Rewrite to remove the `github.com/docker/docker/registry` dependency,
which will not be included in the upcoming "api" and "client" modules,
and will not be a public package in the module used for the daemon itself.
1. don't call "/info" API endpoint to get default registry
The `IndexServerAddress` in the `/info` endpoint was added as part of the
initial Windows implementation of the engine. For legal reasons, Microsoft
Windows (and thus Docker images based on Windows) were not allowed to be
distributed through non-Microsoft infrastructure. As a temporary solution,
a dedicated "registry-win-tp3.docker.io" registry was created to serve
Windows images.
Using separate registries was not an ideal solution, and a more permanent
solution was created by introducing "foreign image layers" in the distribution
spec, after which the "registry-win-tp3.docker.io" ceased to exist, and
removed from the engine through docker/docker PR 21100.
However, the `ElectAuthServer` was left in place, quoting from that PR;
> make the client check which default registry the daemon uses is still
> more correct than leaving it up to the client, even if it won't technically
> matter after this PR. There may be some backward compatibility scenarios
> where `ElectAuthServer` [sic] is still helpful.
That comment was 10 Years ago, and the CLI stopped using this information,
as the default registry is not configurable, so in practice was a static
value. (see b4ca1c7368).
2. replace `ParseRepositoryInfo` and `GetAuthConfigKey` with local impl
The `ParseRepositoryInfo` function was originally implemented for use by
the daemon itself. It returns a `RepositoryInfo` struct that holds information
about the repository and the registry the repository can be found in.
As it was written for use by the daemon, it also was designed to be used
in combination with the daemon's configuration (such as mirrors, and
insecure registries). If no daemon configuration is present, which would
be the case when used in a CLI, it uses fallback logic as used in the daemon
to detect if the registry is running on a localhost / loopback address,
because such addresses are allowed to be "insecure" by default; this includes
resolving the IP-address of the host (if it's not an IP-address).
Unfortunately, these functions (and related types) were reused in the
CLI and many other places, which resulted in those types to be deeply
ingrained in interfaces and (external) code.
For compose; it was only used to get the "auth-config key" to use for
looking up auth information from the credentials store, which still
needs special handling for the "default" (docker hub) domain, which
unlike other image references doesn't use the hostname included in
the image reference for the actual registry (and key for storing
auth).
For those that want to follow along;
First, note that `GetAuthConfig` only requires a `registry.IndexInfo`, so not
the whole `RepositoryInfo` struct;
https://github.com/moby/moby/blob/v28.3.3/registry/types.go#L8-L24
From the `registry.IndexInfo` it only uses the `IsOfficial` and `Name` fields;
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L390-L395
But to get the `IndexInfo`, `ParseRepositoryInfo` is needed, which first
takes the image reference's "domain name" (e.g. `docker.io`);
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L421
This gets "normalized" for some cases where the `info.IndexServerAddress`
was incorrectly assumed to be the canonical domain for Docker Hub registry,
and which _does_ happen to also be accessible as a "v2" registry.
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L334-L341
After normalizing, it checks if it's a docker hub address ("docker.io"
after normalizing); Docker Hub is always required to use a secure
connection, so no detection happens, and the `Official` field is set
to indicate it's Docker Hub (this code path was already simplified
as historically it would try to find daemon configuration (or otherwise
use a default) for Mirror configuration;
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L420-L443
For non-Docker Hub registries, it also sets the name, and attempts
to detect if the registry is allowed to be "insecure";
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L435-L442
Which (as mentioned) involves parsing the address and, if needed, resolving
the hostname
https://github.com/moby/moby/blob/v28.3.3/registry/config.go#L445-L481
As `Insecure` is not used for looking up the auth-config key, all of the
above can be reduced to;
- Is the hostname obtained from the image reference "docker.io" (after normalizing)?
- If so, use the special `https://index.docker.io/v1/` as auth-config key (another horrible remnant)
- Otherwise use the hostname obtained from the image reference as-is
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The metadata types and consts where moved to a separate package,
so update the code to use the new location instead of the aliases
provided.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
