fix(security): behebe F-01/F-02/W-03/W-04 aus Security-Audit + PROJ-24 TOTP 2FA

F-01: err.Error() wird nicht mehr an HTTP-Clients gesendet.
      Stattdessen generische Fehlermeldungen + Server-Log.
      Betrifft: handleCreateUser, handleUpdateUser, handleDeleteUser,
                handleSyncNow, handleSecurityConfig, handleUpload.

F-02: Login-Audit-Log enthält keinen rohen err.Error() mehr.
      Neue classifyLoginError() Funktion: invalid_password / ldap_error /
      account_disabled / unknown — schützt vor LDAP-Info-Leak via Audit-API.

W-03: remoteIP() trimmt jetzt Leerzeichen aus X-Forwarded-For.
      Vollständige Lösung erfordert Proxy-Konfiguration (W-03 bleibt WARN).

W-04: Attachment-Dateiname wird durch sanitizeFilename() bereinigt.
      Nur [a-zA-Z0-9._- ] erlaubt — verhindert Header-Injection.

PROJ-24: TOTP 2FA vollständig implementiert:
      - internal/auth/totp.go: GenerateSecret, ValidateTOTP, QRCodeSVG
      - internal/api/totp_handlers.go: Setup, Login-Step2, Admin-Reset
      - internal/userstore: SetTOTPSecret, EnableTOTP, DisableTOTP, ResetTOTP
      - Login-Flow: totp_pending JWT → /api/auth/totp → vollwertiger JWT
      - AES-256-GCM verschlüsseltes Secret in users.totp_secret

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/api_test.go

@@ -91,7 +91,7 @@ func newTestEnv(t *testing.T) *testEnv {
 	users.Create(userstore.CreateUserRequest{Username: "auditor", Email: "auditor@x.com", Password: "auditorpass", Role: userstore.RoleAuditor})
 	users.Create(userstore.CreateUserRequest{Username: "user1", Email: "user1@x.com", Password: "userpass", Role: userstore.RoleUser})
 
-	authMgr := auth.New(users, nil, "test-secret-must-be-long-enough-32")
+	authMgr := auth.New(users, nil, "test-secret-must-be-long-enough-32", "0000000000000000000000000000000000000000000000000000000000000000")
 	cfg := config.APIConfig{Bind: ":18080", Secret: "test-secret-must-be-long-enough-32"}
 	srv := api.New(cfg, store, idx, authMgr, users, audlog, logger)
 

internal/api/server.go

@@ -194,6 +194,13 @@ func (s *Server) routes() {
 	s.mux.HandleFunc("POST /api/pop3/test", s.auth(s.handleTestPop3))
 	s.mux.HandleFunc("POST /api/pop3/{id}/import", s.auth(s.handleStartPop3Import))
 	s.mux.HandleFunc("GET /api/pop3/{id}/progress", s.auth(s.handlePop3Progress))
+
+	// PROJ-24: TOTP 2FA routes
+	s.mux.HandleFunc("GET /api/auth/totp/setup", s.auth(s.handleTOTPSetupGet))
+	s.mux.HandleFunc("POST /api/auth/totp/setup", s.auth(s.handleTOTPSetupPost))
+	s.mux.HandleFunc("DELETE /api/auth/totp", s.auth(s.handleTOTPDisable))
+	s.mux.HandleFunc("POST /api/auth/totp", s.handleTOTPLogin) // no auth middleware — uses pending token
+	s.mux.HandleFunc("POST /api/admin/users/{id}/totp/reset", s.authAdmin(s.handleTOTPReset))
 }
 
 // ServeHTTP implements http.Handler.
@@ -236,7 +243,7 @@ func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	token, user, err := s.authMgr.Login(req.Username, req.Password)
+	token, user, totpRequired, err := s.authMgr.Login(req.Username, req.Password)
 	if err != nil {
 		_ = s.users.RecordLoginAttempt(req.Username, remoteIP(r))
 		s.audlog.Log(audit.Entry{
@@ -244,12 +251,28 @@ func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
 			Username:  req.Username,
 			IPAddress: remoteIP(r),
 			Success:   false,
-			Detail:    err.Error(),
+			Detail:    classifyLoginError(err),
 		})
 		writeError(w, http.StatusUnauthorized, "invalid credentials")
 		return
 	}
 
+	// PROJ-24: If TOTP is enabled, return a pending token instead of a full session.
+	if totpRequired {
+		s.audlog.Log(audit.Entry{
+			EventType: audit.EventLogin,
+			Username:  user.Username,
+			IPAddress: remoteIP(r),
+			Success:   true,
+			Detail:    "totp_pending",
+		})
+		writeJSON(w, http.StatusAccepted, map[string]interface{}{
+			"totp_required": true,
+			"session_token": token,
+		})
+		return
+	}
+
 	_ = s.users.UpdateLastLogin(user.ID)
 
 	s.audlog.Log(audit.Entry{
@@ -404,7 +427,8 @@ func (s *Server) handleCreateUser(w http.ResponseWriter, r *http.Request) {
 		TenantID: tenantID,
 	})
 	if err != nil {
-		writeError(w, http.StatusBadRequest, err.Error())
+		s.logger.Error("create user failed", "err", err)
+		writeError(w, http.StatusBadRequest, "user creation failed")
 		return
 	}
 
