Support Podman's auth.json in RegistryAuthLocator

[sebastiankirsch]

Hej there,

I've some colleagues using Podman instead of Docker. Running Testcontainers works just fine as well, yet authenticating against a registry is an issue there: Podman stores credentials at ~/.config/containers/auth.json. When copying that file to ~/.docker/config.json, Testcontainers fetches images as expected.

If it's agreeable, I'd create a PR so that RegistryAuthLocator considers that file as well.
What do you think?

[kiview]

Hi @sebastiankirsch,

thanks for the suggestion. In general, we don't intend to add Podman specific code and in the past had good experiences with reporting Docker "incompatibilities" to upstream Podman (they already have a couple of compatibility mode flags in place, IMO for exactly these use cases).

Not that you can already configure the config location by using DOCKER_CONFIG, does that work for your colleagues?

[sebastiankirsch]

Thanks for the quick reply, @kiview !

DOCKER_CONFIG doesn't help, since it only allows to set the path to the config.json, so the auth.json file won't be read.

I wasn't aware of that "policy", but I sure understand why you want to focus on Docker "standards".
And indeed, https://docs.podman.io/en/stable/markdown/podman-login.1.html#authfile-path may hold a solution for us. Thanks for the hint!

[eddumelendez]

I think @kiview meant DOCKER_AUTH_CONFIG. See https://java.testcontainers.org/supported_docker_environment/#docker-registry-authentication

[sebastiankirsch]

@eddumelendez that ENV variable needs to contain JSON, like the files do.
From a practical point of view, it doesn't make much difference if a file is copied or the ENV variable is statically set with some JSON content.

Referring to the file via symlink is most comfortable; but my colleagues using windows don't have that option.

[sebastiankirsch]

(they already have a couple of compatibility mode flags in place, IMO for exactly these use cases).

After considering your hint, I found the REGISTRY_AUTH_FILE flag for Podman, and that makes Podman Docker/Testcontainers-compatible. Thanks again!

[sebastiankirsch]

Would you accept a PR extending https://github.com/testcontainers/testcontainers-java/blob/main/docs/supported_docker_environment/index.md?

[eddumelendez]

Yes, I think it is a good hint. Thanks for sharing!