test: add test coverage for missing permissions

There are multiple issues with missing permission, though they all share
the same KNV2004 error code.
This commit adds test coverage for the following scenarios:
1. A GSA doesn't exist when using gcpserviceaccount
2. A GSA exists, but it is not impersonated with a KSA.
3. A GSA exists and is impersonated, but it doesn't have reader
   permission.
4. A WI+KSA doesn't have reader permission.

e2e/testcases/permission_test.go

@@ -0,0 +1,386 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package e2e
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"kpt.dev/configsync/e2e"
+	"kpt.dev/configsync/e2e/nomostest"
+	"kpt.dev/configsync/e2e/nomostest/ntopts"
+	nomostesting "kpt.dev/configsync/e2e/nomostest/testing"
+	"kpt.dev/configsync/e2e/nomostest/testpredicates"
+	"kpt.dev/configsync/e2e/nomostest/testutils"
+	"kpt.dev/configsync/e2e/nomostest/workloadidentity"
+	"kpt.dev/configsync/pkg/api/configsync"
+	"kpt.dev/configsync/pkg/api/configsync/v1beta1"
+	"kpt.dev/configsync/pkg/core"
+	"kpt.dev/configsync/pkg/importer/filesystem"
+	"kpt.dev/configsync/pkg/kinds"
+	"kpt.dev/configsync/pkg/reconcilermanager/controllers"
+	"kpt.dev/configsync/pkg/status"
+	"kpt.dev/configsync/pkg/testing/fake"
+)
+
+// gsaRestrictedEmail returns a GSA email that has no permissions and no IAM bindings as a WI user.
+func gsaRestrictedEmail() string {
+	return fmt.Sprintf("e2e-test-restricted-user@%s.iam.gserviceaccount.com", *e2e.GCPProject)
+}
+
+// gsaRestrictedImpersonatedEmail returns a GSA email that has no permissions, but has an IAM binding as a WI user.
+func gsaRestrictedImpersonatedEmail() string {
+	return fmt.Sprintf("e2e-test-restricted-wi-user@%s.iam.gserviceaccount.com", *e2e.GCPProject)
+}
+
+const (
+
+	// The exact error message returned for GKE WI is:
+	// credential refresh failed: auth URL returned status 500, body: \"error retrieveing TokenSource.Token: compute: Received 403 `Unable to generate access token; IAM returned 403 Forbidden: Permission 'iam.serviceAccounts.getAccessToken' denied on resource (or it may not exist).\\nThis error could be caused by a missing IAM policy binding on the target IAM service account.\\nFor more information, refer to the Workload Identity documentation:\\n\\thttps://cloud.google.com/kubernetes-engine/docs/how-to/workload-identity#authenticating_to
+	// The exact error message returned for Fleet WI is:
+	// credential refresh failed: auth URL returned status 500, body: \"error retrieveing TokenSource.Token: oauth2/google: status code 403: {\\n  \\\"error\\\": {\\n    \\\"code\\\": 403,\\n    \\\"message\\\": \\\"Permission 'iam.serviceAccounts.getAccessToken' denied on resource (or it may not exist).\\\",\\n    \\\"status\\\": \\\"PERMISSION_DENIED\\\",\\n    \\\"details\\\": [\\n      {\\n        \\\"@type\\\": \\\"type.googleapis.com/google.rpc.ErrorInfo\\\",\\n        \\\"reason\\\": \\\"IAM_PERMISSION_DENIED\\\",\\n        \\\"domain\\\": \\\"iam.googleapis.com\\\",\\n        \\\"metadata\\\": {\\n          \\\"permission\\\": \\\"iam.serviceAccounts.getAccessToken\\\"\\n        }\\n      }\\n    ]\\n  }\\n}\\n\\n\"
+	missingWIBindingError = `Permission 'iam.serviceAccounts.getAccessToken' denied on resource (or it may not exist).`
+
+	// The exact error message returned by CSR is:
+	// remote: PERMISSION_DENIED: The caller does not have permission\\nremote: [type.googleapis.com/google.rpc.RequestInfo]\\nremote: request_id: \\\"6a2759876362432c8d3bb63ad4e45a99\\\"\\nfatal: unable to access 'https://source.developers.google.com/p/stolos-dev/r/kustomize-components/
+	missingCSRPermissionError = "PERMISSION_DENIED: The caller does not have permission"
+
+	// The exact error message returned by AR for the OCI image is:
+	// failed to pull image us-docker.pkg.dev/stolos-dev/config-sync-test-private/kustomize-components:v1: GET https://us-docker.pkg.dev/v2/token?scope=repository%3Astolos-dev%2Fconfig-sync-test-private%2Fkustomize-components%3Apull\u0026service=: DENIED: Permission \"artifactregistry.repositories.downloadArtifacts\" denied on resource \"projects/stolos-dev/locations/us/repositories/config-sync-test-private\" (or it may not exist)
+	missingOCIARPermissionError = `DENIED: Permission \"artifactregistry.repositories.downloadArtifacts\" denied on resource`
+
