NE-1323: Add AWS Assume Role ARN API

Adds the ability to specify a Role ARN to create Route 53 DNS
records in a different AWS Account. Supports Shared VPC scenario.

`api/v1beta1/externaldns_types.go`: Add AssumeRole API
`api/v1beta1/webhook_test.go`: Add AssumeRole WebHook Validation test
`api/v1beta1/zz_generated.deepcopy.go`: Generated
`bundle/manifests/externaldns.olm.openshift.io_externaldnses.yaml`:
Generated
`config/crd/bases/externaldns.olm.openshift.io_externaldnses.yaml`:
Generated
`docs/usage.md`: Add section on AWS Assume Role
`pkg/operator/controller/externaldns/credentials_request.go`: Add
sts:AssumeRole to credential requests
`pkg/operator/controller/externaldns/deployment_test.go`: Unit test
`desiredExternalDNSDeployment`
`pkg/operator/controller/externaldns/pod.go`: Add --aws-assume-role
argument with AssumeRole ARN value

api/v1beta1/externaldns_types.go

@@ -257,9 +257,14 @@ type ExternalDNSAWSProviderOptions struct {
 	// +kubebuilder:validation:Required
 	// +required
 	Credentials SecretReference `json:"credentials"`
-	// TODO: Additionally support access for:
-	// - kiam/kube2iam enabled clusters ("iam.amazonaws.com/role" POD's annotation to assume IAM role)
-	// - EKS clusters ("eks.amazonaws.com/role-arn" ServiceAccount's annotation to assume IAM role)
+
+	// assumeRole is a reference to the IAM role that
+	// ExternalDNS will be assuming in order to perform
+	// any DNS updates.
+	//
+	// +kubebuilder:validation:Optional
+	// +optional
+	AssumeRole *ExternalDNSAWSAssumeRoleOptions `json:"assumeRole,omitempty"`
 }
 
 type ExternalDNSGCPProviderOptions struct {
@@ -485,6 +490,15 @@ const (
 	HostnameAnnotationPolicyAllow  HostnameAnnotationPolicy = "Allow"
 )
 
+type ExternalDNSAWSAssumeRoleOptions struct {
+	// arn is an AWS role ARN that the ExternalDNS
+	// operator will assume when making DNS updates.
+	//
+	// +kubebuilder:validation:Required
+	// +required
+	ARN string `json:"arn,omitempty"`
+}
+
 // ExternalDNSServiceSourceOptions describes options
 // specific to the ExternalDNS service source.
 type ExternalDNSServiceSourceOptions struct {

api/v1beta1/externaldns_webhook.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"regexp"
 
+	"github.com/aws/aws-sdk-go/aws/arn"
 	"k8s.io/apimachinery/pkg/runtime"
 
 	utilErrors "k8s.io/apimachinery/pkg/util/errors"
@@ -71,6 +72,7 @@ func (r *ExternalDNS) validate(old runtime.Object) error {
 		r.validateSources(old),
 		r.validateHostnameAnnotationPolicy(),
 		r.validateProviderCredentials(),
+		r.validateAWSRoleARN(),
 	})
 }
 
@@ -156,3 +158,13 @@ func (r *ExternalDNS) validateProviderCredentials() error {
 	}
 	return nil
 }
+
+func (r *ExternalDNS) validateAWSRoleARN() error {
+	// Ensure we have a valid arn if it is specified.
+	provider := r.Spec.Provider
+	if provider.AWS != nil && provider.AWS.AssumeRole != nil && !arn.IsARN(provider.AWS.AssumeRole.ARN) {
+		return fmt.Errorf("arn %q is not a valid AWS ARN", provider.AWS.AssumeRole.ARN)
+	}
+
+	return nil
+}

