Added support to assert against exact instance IDs

**Problem**
* To support cross-account DHC discovery, we need to add terraform configurations and tests to test against live AWS data.
* However, there was nothing in place to support any AssumeRole testing, irrespective of cross-account.

**Solution**
* Added a new terraform file, iam_assume_role.tf, to contain the new terraform configurations for single-account AssumeRole and cross-role
* Added a second terraform file, iam_cross_account.tf, to contain the new terraform configurations for cross-account
* Refactored how the tests are organized. The previous static test cases used a system where a separate function was created for each test. This was moved to a dedicated file, e2e_host_static_test.go.
* For AssumeRole tests (single account, cross role, and cross account), this system wasn't ideal since there are so many test cases and they are all extremely similar. A table driven system was better that passed in a set of variables to shared test helpers. A dedicated file, e2e_host_assumerole_test.go, was created to contain the testing infrastructure for AssumeRole tests.
* e2e_host_test.go remains the main test runner that then calls e2e_host_assumerole_test.go and e2e_host_static_test.go
* The terraform tests work by setting environment variables for the AWS account that you want to configure the terraform for. The existing setup worked for single-account and cross-role. However, to support cross-account, support had to be added for a second set of credentials. The second set of environment variables can now be set with the TARGET_ prefix. Some configuration in testing.go had to be added to support creating/destroying multiple terraform setups.

**Testing**
* The single account tests pass as expected. However, a bug was discovered during this process that will be addressed later.
* The cross-role and cross-account tests failed as expected because this featured has not yet been delivered.
* It was noticed that some of the existing static tests were flaky. The problem and fix were identified and will be addressed later.

README.md

@@ -25,6 +25,8 @@ Credential rotation can be turned off by setting the
 This plugin will attempt to assume a role when a `role_arn` is supplied through the
 `attributes` object. More information about assume an AWS role can be found [here](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html). This feature only works when the plugin is running on a self managed Boundary [worker](https://developer.hashicorp.com/boundary/tutorials/hcp-administration/hcp-manage-workers).
 
+To discover hosts across multiple AWS accounts, supply a `target_role_arn` in addition to `role_arn`. The plugin uses the principal credentials to assume the target role via a two-hop `AssumeRole` chain, enabling cross-account host discovery from a single worker. See [Attributes and Secrets](plugin/service/host/README.md#attributes-and-secrets) for the full list of `target_*` attributes.
+
 ### Environment Credentials
 
 This plugin will attempt to retrieve credentials from environment variables. More

go.mod

@@ -4,6 +4,7 @@ go 1.25.7
 
 require (
 	github.com/aws/aws-sdk-go-v2 v1.41.7
+	github.com/aws/aws-sdk-go-v2/credentials v1.17.46
 	github.com/aws/aws-sdk-go-v2/service/ec2 v1.254.0
 	github.com/aws/aws-sdk-go-v2/service/iam v1.47.6
 	github.com/aws/aws-sdk-go-v2/service/s3 v1.101.0
@@ -26,7 +27,6 @@ require (
 	github.com/apparentlymart/go-textseg/v15 v15.0.0 // indirect
 	github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.7.10 // indirect
 	github.com/aws/aws-sdk-go-v2/config v1.28.5 // indirect
-	github.com/aws/aws-sdk-go-v2/credentials v1.17.46 // indirect
 	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.16.20 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.23 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.23 // indirect

internal/credential/attributes.go

@@ -186,3 +186,63 @@ func GetCredentialAttributes(in *structpb.Struct) (*CredentialAttributes, error)
 		RoleTags:                  roleTags,
 	}, nil
 }
+
+// GetTargetCredentialAttributes parses values out of a protobuf struct input and returns a CredentialAttributes used
+// for configuring a second AWS session. target_role_arn is required when parsing target credentials.
+// A status error is returned with an InvalidArgument code when target account attributes are missing
+// required values or have invalid value types.
+func GetTargetCredentialAttributes(in *structpb.Struct) (*CredentialAttributes, error) {
+	badFields := make(map[string]string)
+
+	// Parse the role ARN of the target account to AssumeRole into.
+	targetRoleArn, err := values.GetStringValue(in, ConstTargetRoleArn, true)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstTargetRoleArn)] = err.Error()
+	}
+
+	// try parsing target_region, fallback to region, adds target_region to bad fields only when malformed since not required
+	targetRegion, err := values.GetStringValue(in, ConstTargetRegion, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstTargetRegion)] = err.Error()
+	}
+	if targetRegion == "" {
+		targetRegion, err = values.GetStringValue(in, ConstRegion, true) // region is required for processing
+		if err != nil {
+			badFields[fmt.Sprintf("attributes.%s", ConstRegion)] = err.Error()
+		}
+	}
+
+	// the remaining fields are optional and only raise errors when malformed
+	disableCredentialRotation, err := values.GetBoolValue(in, ConstDisableCredentialRotation, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstDisableCredentialRotation)] = err.Error()
+	}
+
+	targetRoleExternalId, err := values.GetStringValue(in, ConstTargetRoleExternalId, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstTargetRoleExternalId)] = err.Error()
+	}
+
+	targetRoleSessionName, err := values.GetStringValue(in, ConstTargetRoleSessionName, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstTargetRoleSessionName)] = err.Error()
+	}
+
+	targetRoleTags, err := values.GetMapStringString(in, ConstTargetRoleTags, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstTargetRoleTags)] = err.Error()
+	}
+
+	if len(badFields) > 0 {
+		return nil, errors.InvalidArgumentError("Error in the attributes provided", badFields)
+	}
+
+	return &CredentialAttributes{
+		Region:                    targetRegion,
+		DisableCredentialRotation: disableCredentialRotation,
+		RoleArn:                   targetRoleArn,
+		RoleExternalId:            targetRoleExternalId,
+		RoleSessionName:           targetRoleSessionName,
+		RoleTags:                  targetRoleTags,
+	}, nil
+}

internal/credential/attributes_test.go

@@ -101,6 +101,232 @@ func TestGetCredentialAttributes(t *testing.T) {
 	}
 }
 
+func TestGetTargetCredentialAttributes(t *testing.T) {
+	const targetRoleArn = "arn:aws:iam::222222222222:role/Target"
+
+	cases := []struct {
+		name                string
+		in                  map[string]any
+		expected            *CredentialAttributes
+		expectedErrContains string
+	}{
+		{
+			name: "missing target_role_arn",
+			in: map[string]any{
+				ConstRegion: "us-west-2",
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name:                "missing target_role_arn and region",
+			in:                  map[string]any{},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "empty target_role_arn",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRoleArn: "",
+			},
+			expectedErrContains: "attributes.target_role_arn: value \"target_role_arn\" cannot be empty",
+		},
+		{
+			name: "wrong type target_role_arn",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRoleArn: true,
+			},
+			expectedErrContains: "attributes.target_role_arn: unexpected type for value \"target_role_arn\": want string, got bool",
+		},
+		{
+			name: "target_region without target_role_arn",
+			in: map[string]any{
+				ConstRegion:       "us-west-2",
+				ConstTargetRegion: "eu-west-1",
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "other target fields without target_role_arn",
+			in: map[string]any{
+				ConstRegion:                "us-west-2",
+				ConstTargetRoleExternalId:  "ext",
+				ConstTargetRoleSessionName: "sess",
+				ConstTargetRoleTags:        map[string]any{"k": "v"},
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "target_role_arn uses region when target_region omitted",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRoleArn: targetRoleArn,
+			},
+			expected: &CredentialAttributes{
+				Region:  "us-west-2",
+				RoleArn: targetRoleArn,
+			},
+		},
+		{
+			name: "target_role_arn without target_region or region",
+			in: map[string]any{
+				ConstTargetRoleArn: targetRoleArn,
+			},
+			expectedErrContains: "missing required value \"region\"",
+		},
+		{
+			name: "target_region overrides region",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRegion:  "eu-west-1",
+				ConstTargetRoleArn: targetRoleArn,
+			},
+			expected: &CredentialAttributes{
+				Region:  "eu-west-1",
+				RoleArn: targetRoleArn,
+			},
+		},
+		{
+			name: "empty target_region falls back to region",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRegion:  "",
+				ConstTargetRoleArn: targetRoleArn,
+			},
+			expected: &CredentialAttributes{
+				Region:  "us-west-2",
+				RoleArn: targetRoleArn,
+			},
+		},
+		{
+			name: "all optional target fields",
+			in: map[string]any{
+				ConstRegion:                    "us-west-2",
+				ConstDisableCredentialRotation: true,
+				ConstTargetRoleArn:             targetRoleArn,
+				ConstTargetRegion:              "eu-west-1",
+				ConstTargetRoleExternalId:      "target-ext",
+				ConstTargetRoleSessionName:     "target-sess",
+				ConstTargetRoleTags:            map[string]any{"env": "target"},
+			},
+			expected: &CredentialAttributes{
+				Region:                    "eu-west-1",
+				DisableCredentialRotation: true,
+				RoleArn:                   targetRoleArn,
+				RoleExternalId:            "target-ext",
+				RoleSessionName:           "target-sess",
+				RoleTags:                  map[string]string{"env": "target"},
+			},
+		},
+		{
+			name: "optional target fields omitted do not copy principal role fields",
+			in: map[string]any{
+				ConstRegion:          "us-west-2",
+				ConstRoleArn:         "arn:aws:iam::111111111111:role/Principal",
+				ConstRoleExternalId:  "principal-ext",
+				ConstRoleSessionName: "principal-sess",
+				ConstRoleTags:        map[string]any{"env": "principal"},
+				ConstTargetRoleArn:   targetRoleArn,
+			},
+			expected: &CredentialAttributes{
+				Region:  "us-west-2",
+				RoleArn: targetRoleArn,
+			},
+		},
+		{
+			name: "disable_credential_rotation false is copied",
+			in: map[string]any{
+				ConstRegion:                    "us-west-2",
+				ConstDisableCredentialRotation: false,
+				ConstTargetRoleArn:             targetRoleArn,
+			},
+			expected: &CredentialAttributes{
+				Region:                    "us-west-2",
+				DisableCredentialRotation: false,
+				RoleArn:                   targetRoleArn,
+			},
+		},
+		{
+			name: "wrong type target_region",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRoleArn: targetRoleArn,
+				ConstTargetRegion:  true,
+			},
+			expectedErrContains: "attributes.target_region: unexpected type for value \"target_region\": want string, got bool",
+		},
+		{
+			name: "wrong type target_role_external_id",
+			in: map[string]any{
+				ConstRegion:               "us-west-2",
+				ConstTargetRoleArn:        targetRoleArn,
+				ConstTargetRoleExternalId: true,
+			},
+			expectedErrContains: "attributes.target_role_external_id: unexpected type for value \"target_role_external_id\": want string, got bool",
+		},
+		{
+			name: "wrong type target_role_session_name",
+			in: map[string]any{
+				ConstRegion:                "us-west-2",
+				ConstTargetRoleArn:         targetRoleArn,
+				ConstTargetRoleSessionName: true,
+			},
+			expectedErrContains: "attributes.target_role_session_name: unexpected type for value \"target_role_session_name\": want string, got bool",
+		},
+		{
+			name: "wrong type target_role_tags",
+			in: map[string]any{
+				ConstRegion:         "us-west-2",
+				ConstTargetRoleArn:  targetRoleArn,
+				ConstTargetRoleTags: true,
+			},
+			expectedErrContains: "attributes.target_role_tags: unexpected type for value \"target_role_tags\": want map[string]string, got bool",
+		},
+		{
+			name: "wrong type target_role_tag value",
+			in: map[string]any{
+				ConstRegion:        "us-west-2",
+				ConstTargetRoleArn: targetRoleArn,
+				ConstTargetRoleTags: map[string]any{
+					"env": true,
+				},
+			},
+			expectedErrContains: `unexpected type for value in map["env"]: want string, got bool`,
+		},
+		{
+			name: "wrong type disable_credential_rotation",
+			in: map[string]any{
+				ConstRegion:                    "us-west-2",
+				ConstTargetRoleArn:             targetRoleArn,
+				ConstDisableCredentialRotation: "sure",
+			},
+			expectedErrContains: "attributes.disable_credential_rotation: unexpected type for value \"disable_credential_rotation\": want bool, got string",
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			require := require.New(t)
+
+			input, err := structpb.NewStruct(tc.in)
+			require.NoError(err)
+
+			actual, err := GetTargetCredentialAttributes(input)
+			if tc.expectedErrContains != "" {
+				require.Error(err)
+				require.Nil(actual)
+				require.Contains(err.Error(), tc.expectedErrContains)
+				require.Equal(codes.InvalidArgument, status.Code(err))
+				return
+			}
+
+			require.NoError(err)
+			require.Equal(tc.expected, actual)
+		})
+	}
+}
+
 func TestGetCredentialsConfig(t *testing.T) {
 	cases := []struct {
 		name                string

internal/credential/const.go

@@ -4,10 +4,10 @@
 package credential
 
 const (
-	// ConstAccessKey is the key for the region in the aws credentials.
+	// ConstRegion is the key for the region in the aws credentials.
 	ConstRegion = "region"
 
-	// ConstAccessKey is the key for the access key id in the aws credentials.
+	// ConstAccessKeyId is the key for the access key id in the aws credentials.
 	ConstAccessKeyId = "access_key_id"
 
 	// ConstSecretAccessKey is the key for the secret access key in the aws credentials.
@@ -30,4 +30,19 @@ const (
 
 	// ConstRoleTags is the key for the tags used for assuming a IAM role.
 	ConstRoleTags = "role_tags"
+
+	// ConstTargetRegion is the key for the region of the target account in the aws credentials.
+	ConstTargetRegion = "target_region"
+
+	// ConstTargetRoleArn is the key for assuming a IAM role for the target account.
+	ConstTargetRoleArn = "target_role_arn"
+
+	// ConstTargetRoleExternalId is the key for the external id used for assuming a IAM role for the target account.
+	ConstTargetRoleExternalId = "target_role_external_id"
+
+	// ConstTargetRoleSessionName is the key for the session name used for assuming a IAM role of the target account.
+	ConstTargetRoleSessionName = "target_role_session_name"
+
+	// ConstTargetRoleTags is the key for the tags used for assuming a IAM role of the target account.
+	ConstTargetRoleTags = "target_role_tags"
 )

plugin/service/host/README.md

@@ -109,13 +109,23 @@ The following `attributes` are valid on an AWS host catalog resource:
 - `region` (string): The region to configure the host catalog for. All host sets
   in this catalog will be configured for this region.
 - `role_arn` (string): The AWS Role ARN used for `AssumeRole` authentication. If
-  provided, `disable_credential_rotation` must be also set to `true.
-- `role_external_id` (string):  The external id configured for the `AssumeRole`
+  provided, `disable_credential_rotation` must be also set to `true`.
+- `role_external_id` (string): The external ID configured for the principal `AssumeRole`
   provider.
-- `role_session_name` (string): The session name configured for the `AssumeRole`
+- `role_session_name` (string): The session name configured for the principal `AssumeRole`
   provider.
-- `role_tags` (object): The key-value pair tags configured for the `AssumeRole`
+- `role_tags` (object): The key-value pair tags configured for the principal `AssumeRole`
   provider.
+- `target_role_arn` (string): The AWS role ARN of the target IAM role to assume for
+  cross-account discovery. Required if any other `target_*` attributes are configured.
+- `target_region` (string): The region where the target hosts reside. Defaults to the
+  principal account `region` if omitted.
+- `target_role_external_id` (string): The external ID configured for the target
+  `AssumeRole` provider.
+- `target_role_session_name` (string): The session name configured for the target
+  `AssumeRole` provider.
+- `target_role_tags` (object): The key-value pair tags configured for the target
+  `AssumeRole` provider.
 
