the following file as constraint-deny-project-iam-admin.

name: organizations/ORG_ID/customConstraints/custom.denyProjectIAMAdmin  
resourceTypes: iam.googleapis.com/AllowPolicy  
methodTypes:  
  - CREATE  
  - UPDATE  
condition:  
  "resource.bindings.exists(  
    binding,  
    RoleNameMatches(binding.role, ['roles/resourcemanager.projectIamAdmin']) &&  
    binding.members.exists(member,  
      MemberSubjectMatches(member, ['user:EMAIL_ADDRESS'])  
    )  
  )"  
actionType: DENY  
displayName: Do not allow EMAIL_ADDRESS to be granted the Project IAM Admin role.  

Replace the following values:

• ORG_ID: the numeric ID of your Google Cloud organization.
• MEMBER_EMAIL_ADDRESS: the email address of the principal that you want to use to test the custom constraint. While the constraint is active, this principal won't be able to be granted the Project IAM Admin role (roles/resourcemanager.projectIamAdmin) on the project that you enforce the constraint for.

1. Apply the constraint:

gcloud org-policies set-custom-constraint ~/constraint-deny-project-iam-admin.yaml  

1. Verify that the constraint exists:

gcloud org-policies list-custom-constraints --organization=ORGANIZATION_ID  

Create the policy

1. Save the following file as policy-deny-project-iam-admin.yaml:

name: projects/PROJECT_ID/policies/custom.denyProjectIamAdmin  
spec:  
  rules:  
  - enforce: true  

Replace PROJECT_ID with your project ID. 2. Apply the policy:

gcloud org-policies set-policy ~/policy-deny-project-iam-admin.yaml  

1. Verify that the policy exists:

gcloud org-policies list --project=PROJECT_ID  

After you apply the policy, wait for about two minutes for Google Cloud to start enforcing the policy.

Test the policy

Try to grant the Project IAM Admin role (roles/resourcemanager.projectIamAdmin) to the principal whose email address you included in the custom constraint. Before running the command, replace the following values:

• PROJECT_ID: The ID of the Google Cloud project where you enforced the constraint
• EMAIL_ADDRESS: The email address of the principal that you specified when you created the organization policy constraint.

gcloud projects add-iam-policy-binding PROJECT_ID
--member=user:EMAIL_ADDRESS --role=roles/resourcemanager.projectIamAdmin

The output is the following:

Operation denied by custom org policies: ["customConstraints/custom.denyProjectIAMAdmin": "EMAIL_ADDRESS can't be granted the Project IAM Admin role."]

Example custom organization policies for common use cases

The following table provides the syntax of some custom constraints for common use cases.

The following examples use the CEL macros all and exists. For more information about these macros, seeMacros to evaluate lists.

Conditional organization policies

You can make a custom organization policy conditional usingtags. For example, imagine that you wrote the following custom constraint to prevent any roles that start with roles/storage. from being granted:

name: organizations/ORG_ID/customConstraints/custom.dontgrantStorageRoles
resourceTypes: iam.googleapis.com/AllowPolicy
methodTypes:
  - CREATE
  - UPDATE
condition:
  "resource.bindings.exists(
    binding,
    RoleNameStartsWith(binding.role, ['roles/storage.'])
  )"
actionType: DENY
displayName: Prevent roles that start with "roles/storage." from being granted

To enforce the constraint conditionally, you could create an organization policy like the following:

name: organizations/ORG_ID/policies/custom.dontgrantStorageRoles
spec:
  rules:
  - condition:
      expression: "resource.matchTag('ORG_ID/environment', 'dev')"
    enforce: true
  - enforce: false

This organization policy prevents roles that start with roles/storage. from being granted on any resource that also has the tag environment=dev.

Identity and Access Management supported resources

IAM supports the AllowPolicy resource. This resource has the attribute resources.bindings attribute, which is returned for all methods that modify a resource's allow policy. All of the methods that modify a resource's allow policy end with setIamPolicy.

The resource.bindings attribute has the following structure, whereBINDINGS is an array of role bindings that were modified during a change to an allow policy:

{
  "bindings": {
    BINDINGS
  }
}

Each binding in resource.bindings has the following structure, whereROLE is the name of the role in the role binding andMEMBERS is a list of identifiers for all principals that were added to or removed from the role binding:

{
  "role": "ROLE"
  "members": {
    MEMBERS
  }
}

To see the formats that principal identifiers can have, see Principal identifiers.

You can only evaluate the resource.bindings attribute and its fields using thesupported functions. Other operators and functions—like ==, !=, in, contains, startsWith, andendsWith—are not supported.

Supported functions

You can use the following CEL functions to evaluate individual roles and members in a binding.

To evaluate all bindings in the bindings array or all members in the membersarray, use the all and exists macros. For more information, see Macros to evaluate lists on this page.

You can also use the logical operators && (and) and || (or) to write multipart conditions.

Macros to evaluate lists

Use the all and exists macros to evaluate a condition expression for a list of items.

Conditions with nested lists

In general, if your condition includes nested lists, you should use the same macro for all lists in the condition.

Consider the following examples:

• If your policy has the actionType ALLOW, then use the all macro for both the members list and the bindings list to ensure that policy modifications are only allowed if all members in all modified bindings satisfy the condition.
• If your policy has the actionType DENY, then use the exists macro for both the members list and the bindings list to ensure that policy modifications aren't allowed if any member in any modified binding satisfies the condition.

Mixing macros in a single condition might result in a condition that doesn't behave how you intended.

For example, imagine that you want to prevent roles from being granted to members outside of the example.com organization. The example.comorganization has the ID 123456789012.

To accomplish this goal, you write the following condition:

Not recommended — misconfigured condition

"resource.bindings.all( binding, binding.members.exists(member, MemberInPrincipalSet(member, ['//cloudresourcemanager.googleapis.com/organizations/123456789012']) ) )"

This condition appears to prevent roles from being granted to members outside of the example.com organization. However, the condition evaluates to true if_any_ member in each of the modified role bindings is in the example.comorganization. As a result, you can still grant roles to members outside of theexample.com organization if you also grant the same role to a member in theexample.com organization.

For example, the condition evaluates to true for the following set of bindings, even though one of the members isn't in the example.comorganization:

"bindings": [ { "members": [ "user:raha@altostrat.com", "user:jie@example.com" ], "role": "roles/resourcemanager.projectCreator" } ],

Instead, you should write a condition like the following:

Recommended — correctly configured condition

"resource.bindings.all( binding, binding.members.all(member, MemberInPrincipalSet(member, ['//cloudresourcemanager.googleapis.com/organizations/123456789012']) ) )"

Using the all macro for both the members.bindings array and theresource.bindings array ensures that the condition evaluates to true only if all members in all bindings are in the example.com principal set.

Supported principal types for MemberTypeMatches

The MemberTypeMatches function requires you to specify which principal type the specified member must match.

The following table lists the principal types that you can enter and a description of what the principal type represents. It also lists the principal identifiers that correspond with each principal type. These identifiers are the values that are used in IAM policies.

What's next

• Learn more aboutOrganization Policy Service.
• Learn more about how tocreate and manage organization policies.
• See the full list of managedorganization policy constraints.