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DevSecOps

What is an Open Policy Agent OPA? Tutorial by Wallarm

What is an Open Policy Agent OPA? Tutorial by Wallarm

By 2023, the majority of applications will be built specifically for the cloud. The importance and complexity of access control increase as businesses move from static on-premises settings to flexible cloud-based ones. In order to install safety barriers on their platform, many people find that OPA is the most convenient option. Are you curious? Let's delve even further into OPA meaning and its subject.

Learning Objectives

What is an Open Policy Agent OPA?

As a free and open-source engine, Open Policy Agent Kubernetes facilitates the declarative coding of policies and their subsequent application in a decision-making context. With Rego, a language built into the system, you may create uniform rules that can be applied across a wide variety of services.

Many other applications exist for OPA, such as:

  • Validation of REST API endpoints for access permissions.
  • Allowing or refusing modifications to Terraform depending on compliance or safety regulations.
  • Applying customized access control rules to software.
  • Validating API security requests with the use of Kubernetes Admission Controllers.

What problems can the OPA solve?

OPA enables the creation of a single set of configuration rules and their automatic deployment over a vast environment by permitting engineers to develop policy-as-code files that define how a resource should act. Policy-as-code describes a method that does away with the need to manually configure and audit each resource.

It's not a novel concept to use code-based policies to set up IT infrastructure. This is exactly what infrastructure-as-code tools like Terraform, Ansible, and AWS CloudFormation have been doing for quite some time. Methods similar to these have been used to manage cloud-based identification and access management and to enforce data security policies.

Whereas other policy-as-code tools might only be able to configure one specific kind of IT resource, OPA is capable of configuring almost any kind of IT resource (like cloud infrastructure or cloud access-control rules). If you're using Kubernetes and need a centralized platform for managing API calls, controlling resource provisioning in the cloud, or even configuring a firewall, OPA is your best bet.

Review of the OPA's work

With OPA, a centralized policy manager is in charge of maintaining service-level policies rather than each individual application. The foundational principle of OPA is that policy decisions should be kept distinct from policy execution at all times.

Requirements for Compliance with OPA Policy

Depending on the nature of the service being provided, a unique set of OPA policy guidelines can be developed, like as:

  • Authorization and access at the user level
  • Setup of Infrastructure
  • Examination and auditing
  • Solutions for application-level authorization
  • Administration of national policies

When it comes to policy management, OPS has you covered with its centralized service that is accessible via RESTful APIs using JSON over HTTP. OPA operates in tandem with the application services. When a service has to resolve a policy issue, it will send a request to the appropriate OPA API, wait for a response, and then act in accordance with the policy's directives.

You can technically run OPA as a daemon, a container, or a library on your operating system. Policy and service data are both kept in memory on the relevant host, which is a key design element of OPA Kubernetes. Policy requests are processed immediately because OPA is physically located on the same server as the service provider.

Open Policy Agent Example 
Open Policy Agent Example 

Open Policy Agent Example 

Due to the importance of labels, it is crucial to implement safeguards against their manipulation by unintended users. Avoiding manual label entry is also recommended, as it is prone to human error, can compromise safety, and creates operational headaches.

OPA is easier to grasp in practice when open policy agent examples are provided. One way in which OPA can be utilized to beef up Kubernetes protection is demonstrated in the example given below:

package kubernetes.validating.existence
 
deny[msg] {
	not input.request.object.metadata.labels.department
	msg := "Every resource must have a department label"
}
 
deny[msg] {
	value := input.request.object.metadata.labels.department
	not startswith(value, "cccode-")
	msg := sprintf("Department code must start with `dcode-`; found `%v`", [value])
}

What is a Rego?

All OPA regulations are written in Rego (pronounced "ray-go"), a declarative programming language. It is designed specifically for expressing rules in relational databases. See the Policy Language docs for more information on Rego.

The data log, a popular query language that has been around for decades, served as inspiration for Rego. Rego is an expansion of the info log that adds support for structured document representations like JSON.

