Manage GCP Backend Bucket IAM Access

The gcp:compute/backendBucketIamMember:BackendBucketIamMember resource, part of the Pulumi GCP provider, manages IAM permissions for Compute Engine backend buckets. GCP provides three related resources for IAM management, each with different levels of control: BackendBucketIamPolicy (authoritative for entire policy), BackendBucketIamBinding (authoritative for a single role), and BackendBucketIamMember (non-authoritative for individual members). This guide focuses on understanding when to use each approach.

All three resources reference an existing backend bucket and require appropriate GCP project permissions. The examples are intentionally small. Combine them with your own backend bucket infrastructure and organizational IAM policies.

Replace the entire IAM policy for a backend bucket

When you need complete control over who can access a backend bucket, BackendBucketIamPolicy sets the entire IAM policy at once.

import * as pulumi from "@pulumi/pulumi";
import * as gcp from "@pulumi/gcp";

const admin = gcp.organizations.getIAMPolicy({
    bindings: [{
        role: "roles/viewer",
        members: ["user:jane@example.com"],
    }],
});
const policy = new gcp.compute.BackendBucketIamPolicy("policy", {
    project: imageBackend.project,
    name: imageBackend.name,
    policyData: admin.then(admin => admin.policyData),
});

import pulumi
import pulumi_gcp as gcp

admin = gcp.organizations.get_iam_policy(bindings=[{
    "role": "roles/viewer",
    "members": ["user:jane@example.com"],
}])
policy = gcp.compute.BackendBucketIamPolicy("policy",
    project=image_backend["project"],
    name=image_backend["name"],
    policy_data=admin.policy_data)

package main

import (
	"github.com/pulumi/pulumi-gcp/sdk/v9/go/gcp/compute"
	"github.com/pulumi/pulumi-gcp/sdk/v9/go/gcp/organizations"
	"github.com/pulumi/pulumi/sdk/v3/go/pulumi"
)

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		admin, err := organizations.LookupIAMPolicy(ctx, &organizations.LookupIAMPolicyArgs{
			Bindings: []organizations.GetIAMPolicyBinding{
				{
					Role: "roles/viewer",
					Members: []string{
						"user:jane@example.com",
					},
				},
			},
		}, nil)
		if err != nil {
			return err
		}
		_, err = compute.NewBackendBucketIamPolicy(ctx, "policy", &compute.BackendBucketIamPolicyArgs{
			Project:    pulumi.Any(imageBackend.Project),
			Name:       pulumi.Any(imageBackend.Name),
			PolicyData: pulumi.String(admin.PolicyData),
		})
		if err != nil {
			return err
		}
		return nil
	})
}

using System.Collections.Generic;
using System.Linq;
using Pulumi;
using Gcp = Pulumi.Gcp;

return await Deployment.RunAsync(() => 
{
    var admin = Gcp.Organizations.GetIAMPolicy.Invoke(new()
    {
        Bindings = new[]
        {
            new Gcp.Organizations.Inputs.GetIAMPolicyBindingInputArgs
            {
                Role = "roles/viewer",
                Members = new[]
                {
                    "user:jane@example.com",
                },
            },
        },
    });

    var policy = new Gcp.Compute.BackendBucketIamPolicy("policy", new()
    {
        Project = imageBackend.Project,
        Name = imageBackend.Name,
        PolicyData = admin.Apply(getIAMPolicyResult => getIAMPolicyResult.PolicyData),
    });

});

package generated_program;

import com.pulumi.Context;
import com.pulumi.Pulumi;
import com.pulumi.core.Output;
import com.pulumi.gcp.organizations.OrganizationsFunctions;
import com.pulumi.gcp.organizations.inputs.GetIAMPolicyArgs;
import com.pulumi.gcp.compute.BackendBucketIamPolicy;
import com.pulumi.gcp.compute.BackendBucketIamPolicyArgs;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;

public class App {
    public static void main(String[] args) {
        Pulumi.run(App::stack);
    }

    public static void stack(Context ctx) {
        final var admin = OrganizationsFunctions.getIAMPolicy(GetIAMPolicyArgs.builder()
            .bindings(GetIAMPolicyBindingArgs.builder()
                .role("roles/viewer")
                .members("user:jane@example.com")
                .build())
            .build());

        var policy = new BackendBucketIamPolicy("policy", BackendBucketIamPolicyArgs.builder()
            .project(imageBackend.project())
            .name(imageBackend.name())
            .policyData(admin.policyData())
            .build());

    }
}

resources:
  policy:
    type: gcp:compute:BackendBucketIamPolicy
    properties:
      project: ${imageBackend.project}
      name: ${imageBackend.name}
      policyData: ${admin.policyData}
variables:
  admin:
    fn::invoke:
      function: gcp:organizations:getIAMPolicy
      arguments:
        bindings:
          - role: roles/viewer
            members:
              - user:jane@example.com

This resource is authoritative: it replaces any existing policy on the backend bucket. The policyData comes from getIAMPolicy, which constructs a policy document from bindings. Each binding maps a role to a list of members. Use this approach when you want to define the complete permission set in one place, but be aware it will remove any permissions not explicitly listed.