api/v1beta1/webhook_test.go

@@ -52,6 +52,33 @@ var _ = Describe("ExternalDNS admission webhook when platform is OCP", func() {
 				err := k8sClient.Create(context.Background(), resource)
 				Expect(err).Should(Succeed())
 			})
+			It("valid RoleARN", func() {
+				resource := makeExternalDNS("test-valid-rolearn-openshift", nil)
+				resource.Spec.Provider = ExternalDNSProvider{
+					Type: ProviderTypeAWS,
+					AWS: &ExternalDNSAWSProviderOptions{
+						AssumeRole: &ExternalDNSAWSAssumeRoleOptions{
+							ARN: "arn:aws:iam::123456789012:role/foo",
+						},
+					},
+				}
+				err := k8sClient.Create(context.Background(), resource)
+				Expect(err).Should(Succeed())
+			})
+			It("invalid RoleARN rejected", func() {
+				resource := makeExternalDNS("test-invalid-rolearn-openshift", nil)
+				resource.Spec.Provider = ExternalDNSProvider{
+					Type: ProviderTypeAWS,
+					AWS: &ExternalDNSAWSProviderOptions{
+						AssumeRole: &ExternalDNSAWSAssumeRoleOptions{
+							ARN: "arn:aws:iam:bad123456789012:role/foo",
+						},
+					},
+				}
+				err := k8sClient.Create(context.Background(), resource)
+				Expect(err).ShouldNot(Succeed())
+				Expect(err.Error()).Should(ContainSubstring(`arn "arn:aws:iam:bad123456789012:role/foo" is not a valid AWS ARN`))
+			})
 		})
 		Context("resource with Azure provider", func() {
 			It("ignores when provider Azure credentials are not specified", func() {
@@ -175,6 +202,35 @@ var _ = Describe("ExternalDNS admission webhook", func() {
 			Expect(err).ShouldNot(Succeed())
 			Expect(err.Error()).Should(ContainSubstring("credentials secret must be specified when provider type is AWS"))
 		})
+		It("valid RoleARN", func() {
+			resource := makeExternalDNS("test-valid-rolearn", nil)
+			resource.Spec.Provider = ExternalDNSProvider{
+				Type: ProviderTypeAWS,
+				AWS: &ExternalDNSAWSProviderOptions{
+					AssumeRole: &ExternalDNSAWSAssumeRoleOptions{
+						ARN: "arn:aws:iam::123456789012:role/foo",
+					},
+					Credentials: SecretReference{Name: "credentials"},
+				},
+			}
+			err := k8sClient.Create(context.Background(), resource)
+			Expect(err).Should(Succeed())
+		})
+		It("invalid RoleARN rejected", func() {
+			resource := makeExternalDNS("test-invalid-rolearn", nil)
+			resource.Spec.Provider = ExternalDNSProvider{
+				Type: ProviderTypeAWS,
+				AWS: &ExternalDNSAWSProviderOptions{
+					AssumeRole: &ExternalDNSAWSAssumeRoleOptions{
+						ARN: "arn:aws:iam:bad123456789012:role/foo",
+					},
+					Credentials: SecretReference{Name: "credentials"},
+				},
+			}
+			err := k8sClient.Create(context.Background(), resource)
+			Expect(err).ShouldNot(Succeed())
+			Expect(err.Error()).Should(ContainSubstring(`arn "arn:aws:iam:bad123456789012:role/foo" is not a valid AWS ARN`))
+		})
 	})
 
 	Context("resource with Azure provider", func() {

bundle/manifests/externaldns.olm.openshift.io_externaldnses.yaml

@@ -570,6 +570,16 @@ spec:
                     description: AWS describes provider configuration options specific
                       to AWS (Route 53).
                     properties:
+                      assumeRole:
+                        description: AssumeRole is a reference to the IAM role that
+                          the controller will be assuming in order to perform any
+                          DNS updates.
+                        properties:
+                          arn:
+                            description: ARN is an AWS role ARN that the external-dns
+                              operator will assume when making DNS updates.
+                            type: string
+                        type: object
                       credentials:
                         description: "Credentials is a reference to a secret containing
                           the following keys (with corresponding values): \n * aws_access_key_id

