refactor(host): propagate BadRequestStatusf from buildFilters through buildDescribeInstancesInput

Set GITHUB_TOKEN to read-only permission by default

.github/workflows/test.yml

@@ -4,6 +4,8 @@ on:
   - workflow_dispatch
   - push
 
+permissions: read-all
+
 jobs:
   test:
     runs-on: ubuntu-latest

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/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 +37,18 @@ 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"
+const errBuildDescribeInstancesInput = "error building DescribeInstances input: %s"
+const errDryRunFailed = "error performing DescribeInstances dry run: %s"
+
 // Ensure that we are implementing HostPluginServiceServer
 var _ pb.HostPluginServiceServer = (*HostPlugin)(nil)
 
@@ -82,13 +99,18 @@ func (p *HostPlugin) OnCreateCatalog(ctx context.Context, req *pb.OnCreateCatalo
 		return nil, errors.BadRequestStatusf("error setting up persisted state: %s", err)
 	}
 
-	// perform dry run to ensure we can interact with AWS as expected.
 	opts := []ec2Option{}
 	if catalogAttributes.DualStack {
 		opts = append(opts, WithDualStack(catalogAttributes.DualStack))
 	}
-	if st := dryRunValidation(ctx, catalogState, opts); st != nil {
-		return nil, st.Err()
+	input, err := buildDescribeInstancesInput(&SetAttributes{}, true)
+	if err != nil {
+		return nil, status.Errorf(codes.Unknown, errBuildDescribeInstancesInput, err)
+	}
+	// Run a DescribeInstances request with DryRun set to true to ensure
+	// we can interact with AWS resources as expected.
+	if _, err := checkHosts(ctx, catalogState, input, opts, catalogAttributes.TargetAccount); err != nil {
+		return nil, fmt.Errorf(errDryRunFailed, err)
 	}
 
 	persistedProto, err := catalogState.toProto()
@@ -171,12 +193,19 @@ func (p *HostPlugin) OnUpdateCatalog(ctx context.Context, req *pb.OnUpdateCatalo
 		if err != nil {
 			return nil, errors.BadRequestStatusf("error loading persisted state: %s", err)
 		}
+
 		opts := []ec2Option{}
 		if newCatalogAttributes.DualStack {
 			opts = append(opts, WithDualStack(newCatalogAttributes.DualStack))
 		}
-		if st := dryRunValidation(ctx, newCatalogState, opts); st != nil {
-			return nil, st.Err()
+		input, err := buildDescribeInstancesInput(&SetAttributes{}, true)
+		if err != nil {
+			return nil, status.Errorf(codes.Unknown, errBuildDescribeInstancesInput, err)
+		}
+		// Run a DescribeInstances request with DryRun set to true to ensure
+		// we can interact with AWS resources as expected.
+		if _, err := checkHosts(ctx, newCatalogState, input, opts, newCatalogAttributes.TargetAccount); err != nil {
+			return nil, fmt.Errorf(errDryRunFailed, err)
 		}
 
 		// Replace the existing credential state.
@@ -216,13 +245,18 @@ func (p *HostPlugin) OnUpdateCatalog(ctx context.Context, req *pb.OnUpdateCatalo
 		return nil, errors.BadRequestStatusf("error loading persisted state: %s", err)
 	}
 
-	// perform dry run to ensure we can interact with AWS as expected.
 	opts := []ec2Option{}
 	if newCatalogAttributes.DualStack {
 		opts = append(opts, WithDualStack(newCatalogAttributes.DualStack))
 	}
-	if st := dryRunValidation(ctx, catalogState, opts); st != nil {
-		return nil, st.Err()
+	input, err := buildDescribeInstancesInput(&SetAttributes{}, true)
+	if err != nil {
+		return nil, status.Errorf(codes.Unknown, errBuildDescribeInstancesInput, err)
+	}
+	// Run a DescribeInstances request with DryRun set to true to ensure
+	// we can interact with AWS resources as expected.
+	if _, err := checkHosts(ctx, catalogState, input, opts, newCatalogAttributes.TargetAccount); err != nil {
+		return nil, fmt.Errorf(errDryRunFailed, err)
 	}
 
 	persistedProto, err := catalogState.toProto()
@@ -366,18 +400,20 @@ func (p *HostPlugin) OnCreateSet(ctx context.Context, req *pb.OnCreateSetRequest
 		return nil, err
 	}
 
-	describeInstanceFilters, err := buildFilters(setAttrs)
-	if err != nil {
-		return nil, errors.BadRequestStatusf("error building set filters: %s", err)
-	}
-
 	opts := []ec2Option{}
 	if catalogAttributes.DualStack {
 		opts = append(opts, WithDualStack(catalogAttributes.DualStack))
 	}
-	if st := dryRunValidation(ctx, catalogState, opts, describeInstanceFilters...); st != nil {
-		return nil, st.Err()
+	input, err := buildDescribeInstancesInput(setAttrs, true)
+	if err != nil {
+		return nil, status.Errorf(codes.Unknown, errBuildDescribeInstancesInput, err)
 	}
+	// Run a DescribeInstances request with DryRun set to true to ensure
+	// we can interact with AWS resources as expected.
+	if _, err := checkHosts(ctx, catalogState, input, opts, catalogAttributes.TargetAccount); err != nil {
+		return nil, fmt.Errorf(errDryRunFailed, err)
+	}
+
 	return &pb.OnCreateSetResponse{}, nil
 }
 
