From c08135309f803585d902b352d2e865bdd718afd7 Mon Sep 17 00:00:00 2001
From: Alexey <alex@oblat.lv>
Date: Wed, 6 Aug 2025 15:41:25 +0300
Subject: [PATCH] add random salt and result/error checksum

---
 internal/server/gateway/route.go   |  8 +++---
 internal/server/rpc/definition.go  | 11 ++++++---
 internal/server/rpc/writers.go     | 39 ++++++++++++++++++++++++++----
 internal/server/sv1/lua_handler.go |  9 ++-----
 4 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/internal/server/gateway/route.go b/internal/server/gateway/route.go
index 18de8cc..b18d5cc 100644
--- a/internal/server/gateway/route.go
+++ b/internal/server/gateway/route.go
@@ -26,7 +26,7 @@ func (gs *GatewayServer) Handle(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("X-Session-UUID", sessionUUID)
 	if !gs.sm.Add(sessionUUID) {
 		gs.x.SLog.Debug("session is busy", slog.String("session-uuid", sessionUUID))
-		rpc.WriteError(w, &rpc.RPCResponse{
+		rpc.WriteError(gs.cs.UUID32, w, &rpc.RPCResponse{
 			Error: map[string]any{
 				"code":    rpc.ErrSessionIsBusy,
 				"message": rpc.ErrSessionIsBusyS,
@@ -40,7 +40,7 @@ func (gs *GatewayServer) Handle(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		gs.x.SLog.Debug("failed to read body", slog.String("err", err.Error()))
 		w.WriteHeader(http.StatusBadRequest)
-		rpc.WriteError(w, &rpc.RPCResponse{
+		rpc.WriteError(gs.cs.UUID32, w, &rpc.RPCResponse{
 			JSONRPC: rpc.JSONRPCVersion,
 			ID:      nil,
 			Error: map[string]any{
@@ -60,7 +60,7 @@ func (gs *GatewayServer) Handle(w http.ResponseWriter, r *http.Request) {
 		if err := json.Unmarshal(body, &single); err != nil {
 			gs.x.SLog.Debug("failed to parse json", slog.String("err", err.Error()))
 			w.WriteHeader(http.StatusBadRequest)
-			rpc.WriteError(w, &rpc.RPCResponse{
+			rpc.WriteError(gs.cs.UUID32, w, &rpc.RPCResponse{
 				JSONRPC: rpc.JSONRPCVersion,
 				ID:      nil,
 				Error: map[string]any{
@@ -76,7 +76,7 @@ func (gs *GatewayServer) Handle(w http.ResponseWriter, r *http.Request) {
 			w.Write([]byte(""))
 			return
 		}
-		rpc.WriteResponse(w, resp)
+		rpc.WriteResponse(gs.cs.UUID32, w, resp)
 		return
 	}
 
diff --git a/internal/server/rpc/definition.go b/internal/server/rpc/definition.go
index 68039f7..426c266 100644
--- a/internal/server/rpc/definition.go
+++ b/internal/server/rpc/definition.go
@@ -11,10 +11,13 @@ type RPCRequest struct {
 }
 
 type RPCResponse struct {
-	JSONRPC string           `json:"jsonrpc"`
-	ID      *json.RawMessage `json:"id"`
-	Result  any              `json:"result,omitempty"`
-	Error   any              `json:"error,omitempty"`
+	JSONRPC         string           `json:"jsonrpc"`
+	ID              *json.RawMessage `json:"id"`
+	Result          any              `json:"result,omitempty"`
+	Error           any              `json:"error,omitempty"`
+	ResponsibleNode string           `json:"responsible-node,omitempty"`
+	Salt            string           `json:"salt,omitempty"`
+	Checksum        string           `json:"checksum,omitempty"`
 }
 
 const (
diff --git a/internal/server/rpc/writers.go b/internal/server/rpc/writers.go
index aa1c519..e02bbd8 100644
--- a/internal/server/rpc/writers.go
+++ b/internal/server/rpc/writers.go
@@ -1,11 +1,40 @@
 package rpc
 
 import (
+	"crypto/md5"
 	"encoding/json"
+	"fmt"
 	"net/http"
+
+	"github.com/google/uuid"
 )
 
-func write(w http.ResponseWriter, msg *RPCResponse) error {
+func generateChecksum(result any) string {
+	if result == nil {
+		return ""
+	}
+	data, err := json.Marshal(result)
+	if err != nil {
+		return ""
+	}
+	return fmt.Sprintf("%x", md5.Sum(data))
+}
+
+func generateSalt() string {
+	return uuid.NewString()
+}
+
+func write(nid string, w http.ResponseWriter, msg *RPCResponse) error {
+	msg.Salt = generateSalt()
+	if msg.Result != nil {
+		msg.Checksum = generateChecksum(msg.Result)
+	} else {
+		msg.Checksum = generateChecksum(msg.Error)
+	}
+	
+	if nid != "" {
+		msg.ResponsibleNode = nid
+	}
 	data, err := json.Marshal(msg)
 	if err != nil {
 		return err
@@ -14,10 +43,10 @@ func write(w http.ResponseWriter, msg *RPCResponse) error {
 	return err
 }
 
-func WriteError(w http.ResponseWriter, errm *RPCResponse) error {
-	return write(w, errm)
+func WriteError(nid string, w http.ResponseWriter, errm *RPCResponse) error {
+	return write(nid, w, errm)
 }
 
-func WriteResponse(w http.ResponseWriter, response *RPCResponse) error {
-	return write(w, response)
+func WriteResponse(nid string, w http.ResponseWriter, response *RPCResponse) error {
+	return write(nid, w, response)
 }
diff --git a/internal/server/sv1/lua_handler.go b/internal/server/sv1/lua_handler.go
index 7837b66..c82c622 100644
--- a/internal/server/sv1/lua_handler.go
+++ b/internal/server/sv1/lua_handler.go
@@ -447,17 +447,13 @@ func (h *HandlerV1) handleLUA(sid string, r *http.Request, req *rpc.RPCRequest,
 	sessionVal := loadedTbl.RawGetString("internal.session")
 	sessionTbl, ok := sessionVal.(*lua.LTable)
 	if !ok {
-		return rpc.NewResponse(map[string]any{
-			"responsible-node": h.cs.UUID32,
-		}, req.ID)
+		return rpc.NewResponse(nil, req.ID)
 	}
 
 	tag := sessionTbl.RawGetString("__gosally_internal")
 	if tag.Type() != lua.LTString || tag.String() != fmt.Sprint(seed) {
 		llog.Debug("stock session module is not imported: wrong seed", slog.String("script", path))
-		return rpc.NewResponse(map[string]any{
-			"responsible-node": h.cs.UUID32,
-		}, req.ID)
+		return rpc.NewResponse(nil, req.ID)
 	}
 
 	outVal := sessionTbl.RawGetString("response")
@@ -500,6 +496,5 @@ func (h *HandlerV1) handleLUA(sid string, r *http.Request, req *rpc.RPCRequest,
 	} else {
 		payload["message"] = ConvertLuaTypesToGolang(resultVal)
 	}
-	payload["responsible-node"] = h.cs.UUID32
 	return rpc.NewResponse(payload, req.ID)
 }