Statements about OPA data can be made using Rego queries. Policies can be defined using these queries, which can then be used to enumerate instances of data that do not conform to the normative state of the system.

How To Manage and Control OPA?

To further reduce latency, the creators of OPA determined that all policy data should be stored in memory. This assures that OPA will not query another service in order to obtain the data. To interact with OPA, you have a set of APIs with varying purposes:

  • Bundle service API: This API is used to send policy data to OPA. OPA continually monitors the Bundle service API in search of updated policy versions. Once located, it retrieves and applies the latest version.
  • Status service API: used to determine the service's status. It displays the current, active policy version on OPA.
  • Decision log service API: OPA logs every policy decision it makes. Later, it transmits these logs in batches to the log service API. This is especially helpful for auditing and troubleshooting.
  • Tools for creating, testing, and debugging policies: a set of command-line tools such as an opa test, run, checks, and so on. A VS Code plugin is also available to facilitate development.

OPA and Cloud Native Environment

Native cloud environments have many moving parts. There are numerous parts that must be set up, taken down, updated, monitored, and protected. OPA can help your business because it has the power to enforce regulations.

OPA can aid you in the following essential cloud-native endeavors:

  • Application authorization - OPA employs a declarative policy language that enables the formulation and enforcement of rules. When you enable this function, you gain access to a full suite of tools for incorporating policies into your applications. The end-user’s policy contributions can be accepted if you provide them with the appropriate rights.
  • Kubernetes admission control — Kubernetes includes a feature that enables the enforcement of admission control policies. The OPA can assist you in enhancing these fundamental capabilities. Implementing OPA as a dynamic admission controller is essential for this. Then, using OPA, you can annotate your resources with precise information, inject pods with sidecar containers, and more.
  • Service mesh authorization—OPA can benefit you manage and control service mesh architectures by helping you regulate and control them. Open Privilege Administration (OPA) allows you to incorporate authorization policies into your service mesh without any additional steps. The ability to restrict horizontal communication within a microservice open policy agent architecture is useful for maintaining compliance.

Use of the OPA in the Kuburnets

Kubernetes Ingress allows you to expose or deny particular services. This could harm:

  • Administrators mistakenly expose services to the Internet using ingress settings.
  • Excessive Ingress permissions can force Kubernetes to spin up many load balancers, raising cloud expenses.
  • Incorrect Ingress configuration might cause new workloads with the same hostname as current workloads to unintentionally take over traffic, disrupting service and exposing sensitive data.
  • A sample OPA policy prevents a new host from using an existing Ingress host.

Using OPA to Secure Kubernetes Ingress

The OPA policy below prevents new hosts from using the same Ingress host as existing hosts.

package kubernetes.validating.ingress
 
deny[msg] {
	is_ingress
	input_host := input.request.object.spec.rules[_].host
    some other_ns, other_name
    other_host :=
    data.kubernetes.ingresses[other_ns][other_name].spec.rules[_].host
	[input_ns, input_name] != [other_ns, other_name]
 
	input_host == other_host
 
	msg := sprintf("Ingress host conflicts with ingress %v/%v", [other_ns, other_name])
}
 
input_ns = input.request.object.metadata.namespace
 
input_name = input.request.object.metadata.name
 
is_ingress {
	input.request.kind.kind == "Ingress"
	input.request.kind.group == "extensions"
	input.request.kind.version == "v1beta1"
}

Conclusion

The identity space, which includes authentication, authorization, and audit, is far more than just OPA. If the current trend is any indication, OPA maintainers are paying attention to the wants and needs of the developer community to fuel future innovation. To that end, we'll be developing several brand-new language features to facilitate both the development and maintenance of policies.

Despite the current absence of a dedicated policy marketplace, it is anticipated that open shared policy libraries and standardized approaches to policy exchange would proliferate in the near future.

OPA is expected to have a breakout year in the enterprise in 2023, according to experts in the containers and distributed systems field, who also anticipate that OPA will be used in an increasing number of use cases.

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