@@ -431,17 +467,18 @@ func (p *HostPlugin) OnUpdateSet(ctx context.Context, req *pb.OnUpdateSetRequest
 		return nil, err
 	}
 
-	describeInstanceFilters, err := buildFilters(setAttrs)
-	if err != nil {
-		return nil, errors.BadRequestStatusf("error building set filters: %s", err)
-	}
-
 	opts := []ec2Option{}
 	if catalogAttributes.DualStack {
 		opts = append(opts, WithDualStack(catalogAttributes.DualStack))
 	}
-	if st := dryRunValidation(ctx, catalogState, opts, describeInstanceFilters...); st != nil {
-		return nil, st.Err()
+	input, err := buildDescribeInstancesInput(setAttrs, true)
+	if err != nil {
+		return nil, status.Errorf(codes.Unknown, errBuildDescribeInstancesInput, err)
+	}
+	// Run a DescribeInstances request with DryRun set to true to ensure
+	// we can interact with AWS resources as expected.
+	if _, err := checkHosts(ctx, catalogState, input, opts, catalogAttributes.TargetAccount); err != nil {
+		return nil, fmt.Errorf(errDryRunFailed, err)
 	}
 
 	return &pb.OnUpdateSetResponse{}, nil
@@ -495,13 +532,6 @@ 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 +561,22 @@ 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).
@@ -601,11 +633,11 @@ func buildFilters(attrs *SetAttributes) ([]types.Filter, error) {
 		splitFilter := strings.Split(filterAttr, "=")
 		switch {
 		case len(splitFilter) != 2:
-			return nil, fmt.Errorf("expected filter %q to contain a single equal sign", filterAttr)
+			return nil, errors.BadRequestStatusf("expected filter %q to contain a single equal sign", filterAttr)
 		case len(splitFilter[0]) == 0:
-			return nil, fmt.Errorf("filter %q contains an empty filter key", filterAttr)
+			return nil, errors.BadRequestStatusf("filter %q contains an empty filter key", filterAttr)
 		case len(splitFilter[1]) == 0:
-			return nil, fmt.Errorf("filter %q contains an empty value", filterAttr)
+			return nil, errors.BadRequestStatusf("filter %q contains an empty value", filterAttr)
 		}
 
 		filterKey, filterValue := splitFilter[0], splitFilter[1]
@@ -636,7 +668,7 @@ func buildFilters(attrs *SetAttributes) ([]types.Filter, error) {
 func buildDescribeInstancesInput(attrs *SetAttributes, dryRun bool) (*ec2.DescribeInstancesInput, error) {
 	filters, err := buildFilters(attrs)
 	if err != nil {
-		return nil, fmt.Errorf("error building filters: %w", err)
+		return nil, err
 	}
 
 	return &ec2.DescribeInstancesInput{
@@ -707,26 +739,115 @@ func awsInstanceToHost(instance types.Instance, catalogAttributes *CatalogAttrib
 	return result, 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
-// host set validation.
-func dryRunValidation(ctx context.Context, state *awsCatalogPersistedState, ec2Opts []ec2Option, filters ...types.Filter) *status.Status {
-	if state == nil {
-		return status.New(codes.InvalidArgument, "persisted state is required")
+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")
 	}
 
-	ec2Client, err := state.EC2Client(ctx, ec2Opts...)
+	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 {
-		return status.New(codes.InvalidArgument, fmt.Sprintf("error getting EC2 client: %s", err))
+		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
 	}
 
-	_, err = ec2Client.DescribeInstances(ctx, &ec2.DescribeInstancesInput{Filters: filters})
+	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 status.New(codes.FailedPrecondition, fmt.Sprintf("aws describe instances failed: %s", err))
+		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")
 	}
 
-	return nil
+	// 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
 }
 
 // appendDistinct will append the elements to the slice

plugin/service/host/plugin_test.go

@@ -742,8 +742,11 @@ func TestPluginOnCreateCatalogErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: "aws describe instances failed: DescribeInstances error",
-			expectedErrCode:     codes.FailedPrecondition,
+			// checkHosts returns the DescribeInstances error as-is rather than
+			// wrapping it in a gRPC FailedPrecondition status like the old
+			// dryRunValidation did. A plain Go error maps to codes.Unknown.
+			expectedErrContains: testDescribeInstancesError,
+			expectedErrCode:     codes.Unknown,
 		},
 	}
 
