kubernetes-sigs · marcosdiez · Nov 1, 2024
diff --git a/apis/elbv2/v1beta1/targetgroupbinding_types.go b/apis/elbv2/v1beta1/targetgroupbinding_types.go
@@ -153,6 +153,14 @@ type TargetGroupBindingSpec struct {
 	// VpcID is the VPC of the TargetGroup. If unspecified, it will be automatically inferred.
 	// +optional
 	VpcID string `json:"vpcID,omitempty"`
+
+	// IAM Role ARN to assume when calling AWS APIs. Useful if the target group is in a different AWS account
+	// +optional
+	IamRoleArnToAssume string `json:"-"` // `json:"iamRoleArnToAssume,omitempty"`
+
+	// IAM Role ARN to assume when calling AWS APIs. Needed to assume a role in another account and prevent the confused deputy problem. https://docs.aws.amazon.com/IAM/latest/UserGuide/confused-deputy.html
+	// +optional
+	AssumeRoleExternalId string `json:"-"` // `json:"assumeRoleExternalId,omitempty"`
 }
 
 // TargetGroupBindingStatus defines the observed state of TargetGroupBinding

diff --git a/controllers/ingress/group_controller.go b/controllers/ingress/group_controller.go
@@ -15,7 +15,7 @@ import (
 	elbv2api "sigs.k8s.io/aws-load-balancer-controller/apis/elbv2/v1beta1"
 	"sigs.k8s.io/aws-load-balancer-controller/controllers/ingress/eventhandlers"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/annotations"
-	"sigs.k8s.io/aws-load-balancer-controller/pkg/aws"
+	"sigs.k8s.io/aws-load-balancer-controller/pkg/aws/services"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/config"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/deploy"
 	elbv2deploy "sigs.k8s.io/aws-load-balancer-controller/pkg/deploy/elbv2"
@@ -43,7 +43,7 @@ const (
 )
 
 // NewGroupReconciler constructs new GroupReconciler
-func NewGroupReconciler(cloud aws.Cloud, k8sClient client.Client, eventRecorder record.EventRecorder,
+func NewGroupReconciler(cloud services.Cloud, k8sClient client.Client, eventRecorder record.EventRecorder,
 	finalizerManager k8s.FinalizerManager, networkingSGManager networkingpkg.SecurityGroupManager,
 	networkingSGReconciler networkingpkg.SecurityGroupReconciler, subnetsResolver networkingpkg.SubnetsResolver,
 	elbv2TaggingManager elbv2deploy.TaggingManager, controllerConfig config.ControllerConfig, backendSGProvider networkingpkg.BackendSGProvider,

diff --git a/controllers/service/service_controller.go b/controllers/service/service_controller.go
@@ -11,7 +11,7 @@ import (
 	"k8s.io/client-go/tools/record"
 	"sigs.k8s.io/aws-load-balancer-controller/controllers/service/eventhandlers"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/annotations"
-	"sigs.k8s.io/aws-load-balancer-controller/pkg/aws"
+	"sigs.k8s.io/aws-load-balancer-controller/pkg/aws/services"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/config"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/deploy"
 	elbv2deploy "sigs.k8s.io/aws-load-balancer-controller/pkg/deploy/elbv2"
@@ -34,7 +34,7 @@ const (
 	controllerName          = "service"
 )
 
-func NewServiceReconciler(cloud aws.Cloud, k8sClient client.Client, eventRecorder record.EventRecorder,
+func NewServiceReconciler(cloud services.Cloud, k8sClient client.Client, eventRecorder record.EventRecorder,
 	finalizerManager k8s.FinalizerManager, networkingSGManager networking.SecurityGroupManager,
 	networkingSGReconciler networking.SecurityGroupReconciler, subnetsResolver networking.SubnetsResolver,
 	vpcInfoProvider networking.VPCInfoProvider, elbv2TaggingManager elbv2deploy.TaggingManager, controllerConfig config.ControllerConfig,

