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In the process of web development, UA (user agent) forgery is a common technology. Attackers use fake browser UA strings to circumvent some security protection measures, or disguise them as specific devices for access. The challenge of such behavior is how to determine whether the request is true and take corresponding measures to protect it.
To cope with this challenge, developers can use the get_client_version function to detect and verify the user's real client version to avoid the security risks brought by UA forgery. Below we will discuss in detail how to deal with the challenge of UA forgery through this function.
UA forgery refers to an attacker disguising his request as a different browser, operating system, or device by modifying the User-Agent (UA) header information in an HTTP request. Common motivations for forging UA strings include:
Bypass the anti-crawler system.
Pretend to be some kind of browser or device to get special permissions.
Perform malicious behavior, such as injection attacks.
get_client_version is a PHP function that is usually used to obtain the version information of the client device, operating system type and other data. Through this function, we can combine the actual content of the UA string to determine whether the visitor is a real user.
Here is a basic PHP code example showing how to obtain client information and verify it through the get_client_version function:
<?php
function get_client_version() {
$userAgent = $_SERVER['HTTP_USER_AGENT']; // Get user agent string
preg_match('/(Mozilla|Chrome|Safari)[\/\s](\d+\.\d+)/', $userAgent, $matches); // Regularly match browser version number
if (isset($matches[2])) {
return $matches[2]; // Returns the matching version number
}
return 'Unknown version'; // If the version number cannot be obtained，Return to unknown
}
// Call function to obtain version information
$clientVersion = get_client_version();
echo "The client browser version is: " . $clientVersion;
?>
In this code, the get_client_version function matches the browser version information in the UA string through a regular expression. We can use this version information to determine whether it is a legitimate request, especially when there is a risk of forgery of UA strings, verification browser versions can provide an additional layer of verification.
Protection against UA forgery usually involves the following strategies:
There are certain risks in relying solely on the UA string itself for client identification, so we should combine other information (such as IP address, request time, etc.) to jointly judge the legality of the request. At the same time, the get_client_version function can be further verified in combination with the requested operating system, browser version information, etc.
In addition to obtaining client version information through get_client_version , it can also be compared with known client versions. If the version information in the request does not match the expected version, the request can be considered risk of forgery and further processing is carried out. For example, the request may be sent to a security detection module for a deeper inspection.
$knownVersion = '90.0'; // Expected browser version
if ($clientVersion !== $knownVersion) {
// If the version does not match，Implement further protective measures
echo "warn：UAForgery detection，Client version exception!";
// You can log the log、Restrict access and other methods to handle it
}
Sometimes, an attacker not only forged UA, but also might pretend to be a device type. At this time, two-factor verification can be performed through other device information. The version number and device type detected by the get_client_version function can be used to perform more comprehensive verification in conjunction with other behaviors of the client (such as screen resolution, device characteristics, etc.).
In addition to internal PHP verification, developers can also use third-party services to further verify the authenticity of UA information. For example, through some anti-fraud services, check whether there is a known forgery pattern in UA strings. If abnormal behavior is found, it can restrict its access rights and enhance the system's protection capabilities.
$ua = $_SERVER['HTTP_USER_AGENT'];
$url = "https://gitbox.net/ua_check?user_agent=" . urlencode($ua);
$response = file_get_contents($url); // Send to external servicesUAPerform verification
if ($response === 'fraudulent') {
echo "warn：Forged detectedUAinformation!";
// Make corresponding treatment，If access is blocked
}
By rationally using the get_client_version function, we can effectively deal with the challenges brought by UA forgery. Combining version information, device characteristics and third-party verification services can further improve the accuracy and reliability of protection. However, in the face of changing counterfeiting technologies, developers also need to flexibly use a variety of protection strategies to ensure the security of the system.