 The following `secrets` are required on an AWS host catalog resource:
 

plugin/service/host/attributes.go

@@ -20,6 +20,9 @@ import (
 type CatalogAttributes struct {
 	*cred.CredentialAttributes
 
+	// TargetAccount optionally holds the credentials used to AssumeRole into a second, affiliated account when provided.
+	TargetAccount *cred.CredentialAttributes
+
 	// DualStack is used for configuring how the aws client will resolve requests.
 	DualStack bool
 
@@ -39,6 +42,14 @@ func getCatalogAttributes(in *structpb.Struct) (*CatalogAttributes, error) {
 		return nil, err
 	}
 
+	var targetCredAttributes *cred.CredentialAttributes
+	if hasTargetAccountAttributes(in) {
+		targetCredAttributes, err = cred.GetTargetCredentialAttributes(in)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	dualStack, err := values.GetBoolValue(in, ConstAwsDualStack, false)
 	if err != nil {
 		badFields[fmt.Sprintf("attributes.%s", ConstAwsDualStack)] = err.Error()
@@ -66,6 +77,16 @@ func getCatalogAttributes(in *structpb.Struct) (*CatalogAttributes, error) {
 			continue
 		case cred.ConstRoleTags:
 			continue
+		case cred.ConstTargetRegion:
+			continue
+		case cred.ConstTargetRoleArn:
+			continue
+		case cred.ConstTargetRoleExternalId:
+			continue
+		case cred.ConstTargetRoleSessionName:
+			continue
+		case cred.ConstTargetRoleTags:
+			continue
 		default:
 			badFields[fmt.Sprintf("attributes.%s", s)] = "unrecognized field"
 		}
@@ -77,6 +98,7 @@ func getCatalogAttributes(in *structpb.Struct) (*CatalogAttributes, error) {
 
 	return &CatalogAttributes{
 		CredentialAttributes:  credAttributes,
+		TargetAccount:         targetCredAttributes,
 		DualStack:             dualStack,
 		InstanceAddressesOnly: instanceAddressesOnly,
 	}, nil
@@ -121,3 +143,19 @@ func getSetAttributes(in *structpb.Struct) (*SetAttributes, error) {
 
 	return &setAttrs, nil
 }
+
+func hasTargetAccountAttributes(in *structpb.Struct) bool {
+	fields := in.GetFields()
+
+	_, hasTargetRegion := fields[cred.ConstTargetRegion]
+	_, hasTargetRoleArn := fields[cred.ConstTargetRoleArn]
+	_, hasTargetRoleExternalID := fields[cred.ConstTargetRoleExternalId]
+	_, hasTargetRoleSessionName := fields[cred.ConstTargetRoleSessionName]
+	_, hasTargetRoleTags := fields[cred.ConstTargetRoleTags]
+
+	return hasTargetRegion ||
+		hasTargetRoleArn ||
+		hasTargetRoleExternalID ||
+		hasTargetRoleSessionName ||
+		hasTargetRoleTags
+}

plugin/service/host/attributes_test.go

@@ -118,6 +118,170 @@ func TestGetCatalogAttributes(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "target_region without target_role_arn",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":        structpb.NewStringValue("us-west-2"),
+					"target_region": structpb.NewStringValue("eu-west-1"),
+				},
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "target role field without target_role_arn",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":                  structpb.NewStringValue("us-west-2"),
+					"target_role_external_id": structpb.NewStringValue("target-ext"),
+				},
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "other target role fields without target_role_arn",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":                   structpb.NewStringValue("us-west-2"),
+					"target_role_session_name": structpb.NewStringValue("target-session"),
+					"target_role_tags": structpb.NewStructValue(&structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							"env": structpb.NewStringValue("target"),
+						},
+					}),
+				},
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+		},
+		{
+			name: "empty target_role_arn with target_region",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":          structpb.NewStringValue("us-west-2"),
+					"target_role_arn": structpb.NewStringValue(""),
+					"target_region":   structpb.NewStringValue("eu-west-1"),
+				},
+			},
+			expectedErrContains: "attributes.target_role_arn: value \"target_role_arn\" cannot be empty",
+		},
+		{
+			name: "target_role_arn without target_region uses region; principal sts fields are not copied",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":                      structpb.NewStringValue("us-west-2"),
+					"disable_credential_rotation": structpb.NewBoolValue(true),
+					"role_arn":                    structpb.NewStringValue("arn:aws:iam::111111111111:role/Principal"),
+					"role_external_id":            structpb.NewStringValue("principal-ext"),
+					"role_session_name":           structpb.NewStringValue("principal-sess"),
+					"role_tags": structpb.NewStructValue(&structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							"env": structpb.NewStringValue("principal"),
+						},
+					}),
+					"target_role_arn": structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+				},
+			},
+			expected: &CatalogAttributes{
+				CredentialAttributes: &cred.CredentialAttributes{
+					Region:                    "us-west-2",
+					DisableCredentialRotation: true,
+					RoleArn:                   "arn:aws:iam::111111111111:role/Principal",
+					RoleExternalId:            "principal-ext",
+					RoleSessionName:           "principal-sess",
+					RoleTags: map[string]string{
+						"env": "principal",
+					},
+				},
+				TargetAccount: &cred.CredentialAttributes{
+					Region:                    "us-west-2",
+					DisableCredentialRotation: true,
+					RoleArn:                   "arn:aws:iam::222222222222:role/Target",
+				},
+			},
+		},
+		{
+			name: "target attributes are independent of principal",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":                      structpb.NewStringValue("us-west-2"),
+					"disable_credential_rotation": structpb.NewBoolValue(true),
+					"role_arn":                    structpb.NewStringValue("arn:aws:iam::111111111111:role/Principal"),
+					"role_external_id":            structpb.NewStringValue("principal-ext"),
+					"role_session_name":           structpb.NewStringValue("principal-sess"),
+					"role_tags": structpb.NewStructValue(&structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							"env": structpb.NewStringValue("principal"),
+						},
+					}),
+					"target_role_arn":          structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+					"target_region":            structpb.NewStringValue("eu-west-1"),
+					"target_role_external_id":  structpb.NewStringValue("target-ext"),
+					"target_role_session_name": structpb.NewStringValue("target-sess"),
+					"target_role_tags": structpb.NewStructValue(&structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							"env": structpb.NewStringValue("target"),
+						},
+					}),
+				},
+			},
+			expected: &CatalogAttributes{
+				CredentialAttributes: &cred.CredentialAttributes{
+					Region:                    "us-west-2",
+					DisableCredentialRotation: true,
+					RoleArn:                   "arn:aws:iam::111111111111:role/Principal",
+					RoleExternalId:            "principal-ext",
+					RoleSessionName:           "principal-sess",
+					RoleTags: map[string]string{
+						"env": "principal",
+					},
+				},
+				TargetAccount: &cred.CredentialAttributes{
+					Region:                    "eu-west-1",
+					DisableCredentialRotation: true,
+					RoleArn:                   "arn:aws:iam::222222222222:role/Target",
+					RoleExternalId:            "target-ext",
+					RoleSessionName:           "target-sess",
+					RoleTags: map[string]string{
+						"env": "target",
+					},
+				},
+			},
+		},
+		{
+			name: "catalog dual_stack and instance_addresses_only with target",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":                  structpb.NewStringValue("us-west-2"),
+					"dual_stack":              structpb.NewBoolValue(true),
+					"instance_addresses_only": structpb.NewBoolValue(true),
+					"target_role_arn":         structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+				},
+			},
+			expected: &CatalogAttributes{
+				CredentialAttributes: &credential.CredentialAttributes{
+					Region:                    "us-west-2",
+					DisableCredentialRotation: false,
+				},
+				TargetAccount: &cred.CredentialAttributes{
+					Region:                    "us-west-2",
+					DisableCredentialRotation: false,
+					RoleArn:                   "arn:aws:iam::222222222222:role/Target",
+				},
+				DualStack:             true,
+				InstanceAddressesOnly: true,
+			},
+		},
+		{
+			name: "unknown field with target_role_arn",
+			in: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"region":          structpb.NewStringValue("us-west-2"),
+					"target_role_arn": structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+					"foo":             structpb.NewBoolValue(true),
+				},
+			},
+			expectedErrContains: "attributes.foo: unrecognized field",
+		},
 	}
 
 	for _, tc := range cases {

plugin/service/host/plugin.go

@@ -5,12 +5,17 @@ package host
 
 import (
 	"context"
+	goerrors "errors"
 	"fmt"
 	"strings"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/credentials/stscreds"
 	"github.com/aws/aws-sdk-go-v2/service/ec2"
 	"github.com/aws/aws-sdk-go-v2/service/ec2/types"
+	"github.com/aws/aws-sdk-go-v2/service/sts"
+	stsTypes "github.com/aws/aws-sdk-go-v2/service/sts/types"
+	"github.com/aws/smithy-go"
 	"github.com/hashicorp/boundary-plugin-aws/internal/credential"
 	"github.com/hashicorp/boundary-plugin-aws/internal/errors"
 	pb "github.com/hashicorp/boundary/sdk/pbs/plugin"
@@ -32,6 +37,16 @@ type HostPlugin struct {
 	testCatalogStateOpts []awsCatalogPersistedStateOption
 }
 
+type hostSetQuery struct {
+	Id          string
+	Input       *ec2.DescribeInstancesInput
+	Output      *ec2.DescribeInstancesOutput
+	OutputHosts []*pb.ListHostsResponseHost
+}
+
+const defaultSessionName = "boundary-default"
+const dryRunOperationErrorCode = "DryRunOperation"
+
 // Ensure that we are implementing HostPluginServiceServer
 var _ pb.HostPluginServiceServer = (*HostPlugin)(nil)
 
@@ -495,13 +510,6 @@ func (p *HostPlugin) ListHosts(ctx context.Context, req *pb.ListHostsRequest) (*
 	}
 
 	// Build all the queries in advance.
-	type hostSetQuery struct {
-		Id          string
-		Input       *ec2.DescribeInstancesInput
-		Output      *ec2.DescribeInstancesOutput
-		OutputHosts []*pb.ListHostsResponseHost
-	}
-
 	queries := make([]hostSetQuery, len(sets))
 	for i, set := range sets {
 		// Validate Id since we use it in output
@@ -531,20 +539,22 @@ func (p *HostPlugin) ListHosts(ctx context.Context, req *pb.ListHostsRequest) (*
 	if catalogAttributes.DualStack {
 		opts = append(opts, WithDualStack(catalogAttributes.DualStack))
 	}
-	ec2Client, err := catalogState.EC2Client(ctx, opts...)
-	if err != nil {
-		return nil, errors.BadRequestStatusf("error getting EC2 client: %s", err)
-	}
 
 	// Run all queries now and assemble output.
 	var maxLen int
 	for i, query := range queries {
-		output, err := ec2Client.DescribeInstances(ctx, query.Input)
+		output, err := checkHosts(ctx, catalogState, query.Input, opts, catalogAttributes.TargetAccount)
 		if err != nil {
-			return nil, errors.BadRequestStatusf("error running DescribeInstances for host set id %q: %s", query.Id, err)
+			if catalogAttributes.TargetAccount != nil {
+				return nil, errors.BadRequestStatusf("unable to list hosts for host set %q: %s", query.Id, err)
+			}
+			return nil, errors.BadRequestStatusf("error retrieving host results for host set id %q: %s", query.Id, err)
 		}
 
 		queries[i].Output = output
+		if output == nil {
+			continue
+		}
 
 		// Process the output here, we will normalize this into a single
 		// set of hosts afterwards (possibly removing duplicates).
@@ -634,10 +644,6 @@ func buildFilters(attrs *SetAttributes) ([]types.Filter, error) {
 }
 
 func buildDescribeInstancesInput(attrs *SetAttributes, dryRun bool) (*ec2.DescribeInstancesInput, error) {
-	if attrs == nil {
-		attrs = &SetAttributes{}
-	}
-
 	filters, err := buildFilters(attrs)
 	if err != nil {
 		return nil, fmt.Errorf("error building filters: %w", err)
@@ -711,6 +717,117 @@ func awsInstanceToHost(instance types.Instance, catalogAttributes *CatalogAttrib
 	return result, nil
 }
 