@@ -477,7 +501,8 @@ func (s *Server) handleUpdateUser(w http.ResponseWriter, r *http.Request) {
 		Password: req.Password,
 	})
 	if err != nil {
-		writeError(w, http.StatusBadRequest, err.Error())
+		s.logger.Error("update user failed", "err", err)
+		writeError(w, http.StatusBadRequest, "user update failed")
 		return
 	}
 
@@ -532,7 +557,8 @@ func (s *Server) handleDeleteUser(w http.ResponseWriter, r *http.Request) {
 			writeError(w, http.StatusConflict, "cannot delete the last active admin")
 			return
 		}
-		writeError(w, http.StatusInternalServerError, err.Error())
+		s.logger.Error("delete user failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "user deletion failed")
 		return
 	}
 
@@ -876,9 +902,45 @@ func tenantFromCtx(ctx context.Context) *int64 {
 	return v
 }
 
+// sanitizeFilename strips characters that could be used for HTTP header injection
+// (quotes, newlines, control chars) from attachment filenames coming from parsed
+// e-mails. Only alphanumerics, spaces, dots, hyphens, and underscores are kept.
+func sanitizeFilename(name string) string {
+	var b strings.Builder
+	for _, r := range name {
+		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') ||
+			r == '.' || r == '-' || r == '_' || r == ' ' {
+			b.WriteRune(r)
+		}
+	}
+	return b.String()
+}
+
+// classifyLoginError maps internal login errors to safe audit-log categories.
+// Raw error messages must not be stored in audit logs since auditor-role
+// users can read them via GET /api/audit and internal details (LDAP hostnames,
+// port numbers, etc.) would be exposed.
+func classifyLoginError(err error) string {
+	if err == nil {
+		return ""
+	}
+	msg := err.Error()
+	switch {
+	case strings.Contains(msg, "not found"), strings.Contains(msg, "invalid password"),
+		strings.Contains(msg, "invalid credentials"):
+		return "invalid_password"
+	case strings.Contains(msg, "ldap"), strings.Contains(msg, "LDAP"):
+		return "ldap_error"
+	case strings.Contains(msg, "disabled"), strings.Contains(msg, "inactive"):
+		return "account_disabled"
+	default:
+		return "unknown"
+	}
+}
+
 func remoteIP(r *http.Request) string {
 	if fwd := r.Header.Get("X-Forwarded-For"); fwd != "" {
-		return strings.Split(fwd, ",")[0]
+		return strings.TrimSpace(strings.Split(fwd, ",")[0])
 	}
 	return r.RemoteAddr
 }
@@ -1043,7 +1105,7 @@ func (s *Server) handleGetAttachment(w http.ResponseWriter, r *http.Request) {
 	}
 
 	a := pm.Attachments[idx]
-	filename := a.Filename
+	filename := sanitizeFilename(a.Filename)
 	if filename == "" {
 		filename = fmt.Sprintf("attachment-%d", idx)
 	}
@@ -1538,7 +1600,8 @@ func (s *Server) handleSyncNow(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := s.imapScheduler.TriggerSync(r.Context(), id); err != nil {
-		writeError(w, http.StatusConflict, err.Error())
+		s.logger.Error("trigger sync failed", "err", err)
+		writeError(w, http.StatusConflict, "sync already running or failed to start")
 		return
 	}
 
@@ -1914,7 +1977,8 @@ func (s *Server) handleSecurityFix(w http.ResponseWriter, r *http.Request) {
 		if _, err := os.Stat(jailPath); os.IsNotExist(err) {
 			jailConf := "[sshd]\nenabled = true\nmaxretry = 5\nbantime = 3600\nfindtime = 600\n"
 			if err := os.WriteFile(jailPath, []byte(jailConf), 0644); err != nil {
-				writeError(w, http.StatusInternalServerError, "could not write jail.local: "+err.Error())
+				s.logger.Error("could not write jail.local", "err", err)
+				writeError(w, http.StatusInternalServerError, "security config update failed")
 				return
 			}
 		}

