Configuring Network Policies to Restrict Pod Access
Network policies are designed by Kubernetes to restrict pod access. It is equivalent to a firewall at the application layer to enhance network security. The capabilities supported by network policies depend on the capabilities of the network add-ons of the cluster.
By default, if a namespace does not have any policy, pods in the namespace accept traffic from any source and send traffic to any destination.
Network policies are classified into the following types:
- namespaceSelector: selects particular namespaces for which all pods should be allowed as ingress sources or egress destinations.
- podSelector: selects particular pods in the same namespace as the network policy which should be allowed as ingress sources or egress destinations.
- IPBlock: selects particular IP blocks to allow as ingress sources or egress destinations. (Only egress rules support IPBlock.)
Notes and Constraints
- Only clusters that use the tunnel network model support network policies. Network policies are classified into the following types:
- Ingress: All versions support this type.
- Egress: The cluster must be of v1.23 or later.
- Network isolation is not supported for IPv6 addresses.
- If you upgrade a CCE cluster to a version that supports egress rules in in-place mode, the rules will not work because the node OS is not upgraded. In this case, reset the node.
Using Ingress Rules Through YAML
- Scenario 1: Use a network policy to limit access to a pod to only pods with specific labels.
Figure 1 podSelector
The pod labeled with role=db only permits access to its port 6379 from pods labeled with role=frontend. To do so, perform the following operations:
- Create the access-demo1.yaml file.
vim access-demo1.yaml
File content:
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: access-demo1 namespace: default spec: podSelector: # The rule takes effect for pods with the role=db label. matchLabels: role: db ingress: # This is an ingress rule. - from: - podSelector: # Only allow the access of the pods labeled with role=frontend. matchLabels: role: frontend ports: # Only TCP can be used to access port 6379. - protocol: TCP port: 6379
- Run the following command to create the network policy based on the access-demo1.yaml file:
kubectl apply -f access-demo1.yaml
Expected output:
networkpolicy.networking.k8s.io/access-demo1 created
- Create the access-demo1.yaml file.
- Scenario 2: Use a network policy to limit access to a pod to only pods in a specific namespace.
Figure 2 namespaceSelector
The pod labeled with role=db only permits access to its port 6379 from pods in the namespace labeled with project=myproject. To do so, perform the following operations:
- Create the access-demo2.yaml file.
vim access-demo2.yaml
File content:
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: access-demo2 spec: podSelector: # The rule takes effect for pods with the role=db label. matchLabels: role: db ingress: # This is an ingress rule. - from: - namespaceSelector: # Only allow the access of the pods in the namespace labeled with project=myproject. matchLabels: project: myproject ports: # Only TCP can be used to access port 6379. - protocol: TCP port: 6379
- Run the following command to create the network policy based on the access-demo2.yaml file:
kubectl apply -f access-demo2.yaml
Expected output:
networkpolicy.networking.k8s.io/access-demo2 created
- Create the access-demo2.yaml file.
Using Egress Rules Through YAML
Egress supports podSelector, namespaceSelector, and IPBlock.
Only clusters of v1.23 or later support egress rules.
- Scenario 1: Use a network policy to limit a pod's access to specific addresses.
Figure 3 IPBlock
The pod labeled with role=db only permits access to the 172.16.0.16/16 CIDR block, excluding 172.16.0.40/32 within it. To do so, perform the following operations:
- Create the access-demo3.yaml file.
vim access-demo2.yaml
File content:
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: access-demo3 namespace: default spec: policyTypes: # Must be specified for an egress rule. - Egress podSelector: # The rule takes effect for pods with the role=db label. matchLabels: role: db egress: # Egress rule - to: - ipBlock: cidr: 172.16.0.16/16 # Allow access to this CIDR block in the outbound direction. except: - 172.16.0.40/32 # Block access to this address in the CIDR block.
- Run the following command to create the network policy based on the access-demo3.yaml file:
kubectl apply -f access-demo3.yaml
Expected output:
networkpolicy.networking.k8s.io/access-demo3 created
- Create the access-demo3.yaml file.
- Scenario 2: Use a network policy to limit access to a pod to only pods with specific labels and this pod can only access specific pods.
Figure 4 Using both ingress and egress
The pod labeled with role=db only permits access to its port 6379 from pods labeled with role=frontend, and this pod can only access the pods labeled with role=web. You can use the same rule to configure both ingress and egress in a network policy. To do so, perform the following operations:
- Create the access-demo4.yaml file.
vim access-demo2.yaml
File content:
apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: access-demo4 namespace: default spec: policyTypes: - Ingress - Egress podSelector: # The rule takes effect for pods with the role=db label. matchLabels: role: db ingress: # This is an ingress rule. - from: - podSelector: # Only allow the access of the pods labeled with role=frontend. matchLabels: role: frontend ports: # Only TCP can be used to access port 6379. - protocol: TCP port: 6379 egress: # Egress rule - to: - podSelector: # Only pods with the role=web label can be accessed. matchLabels: role: web
- Run the following command to create the network policy based on the access-demo4.yaml file:
kubectl apply -f access-demo4.yaml
Expected output:
networkpolicy.networking.k8s.io/access-demo4 created
- Create the access-demo4.yaml file.
Creating a Network Policy on the Console
- Log in to the CCE console and click the cluster name to access the cluster console.
- Choose Policies in the navigation pane, click the Network Policies tab, and click Create Network Policy in the upper right corner.
- Policy Name: Specify a network policy name.
- Namespace: Select a namespace in which the network policy is applied.
- Selector: Enter a label, select the pod to be associated, and click Add. You can also click Reference Workload Label to use the label of an existing workload.
- Inbound Rule: Click to add an inbound rule. For details about parameter settings, see Table 1.
Table 1 Adding an inbound rule Parameter
Description
Protocol & Port
Select the protocol type and port. Currently, TCP and UDP are supported.
Source Namespace
Select a namespace whose objects can be accessed. If this parameter is not specified, the object belongs to the same namespace as the current policy.
Source Pod Label
Allow accessing the pods with this label. If this parameter is not specified, all pods in the namespace can be accessed.
- Outbound Rule: Click to add an outbound rule. For details about parameter settings, see Table 1.
Table 2 Adding an outbound rule Parameter
Description
Protocol & Port
Select the protocol type and port. Currently, TCP and UDP are supported. If this parameter is not specified, the protocol type is not limited.
Destination CIDR Block
Allows requests to be routed to a specified CIDR block (and not to the exception CIDR blocks). Separate the destination and exception CIDR blocks by vertical bars (|), and separate multiple exception CIDR blocks by commas (,). For example, 172.17.0.0/16|172.17.1.0/24,172.17.2.0/24 indicates that 172.17.0.0/16 is accessible, but not for 172.17.1.0/24 and 172.17.2.0/24.
Destination Namespace
Select a namespace whose objects can be accessed. If this parameter is not specified, the object belongs to the same namespace as the current policy.
Destination Pod Label
Allow accessing the pods with this label. If this parameter is not specified, all pods in the namespace can be accessed.
- Click OK.
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