another ssh demo readme

container-images/dockerfiles/alpine-with-sshd/README.md

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+# SSH demo
+
+To demonstrate confidential containers capabilities, we run a pod with SSH public key authentication.
+
+Compared to the execution of and login to a shell on a pod, an SSH connection is cryptographically secured and requires a private key.
+It cannot be established by unauthorized parties, such as someone who controls the node.
+The container image contains the SSH host key that can be used for impersonating the host we will connect to.
+Because this container image is encrypted, and the key to decrypting this image is only provided in measurable ways (e.g. attestation or encrypted initrd), and because the pod/guest memory is protected, even someone who controls the node cannot steal this key.
+
+## Using a pre-provided container image
+
+If you would rather build the image with your own keys, skip to [Building the container image](#building-the-container-image).
+The [operator](/demos/operator-demo) can be used to set up a compatible runtime.
+
+A demo image is provided at [docker.io/katadocker/ccv0-ssh](https://hub.docker.com/r/katadocker/ccv0-ssh).
+It is encrypted with [Attestation Agent](https://github.com/confidential-containers/attestation-agent)'s [offline file system key broker](https://github.com/confidential-containers/attestation-agent/tree/64c12fbecfe90ba974d5fe4896bf997308df298d/src/kbc_modules/offline_fs_kbc) and [`aa-offline_fs_kbc-keys.json`](./aa-offline_fs_kbc-keys.json) as its key file.
+The private key for establishing an SSH connection to this container is given in [`ccv0-ssh`](./ccv0-ssh).
+To use it with SSH, its permissions should be adjusted: `chmod 600 ccv0-ssh`.
+The host key fingerprint is `SHA256:wK7uOpqpYQczcgV00fGCh+X97sJL3f6G1Ku4rvlwtR0`.
+
+All keys shown here are for demonstration purposes.
+To achieve actually confidential containers, use a hardware trusted execution environment and **do not** reuse these keys.
+
+Continue at [Connecting to the guest](#connecting-to-the-guest).
+
+## Building the container image
+
+The image built should be encrypted.
+To receive a decryption key at run time, the Confidential Containers project utilizes the [Attestation Agent](https://github.com/confidential-containers/attestation-agent).
+
+### Generating SSH keys
+
+```sh
+$ ssh-keygen -t ed25519 -f ccv0-ssh -P "" -C ""
+```
+
+generates an SSH key `ccv0-ssh` and the correspondent public key `ccv0-ssh.pub`.
+
+### Building the image
+
+The provided [`Dockerfile`](./Dockerfile) expects `ccv0-sh.pub` to exist.
+Using Docker, you can build with
+
+```sh
+$ docker build -t ccv0-ssh .
+```
+
+Alternatively, Buildah can be used (`buildah build` or formerly `buildah bud`).
+The SSH host key fingerprint is displayed during the build.
+
+## Connecting to the guest
+
+A [Kubernetes YAML file](./k8s-cc-ssh.yaml) specifying the [`kata`](https://github.com/kata-containers/kata-containers) runtime is included.
+If you use a [self-built image](#building-the-container-image), you should replace the image specification with the image you built.
+The default tag points to an `amd64` image, an `s390x` tag is also available.
+With common CNI setups, on the same host, with the service running, you can connect via SSH with
+
+```sh
+$ ssh -i ccv0-ssh root@$(kubectl get service ccv0-ssh -o jsonpath="{.spec.clusterIP}")
+```
+
+You will be prompted about whether the host key fingerprint is correct.
+This fingerprint should match the one specified above/displayed in the Docker build.
+
+`crictl`-compatible [sandbox](./cri-sandbox-config.yaml) and [container](./cri-container-config.yaml) configurations are also included, which forward the pod SSH port (22) to 2222 on the host (use the `-p` flag in SSH).