+func checkHosts(ctx context.Context,
+	principalCatalogState *awsCatalogPersistedState,
+	input *ec2.DescribeInstancesInput,
+	opts []ec2Option,
+	target *credential.CredentialAttributes,
+) (*ec2.DescribeInstancesOutput, error) {
+	if principalCatalogState == nil {
+		return nil, fmt.Errorf("unable to create EC2 client from catalog state")
+	}
+
+	var ec2Client EC2API
+	var err error
+	if target == nil {
+		// use the principal account to execute the DescribeInstances command
+		ec2Client, err = principalCatalogState.EC2Client(ctx, opts...)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// use the target account to execute the DescribeInstances command
+		ec2Client, err = ec2ClientForTarget(ctx, principalCatalogState, target, opts)
+		if err != nil {
+			return nil, fmt.Errorf("EC2 client setup failed for target account: %w", err)
+		}
+	}
+
+	output, err := ec2Client.DescribeInstances(ctx, input)
+	if err != nil {
+		var awsErr smithy.APIError
+		ok := goerrors.As(err, &awsErr)
+		if ok && awsErr.ErrorCode() == dryRunOperationErrorCode {
+			// successful DryRun validation, no response necessary, no error thrown
+			return nil, nil
+		}
+
+		if target != nil {
+			return nil, fmt.Errorf("EC2 DescribeInstances failed for target account: %w", err)
+		}
+		return nil, err
+	}
+
+	return output, nil
+}
+
+// ec2ClientForTarget builds an EC2 client to query the target account.
+// The hop is a continuation of the principal session: STS AssumeRole is called
+// as the principal to get to the target, then EC2 uses the resulting temporary credentials.
+// This is not a second worker-level credential chain on the target attributes.
+func ec2ClientForTarget(
+	ctx context.Context,
+	principalCatalogState *awsCatalogPersistedState,
+	target *credential.CredentialAttributes,
+	opts []ec2Option) (EC2API, error) {
+	// Reuse the principal SDK config (HTTP client, retries, logger, and the
+	// principal identity).
+	principalCfg, err := principalCatalogState.GenerateCredentialChain(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("principal AWS configuration could not be loaded: %w", err)
+	}
+	if principalCfg == nil {
+		return nil, fmt.Errorf("nil principal AWS configuration while configuring EC2 client for target account")
+	}
+
+	// STS must run as the principal so the target role's trust policy sees that
+	// identity, not the worker's. Session name, external ID, and tags are
+	// forwarded from attrs when set so the AssumeRole matches the target role's configuration.
+	stsClient := sts.NewFromConfig(*principalCfg)
+	provider := stscreds.NewAssumeRoleProvider(stsClient, target.RoleArn, func(o *stscreds.AssumeRoleOptions) {
+		if target.RoleSessionName != "" {
+			o.RoleSessionName = target.RoleSessionName
+		} else {
+			// STS may reject the AssumeRole request if session name is not provided.
+			o.RoleSessionName = defaultSessionName
+		}
+		if target.RoleExternalId != "" {
+			o.ExternalID = &target.RoleExternalId
+		}
+		for k, v := range target.RoleTags {
+			o.Tags = append(o.Tags, stsTypes.Tag{
+				Key:   aws.String(k),
+				Value: aws.String(v),
+			})
+		}
+	})
+
+	// Same worker SDK environment as the principal; only identity and region change.
+	targetCfg := principalCfg.Copy()
+	targetCfg.Credentials = aws.NewCredentialsCache(provider)
+	if target.Region != "" {
+		targetCfg.Region = target.Region
+	}
+
+	parsed, err := getOpts(opts...)
+	if err != nil {
+		return nil, fmt.Errorf("EC2 client options are invalid: %w", err)
+	}
+	// Dual-stack is the worker's path to AWS endpoints, not per-account. Apply
+	// it on the hopped client the same way EC2Client does for the principal.
+	var ec2Opts []func(*ec2.Options)
+	if parsed.withDualStack {
+		ec2Opts = append(ec2Opts, ec2.WithEndpointResolverV2(&endpointResolver{
+			dualStack: parsed.withDualStack,
+		}))
+	}
+
+	if principalCatalogState.testEC2APIFunc != nil {
+		return principalCatalogState.testEC2APIFunc(targetCfg)
+	}
+	return ec2.NewFromConfig(targetCfg, ec2Opts...), nil
+}
+
 // dryRunValidation performs an AWS DescribeInstances call to verify the state's
 // credentials, the host listing functionality as well as the filters, if any
 // are passed in. This function can therefore be used for both host catalog and

plugin/service/host/plugin_test.go

@@ -1849,6 +1849,162 @@ func TestPluginOnUpdateSetErr(t *testing.T) {
 	}
 }
 
+func testListHostsSet(id, filter string) *hostsets.HostSet {
+	return &hostsets.HostSet{
+		Id: id,
+		Attrs: &hostsets.HostSet_Attributes{
+			Attributes: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					ConstDescribeInstancesFilters: structpb.NewListValue(
+						&structpb.ListValue{
+							Values: []*structpb.Value{
+								structpb.NewStringValue(filter),
+							},
+						},
+					),
+				},
+			},
+		},
+	}
+}
+
+func testListHostsPersisted() *pb.HostCatalogPersisted {
+	return &pb.HostCatalogPersisted{
+		Secrets: &structpb.Struct{
+			Fields: map[string]*structpb.Value{
+				credential.ConstAccessKeyId:     structpb.NewStringValue("AKIA_foobar"),
+				credential.ConstSecretAccessKey: structpb.NewStringValue("bazqux"),
+			},
+		},
+	}
+}
+
+func testExpectedDescribeInput(filterKey, filterValue string) *ec2.DescribeInstancesInput {
+	return &ec2.DescribeInstancesInput{
+		DryRun: aws.Bool(false),
+		Filters: []types.Filter{
+			{
+				Name:   aws.String(filterKey),
+				Values: []string{filterValue},
+			},
+			{
+				Name:   aws.String("instance-state-name"),
+				Values: []string{string(types.InstanceStateNameRunning)},
+			},
+		},
+	}
+}
+
+func TestPluginListHosts(t *testing.T) {
+	describeOutput := &ec2.DescribeInstancesOutput{
+		Reservations: []types.Reservation{
+			{
+				Instances: []types.Instance{
+					{
+						InstanceId:       aws.String("i-shared"),
+						PrivateIpAddress: aws.String("10.0.0.1"),
+					},
+				},
+			},
+		},
+	}
+
+	cases := []struct {
+		name             string
+		catalogFields    map[string]*structpb.Value
+		sets             []*hostsets.HostSet
+		expectedRegion   string
+		expectedHosts    []*pb.ListHostsResponseHost
+		expectedInputs   []*ec2.DescribeInstancesInput
+		expectedDescribe int
+	}{
+		{
+			name: "principal account lists hosts",
+			catalogFields: map[string]*structpb.Value{
+				credential.ConstRegion: structpb.NewStringValue("us-west-2"),
+			},
+			sets: []*hostsets.HostSet{
+				testListHostsSet("set-1", "tag-key=foo"),
+			},
+			expectedRegion: "us-west-2",
+			expectedHosts: []*pb.ListHostsResponseHost{
+				{
+					ExternalId: "i-shared",
+					SetIds:     []string{"set-1"},
+				},
+			},
+			expectedInputs: []*ec2.DescribeInstancesInput{
+				testExpectedDescribeInput("tag-key", "foo"),
+			},
+			expectedDescribe: 1,
+		},
+		{
+			name: "target account lists hosts without querying principal",
+			catalogFields: map[string]*structpb.Value{
+				credential.ConstRegion:        structpb.NewStringValue("us-west-2"),
+				credential.ConstTargetRoleArn: structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+				credential.ConstTargetRegion:  structpb.NewStringValue("eu-west-1"),
+			},
+			sets: []*hostsets.HostSet{
+				testListHostsSet("set-1", "tag-key=foo"),
+				testListHostsSet("set-2", "tag-key=bar"),
+			},
+			expectedRegion: "eu-west-1",
+			expectedHosts: []*pb.ListHostsResponseHost{
+				{
+					ExternalId: "i-shared",
+					SetIds:     []string{"set-1", "set-2"},
+				},
+			},
+			expectedInputs: []*ec2.DescribeInstancesInput{
+				testExpectedDescribeInput("tag-key", "foo"),
+				testExpectedDescribeInput("tag-key", "bar"),
+			},
+			expectedDescribe: 2,
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			require := require.New(t)
+			state := &testMockEC2State{}
+			p := &HostPlugin{
+				testCatalogStateOpts: []awsCatalogPersistedStateOption{
+					withTestEC2APIFunc(newTestMockEC2(
+						state,
+						testMockEC2WithDescribeInstancesOutput(describeOutput),
+					)),
+				},
+			}
+
+			resp, err := p.ListHosts(context.Background(), &pb.ListHostsRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{
+						Attributes: &structpb.Struct{Fields: tc.catalogFields},
+					},
+				},
+				Persisted: testListHostsPersisted(),
+				Sets:      tc.sets,
+			})
+			require.NoError(err)
+			require.NotNil(resp)
+			require.Len(resp.GetHosts(), len(tc.expectedHosts))
+			for i, expected := range tc.expectedHosts {
+				require.Equal(expected.ExternalId, resp.Hosts[i].ExternalId)
+				require.Equal(expected.SetIds, resp.Hosts[i].SetIds)
+			}
+
+			require.Equal(tc.expectedDescribe, state.DescribeInstancesCallCount)
+			require.Len(state.ClientRegions, tc.expectedDescribe)
+			for _, region := range state.ClientRegions {
+				require.Equal(tc.expectedRegion, region)
+			}
+			require.Equal(tc.expectedInputs, state.DescribeInstancesInputs)
+		})
+	}
+}
+
 func TestPluginListHostsErr(t *testing.T) {
 	cases := []struct {
 		name                string
@@ -2130,7 +2286,101 @@ func TestPluginListHostsErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: fmt.Sprintf("error running DescribeInstances for host set id \"foobar\": %s", testDescribeInstancesError),
+			expectedErrContains: fmt.Sprintf("error retrieving host results for host set id \"foobar\": %s", testDescribeInstancesError),
+			expectedErrCode:     codes.InvalidArgument,
+		},
+		{
+			name: "target attributes missing target_role_arn",
+			req: &pb.ListHostsRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{
+						Attributes: &structpb.Struct{
+							Fields: map[string]*structpb.Value{
+								credential.ConstRegion:       structpb.NewStringValue("us-west-2"),
+								credential.ConstTargetRegion: structpb.NewStringValue("eu-west-1"),
+							},
+						},
+					},
+				},
+			},
+			expectedErrContains: "attributes.target_role_arn: missing required value \"target_role_arn\"",
+			expectedErrCode:     codes.InvalidArgument,
+		},
+		{
+			name: "target EC2 client error",
+			req: &pb.ListHostsRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{
+						Attributes: &structpb.Struct{
+							Fields: map[string]*structpb.Value{
+								credential.ConstRegion:        structpb.NewStringValue("us-west-2"),
+								credential.ConstTargetRoleArn: structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+							},
+						},
+					},
+				},
+				Persisted: &pb.HostCatalogPersisted{
+					Secrets: &structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							credential.ConstAccessKeyId:          structpb.NewStringValue("AKIA_foobar"),
+							credential.ConstSecretAccessKey:      structpb.NewStringValue("bazqux"),
+							credential.ConstCredsLastRotatedTime: structpb.NewStringValue("2006-01-02T15:04:05+07:00"),
+						},
+					},
+				},
+				Sets: []*hostsets.HostSet{
+					{
+						Id: "foobar",
+						Attrs: &hostsets.HostSet_Attributes{
+							Attributes: &structpb.Struct{
+								Fields: map[string]*structpb.Value{
+									ConstDescribeInstancesFilters: structpb.NewListValue(
+										&structpb.ListValue{
+											Values: []*structpb.Value{
+												structpb.NewStringValue("tag-key=foo"),
+											},
+										},
+									),
+								},
+							},
+						},
+					},
+				},
+			},
+			catalogOpts: []awsCatalogPersistedStateOption{
+				withTestEC2APIFunc(func(...aws.Config) (EC2API, error) {
+					return nil, errors.New("test EC2 client error")
+				}),
+			},
+			expectedErrContains: "unable to list hosts for host set \"foobar\": EC2 client setup failed for target account: test EC2 client error",
+			expectedErrCode:     codes.InvalidArgument,
+		},
+		{
+			name: "target DescribeInstances error",
+			req: &pb.ListHostsRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{
+						Attributes: &structpb.Struct{
+							Fields: map[string]*structpb.Value{
+								credential.ConstRegion:        structpb.NewStringValue("us-west-2"),
+								credential.ConstTargetRoleArn: structpb.NewStringValue("arn:aws:iam::222222222222:role/Target"),
+								credential.ConstTargetRegion:  structpb.NewStringValue("eu-west-1"),
+							},
+						},
+					},
+				},
+				Persisted: testListHostsPersisted(),
+				Sets: []*hostsets.HostSet{
+					testListHostsSet("foobar", "tag-key=foo"),
+				},
+			},
+			catalogOpts: []awsCatalogPersistedStateOption{
+				withTestEC2APIFunc(newTestMockEC2(
+					nil,
+					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
+				)),
+			},
+			expectedErrContains: "unable to list hosts for host set \"foobar\": EC2 DescribeInstances failed for target account: DescribeInstances error",
 			expectedErrCode:     codes.InvalidArgument,
 		},
 		{
@@ -2383,21 +2633,6 @@ func TestBuildDescribeInstancesInput(t *testing.T) {
 			require.Equal(tc.expected, actual)
 		})
 	}
-
-	t.Run("nil attrs, dry run", func(t *testing.T) {
-		require := require.New(t)
-		actual, err := buildDescribeInstancesInput(nil, true)
-		require.NoError(err)
-		require.Equal(&ec2.DescribeInstancesInput{
-			DryRun: aws.Bool(true),
-			Filters: []types.Filter{
-				{
-					Name:   aws.String("instance-state-name"),
-					Values: []string{string(types.InstanceStateNameRunning)},
-				},
-			},
-		}, actual)
-	})
 }
 
 func TestAwsInstanceToHost(t *testing.T) {

plugin/service/host/testing.go

@@ -22,11 +22,17 @@ const (
 type testMockEC2State struct {
 	DescribeInstancesCalled      bool
 	DescribeInstancesInputParams *ec2.DescribeInstancesInput
+	DescribeInstancesCallCount   int
+	DescribeInstancesInputs      []*ec2.DescribeInstancesInput
+	ClientRegions                []string
 }
 
 func (s *testMockEC2State) Reset() {
 	s.DescribeInstancesCalled = false
 	s.DescribeInstancesInputParams = nil
+	s.DescribeInstancesCallCount = 0
+	s.DescribeInstancesInputs = nil
+	s.ClientRegions = nil
 }
 
 type testMockEC2 struct {
@@ -72,7 +78,10 @@ func newTestMockEC2(state *testMockEC2State, opts ...testMockEC2Option) ec2APIFu
 			if cfg.Region != "" {
 				m.Region = cfg.Region
 			}
+		}
 
