Image Signature Verification Admission Controller
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In this post I will show you how you can deploy Connaisseur to Image Signature Verification into a Kubernetes cluster.
Parts of the K8S Security Lab series
Container Runetime Security
- Part1: How to deploy CRI-O with Firecracker?
- Part2: How to deploy CRI-O with gVisor?
- Part3: How to deploy containerd with Firecracker?
- Part4: How to deploy containerd with gVisor?
- Part5: How to deploy containerd with kata containers?
Advanced Kernel Security
- Part1: Hardening Kubernetes with seccomp
- Part2: Linux user namespace management wit CRI-O in Kubernetes
- Part3: Hardening Kubernetes with seccomp
Network Security
- Part1: RKE2 Install With Calico
- Part2: RKE2 Install With Cilium
- Part3: CNI-Genie: network separation with multiple CNI
- Part3: Configurre network wit nmstate operator
- Part3: Kubernetes Network Policy
- Part4: Kubernetes with external Ingress Controller with vxlan
- Part4: Kubernetes with external Ingress Controller with bgp
- Part4: Central authentication with oauth2-proxy
- Part5: Secure your applications with Pomerium Ingress Controller
- Part6: CrowdSec Intrusion Detection System (IDS) for Kubernetes
- Part7: Kubernetes audit logs and Falco
Secure Kubernetes Install
- Part1: Best Practices to keeping Kubernetes Clusters Secure
- Part2: Kubernetes Secure Install
- Part3: Kubernetes Hardening Guide with CIS 1.6 Benchmark
- Part4: Kubernetes Certificate Rotation
User Security
- Part1: How to create kubeconfig?
- Part2: How to create Users in Kubernetes the right way?
- Part3: Kubernetes Single Sign-on with Pinniped OpenID Connect
- Part4: Kubectl authentication with Kuberos Depricated !!
- Part5: Kubernetes authentication with Keycloak and gangway Depricated !!
- Part6: kube-openid-connect 1.0 Depricated !!
Image Security
Pod Security
- Part1: Using Admission Controllers
- Part2: RKE2 Pod Security Policy
- Part3: Kubernetes Pod Security Admission
- Part4: Kubernetes: How to migrate Pod Security Policy to Pod Security Admission?
- Part5: Pod Security Standards using Kyverno
- Part6: Kubernetes Cluster Policy with Kyverno
Secret Security
- Part1: Kubernetes and Vault integration
- Part2: Kubernetes External Vault integration
- Part3: ArgoCD and kubeseal to encript secrets
- Part4: Flux2 and kubeseal to encrypt secrets
- Part5: Flux2 and Mozilla SOPS to encrypt secrets
Monitoring and Observability
- Part6: K8S Logging And Monitoring
- Part7: Install Grafana Loki with Helm3
Backup
What is Connaisseur?
Connaisseur is an admission controller for Kubernetes that integrates Image Signature Verification into a cluster, as a means to ensure that only valid images are being deployed.
Notary
Notary is an open source signing solution for containers based on The Update Framework Notary uses TUFs’ roles and key hierarchy for signing of the images. There are five keys to sign the metadata files which lists all filenames in the collection, their sizes and respective hashes.
apt install notary
docker pull alpine
docker tag alpine:latest devopstales/testimage:unsigned
docker push devopstales/testimage:unsigned
notary -s https://notary.docker.io -d ~/.docker/trust init -p docker.io/devopstales/testimage
Root key found, using: 31579f2a034add499da6e799bc9260d08a15ab1804298218f05f78d97a669f77
Enter passphrase for root key with ID 31579f2:
Enter passphrase for new targets key with ID 42e49c6:
Repeat passphrase for new targets key with ID 42e49c6:
Enter passphrase for new snapshot key with ID 399243c:
Repeat passphrase for new snapshot key with ID 399243c:
Enter username: devopstales
Enter password:
Auto-publishing changes to docker.io/devopstales/testimage
Enter username: devopstales
Enter password:
Successfully published changes for repository docker.io/devopstales/testimage
export DOCKER_CONTENT_TRUST=1
export DOCKER_CONTENT_TRUST_SERVER=https://notary.docker.io
docker tag alpine:latest devopstales/testimage:signed
docker push devopstales/testimage:signed
$ find ~/.docker/trust/ | head
/home/devopstales/.docker/trust/
/home/devopstales/.docker/trust/private
/home/devopstales/.docker/trust/private/1f4a9a0922605b3bc19c97e180d962d530721288f4fd0845ad0aa37ba4a6f95d.key
/home/devopstales/.docker/trust/private/fe30e72f5976b2ae7d0d365f28dacfae9c71f11ad854065603ccc806900e84fa.key
/home/devopstales/.docker/trust/private/3da0d27e2d3b964d238d1d184c7578b5f2737b918ec5b8265474e22b07b2ea22.key
/home/devopstales/.docker/trust/private/root-priv.key
/home/devopstales/.docker/trust/private/root-pub.pem
/home/devopstales/.docker/trust/tuf
/home/devopstales/.docker/trust/tuf/docker.io
/home/devopstales/.docker/trust/tuf/docker.io/devopstales
notary -s https://notary.docker.io -d ~/.docker/trust list docker.io/devopstales/testimage
NAME DIGEST SIZE (BYTES) ROLE
---- ------ ------------ ----
signed 4661fb57f7890b9145907a1fe2555091d333ff3d28db86c3bb906f6a2be93c87 528 targets/devopstales
Install Connaisseur
# The installer use yq so we need to install it
wget https://github.com/mikefarah/yq/releases/download/v4.2.0/yq_linux_amd64 -O /usr/bin/yq &&\
chmod +x /usr/bin/yq
# generate the public root cert
cd ~/.docker/trust/private
sed '/^role:\sroot$/d' $(grep -iRl "role: root" .) > root-priv.key
openssl ec -in root-priv.key -pubout -out root-pub.pem
git clone https://github.com/sse-secure-systems/connaisseur.git
cd connaisseur
nano helm/values.yaml
...
# the public part of the root key, for verifying notary's signatures
rootPubKey: |
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE9m6WfwViwT8lYjLF6jAs1bvd1hPp
cRUmONP49JszW1X/6Q22DygylIJGyC8IXeb3zBWVMoYDxauiqrFomHUOEA==
-----END PUBLIC KEY-----
make install
Test the Image Signature Verification
kubens default
kubectl run unsigned --image=docker.io/devopstales/testimage:unsigned
Error from server: admission webhook "connaisseur-svc.connaisseur.svc" denied the request: failed to verify signature of trust data.
kubectl run signed --image=docker.io/devopstales/testimage:signed
pod/signed created
kubectl get po
Final words
Connaisseur is a grate tool but has a few shortcomings:
- There is no option to whitelist images in a specific namespace.
- Connaisseur supports only one Notary server
- Connaisseur supports only one public key
Update:
Connaisseur 2.0 is released and solve all of this problems.
