gcs: Check if the given project id argument exists (#4583)

Using GCS resource manager API, check if the provided
project id is already created and associated to the current
user account.

cmd/gateway-gcs.go

@@ -29,7 +29,10 @@ import (
 	"strings"
 	"time"
 
+	"golang.org/x/oauth2/google"
+
 	"cloud.google.com/go/storage"
+	cloudresourcemanager "google.golang.org/api/cloudresourcemanager/v1"
 	"google.golang.org/api/googleapi"
 	"google.golang.org/api/iterator"
 
@@ -176,14 +179,56 @@ func gcsToObjectError(err error, params ...string) error {
 // gcsProjectIDRegex defines a valid gcs project id format
 var gcsProjectIDRegex = regexp.MustCompile("^[a-z][a-z0-9-]{5,29}$")
 
-// isValidGCSProjectId - checks if a given project id is valid or not.
-// Project IDs must start with a lowercase letter and can have lowercase
-// ASCII letters, digits or hyphens. Project IDs must be between 6 and 30 characters.
+// isValidGCSProjectIDFormat - checks if a given project id format is valid or not.
+// Project IDs must start with a lowercase letter and can have lowercase ASCII letters,
+// digits or hyphens. Project IDs must be between 6 and 30 characters.
 // Ref: https://cloud.google.com/resource-manager/reference/rest/v1/projects#Project (projectId section)
-func isValidGCSProjectID(projectID string) bool {
+func isValidGCSProjectIDFormat(projectID string) bool {
+	// Checking projectID format
 	return gcsProjectIDRegex.MatchString(projectID)
 }
 
+// checkGCSProjectID - checks if the project ID does really exist using resource manager API.
+func checkGCSProjectID(ctx context.Context, projectID string) error {
+	// Check if a project id associated to the current account does really exist
+	resourceManagerClient, err := google.DefaultClient(ctx, cloudresourcemanager.CloudPlatformReadOnlyScope)
+	if err != nil {
+		return err
+	}
+
+	baseSvc, err := cloudresourcemanager.New(resourceManagerClient)
+	if err != nil {
+		return err
+	}
+
+	projectSvc := cloudresourcemanager.NewProjectsService(baseSvc)
+
+	curPageToken := ""
+
+	// Iterate over projects list result pages and immediately return nil when
+	// the project ID is found.
+	for {
+		resp, err := projectSvc.List().PageToken(curPageToken).Context(ctx).Do()
+		if err != nil {
+			return fmt.Errorf("Error getting projects list: %s", err.Error())
+		}
+
+		for _, p := range resp.Projects {
+			if p.ProjectId == projectID {
+				return nil
+			}
+		}
+
+		if resp.NextPageToken != "" {
+			curPageToken = resp.NextPageToken
+		} else {
+			break
+		}
+	}
+
+	return errGCSProjectIDNotFound
+}
+
 // gcsGateway - Implements gateway for Minio and GCS compatible object storage servers.
 type gcsGateway struct {
 	client     *storage.Client
@@ -198,6 +243,11 @@ const googleStorageEndpoint = "storage.googleapis.com"
 func newGCSGateway(projectID string) (GatewayLayer, error) {
 	ctx := context.Background()
 
+	err := checkGCSProjectID(ctx, projectID)
+	if err != nil {
+		return nil, err
+	}
+
 	// Initialize a GCS client.
 	client, err := storage.NewClient(ctx)
 	if err != nil {