C# 检查字符串,防SQL注入攻击

SQL注入攻击如下,CheckParams函数,接收参数任意,如参数中有字符串,则对字符串进行检查,如参数中有集合(如Array之类,总之是实现了ICollection的),则对集合中的字符串元素进行检查.大家可根据具体情况来定要过滤的字符,我这个例子里暂定为=号和'号,实际上我个人认为,过滤了这两个,似乎要进行SQL注入就已经比较困难了,当然,我对SQL是菜鸟,欢迎高手指正,谢谢.

方法一

bool CheckParams(params object[] args)
{ string[] Lawlesses={"=","'"};
if(Lawlesses==null||Lawlesses.Length<=0)return true; //构造正则表达式,
例:Lawlesses是=号和'号,则正则表达式为 .*[=}'].* (正则表达式相关内容请见MSDN) 另外,由于我是想做通用而且容易修改的函数,所以多了一步由字符数组到正则表达式,实际使用中,直接写正则表达式亦可;
string str_Regex=".*[";
for(int i=0;i< Lawlesses.Length-1;i++)
str_Regex+=Lawlesses[i]+"|";
str_Regex+=Lawlesses[Lawlesses.Length-1]+"].*";
// foreach(object arg in args)
{ if(arg is string)//如果是字符串,直接检查
{ if(Regex.Matches(arg.ToString(),str_Regex).Count>0)
return false; }
else if(arg is ICollection)//如果是一个集合,则检查集合内元素是否字符串,是字符串,就进行检查 { foreach(object obj in (ICollection)arg)
{ if(obj is string)
{ if(Regex.Matches(obj.ToString(),str_Regex).Count>0)
return false;
}
}
}
}
return true;}

方法二

一.如果参数全为数字:
// 检查字符串是否全为数字
public static bool IsNum(string Str)
{
     bool blResult = true;
     if (Str == "")
         blResult = false;
     else
     {
         foreach (char Char in Str)
         {
             if (!Char.IsNumber(Char))
             {
                 blResult = false;
                 break;
             }
         }
         if (blResult)
             if (int.Parse(Str) == 0)
                 blResult = false;
     }
     return blResult;
}http://www.pconcool.com

应用:
string Topicid = Request.QueryString["Topicid"];
if (!IsNum(Topicid))
     Server.Transfer("Error.aspx?ErrID=404");


二.如果参数为文本.

// Html转换
public static string htmlstr(string chr)
{
     if(chr==null)
         return "";
     chr=chr.Replace("<","<");
     chr=chr.Replace(">",">");
     chr=chr.Replace("/n","<br>");
     chr=chr.Replace("/"",""");
     chr=chr.Replace("'","'");
     chr=chr.Replace(" ","?");
     chr=chr.Replace("/r","");
     return(chr);
}
应用:string strClass = htmlstr(Request.QueryString["ClassName"]);

方法三：.net整站防sql注入

将下面的代码加入到Global.asax文件中：
     /// <summary>
    /// 防止SQL注入
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
void Application_BeginRequest(Object sender, EventArgs e)
     {
         StartProcessRequest();

     }

     #region SQL注入式攻击代码分析
     /// <summary>
     /// 处理用户提交的请求
     /// </summary>
     private void StartProcessRequest()
     {
         try
         {
             string getkeys = "";
             string sqlErrorPage = "error.aspx";//转向的错误提示页面
             if (System.Web.HttpContext.Current.Request.QueryString != null)
             {

                 for (int i = 0; i < System.Web.HttpContext.Current.Request.QueryString.Count; i++)
                 {
                     getkeys = System.Web.HttpContext.Current.Request.QueryString.Keys[i];
                     if (!ProcessSqlStr(System.Web.HttpContext.Current.Request.QueryString[getkeys]))
                     {
                         System.Web.HttpContext.Current.Response.Redirect(sqlErrorPage);
                         System.Web.HttpContext.Current.Response.End();
                     }
                 }
             }
             if (System.Web.HttpContext.Current.Request.Form != null)
             {
                 for (int i = 0; i < System.Web.HttpContext.Current.Request.Form.Count; i++)
                 {
                     getkeys = System.Web.HttpContext.Current.Request.Form.Keys[i];
                     if (getkeys == "__VIEWSTATE") continue;
                     if (!ProcessSqlStr(System.Web.HttpContext.Current.Request.Form[getkeys]))
                     {
                         System.Web.HttpContext.Current.Response.Redirect(sqlErrorPage);
                         System.Web.HttpContext.Current.Response.End();
                     }
                 }
             }
         }
         catch
         {
             // 错误处理: 处理用户提交信息!
         }
     }
     /// <summary>
     /// 分析用户请求是否正常
     /// </summary>
     /// <param name="Str">传入用户提交数据 </param>
     /// <returns>返回是否含有SQL注入式攻击代码 </returns>
     private bool ProcessSqlStr(string Str)
     {
         bool ReturnValue = true;
         try
         {
             if (Str.Trim() != "")
             {
                 string SqlStr = "and .exec .insert .select .delete .update .count .* .chr .mid .master .truncate .char .declare";

                 string[] anySqlStr = SqlStr.Split('.');
                 foreach (string ss in anySqlStr)
                 {
                     if (Str.ToLower().IndexOf(ss) >= 0)
                     {
                         ReturnValue = false;
                         break;
                     }
                 }
             }
         }
         catch
         {
             ReturnValue = false;
         }
         return ReturnValue;
     }
     #endregion

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