spiffe helper

To display the version:

$ docker run --rm registry.ghost-prod.alphabravo.io/ghost-base/spiffe-helper:<tag> -version

To display help:

$ docker run --rm registry.ghost-prod.alphabravo.io/ghost-base/spiffe-helper:<tag> -help

To run with a configuration file and a shared SVID output volume:

$ docker run --rm \
  -v /run/spire/sockets:/run/spire/sockets \
  -v /path/to/helper.conf:/etc/spiffe-helper/helper.conf:ro \
  -v /path/to/certs:/certs \
  registry.ghost-prod.alphabravo.io/ghost-base/spiffe-helper:<tag> -config /etc/spiffe-helper/helper.conf

Replace /run/spire/sockets with the host path where the SPIFFE Workload API socket is exposed, and /path/to/certs with a host directory writable by uid 65532.

Workload API socket

SPIFFE Helper connects to the SPIFFE Workload API through a Unix domain socket. The socket is typically provided by a SPIRE Agent running on the same node, by a SPIFFE CSI driver, or by another Workload API implementation. You must mount the socket into the container and configure the agent_address field in the config file to point to it.

For a SPIRE Agent socket at /run/spire/sockets/agent.sock on the host, add:

-v /run/spire/sockets:/run/spire/sockets

And set in helper.conf:

agent_address = "/run/spire/sockets/agent.sock"

Configuration file

SPIFFE Helper requires an HCL configuration file. If -config is not specified, the binary looks for helper.conf in the working directory. Pass the path explicitly with -config /path/to/helper.conf. A minimal configuration that fetches X.509 SVIDs to /certs in daemon mode looks like:

agent_address  = "/run/spire/sockets/agent.sock"
cert_dir       = "/certs"
svid_file_name = "svid.pem"
svid_key_file_name  = "svid_key.pem"
svid_bundle_file_name = "svid_bundle.pem"
daemon_mode    = true

For the full list of configuration options, see the upstream README.

SVID output paths

SPIFFE Helper writes certificate and key files to the cert_dir directory defined in the config file. Mount a host directory or an emptyDir volume at that path and ensure it is writable by uid 65532. In Kubernetes, this is typically an emptyDir shared between the SPIFFE Helper init or sidecar container and the application container.

Health endpoint

The health endpoint is disabled by default. To enable it, add a health_checks block to helper.conf:

health_checks {
  listener_enabled = true
  bind_port        = "8081"
  liveness_path    = "/live"
  readiness_path   = "/ready"
}

When enabled, expose the port with -p 8081:8081 (or the equivalent Kubernetes containerPort) so that your orchestrator can reach the liveness and readiness endpoints.

Image variants

Ghost hardened images come in different variants depending on their intended use.

• Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

  • Run as the nonroot user
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the variant name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. For example, usage of MD5 fails in FIPS variants. The SPIFFE Helper FIPS variant runs in lenient FIPS mode (GODEBUG=fips140=on) because the go-jose library used transitively by go-spiffe uses SHA-1 for JWK thumbprints, which is not permitted in strict mode.

Migrate to a Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes.

The upstream ghcr.io/spiffe/spiffe-helper image also places the binary at /spiffe-helper and has an empty CMD, so switching to registry.ghost-prod.alphabravo.io/ghost-base/spiffe-helper is a near-drop-in replacement for most deployments. One important runtime difference is that the upstream image runs as root, while the Ghost hardened image runs as the nonroot user with uid 65532.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. Inspect the image variants to identify which packages are already installed.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

The following are common issues that you may encounter during migration.

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Ghost hardened images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.

If SPIFFE Helper exits with a permission error writing SVID files, verify that the cert_dir volume is writable by uid 65532.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10. To avoid issues, configure your application to listen on port 1025 or higher inside the container, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

Ghost hardened images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Ghost hardened images and update your Dockerfile if necessary.