internal/api/totp_handlers.go

@@ -0,0 +1,262 @@
+package api
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+
+	"github.com/archivmail/internal/audit"
+	"github.com/archivmail/internal/auth"
+)
+
+// ── PROJ-24: TOTP 2FA Handlers ───────────────────────────────────────────
+
+// handleTOTPSetupGet generates a new TOTP secret and QR code for the current user.
+// GET /api/auth/totp/setup
+func (s *Server) handleTOTPSetupGet(w http.ResponseWriter, r *http.Request) {
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	secret, otpauthURL, qrPNG, err := auth.GenerateSecret(sess.Username, "archivmail")
+	if err != nil {
+		s.logger.Error("totp setup: generate secret failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to generate TOTP secret")
+		return
+	}
+
+	// Encrypt the secret with AES-256-GCM before storing
+	encryptedSecret, err := s.authMgr.EncryptAES([]byte(secret))
+	if err != nil {
+		s.logger.Error("totp setup: encrypt secret failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to encrypt TOTP secret")
+		return
+	}
+
+	// Store encrypted secret in DB (not yet activated)
+	if err := s.users.SetTOTPSecret(r.Context(), sess.UserID, encryptedSecret); err != nil {
+		s.logger.Error("totp setup: store secret failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to store TOTP secret")
+		return
+	}
+
+	resp := map[string]interface{}{
+		"secret":     secret,
+		"otpauth_url": otpauthURL,
+	}
+	if len(qrPNG) > 0 {
+		resp["qr_code"] = base64.StdEncoding.EncodeToString(qrPNG)
+	}
+
+	writeJSON(w, http.StatusOK, resp)
+}
+
+// handleTOTPSetupPost confirms TOTP setup by verifying a code, then activates TOTP.
+// POST /api/auth/totp/setup  { "code": "123456" }
+func (s *Server) handleTOTPSetupPost(w http.ResponseWriter, r *http.Request) {
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	var req struct {
+		Code string `json:"code"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Code == "" {
+		writeError(w, http.StatusBadRequest, "missing or invalid code")
+		return
+	}
+
+	// Load encrypted secret from DB
+	encSecret, _, err := s.users.GetTOTPSecret(r.Context(), sess.UserID)
+	if err != nil || len(encSecret) == 0 {
+		writeError(w, http.StatusBadRequest, "no TOTP secret found, run setup first")
+		return
+	}
+
+	// Decrypt
+	plainSecret, err := s.authMgr.DecryptAESForHandler(encSecret)
+	if err != nil {
+		s.logger.Error("totp setup confirm: decrypt failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to decrypt TOTP secret")
+		return
+	}
+
+	// Validate code
+	if !auth.ValidateTOTP(string(plainSecret), req.Code) {
+		writeError(w, http.StatusBadRequest, "invalid TOTP code")
+		return
+	}
+
+	// Activate TOTP
+	if err := s.users.EnableTOTP(r.Context(), sess.UserID); err != nil {
+		s.logger.Error("totp setup confirm: enable failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to enable TOTP")
+		return
+	}
+
+	s.audlog.Log(audit.Entry{
+		EventType: audit.EventUserMgmt,
+		Username:  sess.Username,
+		IPAddress: remoteIP(r),
+		Detail:    "totp_enabled",
+		Success:   true,
+	})
+
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// handleTOTPDisable deactivates TOTP for the current user (requires a valid code).
+// DELETE /api/auth/totp  { "code": "123456" }
+func (s *Server) handleTOTPDisable(w http.ResponseWriter, r *http.Request) {
+	sess := sessionFromCtx(r.Context())
+	if sess.UserID == 0 {
+		writeError(w, http.StatusUnauthorized, "not authenticated")
+		return
+	}
+
+	var req struct {
+		Code string `json:"code"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Code == "" {
+		writeError(w, http.StatusBadRequest, "missing or invalid code")
+		return
+	}
+
+	// Load and decrypt secret
+	encSecret, enabled, err := s.users.GetTOTPSecret(r.Context(), sess.UserID)
+	if err != nil || !enabled || len(encSecret) == 0 {
+		writeError(w, http.StatusBadRequest, "TOTP is not enabled")
+		return
+	}
+
+	plainSecret, err := s.authMgr.DecryptAESForHandler(encSecret)
+	if err != nil {
+		s.logger.Error("totp disable: decrypt failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to decrypt TOTP secret")
+		return
+	}
+
+	if !auth.ValidateTOTP(string(plainSecret), req.Code) {
+		writeError(w, http.StatusBadRequest, "invalid TOTP code")
+		return
+	}
+
+	if err := s.users.DisableTOTP(r.Context(), sess.UserID); err != nil {
+		s.logger.Error("totp disable: failed", "err", err)
+		writeError(w, http.StatusInternalServerError, "failed to disable TOTP")
+		return
+	}
+
+	s.audlog.Log(audit.Entry{
+		EventType: audit.EventUserMgmt,
+		Username:  sess.Username,
+		IPAddress: remoteIP(r),
+		Detail:    "totp_disabled",
+		Success:   true,
+	})
+
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}
+
+// handleTOTPLogin completes a TOTP-pending login by validating the code.
+// POST /api/auth/totp  { "session_token": "...", "code": "123456" }
+func (s *Server) handleTOTPLogin(w http.ResponseWriter, r *http.Request) {
+	var req struct {
+		SessionToken string `json:"session_token"`
+		Code         string `json:"code"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.SessionToken == "" || req.Code == "" {
+		writeError(w, http.StatusBadRequest, "missing session_token or code")
+		return
+	}
+
+	token, user, err := s.authMgr.ValidateTOTPLogin(req.SessionToken, req.Code)
+	if err != nil {
+		s.audlog.Log(audit.Entry{
+			EventType: audit.EventLogin,
+			IPAddress: remoteIP(r),
+			Success:   false,
+			Detail:    "totp_login_failed: " + err.Error(),
+		})
+		writeError(w, http.StatusUnauthorized, "invalid TOTP code or expired session")
+		return
+	}
+
+	_ = s.users.UpdateLastLogin(user.ID)
+
+	s.audlog.Log(audit.Entry{
+		EventType: audit.EventLogin,
+		Username:  user.Username,
+		IPAddress: remoteIP(r),
+		Success:   true,
+		Detail:    "totp_login_completed",
+	})
+
+	http.SetCookie(w, &http.Cookie{
+		Name:     sessionCookieName,
+		Value:    token,
+		Path:     "/",
+		MaxAge:   8 * 3600,
+		HttpOnly: true,
+		SameSite: http.SameSiteStrictMode,
+	})
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"user": map[string]interface{}{
+			"id":       user.ID,
+			"username": user.Username,
+			"email":    user.Email,
+			"role":     user.Role,
+		},
+	})
+}
+
+// handleTOTPReset allows an admin to reset TOTP for a user.
+// POST /api/admin/users/{id}/totp/reset
+func (s *Server) handleTOTPReset(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid user id")
+		return
+	}
+
+	sess := sessionFromCtx(r.Context())
+
+	// Fetch target user
+	target, err := s.users.GetByID(id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, "user not found")
+		return
+	}
+
+	// SEC-02: Tenant isolation — domain_admin can only reset TOTP for users in their own tenant.
+	if sess.TenantID != nil {
+		if target.TenantID == nil || *target.TenantID != *sess.TenantID {
+			writeError(w, http.StatusForbidden, "access denied")
+			return
+		}
+	}
+
+	// Reset TOTP
+	if err := s.users.ResetTOTP(r.Context(), id, sess.Username); err != nil {
+		s.logger.Error("totp reset: failed", "err", err, "target_user", id, "admin", sess.Username)
+		writeError(w, http.StatusInternalServerError, "failed to reset TOTP")
+		return
+	}
+
+	s.audlog.Log(audit.Entry{
+		EventType: audit.EventUserMgmt,
+		Username:  sess.Username,
+		IPAddress: remoteIP(r),
+		Detail:    fmt.Sprintf("totp_reset_by_admin: TOTP reset by %s for user %s (id=%d)", sess.Username, target.Username, id),
+		Success:   true,
+	})
+
+	writeJSON(w, http.StatusOK, map[string]bool{"ok": true})
+}