@@ -994,8 +997,11 @@ func TestPluginOnUpdateCatalogErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: "aws describe instances failed: DescribeInstances error",
-			expectedErrCode:     codes.FailedPrecondition,
+			//checkHosts returns the DesribeInstances errror as-is rather than wrapping it
+			// in a gRpc FailedPrecodndition status like the old dryRunValidiation did.
+			// A plain Go error maps to codeds.Unknown.
+			expectedErrContains: testDescribeInstancesError,
+			expectedErrCode:     codes.Unknown,
 		},
 		{
 			name: "new incoming dynamic credential update dry run error",
@@ -1036,8 +1042,11 @@ func TestPluginOnUpdateCatalogErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: "aws describe instances failed: DescribeInstances error",
-			expectedErrCode:     codes.FailedPrecondition,
+			// checkHosts returns the DescribeInstances error as-is rather than wrapping it
+			// in a gRPC FailedPrecondition status like the old dryRunValidiation did.
+			// A plain Go error maps to codes.Unknown.
+			expectedErrContains: testDescribeInstancesError,
+			expectedErrCode:     codes.Unknown,
 		},
 		{
 			name: "replace creds error",
@@ -1211,8 +1220,11 @@ func TestPluginOnUpdateCatalogErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(fmt.Errorf("oops there was an error")),
 				)),
 			},
-			expectedErrContains: "aws describe instances failed: oops there was an error",
-			expectedErrCode:     codes.FailedPrecondition,
+			// checkHosts returns the DescribeInstances error as-is rather than wrapping it
+			// in a gRPC FailedPrecondition status like the old dryRunValidiation did.
+			// A plain Go error maps to codes.Unknown.
+			expectedErrContains: "oops there was an error",
+			expectedErrCode:     codes.Unknown,
 		},
 	}
 
@@ -1565,8 +1577,8 @@ func TestPluginOnCreateSetErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: fmt.Sprintf("aws describe instances failed: %s", testDescribeInstancesError),
-			expectedErrCode:     codes.FailedPrecondition,
+			expectedErrContains: testDescribeInstancesError,
+			expectedErrCode:     codes.Unknown,
 		},
 	}
 
@@ -1828,8 +1840,8 @@ func TestPluginOnUpdateSetErr(t *testing.T) {
 					testMockEC2WithDescribeInstancesError(errors.New(testDescribeInstancesError)),
 				)),
 			},
-			expectedErrContains: fmt.Sprintf("aws describe instances failed: %s", testDescribeInstancesError),
-			expectedErrCode:     codes.FailedPrecondition,
+			expectedErrContains: testDescribeInstancesError,
+			expectedErrCode:     codes.Unknown,
 		},
 	}
 
@@ -1849,6 +1861,162 @@ 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 +2298,101 @@ 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,
 		},
 		{
@@ -2821,54 +3083,3 @@ func TestAppendDistinct(t *testing.T) {
 		})
 	}
 }
-
-func TestDryRunValidation(t *testing.T) {
-	t.Run("nil credential state", func(t *testing.T) {
-		st := dryRunValidation(context.Background(), nil, nil)
-		require.NotNil(t, st)
-		require.Equal(t, codes.InvalidArgument.String(), st.Code().String())
-		require.Equal(t, "persisted state is required", st.Message())
-	})
-
-	t.Run("ec2ClientErr", func(t *testing.T) {
-		st := dryRunValidation(context.Background(), &awsCatalogPersistedState{
-			AwsCredentialPersistedState: &credential.AwsCredentialPersistedState{
-				CredentialsConfig: &awsutil.CredentialsConfig{},
-			},
-			testEC2APIFunc: func(...aws.Config) (EC2API, error) {
-				return nil, fmt.Errorf("oops ec2 client err")
-			},
-		}, []ec2Option{})
-		require.NotNil(t, st)
-		require.Equal(t, codes.InvalidArgument.String(), st.Code().String())
-		require.Equal(t, "error getting EC2 client: oops ec2 client err", st.Message())
-	})
-
-	t.Run("describeInstancesErr", func(t *testing.T) {
-		st := dryRunValidation(context.Background(), &awsCatalogPersistedState{
-			AwsCredentialPersistedState: &credential.AwsCredentialPersistedState{
-				CredentialsConfig: &awsutil.CredentialsConfig{
-					AccessKey: "AKIAfoo",
-					SecretKey: "baz",
-				},
-			},
-			testEC2APIFunc: newTestMockEC2(nil, testMockEC2WithDescribeInstancesError(fmt.Errorf("oops describe instances error"))),
-		}, []ec2Option{})
-		require.NotNil(t, st)
-		require.Equal(t, codes.FailedPrecondition.String(), st.Code().String())
-		require.Equal(t, "aws describe instances failed: oops describe instances error", st.Message())
-	})
-
-	t.Run("success", func(t *testing.T) {
-		st := dryRunValidation(context.Background(), &awsCatalogPersistedState{
-			AwsCredentialPersistedState: &credential.AwsCredentialPersistedState{
-				CredentialsConfig: &awsutil.CredentialsConfig{
-					AccessKey: "AKIAfoo",
-					SecretKey: "baz",
-				},
-			},
-			testEC2APIFunc: newTestMockEC2(nil, testMockEC2WithDescribeInstancesOutput(&ec2.DescribeInstancesOutput{})),
-		}, []ec2Option{})
-		require.Nil(t, st)
-	})
-}

