Tighten opaque plugin content boundaries

platform/service/distribution_build_execution_test.go

@@ -1,9 +1,12 @@
 package service
 
 import (
+	"bytes"
 	"encoding/base64"
 	"encoding/json"
 	"errors"
+	"os"
+	"path/filepath"
 	"strings"
 	"sync"
 	"testing"
@@ -11,6 +14,7 @@ import (
 
 	"browser.local/platform/domain"
 	"browser.local/platform/repo"
+	"browser.local/platform/validator"
 )
 
 type captureDistributionBuilder struct {
@@ -25,6 +29,11 @@ type progressDistributionBuilder struct {
 	payload []byte
 }
 
+type fileDistributionBuilder struct {
+	inputs     chan domain.DistributionBuildInput
+	outputPath string
+}
+
 func (builder captureDistributionBuilder) Readiness() (bool, string) {
 	return true, ""
 }
@@ -58,6 +67,28 @@ func (builder progressDistributionBuilder) BuildWithProgress(_ domain.Distributi
 	return domain.CopyBytes(builder.payload), nil
 }
 
+func (builder fileDistributionBuilder) Readiness() (bool, string) {
+	return true, ""
+}
+
+func (builder fileDistributionBuilder) Build(domain.DistributionBuildInput) ([]byte, error) {
+	return nil, errors.New("byte build path should not be used for file output builders")
+}
+
+func (builder fileDistributionBuilder) BuildFile(input domain.DistributionBuildInput, progress func(DistributionBuildProgress)) (DistributionBuildOutput, error) {
+	if progress != nil {
+		progress(DistributionBuildProgress{Percent: 88, Message: "package_finalize: output file ready"})
+	}
+	if builder.inputs != nil {
+		builder.inputs <- input
+	}
+	sizeBytes, checksum, err := fileSizeAndChecksum(builder.outputPath)
+	if err != nil {
+		return DistributionBuildOutput{}, err
+	}
+	return DistributionBuildOutput{Path: builder.outputPath, SizeBytes: sizeBytes, Checksum: checksum}, nil
+}
+
 func TestCoreServiceKeepsPlatformBuildKeyOffMachineJobChannel(t *testing.T) {
 	svc, session, instance := newDistributionTestFixture(t)
 	plugin, err := svc.store.GamePlugins().Get(instance.PluginID)
@@ -393,6 +424,47 @@ func TestCoreServiceProjectsPlatformBuilderProgressBeforeCompletion(t *testing.T
 	completeDistributionBuild(t, svc, distribution, nil)
 }
 
+func TestCoreServiceStoresPlatformBuildFileOutput(t *testing.T) {
+	svc, session, instance := newDistributionTestFixture(t)
+	outputPath := filepath.Join(t.TempDir(), "run")
+	payload := bytes.Repeat([]byte("platform-build-file-output"), 8192)
+	if err := os.WriteFile(outputPath, payload, 0o600); err != nil {
+		t.Fatalf("write builder file output: %v", err)
+	}
+	inputs := make(chan domain.DistributionBuildInput, 1)
+	svc.ConfigureDistributionBuilder(fileDistributionBuilder{inputs: inputs, outputPath: outputPath})
+
+	distribution, err := svc.GenerateRunDistributionForSession(session, domain.RunDistributionGenerateRequest{
+		ServerInstanceID: instance.ID,
+		TargetOS:         "linux",
+		TargetArch:       "amd64",
+		IdempotencyKey:   "platform-builder-file-output",
+	})
+	if err != nil {
+		t.Fatalf("generate platform distribution: %v", err)
+	}
+	select {
+	case <-inputs:
+	case <-time.After(time.Second):
+		t.Fatal("platform file builder did not receive internal build input")
+	}
+	distribution = completeDistributionBuild(t, svc, distribution, nil)
+	artifact, err := svc.GetArtifact(distribution.ArtifactID)
+	if err != nil {
+		t.Fatalf("get distribution artifact: %v", err)
+	}
+	if artifact.SizeBytes != int64(len(payload)) || artifact.Checksum != validator.BytesChecksum(payload) {
+		t.Fatalf("artifact metadata did not come from file output: %+v", artifact)
+	}
+	stored, err := svc.artifactStore.GetPayload(distribution.ArtifactID)
+	if err != nil {
+		t.Fatalf("get stored distribution payload: %v", err)
+	}
+	if !bytes.Equal(stored, payload) {
+		t.Fatalf("stored distribution payload changed during file-backed recording")
+	}
+}
+
 func TestCoreServiceDiscardsBuildCompletedAfterKeyReset(t *testing.T) {
 	svc, session, instance := newDistributionTestFixture(t)
 	inputs := make(chan domain.DistributionBuildInput, 1)