+	// The exact error message returned by AR for the Helm chart is:
+	// unexpected error rendering chart, will retry","Err":"rendering helm chart: invoking helm: Error: failed to authorize: failed to fetch oauth token: unexpected status from GET request to https://us-docker.pkg.dev/v2/token?scope=repository%3Astolos-dev%2Fconfig-sync-e2e-test--nanyu-cluster-1%2Fcoredns-test-helm-argke-workload-identit%3Apull\u0026service=us-docker.pkg.dev: 403 Forbidden
+	missingHelmARPermissionError = "403 Forbidden"
+
+	// The exact error message for missing GSA is:
+	// metadata: GCE metadata \"instance/service-accounts/default/token?scopes=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcloud-platform\" not defined
+	missingGSAError = "not defined"
+)
+
+func missingGSAEmail() string {
+	return fmt.Sprintf("e2e-test-non-existent-user@%s.iam.gserviceaccount.com", *e2e.GCPProject)
+}
+
+func TestGSAMissingPermissions(t *testing.T) {
+	testCases := []struct {
+		name           string
+		fwiTest        bool
+		sourceType     v1beta1.SourceType
+		AuthType       configsync.AuthType
+		sourceRepo     string
+		sourceChart    string
+		sourceVersion  string
+		gsaEmail       string
+		expectedErrMsg string
+	}{
+		{
+			name:           "GSA - Git source missing GSA for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.GitSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     csrRepo(),
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - OCI source missing GSA for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - Helm source missing GSA for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - Git source missing GSA for Fleet WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.GitSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     csrRepo(),
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - OCI source missing GSA for Fleet WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - Helm source missing GSA for Fleet WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       missingGSAEmail(),
+			expectedErrMsg: missingGSAError,
+		},
+		{
+			name:           "GSA - Git source missing IAM binding for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.GitSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     csrRepo(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - OCI source missing IAM binding for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - Helm source missing IAM binding for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - Git source missing IAM binding for Fleet WI",
+			fwiTest:        true,
+			sourceType:     v1beta1.GitSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     csrRepo(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - OCI source missing IAM binding for Fleet WI",
+			fwiTest:        true,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - Helm source missing IAM binding for Fleet WI",
+			fwiTest:        true,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingWIBindingError,
+		},
+		{
+			name:           "GSA - Git source with IAM binding for GKE WI, but missing reader permission",
+			fwiTest:        false,
+			sourceType:     v1beta1.GitSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     csrRepo(),
+			gsaEmail:       gsaRestrictedImpersonatedEmail(),
+			expectedErrMsg: missingCSRPermissionError,
+		},
+		{
+			name:           "GSA - OCI source with IAM binding for GKE WI, but missing reader permission",
+			fwiTest:        false,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       gsaRestrictedImpersonatedEmail(),
+			expectedErrMsg: missingOCIARPermissionError,
+		},
+		{
+			name:           "GSA - Helm source with IAM binding for GKE WI, but missing reader permission",
+			fwiTest:        false,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       gsaRestrictedImpersonatedEmail(),
+			expectedErrMsg: missingHelmARPermissionError,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			nt := nomostest.New(t, nomostesting.WorkloadIdentity, ntopts.Unstructured, ntopts.RequireGKE(t))
+			rs := fake.RootSyncObjectV1Beta1(configsync.RootSyncName)
+			tenant := "tenant-a"
+
+			if err := workloadidentity.ValidateEnabled(nt); err != nil {
+				nt.T.Fatal(err)
+			}
+
+			mustConfigureMembership(nt, tc.fwiTest, false)
+
+			spec := &sourceSpec{
+				sourceType:    tc.sourceType,
+				sourceRepo:    tc.sourceRepo,
