[eclipse-kanto#307] Provide how to guide for verifying signed contain…

…er images

Signed-off-by: Dimitar Dimitrov <[email protected]>

web/site/content/docs/how-to-guides/verify-signed-container-images.md

@@ -0,0 +1,152 @@
+---
+title: "Verify signed container images"
+type: docs
+description: >
+    Verify that container image is signed when creating a container from it in Kanto Container Management.
+weight: 5
+---
+
+By following the steps below you will sign a container image and push it to a local registry using a{{% refn "https://github.com/notaryproject/notation" %}}`notation`{{% /refn %}}. Then notation trust policy and Kanto Container Management be configured in a way that running containers from the signed image via kanto-cm CLI will be successfull, while running containers from unsigned images will fail.
+
+### Before you begin
+
+To ensure that your edge device is capable to execute the steps in this guide, you need:
+
+* If you don't have an installed and running Eclipse Kanto, follow {{% relrefn "install" %}} Install Eclipse Kanto {{% /relrefn %}}
+* Installed {{% refn "https://notaryproject.dev/docs/user-guides/installation/cli/" %}} Notation CLI {{% /refn %}}
+* Installed and running {{% refn "https://www.docker.com/products/docker-desktop/" %}} Docker {{% /refn %}}
+
+### Create an image and push it to a local registry using docker and than sign it with notation
+
+Run a local container registry:
+```shell
+sudo docker run -d -p 5000:5000 -e REGISTRY_STORAGE_DELETE_ENABLED=true --name registry registry
+```
+
+Build a dummy hello world image and push it to the registry:
+```shell
+cat <<EOF | sudo docker build -t localhost:5000/dummy-hello:signed -
+FROM busybox:latest
+CMD [ "echo", "Hello World" ]
+EOF
+sudo docker push localhost:5000/dummy-hello:signed
+```
+
+{{% tip %}}
+When signing and verifying container images it is recommended to use the image digest instead of a tag as the digest is immutable.
+{{% /tip %}}
+Get the image digest and assign it to an environment variable to be used the next steps of the guide:
+```shell
+export IMAGE=$(sudo docker inspect --format='{{index .RepoDigests 0}}' localhost:5000/dummy-hello:signed)
+echo $IMAGE
+```
+
+Generate a key-pair with notation and add it as the default key to be used by notation when signing:
+```shell
+notation cert generate-test --default "kanto"
+```
+
+Sign the image and store the signature in the registry:
+```shell
+notation sign $IMAGE
+```
+
+### Configure notation truspolicy and container management verifier
+
+Get the notation config directory and assign it to an environment variable to be used in the next steps of the guide:
+```shell
+export NOTATION_CONFIG=${XDG_CONFIG_HOME:-$HOME/.config}/notation
+echo $NOTATION_CONFIG
+``` 
+
+Create a simple {{% refn "https://github.com/notaryproject/specifications/blob/main/specs/trust-store-trust-policy.md#trust-policy" %}} notation trustpolicy {{% /refn %}} as a `trustpolicy.json` file in the notation config directory: 
+```shell
+cat <<EOF | tee $NOTATION_CONFIG/trustpolicy.json
+{
+  "version": "1.0",
+  "trustPolicies": [
+    {
+      "name": "kanto-images",
+      "registryScopes": [ "*" ],
+      "signatureVerification": {
+        "level" : "strict"
+      },
+      "trustStores": [ "ca:kanto" ],
+      "trustedIdentities": [ "*" ]
+    }
+  ]
+}
+EOF
+```
+
+Create a backup of the initial Kanto Container Management configuration that is found in `/etc/container-management/config.json`(the backup will be restored at the end of the guide):
+```shell
+sudo cp /etc/container-management/config.json /etc/container-management/config-backup.json
+```
+
+Configure the use of notation verifier, set it's config directory and also mark the local registry as a insecure one:
+```shell
+cat <<EOF | sudo tee /etc/container-management/config.json
+{
+  "log": {
+    "log_file": "/var/log/container-management/container-management.log"
+  },
+  "containers": {
+    "image_verifier_type": "notation",
+    "image_verifier_config": {
+      "configDir": "$NOTATION_CONFIG"
+    },
+    "insecure_registries": [ "localhost:5000" ]
+  }
+}
+EOF
+```
+
+Restart the Container Management service for the changes to take effect:
+```shell
+sudo systemctl restart container-management.service
+```
+
+### Verify
+
+Create and run container from the signed image. The container prints `Hello world` to the console:
+```shell
+sudo kanto-cm create --name dummy-hello --rp no --t $IMAGE
+sudo kanto-cm start --name dummy-hello --a
+```
+
+
+Make sure that docker hub hello_world image is not cached localy and verify that creating containers from it fails, as the image is not signed and the signature verification fails:
+```shell
+sudo ctr -n kanto-cm image remove docker.io/library/hello-world:latest
+sudo kanto-cm create --name dockerhub-hello --rp no --t docker.io/library/hello-world:latest
+```
+
+### Clean up
+
+Remove the created container from Kanto Container Management and the localy cached image:
+```shell
+sudo kanto-cm remove -n dummy-hello
+sudo ctr -n kanto-cm image rm $IMAGE
+```
+
+Restore the initial Kanto Container Management configuration and restart the service:
+```shell
+sudo mv -f /etc/container-management/config-backup.json /etc/container-management/config.json
+sudo systemctl restart container-management.service
+```
+
+Remove the local container registry running Docker and the localy cached images:
+```shell
+sudo docker rm -f registry
+sudo docker image rm localhost:5000/dummy-hello:signed registry:latest
+```
+
+Reset the notation configuration by removing the directory:
+```shell
+rm -r $NOTATION_CONFIG
+```
+
+Unset exported environment variables:
+```shell
+unset IMAGE NOTATION_CONFIG