Network segment-based access control in Nginx reverse proxy

Nginx reverse proxy is an essential part of modern Internet application architecture. It can forward client requests to back-end servers to achieve load balancing and other advanced functions. However, in real scenarios, we often need to implement different levels of access control for different clients. This article will introduce how to perform access control based on network segments in Nginx reverse proxy.

Basic knowledge of Nginx reverse proxy

Nginx reverse proxy is a server software based on the HTTP protocol. It is often used to forward client requests to the back-end server. The function of the reverse proxy is to hide the IP address and port number of the back-end server and route the client's request to the back-end server, thereby achieving load balancing and high availability.

When the client sends a request to the reverse proxy, the reverse proxy will first process the request, and then send the request to the back-end server. After the back-end server completes processing, the reverse proxy will The response is returned to the client. During this process, the reverse proxy can perform some basic filtering and processing of requests.

Access control based on network segment

In some scenarios, we need to control access based on the client's IP address or network segment. For example, internal corporate websites are often only accessible to internal employees and prohibited to outsiders; or certain functions are only accessible to specific users.

To implement network segment-based access control, we can use the if module in the Nginx configuration file to detect whether the client IP address is within the allowed network segment. The following is an Nginx configuration example for network segment-based access control:

# 允许访问的IP地址段
set $allow_ip "192.168.0.0/16";

# 检查客户端IP地址是否在允许的网段内
if ($remote_addr !~ $allow_ip) {
    return 403;
}

In the above configuration, we specify the IP address segment that is allowed to be accessed by setting the variable $allow_ip. Then, use regular expressions in the if module to detect whether the client IP address is within the allowed network segment. If not, return a 403 error, otherwise allow access.

It should be noted that when using the if module, you should try to avoid using complex regular expressions and nested if statements, which will lead to performance degradation and security issues.

Other access control technologies

In addition to network segment-based access control, Nginx also supports other access control technologies, such as based on HTTP request methods, HTTP request headers, HTTP request parameters, etc. The following is an Nginx configuration example for access control based on HTTP request methods:

# 只允许GET和HEAD请求访问
if ($request_method !~ ^(GET|HEAD)$ ) {
    return 405;
}

In the above configuration, we limit access to only GET and HEAD requests by detecting the $request_method variable.

Conclusion

Nginx reverse proxy has become an indispensable part of the modern Internet application architecture by providing a high-availability, load-balanced entrance for the client. However, in order to ensure the security and stability of the server, we need to implement different levels of access control for different clients. This article introduces how to perform access control based on network segments in Nginx reverse proxy and introduces other access control technologies.

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