什么是SQL注入？
我理解的sql注入就是一些人可以通過惡意的參數(shù)輸入，讓后臺執(zhí)行這段SQL，然后達(dá)到獲取數(shù)據(jù)或者破壞數(shù)據(jù)庫的目的！
舉個(gè)簡單的查詢例子，后臺sql是拼接的：select * from Test where name='+參數(shù)傳遞+'；前臺頁面要求輸入name，那么黑客可以輸入： ';DROP TABLE Test;-- 不要小瞧這一段SQL代碼：
select * from Test where name=' ';DROP TABLE Test;--'；在SQL中是正確的，可執(zhí)行的，但是執(zhí)行后整個(gè)Test表都刪除了，網(wǎng)站崩潰！
最好的解決方法
最好的辦法就是不寫拼接SQL，改用參數(shù)化SQL，推薦新項(xiàng)目使用。這里不做介紹，感興趣的朋友可以自行搜索一下，本文介紹的方法適合老項(xiàng)目，就是沒有使用參數(shù)化SQL開發(fā)的程序。
使用過濾函數(shù)來過濾
將SQL一些危險(xiǎn)的關(guān)鍵字，還有注釋百分號以及分號這些根本在我們正常寫代碼的時(shí)候根本不會出現(xiàn)的字符都過濾掉，這樣能最大限度的保證SQL執(zhí)行是安全的，代碼如下：
public class SqlFilter{ public static void Filter() { string fileter_sql = "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,',%,;,--"; try { // -----------------------防 Post 注入----------------------- if (HttpContext.Current.Request.Form != null) { PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic); //把 Form 屬性改為可讀寫 isreadonly.SetValue(HttpContext.Current.Request.Form, false, null); for (int k = 0; k < System.Web.HttpContext.Current.Request.Form.Count; k++) { string getsqlkey = HttpContext.Current.Request.Form.Keys[k]; string sqlstr = HttpContext.Current.Request.Form[getsqlkey]; string[] replace_sqls = fileter_sql.Split(','); foreach (string replace_sql in replace_sqls) { sqlstr = Regex.Replace(sqlstr, replace_sql, "", RegexOptions.IgnoreCase); } HttpContext.Current.Request.Form[getsqlkey] = sqlstr; } } // -----------------------防 GET 注入----------------------- if (HttpContext.Current.Request.QueryString != null) { PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic); //把 QueryString 屬性改為可讀寫 isreadonly.SetValue(HttpContext.Current.Request.QueryString, false, null); for (int k = 0; k < System.Web.HttpContext.Current.Request.QueryString.Count; k++) { string getsqlkey = HttpContext.Current.Request.QueryString.Keys[k]; string sqlstr = HttpContext.Current.Request.QueryString[getsqlkey]; string[] replace_sqls = fileter_sql.Split(','); foreach (string replace_sql in replace_sqls) { sqlstr = Regex.Replace(sqlstr, replace_sql, "", RegexOptions.IgnoreCase); } HttpContext.Current.Request.QueryString[getsqlkey] = sqlstr; } } // -----------------------防 Cookies 注入----------------------- if (HttpContext.Current.Request.Cookies != null) { PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic); //把 Cookies 屬性改為可讀寫 isreadonly.SetValue(HttpContext.Current.Request.Cookies, false, null); for (int k = 0; k < System.Web.HttpContext.Current.Request.Cookies.Count; k++) { string getsqlkey = HttpContext.Current.Request.Cookies.Keys[k]; string sqlstr = HttpContext.Current.Request.Cookies[getsqlkey].Value; string[] replace_sqls = fileter_sql.Split(','); foreach (string replace_sql in replace_sqls) { sqlstr = Regex.Replace(sqlstr, replace_sql, "", RegexOptions.IgnoreCase); } HttpContext.Current.Request.Cookies[getsqlkey].Value = sqlstr; } } } catch (Exception ex) { Console.WriteLine(ex.Message); } }} 
