Understand the CAS authentication method and its implementation ideas in PHP

Understand the CAS authentication method in PHP and its implementation ideas

CAS (Central Authentication Service) is a commonly used single sign-on authentication protocol that centralizes user authentication and session information management On a central server, shared login status between multiple application systems is implemented. In PHP development, the CAS authentication method can quickly implement single sign-on and permission management functions. This article will introduce the CAS authentication method in detail and provide PHP code examples to help readers understand and practice it in depth.

1. Basic principles of CAS authentication method

1. Client requests login: The user clicks the login button in the client application system to initiate a login request to the CAS server.
2. CAS server verifies user identity: After the CAS server receives the login request, it will verify the user's identity information, such as user name and password. If the verification is successful, the CAS server will generate a globally unique ticket (TGT, Ticket Granting Ticket).
3. The client redirects to the CAS server: After the CAS server generates the TGT, it will return it to the client and initiate a 302 redirect, guiding the user to another address, which is the login of the CAS client application system address.
4. The client requests the CAS server again: After the client application system receives the 302 redirect, it will initiate a request to the CAS server again. At this time, the request will carry the previously obtained TGT.
5. The CAS server verifies the TGT and generates ST: After the CAS server receives the client request, it will verify the validity of the TGT. If the TGT is valid, the CAS server will generate a service ticket (ST, Service Ticket).
6. The CAS server returns ST to the client: The CAS server returns the generated ST to the client.
7. The client carries ST to request the service system: after the client application system receives ST, it will carry it in the request parameters and initiate a request to the service system.
8. The service system verifies ST and generates login status: After receiving the client request, the service system verifies the validity of ST to the CAS server. If ST is valid, the service system will generate the user's login status and complete the user login.

The above is the basic process of CAS authentication method. Next, we will demonstrate the implementation of the CAS authentication method and related details through PHP code examples.

2. PHP implementation of CAS authentication method

1. CAS server-side implementation

(1) Configure CAS server-side authentication information, including user name and Password etc.

(2) Provide CAS server-side verification interface for verifying user identity information and verifying the validity of TGT and ST. The interface code example is as follows:

// 验证用户身份信息
function validateUser($username, $password) {
  // 验证逻辑代码
}

// 验证TGT有效性
function validateTGT($tgt) {
  // 验证逻辑代码
}

// 验证ST有效性
function validateST($st) {
  // 验证逻辑代码
}

(3) Generate TGT and ST, as well as the processing logic returned to the client.

2. Realization of CAS client application system

(1) Implementation of user login page. When the user clicks the login button, it will jump to the login address of the CAS server and carry the service address of the client application system.

(2) Parse the ST returned by the CAS server and send a request to the service system. After the client application system receives the ST, it needs to parse the ST and carry it in the request parameters, for example:

$service_ticket = $_GET['st'];
// 发起请求
$request_url = "http://service.system.com/?st=" . $service_ticket;
$response = file_get_contents($request_url);

(3) ST verification implementation in the service system. After receiving the client request, the service system needs to verify the validity of the ST with the CAS server. Verification logic code example:

$url = "http://cas-server.com/validateST";
$data = array('st' => $service_ticket);
$options = array(
  'http' => array(
    'header'  => "Content-type: application/x-www-form-urlencoded
",
    'method'  => 'POST',
    'content' => http_build_query($data),
  ),
);
$context  = stream_context_create($options);
$result = file_get_contents($url, false, $context);
if ($result == "valid") {
  // ST有效，生成登录状态
} else {
  // ST无效，跳转到登录页面
}

The above are the PHP implementation steps and code examples of the CAS authentication method. By understanding the basic principles of the CAS authentication method and the specific PHP implementation, we can quickly implement single sign-on and permission management functions, improving user experience and system security.

To sum up, this article introduces in detail the principle and implementation ideas of the CAS authentication method in PHP, and gives code examples. It is hoped that readers can better understand and apply the CAS authentication method through the guidance and practice of this article, and provide a reference for development practice.

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