diff --git a/docs/deploy/installation.md b/docs/deploy/installation.md
@@ -7,10 +7,10 @@ The LBC is supported by AWS. Some clusters may be using the legacy "in-tree" fun
 !!!question "Existing AWS ALB Ingress Controller users"
     The AWS ALB Ingress controller must be uninstalled before installing the AWS Load Balancer Controller.
     Please follow our [migration guide](upgrade/migrate_v1_v2.md) to do a migration.
-    
+
 !!!warning "When using AWS Load Balancer Controller v2.5+"
-    The AWS LBC provides a mutating webhook for service resources to set the `spec.loadBalancerClass` field for service of type LoadBalancer on create. 
-    This makes the AWS LBC the **default controller for service** of type LoadBalancer. You can disable this feature and revert to set Cloud Controller Manager (in-tree controller) as the default by setting the helm chart value **enableServiceMutatorWebhook to false** with `--set enableServiceMutatorWebhook=false` . 
+    The AWS LBC provides a mutating webhook for service resources to set the `spec.loadBalancerClass` field for service of type LoadBalancer on create.
+    This makes the AWS LBC the **default controller for service** of type LoadBalancer. You can disable this feature and revert to set Cloud Controller Manager (in-tree controller) as the default by setting the helm chart value **enableServiceMutatorWebhook to false** with `--set enableServiceMutatorWebhook=false` .
     You will no longer be able to provision new Classic Load Balancer (CLB) from your kubernetes service unless you disable this feature. Existing CLB will continue to work fine.
 
 ## Supported Kubernetes versions
@@ -30,7 +30,7 @@ The LBC is supported by AWS. Some clusters may be using the legacy "in-tree" fun
 Isolated clusters are clusters without internet access, and instead reply on VPC endpoints for all required connects.
 When installing the AWS LBC in isolated clusters, you need to disable shield, waf and wafv2 via controller flags `--enable-shield=false, --enable-waf=false, --enable-wafv2=false`
 ### Using the Amazon EC2 instance metadata server version 2 (IMDSv2)
-We recommend blocking the access to instance metadata by requiring the instance to use [IMDSv2](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html) only. For more information, please refer to the AWS guidance [here](https://aws.github.io/aws-eks-best-practices/security/docs/iam/#restrict-access-to-the-instance-profile-assigned-to-the-worker-node). If you are using the IMDSv2, set the hop limit to 2 or higher in order to allow the LBC to perform the metadata introspection. 
+We recommend blocking the access to instance metadata by requiring the instance to use [IMDSv2](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html) only. For more information, please refer to the AWS guidance [here](https://aws.github.io/aws-eks-best-practices/security/docs/iam/#restrict-access-to-the-instance-profile-assigned-to-the-worker-node). If you are using the IMDSv2, set the hop limit to 2 or higher in order to allow the LBC to perform the metadata introspection.
 
 You can set the IMDSv2 as follows:
 ```
@@ -127,6 +127,10 @@ If you're not setting up IAM roles for service accounts, apply the IAM policies
 curl -o iam-policy.json https://raw.githubusercontent.com/kubernetes-sigs/aws-load-balancer-controller/v2.10.0/docs/install/iam_policy.json
 ```
 
+## Special IAM cases
+
+### You only want the LBC to add and remove IPs to already existing target groups:
+
 The following IAM permissions subset is for those using `TargetGroupBinding` only and don't plan to use the LBC to manage security group rules:
 
 ```
@@ -152,6 +156,57 @@ The following IAM permissions subset is for those using `TargetGroupBinding` onl
 }
 ```
 
+### You only want the LBC to add and remove IPs to already existing target groups, also in other accounts, assuming roles
+
+On the other hand, if you plan to use the LBC to manage also target groups in different accounts, you will need to add `"sts:AssumeRole"` to your list of permissions, in other words:
+
+```
+{
+    "Statement": [
+        {
+            "Action": [
+                "ec2:DescribeVpcs",
+                "ec2:DescribeSecurityGroups",
+                "ec2:DescribeInstances",
+                "elasticloadbalancing:DescribeTargetGroups",
+                "elasticloadbalancing:DescribeTargetHealth",
+                "elasticloadbalancing:ModifyTargetGroup",
+                "elasticloadbalancing:ModifyTargetGroupAttributes",
+                "elasticloadbalancing:RegisterTargets",
+                "elasticloadbalancing:DeregisterTargets",
+                "sts:AssumeRole"
+            ],
+            "Effect": "Allow",
+            "Resource": "*"
+        }
+    ],
+    "Version": "2012-10-17"
+}
+```
+
+The assumed roles will need the exactly the same permissions, without `"sts:AssumeRole"`. The assumed role will need a to allow to be assumed by the main role, something like this:
+
+```
+{
+    "Version": "2012-10-17",
+    "Statement": [
+        {
+            "Sid": "",
+            "Effect": "Allow",
+            "Principal": {
+                "AWS": "arn:aws:iam::999999999999999:user/test-alb-controller"
+            },
+            "Action": "sts:AssumeRole",
+            "Condition": {
+                "StringEquals": {
+                    "sts:ExternalId": "very-secret-string"
+                }
+            }
+        }
+    ]
+}
+```
+
 ## Network configuration
 
