Docker's logic for resolving credentials from .dockercfg accepts two kinds of matches:
1. an exact match between the dockercfg entry and the image prefix
2. a hostname match between the dockercfg entry and the image prefix
This change implements the latter, which permits the docker client to take .dockercfg entries of the form:
https://quay.io/v1/
and use them for images of the form:
quay.io/foo/bar
even though they are not a prefix-match.
This change refactors the way Kubelet's DockerPuller handles the docker config credentials to utilize a new credentialprovider library.
The credentialprovider library is based on several of the files from the Kubelet's dockertools directory, but supports a new pluggable model for retrieving a .dockercfg-compatible JSON blob with credentials.
With this change, the Kubelet will lazily ask for the docker config from a set of DockerConfigProvider extensions each time it needs a credential.
This change provides common implementations of DockerConfigProvider for:
- "Default": load .dockercfg from disk
- "Caching": wraps another provider in a cache that expires after a pre-specified lifetime.
GCP-only:
- "google-dockercfg": reads a .dockercfg from a GCE instance's metadata
- "google-dockercfg-url": reads a .dockercfg from a URL specified in a GCE instance's metadata.
- "google-container-registry": reads an access token from GCE metadata into a password field.
Eric Paris