k8s安全05--配置网络策略 NetworkPolicy

1 介绍

k8s安全04–kube-apiserver 安全配置 已经介绍了kube-apiserver 的常见安全配置，本文接上文继续介绍k8s的网络安策略，并使用两个案例加以说明，后续会在本文持续更新网络策略相关的案例和注意事项、

2 案例

2.1 案例1

1.1 创建 ns 和 pod

$ kubectl create ns dev-ns
$ kubectl create ns prod-a
$ kubectl create ns prod-b

vim netpods.yaml
---
apiVersion: v1
kind: Pod
metadata:
  name: devapp
  namespace: dev-ns
  labels:
    app: devapp
    user: bob
spec:
  containers:
  - name: ubuntu
    image: ubuntu:20.04
    command: ["/bin/sleep", "3650d"]
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
---
apiVersion: v1
kind: Pod
metadata:
  name: frontend
  namespace: prod-a
  labels:
    app: front
    user: tim
spec:
  containers:
  - name: frontend
    image: nginx:1.19.6
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
---
apiVersion: v1
kind: Pod
metadata:
  name: backend
  namespace: prod-b
  labels:
    app: back
    user: tim
spec:
  containers:
  - name: backend
    image: nginx:1.19.6
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: devapp
    user: bob
  name: devapp
  namespace: dev-ns
spec:
  ports:
  - port: 80
    name: web
    protocol: TCP
    targetPort: 80
  - port: 22
    name: ssh
    protocol: TCP
    targetPort: 22
  selector:
    app: devapp
    user: bob
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: front
    user: tim
  name: frontend
  namespace: prod-a
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: front
    user: tim
  sessionAffinity: None
  type: NodePort
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: back
    user: tim
  name: backend
  namespace: prod-b
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: back
    user: tim
  sessionAffinity: None
  type: ClusterIP

$ kubectl apply -f netpods.yaml

1.2 查看pod，svc 信息

$ kubectl get pod,svc -A |grep -v kube-system|grep -v lens-metrics
NAMESPACE      NAME                                           READY   STATUS    RESTARTS          AGE
dev-ns         pod/devapp                                     1/1     Running   0                 12m
prod-a         pod/frontend                                   1/1     Running   0                 10m
prod-b         pod/backend                                    1/1     Running   0                 10m

NAMESPACE      NAME                         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                  AGE
default        service/kubernetes           ClusterIP   10.96.0.1       <none>        443/TCP                  91d
dev-ns         service/devapp               ClusterIP   10.98.181.135   <none>        80/TCP,22/TCP            12m
prod-a         service/frontend             NodePort    10.99.102.196   <none>        80:30119/TCP             12m
prod-b         service/backend              ClusterIP   10.105.19.195   <none>        80/TCP                   12m

1.3 测试网络联通性

$ kubectl -n dev-ns exec -it devapp -- bash
# apt-get update; apt-get install iputils-ping netcat ssh curl iproute2 -y

# curl frontend.prod-a.svc.cluster.local
# curl backend.prod-b.svc.cluster.local

# ping -c3 www.linux.com
# ping -c3 frontend.prod-a.svc.cluster.local
# ping -c3 backend.prod-a.svc.cluster.local

可访问 frontend
在这里插入图片描述
可访问 backend
在这里插入图片描述
可ping www.linux.com
不可 ping -c3 frontend.prod-a.svc.cluster.local,backend.prod-a.svc.cluster.local
在这里插入图片描述

1.4 在集群外部通过NodePort 访问服务

$ curl kmaster:30119

在这里插入图片描述

1.5 创建网络策略，prod-a 拒绝任何访问

$ vim denyall.yaml 
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: prod-deny-all
  namespace: prod-a
spec:
  podSelector: {}
  policyTypes:
  - Ingress 

$ kubectl apply -f denyall.yaml
networkpolicy.networking.k8s.io/prod-deny-all created

