GCP - Basic Information
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Last updated
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Google Cloud uses a Resource hierarchy that is similar, conceptually, to that of a traditional filesystem. This provides a logical parent/child workflow with specific attachment points for policies and permissions.
At a high level, it looks like this:
A virtual machine (called a Compute Instance) is a resource. A resource resides in a project, probably alongside other Compute Instances, storage buckets, etc.
It's possible to migrate a project without any organization to an organization with the permissions roles/resourcemanager.projectCreator and roles/resourcemanager.projectMover. If the project is inside other organization, it's needed to contact GCP support to move them out of the organization first. For more info check this.
Allow to centralize control over your organization's cloud resources:
Centralize control to configure restrictions on how your organization’s resources can be used.
Define and establish guardrails for your development teams to stay within compliance boundaries.
Help project owners and their teams move quickly without worry of breaking compliance.
These policies can be created to affect the complete organization, folder(s) or project(s). Descendants of the targeted resource hierarchy node inherit the organization policy.
In order to define an organization policy, you choose a constraint, which is a particular type of restriction against either a Google Cloud service or a group of Google Cloud services. You configure that constraint with your desired restrictions.
Limit resource sharing based on domain.
Limit the usage of Identity and Access Management service accounts.
Restrict the physical location of newly created resources.
Disable service account creation
There are many more constraints that give you fine-grained control of your organization's resources. For more information, see the list of all Organization Policy Service constraints.
These are like IAM policies in AWS as each role contains a set of permissions.
However, unlike in AWS, there is no centralized repo of roles. Instead of that, resources give X access roles to Y principals, and the only way to find out who has access to a resource is to use the get-iam-policy method over that resource.
This could be a problem because this means that the only way to find out which permissions a principal has is to ask every resource who is it giving permissions to, and a user might not have permissions to get permissions from all resources.
There are three types of roles in IAM:
Basic/Primitive roles, which include the Owner, Editor, and Viewer roles that existed prior to the introduction of IAM.
Predefined roles, which provide granular access for a specific service and are managed by Google Cloud. There are a lot of predefined roles, you can see all of them with the privileges they have here.
Custom roles, which provide granular access according to a user-specified list of permissions.
There are thousands of permissions in GCP. In order to check if a role has a permissions you can search the permission here and see which roles have it.
You can also search here predefined roles offered by each product. Note that some roles cannot be attached to users and only to SAs because some permissions they contain. Moreover, note that permissions will only take effect if they are attached to the relevant service.
Or check if a custom role can use a specific permission in here.
GCP - IAM, Principals & Org Policies EnumIn GCP console there isn't any Users or Groups management, that is done in Google Workspace. Although you could synchronize a different identity provider in Google Workspace.
You can access Workspaces users and groups in https://admin.google.com.
MFA can be forced to Workspaces users, however, an attacker could use a token to access GCP via cli which won't be protected by MFA (it will be protected by MFA only when the user logins to generate it: gcloud auth login).
When an organisation is created several groups are strongly suggested to be created. If you manage any of them you might have compromised all or an important part of the organization:
Group
Function
gcp-organization-admins
(group or individual accounts required for checklist)
Administering any resource that belongs to the organization. Assign this role sparingly; org admins have access to all of your Google Cloud resources. Alternatively, because this function is highly privileged, consider using individual accounts instead of creating a group.
gcp-network-admins
(required for checklist)
Creating networks, subnets, firewall rules, and network devices such as Cloud Router, Cloud VPN, and cloud load balancers.
gcp-billing-admins
(required for checklist)
Setting up billing accounts and monitoring their usage.
gcp-developers
(required for checklist)
Designing, coding, and testing applications.
gcp-security-admins
Establishing and managing security policies for the entire organization, including access management and organization constraint policies. See the Google Cloud security foundations guide for more information about planning your Google Cloud security infrastructure.
gcp-devops
Creating or managing end-to-end pipelines that support continuous integration and delivery, monitoring, and system provisioning.