config/crd/bases/externaldns.olm.openshift.io_externaldnses.yaml

@@ -572,6 +572,16 @@ spec:
                     description: AWS describes provider configuration options specific
                       to AWS (Route 53).
                     properties:
+                      assumeRole:
+                        description: AssumeRole is a reference to the IAM role that
+                          the controller will be assuming in order to perform any
+                          DNS updates.
+                        properties:
+                          arn:
+                            description: ARN is an AWS role ARN that the external-dns
+                              operator will assume when making DNS updates.
+                            type: string
+                        type: object
                       credentials:
                         description: "Credentials is a reference to a secret containing
                           the following keys (with corresponding values): \n * aws_access_key_id

docs/usage.md

@@ -14,7 +14,7 @@ provider configuration in the `ExternalDNS` resource. However, it does not provi
 it expects the credentials to be in the same namespace as the operator itself. It then copies over the credentials into
 the namespace where the _external-dns_ deployments are created so that they can be mounted by the pods.
 
-## AWS
+# AWS
 
 Create a secret with the access key id and secret:
 
@@ -55,11 +55,57 @@ spec:
 Once this is created the _external-dns-operator_ will create a deployment of _external-dns_ which is configured to
 manage DNS records in AWS Route53.
 
-## AWS GovCloud
+## Assume Role
+
+The _external-dns-operator_ supports managing records in another AWS account's hosted zone. To achieve this, you will
+require an IAM Role ARN with the necessary permissions properly set up. This Role ARN should then be specified in the
+`ExternalDNS` resource in the following manner:
+
+```yaml
+apiVersion: externaldns.olm.openshift.io/v1beta1
+kind: ExternalDNS
+metadata:
+  name: aws-example
+spec:
+  provider:
+    type: AWS
+    aws:
+      credentials:
+        name: aws-access-key
+      assumeRole:
+        arn: arn:aws:iam::123456789012:role/role-name # Replace with the desire Role ARN
+  zones: # Replace with the desired hosted zone IDs
+    - "Z3URY6TWQ91KXX"
+  source:
+    type: Service
+    fqdnTemplate:
+    - '{{.Name}}.mydomain.net'
+```
+
+**Note**: Due to a limitation of the `v1beta1` API requiring the `credentials` field, OpenShift users will be required
+to provide an empty (`""`) credentials field. The empty credentials will be ignored and the secret provided by
+OpenShift's Cloud Credentials Operator will be used:
+
+```yaml
+apiVersion: externaldns.olm.openshift.io/v1beta1
+kind: ExternalDNS
+metadata:
+  name: aws-example
+spec:
+  provider:
+    type: AWS
+    aws:
+      credentials:
+        name: "" # Empty Credentials
+      assumeRole:
+        arn: arn:aws:iam::123456789012:role/role-name # Replace with the desire Role ARN
+```
+
+## GovCloud
 The operator makes the assumption that `ExternalDNS` instances which target GovCloud DNS also run on the GovCloud. This is needed to detect the AWS region.   
 As for the rest: the usage is exactly the same as for `AWS`.
 
-## Infoblox
+# Infoblox
 
 Before creating an `ExternalDNS` resource for the [Infoblox](https://www.infoblox.com/wp-content/uploads/infoblox-deployment-infoblox-rest-api.pdf)
 the following information is required:
@@ -110,7 +156,7 @@ spec:
 Once this is created the _external-dns-operator_ will create a deployment of _external-dns_ which is configured to
 manage DNS records in Infoblox.
 
-## BlueCat
+# BlueCat
 
 The BlueCat provider requires
 the [BlueCat Gateway](https://docs.bluecatnetworks.com/r/Gateway-Installation-Guide/Installing-BlueCat-Gateway/20.3.1)

pkg/operator/controller/externaldns/credentials_request.go

@@ -248,6 +248,7 @@ func createProviderConfig(externalDNS *operatorv1beta1.ExternalDNS, platformStat
 							"route53:ListHostedZones",
 							"route53:ListResourceRecordSets",
 							"tag:GetResources",
+							"sts:AssumeRole",
 						},
 						Resource: "*",
 					},