+		if state != nil {
+			state.ClientRegions = append(state.ClientRegions, m.Region)
 		}
 
 		return m, nil
@@ -83,6 +92,8 @@ func (m *testMockEC2) DescribeInstances(ctx context.Context, input *ec2.Describe
 	if m.State != nil {
 		m.State.DescribeInstancesCalled = true
 		m.State.DescribeInstancesInputParams = input
+		m.State.DescribeInstancesCallCount++
+		m.State.DescribeInstancesInputs = append(m.State.DescribeInstancesInputs, input)
 	}
 
 	if m.DescribeInstancesError != nil {

testing/e2e_host_assumerole_test.go

@@ -0,0 +1,304 @@
+// Copyright IBM Corp. 2021, 2026
+// SPDX-License-Identifier: MPL-2.0
+
+package testing
+
+// This file contains table-driven test infrastructure for AssumeRole and
+// cross-role (two-hop) Dynamic Host Catalog scenarios. Each plugin operation
+// has a corresponding case type and runner function. The orchestrator in
+// e2e_host_test.go populates the case tables using the Terraform outputs.
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/boundary-plugin-aws/internal/credential"
+	"github.com/hashicorp/boundary-plugin-aws/plugin/service/host"
+	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostcatalogs"
+	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostsets"
+	pb "github.com/hashicorp/boundary/sdk/pbs/plugin"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/types/known/structpb"
+)
+
+// ---------------------------------------------------------------------------
+// Attr builders
+// ---------------------------------------------------------------------------
+
+// roleArnAttrs builds catalog attributes for a single-hop AssumeRole catalog.
+func roleArnAttrs(region, roleArn string) map[string]any {
+	return map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: true,
+		credential.ConstRoleArn:                   roleArn,
+	}
+}
+
+// crossRoleAttrs builds catalog attributes for a two-hop cross-role catalog.
+func crossRoleAttrs(region, principalRoleArn, targetRoleArn string) map[string]any {
+	return map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: true,
+		credential.ConstRoleArn:                   principalRoleArn,
+		credential.ConstTargetRoleArn:             targetRoleArn,
+	}
+}
+
+// tagFilterSetAttrs builds set attributes with a single tag-key filter.
+func tagFilterSetAttrs(tags []string) map[string]any {
+	return map[string]any{
+		host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", strings.Join(tags, ","))},
+	}
+}
+
+// requireTagInstancesMatchProvisioned asserts that every instance ID in tagInstancesMap
+// is present in provisionedIds (the raw []any slice from a Terraform output).
+func requireTagInstancesMatchProvisioned(t *testing.T, provisionedIds []any, tagInstancesMap map[string][]string) {
+	t.Helper()
+	idSet := make(map[string]struct{}, len(provisionedIds))
+	for _, id := range provisionedIds {
+		idSet[id.(string)] = struct{}{}
+	}
+	for tag, ids := range tagInstancesMap {
+		for _, id := range ids {
+			require.Contains(t, idSet, id, "instance ID %s in tag bucket %q was not provisioned by Terraform", id, tag)
+		}
+	}
+}
+
+// buildExpectedTagInstancesMap builds a map of tag key to instance IDs from a Terraform instance_tags output map.
+func buildExpectedTagInstancesMap(rawTags map[string]any, expectedTags []string) map[string][]string {
+	tagMap := make(map[string][]string)
+	for instanceId, instanceTags := range rawTags {
+		for tagKey := range instanceTags.(map[string]any) {
+			for _, expectedTag := range expectedTags {
+				if tagKey == expectedTag {
+					tagMap[tagKey] = append(tagMap[tagKey], instanceId)
+				}
+			}
+		}
+	}
+	return tagMap
+}
+
+// ---------------------------------------------------------------------------
+// Table-driven runners
+// ---------------------------------------------------------------------------
+
+type onCreateCatalogCase struct {
+	name         string
+	catalogAttrs map[string]any
+	wantErr      string // empty = expect success with empty persisted secrets
+}
+
+func testOnCreateCatalogCases(ctx context.Context, t *testing.T, p *host.HostPlugin, cases []onCreateCatalogCase) {
+	t.Helper()
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Helper()
+			require := require.New(t)
+			attrs, err := structpb.NewStruct(tc.catalogAttrs)
+			require.NoError(err)
+			resp, err := p.OnCreateCatalog(ctx, &pb.OnCreateCatalogRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: attrs},
+				},
+			})
+			if tc.wantErr != "" {
+				require.Error(err)
+				st, ok := status.FromError(err)
+				require.True(ok)
+				require.Contains(st.Message(), tc.wantErr)
+				return
+			}
+			require.NoError(err)
+			require.NotNil(resp)
+			// Dynamic credentials are never stored — persisted secrets should be empty.
+			require.Empty(resp.GetPersisted().GetSecrets().GetFields())
+		})
+	}
+}
+
+type onUpdateCatalogCase struct {
+	name         string
+	catalogAttrs map[string]any // used for both current and new when currentAttrs/newAttrs are nil
+	currentAttrs map[string]any // optional: override current catalog attrs
+	newAttrs     map[string]any // optional: override new catalog attrs
+	wantErr      string
+}
+
+func testOnUpdateCatalogCases(ctx context.Context, t *testing.T, p *host.HostPlugin, cases []onUpdateCatalogCase) {
+	t.Helper()
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Helper()
+			require := require.New(t)
+			currentRaw := tc.catalogAttrs
+			if tc.currentAttrs != nil {
+				currentRaw = tc.currentAttrs
+			}
+			newRaw := tc.catalogAttrs
+			if tc.newAttrs != nil {
+				newRaw = tc.newAttrs
+			}
+			currentAttrs, err := structpb.NewStruct(currentRaw)
+			require.NoError(err)
+			newAttrs, err := structpb.NewStruct(newRaw)
+			require.NoError(err)
+			resp, err := p.OnUpdateCatalog(ctx, &pb.OnUpdateCatalogRequest{
+				CurrentCatalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: currentAttrs},
+				},
+				NewCatalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: newAttrs},
+				},
+				Persisted: &pb.HostCatalogPersisted{},
+			})
+			if tc.wantErr != "" {
+				require.Error(err)
+				st, ok := status.FromError(err)
+				require.True(ok)
+				require.Contains(st.Message(), tc.wantErr)
+				return
+			}
+			require.NoError(err)
+			require.NotNil(resp)
+			// Dynamic credentials are never stored — persisted secrets should be empty.
+			require.Empty(resp.GetPersisted().GetSecrets().GetFields())
+		})
+	}
+}
+
+type onSetCase struct {
+	name         string
+	catalogAttrs map[string]any
+	tags         []string // nil = no filter (empty set attrs)
+	wantErr      string
+}
+
+func testOnCreateSetCases(ctx context.Context, t *testing.T, p *host.HostPlugin, cases []onSetCase) {
+	t.Helper()
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Helper()
+			require := require.New(t)
+			catalogAttrs, err := structpb.NewStruct(tc.catalogAttrs)
+			require.NoError(err)
+			setRaw := map[string]any{host.ConstDescribeInstancesFilters: []any{}}
+			if len(tc.tags) > 0 {
+				setRaw = tagFilterSetAttrs(tc.tags)
+			}
+			setAttrs, err := structpb.NewStruct(setRaw)
+			require.NoError(err)
+			resp, err := p.OnCreateSet(ctx, &pb.OnCreateSetRequest{
+				Catalog:   &hostcatalogs.HostCatalog{Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: catalogAttrs}},
+				Set:       &hostsets.HostSet{Attrs: &hostsets.HostSet_Attributes{Attributes: setAttrs}},
+				Persisted: &pb.HostCatalogPersisted{},
+			})
+			if tc.wantErr != "" {
+				require.Error(err)
+				st, ok := status.FromError(err)
+				require.True(ok)
+				require.Contains(st.Message(), tc.wantErr)
+				return
+			}
+			require.NoError(err)
+			require.NotNil(resp)
+		})
+	}
+}
+
+func testOnUpdateSetCases(ctx context.Context, t *testing.T, p *host.HostPlugin, cases []onSetCase) {
+	t.Helper()
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Helper()
+			require := require.New(t)
+			catalogAttrs, err := structpb.NewStruct(tc.catalogAttrs)
+			require.NoError(err)
+			setRaw := map[string]any{host.ConstDescribeInstancesFilters: []any{}}
+			if len(tc.tags) > 0 {
+				setRaw = tagFilterSetAttrs(tc.tags)
+			}
+			setAttrs, err := structpb.NewStruct(setRaw)
+			require.NoError(err)
+			set := &hostsets.HostSet{Attrs: &hostsets.HostSet_Attributes{Attributes: setAttrs}}
+			resp, err := p.OnUpdateSet(ctx, &pb.OnUpdateSetRequest{
+				Catalog:    &hostcatalogs.HostCatalog{Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: catalogAttrs}},
+				CurrentSet: set,
+				NewSet:     set,
+				Persisted:  &pb.HostCatalogPersisted{},
+			})
+			if tc.wantErr != "" {
+				require.Error(err)
+				st, ok := status.FromError(err)
+				require.True(ok)
+				require.Contains(st.Message(), tc.wantErr)
+				return
+			}
+			require.NoError(err)
+			require.NotNil(resp)
+		})
+	}
+}
+
+type listHostsCase struct {
+	name         string
+	catalogAttrs map[string]any
+	tags         []string
+	expected     map[string][]string // nil = don't assert instances (error cases)
+	wantErr      string
+}
+
+func testListHostsCases(ctx context.Context, t *testing.T, p *host.HostPlugin, cases []listHostsCase) {
+	t.Helper()
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Helper()
+			require := require.New(t)
+			catalogAttrs, err := structpb.NewStruct(tc.catalogAttrs)
+			require.NoError(err)
+			sets := make([]*hostsets.HostSet, len(tc.tags))
+			for i, tag := range tc.tags {
+				setAttrs, err := structpb.NewStruct(map[string]any{
+					host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", tag)},
+				})
+				require.NoError(err)
+				sets[i] = &hostsets.HostSet{
+					Id:    fmt.Sprintf("hostset-%d", i),
+					Attrs: &hostsets.HostSet_Attributes{Attributes: setAttrs},
+				}
+			}
+			resp, err := p.ListHosts(ctx, &pb.ListHostsRequest{
+				Catalog:   &hostcatalogs.HostCatalog{Attrs: &hostcatalogs.HostCatalog_Attributes{Attributes: catalogAttrs}},
+				Sets:      sets,
+				Persisted: &pb.HostCatalogPersisted{},
+			})
+			if tc.wantErr != "" {
+				require.Error(err)
+				st, ok := status.FromError(err)
+				require.True(ok)
+				require.Contains(st.Message(), tc.wantErr)
+				return
+			}
+			require.NoError(err)
+			require.NotNil(resp)
+			expectedInstances := make(map[string][]string)
+			for i, tag := range tc.tags {
+				for _, instanceId := range tc.expected[tag] {
+					expectedInstances[instanceId] = append(expectedInstances[instanceId], fmt.Sprintf("hostset-%d", i))
+				}
+			}
+			actualInstances := make(map[string][]string)
+			for _, h := range resp.GetHosts() {
+				actualInstances[h.ExternalId] = h.SetIds
+			}
+			require.Equal(expectedInstances, actualInstances)
+			t.Logf("success: %d hosts matched", len(actualInstances))
+		})
+	}
+}
+

