sql注入登录表单错误

Question

我正在编写有关如何使用旧的PHP代码进行sql注入的教程。 我有这个代码，我正在测试它，但我有一个错误，说：

致命错误：在非对象上调用成员函数fetch_assoc（）

这是旧代码：

<?php
$host="localhost"; // Host name 
$username="root"; // Mysql username 
$password="root"; // Mysql password 
$db_name="graphic_db"; // Database name 
$tbl_name="login"; // Table name 
//if(!session_is_registered(myusername)){
//header("location:index.html");
  $con=mysqli_connect($host,$username,$password,$db_name);



if(isset($_POST['login_submit'])){

    if($_POST['username'] != '' && $_POST['password']!=''){
        if(!isset($_SESSION)) 
    { 
        session_start();
        //session_register('username'); 
    } 

        $result = mysqli_query($con, "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
        while($row  = $result->fetch_assoc($result) ){
        if(is_array($row)) {
            $_SESSION["username"] = $row[$_POST["username"]];
            $_SESSION['username'] = $_POST["username"];

            header("Location:home.php");
            } 
            else {
            $message = "Invalid Username or Password!";

            }

        }
        }

        }

?>

Answer 1

您在代码中混合了Object oriented style和Procedural style 。仅使用一种样式

面向对象的风格

$result = $mysqli->query( "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
 while($row  = $result->fetch_assoc() ){

在程序风格

 $result = mysqli_query($con, "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
 while($row  = mysqli_fetch_assoc($result) ){

阅读http://php.net/manual/en/mysqli-result.fetch-assoc.php

Answer 2

试试这段代码$row=mysqli_fetch_array($result,MYSQLI_ASSOC);

Answer 3

    $host="localhost"; // Host name 
    $username="root"; // Mysql username 
    $password="root"; // Mysql password 
    $db_name="graphic_db"; // Database name 
    $tbl_name="login"; // Table name 
    session_start();
    $mysqli = new mysqli($host, $username, $password, $db_name);

    if(isset($_POST['login_submit'])){
        $stmt = $mysqli->prepare("SELECT * FROM login WHERE email=? AND  password=? ");
        $email = $_POST['username'];
        $password = md5($_POST['password']);
        $stmt->bind_param('ss', $email, $password);
        $stmt->execute();
        $stmt->bind_result($email, $password);
        $stmt->store_result();

        if($stmt->num_rows == 1)  //To check if the row exists
        {
            while($stmt->fetch()) //fetching the contents of the row
            {
                $_SESSION['Logged'] = 1;
                   $_SESSION['Email'] = $email;
                   header('Location: home.php');
                   exit();
            }

        }
        else 
        {
            echo "Wrong Username or Password!";
        }
        $stmt->close();
        $stmt->free_result();
    }

使用准备好的查询为您的SQL注入代码。 这是最好的做法。

准备语句对于SQL注入非常有用，因为稍后使用不同协议传输的参数值无需正确转义。 如果原始语句模板不是从外部输入派生的，则不能进行SQL注入。