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 {

plugin/service/storage/plugin.go

@@ -665,6 +665,23 @@ func (p *StoragePlugin) GetObject(req *pb.GetObjectRequest, stream pb.StoragePlu
 	return nil
 }
 
+const (
+	// multipartThreshold is the file size, in bytes, above which PutObject
+	// uploads an object using a multipart upload instead of a single PutObject
+	// request. 8 MiB matches the AWS CLI and boto3 defaults.
+	multipartThreshold = 8 * 1024 * 1024 // 8 MiB
+
+	// defaultMultipartPartSize is the default size, in bytes, of each part
+	// uploaded during a multipart upload. It is kept equal to
+	// multipartThreshold so a multipart upload always has at least two parts
+	// (S3 requires every part except the last to be at least 5 MiB).
+	defaultMultipartPartSize = 8 * 1024 * 1024 // 8 MiB
+
+	// maxMultipartParts is the maximum number of parts S3 permits for a single
+	// multipart upload.
+	maxMultipartParts = 10000
+)
+
 // PutObject is called when putting objects into an s3 bucket.
 func (p *StoragePlugin) PutObject(ctx context.Context, req *pb.PutObjectRequest) (*pb.PutObjectResponse, error) {
 	if req == nil {
@@ -751,6 +768,32 @@ func (p *StoragePlugin) PutObject(ctx context.Context, req *pb.PutObjectRequest)
 	}
 	objectKey := path.Join(bucket.GetBucketPrefix(), req.GetKey())
 
+	// decodedChecksum is the raw SHA-256 digest of the entire object. Boundary
+	// compares this byte-for-byte against the hash it computed locally before
+	// the upload, so it must always be the whole-object checksum regardless of
+	// whether a single PutObject or a multipart upload is used.
+	decodedChecksum, err := base64.StdEncoding.DecodeString(checksum)
+	if err != nil {
+		return nil, errors.UnknownStatus("failed to decode checksum value")
+	}
+
+	// for larger files, use a multipart upload instead of a single PutObject
+	// request.
+	if info.Size() > multipartThreshold {
+		partSize := int64(defaultMultipartPartSize)
+		// S3 allows at most maxMultipartParts parts per upload, so grow the
+		// part size for very large objects to stay within that limit.
+		if sz := info.Size(); sz/partSize >= maxMultipartParts {
+			partSize = (sz + maxMultipartParts - 1) / maxMultipartParts
+		}
+		if err := p.putObjectMultipart(ctx, req, storageState, bucket.GetBucketName(), objectKey, file, partSize, opts...); err != nil {
+			return nil, err
+		}
+		return &pb.PutObjectResponse{
+			ChecksumSha_256: decodedChecksum,
+		}, nil
+	}
+
 	putCall := func(s3Client S3API) (any, error) {
 		return s3Client.PutObject(ctx, &s3.PutObjectInput{
 			Bucket:            aws.String(bucket.GetBucketName()),
@@ -772,15 +815,126 @@ func (p *StoragePlugin) PutObject(ctx context.Context, req *pb.PutObjectRequest)
 	if checksum != *resp.ChecksumSHA256 {
 		return nil, checksumMistmatchStatus()
 	}
-	decodedChecksum, err := base64.StdEncoding.DecodeString(*resp.ChecksumSHA256)
-	if err != nil {
-		return nil, errors.UnknownStatus("failed to decode checksum value from aws")
-	}
 	return &pb.PutObjectResponse{
 		ChecksumSha_256: decodedChecksum,
 	}, nil
 }
 