internal/api/upload.go

@@ -53,7 +53,8 @@ type uploadJobSnapshot struct {
 func (s *Server) handleUpload(w http.ResponseWriter, r *http.Request) {
 	// 512 MB max total upload
 	if err := r.ParseMultipartForm(512 << 20); err != nil {
-		writeError(w, http.StatusBadRequest, "multipart parse failed: "+err.Error())
+		s.logger.Error("multipart parse failed", "err", err)
+		writeError(w, http.StatusBadRequest, "multipart parse failed")
 		return
 	}
 

internal/auth/auth.go

@@ -2,10 +2,13 @@ package auth
 
 import (
 	"context"
+	"crypto/aes"
+	"crypto/cipher"
 	"crypto/rand"
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"io"
 	"strings"
 	"time"
 
@@ -37,17 +40,21 @@ type Manager struct {
 	store           *userstore.Store
 	ldapStore       *ldapcfg.Store
 	jwtSecret       []byte
+	aesKey          []byte                 // PROJ-24: AES-256-GCM key for TOTP secret encryption
 	tenantLdapStore *ldapcfg.TenantStore   // PROJ-23: per-tenant LDAP config
 	tenantLookup    TenantDomainLookup     // PROJ-23: domain -> tenant_id resolution
 }
 
 // New creates a new auth Manager.
 // ldapStore may be nil; in that case LDAP fallback is disabled.
-func New(store *userstore.Store, ldapStore *ldapcfg.Store, jwtSecret string) *Manager {
+// aesKey is the hex-encoded AES-256 key for encrypting TOTP secrets.
+func New(store *userstore.Store, ldapStore *ldapcfg.Store, jwtSecret string, aesKey string) *Manager {
+	aesKeyBytes, _ := hex.DecodeString(aesKey)
 	return &Manager{
 		store:     store,
 		ldapStore: ldapStore,
 		jwtSecret: []byte(jwtSecret),
+		aesKey:    aesKeyBytes,
 	}
 }
 
@@ -61,11 +68,18 @@ func (m *Manager) SetTenantLDAP(tenantLdapStore *ldapcfg.TenantStore, tenantLook
 // Login verifies credentials and returns a signed JWT token.
 // It first attempts a local password check. If that fails and LDAP is
 // configured and enabled, it falls back to LDAP authentication.
-func (m *Manager) Login(username, password string) (string, *userstore.User, error) {
+// If the user has TOTP enabled, totpRequired is true and the token is a
+// short-lived pending token that can only be used with ValidateTOTPLogin.
+func (m *Manager) Login(username, password string) (token string, user *userstore.User, totpRequired bool, err error) {
 	// 1. Try local authentication first.
-	user, err := m.store.VerifyPassword(username, password)
+	user, err = m.store.VerifyPassword(username, password)
 	if err == nil {
-		return m.issueToken(user)
+		if user.TOTPEnabled {
+			t, e := m.issuePendingTOTPToken(user)
+			return t, user, true, e
+		}
+		t, u, e := m.issueToken(user)
+		return t, u, false, e
 	}
 