Grant a role to multiple members at once

When multiple users or service accounts need the same level of access, BackendBucketIamBinding assigns them all to a role in a single resource.

import * as pulumi from "@pulumi/pulumi";
import * as gcp from "@pulumi/gcp";

const binding = new gcp.compute.BackendBucketIamBinding("binding", {
    project: imageBackend.project,
    name: imageBackend.name,
    role: "roles/viewer",
    members: ["user:jane@example.com"],
});

import pulumi
import pulumi_gcp as gcp

binding = gcp.compute.BackendBucketIamBinding("binding",
    project=image_backend["project"],
    name=image_backend["name"],
    role="roles/viewer",
    members=["user:jane@example.com"])

package main

import (
	"github.com/pulumi/pulumi-gcp/sdk/v9/go/gcp/compute"
	"github.com/pulumi/pulumi/sdk/v3/go/pulumi"
)

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		_, err := compute.NewBackendBucketIamBinding(ctx, "binding", &compute.BackendBucketIamBindingArgs{
			Project: pulumi.Any(imageBackend.Project),
			Name:    pulumi.Any(imageBackend.Name),
			Role:    pulumi.String("roles/viewer"),
			Members: pulumi.StringArray{
				pulumi.String("user:jane@example.com"),
			},
		})
		if err != nil {
			return err
		}
		return nil
	})
}

using System.Collections.Generic;
using System.Linq;
using Pulumi;
using Gcp = Pulumi.Gcp;

return await Deployment.RunAsync(() => 
{
    var binding = new Gcp.Compute.BackendBucketIamBinding("binding", new()
    {
        Project = imageBackend.Project,
        Name = imageBackend.Name,
        Role = "roles/viewer",
        Members = new[]
        {
            "user:jane@example.com",
        },
    });

});

package generated_program;

import com.pulumi.Context;
import com.pulumi.Pulumi;
import com.pulumi.core.Output;
import com.pulumi.gcp.compute.BackendBucketIamBinding;
import com.pulumi.gcp.compute.BackendBucketIamBindingArgs;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;

public class App {
    public static void main(String[] args) {
        Pulumi.run(App::stack);
    }

    public static void stack(Context ctx) {
        var binding = new BackendBucketIamBinding("binding", BackendBucketIamBindingArgs.builder()
            .project(imageBackend.project())
            .name(imageBackend.name())
            .role("roles/viewer")
            .members("user:jane@example.com")
            .build());

    }
}

resources:
  binding:
    type: gcp:compute:BackendBucketIamBinding
    properties:
      project: ${imageBackend.project}
      name: ${imageBackend.name}
      role: roles/viewer
      members:
        - user:jane@example.com

This resource is authoritative for the specified role: it controls the complete list of members for that role while preserving other roles on the backend bucket. The members property accepts a list of identity strings. This approach works well when you manage teams or groups that share the same permission level. You can use multiple BackendBucketIamBinding resources for different roles, but only one binding per role.

Add a single member to a role incrementally

When you need to grant access to one user without affecting existing permissions, BackendBucketIamMember adds individual members to roles.

import * as pulumi from "@pulumi/pulumi";
import * as gcp from "@pulumi/gcp";

const member = new gcp.compute.BackendBucketIamMember("member", {
    project: imageBackend.project,
    name: imageBackend.name,
    role: "roles/viewer",
    member: "user:jane@example.com",
});

import pulumi
import pulumi_gcp as gcp

member = gcp.compute.BackendBucketIamMember("member",
    project=image_backend["project"],
    name=image_backend["name"],
    role="roles/viewer",
    member="user:jane@example.com")

package main

import (
	"github.com/pulumi/pulumi-gcp/sdk/v9/go/gcp/compute"
	"github.com/pulumi/pulumi/sdk/v3/go/pulumi"
)