+// putObjectMultipart uploads file to the given bucket and key using an S3
+// multipart upload. The file is split into parts of partSize bytes (the final
+// part may be smaller) and each part is uploaded with its own SHA-256 checksum
+// so S3 can verify part integrity on the wire.
+//
+// If any step fails the upload is aborted on a best-effort basis to avoid
+// leaving orphaned parts behind, which would otherwise continue to accrue
+// storage charges.
+func (p *StoragePlugin) putObjectMultipart(
+	ctx context.Context,
+	req *pb.PutObjectRequest,
+	storageState *awsStoragePersistedState,
+	bucketName, objectKey string,
+	file *os.File,
+	partSize int64,
+	opts ...s3Option,
+) error {
+	bucketId := req.GetBucket().GetId()
+
+	createCall := func(s3Client S3API) (any, error) {
+		return s3Client.CreateMultipartUpload(ctx, &s3.CreateMultipartUploadInput{
+			Bucket:            aws.String(bucketName),
+			Key:               aws.String(objectKey),
+			ChecksumAlgorithm: types.ChecksumAlgorithmSha256,
+		})
+	}
+	createResp, err := p.call(ctx, createCall, bucketId, storageState, opts...)
+	if err != nil {
+		return parseS3Error("create multipart upload", err, req).Err()
+	}
+	uploadId := createResp.(*s3.CreateMultipartUploadOutput).UploadId
+
+	// once the upload has been created, any subsequent failure must abort it so
+	// uploaded parts are not orphaned.
+	abort := func() {
+		abortCall := func(s3Client S3API) (any, error) {
+			return s3Client.AbortMultipartUpload(ctx, &s3.AbortMultipartUploadInput{
+				Bucket:   aws.String(bucketName),
+				Key:      aws.String(objectKey),
+				UploadId: uploadId,
+			})
+		}
+		// best effort: the failure that triggered the abort is more useful to
+		// the caller than an error from the abort itself.
+		_, _ = p.call(ctx, abortCall, bucketId, storageState, opts...)
+	}
+
+	var completedParts []types.CompletedPart
+	buf := make([]byte, partSize)
+	var partNumber int32 = 1
+	for {
+		n, readErr := io.ReadFull(file, buf)
+		if readErr == io.EOF {
+			// previous iteration consumed the final bytes of the file
+			break
+		}
+		if readErr != nil && readErr != io.ErrUnexpectedEOF {
+			abort()
+			return errors.UnknownStatusf("failed to read file: %s", readErr)
+		}
+
+		partData := buf[:n]
+		sum := sha256.Sum256(partData)
+		partChecksum := base64.StdEncoding.EncodeToString(sum[:])
+
+		pn := partNumber
+		uploadCall := func(s3Client S3API) (any, error) {
+			return s3Client.UploadPart(ctx, &s3.UploadPartInput{
+				Bucket:            aws.String(bucketName),
+				Key:               aws.String(objectKey),
+				UploadId:          uploadId,
+				PartNumber:        aws.Int32(pn),
+				Body:              bytes.NewReader(partData),
+				ContentLength:     aws.Int64(int64(n)),
+				ChecksumAlgorithm: types.ChecksumAlgorithmSha256,
+				ChecksumSHA256:    aws.String(partChecksum),
+			})
+		}
+		uploadResp, err := p.call(ctx, uploadCall, bucketId, storageState, opts...)
+		if err != nil {
+			abort()
+			return parseS3Error("upload part", err, req).Err()
+		}
+		part := uploadResp.(*s3.UploadPartOutput)
+		completedParts = append(completedParts, types.CompletedPart{
+			ETag:           part.ETag,
+			ChecksumSHA256: part.ChecksumSHA256,
+			PartNumber:     aws.Int32(pn),
+		})
+
+		partNumber++
+		if readErr == io.ErrUnexpectedEOF {
+			// the final, short part
+			break
+		}
+	}
+
+	completeCall := func(s3Client S3API) (any, error) {
+		return s3Client.CompleteMultipartUpload(ctx, &s3.CompleteMultipartUploadInput{
+			Bucket:   aws.String(bucketName),
+			Key:      aws.String(objectKey),
+			UploadId: uploadId,
+			MultipartUpload: &types.CompletedMultipartUpload{
+				Parts: completedParts,
+			},
+		})
+	}
+	if _, err := p.call(ctx, completeCall, bucketId, storageState, opts...); err != nil {
+		abort()
+		return parseS3Error("complete multipart upload", err, req).Err()
+	}
+
+	return nil
+}
+
 // DeleteObjects is used to delete one or many objects from an s3 bucket.
 func (p *StoragePlugin) DeleteObjects(ctx context.Context, req *pb.DeleteObjectsRequest) (*pb.DeleteObjectsResponse, error) {
 	if req.GetKeyPrefix() == "" {