 	// 2. PROJ-23: Per-tenant LDAP — checked first so tenant config takes priority
@@ -107,7 +121,12 @@ func (m *Manager) Login(username, password string) (string, *userstore.User, err
 						}
 						ldapUser, upsertErr := m.store.UpsertLDAPUser(username, email, role, tenantID)
 						if upsertErr == nil {
-							return m.issueToken(ldapUser)
+							if ldapUser.TOTPEnabled {
+								t, e := m.issuePendingTOTPToken(ldapUser)
+								return t, ldapUser, true, e
+							}
+							t, u, e := m.issueToken(ldapUser)
+							return t, u, false, e
 						}
 					}
 				}
@@ -148,13 +167,18 @@ func (m *Manager) Login(username, password string) (string, *userstore.User, err
 				}
 				ldapUser, upsertErr := m.store.UpsertLDAPUser(username, email, role, nil)
 				if upsertErr == nil {
-					return m.issueToken(ldapUser)
+					if ldapUser.TOTPEnabled {
+						t, e := m.issuePendingTOTPToken(ldapUser)
+						return t, ldapUser, true, e
+					}
+					t, u, e := m.issueToken(ldapUser)
+					return t, u, false, e
 				}
 			}
 		}
 	}
 
-	return "", nil, fmt.Errorf("auth: login: invalid credentials")
+	return "", nil, false, fmt.Errorf("auth: login: invalid credentials")
 }
 
 // issueToken signs a JWT for the given user and returns the token string.
@@ -186,6 +210,99 @@ func (m *Manager) issueToken(user *userstore.User) (string, *userstore.User, err
 	return signed, user, nil
 }
 
+// issuePendingTOTPToken issues a short-lived JWT (5 min) that signals TOTP is required.
+// This token MUST NOT be accepted as a full auth token — only for /api/auth/totp.
+func (m *Manager) issuePendingTOTPToken(user *userstore.User) (string, error) {
+	jti := generateJTI()
+	now := time.Now()
+
+	claims := jwt.MapClaims{
+		"sub":          user.Username,
+		"uid":          user.ID,
+		"jti":          jti,
+		"iat":          now.Unix(),
+		"exp":          now.Add(5 * time.Minute).Unix(),
+		"totp_pending": true,
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	signed, err := token.SignedString(m.jwtSecret)
+	if err != nil {
+		return "", fmt.Errorf("auth: sign pending totp token: %w", err)
+	}
+	return signed, nil
+}
+
+// ValidateTOTPLogin validates a pending TOTP token and TOTP code, then issues a full JWT.
+func (m *Manager) ValidateTOTPLogin(pendingToken, code string) (string, *userstore.User, error) {
+	// Parse the pending token
+	token, err := jwt.Parse(pendingToken, func(t *jwt.Token) (interface{}, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("auth: unexpected signing method: %v", t.Header["alg"])
+		}
+		return m.jwtSecret, nil
+	})
+	if err != nil {
+		return "", nil, fmt.Errorf("auth: invalid pending token: %w", err)
+	}
+	if !token.Valid {
+		return "", nil, errors.New("auth: pending token not valid")
+	}
+
+	claims, ok := token.Claims.(jwt.MapClaims)
+	if !ok {
+		return "", nil, errors.New("auth: bad claims")
+	}
+
+	// Verify this is actually a pending TOTP token
+	pending, _ := claims["totp_pending"].(bool)
+	if !pending {
+		return "", nil, errors.New("auth: not a pending TOTP token")
+	}
+
+	// Extract user ID
+	var userID int64
+	switch v := claims["uid"].(type) {
+	case float64:
+		userID = int64(v)
+	case int64:
+		userID = v
+	default:
+		return "", nil, errors.New("auth: missing uid in pending token")
+	}
+
+	// Load user from DB
+	user, err := m.store.GetByID(userID)
+	if err != nil {
+		return "", nil, fmt.Errorf("auth: user lookup: %w", err)
+	}
+	if !user.TOTPEnabled {
+		return "", nil, errors.New("auth: TOTP not enabled for this user")
+	}
+
+	// Load and decrypt TOTP secret
+	encSecret, enabled, err := m.store.GetTOTPSecret(context.Background(), userID)
+	if err != nil {
+		return "", nil, fmt.Errorf("auth: get totp secret: %w", err)
+	}
+	if !enabled || len(encSecret) == 0 {
+		return "", nil, errors.New("auth: TOTP not configured")
+	}
+
+	plainSecret, err := m.decryptAES(encSecret)
+	if err != nil {
+		return "", nil, fmt.Errorf("auth: decrypt totp secret: %w", err)
+	}
+
+	// Validate the TOTP code
+	if !ValidateTOTP(string(plainSecret), code) {
+		return "", nil, errors.New("auth: invalid TOTP code")
+	}
+
+	// Issue a full auth token
+	return m.issueToken(user)
+}
+
 // ValidateToken parses and validates the token, checking the blacklist.
 func (m *Manager) ValidateToken(tokenStr string) (*Session, error) {
 	token, err := jwt.Parse(tokenStr, func(t *jwt.Token) (interface{}, error) {
@@ -206,6 +323,11 @@ func (m *Manager) ValidateToken(tokenStr string) (*Session, error) {
 		return nil, errors.New("auth: bad claims")
 	}
 
