How to use this image

All examples in this guide use the public image. If you've mirrored the repository for your own use (for example, to your Docker Hub namespace), update your commands to reference the mirrored image instead of the public one.

For example:

• Public image: dhi.io/<repository>:<tag>
• Mirrored image: <your-namespace>/dhi-<repository>:<tag>

For the examples, you must first use docker login dhi.io to authenticate to the registry to pull the images.

Start a go-httpbin instance

The server listens on port 8080. go-httpbin has no authentication, so the example publishes the port on the loopback interface only:

$ docker run -d --name go-httpbin -p 127.0.0.1:8080:8080 dhi.io/go-httpbin:<tag>

Send a request and go-httpbin echoes it back as JSON:

$ curl -s 'http://127.0.0.1:8080/get?probe=dhi'
{
  "args": {
    "probe": [
      "dhi"
    ]
  },
  ...
  "method": "GET",
  "origin": "172.17.0.1",
  "url": "http://127.0.0.1:8080/get?probe=dhi"
}

Configure the server with command-line flags or the matching environment variables; flags take precedence. This example moves the listener to port 9090 and reports the full build details on /version:

$ docker run -d --name go-httpbin -e PORT=9090 -e USE_FULL_VERSION=true -p 127.0.0.1:9090:9090 \
  dhi.io/go-httpbin:<tag>
$ curl -s http://127.0.0.1:9090/version
{
  "service": "go-httpbin",
  "version": "<version>",
  ...
}

Replace <version> with the go-httpbin version of the tag you run. The full list of flags and environment variables is in the go-httpbin README⁠.

Common go-httpbin use cases

Serve over HTTPS

go-httpbin serves HTTPS when given a certificate and key. The files must be readable by the nonroot user (UID 65532):

$ openssl req -x509 -newkey ec -pkeyopt ec_paramgen_curve:prime256v1 -nodes -days 365 \
  -subj "/CN=localhost" -keyout server.key -out server.crt
$ chmod 644 server.crt server.key
$ docker run -d --name go-httpbin -p 127.0.0.1:8443:8080 \
  -v "$(pwd)":/tls:ro \
  -e HTTPS_CERT_FILE=/tls/server.crt \
  -e HTTPS_KEY_FILE=/tls/server.key \
  dhi.io/go-httpbin:<tag>
$ curl -sk https://127.0.0.1:8443/get

Deploy to Kubernetes

This manifest is the upstream Kustomize deployment with the image reference replaced. Replace <tag> with the image tag, and add an imagePullSecrets entry if your cluster pulls from dhi.io with credentials:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin
  labels:
    app.kubernetes.io/name: httpbin
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: httpbin
  template:
    metadata:
      labels:
        app.kubernetes.io/name: httpbin
    spec:
      containers:
        - name: httpbin
          image: dhi.io/go-httpbin:<tag>
          ports:
            - name: http
              containerPort: 8080
              protocol: TCP
          livenessProbe:
            httpGet:
              path: /status/200
              port: http
          readinessProbe:
            httpGet:
              path: /status/200
              port: http
          securityContext:
            runAsNonRoot: true
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app.kubernetes.io/name: httpbin
spec:
  selector:
    app.kubernetes.io/name: httpbin
  ports:
    - name: http
      port: 80
      targetPort: http
      protocol: TCP
      appProtocol: http

Non-hardened images vs. Docker Hardened Images

• The upstream image's entrypoint is /usr/bin/go-httpbin. This image's entrypoint is /usr/local/bin/go-httpbin, a symlink to /usr/bin/go-httpbin. Both paths and /bin/go-httpbin, which the upstream README uses, resolve in every variant, so pass only flags as arguments: docker run dhi.io/go-httpbin:<tag> -port 9090.
• The upstream image sets the working directory to /home/nonroot and SSL_CERT_FILE in its environment. This image keeps the working directory at /, and only the Debian FIPS variants set SSL_CERT_FILE, as part of their OpenSSL FIPS configuration. go-httpbin reads no files from its working directory and makes no outbound TLS connections.

Image variants

Docker 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.

  go-httpbin is an exception: its FIPS variants run in the default FIPS 140 mode, which still allows the MD5 digest algorithm on /digest-auth and the SHA-1 WebSocket handshake on /websocket/echo, because the HTTP protocols require them. Set GODEBUG=fips140=only on the container to refuse them; /digest-auth and /websocket/echo then fail while the other endpoints, such as /get, keep serving.

Migrate to a Docker Hardened Image

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

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

   Docker 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 Docker 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.

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

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