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		_, err := compute.NewBackendBucketIamMember(ctx, "member", &compute.BackendBucketIamMemberArgs{
			Project: pulumi.Any(imageBackend.Project),
			Name:    pulumi.Any(imageBackend.Name),
			Role:    pulumi.String("roles/viewer"),
			Member:  pulumi.String("user:jane@example.com"),
		})
		if err != nil {
			return err
		}
		return nil
	})
}

using System.Collections.Generic;
using System.Linq;
using Pulumi;
using Gcp = Pulumi.Gcp;

return await Deployment.RunAsync(() => 
{
    var member = new Gcp.Compute.BackendBucketIamMember("member", new()
    {
        Project = imageBackend.Project,
        Name = imageBackend.Name,
        Role = "roles/viewer",
        Member = "user:jane@example.com",
    });

});

package generated_program;

import com.pulumi.Context;
import com.pulumi.Pulumi;
import com.pulumi.core.Output;
import com.pulumi.gcp.compute.BackendBucketIamMember;
import com.pulumi.gcp.compute.BackendBucketIamMemberArgs;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;

public class App {
    public static void main(String[] args) {
        Pulumi.run(App::stack);
    }

    public static void stack(Context ctx) {
        var member = new BackendBucketIamMember("member", BackendBucketIamMemberArgs.builder()
            .project(imageBackend.project())
            .name(imageBackend.name())
            .role("roles/viewer")
            .member("user:jane@example.com")
            .build());

    }
}

resources:
  member:
    type: gcp:compute:BackendBucketIamMember
    properties:
      project: ${imageBackend.project}
      name: ${imageBackend.name}
      role: roles/viewer
      member: user:jane@example.com

This resource is non-authoritative: it adds one member to a role without removing other members. The member property (singular) accepts a single identity string. This is the safest approach for incremental changes because it won’t accidentally remove permissions granted elsewhere. You can combine multiple BackendBucketIamMember resources for the same role, and they can coexist with BackendBucketIamBinding resources as long as they target different roles.

Beyond these examples

These snippets focus on specific IAM management features: authoritative and non-authoritative IAM management, and role-based access control. They’re intentionally minimal rather than full access control configurations.

The examples reference pre-existing infrastructure such as backend buckets and GCP projects with appropriate permissions. They focus on configuring IAM permissions rather than provisioning the underlying resources.

To keep things focused, common IAM patterns are omitted, including:

Conditional IAM bindings (condition property)
Custom role definitions
Service account creation and management
Backend bucket creation and configuration

These omissions are intentional: the goal is to illustrate how each IAM resource type is wired, not provide drop-in access control modules. See the BackendBucketIamMember resource reference for all available configuration options.

Let's manage GCP Backend Bucket IAM Access

Get started with Pulumi Cloud, then follow our quick setup guide to deploy this infrastructure.

Try Pulumi Cloud for FREE

Frequently Asked Questions

Resource Selection & Conflicts

What's the difference between BackendBucketIamPolicy, BackendBucketIamBinding, and BackendBucketIamMember?

BackendBucketIamPolicy is authoritative and replaces the entire IAM policy. BackendBucketIamBinding is authoritative for a specific role but preserves other roles. BackendBucketIamMember is non-authoritative and adds a single member to a role while preserving existing members.

Why are my BackendBucketIam resources conflicting?

BackendBucketIamPolicy cannot be used with BackendBucketIamBinding or BackendBucketIamMember because they will fight over the policy. Use either Policy alone (authoritative) or Binding/Member (non-authoritative), but not both.

Can I use BackendBucketIamBinding and BackendBucketIamMember together?

Yes, but only if they don’t grant privileges to the same role. Each role should be managed by only one resource type to avoid conflicts.

Identity & Role Configuration

What member identity formats are supported?

Supported formats include allUsers, allAuthenticatedUsers, user:{email}, serviceAccount:{email}, group:{email}, domain:{domain}, projectOwner/Editor/Viewer:{projectid}, and federated identities like principal://iam.googleapis.com/....

How do I specify custom roles?

Custom roles must use the format [projects|organizations]/{parent-name}/roles/{role-name}. For example, projects/my-project/roles/my-custom-role or organizations/my-org/roles/my-custom-role.

What properties are immutable after creation?

All core properties are immutable: member, role, name, project, and condition. Changes to any of these require recreating the resource.

Import & Migration

How do I import a BackendBucketIamMember resource?

Use space-delimited identifiers:

pulumi import gcp:compute/backendBucketIamMember:BackendBucketIamMember editor "projects/{{project}}/global/backendBuckets/{{backend_bucket}} roles/viewer user:jane@example.com"

. For custom roles, use the full role name format.

Using a different cloud?

Explore security guides for other cloud providers:

AWS Guides Azure Guides