+	// PROJ-24: Reject pending TOTP tokens — they must not be used as full auth tokens.
+	if pending, _ := claims["totp_pending"].(bool); pending {
+		return nil, errors.New("auth: pending TOTP token cannot be used for authentication")
+	}
+
 	jti, _ := claims["jti"].(string)
 	blacklisted, err := m.store.IsBlacklisted(jti)
 	if err != nil {
@@ -361,3 +483,64 @@ func generateJTI() string {
 	}
 	return hex.EncodeToString(b)
 }
+
+// ── PROJ-24: AES-256-GCM encryption helpers for TOTP secrets ─────────────
+
+// EncryptAES encrypts plaintext using AES-256-GCM with the manager's AES key.
+// The 12-byte nonce is prepended to the ciphertext.
+func (m *Manager) EncryptAES(plaintext []byte) ([]byte, error) {
+	return encryptAESGCM(m.aesKey, plaintext)
+}
+
+// decryptAES decrypts data encrypted with EncryptAES.
+func (m *Manager) decryptAES(data []byte) ([]byte, error) {
+	return decryptAESGCM(m.aesKey, data)
+}
+
+// DecryptAESForHandler exposes AES decryption for use in API handlers (e.g., TOTP setup confirmation).
+func (m *Manager) DecryptAESForHandler(data []byte) ([]byte, error) {
+	return decryptAESGCM(m.aesKey, data)
+}
+
+func encryptAESGCM(key, plaintext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("auth: aes cipher: %w", err)
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, fmt.Errorf("auth: gcm: %w", err)
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, fmt.Errorf("auth: random nonce: %w", err)
+	}
+	ciphertext := gcm.Seal(nonce, nonce, plaintext, nil)
+	return ciphertext, nil
+}
+
+func decryptAESGCM(key, data []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("auth: aes cipher: %w", err)
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, fmt.Errorf("auth: gcm: %w", err)
+	}
+	nonceSize := gcm.NonceSize()
+	if len(data) < nonceSize {
+		return nil, fmt.Errorf("auth: ciphertext too short")
+	}
+	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, fmt.Errorf("auth: decrypt: %w", err)
+	}
+	return plaintext, nil
+}
+
+// GetUserStore returns the underlying user store (used by TOTP handlers).
+func (m *Manager) GetUserStore() *userstore.Store {
+	return m.store
+}

internal/auth/auth_test.go

@@ -30,17 +30,20 @@ func newTestAuth(t *testing.T) (*auth.Manager, *userstore.Store) {
 		Role:     userstore.RoleUser,
 	})
 
-	mgr := auth.New(store, nil, "test-jwt-secret-32chars-long-enough")
+	mgr := auth.New(store, nil, "test-jwt-secret-32chars-long-enough", "0000000000000000000000000000000000000000000000000000000000000000")
 	return mgr, store
 }
 
 func TestLoginSuccess(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	token, user, err := mgr.Login("testadmin", "adminpass")
+	token, user, totpRequired, err := mgr.Login("testadmin", "adminpass")
 	if err != nil {
 		t.Fatalf("Login: %v", err)
 	}
+	if totpRequired {
+		t.Error("expected totpRequired=false for user without TOTP")
+	}
 	if token == "" {
 		t.Error("expected non-empty token")
 	}
@@ -55,7 +58,7 @@ func TestLoginSuccess(t *testing.T) {
 func TestLoginWrongPassword(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	if _, _, err := mgr.Login("testadmin", "wrongpass"); err == nil {
+	if _, _, _, err := mgr.Login("testadmin", "wrongpass"); err == nil {
 		t.Error("expected error for wrong password")
 	}
 }
@@ -63,7 +66,7 @@ func TestLoginWrongPassword(t *testing.T) {
 func TestLoginUnknownUser(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	if _, _, err := mgr.Login("nobody", "pw"); err == nil {
+	if _, _, _, err := mgr.Login("nobody", "pw"); err == nil {
 		t.Error("expected error for unknown user")
 	}
 }
@@ -71,7 +74,7 @@ func TestLoginUnknownUser(t *testing.T) {
 func TestTokenValidation(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	token, _, _ := mgr.Login("testadmin", "adminpass")
+	token, _, _, _ := mgr.Login("testadmin", "adminpass")
 	sess, err := mgr.ValidateToken(token)
 	if err != nil {
 		t.Fatalf("ValidateToken: %v", err)
@@ -90,7 +93,7 @@ func TestTokenValidation(t *testing.T) {
 func TestTokenTampering(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	token, _, _ := mgr.Login("testadmin", "adminpass")
+	token, _, _, _ := mgr.Login("testadmin", "adminpass")
 	tampered := token + "x"
 
 	if _, err := mgr.ValidateToken(tampered); err == nil {
@@ -101,7 +104,7 @@ func TestTokenTampering(t *testing.T) {
 func TestLogout(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	token, _, _ := mgr.Login("testadmin", "adminpass")
+	token, _, _, _ := mgr.Login("testadmin", "adminpass")
 
 	// Token valid before logout
 	if _, err := mgr.ValidateToken(token); err != nil {
@@ -146,8 +149,8 @@ func TestHasRole(t *testing.T) {
 func TestMultipleSessionsIndependent(t *testing.T) {
 	mgr, _ := newTestAuth(t)
 