plugin/service/storage/plugin_test.go

@@ -3715,6 +3715,195 @@ func TestStoragePlugin_PutObject(t *testing.T) {
 	}
 }
 
+func TestStoragePlugin_PutObjectMultipart(t *testing.T) {
+	td := t.TempDir()
+
+	// genFile writes size bytes of deterministic content to a temp file and
+	// returns its path along with the raw SHA-256 digest of the whole file.
+	genFile := func(t *testing.T, name string, size int) (string, []byte) {
+		t.Helper()
+		data := make([]byte, size)
+		for i := range data {
+			data[i] = byte(i % 251)
+		}
+		fp := path.Join(td, name)
+		require.NoError(t, os.WriteFile(fp, data, 0o600))
+		sum := sha256.Sum256(data)
+		return fp, sum[:]
+	}
+
+	validRequest := func(p string) *pb.PutObjectRequest {
+		return &pb.PutObjectRequest{
+			Bucket: &storagebuckets.StorageBucket{
+				BucketName:   "external-obj-store",
+				BucketPrefix: "prefix",
+				Secrets:      credential.MockStaticCredentialSecrets(),
+				Attributes: &structpb.Struct{
+					Fields: map[string]*structpb.Value{
+						credential.ConstRegion: structpb.NewStringValue("us-west-2"),
+					},
+				},
+			},
+			Key:  "mock-object",
+			Path: p,
+		}
+	}
+
+	t.Run("multipart success spanning multiple parts", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		// 20 MiB with 8 MiB parts -> 3 parts (8, 8, 4 MiB).
+		fp, wholeChecksum := genFile(t, "large-file", 20*1024*1024)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(state)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.NoError(err)
+		require.NotNil(resp)
+
+		// Boundary must receive the whole-object SHA-256, not the multipart
+		// composite checksum.
+		assert.True(bytes.Equal(wholeChecksum, resp.GetChecksumSha_256()))
+
+		// The single-shot PutObject path must not have been used.
+		assert.False(state.PutObjectCalled)
+		assert.True(state.CreateMultipartUploadCalled)
+		assert.Equal(3, state.UploadPartCallCount)
+		assert.True(state.CompleteMultipartUploadCalled)
+		assert.False(state.AbortMultipartUploadCalled)
+
+		// The reassembled part bodies must equal the original file content.
+		orig, err := os.ReadFile(fp)
+		require.NoError(err)
+		assert.True(bytes.Equal(orig, state.UploadPartBody))
+
+		// The object key must include the configured bucket prefix.
+		require.NotNil(state.CreateMultipartUploadInputParams)
+		assert.Equal("prefix/mock-object", aws.ToString(state.CreateMultipartUploadInputParams.Key))
+	})
+
+	t.Run("file just above threshold uses two parts", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		// 8 MiB + 1 byte -> 2 parts (8 MiB, 1 byte).
+		fp, wholeChecksum := genFile(t, "just-over", 8*1024*1024+1)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(state)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.NoError(err)
+		assert.True(bytes.Equal(wholeChecksum, resp.GetChecksumSha_256()))
+		assert.Equal(2, state.UploadPartCallCount)
+		assert.True(state.CompleteMultipartUploadCalled)
+	})
+
+	t.Run("file at threshold uses single PutObject", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		// Exactly 8 MiB is not above the threshold, so the single-shot path is used.
+		fp, wholeChecksum := genFile(t, "at-threshold", 8*1024*1024)
+		checksum := base64.StdEncoding.EncodeToString(wholeChecksum)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(
+					state,
+					testMockS3WithPutObjectOutput(&s3.PutObjectOutput{
+						ChecksumSHA256: aws.String(checksum),
+					}),
+				)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.NoError(err)
+		assert.True(bytes.Equal(wholeChecksum, resp.GetChecksumSha_256()))
+		assert.True(state.PutObjectCalled)
+		assert.False(state.CreateMultipartUploadCalled)
+	})
+
+	t.Run("create multipart upload error", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		fp, _ := genFile(t, "create-err", 20*1024*1024)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(
+					state,
+					testMockS3WithCreateMultipartUploadError(TestAwsS3Error("AccessDenied", "CreateMultipartUpload", "not authorized")),
+				)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.Error(err)
+		assert.Nil(resp)
+		assert.Equal(codes.PermissionDenied, status.Code(err))
+		// Nothing was created, so nothing should be aborted.
+		assert.False(state.AbortMultipartUploadCalled)
+	})
+
+	t.Run("upload part error aborts upload", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		fp, _ := genFile(t, "upload-err", 20*1024*1024)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(
+					state,
+					testMockS3WithUploadPartErrorOnPart(2, TestAwsS3Error("AccessDenied", "UploadPart", "not authorized")),
+				)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.Error(err)
+		assert.Nil(resp)
+		assert.Equal(codes.PermissionDenied, status.Code(err))
+		assert.True(state.CreateMultipartUploadCalled)
+		assert.False(state.CompleteMultipartUploadCalled)
+		// The failed upload must be aborted to avoid orphaned parts.
+		assert.True(state.AbortMultipartUploadCalled)
+	})
+
+	t.Run("complete multipart upload error aborts upload", func(t *testing.T) {
+		require, assert := require.New(t), assert.New(t)
+		fp, _ := genFile(t, "complete-err", 20*1024*1024)
+
+		state := &testMockS3State{}
+		p := &StoragePlugin{
+			testCredStateOpts: validSTSMock(),
+			testStorageStateOpts: []awsStoragePersistedStateOption{
+				withTestS3APIFunc(newTestMockS3(
+					state,
+					testMockS3WithCompleteMultipartUploadError(TestAwsS3Error("InternalError", "CompleteMultipartUpload", "boom")),
+				)),
+			},
+		}
+
+		resp, err := p.PutObject(context.Background(), validRequest(fp))
+		require.Error(err)
+		assert.Nil(resp)
+		assert.Equal(3, state.UploadPartCallCount)
+		assert.True(state.AbortMultipartUploadCalled)
+	})
+}
+
 func TestStoragePlugin_DeleteObjects(t *testing.T) {
 	validRequest := func() *pb.DeleteObjectsRequest {
 		return &pb.DeleteObjectsRequest{

