pkg/docker/config/config.go
func GetAuthentication(sys *types.SystemContext, registry string) (string, string, error) {
	if sys != nil && sys.DockerAuthConfig != nil {
		return sys.DockerAuthConfig.Username, sys.DockerAuthConfig.Password, nil
	}

	dockerLegacyPath := filepath.Join(homedir.Get(), dockerLegacyHomePath)
	var paths []string
	pathToAuth, err := getPathToAuth(sys)
	if err == nil {
		paths = append(paths, pathToAuth)
	} else {
		// Error means that the path set for XDG_RUNTIME_DIR does not exist
		// but we don't want to completely fail in the case that the user is pulling a public image
		// Logging the error as a warning instead and moving on to pulling the image
		logrus.Warnf("%v: Trying to pull image in the event that it is a public image.", err)
	}
	paths = append(paths, filepath.Join(homedir.Get(), dockerHomePath), dockerLegacyPath)

	for _, path := range paths {
		legacyFormat := path == dockerLegacyPath
		username, password, err := findAuthentication(registry, path, legacyFormat)
		if err != nil {
			return "", "", err
		}
		if username != "" && password != "" {
			return username, password, nil
		}
	}
	return "", "", nil
}
func GetAuthentication(sys *types.SystemContext, registry string) (string, string, error) {
	if sys != nil && sys.DockerAuthConfig != nil {
		return sys.DockerAuthConfig.Username, sys.DockerAuthConfig.Password, nil
	}

	dockerLegacyPath := filepath.Join(homedir.Get(), dockerLegacyHomePath)
	var paths []string
	pathToAuth, err := getPathToAuth(sys)
	if err == nil {
		paths = append(paths, pathToAuth)
	} else {
		// Error means that the path set for XDG_RUNTIME_DIR does not exist
		// but we don't want to completely fail in the case that the user is pulling a public image
		// Logging the error as a warning instead and moving on to pulling the image
		logrus.Warnf("%v: Trying to pull image in the event that it is a public image.", err)
	}
	paths = append(paths, filepath.Join(homedir.Get(), dockerHomePath), dockerLegacyPath)

	for _, path := range paths {
		legacyFormat := path == dockerLegacyPath
		username, password, err := findAuthentication(registry, path, legacyFormat)
		if err != nil {
			return "", "", err
		}
		if username != "" && password != "" {
			return username, password, nil
		}
	}
	return "", "", nil
}
// GetAuthentication returns the registry credentials stored in
// either auth.json file or .docker/config.json
// If an entry is not found empty strings are returned for the username and password