ACL configuration based on user behavior in Nginx reverse proxy

Nginx is a high-performance web server and reverse proxy server software. It is an open source software that can run on a variety of operating systems, such as Linux, Windows, FreeBSD, etc. Nginx is commonly used in reverse proxy, load balancing, HTTP caching, security authentication and other scenarios. In a reverse proxy scenario, Nginx can forward user requests to multiple back-end servers to improve system performance and reliability. This article will introduce how to configure ACL based on user behavior in Nginx reverse proxy.

ACL is the abbreviation of Access Control List, which is a technology used for access control. In the network, ACL technology is widely used in firewalls, routers, proxy servers and other equipment. ACL can restrict or allow user access based on different conditions, such as IP address, port number, protocol type, etc. In the Nginx reverse proxy, ACL can limit or allow the forwarding of requests based on the user's request characteristics.

The ACL configuration syntax of Nginx is as follows:

location / {
    # allow或deny用于定义访问控制规则，如：
    allow ip; # 允许IP地址访问
    deny ip; # 禁止IP地址访问
    allow all; # 允许所有访问
    deny all; # 禁止所有访问
}

Among them, ip can be a single IP address, an IP address segment or an IP address in CIDR format, such as:

allow 192.168.1.1; # 允许单个IP地址访问
allow 192.168.0.0/16; # 允许IP地址段访问
allow 192.168.1.0/24; # 允许CIDR格式的IP地址访问

In addition to IP In addition to addresses, ACL also supports other conditions, such as HTTP request headers, request methods, request paths, etc. In the Nginx reverse proxy, the HTTP request header is particularly important because it can represent the user's behavioral characteristics.

In modern web applications, user behavior characteristics are becoming more and more complex, requiring more flexible and intelligent ACL configuration for access control. For example, we may need to limit or allow the forwarding of requests based on factors such as the user's login status, request frequency, request source, etc. In Nginx, we can implement ACL configuration based on user behavior in the following ways.

1. Based on request headers

In Nginx, we can use if statements to check HTTP request headers and execute allow or deny instructions as needed. For example, we can restrict access to specific browsers or operating systems by checking the User-Agent field in the request header. The sample configuration is as follows:

location / {
    if ($http_user_agent ~* MSIE) {
        deny all;
    }
    allow all;
}

The above configuration means that all users whose User-Agent contains "MSIE" are prohibited from accessing, and other users are allowed to access.

2. Based on Cookie

In modern web applications, users usually need to log in to access certain resources. In order to restrict access to non-logged-in users, we need to check the Cookie field in the request and execute the allow or deny directive as needed. For example, we can restrict access to non-logged-in users by checking the Cookie field in the request header. The sample configuration is as follows:

location /protected {
    if ($http_cookie !~* "access_token=.*") {
        return 401; # 请求未携带access_token
    }
    allow all;
}

The above configuration means that if the request does not carry the "access_token" field, a 401 error will be returned; otherwise, all users will be allowed to access.

3. Based on access frequency

In some scenarios, we need to limit or allow user access based on the user's access frequency. For example, in the API interface scenario, we can avoid DDoS attacks by checking the request frequency. In Nginx, we can use the limit_req directive to implement ACL configuration based on access frequency. The example configuration is as follows:

http {
    # 定义限制访问频率的配置
    limit_req_zone $binary_remote_addr zone=api:10m rate=10r/s;
    # 定义反向代理配置
    server {
        location /api/ {
            limit_req zone=api burst=20 nodelay;
            proxy_pass http://api.example.com/;
        }
    }
}

The above configuration indicates that each IP address can access the /api/ path up to 10 times per second, and 20 burst accesses are allowed. If the user's access frequency exceeds the limit, a 503 error will be returned.

4. Based on request source

In some scenarios, we need to restrict or allow user access based on the source IP address or domain name of the request. For example, in some security authentication scenarios, we can implement access control by checking the request source IP or domain name. In Nginx, we can use the geo directive to implement ACL configuration based on the request source. The sample configuration is as follows:

http {
    # 定义IP地址库文件
    geoip_country /usr/share/GeoIP/GeoIP.dat;
    # 定义反向代理配置
    server {
        location / {
            # 根据请求IP的国家代码进行访问控制
            if ($geoip_country_code != CN) {
                deny all;
            }
            proxy_pass http://proxy.example.com/;
        }
    }
}

The above configuration means that if the country where the requested IP is located is not China, access is prohibited. If you need to control access based on domain name, you can use the geoip_host directive.

In short, Nginx's ACL configuration is very flexible and powerful, and can implement access control based on user behavior according to different needs. When using ACL, you need to be careful not to abuse if statements, because if statements will affect the performance and stability of Nginx. It is recommended to use Nginx's built-in instructions and variables as much as possible to implement ACL configuration. At the same time, performance testing and optimization also need to be carried out based on actual conditions to ensure that ACL configuration has as little impact on system performance as possible.

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