Docker auth (#891)

* feat: read docker credentials from local docker config

* fix: url.Parse requires protocol

Co-authored-by: Björn Brauer <[email protected]>

* fix: docker decides by the existence of . or : if...

... the image is in a custom registry or not.

Co-authored-by: Björn Brauer <[email protected]>

* fix: make docker hostname detection more robust

* test: mock docker config for getImagePullOptions test

By default github actions have a docker config set with a token to pull
images from docker hub.

Co-authored-by: Markus Wolf <[email protected]>

Co-authored-by: Markus Wolf <[email protected]>

pkg/container/docker_pull.go

@@ -77,6 +77,7 @@ func getImagePullOptions(ctx context.Context, input NewDockerPullExecutorInput)
 	imagePullOptions := types.ImagePullOptions{
 		Platform: input.Platform,
 	}
+
 	if input.Username != "" && input.Password != "" {
 		logger := common.Logger(ctx)
 		logger.Debugf("using authentication for docker pull")
@@ -91,6 +92,21 @@ func getImagePullOptions(ctx context.Context, input NewDockerPullExecutorInput)
 			return imagePullOptions, err
 		}
 
+		imagePullOptions.RegistryAuth = base64.URLEncoding.EncodeToString(encodedJSON)
+	} else {
+		authConfig, err := LoadDockerAuthConfig(input.Image)
+		if err != nil {
+			return imagePullOptions, err
+		}
+		if authConfig.Username == "" && authConfig.Password == "" {
+			return imagePullOptions, nil
+		}
+
+		encodedJSON, err := json.Marshal(authConfig)
+		if err != nil {
+			return imagePullOptions, err
+		}
+
 		imagePullOptions.RegistryAuth = base64.URLEncoding.EncodeToString(encodedJSON)
 	}