 Review the [worker nodes security group](https://docs.aws.amazon.com/eks/latest/userguide/sec-group-reqs.html) docs. Your node security group must permit incoming traffic on TCP port 9443 from the Kubernetes control plane. This is needed for webhook access.

diff --git a/docs/guide/targetgroupbinding/spec.md b/docs/guide/targetgroupbinding/spec.md
@@ -52,10 +52,29 @@ Kubernetes meta/v1.ObjectMeta
 </em>
 </td>
 <td>
-Refer to the Kubernetes API documentation for the fields of the
+<table>
+<tr><td><code>annotations</code></td><td>
+
+<table>
+<tr><td><code>alb.ingress.kubernetes.io/IamRoleArnToAssume</code><br><i>string</i></td>
+<td><i>(Optional)</i> In case the target group is in a differet AWS account, you put here the role that needs to be assumed in order to manipulate the target group.
+</td></tr>
+<tr><td><code>alb.ingress.kubernetes.io/AssumeRoleExternalId</code><br><i>string</i></td>
+<td><i>(Optional)</i> The external ID for the assume role operation. Optional, but recommended. It helps you to prevent the <a href="https://docs.aws.amazon.com/IAM/latest/UserGuide/confused-deputy.html" target="_blank">confused deputy problem</a>.
+</td></tr>
+</table>
+
+<tr><td colspan=2>
+Refer to the Kubernetes API documentation for the other fields of the
 <code>metadata</code> field.
+</td></tr>
+</table></td></tr>
+
+
+
 </td>
 </tr>
+
 <tr>
 <td>
 <code>spec</code></br>

diff --git a/docs/guide/targetgroupbinding/targetgroupbinding.md b/docs/guide/targetgroupbinding/targetgroupbinding.md
@@ -92,6 +92,29 @@ spec:
   ...
 ```
 
+### AssumeRole
+
+Sometimes the AWS LoadBalancer controller needs to manipulate target groups from different AWS accounts.
+The way to do that is assuming a role from such account. There are annotations that can help you with that:
+
+* `alb.ingress.kubernetes.io/IamRoleArnToAssume`: the ARN that you need to assume
+* `alb.ingress.kubernetes.io/AssumeRoleExternalId`: the external ID for the assume role operation. Optional, but recommended. It helps you to prevent the confused deputy problem ( https://docs.aws.amazon.com/IAM/latest/UserGuide/confused-deputy.html )
+
+
+## Sample YAML
+
+```yaml
+apiVersion: elbv2.k8s.aws/v1beta1
+kind: TargetGroupBinding
+metadata:
+  name: my-tgb
+  annotations:
+    alb.ingress.kubernetes.io/IamRoleArnToAssume: "arn:aws:iam::999999999999:role/alb-controller-policy-to-assume"
+    alb.ingress.kubernetes.io/AssumeRoleExternalId: "some-magic-string"
+spec:
+  ...
+```
+
 ## MultiCluster Target Group
 TargetGroupBinding CRD supports sharing the same target group ARN among multiple clusters. Setting this flag will ensure the controller only operates on targets within the cluster.
 

diff --git a/go.mod b/go.mod
@@ -56,10 +56,12 @@ require (
 	github.com/ajg/form v1.5.1 // indirect
 	github.com/andybalholm/brotli v1.0.4 // indirect
 	github.com/asaskevich/govalidator v0.0.0-20200428143746-21a406dcc535 // indirect
+	github.com/aws/aws-sdk-go v1.55.5 // indirect
 	github.com/aws/aws-sdk-go-v2/credentials v1.17.27 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/configsources v1.3.22 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.6.22 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/ini v1.8.0 // indirect
+	github.com/aws/aws-sdk-go-v2/service/iam v1.36.3 // indirect
 	github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.11.3 // indirect
 	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.11.17 // indirect
 	github.com/aws/aws-sdk-go-v2/service/sso v1.22.4 // indirect