testing/e2e_host_static_test.go

@@ -0,0 +1,396 @@
+// Copyright IBM Corp. 2021, 2026
+// SPDX-License-Identifier: MPL-2.0
+
+package testing
+
+// This file contains helper functions for the static-credential (access key /
+// secret access key) test paths exercised by TestHostPlugin in e2e_host_test.go.
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/hashicorp/boundary-plugin-aws/internal/credential"
+	"github.com/hashicorp/boundary-plugin-aws/plugin/service/host"
+	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostcatalogs"
+	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostsets"
+	pb "github.com/hashicorp/boundary/sdk/pbs/plugin"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/types/known/structpb"
+)
+
+func testPluginOnCreateCatalog(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, rotate bool) (string, string) {
+	t.Helper()
+	t.Logf("testing OnCreateCatalog (region=%s, rotate=%t)", region, rotate)
+	require := require.New(t)
+
+	reqAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: !rotate,
+	})
+	require.NoError(err)
+	reqSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:     accessKeyId,
+		credential.ConstSecretAccessKey: secretAccessKey,
+	})
+	require.NoError(err)
+	request := &pb.OnCreateCatalogRequest{
+		Catalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: reqAttrs,
+			},
+			Secrets: reqSecrets,
+		},
+	}
+	response, err := p.OnCreateCatalog(ctx, request)
+	require.NoError(err)
+	require.NotNil(response)
+	persisted := response.GetPersisted()
+	require.NotNil(persisted)
+	return validatePersistedSecrets(t, persisted.GetSecrets(), accessKeyId, secretAccessKey, rotate)
+}
+
+func testPluginOnUpdateCatalog(
+	ctx context.Context, t *testing.T, p *host.HostPlugin,
+	region, currentAccessKeyId, currentSecretAccessKey, newAccessKeyId, newSecretAccessKey string,
+	rotated, rotate bool,
+) (string, string) {
+	t.Helper()
+	t.Logf("testing OnUpdateCatalog (region=%s, newcreds=%t, rotated=%t, rotate=%t)", region, newAccessKeyId != "" && newSecretAccessKey != "", rotated, rotate)
+	require := require.New(t)
+
+	// Take a timestamp of the current time to get a point in time to
+	// reference, ensuring that we are updating credential rotation
+	// timestamps.
+	currentCredsLastRotatedTime := time.Now()
+
+	reqCurrentAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: !rotated,
+	})
+	require.NoError(err)
+	reqNewAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: !rotate,
+	})
+	require.NoError(err)
+	var reqSecrets *structpb.Struct
+	if newAccessKeyId != "" && newSecretAccessKey != "" {
+		reqSecrets, err = structpb.NewStruct(map[string]any{
+			credential.ConstAccessKeyId:     newAccessKeyId,
+			credential.ConstSecretAccessKey: newSecretAccessKey,
+		})
+		require.NoError(err)
+	}
+	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:     currentAccessKeyId,
+		credential.ConstSecretAccessKey: currentSecretAccessKey,
+		credential.ConstCredsLastRotatedTime: func() string {
+			if rotated {
+				return currentCredsLastRotatedTime.Format(time.RFC3339Nano)
+			}
+
+			return (time.Time{}).Format(time.RFC3339Nano)
+		}(),
+	})
+	require.NoError(err)
+	require.NotNil(reqPersistedSecrets)
+	request := &pb.OnUpdateCatalogRequest{
+		CurrentCatalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: reqCurrentAttrs,
+			},
+		},
+		NewCatalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: reqNewAttrs,
+			},
+			Secrets: reqSecrets,
+		},
+		Persisted: &pb.HostCatalogPersisted{
+			Secrets: reqPersistedSecrets,
+		},
+	}
+	response, err := p.OnUpdateCatalog(ctx, request)
+	require.NoError(err)
+	require.NotNil(response)
+	persisted := response.GetPersisted()
+	require.NotNil(persisted)
+	return validateUpdateSecrets(t, persisted.GetSecrets(), currentCredsLastRotatedTime, currentAccessKeyId, currentSecretAccessKey, newAccessKeyId, newSecretAccessKey, rotated, rotate)
+}
+
+func testPluginOnDeleteCatalog(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, rotated bool) {
+	t.Helper()
+	t.Logf("testing OnDeleteCatalog (region=%s, rotated=%t)", region, rotated)
+	require := require.New(t)
+
+	reqAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: !rotated,
+	})
+	require.NoError(err)
+	reqSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:     accessKeyId,
+		credential.ConstSecretAccessKey: secretAccessKey,
+	})
+	require.NoError(err)
+	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:     accessKeyId,
+		credential.ConstSecretAccessKey: secretAccessKey,
+		credential.ConstCredsLastRotatedTime: func() string {
+			if rotated {
+				return time.Now().Format(time.RFC3339Nano)
+			}
+
+			return (time.Time{}).Format(time.RFC3339Nano)
+		}(),
+	})
+	require.NoError(err)
+	request := &pb.OnDeleteCatalogRequest{
+		Catalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: reqAttrs,
+			},
+			Secrets: reqSecrets,
+		},
+		Persisted: &pb.HostCatalogPersisted{
+			Secrets: reqPersistedSecrets,
+		},
+	}
+	response, err := p.OnDeleteCatalog(ctx, request)
+	require.NoError(err)
+	require.NotNil(response)
+
+	// We want to test the validity of the credentials post-deletion.
+	if rotated {
+		// The credentials should no longer be valid.
+		requireCredentialsInvalid(t, accessKeyId, secretAccessKey)
+	} else {
+		// The credentials should still be valid. Sleep 10s first just to
+		// be sure, since we're not rotating.
+		time.Sleep(time.Second * 10)
+		requireCredentialsValid(t, accessKeyId, secretAccessKey)
+	}
+}
+
+func testPluginOnCreateUpdateSet(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, tags []string) {
+	t.Helper()
+	t.Logf("testing OnCreateSet (region=%s, tags=%v)", region, tags)
+	require := require.New(t)
+	catalogAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: true, // Note that this does nothing in sets, but just noting for tests
+	})
+	require.NoError(err)
+	setAttrs, err := structpb.NewStruct(map[string]any{
+		host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", strings.Join(tags, ","))},
+	})
+	require.NoError(err)
+	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:          accessKeyId,
+		credential.ConstSecretAccessKey:      secretAccessKey,
+		credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
+	})
+	require.NoError(err)
+	createRequest := &pb.OnCreateSetRequest{
+		Catalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: catalogAttrs,
+			},
+		},
+		Set: &hostsets.HostSet{
+			Attrs: &hostsets.HostSet_Attributes{
+				Attributes: setAttrs,
+			},
+		},
+		Persisted: &pb.HostCatalogPersisted{
+			Secrets: reqPersistedSecrets,
+		},
+	}
+	createResponse, err := p.OnCreateSet(ctx, createRequest)
+	require.NoError(err)
+	require.NotNil(createResponse)
+
+	// Do an update test in the same function, as it's pretty much the
+	// same function right now.
+	t.Logf("testing OnUpdateSet (region=%s, tags=%v)", region, tags)
+	updateRequest := &pb.OnUpdateSetRequest{
+		Catalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: catalogAttrs,
+			},
+		},
+		CurrentSet: &hostsets.HostSet{
+			Attrs: &hostsets.HostSet_Attributes{
+				Attributes: setAttrs,
+			},
+		},
+		NewSet: &hostsets.HostSet{
+			Attrs: &hostsets.HostSet_Attributes{
+				Attributes: setAttrs,
+			},
+		},
+		Persisted: &pb.HostCatalogPersisted{
+			Secrets: reqPersistedSecrets,
+		},
+	}
+	updateResponse, err := p.OnUpdateSet(ctx, updateRequest)
+	require.NoError(err)
+	require.NotNil(updateResponse)
+}
+
+func testPluginListHosts(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, tags []string, expected map[string][]string) {
+	t.Helper()
+	t.Logf("testing ListHosts (region=%s, tags=%v)", region, tags)
+	require := require.New(t)
+	catalogAttrs, err := structpb.NewStruct(map[string]any{
+		credential.ConstRegion:                    region,
+		credential.ConstDisableCredentialRotation: true, // Note that this does nothing in sets, but just noting for tests
+	})
+	require.NoError(err)
+	sets := make([]*hostsets.HostSet, len(tags))
+	for i, tag := range tags {
+		setAttrs, err := structpb.NewStruct(map[string]any{
+			host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", tag)},
+		})
+		require.NoError(err)
+		sets[i] = &hostsets.HostSet{
+			Id: fmt.Sprintf("hostset-%d", i),
+			Attrs: &hostsets.HostSet_Attributes{
+				Attributes: setAttrs,
+			},
+		}
+	}
+	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
+		credential.ConstAccessKeyId:          accessKeyId,
+		credential.ConstSecretAccessKey:      secretAccessKey,
+		credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
+	})
+	require.NoError(err)
+	request := &pb.ListHostsRequest{
+		Catalog: &hostcatalogs.HostCatalog{
+			Attrs: &hostcatalogs.HostCatalog_Attributes{
+				Attributes: catalogAttrs,
+			},
+		},
+		Sets: sets,
+		Persisted: &pb.HostCatalogPersisted{
+			Secrets: reqPersistedSecrets,
+		},
+	}
+	response, err := p.ListHosts(ctx, request)
+	require.NoError(err)
+	require.NotNil(response)
+
+	// Validate the returned instances by ID. Assemble the instance
+	// details from the expected set.
+	expectedInstances := make(map[string][]string)
+	for i, tag := range tags {
+		for _, instanceId := range expected[tag] {
+			expectedInstances[instanceId] = append(expectedInstances[instanceId], fmt.Sprintf("hostset-%d", i))
+		}
+	}
+
+	// Take the returned hosts by ID and create the same kind of map.
+	actualInstances := make(map[string][]string)
+	for _, host := range response.GetHosts() {
+		actualInstances[host.ExternalId] = host.SetIds
+	}
+
+	// Compare
+	require.Equal(expectedInstances, actualInstances)
+	// Success
+	t.Logf("testing ListHosts: success (region=%s, tags=%v, expected/actual=(len=%d, ids=%s))", region, tags, len(actualInstances), actualInstances)
+}
+
+func testInstanceAddressesOnlyListHosts(ctx context.Context, t *testing.T, p *host.HostPlugin, tf *TestTerraformer, region, accessKeyId, secretAccessKey string) {
+	t.Helper()
+	t.Logf("testing testInstanceAddressesOnlyListHosts")
+
+	// Get the instance details from tf output
+	instanceID, err := tf.GetOutputString("multi_address_instance_id")
+	require.NoError(t, err)
+	primaryAddresses, err := tf.GetOutputMap("multi_address_primary_addresses")
+	require.NoError(t, err)
+	secondaryAddresses, err := tf.GetOutputMap("multi_address_secondary_addresses")
+	require.NoError(t, err)
+
+	var primary, allAddresses []string
+	for _, addr := range primaryAddresses {
+		primary = append(primary, addr.(string))
+	}
+	allAddresses = append(allAddresses, primary...)
+	for _, addr := range secondaryAddresses {
+		allAddresses = append(allAddresses, addr.(string))
+	}
+
+	cases := []struct {
+		name                  string
+		instanceAddressesOnly bool
+		expectedIPs           []string
+	}{
+		{
+			name:        "all addresses",
+			expectedIPs: allAddresses,
+		},
+		{
+			name:                  "instance addresses only",
+			instanceAddressesOnly: true,
+			expectedIPs:           primary,
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			require := require.New(t)
+
+			catalogAttrMap := map[string]any{
+				credential.ConstRegion:                    region,
+				credential.ConstDisableCredentialRotation: true,
+			}
+			if tc.instanceAddressesOnly {
+				catalogAttrMap[host.ConstInstanceAddressesOnly] = true
+			}
+
+			catalogAttrs, err := structpb.NewStruct(catalogAttrMap)
+			require.NoError(err)
+			setAttrs, err := structpb.NewStruct(map[string]any{
+				host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("instance-id=%s", instanceID)},
+			})
+			require.NoError(err)
+
+			reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
+				credential.ConstAccessKeyId:          accessKeyId,
+				credential.ConstSecretAccessKey:      secretAccessKey,
+				credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
+			})
+			require.NoError(err)
+			request := &pb.ListHostsRequest{
+				Catalog: &hostcatalogs.HostCatalog{
+					Attrs: &hostcatalogs.HostCatalog_Attributes{
+						Attributes: catalogAttrs,
+					},
+				},
+				Sets: []*hostsets.HostSet{{
+					Id:    "hostset-0",
+					Attrs: &hostsets.HostSet_Attributes{Attributes: setAttrs},
+				}},
+				Persisted: &pb.HostCatalogPersisted{
+					Secrets: reqPersistedSecrets,
+				},
+			}
+
+			response, err := p.ListHosts(ctx, request)
+			require.NoError(err)
+			require.Len(response.GetHosts(), 1)
+			hostResp := response.GetHosts()[0]
+
+			require.Equal(instanceID, hostResp.ExternalId)
+			require.ElementsMatch(hostResp.IpAddresses, tc.expectedIPs)
+		})
+	}
+}

testing/e2e_host_test.go

@@ -3,21 +3,24 @@
 
 package testing
 
+// This file contains the TestHostPlugin orchestrator. It deploys the Terraform
+// workspace, collects outputs, and calls the per-credential-type helper
+// functions defined in e2e_host_static_test.go and e2e_host_assumerole_test.go.
+
 import (
 	"context"
-	"fmt"
 	"os"
-	"strings"
 	"testing"
-	"time"
 
-	"github.com/hashicorp/boundary-plugin-aws/internal/credential"
 	"github.com/hashicorp/boundary-plugin-aws/plugin/service/host"
-	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostcatalogs"
-	"github.com/hashicorp/boundary/sdk/pbs/controller/api/resources/hostsets"
-	pb "github.com/hashicorp/boundary/sdk/pbs/plugin"
 	"github.com/stretchr/testify/require"
-	"google.golang.org/protobuf/types/known/structpb"
+)
+
+const (
+	envTargetAccessKeyId     = "TARGET_AWS_ACCESS_KEY_ID"
+	envTargetSecretAccessKey = "TARGET_AWS_SECRET_ACCESS_KEY"
+	envTargetSessionToken    = "TARGET_AWS_SESSION_TOKEN"
+	envTargetRegion          = "TARGET_AWS_REGION"
 )
 
 const expectedEc2InstanceCount = 5
@@ -35,7 +38,29 @@ func TestHostPlugin(t *testing.T) {
 	}
 
 	require := require.New(t)
-	tf, err := NewTestTerraformer("testdata/host")
+
+	// Collect cross-account credentials up front so they can be passed as
+	// Terraform variables. The cross-account section is skipped (not failed)
+	// when these are absent, but we need the values available before Deploy.
+	targetAccessKeyId := os.Getenv(envTargetAccessKeyId)
+	targetSecretAccessKey := os.Getenv(envTargetSecretAccessKey)
+	targetSessionToken := os.Getenv(envTargetSessionToken)
+	targetRegion := os.Getenv(envTargetRegion)
+	if targetRegion == "" {
+		targetRegion = region
+	}
+
+	tfVars := map[string]string{}
+	if targetAccessKeyId != "" && targetSecretAccessKey != "" {
+		tfVars["target_access_key_id"] = targetAccessKeyId
+		tfVars["target_secret_access_key"] = targetSecretAccessKey
+		tfVars["target_region"] = targetRegion
+		if targetSessionToken != "" {
+			tfVars["target_session_token"] = targetSessionToken
+		}
+	}
+
+	tf, err := NewTestTerraformer("testdata/host", tfVars)
 	require.NoError(err)
 	require.NotNil(tf)
 
