fix(transport): relax universe checks (#2376)

This PR serves to relax universe mismatch checks, as a user specifying credentials via the option.WithTokenSource has provided a form of credential where the universe information is not directly accessible.

In these cases, we no longer perform the universe mismatch checks.

This PR also augments the existing mismatch checks to exercise a more diverse set of client options.

transport/grpc/dial.go

@@ -181,8 +181,12 @@ func dial(ctx context.Context, insecure bool, o *internal.DialSettings) (*grpc.C
 			if err != nil {
 				return nil, err
 			}
-			if o.GetUniverseDomain() != credsUniverseDomain {
-				return nil, internal.ErrUniverseNotMatch(o.GetUniverseDomain(), credsUniverseDomain)
+			if o.TokenSource == nil {
+				// We only validate non-tokensource creds, as TokenSource-based credentials
+				// don't propagate universe.
+				if o.GetUniverseDomain() != credsUniverseDomain {
+					return nil, internal.ErrUniverseNotMatch(o.GetUniverseDomain(), credsUniverseDomain)
+				}
 			}
 			grpcOpts = append(grpcOpts, grpc.WithPerRPCCredentials(grpcTokenSource{
 				TokenSource:   oauth.TokenSource{TokenSource: creds.TokenSource},

transport/http/dial.go

@@ -92,8 +92,12 @@ func newTransport(ctx context.Context, base http.RoundTripper, settings *interna
 		if err != nil {
 			return nil, err
 		}
-		if settings.GetUniverseDomain() != credsUniverseDomain {
-			return nil, internal.ErrUniverseNotMatch(settings.GetUniverseDomain(), credsUniverseDomain)
+		if settings.TokenSource == nil {
+			// We only validate non-tokensource creds, as TokenSource-based credentials
+			// don't propagate universe.
+			if settings.GetUniverseDomain() != credsUniverseDomain {
+				return nil, internal.ErrUniverseNotMatch(settings.GetUniverseDomain(), credsUniverseDomain)
+			}
 		}
 		paramTransport.quotaProject = internal.GetQuotaProject(creds, settings.QuotaProject)
 		ts := creds.TokenSource

transport/http/dial_test.go

@@ -7,12 +7,12 @@ package http
 import (
 	"context"
 	"fmt"
+	"strings"
 	"testing"
 
 	"go.opencensus.io/plugin/ochttp"
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
-	"google.golang.org/api/internal"
 	"google.golang.org/api/option"
 )
 
@@ -41,16 +41,88 @@ func TestNewClient(t *testing.T) {
 	}
 }
 
-func TestNewClient_MismatchedUniverseDomainCreds(t *testing.T) {
+func TestNewClient_MismatchedUniverseChecks(t *testing.T) {
+
 	rootTokenScope := "https://www.googleapis.com/auth/cloud-platform"
-	universeDomain := "example.com"
-	universeDomainDefault := "googleapis.com"
-	creds := &google.Credentials{} // universeDomainDefault
-	wantErr := internal.ErrUniverseNotMatch(universeDomain, universeDomainDefault)
-	_, _, err := NewClient(context.Background(), option.WithUniverseDomain(universeDomain),
-		option.WithCredentials(creds), option.WithScopes(rootTokenScope))
-
-	if err.Error() != wantErr.Error() {
-		t.Fatalf("got: %v, want: %v", err, wantErr)
+	otherUniverse := "example.com"
+	defaultUniverse := "googleapis.com"
+	fakeCreds := `
+	{"type": "service_account",
+     "project_id": "some-project",
+     "universe_domain": "UNIVERSE"}`
+
+	// utility function to make a fake credential quickly
+	makeFakeCredF := func(universe string) option.ClientOption {
+		data := []byte(strings.ReplaceAll(fakeCreds, "UNIVERSE", universe))
+		creds, _ := google.CredentialsFromJSON(context.Background(), data, rootTokenScope)
+		return option.WithCredentials(creds)
+	}
+
+	testCases := []struct {
+		description string
+		opts        []option.ClientOption
+		wantErr     bool
+	}{
+		{
+			description: "default creds and no universe",
+			opts: []option.ClientOption{
+				option.WithCredentials(&google.Credentials{}),
+			},
+			wantErr: false,
+		},
+		{
+			description: "default creds and default universe",
+			opts: []option.ClientOption{
+				option.WithCredentials(&google.Credentials{}),
+				option.WithUniverseDomain(defaultUniverse),
+			},
+			wantErr: false,
+		},
+		{
+			description: "default creds and mismatched universe",
+			opts: []option.ClientOption{
+				option.WithCredentials(&google.Credentials{}),
+				option.WithUniverseDomain(otherUniverse),
+			},
+			wantErr: true,
+		},
+		{
+			description: "foreign universe creds and default universe",
+			opts: []option.ClientOption{
+				makeFakeCredF(otherUniverse),
+				option.WithUniverseDomain(defaultUniverse),
+			},
+			wantErr: true,
+		},
+		{
+			description: "foreign universe creds and foreign universe",
+			opts: []option.ClientOption{
+				makeFakeCredF(otherUniverse),
+				option.WithUniverseDomain(otherUniverse),
+			},
+			wantErr: false,
+		},
+		{
+			description: "tokensource + mismatched universe",
+			opts: []option.ClientOption{
+				option.WithTokenSource(oauth2.StaticTokenSource(&oauth2.Token{})),
+				option.WithUniverseDomain(otherUniverse),
+			},
+			wantErr: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		opts := []option.ClientOption{
+			option.WithScopes(rootTokenScope),
+		}
+		opts = append(opts, tc.opts...)
+		_, _, gotErr := NewClient(context.Background(), opts...)
+		if tc.wantErr && gotErr == nil {
+			t.Errorf("%q: wanted error, got none", tc.description)
+		}
+		if !tc.wantErr && gotErr != nil {
+			t.Errorf("%q: wanted success, got err: %v", tc.description, gotErr)
+		}
 	}
 }