Configure GCP Cloud Functions IAM Bindings

The gcp:cloudfunctions/functionIamBinding:FunctionIamBinding resource, part of the Pulumi GCP provider, grants IAM roles to lists of members for Cloud Functions while preserving other roles in the function’s policy. This guide focuses on two capabilities: granting roles to multiple members and adding individual members incrementally.

FunctionIamBinding is authoritative for a given role, meaning it replaces all members for that role. It can coexist with FunctionIamMember resources as long as they manage different roles. The examples are intentionally small. Combine them with your own Cloud Functions and IAM principals.

Grant a role to multiple members at once

When multiple users or service accounts need the same access level, FunctionIamBinding assigns a role to all members in one resource.

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

const binding = new gcp.cloudfunctions.FunctionIamBinding("binding", {
    project: _function.project,
    region: _function.region,
    cloudFunction: _function.name,
    role: "roles/viewer",
    members: ["user:jane@example.com"],
});

import pulumi
import pulumi_gcp as gcp

binding = gcp.cloudfunctions.FunctionIamBinding("binding",
    project=function["project"],
    region=function["region"],
    cloud_function=function["name"],
    role="roles/viewer",
    members=["user:jane@example.com"])

package main

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

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		_, err := cloudfunctions.NewFunctionIamBinding(ctx, "binding", &cloudfunctions.FunctionIamBindingArgs{
			Project:       pulumi.Any(function.Project),
			Region:        pulumi.Any(function.Region),
			CloudFunction: pulumi.Any(function.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.CloudFunctions.FunctionIamBinding("binding", new()
    {
        Project = function.Project,
        Region = function.Region,
        CloudFunction = function.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.cloudfunctions.FunctionIamBinding;
import com.pulumi.gcp.cloudfunctions.FunctionIamBindingArgs;
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 FunctionIamBinding("binding", FunctionIamBindingArgs.builder()
            .project(function.project())
            .region(function.region())
            .cloudFunction(function.name())
            .role("roles/viewer")
            .members("user:jane@example.com")
            .build());

    }
}

resources:
  binding:
    type: gcp:cloudfunctions:FunctionIamBinding
    properties:
      project: ${function.project}
      region: ${function.region}
      cloudFunction: ${function.name}
      role: roles/viewer
      members:
        - user:jane@example.com

The role property specifies which IAM role to grant (e.g., “roles/viewer”). The members array lists all principals who receive this role; each entry uses a specific format like “user:jane@example.com” or “serviceAccount:app@project.iam.gserviceaccount.com”. This resource is authoritative for the role, replacing any existing members.

Add a single member to a role incrementally

Teams managing access grants individually use FunctionIamMember to add one principal without affecting other members of the same role.

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

const member = new gcp.cloudfunctions.FunctionIamMember("member", {
    project: _function.project,
    region: _function.region,
    cloudFunction: _function.name,
    role: "roles/viewer",
    member: "user:jane@example.com",
});

import pulumi
import pulumi_gcp as gcp

member = gcp.cloudfunctions.FunctionIamMember("member",
    project=function["project"],
    region=function["region"],
    cloud_function=function["name"],
    role="roles/viewer",
    member="user:jane@example.com")

package main

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

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		_, err := cloudfunctions.NewFunctionIamMember(ctx, "member", &cloudfunctions.FunctionIamMemberArgs{
			Project:       pulumi.Any(function.Project),
			Region:        pulumi.Any(function.Region),
			CloudFunction: pulumi.Any(function.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.CloudFunctions.FunctionIamMember("member", new()
    {
        Project = function.Project,
        Region = function.Region,
        CloudFunction = function.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.cloudfunctions.FunctionIamMember;
import com.pulumi.gcp.cloudfunctions.FunctionIamMemberArgs;
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 FunctionIamMember("member", FunctionIamMemberArgs.builder()
            .project(function.project())
            .region(function.region())
            .cloudFunction(function.name())
            .role("roles/viewer")
            .member("user:jane@example.com")
            .build());

    }
}

resources:
  member:
    type: gcp:cloudfunctions:FunctionIamMember
    properties:
      project: ${function.project}
      region: ${function.region}
      cloudFunction: ${function.name}
      role: roles/viewer
      member: user:jane@example.com

The member property specifies a single principal to grant the role. Unlike FunctionIamBinding, this resource is non-authoritative: it adds the member without removing others. You can use multiple FunctionIamMember resources for the same role, or combine them with FunctionIamBinding resources that manage different roles.

Beyond these examples

These snippets focus on specific IAM binding features: role-based access control and binding vs member grant patterns. They’re intentionally minimal rather than full access control configurations.

The examples reference pre-existing infrastructure such as Cloud Functions that need IAM configuration. They focus on configuring access rather than provisioning the functions themselves.

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

Conditional IAM bindings (condition property)
Full policy replacement (FunctionIamPolicy resource)
Custom role definitions
Federated identity configuration details

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

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Frequently Asked Questions

Resource Selection & Conflicts

Which IAM resources can I use together?

FunctionIamPolicy cannot be used with FunctionIamBinding or FunctionIamMember because they conflict over policy management. However, FunctionIamBinding and FunctionIamMember can be used together as long as they don’t grant privileges to the same role.

What's the difference between FunctionIamPolicy, FunctionIamBinding, and FunctionIamMember?

FunctionIamPolicy is authoritative and replaces the entire IAM policy. FunctionIamBinding is authoritative for a specific role but preserves other roles. FunctionIamMember is non-authoritative and preserves other members for the same role.

IAM Configuration

What format do custom roles require?

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

What member identity formats are supported?

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

How do I grant a role to multiple users at once?

Use FunctionIamBinding with a members array containing all the identities you want to grant the role to, such as ["user:jane@example.com", "user:john@example.com"].

Constraints & Immutability

What properties can't be changed after creation?

The cloudFunction, role, project, region, and condition properties are immutable and cannot be modified after the resource is created.

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