PHP data filtering: preventing cookie hijacking and tampering

PHP Data Filtering: Preventing Cookie Hijacking and Tampering

In Internet application development, Cookie is a commonly used technology used to transfer data between the client and the server. However, due to the characteristics of cookies, they are vulnerable to attacks by hackers, such as cookie hijacking and tampering. In order to protect the security of user data, we need to filter and verify incoming cookie data. This article will introduce how to use PHP to filter cookie data to prevent cookie hijacking and tampering.

1. Using the HTTP Only flag

HTTP Only is a commonly used security flag used to specify whether a cookie can be accessed by scripts. Setting the HTTP Only attribute of the cookie to true can prevent cross-site scripting attacks. The following is sample code for setting the HTTP Only attribute of a cookie:

setcookie('cookie_name', 'cookie_value', time() + 3600, '/', 'example.com', true, true);

2. Using the Secure flag

Secure is another commonly used security flag that is used to specify whether a cookie is passed only by Encrypted connection transmission. Setting the Cookie's Secure attribute to true prevents cookies from being transmitted over non-secure connections. The following is sample code for setting the Secure attribute of a cookie:

setcookie('cookie_name', 'cookie_value', time() + 3600, '/', 'example.com', true, true, true);

3. Filter illegal characters

Hackers may try to hijack or tamper with cookies by passing illegal characters. To prevent this from happening, we can use PHP's filter function to filter the input cookie data. The following is a sample code for filtering illegal characters:

$cookie_value = filter_input(INPUT_COOKIE, 'cookie_name', FILTER_SANITIZE_STRING);

4. Use encryption algorithm

Using encryption algorithm to encrypt Cookie data can increase the security of Cookie. You can use PHP encryption functions, such as md5, sha1, etc. The following is a sample code that uses md5 to encrypt cookie data:

$cookie_value = md5($_COOKIE['cookie_name']);

5. Verify signature

Verifying the signature of a cookie ensures that the cookie has not been tampered with. The HMAC encryption algorithm can be used to generate and verify cookie signatures. The following is a sample code that uses the HMAC algorithm to verify Cookie signatures:

$secret_key = 'your_secret_key';
$cookie_value = $_COOKIE['cookie_name'];

$exploded_cookie = explode('.', $cookie_value);
$cookie_data = $exploded_cookie[0];
$cookie_signature = $exploded_cookie[1];

$generated_signature = hash_hmac('sha256', $cookie_data, $secret_key);

if ($generated_signature === $cookie_signature) {
    // 签名验证成功
} else {
    // 签名验证失败
}

Summary:

By using the above method, we can strengthen the filtering and verification of Cookie data, thereby preventing Cookie hijacking and tampering happened. When writing Internet applications, ensuring proper filtering and validation of cookie data is an important step in protecting user data. Hope the above sample code is helpful to you.

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