plugin/service/storage/state.go

@@ -26,6 +26,10 @@ type S3API interface {
 	GetObject(ctx context.Context, params *s3.GetObjectInput, optFns ...func(*s3.Options)) (*s3.GetObjectOutput, error)
 	HeadObject(ctx context.Context, params *s3.HeadObjectInput, optFns ...func(*s3.Options)) (*s3.HeadObjectOutput, error)
 	PutObject(ctx context.Context, params *s3.PutObjectInput, optFns ...func(*s3.Options)) (*s3.PutObjectOutput, error)
+	CreateMultipartUpload(ctx context.Context, params *s3.CreateMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.CreateMultipartUploadOutput, error)
+	UploadPart(ctx context.Context, params *s3.UploadPartInput, optFns ...func(*s3.Options)) (*s3.UploadPartOutput, error)
+	CompleteMultipartUpload(ctx context.Context, params *s3.CompleteMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.CompleteMultipartUploadOutput, error)
+	AbortMultipartUpload(ctx context.Context, params *s3.AbortMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.AbortMultipartUploadOutput, error)
 	DeleteObjects(ctx context.Context, params *s3.DeleteObjectsInput, optFns ...func(*s3.Options)) (*s3.DeleteObjectsOutput, error)
 	ListObjectsV2(ctx context.Context, params *s3.ListObjectsV2Input, optFns ...func(*s3.Options)) (*s3.ListObjectsV2Output, error)
 	Credentials() aws.Credentials

plugin/service/storage/testing.go

@@ -6,6 +6,8 @@ package storage
 import (
 	"bytes"
 	"context"
+	"crypto/sha256"
+	"encoding/base64"
 	"fmt"
 	"io"
 	"testing"
@@ -39,6 +41,23 @@ type testMockS3State struct {
 	PutObjectInputParams *s3.PutObjectInput
 	PutObjectBody        []byte
 
+	CreateMultipartUploadCalled      bool
+	CreateMultipartUploadInputParams *s3.CreateMultipartUploadInput
+
+	UploadPartCalled      bool
+	UploadPartCallCount   int
+	UploadPartInputParams []*s3.UploadPartInput
+	// UploadPartBody is the concatenation, in part-number order, of every
+	// part body received by UploadPart. It can be compared against the full
+	// object that was expected to be uploaded.
+	UploadPartBody []byte
+
+	CompleteMultipartUploadCalled      bool
+	CompleteMultipartUploadInputParams *s3.CompleteMultipartUploadInput
+
+	AbortMultipartUploadCalled      bool
+	AbortMultipartUploadInputParams *s3.AbortMultipartUploadInput
+
 	HeadObjectCalled      bool
 	HeadObjectInputParams *s3.HeadObjectInput
 
@@ -57,6 +76,16 @@ func (s *testMockS3State) Reset() {
 	s.PutObjectCalled = false
 	s.PutObjectInputParams = nil
 	s.PutObjectBody = nil
+	s.CreateMultipartUploadCalled = false
+	s.CreateMultipartUploadInputParams = nil
+	s.UploadPartCalled = false
+	s.UploadPartCallCount = 0
+	s.UploadPartInputParams = nil
+	s.UploadPartBody = nil
+	s.CompleteMultipartUploadCalled = false
+	s.CompleteMultipartUploadInputParams = nil
+	s.AbortMultipartUploadCalled = false
+	s.AbortMultipartUploadInputParams = nil
 	s.HeadObjectCalled = false
 	s.HeadObjectInputParams = nil
 	s.ListObjectsV2Called = false
@@ -81,6 +110,19 @@ type testMockS3 struct {
 	PutObjectOutput *s3.PutObjectOutput
 	PutObjectErr    error
 
+	// mocked responses for the multipart upload calls
+	CreateMultipartUploadOutput *s3.CreateMultipartUploadOutput
+	CreateMultipartUploadErr    error
+	UploadPartOutput            *s3.UploadPartOutput
+	UploadPartErr               error
+	// UploadPartErrOnPart, when greater than zero, causes UploadPart to return
+	// UploadPartErr (or a generic error) only for the matching part number.
+	UploadPartErrOnPart           int32
+	CompleteMultipartUploadOutput *s3.CompleteMultipartUploadOutput
+	CompleteMultipartUploadErr    error
+	AbortMultipartUploadOutput    *s3.AbortMultipartUploadOutput
+	AbortMultipartUploadErr       error
+
 	// mocked responses for headObject
 	HeadObjectOutput *s3.HeadObjectOutput
 	HeadObjectErr    error
@@ -114,6 +156,63 @@ func testMockS3WithPutObjectError(e error) testMockS3Option {
 	}
 }
 