gcp-logging-admins
gcp-logging-viewers
gcp-monitor-admins
gcp-billing-viewer
(no longer by default)
Monitoring the spend on projects. Typical members are part of the finance team.
gcp-platform-viewer
(no longer by default)
Reviewing resource information across the Google Cloud organization.
gcp-security-reviewer
(no longer by default)
Reviewing cloud security.
gcp-network-viewer
(no longer by default)
Reviewing network configurations.
grp-gcp-audit-viewer
(no longer by default)
Viewing audit logs.
gcp-scc-admin
(no longer by default)
Administering Security Command Center.
gcp-secrets-admin
(no longer by default)
Managing secrets in Secret Manager.
Enforce strong passwords
Between 8 and 100 characters
No reuse
No expiration
If people is accessing Workspace through a third party provider, these requirements aren't applied.
These are the principals that resources can have attached and access to interact easily with GCP. For example, it's possible to access the auth token of a Service Account attached to a VM in the metadata.
It is possible to encounter some conflicts when using both IAM and access scopes. For example, your service account may have the IAM role of compute.instanceAdmin but the instance you've breached has been crippled with the scope limitation of https://www.googleapis.com/auth/compute.readonly. This would prevent you from making any changes using the OAuth token that's automatically assigned to your instance.
It's similar to IAM roles from AWS. But not like in AWS, any service account can be attached to any service (it doesn't need to allow it via a policy).
Several of the service accounts that you will find are actually automatically generated by GCP when you start using a service, like:
However, it's also possible to create and attach to resources custom service accounts, which will look like this:
There are 2 main ways to access GCP as a service account:
Via OAuth tokens: These are tokens that you will get from places like metadata endpoints or stealing http requests and they are limited by the access scopes.
Keys: These are public and private key pairs that will allow you to sign requests as the service account and even generate OAuth tokens to perform actions as the service account. These keys are dangerous because they are more complicated to limit and control, that's why GCP recommend to not generate them.
Note that every-time a SA is created, GCP generates a key for the service account that the user cannot access (and won't be listed in the web application). According to this thread this key is used internally by GCP to give metadata endpoints access to generate the accesible OAuth tokens.
Access scope are attached to generated OAuth tokens to access the GCP API endpoints. They restrict the permissions of the OAuth token. This means that if a token belongs to an Owner of a resource but doesn't have the in the token scope to access that resource, the token cannot be used to (ab)use those privileges.
Google actually recommends that access scopes are not used and to rely totally on IAM. The web management portal actually enforces this, but access scopes can still be applied to instances using custom service accounts programmatically.
You can see what scopes are assigned by querying:
The previous scopes are the ones generated by default using gcloud to access data. This is because when you use gcloud you first create an OAuth token, and then use it to contact the endpoints.
The most important scope of those potentially is cloud-platform, which basically means that it's possible to access any service in GCP.
You can find a list of all the possible scopes in here.
If you have gcloud browser credentials, it's possible to obtain a token with other scopes, doing something like:
As defined by terraform in https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/google_project_iam using terraform with GCP there are different ways to grant a principal access over a resource:
Memberships: You set principals as members of roles without restrictions over the role or the principals. You can put a user as a member of a role and then put a group as a member of the same role and also set those principals (user and group) as member of other roles.
Bindings: Several principals can be binded to a role. Those principals can still be binded or be members of other roles. However, if a principal which isn’t binded to the role is set as member of a binded role, the next time the binding is applied, the membership will disappear.
Policies: A policy is authoritative, it indicates roles and principals and then, those principals cannot have more roles and those roles cannot have more principals unless that policy is modified (not even in other policies, bindings or memberships). Therefore, when a role or principal is specified in policy all its privileges are limited by that policy. Obviously, this can be bypassed in case the principal is given the option to modify the policy or privilege escalation permissions (like create a new principal and bind him a new role).
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