pkg/operator/controller/externaldns/credentials_request_test.go

@@ -285,6 +285,7 @@ func desiredAWSProviderSpec() runtime.Object {
 					"route53:ListHostedZones",
 					"route53:ListResourceRecordSets",
 					"tag:GetResources",
+					"sts:AssumeRole",
 				},
 				Resource: "*",
 			},
@@ -311,6 +312,7 @@ func desiredAWSProviderSpecGovARN() runtime.Object {
 					"route53:ListHostedZones",
 					"route53:ListResourceRecordSets",
 					"tag:GetResources",
+					"sts:AssumeRole",
 				},
 				Resource: "*",
 			},

pkg/operator/controller/externaldns/deployment_test.go

@@ -1783,6 +1783,55 @@ func TestDesiredExternalDNSDeployment(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:             "RoleARN set AWS Route",
+			inputExternalDNS: testAWSExternalDNSRoleARN(operatorv1beta1.SourceTypeRoute, "arn:aws:iam:123456789012:role/foo"),
+			expectedTemplatePodSpec: corev1.PodSpec{
+				ServiceAccountName: test.OperandName,
+				NodeSelector: map[string]string{
+					osLabel:             linuxOS,
+					masterNodeRoleLabel: "",
+				},
+				Tolerations: []corev1.Toleration{
+					{
+						Key:      masterNodeRoleLabel,
+						Operator: corev1.TolerationOpExists,
+						Effect:   corev1.TaintEffectNoSchedule,
+					},
+				},
+				Containers: []corev1.Container{
+					{
+						Name:  ExternalDNSContainerName,
+						Image: test.OperandImage,
+						Args: []string{
+							"--aws-assume-role=arn:aws:iam:123456789012:role/foo",
+							"--metrics-address=127.0.0.1:7979",
+							"--txt-owner-id=external-dns-test",
+							"--zone-id-filter=my-dns-public-zone",
+							"--provider=aws",
+							"--source=openshift-route",
+							"--policy=sync",
+							"--registry=txt",
+							"--log-level=debug",
+							"--ignore-hostname-annotation",
+							`--fqdn-template={{""}}`,
+							"--txt-prefix=external-dns-",
+						},
+						SecurityContext: &corev1.SecurityContext{
+							Capabilities: &corev1.Capabilities{
+								Drop: []corev1.Capability{allCapabilities},
+							},
+							Privileged:               pointer.Bool(false),
+							RunAsNonRoot:             pointer.Bool(true),
+							AllowPrivilegeEscalation: pointer.Bool(false),
+							SeccompProfile: &corev1.SeccompProfile{
+								Type: corev1.SeccompProfileTypeRuntimeDefault,
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name:             "Nominal Azure Route",
 			inputSecretName:  azureSecret,
@@ -5317,6 +5366,16 @@ func testAWSExternalDNSDomainFilter(zones []string, source operatorv1beta1.Exter
 	return extdns
 }
 
+func testAWSExternalDNSRoleARN(source operatorv1beta1.ExternalDNSSourceType, roleARN string) *operatorv1beta1.ExternalDNS {
+	extdns := testCreateDNSFromSourceWRTCloudProvider(source, operatorv1beta1.ProviderTypeAWS, nil, "")
+	extdns.Spec.Provider.AWS = &operatorv1beta1.ExternalDNSAWSProviderOptions{
+		AssumeRole: &operatorv1beta1.ExternalDNSAWSAssumeRoleOptions{
+			ARN: roleARN,
+		},
+	}
+	return extdns
+}
+
 func testPlatformStatusGCP(projectID string) *configv1.PlatformStatus {
 	return &configv1.PlatformStatus{
 		Type: configv1.GCPPlatformType,

pkg/operator/controller/externaldns/pod.go

@@ -341,6 +341,10 @@ func (b *externalDNSContainerBuilder) fillAWSFields(container *corev1.Container)
 		container.Args = append(container.Args, "--aws-prefer-cname")
 	}
 
+	if b.externalDNS.Spec.Provider.AWS != nil && b.externalDNS.Spec.Provider.AWS.AssumeRole != nil {
+		container.Args = append(container.Args, fmt.Sprintf("--aws-assume-role=%s", b.externalDNS.Spec.Provider.AWS.AssumeRole.ARN))
+	}
+
 	// don't add empty credentials environment variables if no secret was given
 	if len(b.secretName) == 0 {
 		return