@@ -137,16 +162,9 @@ func TestHostPlugin(t *testing.T) {
 	// Reassign the keyid and secret first.
 	keyid, secret = iamAccessKeyIds[5].(string), iamSecretAccessKeys[5].(string)
 	// Process the collection of instances and index by expected tag names.
-	expectedTagInstancesMap := make(map[string][]string)
-	for instanceId, instanceTags := range ec2InstanceTags {
-		for tagKey := range instanceTags.(map[string]any) {
-			for _, expectedTag := range expectedTags {
-				if tagKey == expectedTag {
-					expectedTagInstancesMap[tagKey] = append(expectedTagInstancesMap[tagKey], instanceId)
-				}
-			}
-		}
-	}
+	expectedTagInstancesMap := buildExpectedTagInstancesMap(ec2InstanceTags, expectedTags)
+
+	requireTagInstancesMatchProvisioned(t, ec2InstanceIds, expectedTagInstancesMap)
 
 	cases := [][]string{
 		{expectedTags[0]},
@@ -168,377 +186,162 @@ func TestHostPlugin(t *testing.T) {
 
 	// finally lets test instance_addresses_only catalog attribute correctly syncs only instance addresses
 	testInstanceAddressesOnlyListHosts(ctx, t, p, tf, region, keyid, secret)
-}
 
-func testPluginOnCreateCatalog(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, rotate bool) (string, string) {
-	t.Helper()
-	t.Logf("testing OnCreateCatalog (region=%s, rotate=%t)", region, rotate)
-	require := require.New(t)
+	// ********************
+	// * AssumeRole - Happy Path & Error Cases
+	// ********************
+	assumeRoleArn, err := tf.GetOutputString("assume_role_arn")
+	require.NoError(err)
 
-	reqAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: !rotate,
+	noTrustRoleArn, err := tf.GetOutputString("assume_role_no_trust_arn")
+	require.NoError(err)
+
+	missingPermRoleArn, err := tf.GetOutputString("assume_role_no_ec2_permission_arn")
+	require.NoError(err)
+
+	testOnCreateCatalogCases(ctx, t, p, []onCreateCatalogCase{
+		{name: "assume role happy path", catalogAttrs: roleArnAttrs(region, assumeRoleArn)},
+		{name: "assume role no trust", catalogAttrs: roleArnAttrs(region, noTrustRoleArn), wantErr: "AccessDenied"},
+		{name: "assume role missing ec2 permission", catalogAttrs: roleArnAttrs(region, missingPermRoleArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	reqSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:     accessKeyId,
-		credential.ConstSecretAccessKey: secretAccessKey,
+	testOnUpdateCatalogCases(ctx, t, p, []onUpdateCatalogCase{
+		{name: "assume role happy path", catalogAttrs: roleArnAttrs(region, assumeRoleArn)},
+		{name: "assume role no trust", catalogAttrs: roleArnAttrs(region, noTrustRoleArn), wantErr: "AccessDenied"},
+		{name: "assume role missing ec2 permission", currentAttrs: roleArnAttrs(region, assumeRoleArn), newAttrs: roleArnAttrs(region, missingPermRoleArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	request := &pb.OnCreateCatalogRequest{
-		Catalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: reqAttrs,
-			},
-			Secrets: reqSecrets,
-		},
-	}
-	response, err := p.OnCreateCatalog(ctx, request)
-	require.NoError(err)
-	require.NotNil(response)
-	persisted := response.GetPersisted()
-	require.NotNil(persisted)
-	return validatePersistedSecrets(t, persisted.GetSecrets(), accessKeyId, secretAccessKey, rotate)
-}
-
-func testPluginOnUpdateCatalog(
-	ctx context.Context, t *testing.T, p *host.HostPlugin,
-	region, currentAccessKeyId, currentSecretAccessKey, newAccessKeyId, newSecretAccessKey string,
-	rotated, rotate bool,
-) (string, string) {
-	t.Helper()
-	t.Logf("testing OnUpdateCatalog (region=%s, newcreds=%t, rotated=%t, rotate=%t)", region, newAccessKeyId != "" && newSecretAccessKey != "", rotated, rotate)
-	require := require.New(t)
-
-	// Take a timestamp of the current time to get a point in time to
-	// reference, ensuring that we are updating credential rotation
-	// timestamps.
-	currentCredsLastRotatedTime := time.Now()
-
-	reqCurrentAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: !rotated,
+	testOnCreateSetCases(ctx, t, p, []onSetCase{
+		{name: "assume role happy path", catalogAttrs: roleArnAttrs(region, assumeRoleArn), tags: cases[0]},
+		{name: "assume role no trust", catalogAttrs: roleArnAttrs(region, noTrustRoleArn), wantErr: "AccessDenied"},
+		{name: "assume role missing ec2 permission", catalogAttrs: roleArnAttrs(region, missingPermRoleArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	reqNewAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: !rotate,
+	testOnUpdateSetCases(ctx, t, p, []onSetCase{
+		{name: "assume role happy path", catalogAttrs: roleArnAttrs(region, assumeRoleArn), tags: cases[0]},
+		{name: "assume role no trust", catalogAttrs: roleArnAttrs(region, noTrustRoleArn), wantErr: "AccessDenied"},
+		{name: "assume role missing ec2 permission", catalogAttrs: roleArnAttrs(region, missingPermRoleArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	var reqSecrets *structpb.Struct
-	if newAccessKeyId != "" && newSecretAccessKey != "" {
-		reqSecrets, err = structpb.NewStruct(map[string]any{
-			credential.ConstAccessKeyId:     newAccessKeyId,
-			credential.ConstSecretAccessKey: newSecretAccessKey,
-		})
-		require.NoError(err)
-	}
-	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:     currentAccessKeyId,
-		credential.ConstSecretAccessKey: currentSecretAccessKey,
-		credential.ConstCredsLastRotatedTime: func() string {
-			if rotated {
-				return currentCredsLastRotatedTime.Format(time.RFC3339Nano)
-			}
-
-			return (time.Time{}).Format(time.RFC3339Nano)
-		}(),
+	testListHostsCases(ctx, t, p, []listHostsCase{
+		{name: "assume role happy path", catalogAttrs: roleArnAttrs(region, assumeRoleArn), tags: cases[0], expected: expectedTagInstancesMap},
+		{name: "assume role no trust", catalogAttrs: roleArnAttrs(region, noTrustRoleArn), tags: cases[0], wantErr: "AccessDenied"},
+		{name: "assume role missing ec2 permission", catalogAttrs: roleArnAttrs(region, missingPermRoleArn), tags: cases[0], wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	require.NotNil(reqPersistedSecrets)
-	request := &pb.OnUpdateCatalogRequest{
-		CurrentCatalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: reqCurrentAttrs,
-			},
-		},
-		NewCatalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: reqNewAttrs,
-			},
-			Secrets: reqSecrets,
-		},
-		Persisted: &pb.HostCatalogPersisted{
-			Secrets: reqPersistedSecrets,
-		},
-	}
-	response, err := p.OnUpdateCatalog(ctx, request)
-	require.NoError(err)
-	require.NotNil(response)
-	persisted := response.GetPersisted()
-	require.NotNil(persisted)
-	return validateUpdateSecrets(t, persisted.GetSecrets(), currentCredsLastRotatedTime, currentAccessKeyId, currentSecretAccessKey, newAccessKeyId, newSecretAccessKey, rotated, rotate)
-}
 
-func testPluginOnDeleteCatalog(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, rotated bool) {
-	t.Helper()
-	t.Logf("testing OnDeleteCatalog (region=%s, rotated=%t)", region, rotated)
-	require := require.New(t)
+	// ********************
+	// * Cross-Role AssumeRole - Happy Path & Error Cases
+	// ********************
+	// These tests exercise the two-hop role chain within a single AWS account.
+	// The principal role has no ec2:DescribeInstances; the target role
+	// (assume_role) does. The plugin must assume the principal first, then use
+	// those credentials to assume the target role before calling DescribeInstances.
+	// This validates the plugin's chained credential logic without requiring a
+	// second AWS account.
+	crossRolePrincipalArn, err := tf.GetOutputString("cross_role_principal_arn")
+	require.NoError(err)
 
-	reqAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: !rotated,
+	crossRolePrincipalNoTrustArn, err := tf.GetOutputString("cross_role_principal_no_trust_arn")
+	require.NoError(err)
+
+	crossRoleTargetNoTrustArn, err := tf.GetOutputString("cross_role_target_no_trust_arn")
+	require.NoError(err)
+
+	crossRoleTargetNoEc2PermissionArn, err := tf.GetOutputString("cross_role_target_no_ec2_permission_arn")
+	require.NoError(err)
+
+	// assume_role_arn is reused as the cross-role target — it has ec2:DescribeInstances
+	// and its trust policy allows the cross-role principal to assume it.
+	testOnCreateCatalogCases(ctx, t, p, []onCreateCatalogCase{
+		{name: "cross-role happy path", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, assumeRoleArn)},
+		{name: "cross-role principal no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalNoTrustArn, assumeRoleArn), wantErr: "AccessDenied"},
+		{name: "cross-role target no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoTrustArn), wantErr: "AccessDenied"},
+		{name: "cross-role target missing ec2 permission", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	reqSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:     accessKeyId,
-		credential.ConstSecretAccessKey: secretAccessKey,
+	testOnUpdateCatalogCases(ctx, t, p, []onUpdateCatalogCase{
+		{name: "cross-role happy path", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, assumeRoleArn)},
+		{name: "cross-role principal no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalNoTrustArn, assumeRoleArn), wantErr: "AccessDenied"},
+		{name: "cross-role target no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoTrustArn), wantErr: "AccessDenied"},
+		{name: "cross-role target missing ec2 permission", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:     accessKeyId,
-		credential.ConstSecretAccessKey: secretAccessKey,
-		credential.ConstCredsLastRotatedTime: func() string {
-			if rotated {
-				return time.Now().Format(time.RFC3339Nano)
-			}
-
-			return (time.Time{}).Format(time.RFC3339Nano)
-		}(),
+	testOnCreateSetCases(ctx, t, p, []onSetCase{
+		{name: "cross-role happy path", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, assumeRoleArn), tags: cases[0]},
+		{name: "cross-role principal no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalNoTrustArn, assumeRoleArn), wantErr: "AccessDenied"},
+		{name: "cross-role target no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoTrustArn), wantErr: "AccessDenied"},
+		{name: "cross-role target missing ec2 permission", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
 	})
-	require.NoError(err)
-	request := &pb.OnDeleteCatalogRequest{
-		Catalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: reqAttrs,
-			},
-			Secrets: reqSecrets,
-		},
-		Persisted: &pb.HostCatalogPersisted{
-			Secrets: reqPersistedSecrets,
-		},
-	}
-	response, err := p.OnDeleteCatalog(ctx, request)
-	require.NoError(err)
-	require.NotNil(response)
-
-	// We want to test the validity of the credentials post-deletion.
-	if rotated {
-		// The credentials should no longer be valid.
-		requireCredentialsInvalid(t, accessKeyId, secretAccessKey)
+	testOnUpdateSetCases(ctx, t, p, []onSetCase{
+		{name: "cross-role happy path", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, assumeRoleArn), tags: cases[0]},
+		{name: "cross-role principal no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalNoTrustArn, assumeRoleArn), wantErr: "AccessDenied"},
+		{name: "cross-role target no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoTrustArn), wantErr: "AccessDenied"},
+		{name: "cross-role target missing ec2 permission", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
+	})
+	testListHostsCases(ctx, t, p, []listHostsCase{
+		{name: "cross-role happy path", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, assumeRoleArn), tags: cases[0], expected: expectedTagInstancesMap},
+		{name: "cross-role principal no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalNoTrustArn, assumeRoleArn), tags: cases[0], wantErr: "AccessDenied"},
+		{name: "cross-role target no trust", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoTrustArn), tags: cases[0], wantErr: "AccessDenied"},
+		{name: "cross-role target missing ec2 permission", catalogAttrs: crossRoleAttrs(region, crossRolePrincipalArn, crossRoleTargetNoEc2PermissionArn), tags: cases[0], wantErr: "UnauthorizedOperation"},
+	})
+	// ********************
+	// * Cross-Account AssumeRole - Happy Path & Error Cases
+	// ********************
+	// These tests require credentials for a second AWS account supplied via
+	// TARGET_AWS_ACCESS_KEY_ID, TARGET_AWS_SECRET_ACCESS_KEY, and (for
+	// temporary credentials) TARGET_AWS_SESSION_TOKEN. They are skipped
+	// (not failed) when the access key ID or secret access key are absent.
+	if targetAccessKeyId == "" || targetSecretAccessKey == "" {
+		t.Log("skipping cross-account tests: set TARGET_AWS_ACCESS_KEY_ID and TARGET_AWS_SECRET_ACCESS_KEY to enable")
 	} else {
-		// The credentials should still be valid. Sleep 10s first just to
-		// be sure, since we're not rotating.
-		time.Sleep(time.Second * 10)
-		requireCredentialsValid(t, accessKeyId, secretAccessKey)
-	}
-}
-
-func testPluginOnCreateUpdateSet(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, tags []string) {
-	t.Helper()
-	t.Logf("testing OnCreateSet (region=%s, tags=%v)", region, tags)
-	require := require.New(t)
-	catalogAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: true, // Note that this does nothing in sets, but just noting for tests
-	})
-	require.NoError(err)
-	setAttrs, err := structpb.NewStruct(map[string]any{
-		host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", strings.Join(tags, ","))},
-	})
-	require.NoError(err)
-	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:          accessKeyId,
-		credential.ConstSecretAccessKey:      secretAccessKey,
-		credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
-	})
-	require.NoError(err)
-	createRequest := &pb.OnCreateSetRequest{
-		Catalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: catalogAttrs,
-			},
-		},
-		Set: &hostsets.HostSet{
-			Attrs: &hostsets.HostSet_Attributes{
-				Attributes: setAttrs,
-			},
-		},
-		Persisted: &pb.HostCatalogPersisted{
-			Secrets: reqPersistedSecrets,
-		},
-	}
-	createResponse, err := p.OnCreateSet(ctx, createRequest)
-	require.NoError(err)
-	require.NotNil(createResponse)
-
-	// Do an update test in the same function, as it's pretty much the
-	// same function right now.
-	t.Logf("testing OnUpdateSet (region=%s, tags=%v)", region, tags)
-	updateRequest := &pb.OnUpdateSetRequest{
-		Catalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: catalogAttrs,
-			},
-		},
-		CurrentSet: &hostsets.HostSet{
-			Attrs: &hostsets.HostSet_Attributes{
-				Attributes: setAttrs,
-			},
-		},
-		NewSet: &hostsets.HostSet{
-			Attrs: &hostsets.HostSet_Attributes{
-				Attributes: setAttrs,
-			},
-		},
-		Persisted: &pb.HostCatalogPersisted{
-			Secrets: reqPersistedSecrets,
-		},
-	}
-	updateResponse, err := p.OnUpdateSet(ctx, updateRequest)
-	require.NoError(err)
-	require.NotNil(updateResponse)
-}
-
-func testPluginListHosts(ctx context.Context, t *testing.T, p *host.HostPlugin, region, accessKeyId, secretAccessKey string, tags []string, expected map[string][]string) {
-	t.Helper()
-	t.Logf("testing ListHosts (region=%s, tags=%v)", region, tags)
-	require := require.New(t)
-	catalogAttrs, err := structpb.NewStruct(map[string]any{
-		credential.ConstRegion:                    region,
-		credential.ConstDisableCredentialRotation: true, // Note that this does nothing in sets, but just noting for tests
-	})
-	require.NoError(err)
-	sets := make([]*hostsets.HostSet, len(tags))
-	for i, tag := range tags {
-		setAttrs, err := structpb.NewStruct(map[string]any{
-			host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("tag-key=%s", tag)},
-		})
+		crossAccountPrincipalArn, err := tf.GetOutputString("cross_account_principal_arn")
 		require.NoError(err)
-		sets[i] = &hostsets.HostSet{
-			Id: fmt.Sprintf("hostset-%d", i),
-			Attrs: &hostsets.HostSet_Attributes{
-				Attributes: setAttrs,
-			},
-		}
-	}
-	reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
-		credential.ConstAccessKeyId:          accessKeyId,
-		credential.ConstSecretAccessKey:      secretAccessKey,
-		credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
-	})
-	require.NoError(err)
-	request := &pb.ListHostsRequest{
-		Catalog: &hostcatalogs.HostCatalog{
-			Attrs: &hostcatalogs.HostCatalog_Attributes{
-				Attributes: catalogAttrs,
-			},
-		},
-		Sets: sets,
-		Persisted: &pb.HostCatalogPersisted{
-			Secrets: reqPersistedSecrets,
-		},
-	}
-	response, err := p.ListHosts(ctx, request)
-	require.NoError(err)
-	require.NotNil(response)
 
