.Net 全局过滤，防止SQL注入

问题背景：由于公司需要整改的老系统的漏洞检查，而系统就是没有使用参数化SQL即拼接查询语句开发的程序，导致漏洞扫描出现大量SQL注入问题。

解决方法：最好的办法就是不写拼接SQL，改用参数化SQL，推荐新项目使用，老项目改起来比较麻烦，花费的时间也多，最后选择用全局SQL过滤器过滤前端发送的请求内容。

代码：

/// <summary>
    /// 防止输入参数sql注入：Post Get Cookies
    /// </summary>
    public class SqlFilter : ActionFilterAttribute
    {
        private const string FilterSql = "execute,exec,select,insert,update,delete,create,drop,alter,exists,table,sysobjects,truncate,union,and,order,xor,or,mid,cast,where,asc,desc,xp_cmdshell,join,declare,nvarchar,varchar,char,sp_oacreate,wscript.shell,xp_regwrite,',%,;,--";

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            // -----------------------防 Post 注入-----------------------
            if (filterContext.HttpContext.Request.Form != null)
            {
                var isReadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
                //把 Form 属性改为可读写
                isReadonly?.SetValue(filterContext.HttpContext.Request.Form, false, null);

                for (var k = 0; k < filterContext.HttpContext.Request.Form.Count; k++)
                {
                    var inputKey = filterContext.HttpContext.Request.Form.Keys[k];
                    var inputValue = filterContext.HttpContext.Request.Form[inputKey];
                    var filters = FilterSql.Split(',');
                    inputValue = filters.Aggregate(inputValue, (current, filterSql) => Regex.Replace(current, filterSql, "", RegexOptions.IgnoreCase));
                    filterContext.HttpContext.Request.Form[inputKey] = inputValue;
                }
            }


            // -----------------------防 GET 注入-----------------------
            if (filterContext.HttpContext.Request.QueryString != null)
            {
                var isReadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
                //把 QueryString 属性改为可读写
                isReadonly?.SetValue(filterContext.HttpContext.Request.QueryString, false, null);

                for (var k = 0; k < filterContext.HttpContext.Request.QueryString.Count; k++)
                {
                    var inputKey = filterContext.HttpContext.Request.QueryString.Keys[k];
                    var inputValue = filterContext.HttpContext.Request.QueryString[inputKey];
                    var filters = FilterSql.Split(',');
                    inputValue = filters.Aggregate(inputValue, (current, filterSql) => Regex.Replace(current, filterSql, "", RegexOptions.IgnoreCase));
                    filterContext.HttpContext.Request.QueryString[inputKey] = inputValue;
                }
            }


            // -----------------------防 Cookies 注入-----------------------
            if (filterContext.HttpContext.Request.Cookies.Count > 0)
            {
                var isReadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
                //把 Cookies 属性改为可读写
                isReadonly?.SetValue(filterContext.HttpContext.Request.Cookies, false, null);

                for (var k = 0; k < filterContext.HttpContext.Request.Cookies.Count; k++)
                {
                    var inputKey = filterContext.HttpContext.Request.Cookies.Keys[k];
                    var inputValue = filterContext.HttpContext.Request.Cookies[inputKey]?.Value;
                    var filters = FilterSql.Split(',');
                    inputValue = filters.Aggregate(inputValue, (current, filterSql) => Regex.Replace(current, filterSql, "", RegexOptions.IgnoreCase));
                    if (!(filterContext.HttpContext.Request.Cookies[inputKey] is null))
                    {
                        filterContext.HttpContext.Request.Cookies[inputKey].Value = inputValue;
                    }
                }
            }
            base.OnActionExecuting(filterContext);
        }
    }