fix: harden notification cache synchronization

cmd/dashboard/controller/notification.go

@@ -1,6 +1,7 @@
 package controller
 
 import (
+	"net/http"
 	"slices"
 	"strconv"
 
@@ -12,6 +13,8 @@ import (
 	"github.com/nezhahq/nezha/service/singleton"
 )
 
+const notificationBatchDeleteMaxBodyBytes = 1 << 20
+
 // List notification
 // @Summary List notification
 // @Security BearerAuth
@@ -174,6 +177,9 @@ func updateNotification(c *gin.Context) (any, error) {
 // @Router /batch-delete/notification [post]
 func batchDeleteNotification(c *gin.Context) (any, error) {
 	var n []uint64
+	if c.Request != nil && c.Request.Body != nil {
+		c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, notificationBatchDeleteMaxBodyBytes)
+	}
 	if err := c.ShouldBindJSON(&n); err != nil {
 		return nil, err
 	}

cmd/dashboard/controller/notification_body_limit_test.go

@@ -0,0 +1,25 @@
+package controller
+
+import (
+	"bytes"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func TestBatchDeleteNotificationCapsRequestBody(t *testing.T) {
+	body := append(bytes.Repeat([]byte{' '}, notificationBatchDeleteMaxBodyBytes+1), '[', ']')
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/batch-delete/notification", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = req
+
+	_, err := batchDeleteNotification(c)
+	if err == nil || !strings.Contains(err.Error(), "request body too large") {
+		t.Fatalf("oversized request body was not rejected by MaxBytesReader: %v", err)
+	}
+}