Access control (IAM vs ACLs) in GCP - Hands-On Comparison

Access control (IAM vs ACLs) in GCP

📖 Scenario: You are managing access to a Google Cloud Storage bucket for a small team. You want to control who can read and write files in the bucket using two common methods: IAM roles and ACLs.

🎯 Goal: Build a simple configuration that sets up a Cloud Storage bucket with specific IAM roles and ACLs to control access for users.

📋 What You'll Learn

Create a Cloud Storage bucket named exactly team-data-bucket

Assign the IAM role roles/storage.objectViewer to the user user:[e-mail]

Assign the IAM role roles/storage.objectAdmin to the user user:[e-mail]

Set an ACL on the bucket to give user:[e-mail] read access

Set an ACL on the bucket to give user:[e-mail] write access

💡 Why This Matters

🌍 Real World

Managing access to cloud storage is essential for protecting data and ensuring only authorized users can read or modify files.

💼 Career

Cloud engineers and administrators regularly configure IAM and ACLs to enforce security policies and compliance in cloud environments.

1

Create the Cloud Storage bucket

Create a Cloud Storage bucket named team-data-bucket using the resource block with google_storage_bucket.

GCP

# Your code here to create the bucket named team-data-bucket

Hint

Use the google_storage_bucket resource and set the name attribute exactly to team-data-bucket.

2

Add IAM roles for Alice and Bob

Add two google_storage_bucket_iam_member resources to assign the IAM role roles/storage.objectViewer to user:[e-mail] and the IAM role roles/storage.objectAdmin to user:[e-mail] for the bucket team-data-bucket.

GCP

resource "google_storage_bucket" "team_data_bucket" {
  name = "team-data-bucket"
}

# Your code here to add IAM roles for Alice and Bob

Hint

Use two google_storage_bucket_iam_member resources with the bucket attribute set to the bucket name, and assign the correct role and member.

3

Add ACLs for Charlie and Dana

Add two google_storage_bucket_acl entries to give user:[e-mail] read access and user:[e-mail] write access to the bucket team-data-bucket. Use the google_storage_bucket_acl resource with bucket set to the bucket name and specify the entity and role accordingly.

GCP

resource "google_storage_bucket" "team_data_bucket" {
  name = "team-data-bucket"
}

resource "google_storage_bucket_iam_member" "alice_viewer" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "roles/storage.objectViewer"
  member = "user:[e-mail]"
}

resource "google_storage_bucket_iam_member" "bob_admin" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "roles/storage.objectAdmin"
  member = "user:[e-mail]"
}

# Your code here to add ACLs for Charlie and Dana

Hint

Use google_storage_bucket_acl resources with role set to READER or WRITER and entity set to user-email format with a dash.

4

Complete the configuration with bucket location

Add the location attribute with value US to the google_storage_bucket resource team_data_bucket to specify the bucket's geographic location.

GCP

resource "google_storage_bucket" "team_data_bucket" {
  name = "team-data-bucket"
  # Add location attribute here
}

resource "google_storage_bucket_iam_member" "alice_viewer" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "roles/storage.objectViewer"
  member = "user:[e-mail]"
}

resource "google_storage_bucket_iam_member" "bob_admin" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "roles/storage.objectAdmin"
  member = "user:[e-mail]"
}

resource "google_storage_bucket_acl" "charlie_read" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "READER"
  entity = "[e-mail]"
}

resource "google_storage_bucket_acl" "dana_write" {
  bucket = google_storage_bucket.team_data_bucket.name
  role   = "WRITER"
  entity = "[e-mail]"
}

Hint

Add the location attribute inside the bucket resource block and set it to US.

Practice

1. What is the main difference between IAM and ACLs in Google Cloud Platform?

easy

A. IAM and ACLs are exactly the same in functionality.

B. IAM controls network traffic, and ACLs control user passwords.

C. IAM is only for virtual machines, ACLs are for storage only.

D. IAM manages access at resource levels using roles, while ACLs manage access at object or bucket levels.

Solution

1. Step 1: Understand IAM scope

   IAM controls access broadly by assigning roles to users or groups at resource levels like projects or services.

2. Step 2: Understand ACL scope

   ACLs control access more narrowly, typically at the object or bucket level in storage services.