+				sourceChart:   tc.sourceChart,
+				sourceVersion: tc.sourceVersion,
+				gsaEmail:      tc.gsaEmail,
+			}
+			mustConfigureRootSync(nt, rs, tenant, spec)
+			nt.WaitForRootSyncSourceError(rs.Name, status.SourceErrorCode, tc.expectedErrMsg)
+		})
+	}
+
+}
+
+func TestKSAMissingReaderPermission(t *testing.T) {
+	testCases := []struct {
+		name           string
+		fwiTest        bool
+		sourceType     v1beta1.SourceType
+		AuthType       configsync.AuthType
+		sourceRepo     string
+		sourceChart    string
+		sourceVersion  string
+		gsaEmail       string
+		expectedErrMsg string
+	}{
+		{
+			name:           "WI-KSA - OCI source missing permission for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingOCIARPermissionError,
+		},
+		{
+			name:           "WI-KSA - Helm source missing permission for GKE WI",
+			fwiTest:        false,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingHelmARPermissionError,
+		},
+		{
+			name:           "WI-KSA - OCI source missing permission for Fleet WI",
+			fwiTest:        true,
+			sourceType:     v1beta1.OciSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceRepo:     privateARImage(),
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingOCIARPermissionError,
+		},
+		{
+			name:           "WI-KSA - Helm source missing permission for Fleet WI",
+			fwiTest:        true,
+			sourceType:     v1beta1.HelmSource,
+			AuthType:       configsync.AuthGCPServiceAccount,
+			sourceVersion:  privateCoreDNSHelmChartVersion,
+			sourceChart:    privateCoreDNSHelmChart,
+			gsaEmail:       gsaRestrictedEmail(),
+			expectedErrMsg: missingHelmARPermissionError,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			nt := nomostest.New(t, nomostesting.WorkloadIdentity,
+				ntopts.Unstructured,
+				ntopts.RequireGKE(t))
+
+			if err := workloadidentity.ValidateEnabled(nt); err != nil {
+				nt.T.Fatal(err)
+			}
+			mustConfigureMembership(nt, tc.fwiTest, false)
+
+			// Add another RootSync (rs-byoid) to the `root-sync` Rootsync.
+			rs := fake.RootSyncObjectV1Beta1("rs-byoid")
+			syncDir := "tenant"
+			rs.Spec.SourceFormat = string(filesystem.SourceFormatUnstructured)
+			rs.Spec.SourceType = string(tc.sourceType)
+			spec := &sourceSpec{
+				sourceType:    tc.sourceType,
+				sourceRepo:    tc.sourceRepo,
+				sourceChart:   tc.sourceChart,
+				sourceVersion: tc.sourceVersion,
+				gsaEmail:      tc.gsaEmail,
+			}
+			if err := pushSource(nt, spec); err != nil {
+				nt.T.Fatal(err)
+			}
+			switch tc.sourceType {
+			case v1beta1.OciSource:
+				rs.Spec.Oci = &v1beta1.Oci{
+					Image: spec.sourceRepo,
+					Dir:   syncDir,
+					Auth:  configsync.AuthK8sServiceAccount,
+				}
+			case v1beta1.HelmSource:
+				rs.Spec.Helm = &v1beta1.HelmRootSync{
+					HelmBase: v1beta1.HelmBase{
+						Repo:        spec.sourceRepo,
+						Chart:       spec.sourceChart,
+						Version:     spec.sourceVersion,
+						ReleaseName: "my-coredns",
+						Period:      metav1.Duration{},
+						Auth:        configsync.AuthK8sServiceAccount,
+					},
+					Namespace: "coredns",
+				}
+			}
+			nt.Must(nt.RootRepos[configsync.RootSyncName].Add("acme/rs-byoid.yaml", rs))
+			nt.Must(nt.RootRepos[configsync.RootSyncName].CommitAndPush("Add a RootSync with restricted k8sserviceaccount"))
+
+			ksaRef := types.NamespacedName{
+				Namespace: configsync.ControllerNamespace,
+				Name:      core.RootReconcilerName(rs.Name),
+			}
+			require.NoError(nt.T,
+				nt.WatchForSync(kinds.RootSyncV1Beta1(), configsync.RootSyncName, configsync.ControllerNamespace,
+					nomostest.DefaultRootSha1Fn, nomostest.RootSyncHasStatusSyncCommit, nil),
+			)
+			require.NoError(nt.T,
+				nt.Watcher.WatchObject(kinds.ServiceAccount(), ksaRef.Name, ksaRef.Namespace, []testpredicates.Predicate{
+					testpredicates.MissingAnnotation(controllers.GCPSAAnnotationKey),
+				}))
+			if tc.fwiTest {
+				nt.T.Log("Validate the serviceaccount_impersonation_url is absent from the injected FWI credentials")
+				nomostest.Wait(nt.T, "wait for FWI credentials to exist", nt.DefaultWaitTimeout, func() error {
+					return testutils.ReconcilerPodHasFWICredsAnnotation(nt, nomostest.DefaultRootReconcilerName, "", configsync.AuthK8sServiceAccount)
+				})
+			}
+
+			nt.WaitForRootSyncSourceError(rs.Name, status.SourceErrorCode, tc.expectedErrMsg)
+		})
+	}
+
+}