kyvernoVSgateKeeper

kyverno VS gateKeeper

概述

这两组开源工具都是是基于kubernetes 的webhook机制，支持validatingwebhook和mutatingwebhook。整体思路上是一样的，都是针对资源的字段，如标签、镜像等来设置规则，在对kubernetes资源的控制范围和粒度上，二者可以看作是一样的。

kyverno

kyverno 的架构如下，它是基于kubernetes 资源的一种策略执行器，主要基于kubernetes资源的标签和spec字段制定规则，规则支持简单的条件判断，逻辑与、或、非。支持如下功能：

• 支持集群级别和命名空间级别的策略
• 支持审计日志功能
• 有一个官方的UI
• 支持kubernetes原生资源和CRD
• 支持如下规则类型：
  validate：规则校验，最常用的类型
  mutate：支持修改现有资源
  generate：支持生成新的资源
  verifyImages：校验镜像签名

例子

如下策略表示拒绝没有cluster-admin clusterRoles的用户删除带app.kubernetes.io/managed-by: kyverno 标签的对象

apiVersion: kyverno.io/v1kind: ClusterPolicymetadata:  name: deny-deletesspec:  validationFailureAction: enforce  background: false  rules:  - name: block-deletes-for-kyverno-resources    match:      resources:        selector:          matchLabels:            app.kubernetes.io/managed-by: kyverno    exclude:      clusterRoles:      - cluster-admin    validate:      message: "Deleting {{request.oldObject.kind}}/{{request.oldObject.metadata.name}} is not allowed"      deny:        conditions:        - key: "{{request.operation}}"          operator: In          value:          - DELETE

由于kyverno 建立在kubernetes之上，其策略决策和策略执行也是基于kubernetes的资源，因此也限制了其使用场景，如对接image registries, Active Directory/LDAP directories等第三方验证服务，而gatekeeper就可以支持就这些场景。

此外由于它使用类yaml的方式来表达策略的，因此其使用起来比较笨拙。

优点就是使用的配置比较简单，相比于gateKeeper来说入手比较简单，维护成本低。

gateKeeper

例子

gateKeeper的规则配置要分为两步，首先创建ConstraintTemplate，再创建constraint

首先需要创建一个模板ConstraintTemplate，下面模板用于要求所有资源中必须存在constraint 所要求的标签

apiVersion: templates.gatekeeper.sh/v1beta1kind: ConstraintTemplatemetadata:  name: k8srequiredlabelsspec:  crd:    spec:      names:        kind: K8sRequiredLabels      validation:        # Schema for the `parameters` field        openAPIV3Schema:          properties:            labels:              type: array              items: string  targets:    - target: admission.k8s.gatekeeper.sh      rego: |        package k8srequiredlabels        violation[{"msg": msg, "details": {"missing_labels": missing}}] {          provided := {label | input.review.object.metadata.labels[label]}          required := {label | label := input.parameters.labels[_]}          missing := required - provided          count(missing) > 0          msg := sprintf("you must provide labels: %v", [missing])        }

然后创建一个constraints，并指定上面的K8sRequiredLabels模板，要求所有命名空间资源中必须有gatekeeper标签

apiVersion: constraints.gatekeeper.sh/v1beta1kind: K8sRequiredLabelsmetadata:  name: ns-must-have-gkspec:  match:    kinds:      - apiGroups: [""]        kinds: ["Namespace"]  parameters:    labels: ["gatekeeper"]

对比表

Features/Capabilities	Gatekeeper	Kyverno
Validation	?	?
Mutation	?* beta	?
Generation	X	?
Policy as native resources	?	?
Metrics exposed	?	?
OpenAPI validation schema (kubectl explain)	X	?
High Availability	?	?*
API object lookup	?	?
CLI with test ability	?**	?
Policy audit ability	?	?
Self-service reports	X	?

* Alpha status

** Separate CLI

Community/Ecosystem	Gatekeeper	Kyverno
CNCF status	Graduated (OPA)	Sandbox
Partner ecosystem adoption*	?	?
GitHub status (stars, forks, releases, commits)	1,832, 349, 46, 630	1,063, 122, 82, 3,326
Community traction**	?	?
Policy sample library	?	?

* Not well defined. 相比Kyverno来说，Gatekeeper 的采纳意向更多,但具体不详.

** No objective measurement exists. 考虑到社区的存在时间，Gatekeeper 可能更具吸引力.

Meta/Misc	Gatekeeper	Kyverno
Programming required	?	X
Use outside Kubernetes	?	X
Birth (Age as of June 2021)	July 2017 (3 years, 11 months)	May 2019 (2 years, 1 month)
Origin company	Styra (OPA)	Nirmata
Documentation maturity	?*	?

* Not totally objective with direct comparison being difficult. Assessment made based on Gatekeeper project/functionality and not maturity level of Rego enablement materials/literature.

参考

• kubernetes-policy-comparison-opa-gatekeeper-vs-kyverno
• Kyverno 和 OPA/Gatkeeper 的一点对比
• kyverno policies
• gatekeeper-library