1.6 测试网络策略

从 dev-ns 访问

$ kubectl -n dev-ns exec -it devapp -- bash
# curl frontend.prod-a.svc.cluster.local
# curl backend.prod-b.svc.cluster.local
如下图，无法访问prod-a ns的服务，但是可以正常访问prod-b ns的服务
$ curl kmaster:30119 #集群外部访问也失败

在这里插入图片描述
从 prod-a 访问

$ kubectl -n prod-a exec -it frontend -- bash
# curl backend.prod-b.svc.cluster.local
# ping -c3 www.linux.com
# curl frontend.prod-a.svc.cluster.local
从prod-a 访问其它ns 或者域名，都可以正常访问；
从prod-a 访问它自己失败

1.7 创建网络策略, 允许标签为 app: front 的pod 访问

vim allowinternet.yaml 
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: internet-access
  namespace: prod-a
spec:
  podSelector:
    matchLabels:
      app: front
  policyTypes:
  - Ingress
  ingress:
  - {}

$ kubectl apply -f allowinternet.yaml 
networkpolicy.networking.k8s.io/internet-access created

1.8 测试网络策略

$ kubectl -n prod-a exec -it frontend -- bash
# curl frontend.prod-a.svc.cluster.local

$ curl kmaster:30119

$ kubectl -n prod-b exec -it backend -- bash
# curl frontend.prod-a.svc.cluster.local
此时在prod-a prod-b 集群外部，都可以正常访问frontend服务

2.2 案例2

在prod-a 命名空间内，创建名为pod-access的NetworkPolicy作用于名为 frontend 的Pod，只允许命名空间为testing的Pod或者在任何命名空间内有environment:staging标签的Pod来访问.

2.1 创建ns 和 pod

创建 ns

vim ns.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev-ns
  labels:
    name: testing
spec: {}
status: {}
---
apiVersion: v1
kind: Namespace
metadata:
  name: prod-a
spec: {}
status: {}

$ kubectl apply -f ns.yaml 
namespace/dev-ns created
namespace/prod-a created

$ kubectl get ns -A --show-labels|grep -E 'dev-ns|prod-a|default'
default           Active   92d   kubernetes.io/metadata.name=default
dev-ns            Active   21h   kubernetes.io/metadata.name=dev-ns,name=testing
prod-a            Active   21h   kubernetes.io/metadata.name=prod-a
只有dev-ns 有标签 name:testing

创建 base pod

vim base.yaml
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu01
  namespace: default
spec:
  containers:
  - name: ubuntu01
    image: ubuntu:20.04
    command: ["sleep", "infinity"]
    imagePullPolicy: IfNotPresent
---
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu02
  namespace: default
  labels:
    environment: staging
spec:
  containers:
  - name: ubuntu02
    image: ubuntu:20.04
    command: ["sleep", "infinity"]
    imagePullPolicy: IfNotPresent
---
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu03
  namespace: dev-ns
  labels:
    app: dev
spec:
  containers:
  - name: ubuntu03
    image: ubuntu:20.04
    command: ["sleep", "infinity"]
    imagePullPolicy: IfNotPresent

$ kubectl apply -f base.yaml

创建 nginx pod

vim netpods.yaml
apiVersion: v1
kind: Pod
metadata:
  name: frontend
  namespace: prod-a
  labels:
    app: front
    environment: staging
spec:
  containers:
  - name: frontend
    image: nginx:1.19.6
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: front
  name: frontend
  namespace: prod-a
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: front
  sessionAffinity: None
  type: NodePort
---
apiVersion: v1
kind: Pod
metadata:
  name: backend
  namespace: prod-a
  labels:
    app: back
spec:
  containers:
  - name: backend
    image: nginx:1.19.6
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: back
  name: backend
  namespace: prod-a
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: back
  sessionAffinity: None
  type: NodePort