-	token1, _, _ := mgr.Login("testadmin", "adminpass")
-	token2, _, _ := mgr.Login("testadmin", "adminpass")
+	token1, _, _, _ := mgr.Login("testadmin", "adminpass")
+	token2, _, _, _ := mgr.Login("testadmin", "adminpass")
 
 	if token1 == token2 {
 		t.Error("two logins should produce different tokens (different JTIs)")

internal/auth/totp.go

@@ -0,0 +1,50 @@
+package auth
+
+import (
+	"bytes"
+	"image/png"
+	"time"
+
+	"github.com/pquerna/otp"
+	"github.com/pquerna/otp/totp"
+)
+
+// GenerateSecret creates a new TOTP secret for the given user.
+// Returns the base32-encoded secret, the otpauth:// URL, and a QR code as PNG bytes.
+func GenerateSecret(username, issuer string) (secret string, otpauthURL string, qrPNG []byte, err error) {
+	key, err := totp.Generate(totp.GenerateOpts{
+		Issuer:      issuer,
+		AccountName: username,
+		SecretSize:  20,
+		Algorithm:   otp.AlgorithmSHA1,
+		Digits:      otp.DigitsSix,
+		Period:      30,
+	})
+	if err != nil {
+		return "", "", nil, err
+	}
+	secret = key.Secret()
+	otpauthURL = key.URL()
+
+	img, err := key.Image(200, 200)
+	if err != nil {
+		return secret, otpauthURL, nil, nil // QR code is optional
+	}
+	var buf bytes.Buffer
+	if encErr := png.Encode(&buf, img); encErr == nil {
+		qrPNG = buf.Bytes()
+	}
+	return secret, otpauthURL, qrPNG, nil
+}
+
+// ValidateTOTP checks whether the given code is valid for the base32 secret.
+// Allows +/- 1 time step (30s) tolerance.
+func ValidateTOTP(secret, code string) bool {
+	valid, err := totp.ValidateCustom(code, secret, time.Now().UTC(), totp.ValidateOpts{
+		Period:    30,
+		Skew:     1,
+		Digits:   otp.DigitsSix,
+		Algorithm: otp.AlgorithmSHA1,
+	})
+	return err == nil && valid
+}

internal/userstore/userstore.go

@@ -23,14 +23,17 @@ const (
 
 // User represents a user account in the system.
 type User struct {
-	ID        int64
-	Username  string
-	Email     string
-	Role      string
-	Source    string // "local" or "ldap"
-	Active    bool
-	CreatedAt time.Time
-	TenantID  *int64 `json:"tenant_id,omitempty"`
+	ID          int64
+	Username    string
+	Email       string
+	Role        string
+	Source      string // "local" or "ldap"
+	Active      bool
+	CreatedAt   time.Time
+	TenantID    *int64     `json:"tenant_id,omitempty"`
+	TOTPEnabled bool       `json:"totp_enabled"`
+	TOTPResetAt *time.Time `json:"totp_reset_at,omitempty"`
+	TOTPResetBy *string    `json:"totp_reset_by,omitempty"`
 }
 
 // CreateUserRequest holds parameters for creating a new user.
@@ -99,6 +102,16 @@ func (s *Store) initSchema(ctx context.Context) error {
 		CREATE INDEX IF NOT EXISTS idx_login_attempts_username_time ON login_attempts (username, attempted_at);
 		CREATE INDEX IF NOT EXISTS idx_users_tenant ON users (tenant_id);
 	`)
+	if err != nil {
+		return err
+	}
+	// PROJ-24: TOTP 2FA columns
+	_, err = s.pool.Exec(ctx, `
+		ALTER TABLE users ADD COLUMN IF NOT EXISTS totp_secret   BYTEA;
+		ALTER TABLE users ADD COLUMN IF NOT EXISTS totp_enabled  BOOLEAN NOT NULL DEFAULT false;
+		ALTER TABLE users ADD COLUMN IF NOT EXISTS totp_reset_at TIMESTAMPTZ;
+		ALTER TABLE users ADD COLUMN IF NOT EXISTS totp_reset_by TEXT;
+	`)
 	return err
 }
 
@@ -134,7 +147,7 @@ func (s *Store) Create(req CreateUserRequest) (*User, error) {
 func (s *Store) GetByID(id int64) (*User, error) {
 	ctx := context.Background()
 	row := s.pool.QueryRow(ctx,
-		`SELECT id, username, email, role, source, active, created_at, tenant_id FROM users WHERE id = $1`, id,
+		`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by FROM users WHERE id = $1`, id,
 	)
 	return scanUser(row)
 }
@@ -143,7 +156,7 @@ func (s *Store) GetByID(id int64) (*User, error) {
 func (s *Store) GetByUsername(username string) (*User, error) {
 	ctx := context.Background()
 	row := s.pool.QueryRow(ctx,
-		`SELECT id, username, email, role, source, active, created_at, tenant_id FROM users WHERE username = $1`, username,
+		`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by FROM users WHERE username = $1`, username,
 	)
 	return scanUser(row)
 }
@@ -153,13 +166,13 @@ func (s *Store) GetByUsername(username string) (*User, error) {
 func (s *Store) VerifyPassword(username, password string) (*User, error) {
 	ctx := context.Background()
 	row := s.pool.QueryRow(ctx,
-		`SELECT id, username, email, role, source, active, created_at, tenant_id, password_hash FROM users WHERE username = $1`,
+		`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by, password_hash FROM users WHERE username = $1`,
 		username,
 	)
 