+func testMockS3WithCreateMultipartUploadOutput(o *s3.CreateMultipartUploadOutput) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.CreateMultipartUploadOutput = o
+		return nil
+	}
+}
+
+func testMockS3WithCreateMultipartUploadError(e error) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.CreateMultipartUploadErr = e
+		return nil
+	}
+}
+
+func testMockS3WithUploadPartOutput(o *s3.UploadPartOutput) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.UploadPartOutput = o
+		return nil
+	}
+}
+
+func testMockS3WithUploadPartError(e error) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.UploadPartErr = e
+		return nil
+	}
+}
+
+func testMockS3WithUploadPartErrorOnPart(partNumber int32, e error) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.UploadPartErr = e
+		m.UploadPartErrOnPart = partNumber
+		return nil
+	}
+}
+
+func testMockS3WithCompleteMultipartUploadOutput(o *s3.CompleteMultipartUploadOutput) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.CompleteMultipartUploadOutput = o
+		return nil
+	}
+}
+
+func testMockS3WithCompleteMultipartUploadError(e error) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.CompleteMultipartUploadErr = e
+		return nil
+	}
+}
+
+func testMockS3WithAbortMultipartUploadError(e error) testMockS3Option {
+	return func(m *testMockS3) error {
+		m.AbortMultipartUploadErr = e
+		return nil
+	}
+}
+
 func testMockS3WithGetObjectOutput(o *s3.GetObjectOutput) testMockS3Option {
 	return func(m *testMockS3) error {
 		m.GetObjectOutput = o
@@ -255,6 +354,95 @@ func (m *testMockS3) PutObject(ctx context.Context, params *s3.PutObjectInput, o
 	return m.PutObjectOutput, nil
 }
 
+func (m *testMockS3) CreateMultipartUpload(ctx context.Context, params *s3.CreateMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.CreateMultipartUploadOutput, error) {
+	if m.State != nil {
+		m.State.CreateMultipartUploadCalled = true
+		m.State.CreateMultipartUploadInputParams = params
+	}
+
+	if m.CreateMultipartUploadErr != nil {
+		return nil, m.CreateMultipartUploadErr
+	}
+
+	if m.CreateMultipartUploadOutput != nil {
+		return m.CreateMultipartUploadOutput, nil
+	}
+	return &s3.CreateMultipartUploadOutput{
+		UploadId: aws.String("test-upload-id"),
+	}, nil
+}
+
+func (m *testMockS3) UploadPart(ctx context.Context, params *s3.UploadPartInput, optFns ...func(*s3.Options)) (*s3.UploadPartOutput, error) {
+	if m.State != nil {
+		m.State.UploadPartCalled = true
+		m.State.UploadPartCallCount++
+		m.State.UploadPartInputParams = append(m.State.UploadPartInputParams, params)
+	}
+
+	// always drain the body so the part data can be asserted on and so the
+	// reader is not left dangling.
+	var data []byte
+	if params.Body != nil {
+		var err error
+		data, err = io.ReadAll(params.Body)
+		if err != nil {
+			return nil, err
+		}
+		if m.State != nil {
+			m.State.UploadPartBody = append(m.State.UploadPartBody, data...)
+		}
+	}
+
+	if m.UploadPartErr != nil {
+		if m.UploadPartErrOnPart == 0 || (params.PartNumber != nil && *params.PartNumber == m.UploadPartErrOnPart) {
+			return nil, m.UploadPartErr
+		}
+	}
+
+	if m.UploadPartOutput != nil {
+		return m.UploadPartOutput, nil
+	}
+	// echo the supplied part checksum so CompleteMultipartUpload can be built
+	// the way the real service would allow.
+	sum := sha256.Sum256(data)
+	return &s3.UploadPartOutput{
+		ETag:           aws.String(fmt.Sprintf("etag-%d", aws.ToInt32(params.PartNumber))),
+		ChecksumSHA256: aws.String(base64.StdEncoding.EncodeToString(sum[:])),
+	}, nil
+}
+
+func (m *testMockS3) CompleteMultipartUpload(ctx context.Context, params *s3.CompleteMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.CompleteMultipartUploadOutput, error) {
+	if m.State != nil {
+		m.State.CompleteMultipartUploadCalled = true
+		m.State.CompleteMultipartUploadInputParams = params
+	}
+
+	if m.CompleteMultipartUploadErr != nil {
+		return nil, m.CompleteMultipartUploadErr
+	}
+
+	if m.CompleteMultipartUploadOutput != nil {
+		return m.CompleteMultipartUploadOutput, nil
+	}
+	return &s3.CompleteMultipartUploadOutput{}, nil
+}
+
+func (m *testMockS3) AbortMultipartUpload(ctx context.Context, params *s3.AbortMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.AbortMultipartUploadOutput, error) {
+	if m.State != nil {
+		m.State.AbortMultipartUploadCalled = true
+		m.State.AbortMultipartUploadInputParams = params
+	}
+
+	if m.AbortMultipartUploadErr != nil {
+		return nil, m.AbortMultipartUploadErr
+	}
+
+	if m.AbortMultipartUploadOutput != nil {
+		return m.AbortMultipartUploadOutput, nil
+	}
+	return &s3.AbortMultipartUploadOutput{}, nil
+}
+
 func (m *testMockS3) ListObjectsV2(ctx context.Context, params *s3.ListObjectsV2Input, optFns ...func(*s3.Options)) (*s3.ListObjectsV2Output, error) {
 	if m.State != nil {
 		m.State.ListObjectsV2Called = true