feat: edge gateway service

gateway/internal/grpcapi/payload_hash.go

@@ -0,0 +1,66 @@
+package grpcapi
+
+import (
+	"context"
+	"errors"
+
+	"galaxy/gateway/internal/authn"
+	gatewayv1 "galaxy/gateway/proto/galaxy/gateway/v1"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// payloadHashVerifyingService applies payload-hash verification after session
+// lookup and before any later auth or routing step runs.
+type payloadHashVerifyingService struct {
+	gatewayv1.UnimplementedEdgeGatewayServer
+
+	delegate gatewayv1.EdgeGatewayServer
+}
+
+// ExecuteCommand verifies req payload integrity before delegating to the
+// configured service implementation.
+func (s payloadHashVerifyingService) ExecuteCommand(ctx context.Context, req *gatewayv1.ExecuteCommandRequest) (*gatewayv1.ExecuteCommandResponse, error) {
+	if err := verifyPayloadHash(ctx); err != nil {
+		return nil, err
+	}
+
+	return s.delegate.ExecuteCommand(ctx, req)
+}
+
+// SubscribeEvents verifies req payload integrity before delegating to the
+// configured service implementation.
+func (s payloadHashVerifyingService) SubscribeEvents(req *gatewayv1.SubscribeEventsRequest, stream grpc.ServerStreamingServer[gatewayv1.GatewayEvent]) error {
+	if err := verifyPayloadHash(stream.Context()); err != nil {
+		return err
+	}
+
+	return s.delegate.SubscribeEvents(req, stream)
+}
+
+// newPayloadHashVerifyingService wraps delegate with the payload-hash
+// verification gate.
+func newPayloadHashVerifyingService(delegate gatewayv1.EdgeGatewayServer) gatewayv1.EdgeGatewayServer {
+	return payloadHashVerifyingService{delegate: delegate}
+}
+
+func verifyPayloadHash(ctx context.Context) error {
+	envelope, ok := parsedEnvelopeFromContext(ctx)
+	if !ok {
+		return status.Error(codes.Internal, "authenticated request context is incomplete")
+	}
+
+	err := authn.VerifyPayloadHash(envelope.PayloadBytes, envelope.PayloadHash)
+	switch {
+	case err == nil:
+		return nil
+	case errors.Is(err, authn.ErrInvalidPayloadHash), errors.Is(err, authn.ErrPayloadHashMismatch):
+		return status.Error(codes.InvalidArgument, err.Error())
+	default:
+		return status.Error(codes.Internal, "payload hash verification failed")
+	}
+}
+
+var _ gatewayv1.EdgeGatewayServer = payloadHashVerifyingService{}