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Version: 0.18.0

Weave policy profile Enterprise

Weave Policy Profile

Overview​

Weave policy profile provides policies to automate the enforcement of best practice and conventions. It ensures the compliance of workloads through the use of a policy agent that provides an admission controller webhook that stops violating resources from deploying to a cluster and runs a daily audit that reports violating resources already deployed.

Policy Sources​

Policies are provided in the profile as Custom Resources. The agent reads from the policies deployed on the cluster and runs them during each admission request or when auditing a resource.

Policies are hosted in a policy library which is usually a git repository. They are fetched in the profile through the use of kustomize.toolkit.fluxcd.io.Kustomization, that deploys the policies to the cluster.

By default all policies in the specified path would be deployed in order to specify which policies should be deployed in a library, a kustomize.config.k8s.io.Kustomization file should be defined in the repository.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources: # specifies the path to each required policy 
  - policies/ControllerContainerAllowingPrivilegeEscalation/policy.yaml
  - policies/ControllerContainerRunningAsRoot/policy.yaml
  - policies/ControllerReadOnlyFileSystem/policy.yaml

The profile then needs to be configured with the necessary config to be able to reach the repository that is acting as a policy library.

policySource:
  enabled: true
  url: URL of the repo where your policies exist
  tag: tag name on the policies repo
  path: Path to the policies dir - or a kustomization.yaml that selects some policies - in the repo
  secretRef (if the repo is private): Name of the K8s secret with private repo credentials (leave empty if the repo is public)

There is the option of referencing an existing policy library source instead of creating a new one.

policySource:
  enabled: true
  sourceRef:
    kind: Kind of the existing source
    name: Name of the policy library source
    namespace: Namespace where the source exists

Admission Controller Setup​

To enable admission control:

policy-agent:
  config:
    admission:
      enabled: true

Enabling admission controller requires certificates for secure communication with the webhook client and the admission server. The best way to achieve this is by installing cert manager and then configuring the profile as follows:

policy-agent:
  useCertManager: true

There is the option of providing previously generated certificates although it is not recommended and it is up to the user to manage it:

policy-agent:
  certificate: "---" # admission server certificate
  key: "---" # admission server private key
  caCertificate: "---" # CA bundle to validate the webhook server, used by the client

If the agent webhook could not be reached or the request failed to complete, the corresponding request would be refused. To change that behavior and accepts the request in cases of failure, this needs to be set:

policy-agent:
  failurePolicy: Ignore

Audit​

Audit functionality provide a full scan on the cluster(s) and report back policy violations. This usually is used for policy violations reporting, and Compliance posture analysis against known benchmarks like PCI DSS, CIS, .etc.

To enable audit functionality:

policy-agent:
  config:
    audit:
      enabled: true
      interval: 24 # configuring the frequent of audit operations running in hours (default is 24 hour)

Audit will be performed when the agent starts and then at an interval of your choice in hours (default is 24 hour). The results from that sink would be published by the registered sinks.

Policy Sets​

Policy set is a custom resource that gives more control over which policies to be used in each scenario. There are cases in which certain policies are required to be observed but denying the requests of violating objects would be disruptive. Policy set allows defining additional filters for each scenario: Audit and Admission so it is possible to report violations on certain policies without the need of blocking the deployments if certain policies are not as critical as others.

Policy set should also be hosted on the policy library. The following definition defines which specific policies should be used using policy names:

apiVersion: pac.weave.works/v2beta1
kind: PolicySet
metadata:
    name: admission-policy-set
spec:
    id: admission-policy-set
    name: admission-policy-set
    filters:
      ids:
        - weave.policies.containers-running-with-privilege-escalation
        - weave.policies.containers-read-only-root-filesystem

To make use of this policy set in the profile:

policy-agent:
  config: 
    admission:
      policySet: admission-policy-set # name of policy set to be used for admission
    audit: 
      policySet: audit-policy-set # name of policy set to be used for audit

Policy Validation Sinks​

When validating a resource a validation object is generated that contains information about the status of that validation and metadata about the resource and policy involved. These objects should be exported to be visible for users as a critical part of the audit flow, but can also be useful as logs for the admission scenario.

By default the agent only writes policy validation that are violating a certain policy when performing an audit, to write compliance results as well, the following needs to be specified in the profile:

policy-agent:
  config:
    audit:
      writeCompliance: true

The agent profile supports multiple methods for different scenarios either Admission or Audit to expose this data and multiple can be used at the same time:

The results would be dumped into a text file in logs directory in the agent container as a json string. It is important to note that this file would not be persistent and would be deleted upon pod restart, so generally this approach is not recommended for production environment.

To enable writing to a text file in audit scenario:

policy-agent:
  config:
    audit:
      sinks:
        fileSystemSink:
          fileName: "file.json"

To enable writing to a text file in admission scenario:

policy-agent:
  config:
    admission:
      sinks:
        fileSystemSink:
          fileName: "file.json"

It is possible to make the file persistent, this assumes that there is a PersistentVolume already configured on the cluster.

policy-agent:
  persistence:
    enabled: false # specifies whether to use persistence or not
    claimStorage: 1Gi # claim size
    storageClassName: standard # k8s StorageClass name

Policy Validation​

Policy validation object contains all the necessary information to give the user a clear idea on what caused it. It is the result of validating an entity against a policy.

id: string # identifier for the violation
account_id: string # organization identifier
cluster_id: string # cluster identifier
policy: object # contains related policy data
entity: object # contains related resource data
status: string # Violation or Compliance
message: string # message that summarizes the policy validation
type: string # Admission or Audit
trigger: string # what triggered the validation, create request or initial audit,..
created_at: string # time that the validation occurred in