azure_federatedidentity.go

/*
Copyright 2023 The Radius Authors.

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 handlers

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/msi/armmsi"

	"github.com/radius-project/radius/pkg/azure/armauth"
	"github.com/radius-project/radius/pkg/azure/clientv2"
	"github.com/radius-project/radius/pkg/logging"
	rpv1 "github.com/radius-project/radius/pkg/rp/v1"
	"github.com/radius-project/radius/pkg/to"
	"github.com/radius-project/radius/pkg/ucp/resources"
	resources_azure "github.com/radius-project/radius/pkg/ucp/resources/azure"
	"github.com/radius-project/radius/pkg/ucp/ucplog"
)

const (
	// AzureFederatedIdentityAudience represents the Azure AD OIDC target audience.
	AzureFederatedIdentityAudience = "api://AzureADTokenExchange"

	// FederatedIdentityNameKey is the key to represent the federated identity credential name (aka workload identity).
	FederatedIdentityNameKey = "federatedidentityname"
	// FederatedIdentityIssuerKey is the key to represent the oidc issuer.
	FederatedIdentityIssuerKey = "federatedidentityissuer"
	// FederatedIdentitySubjectKey is the key to represent the identity subject.
	FederatedIdentitySubjectKey = "federatedidentitysubject"
)

var (
	// Federated identity is still in preview.
	// The below regions are not supported.
	// Reference: https://learn.microsoft.com/en-us/azure/active-directory/develop/workload-identity-federation-considerations#unsupported-regions-user-assigned-managed-identities
	federatedUnsupportedRegions = []string{
		"Germany North",
		"Sweden South",
		"Sweden Central",
		"Switzerland West",
		"Brazil Southeast",
		"East Asia",
		"Southeast Asia",
		"Switzerland West",
		"South Africa West",
		"Qatar Central",
		"Australia Central",
		"Australia Central2",
		"Norway West",
	}
)

func isFederatedIdentitySupported(region string) bool {
	for _, r := range federatedUnsupportedRegions {
		if strings.EqualFold(r, region) {
			return false
		}
	}
	return true
}

// GetKubeAzureSubject constructs the federated identity subject in the format "system:serviceaccount:<namespace>:<saName>"
// from the given namespace and service account name.
func GetKubeAzureSubject(namespace, saName string) string {
	return fmt.Sprintf("system:serviceaccount:%s:%s", namespace, saName)
}

// NewAzureFederatedIdentity creates a new instance of AzureFederatedIdentityHandler.
func NewAzureFederatedIdentity(arm *armauth.ArmConfig) ResourceHandler {
	return &azureFederatedIdentityHandler{arm: arm}
}

type azureFederatedIdentityHandler struct {
	arm *armauth.ArmConfig
}

// Put creates a federated identity for an Azure AD identity and populates the federated
// identity credential changes.
func (handler *azureFederatedIdentityHandler) Put(ctx context.Context, options *PutOptions) (map[string]string, error) {
	logger := ucplog.FromContextOrDiscard(ctx)

	// Get dependencies
	identityProp, ok := options.DependencyProperties[rpv1.LocalIDUserAssignedManagedIdentity]
	if !ok {
		return nil, errors.New("missing dependency: a user assigned identity is required to create role assignment")
	}

	identityID, err := GetMapValue[string](identityProp, UserAssignedIdentityIDKey)
	if err != nil {
		return nil, errors.New("fails to get identity resource id")
	}

	rs := options.Resource.CreateResource.Data
	federatedName, err := GetMapValue[string](rs, FederatedIdentityNameKey)
	if err != nil {
		return nil, err
	}
	issuer, err := GetMapValue[string](rs, FederatedIdentityIssuerKey)
	if err != nil {
		return nil, err
	}
	subject, err := GetMapValue[string](rs, FederatedIdentitySubjectKey)
	if err != nil {
		return nil, err
	}

	_, err = resources.ParseResource(identityID)
	if err != nil {
		return nil, err
	}

	params := armmsi.FederatedIdentityCredential{
		Properties: &armmsi.FederatedIdentityCredentialProperties{
			Audiences: []*string{to.Ptr(AzureFederatedIdentityAudience)},
			Issuer:    to.Ptr(issuer),
			Subject:   to.Ptr(subject),
		},
	}

	rID, err := resources.ParseResource(identityID)
	if err != nil {
		return nil, err
	}

	subID := rID.FindScope(resources_azure.ScopeSubscriptions)
	rgName := rID.FindScope(resources_azure.ScopeResourceGroups)

	client, err := clientv2.NewFederatedIdentityClient(subID, &handler.arm.ClientOptions)
	if err != nil {
		return nil, err
	}

	// Populating the federated identity credential changes takes some time. Therefore, POD will take some time to start.
	_, err = client.CreateOrUpdate(ctx, rgName, rID.Name(), federatedName, params, nil)
	if err != nil {
		return nil, err
	}

	// WORKAROUND: Ensure that federal identity credential is populated. (Why not they provide async api?)
	response, err := client.Get(ctx, rgName, rID.Name(), federatedName, nil)
	if err != nil {
		return nil, err
	}

	id, err := resources.ParseResource(*response.ID)
	if err != nil {
		return nil, err
	}

	options.Resource.ID = id
	logger.Info("Created federated identity for Azure AD identity.", logging.LogFieldLocalID, rpv1.LocalIDFederatedIdentity)

	return map[string]string{}, nil
}

// Delete deletes the federated identity credential.
//

// azureFederatedIdentityHandler.Delete deletes an Azure Federated Identity resource from the Azure cloud given the
// resource's data and subscription ID.
func (handler *azureFederatedIdentityHandler) Delete(ctx context.Context, options *DeleteOptions) error {
	subscriptionID := options.Resource.ID.FindScope(resources_azure.ScopeSubscriptions)

	client, err := clientv2.NewFederatedIdentityClient(subscriptionID, &handler.arm.ClientOptions)
	if err != nil {
		return err
	}

	// Validate the ID matches the expected type before we start taking it apart to get the names.
	expected := resources.KnownType{
		Types: []resources.TypeSegment{
			{
				Type: "Microsoft.ManagedIdentity/userAssignedIdentities",
				Name: "*",
			},
			{
				Type: "federatedIdentityCredentials",
				Name: "*",
			},
		},
	}
	err = options.Resource.ID.ValidateResourceType(expected)
	if err != nil {
		return err
	}

	typeSegments := options.Resource.ID.TypeSegments()
	_, err = client.Delete(ctx, options.Resource.ID.FindScope(resources_azure.ScopeResourceGroups), typeSegments[0].Name, typeSegments[1].Name, nil)
	return err
}