pkg/storage/azure: configure registry with workload identity

pkg/storage/azure/azure.go

@@ -406,7 +406,8 @@ func (d *driver) ConfigEnv() (envs envvar.List, err error) {
 	}
 
 	key := cfg.AccountKey
-	if key == "" {
+	federated_token := cfg.FederatedTokenFile
+	if key == "" && federated_token == "" {
 		storageAccountsClient, err := d.storageAccountsClient(cfg, environment)
 		if err != nil {
 			return nil, err
@@ -418,11 +419,30 @@ func (d *driver) ConfigEnv() (envs envvar.List, err error) {
 		}
 	}
 
+	if key != "" {
+		envs = append(envs,
+			envvar.EnvVar{Name: "REGISTRY_STORAGE_AZURE_ACCOUNTKEY", Value: key, Secret: true},
+		)
+	}
+
+	// the AZURE_ vars used to configure workload identity are taken
+	// from https://github.com/distribution/distribution/blob/6a57630cf40122000083e60bcb7e97c50a904c5e/vendor/github.com/Azure/azure-sdk-for-go/sdk/azidentity/default_azure_credential.go#LL86C43-L86C63
+	if federated_token != "" {
+		envs = append(envs,
+			// NOTE: these env vars are not prepended with REGISTRY_STORAGE
+			// because they're exported for the azure-sdk, not the registry.
+			// we do this as a transparent way to support workload identity in the registry.
+			envvar.EnvVar{Name: "AZURE_CLIENT_ID", Value: cfg.ClientID},
+			envvar.EnvVar{Name: "AZURE_TENANT_ID", Value: cfg.TenantID},
+			envvar.EnvVar{Name: "AZURE_FEDERATED_TOKEN_FILE", Value: federated_token},
+			envvar.EnvVar{Name: "AZURE_AUTHORITY_HOST", Value: environment.ActiveDirectoryEndpoint},
+		)
+	}
+
 	envs = append(envs,
 		envvar.EnvVar{Name: "REGISTRY_STORAGE", Value: "azure"},
 		envvar.EnvVar{Name: "REGISTRY_STORAGE_AZURE_CONTAINER", Value: d.Config.Container},
 		envvar.EnvVar{Name: "REGISTRY_STORAGE_AZURE_ACCOUNTNAME", Value: d.Config.AccountName},
-		envvar.EnvVar{Name: "REGISTRY_STORAGE_AZURE_ACCOUNTKEY", Value: key, Secret: true},
 	)
 
 	if d.Config.CloudName != "" {

pkg/storage/azure/azure_test.go

@@ -339,6 +339,83 @@ func TestConfigEnv(t *testing.T) {
 	}
 }
 
+func TestConfigEnvWorkloadIdentity(t *testing.T) {
+	ctx := context.Background()
+
+	config := &imageregistryv1.ImageRegistryConfigStorageAzure{}
+
+	testBuilder := cirofake.NewFixturesBuilder()
+	testBuilder.AddInfraConfig(&configv1.Infrastructure{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "cluster",
+		},
+		Status: configv1.InfrastructureStatus{
+			PlatformStatus: &configv1.PlatformStatus{
+				Type: configv1.AzurePlatformType,
+				Azure: &configv1.AzurePlatformStatus{
+					ResourceGroupName: "resourcegroup",
+					CloudName:         configv1.AzureUSGovernmentCloud,
+				},
+			},
+		},
+	})
+	testBuilder.AddSecrets(&corev1.Secret{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      defaults.CloudCredentialsName,
+			Namespace: defaults.ImageRegistryOperatorNamespace,
+		},
+		Data: map[string][]byte{
+			"azure_client_id":            []byte("client_id"),
+			"azure_federated_token_file": []byte("/path/to/file"),
+			"azure_region":               []byte("region"),
+			"azure_subscription_id":      []byte("subscription_id"),
+			"azure_tenant_id":            []byte("tenant_id"),
+		},
+	})
+
+	listers := testBuilder.BuildListers()
+
+	authorizer := autorest.NullAuthorizer{}
+	sender := mocks.NewSender()
+	sender.AppendResponse(mocks.NewResponseWithContent(`{"nameAvailable":true}`))
+	sender.AppendResponse(mocks.NewResponseWithContent(`?`))
+	sender.AppendResponse(mocks.NewResponseWithContent(`{"name":"account"}`))
+	sender.AppendResponse(mocks.NewResponseWithContent(`{"keys":[{"value":"firstKey"}]}`))
+	sender.AppendResponse(mocks.NewResponseWithContent(`{"keys":[{"value":"firstKey"}]}`))
+	httpSender := pipeline.FactoryFunc(func(next pipeline.Policy, po *pipeline.PolicyOptions) pipeline.PolicyFunc {
+		return func(ctx context.Context, request pipeline.Request) (pipeline.Response, error) {
+			return pipeline.NewHTTPResponse(mocks.NewResponseWithContent(`{}`)), nil
+		}
+	})
+
+	d := NewDriver(ctx, config, &listers.StorageListers)
+	d.authorizer = authorizer
+	d.sender = sender
+	d.httpSender = httpSender
+
+	envvars, err := d.ConfigEnv()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedVars := map[string]interface{}{
+		"REGISTRY_STORAGE":           "azure",
+		"AZURE_CLIENT_ID":            "client_id",
+		"AZURE_TENANT_ID":            "tenant_id",
+		"AZURE_FEDERATED_TOKEN_FILE": "/path/to/file",
+		"AZURE_AUTHORITY_HOST":       "https://login.microsoftonline.com/", // default for configv1.AzureUSGovernmentCloud
+	}
+	for key, value := range expectedVars {
+		e := findEnvVar(envvars, key)
+		if e == nil {
+			t.Fatalf("envvar %s not found, %v", key, envvars)
+		}
+		if e.Value != value {
+			t.Errorf("%s: got %#+v, want %#+v", key, e.Value, value)
+		}
+	}
+}
+
 func TestConfigEnvWithUserKey(t *testing.T) {
 	ctx := context.Background()