3. Final Answer:

   IAM manages access at resource levels using roles, while ACLs manage access at object or bucket levels. -> Option D

4. Quick Check:

   IAM = broad roles, ACLs = fine-grained object permissions [OK]

Hint: IAM is broad roles; ACLs are fine-grained permissions [OK]

Common Mistakes:

• Confusing IAM with network controls
• Thinking ACLs control passwords
• Assuming IAM and ACLs are identical

2. Which of the following is the correct way to grant a user the role of 'Storage Object Viewer' using IAM in GCP?

easy

A. Edit the user's password in the IAM console.

B. Add the user to the ACL of the bucket with read permission.

C. Use the command: gcloud projects add-iam-policy-binding my-project --member='user:[e-mail]' --role='roles/storage.objectViewer'

D. Create a firewall rule allowing the user access.

Solution

1. Step 1: Identify IAM command syntax

   The correct gcloud command to grant IAM roles uses 'add-iam-policy-binding' with member and role flags.

2. Step 2: Verify role and member format

   The role 'roles/storage.objectViewer' and member format 'user:[e-mail]' are correct for granting read access to storage objects.

3. Final Answer:

   Use the command: gcloud projects add-iam-policy-binding my-project --member='user:[e-mail]' --role='roles/storage.objectViewer' -> Option C

4. Quick Check:

   IAM role grant uses gcloud add-iam-policy-binding [OK]

Hint: Use gcloud add-iam-policy-binding with correct role and member [OK]

Common Mistakes:

• Confusing ACL changes with IAM commands
• Editing passwords instead of roles
• Using firewall rules for access control

3. Given the following IAM policy snippet for a bucket, what access does the user 'user:[e-mail]' have?

{
  "bindings": [
    {
      "role": "roles/storage.objectAdmin",
      "members": ["user:[e-mail]"]
    }
  ]
}

medium

A. Alice can only read objects in the bucket.

B. Alice can create, delete, and update objects in the bucket.

C. Alice has no access to the bucket.

D. Alice can manage IAM policies but not objects.

Solution

1. Step 1: Identify the role assigned

   The role 'roles/storage.objectAdmin' allows full control over objects in the bucket, including create, delete, and update.

2. Step 2: Confirm member access

   The member 'user:[e-mail]' is assigned this role, so Alice has these permissions.

3. Final Answer:

   Alice can create, delete, and update objects in the bucket. -> Option B

4. Quick Check:

   roles/storage.objectAdmin = full object control [OK]

Hint: objectAdmin role means full object permissions [OK]

Common Mistakes:

• Confusing objectAdmin with read-only roles
• Assuming no access without explicit bucket ACL
• Mixing IAM roles with IAM policy management

4. You tried to grant a user access to a Cloud Storage bucket by adding them to the bucket's ACL, but they still cannot access the objects. What is the likely issue?

medium

A. The bucket has uniform bucket-level access enabled, which disables ACLs.

B. The user needs to restart their computer.

C. The user's email address was misspelled in the ACL.

D. The user was not granted an IAM role at the project level.

Solution

1. Step 1: Understand uniform bucket-level access

   When uniform bucket-level access is enabled, ACLs are disabled and only IAM controls access.

2. Step 2: Check ACL effect

   Adding users to ACLs has no effect if uniform bucket-level access is on, so the user cannot access objects despite ACL changes.

3. Final Answer:

   The bucket has uniform bucket-level access enabled, which disables ACLs. -> Option A

4. Quick Check:

   Uniform bucket-level access disables ACLs [OK]

Hint: Uniform bucket-level access disables ACLs [OK]

Common Mistakes:

• Assuming ACLs always work regardless of bucket settings
• Blaming user typos without verification
• Thinking user restart affects cloud permissions

5. You want to allow a third-party service to read specific objects in your Cloud Storage bucket without giving it full project access. Which approach is best?

hard

A. Add the service account to the bucket's ACL with READER permission on specific objects.

B. Enable uniform bucket-level access and grant the service account the storage.admin role.

C. Grant the service an IAM role at the project level with storage.objectViewer permission.

D. Create a firewall rule to allow the service IP to access the bucket.

Solution

1. Step 1: Understand access scope needs

   The third-party service needs access only to specific objects, not the whole project.

2. Step 2: Choose fine-grained control method

   ACLs allow granting permissions on specific objects or buckets, ideal for limited access.

3. Step 3: Evaluate other options

   IAM roles at project level are too broad; storage.admin is too powerful; firewall rules do not control storage access.

4. Final Answer:

   Add the service account to the bucket's ACL with READER permission on specific objects. -> Option A

5. Quick Check:

   Use ACLs for fine-grained object access [OK]

Hint: Use ACLs for specific object access, IAM for broad access [OK]

Common Mistakes:

• Granting overly broad IAM roles
• Confusing firewall rules with access control
• Using storage.admin role unnecessarily