Encrypt in-cluster pod traffic

5 MINUTE READ

Big picture

Enable WireGuard to secure on-the-wire, in-cluster pod traffic in a Calico cluster.

Value

When this feature is enabled, Calico automatically creates and manages WireGuard tunnels between nodes providing transport-level security for on-the-wire, in-cluster pod traffic. WireGuard provides formally verified secure and performant tunnels without any specialized hardware. For a deep dive in to WireGuard implementation, see this whitepaper.

Features

This how-to guide uses the following Calico features:

  • Felix configuration resource with WireGuard configuration parameters

Before you begin…

The following platforms using only IPv4:

  • Kubernetes, on-premises
  • EKS using Calico CNI
  • EKS using AWS CNI
  • AKS using Azure CNI

Supported encryption

  • Host-to-host encryption for pod traffic
  • Encryption for direct node-to-node communication - supported only on managed clusters deployed on EKS and AKS

Required

  • On all nodes in the cluster that you want to participate in Calico encryption, verify that the operating system(s) on the nodes are installed with WireGuard.

    Note: Some node operating systems do not support Wireguard, or do not have it installed by default. Enabling Calico Wireguard encryption does not require all nodes to be installed with Wireguard. However, traffic to or from a node that does not have Wireguard installed, will not be encrypted.

  • IP addresses for every node in the cluster. This is required to establish secure tunnels between the nodes. Calico can automatically do this using IP autodetection methods.

How to

Install WireGuard

WireGuard is included in Linux 5.6+ kernels, and has been backported to earlier Linux kernels in some Linux distributions.

Install WireGuard on cluster nodes using instructions for your operating system. Note that you may need to reboot your nodes after installing WireGuard to make the kernel modules available on your system.

Use the following instructions for these platforms that are not listed on the WireGuard installation page, before proceeding to enabling WireGuard.

To install WireGuard on the default Amazon Machine Image (AMI):

   sudo yum install kernel-devel-`uname -r` -y
   sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm -y
   sudo curl -o /etc/yum.repos.d/jdoss-wireguard-epel-7.repo https://copr.fedorainfracloud.org/coprs/jdoss/wireguard/repo/epel-7/jdoss-wireguard-epel-7.repo
   sudo yum install wireguard-dkms wireguard-tools -y

AKS cluster nodes run Ubuntu with a kernel that has WireGuard installed already, so there is no manual installation required.

To install WireGuard for OpenShift v4.8:

  1. Install requirements:
  2. Download and configure the tools needed for kmods.
       FAKEROOT=$(mktemp -d)
       git clone https://github.com/tigera/kmods-via-containers
       cd kmods-via-containers
       make install FAKEROOT=${FAKEROOT}
       cd ..
       git clone https://github.com/tigera/kvc-wireguard-kmod
       cd kvc-wireguard-kmod
       make install FAKEROOT=${FAKEROOT}
       cd ..
    
  3. Configure/edit ${FAKEROOT}/root/etc/kvc/wireguard-kmod.conf.

    a. You must then set the URLs for the KERNEL_CORE_RPM, KERNEL_DEVEL_RPM and KERNEL_MODULES_RPM packages in the conf file $FAKEROOT/etc/kvc/wireguard-kmod.conf. Obtain copies for kernel-core, kernel-devel, and kernel-modules rpms from RedHat Access and host it in an http file server that is reachable by your OCP workers.

    b. For help configuring kvc-wireguard-kmod/wireguard-kmod.conf and Wireguard version to kernel version compatibility, see the kvc-wireguard-kmod README file.

  4. Get RHEL Entitlement data from your own RHEL8 system from a host in your cluster.
    tar -czf subs.tar.gz /etc/pki/entitlement/ /etc/rhsm/ /etc/yum.repos.d/redhat.repo
    

    Please refer to Openshift documentation for more information about these entitlement files.

  5. Copy the subs.tar.gz file to your workspace and then extract the contents using the following command.
    tar -x -C ${FAKEROOT}/root -f subs.tar.gz
    
  6. Transpile your machine config using CoreOS Butane.
    cd kvc-wireguard-kmod
    make ignition FAKEROOT=${FAKEROOT} > mc-wg.yaml
    
  7. With the KUBECONFIG set for your cluster, run the following command to apply the MachineConfig which will install WireGuard across your cluster.
    oc create -f mc-wg.yaml
    

Enable WireGuard for a cluster

Enable WireGuard encryption across all the nodes using the following command.

kubectl patch felixconfiguration default --type='merge' -p '{"spec":{"wireguardEnabled":true}}'

Enable WireGuard encryption across all the nodes using the following command.

calicoctl patch felixconfiguration default --type='merge' -p '{"spec":{"wireguardEnabled":true}}'

Perform the next step for EKS and AKS clusters only, and only if your cluster is using the cloud provider CNI plugin and not Calico CNI. Enable WireGuard encryption for direct node-to-node communications using the following command.

calicoctl patch felixconfiguration default --type='merge' -p '{"spec": {"wireguardHostEncryptionEnabled": true}}'

For OpenShift, add the Felix configuration with WireGuard enabled under custom resources.

Note: The above command can be used to change other WireGuard attributes. For a list of other WireGuard parameters and configuration evaluation, see the Felix configuration.

We recommend that you review and modify the MTU used by Calico networking when WireGuard is enabled to increase network performance. Follow the instructions in the Configure MTU to maximize network performance guide to set the MTU to a value appropriate for your network.

Disable WireGuard for an individual node

To disable WireGuard on a specific node with WireGuard installed, modify the node-specific Felix configuration. e.g., to turn off encryption for pod traffic on node my-node, use the following command:

cat <<EOF | kubectl apply -f -
apiVersion: projectcalico.org/v3
kind: FelixConfiguration
metadata:
  name: node.my-node
spec:
  logSeverityScreen: Info
  reportingInterval: 0s
  wireguardEnabled: false
EOF

With the above command, Calico will not encrypt any of the pod traffic to or from node my-node.

To enable encryption for pod traffic on node my-node again:

calicoctl patch felixconfiguration node.my-node --type='merge' -p '{"spec":{"wireguardEnabled":true}}'

Verify configuration

To verify that the nodes are configured for WireGuard encryption, check the node status set by Felix using calicoctl. For example:

   $ calicoctl get node <NODE-NAME> -o yaml
   ...
   status:
     ...
     wireguardPublicKey: jlkVyQYooZYzI2wFfNhSZez5eWh44yfq1wKVjLvSXgY=
     ...

Disable WireGuard for a cluster

To disable WireGuard on all nodes modify the default Felix configuration. For example:

  calicoctl patch felixconfiguration default --type='merge' -p '{"spec":{"wireguardEnabled":false}}'

Above and beyond