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public class JDBCDemo3 {public static void demo3_1(){boolean flag=login("aaa' OR ' ","1651561"); //若已知用户名,用这种方式便可不用知道密码就可登陆成功if (flag){System.out.println("登陆成功");}else{System.out.println("登陆失败");}}public static boolean login(String username,String password){Connection conn=null;Statement stat=null;ResultSet rs=null;boolean flag=false;try {conn=JDBCUtils.getConnection();String sql="SELECT * FROM user WHERE username='"+username+"'AND password='"+password+"'"; //此处是SQL注入漏洞的关键,因为是字符串的拼接,会使查询语句变为:SELECT * FROM user WHERE username='aaa' OR '' AND password='1651561',此查询语句是可得到结果集的,便出现此漏洞stat=conn.createStatement();rs=stat.executeQuery(sql);if(rs.next()){flag=true;}else{flag=false;}} catch (SQLException e) {e.printStackTrace();}return flag;} |
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public static void demo3_1(){boolean flag=login1("aaa' OR ' ","1651561");if (flag){System.out.println("登陆成功");}else{System.out.println("登陆失败");}}public static boolean login1(String username,String password){Connection conn=null;PreparedStatement pstat=null;ResultSet rs=null;boolean flag=false;try {conn=JDBCUtils.getConnection();String sql="SELECT * FROM user WHERE username=? AND password=?"; //使用?代替参数,预先设置好sql格式,就算在输入sql关键字也不会被sql识别pstat=conn.prepareStatement(sql);pstat.setString(1,username); //设置问号的值pstat.setString(2,password);rs=pstat.executeQuery();if(rs.next()){flag=true;}else{flag=false;}} catch (SQLException e) {e.printStackTrace();}return flag;}} |
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