So we needed to fetch manifests of repositories from Docker Hub today. It’s not that hard. 30 lines of python can do it. But at the same time, you need to read docs with all the specs.

Authentication

The biggest pain. pull seems to be a privileged operation which requires authentication. Luckily you only need to obtain a token:

repo = "library/fedora"
login_template = "https://auth.docker.io/token?service=registry.docker.io&scope=repository:{repository}:pull"
token = requests.get(login_template.format(repository=repo), json=True).json()["token"]

This is documented nicely here.

API call for getting the manifest

That one is documented over here.

GET /v2/{repository}/manifests/{tag}

Nothing really to talk about: just fetch manifest of requested repository.

get_manifest_template = "https://registry.hub.docker.com/v2/{repository}/manifests/{tag}"
manifest = requests.get(
    get_manifest_template.format(repository=repo, tag=tag),
    headers={"Authorization": "Bearer {}".format(token)},
    json=True
).json()

Pretty simple, right?

The whole script is available in this github repo.

Happy hacking!