Transparent Encryption (stable/beta)

This guide explains how to configure Cilium to use IPsec based transparent encryption using Kubernetes secrets to distribute the IPsec keys. After this configuration is complete all traffic between Cilium managed endpoints, as well as Cilium managed host traffic, will be encrypted using IPsec. This guide uses Kubernetes secrets to distribute keys. Alternatively, keys may be manually distributed but that is not shown here.

Note

The encryption feature is stable in combination with the direct-routing and ENI datapath mode. In combination with encapsulation/tunneling, the feature is still in beta phase.

Generate & import the PSK

First create a Kubernetes secret for the IPsec keys to be stored. This will generate the necessary IPsec keys which will be distributed as a Kubernetes secret called cilium-ipsec-keys. In this example we use GMC-128-AES, but any of the supported Linux algorithms may be used. To generate use the following

$ kubectl create -n kube-system secret generic cilium-ipsec-keys \
    --from-literal=keys="3 rfc4106(gcm(aes)) $(echo $(dd if=/dev/urandom count=20 bs=1 2> /dev/null| xxd -p -c 64)) 128"

The secret can be displayed with kubectl -n kube-system get secret and will be listed as ‘cilium-ipsec-keys’.

$ kubectl -n kube-system get secrets cilium-ipsec-keys
NAME                TYPE     DATA   AGE
cilium-ipsec-keys   Opaque   1      176m

Enable Encryption in Cilium

Install Helm to prepare generating the deployment artifacts based on the Helm templates.

Setup helm repository:

helm repo add cilium https://helm.cilium.io/

Deploy Cilium release via Helm:

helm install cilium cilium/cilium --version 1.7.0 \
  --namespace kube-system \
  --set global.encryption.enabled=true \
  --set global.encryption.nodeEncryption=false

At this point the Cilium managed nodes will be using IPsec for all traffic. For further information on Cilium’s transparent encryption, see Architecture.

Encryption interface

If direct routing is being used an additional argument can be used to identify the network facing interface. If no interface is specified the default route link is chosen by inspecting the routing tables. This will work in many cases but depending on routing rules users may need to specify the encryption interface as follows:

--set global.encryption.interface=ethX

Node to node encryption

In order to enable node-to-node encryption, add:

[...]
--set global.encryption.enabled=true \
--set global.encryption.nodeEncryption=true

Validate the Setup

Run a bash shell in one of the Cilium pods with kubectl -n kube-system exec -ti cilium-7cpsm -- bash and execute the following commands:

  1. Install tcpdump
apt-get update
apt-get -y install tcpdump
  1. Check that traffic is encrypted:
tcpdump -n -i cilium_vxlan
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on cilium_vxlan, link-type EN10MB (Ethernet), capture size 262144 bytes
15:16:21.626416 IP 10.60.1.1 > 10.60.0.1: ESP(spi=0x00000001,seq=0x57e2), length 180
15:16:21.626473 IP 10.60.1.1 > 10.60.0.1: ESP(spi=0x00000001,seq=0x57e3), length 180
15:16:21.627167 IP 10.60.0.1 > 10.60.1.1: ESP(spi=0x00000001,seq=0x579d), length 100
15:16:21.627296 IP 10.60.0.1 > 10.60.1.1: ESP(spi=0x00000001,seq=0x579e), length 100
15:16:21.627523 IP 10.60.0.1 > 10.60.1.1: ESP(spi=0x00000001,seq=0x579f), length 180
15:16:21.627699 IP 10.60.1.1 > 10.60.0.1: ESP(spi=0x00000001,seq=0x57e4), length 100
15:16:21.628408 IP 10.60.1.1 > 10.60.0.1: ESP(spi=0x00000001,seq=0x57e5), length 100

Key Rotation

To replace cilium-ipsec-keys secret with a new keys,

KEYID=$(kubectl get secret -n kube-system cilium-ipsec-keys -o yaml|grep keys: | awk '{print $2}' | base64 -d | awk '{print $1}')
if [[ $KEYID -gt 15 ]]; then KEYID=0; fi
data=$(echo "{\"stringData\":{\"keys\":\"$((($KEYID+1))) "rfc4106\(gcm\(aes\)\)" $(echo $(dd if=/dev/urandom count=20 bs=1 2> /dev/null| xxd -p -c 64)) 128\"}}")
kubectl patch secret -n kube-system cilium-ipsec-keys -p="${data}" -v=1

Then restart cilium agents to transition to the new key. During transition the new and old keys will be in use. The cilium agent keeps per endpoint data on which key is used by each endpoint and will use the correct key if either side has not yet been updated. In this way encryption will work as new keys are rolled out.

The KEYID environment variable in the above example stores the current key ID used by Cilium. The key variable is a uint8 with value between 0-16 and should be monotonically increasing every re-key with a rollover from 16 to 0. The cilium agent will default to KEYID of zero if its not specified in the secret.

Troubleshooting

  • Make sure that the Cilium pods have kvstore connectivity:

    cilium status
KVStore:                Ok   etcd: 1/1 connected: http://127.0.0.1:31079 - 3.3.2 (Leader)
[...]

  • Check for level=warning and level=error messages in the Cilium log files

  • Run a bash in a Cilium and validate the following:

    • Routing rules matching on fwmark:

      ip rule list
1:      from all fwmark 0xd00/0xf00 lookup 200
1:      from all fwmark 0xe00/0xf00 lookup 200
[...]

    • Content of routing table 200

      ip route list table 200
local 10.60.0.0/24 dev cilium_vxlan proto 50 scope host
10.60.1.0/24 via 10.60.0.1 dev cilium_host

    • XFRM policy:

      ip xfrm p
src 10.60.1.1/24 dst 10.60.0.1/24
        dir fwd priority 0
        mark 0xd00/0xf00
        tmpl src 10.60.1.1 dst 10.60.0.1
                proto esp spi 0x00000001 reqid 1 mode tunnel
src 10.60.1.1/24 dst 10.60.0.1/24
        dir in priority 0
        mark 0xd00/0xf00
        tmpl src 10.60.1.1 dst 10.60.0.1
                proto esp spi 0x00000001 reqid 1 mode tunnel
src 10.60.0.1/24 dst 10.60.1.1/24
        dir out priority 0
        mark 0xe00/0xf00
        tmpl src 10.60.0.1 dst 10.60.1.1
                proto esp spi 0x00000001 reqid 1 mode tunnel

    • XFRM state:

      ip xfrm s
src 10.60.0.1 dst 10.60.1.1
        proto esp spi 0x00000001 reqid 1 mode tunnel
        replay-window 0
        auth-trunc hmac(sha256) 0x6162636465666768696a6b6c6d6e6f70717273747576777a797a414243444546 96
        enc cbc(aes) 0x6162636465666768696a6b6c6d6e6f70717273747576777a797a414243444546
        anti-replay context: seq 0x0, oseq 0xe0c0, bitmap 0x00000000
        sel src 0.0.0.0/0 dst 0.0.0.0/0
src 10.60.1.1 dst 10.60.0.1
        proto esp spi 0x00000001 reqid 1 mode tunnel
        replay-window 0
        auth-trunc hmac(sha256) 0x6162636465666768696a6b6c6d6e6f70717273747576777a797a414243444546 96
        enc cbc(aes) 0x6162636465666768696a6b6c6d6e6f70717273747576777a797a414243444546
        anti-replay context: seq 0x0, oseq 0x0, bitmap 0x00000000
        sel src 0.0.0.0/0 dst 0.0.0.0/0

Disabling Encryption

To disable the encryption, regenerate the YAML with the option global.encryption.enabled=false