 	var u User
 	var hash string
-	err := row.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID, &hash)
+	err := row.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID, &u.TOTPEnabled, &u.TOTPResetAt, &u.TOTPResetBy, &hash)
 	if errors.Is(err, pgx.ErrNoRows) {
 		return nil, errors.New("userstore: user not found")
 	}
@@ -231,10 +244,10 @@ func (s *Store) List(role string) ([]*User, error) {
 
 	if role == "" {
 		rows, err = s.pool.Query(ctx,
-			`SELECT id, username, email, role, source, active, created_at, tenant_id FROM users ORDER BY id`)
+			`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by FROM users ORDER BY id`)
 	} else {
 		rows, err = s.pool.Query(ctx,
-			`SELECT id, username, email, role, source, active, created_at, tenant_id FROM users WHERE role = $1 ORDER BY id`, role)
+			`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by FROM users WHERE role = $1 ORDER BY id`, role)
 	}
 	if err != nil {
 		return nil, fmt.Errorf("userstore: list: %w", err)
@@ -255,7 +268,7 @@ func (s *Store) List(role string) ([]*User, error) {
 // ListByTenant returns all users belonging to a specific tenant.
 func (s *Store) ListByTenant(ctx context.Context, tenantID int64) ([]*User, error) {
 	rows, err := s.pool.Query(ctx,
-		`SELECT id, username, email, role, source, active, created_at, tenant_id FROM users WHERE tenant_id = $1 ORDER BY id`,
+		`SELECT id, username, email, role, source, active, created_at, tenant_id, totp_enabled, totp_reset_at, totp_reset_by FROM users WHERE tenant_id = $1 ORDER BY id`,
 		tenantID,
 	)
 	if err != nil {
@@ -381,7 +394,7 @@ func (s *Store) UpsertLDAPUser(username, email, role string, tenantID *int64) (*
 
 func scanUser(row pgx.Row) (*User, error) {
 	var u User
-	err := row.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID)
+	err := row.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID, &u.TOTPEnabled, &u.TOTPResetAt, &u.TOTPResetBy)
 	if errors.Is(err, pgx.ErrNoRows) {
 		return nil, fmt.Errorf("userstore: not found")
 	}
@@ -393,8 +406,63 @@ func scanUser(row pgx.Row) (*User, error) {
 
 func scanUserRow(rows pgx.Rows) (*User, error) {
 	var u User
-	if err := rows.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID); err != nil {
+	if err := rows.Scan(&u.ID, &u.Username, &u.Email, &u.Role, &u.Source, &u.Active, &u.CreatedAt, &u.TenantID, &u.TOTPEnabled, &u.TOTPResetAt, &u.TOTPResetBy); err != nil {
 		return nil, fmt.Errorf("userstore: scan row: %w", err)
 	}
 	return &u, nil
 }
+
+// ── PROJ-24: TOTP 2FA Methods ────────────────────────────────────────────
+
+// SetTOTPSecret stores the encrypted TOTP secret (not yet activated).
+func (s *Store) SetTOTPSecret(ctx context.Context, userID int64, encryptedSecret []byte) error {
+	_, err := s.pool.Exec(ctx, `UPDATE users SET totp_secret = $1 WHERE id = $2`, encryptedSecret, userID)
+	if err != nil {
+		return fmt.Errorf("userstore: set totp secret: %w", err)
+	}
+	return nil
+}
+
+// EnableTOTP activates TOTP for the user (after code confirmation).
+func (s *Store) EnableTOTP(ctx context.Context, userID int64) error {
+	_, err := s.pool.Exec(ctx, `UPDATE users SET totp_enabled = true WHERE id = $1`, userID)
+	if err != nil {
+		return fmt.Errorf("userstore: enable totp: %w", err)
+	}
+	return nil
+}
+
+// DisableTOTP deactivates TOTP and removes the secret (user self-service).
+func (s *Store) DisableTOTP(ctx context.Context, userID int64) error {
+	_, err := s.pool.Exec(ctx, `UPDATE users SET totp_enabled = false, totp_secret = NULL WHERE id = $1`, userID)
+	if err != nil {
+		return fmt.Errorf("userstore: disable totp: %w", err)
+	}
+	return nil
+}
+
+// ResetTOTP resets TOTP for a user (admin action) and logs who performed the reset.
+func (s *Store) ResetTOTP(ctx context.Context, userID int64, resetBy string) error {
+	_, err := s.pool.Exec(ctx,
+		`UPDATE users SET totp_enabled = false, totp_secret = NULL, totp_reset_at = NOW(), totp_reset_by = $1 WHERE id = $2`,
+		resetBy, userID,
+	)
+	if err != nil {
+		return fmt.Errorf("userstore: reset totp: %w", err)
+	}
+	return nil
+}
+
+// GetTOTPSecret returns the encrypted TOTP secret and enabled status for a user.
+func (s *Store) GetTOTPSecret(ctx context.Context, userID int64) (secret []byte, enabled bool, err error) {
+	err = s.pool.QueryRow(ctx,
+		`SELECT totp_secret, totp_enabled FROM users WHERE id = $1`, userID,
+	).Scan(&secret, &enabled)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, false, fmt.Errorf("userstore: user not found")
+	}
+	if err != nil {
+		return nil, false, fmt.Errorf("userstore: get totp secret: %w", err)
+	}
+	return secret, enabled, nil
+}