Fix Turnstile verification encoding and admin login diagnostics

go-backend/internal/handlers/admin_handler.go

@@ -83,17 +83,24 @@ func (h *AdminHandler) AdminLogin(c *gin.Context) {
 
 	// Verify Turnstile token
 	if h.turnstileSecret != "" {
+		if strings.TrimSpace(req.TurnstileToken) == "" {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "Security verification failed"})
+			return
+		}
 		turnstileService := services.NewTurnstileService(h.turnstileSecret)
-		remoteIP := c.ClientIP()
+		turnstileResp, err := turnstileService.VerifyToken(req.TurnstileToken, "")
-		turnstileResp, err := turnstileService.VerifyToken(req.TurnstileToken, remoteIP)
 		if err != nil {
 			log.Error().Err(err).Msg("Admin login: Turnstile verification failed")
 			c.JSON(http.StatusBadRequest, gin.H{"error": "Security verification failed"})
 			return
 		}
 		if !turnstileResp.Success {
-			log.Warn().Strs("errors", turnstileResp.ErrorCodes).Msg("Admin login: Turnstile validation failed")
+			log.Warn().
-			c.JSON(http.StatusForbidden, gin.H{"error": "Security verification failed. Please try again."})
+				Strs("errors", turnstileResp.ErrorCodes).
+				Str("hostname", turnstileResp.Hostname).
+				Str("action", turnstileResp.Action).
+				Msg("Admin login: Turnstile validation failed")
+			c.JSON(http.StatusBadRequest, gin.H{"error": "Security verification failed"})
 			return
 		}
 	}

go-backend/internal/services/turnstile_service.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
 	"time"
 )
 
@@ -39,22 +40,18 @@ func (s *TurnstileService) VerifyToken(token, remoteIP string) (*TurnstileRespon
 		return &TurnstileResponse{Success: true}, nil
 	}
 
-	// Prepare the request data
+	// Prepare the request data (properly form-encoded)
-	data := fmt.Sprintf(
+	// Note: We intentionally do NOT send remoteip. In practice this often causes false negatives
-		"secret=%s&response=%s",
+	// behind proxies/CDNs (Cloudflare), and Turnstile does not require it.
-		s.secretKey,
+	form := url.Values{}
-		token,
+	form.Set("secret", s.secretKey)
-	)
+	form.Set("response", token)
-	
-	if remoteIP != "" {
-		data += fmt.Sprintf("&remoteip=%s", remoteIP)
-	}
 
 	// Make the request to Cloudflare
 	resp, err := s.client.Post(
 		"https://challenges.cloudflare.com/turnstile/v0/siteverify",
 		"application/x-www-form-urlencoded",
-		bytes.NewBufferString(data),
+		bytes.NewBufferString(form.Encode()),
 	)
 	if err != nil {
 		return nil, fmt.Errorf("failed to verify turnstile token: %w", err)