feat: wallet private key export API with password verification

internal/auth/service.go

@@ -535,6 +535,18 @@ func sanitizeForUsername(s string) string {
 // If these fail, the admin user exists without a wallet/profile.
 // This is acceptable because EnsureAdmin runs once at startup and failures
 // are logged as warnings. A restart will skip user creation (already exists).
+// VerifyPassword checks if the password matches the user's stored hash.
+func (s *Service) VerifyPassword(userID uint, password string) error {
+	user, err := s.repo.FindByID(userID)
+	if err != nil {
+		return fmt.Errorf("user not found")
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(password)); err != nil {
+		return fmt.Errorf("invalid password")
+	}
+	return nil
+}
+
 func (s *Service) EnsureAdmin(username, password string) error {
 	if _, err := s.repo.FindByUsername(username); err == nil {
 		return nil

internal/chain/handler.go

@@ -3,6 +3,7 @@ package chain
 import (
 	"errors"
 	"log"
+	"log/slog"
 	"strconv"
 	"strings"
 
@@ -620,6 +621,39 @@ func (h *Handler) RegisterTemplate(c *fiber.Ctx) error {
 	return c.Status(fiber.StatusCreated).JSON(result)
 }
 
+// ExportWallet godoc
+// @Summary      개인키 내보내기
+// @Description  비밀번호 확인 후 현재 유저의 지갑 개인키를 반환합니다
+// @Tags         Chain
+// @Accept       json
+// @Produce      json
+// @Security     BearerAuth
+// @Param        body  body  exportRequest  true  "비밀번호"
+// @Success      200  {object}  map[string]string
+// @Failure      400  {object}  docs.ErrorResponse
+// @Failure      401  {object}  docs.ErrorResponse
+// @Router       /api/chain/wallet/export [post]
+type exportRequest struct {
+	Password string `json:"password"`
+}
+
+func (h *Handler) ExportWallet(c *fiber.Ctx) error {
+	userID, err := getUserID(c)
+	if err != nil {
+		return err
+	}
+	var req exportRequest
+	if err := c.BodyParser(&req); err != nil || req.Password == "" {
+		return c.Status(400).JSON(fiber.Map{"error": "password is required"})
+	}
+	slog.Warn("wallet export requested", "userID", userID, "ip", c.IP())
+	privKeyHex, err := h.svc.ExportPrivKey(userID, req.Password)
+	if err != nil {
+		return c.Status(401).JSON(fiber.Map{"error": "invalid password"})
+	}
+	return c.JSON(fiber.Map{"privateKey": privKeyHex})
+}
+
 // ---- Internal Handlers (game server, username-based) ----
 
 // InternalGrantReward godoc

internal/chain/service.go

@@ -21,14 +21,15 @@ import (
 )
 
 type Service struct {
-	repo           *Repository
-	client         *Client
-	chainID        string
-	operatorWallet *wallet.Wallet
-	encKeyBytes    []byte // 32-byte AES-256 key
-	userResolver   func(username string) (uint, error)
-	operatorMu     sync.Mutex // serialises operator-nonce transactions
-	userMu         sync.Map   // per-user mutex (keyed by userID uint)
+	repo             *Repository
+	client           *Client
+	chainID          string
+	operatorWallet   *wallet.Wallet
+	encKeyBytes      []byte // 32-byte AES-256 key
+	userResolver     func(username string) (uint, error)
+	passwordVerifier func(userID uint, password string) error
+	operatorMu       sync.Mutex // serialises operator-nonce transactions
+	userMu           sync.Map   // per-user mutex (keyed by userID uint)
 }
 
 // SetUserResolver sets the callback that resolves username → userID.
@@ -36,6 +37,24 @@ func (s *Service) SetUserResolver(fn func(username string) (uint, error)) {
 	s.userResolver = fn
 }
 
+func (s *Service) SetPasswordVerifier(fn func(userID uint, password string) error) {
+	s.passwordVerifier = fn
+}
+
+func (s *Service) ExportPrivKey(userID uint, password string) (string, error) {
+	if s.passwordVerifier == nil {
+		return "", fmt.Errorf("password verifier not configured")
+	}
+	if err := s.passwordVerifier(userID, password); err != nil {
+		return "", err
+	}
+	w, _, err := s.loadUserWallet(userID)
+	if err != nil {
+		return "", err
+	}
+	return w.PrivKey().Hex(), nil
+}
+
 // resolveUsername converts a username to the user's on-chain pubKeyHex.
 // If the user exists but has no wallet (e.g. legacy user or failed creation),
 // a wallet is auto-created on the fly.

main.go

@@ -93,6 +93,7 @@ func main() {
 		_, err := chainSvc.CreateWallet(userID)
 		return err
 	})
+	chainSvc.SetPasswordVerifier(authSvc.VerifyPassword)
 
 	playerRepo := player.NewRepository(db)
 	playerSvc := player.NewService(playerRepo)

routes/routes.go

@@ -113,6 +113,7 @@ func Register(
 	// Chain - Queries (authenticated)
 	ch := api.Group("/chain", authMw)
 	ch.Get("/wallet", chainH.GetWalletInfo)
+	ch.Post("/wallet/export", chainH.ExportWallet)
 	ch.Get("/balance", chainH.GetBalance)
 	ch.Get("/assets", chainH.GetAssets)
 	ch.Get("/asset/:id", chainH.GetAsset)