-	// Validate the returned instances by ID. Assemble the instance
-	// details from the expected set.
-	expectedInstances := make(map[string][]string)
-	for i, tag := range tags {
-		for _, instanceId := range expected[tag] {
-			expectedInstances[instanceId] = append(expectedInstances[instanceId], fmt.Sprintf("hostset-%d", i))
-		}
-	}
+		crossAccountPrincipalNoTrustArn, err := tf.GetOutputString("cross_account_principal_no_trust_arn")
+		require.NoError(err)
 
-	// Take the returned hosts by ID and create the same kind of map.
-	actualInstances := make(map[string][]string)
-	for _, host := range response.GetHosts() {
-		actualInstances[host.ExternalId] = host.SetIds
-	}
+		crossAccountTargetArn, err := tf.GetOutputString("cross_account_target_arn")
+		require.NoError(err)
 
-	// Compare
-	require.Equal(expectedInstances, actualInstances)
-	// Success
-	t.Logf("testing ListHosts: success (region=%s, tags=%v, expected/actual=(len=%d, ids=%s))", region, tags, len(actualInstances), actualInstances)
-}
+		crossAccountTargetNoTrustArn, err := tf.GetOutputString("cross_account_target_no_trust_arn")
+		require.NoError(err)
 
-func testInstanceAddressesOnlyListHosts(ctx context.Context, t *testing.T, p *host.HostPlugin, tf *TestTerraformer, region, accessKeyId, secretAccessKey string) {
-	t.Helper()
-	t.Logf("testing testInstanceAddressesOnlyListHosts")
+		crossAccountTargetNoEc2PermissionArn, err := tf.GetOutputString("cross_account_target_no_ec2_permission_arn")
+		require.NoError(err)
 
-	// Get the instance details from tf output
-	instanceID, err := tf.GetOutputString("multi_address_instance_id")
-	require.NoError(t, err)
-	primaryAddresses, err := tf.GetOutputMap("multi_address_primary_addresses")
-	require.NoError(t, err)
-	secondaryAddresses, err := tf.GetOutputMap("multi_address_secondary_addresses")
-	require.NoError(t, err)
+		targetEc2InstanceIds, err := tf.GetOutputSlice("target_instance_ids")
+		require.NoError(err)
+		require.Len(targetEc2InstanceIds, expectedEc2InstanceCount)
 
-	var primary, allAddresses []string
-	for _, addr := range primaryAddresses {
-		primary = append(primary, addr.(string))
-	}
-	allAddresses = append(allAddresses, primary...)
-	for _, addr := range secondaryAddresses {
-		allAddresses = append(allAddresses, addr.(string))
-	}
+		targetEc2InstanceTags, err := tf.GetOutputMap("target_instance_tags")
+		require.NoError(err)
+		expectedTargetTagInstancesMap := buildExpectedTagInstancesMap(targetEc2InstanceTags, expectedTags)
 
-	cases := []struct {
-		name                  string
-		instanceAddressesOnly bool
-		expectedIPs           []string
-	}{
-		{
-			name:        "all addresses",
-			expectedIPs: allAddresses,
-		},
-		{
-			name:                  "instance addresses only",
-			instanceAddressesOnly: true,
-			expectedIPs:           primary,
-		},
-	}
+		requireTagInstancesMatchProvisioned(t, targetEc2InstanceIds, expectedTargetTagInstancesMap)
 
-	for _, tc := range cases {
-		tc := tc
-		t.Run(tc.name, func(t *testing.T) {
-			require := require.New(t)
-
-			catalogAttrMap := map[string]any{
-				credential.ConstRegion:                    region,
-				credential.ConstDisableCredentialRotation: true,
-			}
-			if tc.instanceAddressesOnly {
-				catalogAttrMap[host.ConstInstanceAddressesOnly] = true
-			}
-
-			catalogAttrs, err := structpb.NewStruct(catalogAttrMap)
-			require.NoError(err)
-			setAttrs, err := structpb.NewStruct(map[string]any{
-				host.ConstDescribeInstancesFilters: []any{fmt.Sprintf("instance-id=%s", instanceID)},
-			})
-			require.NoError(err)
-
-			reqPersistedSecrets, err := structpb.NewStruct(map[string]any{
-				credential.ConstAccessKeyId:          accessKeyId,
-				credential.ConstSecretAccessKey:      secretAccessKey,
-				credential.ConstCredsLastRotatedTime: (time.Time{}).Format(time.RFC3339Nano),
-			})
-			require.NoError(err)
-			request := &pb.ListHostsRequest{
-				Catalog: &hostcatalogs.HostCatalog{
-					Attrs: &hostcatalogs.HostCatalog_Attributes{
-						Attributes: catalogAttrs,
-					},
-				},
-				Sets: []*hostsets.HostSet{{
-					Id:    "hostset-0",
-					Attrs: &hostsets.HostSet_Attributes{Attributes: setAttrs},
-				}},
-				Persisted: &pb.HostCatalogPersisted{
-					Secrets: reqPersistedSecrets,
-				},
-			}
-
-			response, err := p.ListHosts(ctx, request)
-			require.NoError(err)
-			require.Len(response.GetHosts(), 1)
-			hostResp := response.GetHosts()[0]
-
-			require.Equal(instanceID, hostResp.ExternalId)
-			require.ElementsMatch(hostResp.IpAddresses, tc.expectedIPs)
+		testOnCreateCatalogCases(ctx, t, p, []onCreateCatalogCase{
+			{name: "cross-account happy path", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetArn)},
+			{name: "cross-account principal no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalNoTrustArn, crossAccountTargetArn), wantErr: "AccessDenied"},
+			{name: "cross-account target no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoTrustArn), wantErr: "AccessDenied"},
+			{name: "cross-account target missing ec2 permission", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
+		})
+		testOnUpdateCatalogCases(ctx, t, p, []onUpdateCatalogCase{
+			{name: "cross-account happy path", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetArn)},
+			{name: "cross-account principal no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalNoTrustArn, crossAccountTargetArn), wantErr: "AccessDenied"},
+			{name: "cross-account target no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoTrustArn), wantErr: "AccessDenied"},
+			{name: "cross-account target missing ec2 permission", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
+		})
+		testOnCreateSetCases(ctx, t, p, []onSetCase{
+			{name: "cross-account happy path", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetArn), tags: cases[0]},
+			{name: "cross-account principal no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalNoTrustArn, crossAccountTargetArn), wantErr: "AccessDenied"},
+			{name: "cross-account target no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoTrustArn), wantErr: "AccessDenied"},
+			{name: "cross-account target missing ec2 permission", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
+		})
+		testOnUpdateSetCases(ctx, t, p, []onSetCase{
+			{name: "cross-account happy path", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetArn), tags: cases[0]},
+			{name: "cross-account principal no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalNoTrustArn, crossAccountTargetArn), wantErr: "AccessDenied"},
+			{name: "cross-account target no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoTrustArn), wantErr: "AccessDenied"},
+			{name: "cross-account target missing ec2 permission", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoEc2PermissionArn), wantErr: "UnauthorizedOperation"},
+		})
+		testListHostsCases(ctx, t, p, []listHostsCase{
+			{name: "cross-account happy path", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetArn), tags: cases[0], expected: expectedTargetTagInstancesMap},
+			{name: "cross-account principal no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalNoTrustArn, crossAccountTargetArn), tags: cases[0], wantErr: "AccessDenied"},
+			{name: "cross-account target no trust", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoTrustArn), tags: cases[0], wantErr: "AccessDenied"},
+			{name: "cross-account target missing ec2 permission", catalogAttrs: crossRoleAttrs(targetRegion, crossAccountPrincipalArn, crossAccountTargetNoEc2PermissionArn), tags: cases[0], wantErr: "UnauthorizedOperation"},
 		})
 	}
 }

testing/testdata/host/iam_assume_role.tf

@@ -0,0 +1,206 @@
+# Copyright IBM Corp. 2021, 2026
+# SPDX-License-Identifier: MPL-2.0
+
+resource "random_id" "assume_role_name" {
+  prefix      = "BoundaryPluginAssumeRole"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "assume_role" {
+  name = random_id.assume_role_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Principal = {
+          AWS = data.aws_caller_identity.current.arn
+        }
+      },
+      # Also trusted by the cross-role principal role so it can be used
+      # as the target in two-hop AssumeRole tests.
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Principal = {
+          AWS = aws_iam_role.cross_role_principal.arn
+        }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+resource "aws_iam_role_policy_attachment" "assume_role_ec2_describeinstances" {
+  role       = aws_iam_role.assume_role.name
+  policy_arn = aws_iam_policy.ec2_describeinstances.arn
+}
+
+output "assume_role_arn" {
+  value = aws_iam_role.assume_role.arn
+}
+
+# Error case: role exists with ec2:DescribeInstances but trust policy
+# does not allow the caller to assume it.
+resource "random_id" "assume_role_no_trust_name" {
+  prefix      = "BoundaryPluginNoTrust"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "assume_role_no_trust" {
+  name = random_id.assume_role_no_trust_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Deny"
+        Principal = {
+          AWS = data.aws_caller_identity.current.arn
+        }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+output "assume_role_no_trust_arn" {
+  value = aws_iam_role.assume_role_no_trust.arn
+}
+
+# Error case: role exists and the caller can assume it, but has no
+# ec2:DescribeInstances permission.
+# Also trusted by cross_role_principal so this same role can be reused as the
+# no-EC2-permission target in two-hop (cross-role) error case tests.
+resource "random_id" "assume_role_no_ec2_permission_name" {
+  prefix      = "BoundaryPluginNoEC2Perm"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "assume_role_no_ec2_permission" {
+  name = random_id.assume_role_no_ec2_permission_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Principal = {
+          AWS = data.aws_caller_identity.current.arn
+        }
+      },
+      # Also trusted by the cross-role principal so it can serve as the
+      # no-EC2-permission target in two-hop error case tests.
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Principal = {
+          AWS = aws_iam_role.cross_role_principal.arn
+        }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+output "assume_role_no_ec2_permission_arn" {
+  value = aws_iam_role.assume_role_no_ec2_permission.arn
+}
+
+# Cross-role (two-hop) principal role.
+# The test runner can assume this role. It has permission to AssumeRole into
+# aws_iam_role.assume_role (the target role) but has no ec2:DescribeInstances
+# of its own. This simulates the principal side of a two-hop role chain: the
+# plugin must assume the principal first, then use those credentials to assume
+# the target role before calling DescribeInstances.
+# Note: both roles are in the same AWS account. This tests the plugin's
+# two-hop credential chain logic without requiring a second account.
+resource "random_id" "cross_role_principal_name" {
+  prefix      = "BoundaryPluginCRPrincipal"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "cross_role_principal" {
+  name = random_id.cross_role_principal_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Principal = {
+          AWS = data.aws_caller_identity.current.arn
+        }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+# Single policy granting cross_role_principal permission to assume all target
+# roles it needs for both happy path and error case tests.
+resource "aws_iam_policy" "cross_role_principal_assume_targets" {
+  name = "${random_id.cross_role_principal_name.dec}-assume-targets"
+
+  policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect = "Allow"
+        Resource = [
+          aws_iam_role.assume_role.arn,
+          aws_iam_role.assume_role_no_ec2_permission.arn,
+        ]
+      },
+    ]
+  })
+}
+
+resource "aws_iam_role_policy_attachment" "cross_role_principal_assume_targets" {
+  role       = aws_iam_role.cross_role_principal.name
+  policy_arn = aws_iam_policy.cross_role_principal_assume_targets.arn
+}
+
+output "cross_role_principal_arn" {
+  value = aws_iam_role.cross_role_principal.arn
+}
+
+# Error case: caller cannot assume the principal role (first hop denied).
+# Reuses assume_role_no_trust — it already has a Deny trust policy for the
+# caller, so it also serves as an unassumable principal in two-hop tests.
+output "cross_role_principal_no_trust_arn" {
+  value = aws_iam_role.assume_role_no_trust.arn
+}
+
+# Error case: principal can be assumed, but the target role's trust policy
+# does not allow the principal to assume it (second hop denied).
+# Reuses assume_role_no_trust as the target — its Deny trust policy blocks
+# all callers including cross_role_principal.
+output "cross_role_target_no_trust_arn" {
+  value = aws_iam_role.assume_role_no_trust.arn
+}
+
+# Error case: both hops succeed but the target has no ec2:DescribeInstances.
+# Reuses assume_role_no_ec2_permission — its trust policy allows
+# cross_role_principal (see above), and it has no EC2 permission.
+output "cross_role_target_no_ec2_permission_arn" {
+  value = aws_iam_role.assume_role_no_ec2_permission.arn
+}

