Access Context Manager Overview

This document provides a general overview of the Access Context Manager service and its functions. Google Cloud organization administrators can use Access Context Manager to define fine-grained, attribute-based access control for projects and resources in Google Cloud. As an administrator, you first define an access policy, which is an organization-wide container for access levels and service perimeters.

Access levels describe the requirements for requests to be honored. Examples include the following:

  • Device type and operating system
  • IP address
  • User identity

Service perimeters define sandboxes of resources, which can freely exchange data within the perimeter but are not allowed to export data outside of the perimeter. Access Context Manager isn't responsible for policy enforcement. Rather, Access Context Manager is designed to define specific rules or context. Policy is configured and enforced across various points, such as VPC Service Controls. You can read more about these services in their respective user guides.

You can configure and enforce Access Context Manager policies across the following Chrome Enterprise Premium solution components:

Benefits

Many companies rely on a perimeter security model such as a firewall to secure internal resources. A perimeter security model is heavily guarded with a single point of entry and exit. Anything located outside is considered dangerous . Anything inside is trusted.

Firewalls and the perimeter security model work well if there is a precise boundary around specific users and services. However, if a workforce is mobile, the variety of devices increases as users bring their own devices (BYOD) and utilize cloud-based services. This scenario results in additional attack vectors that aren't considered by the perimeter model. Given this, the perimeter is no longer only the physical location of the enterprise, and what lies inside cannot be assumed as safe.

You can use Access Context Manager to reduce the size of the privileged network and move to a model where endpoints don't carry ambient authority based on the network. Instead, you can grant access based on the context of the request, such as device type, user identity, and more, while still checking for corporate network access when necessary.

Access Context Manager is an integral part of the BeyondCorp effort at Google. For more information, see BeyondCorp.

Access policies

An access policy is a container for all of your Access Context Manager resources, such as access levels and service perimeters.

You can create an access policy in the context of an organization and use the organization-level access policy anywhere in your organization. To delegate administration of an access policy, you can create a scoped access policy and set the scope of the policy at the folder or project level. The delegated administrator to whom the scoped policy is assigned can manage only the scoped access policy and not the organization-level access policy.

An access policy is versioned using an etag. You can use etag to target changes to your access policy, such as modifications to access levels or to a specific version of the policy. If multiple sources change your access policy, using the etag field for the gcloud command-line tool and API calls helps prevent unintended overwrites and conflicts.

To learn how to create access policies, see Creating an access policy.

Access levels

Access levels are used for permitting access to resources based on contextual information about the request. Using access levels, you can start to organize tiers of trust. For example, you might create an access level called High_Level that will permit requests from a small group of highly-privileged individuals. You might also identify a more general group to trust, such as an IP range that you want to permit requests from. In that case, you might create an access level called Medium_Level to permit those requests.

After you've defined access levels, enforcement services can use them to determine whether to honor a request. For example, you might specify that, while many resources are available to Medium_Trust, certain more sensitive resources require the High_Trust level. These checks are applied in addition to standard IAM policy.

Access levels are customizable; the High_Trust and Medium_Trust access levels are examples. You can specify multiple access levels as part of an access policy.

Access Context Manager provides two ways to define access levels:

  • A basic access level consists of a collection of conditions that are used to test requests. Conditions can be defined as a group of attributes that you want to test, such as device type, IP address, or user identity. The attributes are combined as either an AND operation (all must be true) or a NOR operation (none must be true) to determine whether the condition is met.

  • Custom access levels are created using a subset of Common Expression Language. In addition to the request context used for basic access levels, you can also use custom access levels to permit requests based on data from third-party services. For more information, see Custom Access Levels.

When nesting access levels and when combining all logic, keep in mind that, if any of the operands of the boolean operators AND (&&) and OR (||) uniquely determines the result, the other operand might or might not be evaluated. In addition, if that evaluation produces a runtime error, it is ignored. For example, in the following expression, the evaluation of origin.region_code fails, but the levels.ip_check evaluation succeeds. Because at least one of the checks is successful, the overall condition, which is combined by OR, becomes true, and access is GRANTED.

!(origin.region_code in ['RU', 'BY', 'UA']) -> FAILED  // levels.regions_check

inIpRange(origin.ip, ['205.220.128.0/23']) -> GRANTED  // levels.ip_check

!(origin.region_code in ['RU', 'BY', 'UA']) || inIpRange(origin.ip, ['205.220.128.0/23']) -> GRANTED

levels.regions_check || levels.ip_check -> GRANTED

IP address

You can grant an access level based on the IP address of the originating request. The range of IPs to allow is specified in the form of a Classless Inter-Domain Routing (CIDR) block, which allows for fine-grained control over the IPs allowed.

A single access level can contain multiple IP ranges.

To learn how to create an access level that only allows access to a specified range of IP addresses such as those within a single corporate network, see Creating an Access Level for Corporate Network Access.

Device type

Access Context Manager uses Endpoint Verification to gather information about user devices such as the operating system, device type, or version. You can grant an access level based on this data. For example, you can grant a more permissive access level to devices that run the latest version of the primary operating system deployed at your company.

To learn how to grant an access level based on such device attributes, see Limit access by device type.

User identity

In some scenarios, you might want to grant an access level to specific entities. In these scenarios, the identity of the caller determines whether the condition is met. This scenario is often used together with Service Accounts and VPC Service Controls. For example, you can use this scenario to enable a Cloud Function to access data protected by VPC Service Controls.

You can create and manage identity-only access levels with the gcloud command-line tool, but not with the Google Cloud console.

To get started with creating a basic access level, see Create an access level for Access Context Manager.

For information about creating an access level that allows access based on the context of a request, see Create a custom access level.

Combining conditions

A single access level can contain multiple conditions. The conditions can be evaluated using either the AND or OR operator. You can specify the mode when creating or updating an access level.

The AND case is the stricter and default option. This option only grants the Access Level if all conditions pass. For example, you might require a request come from within the corporate network and from a device that runs a latest version of an operating system.

OR is a less restrictive option. This option only requires one of many conditions to be true. This is sometimes valuable when dealing with user identities—for example, to exclude specific entities (such as Service Accounts) from the normal requirements.

Nesting conditions

Conditions can be nested such that one condition depends on another condition. For example, if you have the two access levels of "Medium" and "High" trust, you can set the requirements for "High" to require "Medium," in addition to other conditions.

Nesting conditions can make managing access levels more convenient. For example, imagine your most permissive access level contains a minimum operating system version, and you set your more restrictive levels to depend on it. If you update the minimum version in the future, you only have to update a single condition, rather than every access level in the policy.

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