When tools like Podman or Docker pull container images, users prefer to use short names like fedora or alpine rather then fully specified image names registry.fedoraproject.org/fedora and docker.io/alpine, respectively. In container engines that allow you to specify more then a single registry for storing container images, using short names can lead to ambiguity.

Imagine that I have two registries defined and both contain an image named "foobar". Now if I specify foobar, I am not sure which image I will get. There is potential for malicious parties to take advantage of this by spoofing images and tricking users into pulling them.

We are building into these container engine tools the ability to use short name aliases to help mitigate the risk of pulling the wrong image, especially when the image is a well known short name.

Similar to aliases in shells such as Bash, a short-name alias has a left-hand name that is being replaced with a right-hand value. Short-name aliases can now be configured in the 'registries.conf' file as follows:

unqualified-search-registries=["registry.fedoraproject.org", "docker.io"]

[aliases]
"fedora"="registry.fedoraproject.org/fedora"

All aliases must be specified in the new “aliases” table. Using the above 'registries.conf' file, Podman will resolve “fedora” immediately and securely to “registry.fedoraproject.org/fedora”. We are currently assembling a public list of short-name aliases that can be used across the community. Multiple Linux distributions and companies have expressed interest in collaborating with the container engines, to help registry their images.

The goal of this REPO is to gather a list of shortnames from the community, to allow distributions to ship them in their distributions. The idea is this list could be added to the default 'registries.conf' file shipped by a distro.

This list is in the open to guarantee fairness. We do not want this to be a free for all land grab, so we will base the list of images on images at well known registries and distributions.

In the case of a conflicts, we will base the shortname on the original source of the image. For example if the Fedora image is available at 'docker.io' as well as at 'registry.fedoraproject.org', we will grab it from fedoraproject.

I am sure over time their might be further rules designed if this turns out to be a problem.

Of course distributions are always free to make changes to this list if/when they ship it.

Please verify that you are not conflicting with existing shortnames, or state your case on why your shortname should replace the existing short names.

The configuration file is intended to be shipped in the /etc/containers/registries.conf.d directory. This directory allows for supporting drop-in registries.conf configuration files that are loaded in alpha-numerical order. Users can easily add new files manually or via config managers such as Ansible or Salt. Please refer to the upstream documentation of the containers/image library to read more about the registries.conf format, and the loading behavior.

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