testing/testdata/host/iam_cross_account.tf

@@ -0,0 +1,322 @@
+# Copyright IBM Corp. 2021, 2026
+# SPDX-License-Identifier: MPL-2.0
+
+# Cross-account Dynamic Host Catalog test infrastructure.
+#
+# This file provisions the IAM resources needed to test two-hop AssumeRole
+# across two separate AWS accounts:
+#
+#   Account A (principal account) — the default provider
+#     * cross_account_principal: the plugin assumes this role first.
+#       It has sts:AssumeRole permission on the target role in Account B.
+#
+#   Account B (target account) — the "target" provider alias
+#     * cross_account_target: holds ec2:DescribeInstances; its trust policy
+#       allows the Account A principal role to assume it. (happy path)
+#     * cross_account_target_no_ec2_permission: same trust policy but no
+#       ec2:DescribeInstances. (error case)
+#     * cross_account_target_no_trust: exists in Account B but its trust
+#       policy does not allow the Account A principal. (error case)
+#
+# Prerequisites:
+#   TARGET_AWS_ACCESS_KEY_ID, TARGET_AWS_SECRET_ACCESS_KEY, and (for temporary
+#   credentials) TARGET_AWS_SESSION_TOKEN must be set to credentials that have
+#   sufficient IAM permissions in Account B. The test runner skips this
+#   section when the access key ID or secret access key are absent.
+
+# ---------------------------------------------------------------------------
+# Provider for Account B (target account)
+# ---------------------------------------------------------------------------
+
+provider "aws" {
+  alias      = "target"
+  region     = var.target_region
+  access_key = var.target_access_key_id
+  secret_key = var.target_secret_access_key
+  token      = var.target_session_token
+}
+
+data "aws_caller_identity" "target" {
+  provider = aws.target
+}
+
+# ---------------------------------------------------------------------------
+# Variables for Account B credentials and region
+# ---------------------------------------------------------------------------
+
+variable "target_access_key_id" {
+  description = "AWS access key ID for the target account (Account B)."
+  type        = string
+  sensitive   = true
+  default     = ""
+}
+
+variable "target_secret_access_key" {
+  description = "AWS secret access key for the target account (Account B)."
+  type        = string
+  sensitive   = true
+  default     = ""
+}
+
+variable "target_session_token" {
+  description = "AWS session token for the target account (Account B). Required when using temporary (STS) credentials."
+  type        = string
+  sensitive   = true
+  default     = ""
+}
+
+variable "target_region" {
+  description = "AWS region for the target account (Account B). Defaults to the same region as Account A."
+  type        = string
+  default     = ""
+}
+
+# ---------------------------------------------------------------------------
+# Account A: cross_account_principal role
+# ---------------------------------------------------------------------------
+
+resource "random_id" "cross_account_principal_name" {
+  prefix      = "BoundaryPluginCAPrincipal"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "cross_account_principal" {
+  name = random_id.cross_account_principal_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action    = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect    = "Allow"
+        Principal = { AWS = data.aws_caller_identity.current.arn }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+# Allow the principal role to assume the happy-path and no-EC2-permission
+# target roles in Account B.
+resource "aws_iam_policy" "cross_account_principal_assume_targets" {
+  name = "${random_id.cross_account_principal_name.dec}-assume-targets"
+
+  policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action   = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect   = "Allow"
+        Resource = [
+          aws_iam_role.cross_account_target.arn,
+          aws_iam_role.cross_account_target_no_ec2_permission.arn,
+        ]
+      },
+    ]
+  })
+}
+
+resource "aws_iam_role_policy_attachment" "cross_account_principal_assume_targets" {
+  role       = aws_iam_role.cross_account_principal.name
+  policy_arn = aws_iam_policy.cross_account_principal_assume_targets.arn
+}
+
+output "cross_account_principal_arn" {
+  value = aws_iam_role.cross_account_principal.arn
+}
+
+# Error case: caller cannot assume the principal role (first hop denied).
+# Reuses assume_role_no_trust from iam_assume_role.tf — its Deny trust policy
+# also blocks the test runner from assuming it as a principal.
+output "cross_account_principal_no_trust_arn" {
+  value = aws_iam_role.assume_role_no_trust.arn
+}
+
+# ---------------------------------------------------------------------------
+# Account B: happy-path target role
+# ---------------------------------------------------------------------------
+
+resource "random_id" "cross_account_target_name" {
+  prefix      = "BoundaryPluginCATarget"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "cross_account_target" {
+  provider = aws.target
+  name     = random_id.cross_account_target_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action    = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect    = "Allow"
+        Principal = { AWS = aws_iam_role.cross_account_principal.arn }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+resource "aws_iam_policy" "cross_account_target_ec2_describeinstances" {
+  provider = aws.target
+  name     = "${random_id.cross_account_target_name.dec}-ec2"
+
+  policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action   = ["ec2:DescribeInstances"]
+        Effect   = "Allow"
+        Resource = "*"
+      },
+    ]
+  })
+}
+
+resource "aws_iam_role_policy_attachment" "cross_account_target_ec2_describeinstances" {
+  provider   = aws.target
+  role       = aws_iam_role.cross_account_target.name
+  policy_arn = aws_iam_policy.cross_account_target_ec2_describeinstances.arn
+}
+
+output "cross_account_target_arn" {
+  value = aws_iam_role.cross_account_target.arn
+}
+
+# ---------------------------------------------------------------------------
+# Account B: error case — both hops succeed but target has no ec2:DescribeInstances
+# ---------------------------------------------------------------------------
+
+resource "random_id" "cross_account_target_no_ec2_permission_name" {
+  prefix      = "BoundaryPluginCATargetNoEC2"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "cross_account_target_no_ec2_permission" {
+  provider = aws.target
+  name     = random_id.cross_account_target_no_ec2_permission_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action    = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect    = "Allow"
+        Principal = { AWS = aws_iam_role.cross_account_principal.arn }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+output "cross_account_target_no_ec2_permission_arn" {
+  value = aws_iam_role.cross_account_target_no_ec2_permission.arn
+}
+
+# ---------------------------------------------------------------------------
+# Account B: error case — principal cannot assume this target (second hop denied)
+# ---------------------------------------------------------------------------
+
+resource "random_id" "cross_account_target_no_trust_name" {
+  prefix      = "BoundaryPluginCATargetNoTrust"
+  byte_length = 4
+}
+
+resource "aws_iam_role" "cross_account_target_no_trust" {
+  provider = aws.target
+  name     = random_id.cross_account_target_no_trust_name.dec
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Action    = ["sts:AssumeRole", "sts:SetSourceIdentity"]
+        Effect    = "Deny"
+        Principal = { AWS = aws_iam_role.cross_account_principal.arn }
+      },
+    ]
+  })
+
+  tags = {
+    "boundary-demo" = local.hashicorp_email
+  }
+}
+
+output "cross_account_target_no_trust_arn" {
+  value = aws_iam_role.cross_account_target_no_trust.arn
+}
+
+# ---------------------------------------------------------------------------
+# Account B: EC2 instance for cross-account host discovery validation
+# ---------------------------------------------------------------------------
+
+data "aws_availability_zones" "target_azs" {
+  count    = var.target_access_key_id != "" ? 1 : 0
+  provider = aws.target
+}
+
+data "aws_ami" "target_ubuntu" {
+  count       = var.target_access_key_id != "" ? 1 : 0
+  provider    = aws.target
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["099720109477"] # Canonical
+}
+
+resource "aws_vpc" "target_vpc" {
+  count                            = var.target_access_key_id != "" ? 1 : 0
+  provider                         = aws.target
+  cidr_block                       = "10.1.0.0/16"
+  assign_generated_ipv6_cidr_block = true
+}
+
+resource "aws_subnet" "target_subnet" {
+  count                           = var.target_access_key_id != "" ? 1 : 0
+  provider                        = aws.target
+  vpc_id                          = aws_vpc.target_vpc[0].id
+  cidr_block                      = aws_vpc.target_vpc[0].cidr_block
+  ipv6_cidr_block                 = cidrsubnet(aws_vpc.target_vpc[0].ipv6_cidr_block, 8, 0)
+  availability_zone               = data.aws_availability_zones.target_azs[0].names[0]
+  map_public_ip_on_launch         = true
+  assign_ipv6_address_on_creation = true
+}
+
+resource "aws_instance" "target_instances" {
+  count         = var.target_access_key_id != "" ? length(local.instance_tags) : 0
+  provider      = aws.target
+  ami           = data.aws_ami.target_ubuntu[0].id
+  instance_type = "t3.nano"
+  subnet_id     = aws_subnet.target_subnet[0].id
+
+  tags = local.instance_tags[count.index]
+}
+
+output "target_instance_ids" {
+  value = aws_instance.target_instances.*.id
+}
+
+output "target_instance_tags" {
+  value = {
+    for _, r in aws_instance.target_instances : r.id => r.tags
+  }
+}

testing/testing.go

@@ -39,6 +39,10 @@ type TestTerraformer struct {
 	// The working directory for Terraform commands.
 	workDir string
 
+	// vars holds optional key/value pairs passed as -var flags to every
+	// Terraform command that accepts them (apply, destroy, plan).
+	vars map[string]string
+
 	// The Terraform state. Use the Output method to look up particular
 	// outputs from the Terraform state.
 	state *tfjson.State
@@ -53,8 +57,9 @@ type TestTerraformer struct {
 
 // NewTestTerraformer initializes a Terraform directory. It just
 // returns an initialized project, it does not perform any actions on
-// it.
-func NewTestTerraformer(workDir string) (*TestTerraformer, error) {
+// it. An optional vars map may be provided; each entry is passed as a
+// -var flag to Terraform commands.
+func NewTestTerraformer(workDir string, vars ...map[string]string) (*TestTerraformer, error) {
 	tfPath, err := exec.LookPath("terraform")
 	if err != nil {
 		return nil, fmt.Errorf("LookPath error: %w", err)
@@ -64,10 +69,24 @@ func NewTestTerraformer(workDir string) (*TestTerraformer, error) {
 		return nil, errors.New("workDir is empty")
 	}
 
-	return &TestTerraformer{
+	tf := &TestTerraformer{
 		tfPath:  tfPath,
 		workDir: workDir,
-	}, nil
+	}
+	if len(vars) > 0 {
+		tf.vars = vars[0]
+	}
+	return tf, nil
+}
+
+// varArgs converts the stored vars map into a slice of -var flags
+// suitable for appending to a Terraform command's argument list.
+func (t *TestTerraformer) varArgs() []string {
+	args := make([]string, 0, len(t.vars)*2)
+	for k, v := range t.vars {
+		args = append(args, "-var", fmt.Sprintf("%s=%s", k, v))
+	}
+	return args
 }
 
 // Deploy runs the following commands, in order: init, apply, plan,
@@ -214,7 +233,8 @@ func (t *TestTerraformer) init() error {
 
 // apply runs "terraform apply" in the project's working directory.
 func (t *TestTerraformer) apply() error {
-	cmd := exec.Command(t.tfPath, "apply", "-input=false", "-auto-approve")
+	args := append([]string{"apply", "-input=false", "-auto-approve"}, t.varArgs()...)
+	cmd := exec.Command(t.tfPath, args...)
 	cmd.Dir = t.workDir
 	stdoutStderr, err := cmd.CombinedOutput()
 	if err != nil {
@@ -226,7 +246,8 @@ func (t *TestTerraformer) apply() error {
 
 // destroy runs "terraform destroy" in the project's working directory.
 func (t *TestTerraformer) destroy() error {
-	cmd := exec.Command(t.tfPath, "destroy", "-input=false", "-auto-approve")
+	args := append([]string{"destroy", "-input=false", "-auto-approve"}, t.varArgs()...)
+	cmd := exec.Command(t.tfPath, args...)
 	cmd.Dir = t.workDir
 	stdoutStderr, err := cmd.CombinedOutput()
 	if err != nil {
@@ -242,7 +263,8 @@ func (t *TestTerraformer) destroy() error {
 // it's run to get the data for for importing the state via
 // terraform-json. The apply method ignores the plan generated here.
 func (t *TestTerraformer) plan() error {
-	cmd := exec.Command(t.tfPath, "plan", "-input=false", "-out=plan.tfplan")
+	args := append([]string{"plan", "-input=false", "-out=plan.tfplan"}, t.varArgs()...)
+	cmd := exec.Command(t.tfPath, args...)
 	cmd.Dir = t.workDir
 	stdoutStderr, err := cmd.CombinedOutput()
 	if err != nil {