PHP login verification vulnerability revealed: Can you log in to your account with an incorrect password?

PHP login verification is a very important link in website development. It determines whether the user has the right to access the website by checking whether the account number and password entered by the user match the information stored in the database. . However, sometimes programmers make some common mistakes when writing login verification functionality, leading to security holes in the website. This article will reveal a common PHP login verification vulnerability, that is, the wrong password can actually log in to the account, and provide specific code examples for analysis and repair.

1. Principle of the vulnerability

In some simple login verification logic, the programmer may only check whether the password entered by the user is consistent with the password stored in the database, without considering whether the password is entered incorrectly. Condition. This leads to a serious vulnerability, where users can enter the wrong password and still successfully log into their account.

2. Specific code example

The following is a simple PHP code example to demonstrate how this vulnerability occurs:

<?php

// 模拟数据库中的用户信息
$users = [
    'admin' => 'password123'
];

// 用户提交的表单数据
$username = $_POST['username'];
$password = $_POST['password'];

// 验证用户身份
if (isset($users[$username]) && $password === $users[$username]) {
    echo '登录成功！';
} else {
    echo '用户名或密码错误！';
}

?>

In the above code, when the user When entering an incorrect password, the program does not have any limit on the number of incorrect passwords or error prompts, allowing users to finally successfully log in to their account by trying different passwords.

3. Vulnerability Repair

To fix this vulnerability, we need to perform appropriate processing when verifying user passwords do not match, such as limiting the number of password errors or adding a verification code function. The following is an example of the code after the repair:

<?php

// 模拟数据库中的用户信息
$users = [
    'admin' => 'password123'
];

// 用户提交的表单数据
$username = $_POST['username'];
$password = $_POST['password'];

// 设定密码错误次数限制
$loginAttempts = 3;

// 验证用户身份
if (isset($users[$username])) {
    if ($password === $users[$username]) {
        echo '登录成功！';
    } else {
        if ($_SESSION['login_attempts'] >= $loginAttempts) {
            echo '密码错误次数过多，请稍后再试！';
        } else {
            $_SESSION['login_attempts']++;
            echo '用户名或密码错误！';
        }
    }
} else {
    echo '用户名或密码错误！';
}

?>

In the code after the repair, we have increased the limit on the number of incorrect passwords and temporarily prohibited users from logging in after the number of incorrect passwords reaches a certain number to improve the security of the website. .

4. Conclusion

Through the analysis of this article, we revealed a common PHP login verification vulnerability and provided specific code examples for demonstration and repair. In actual development, programmers should be wary of such simple but dangerous vulnerabilities and strengthen the verification and processing of user input data to ensure the security of the website.

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