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.

Build and run a Python application

The recommended way to use this image is to use a multi-stage Dockerfile with the -dev version of the image as the build stage. For the runtime stage, simply remove the -dev suffix from the image tag. For example, use the image tag dhi.io/python:3.9.23-debian13-fips-dev for the build stage, and use dhi.io/python:3.9.23-debian13-fips for the runtime stage.

Create a new directory and use the following Dockerfile to get started. Replace <tag> with the image variant.

# syntax=docker/dockerfile:1

## -----------------------------------------------------
## Build stage (use tag with -dev suffix: e.g. 3.9.23-debian13-fips-dev)
FROM dhi.io/python:<tag> AS build-stage

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/app/venv/bin:$PATH"

WORKDIR /app

RUN python -m venv /app/venv
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

## -----------------------------------------------------
## Final stage (use the same tag as above but without the -dev suffix e.g. 3.9.23-debian13-fips)
FROM dhi.io/python:<tag> AS runtime-stage

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/app/venv/bin:$PATH"

WORKDIR /app

COPY --from=build-stage /app/venv /app/venv
COPY app.py .

CMD ["python", "/app/app.py"]

Next, create app.py and requirements.txt files in the same directory.

# app.py

import openai
import numpy as np
import pandas as pd

def main():
    print("Package versions:")
    print(f"openai: {openai.__version__}")
    print(f"numpy: {np.__version__}")
    print(f"pandas: {pd.__version__}")

if __name__ == "__main__":
    main()

openai
numpy
pandas

Run the following commands to build and run the sample app. You should see output printing the package versions.

docker build -t my-python-app .
docker run --rm --name my-running-app my-python-app

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

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. Docker Hardened Python images include FIPS-compliant variants for environments requiring Federal Information Processing Standards compliance.

Modify your app.py file to the following script to verify FIPS status and availability.

# app.py

import ssl
import hashlib

def main():
    try:
        hashlib.md5("test_str".encode("utf-8")).hexdigest()
        print("MD5: Available (not FIPS safe)")
    except ValueError as e:
        print("MD5: Disabled (FIPS safe)")

    # list available ciphers
    try:
        ctx = ssl.create_default_context()
        ciphers = [c['name'] for c in ctx.get_ciphers()]
        print("Cipher count:", len(ciphers))
    except Exception as e:
        print("Error getting ciphers:", e)

if __name__ == "__main__":
    main()

Rebuild your image and then run docker run --rm --name my-running-app my-python-app again to print FIPS status and available modules. You should see the following output if FIPS is enabled:

MD5: Disabled (FIPS safe)
Cipher count: 26

Recompiling Python dependencies with the FIPS OpenSSL provider

When importing Python packages that have binaries pre-built it can happen that those binaries might have been statically linked to a non-FIPS compliant OpenSSL implementation. Therefore the recommended approach to install those dependencies is to build them from source. This makes sure that they are statically linked against our FIPS compliant provider. The following is an example:

# syntax=docker/dockerfile:1
FROM dhi.io/python:<tag>-fips-dev AS build-stage
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/.venv/bin:$PATH"

RUN python -m venv /.venv
# Rebuild the cryptography binary linking it with OpenSSL
RUN apk add --no-cache openssl-dev
RUN pip install --no-cache-dir --no-binary cryptography cryptography boto3

FROM dhi.io/python:<tag>-fips AS build-stage
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/.venv/bin:$PATH"
WORKDIR /
COPY --from=build-stage /.venv /.venv
CMD ["python"]

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.

Image digests for the /opt path

The installation location of Python has moved from /opt to /usr. If you need to temporarily keep the old /opt path while you migrate, pin to one of the digests below. These are the last images published with Python installed under /opt.