Method lookasideStorageBaseURL

docker/registries_d.go:171–193

lookasideStorageBaseURL returns an appropriate signature storage URL for ref, for write access if “write”. the usage of the BaseURL is defined under docker/distribution registries—separate storage of docs/signature-protocols.md

(dr dockerReference, write bool)

// lookasideStorageBaseURL returns an appropriate signature storage URL for ref, for write access if “write”.
// the usage of the BaseURL is defined under docker/distribution registries—separate storage of docs/signature-protocols.md
func (config *registryConfiguration) lookasideStorageBaseURL(dr dockerReference, write bool) (*url.URL, error) {
	topLevel := config.signatureTopLevel(dr, write)
	var baseURL *url.URL
	if topLevel != "" {
		u, err := url.Parse(topLevel)
		if err != nil {
			return nil, fmt.Errorf("Invalid signature storage URL %s: %w", topLevel, err)
		}
		baseURL = u
	} else {
		// returns default directory if no lookaside specified in configuration file
		baseURL = builtinDefaultLookasideStorageDir(rootless.GetRootlessEUID())
		logrus.Debugf(" No signature storage configuration found for %s, using built-in default %s", dr.PolicyConfigurationIdentity(), baseURL.Redacted())
	}
	// NOTE: Keep this in sync with docs/signature-protocols.md!
	// FIXME? Restrict to explicitly supported schemes?
	repo := reference.Path(dr.ref) // Note that this is without a tag or digest.
	if path.Clean(repo) != repo {  // Coverage: This should not be reachable because /./ and /../ components are not valid in docker references
		return nil, fmt.Errorf("Unexpected path elements in Docker reference %s for signature storage", dr.ref.String())
	}
	baseURL.Path = baseURL.Path + "/" + repo
	return baseURL, nil
}

// builtinDefaultLookasideStorageDir returns default signature storage URL as per euid
func builtinDefaultLookasideStorageDir(euid int) *url.URL {