$ kubectl apply -f netpods.yaml

查看ns，pod，svc 信息

$ kubectl get pod -A --show-labels|grep -E 'ubuntu|frontend|backend'
default        ubuntu01                                   1/1     Running   0               31m     <none>
default        ubuntu02                                   1/1     Running   0               31m     environment=staging
dev-ns         ubuntu03                                   1/1     Running   0               15m     app=dev
prod-a         backend                                    1/1     Running   0               43m     app=back
prod-a         frontend                                   1/1     Running   0               21h     app=front,environment=staging

$ kubectl get svc -A --show-labels|grep -E 'frontend|backend'
prod-a         backend              NodePort    10.110.111.176   <none>        80:32521/TCP             43m   app=back
prod-a         frontend             NodePort    10.100.182.62    <none>        80:31671/TCP             21h   app=front

2.2 创建网络策略

vim np.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: pod-access
  namespace: prod-a
spec:
  podSelector:
    matchLabels:
       environment: staging
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: testing
  - from:
    - namespaceSelector:
        matchLabels: {}
      podSelector:
        matchLabels:
           environment: staging

$ kubectl apply -f np.yaml 
networkpolicy.networking.k8s.io/pod-access created

2.3 测试网络策略

2.3.1 集群外部访问， 访问frontend 异常，访问backend 正常
$ curl kmaster:31671 #前端
$ curl kmaster:32521 #后端

访问前端异常
在这里插入图片描述
访问后端ok
在这里插入图片描述

2.3.2 dev-ns 内部分别访问frontend、backend
$ kubectl -n dev-ns exec -it ubuntu03 -- bash
# curl frontend.prod-a.svc.cluster.local
# curl backend.prod-a.svc.cluster.local

访问前端正常
在这里插入图片描述
访问后端正常
在这里插入图片描述

2.3.3 default 内部ubuntu01(没有打标签)分别访问前后端
$ kubectl -n default exec -it ubuntu01 -- bash
# curl frontend.prod-a.svc.cluster.local
# curl backend.prod-a.svc.cluster.local

访问前端失败
在这里插入图片描述
访问后端成功
在这里插入图片描述

2.3.4 default 内部ubuntu02(打标签environment=staging)分别访问前后端
$ kubectl -n default exec -it ubuntu02 -- bash
# curl frontend.prod-a.svc.cluster.local
# curl backend.prod-a.svc.cluster.local

访问前端成功
在这里插入图片描述
访问后端成功
在这里插入图片描述

3 注意事项

3.1 常见Selector功能区别

case 1: spec 下的 podSelector，其作用是确定哪些pod受到该网络策略的限制

spec:
  podSelector

spec:
  ingress:
  - from:
    - namespaceSelector:

case 2: spec.ingress.from 下的 podSelector，其作用为满足该标签的pod能访问 case 1 中pod

spec:
  ingress:
  - from:
    - podSelector:

case 3: spec.ingress.from 下的 namespaceSelector，其作用为有这个标签的ns下的pod能访问 case 1 中pod

spec:
  ingress:
  - from:
    - namespaceSelector:

case 4 spec.ingress.from 下同时有 namespaceSelector 和 podSelector，其作用为 满足 namespaceSelector 标签的 ns 且该ns 中pod的标签满足 podSelector 的pod 能访问 case 1 中pod

spec:
  ingress:
  - from:
    - namespaceSelector:
      podSelector:

3.2 拒绝和允许一个ns的ingress访问

vim deny.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: deny-all-ingress
  namespace: prod-a
spec:
  podSelector: {}
  ingress:
  policyTypes:
  - Ingress

vim allow.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-all-ingress
  namespace: prod-a
spec:
  podSelector: {}
  ingress:
  - {}
  policyTypes:
  - Ingress

两者区别，
allow.yaml 的 spec.ingress: 下面多了个 - {}

4 说明

Concepts->Services, Load Balancing, and Networking->Network Policies

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