HTTP request sniffing defense method in Nginx reverse proxy

With the development of the Internet, Web servers and applications have become more and more complex, and security attacks have gradually increased. Nginx is one of the most widely used tools in Web servers and load balancing technology. Nginx's reverse proxy mechanism can make it a reliable application server, but it is also a widely attacked target. In this article, we will explore how to defend against HTTP request sniffing attacks in Nginx reverse proxy.

What is an HTTP request sniffing attack?

HTTP request sniffing attack is a common network attack method. The attacker intercepts HTTP requests in network data packets and analyzes and processes the data to obtain sensitive information of the target site. In other words, the attacker intercepts the HTTP request sent by the client to the server and analyzes the headers and parameters. By analyzing this information, the attacker can obtain the actual IP address of the server, infer the actual application server, and obtain important sensitive data that may include user login credentials, business data, session identification, etc. HTTP request sniffing attacks can also be used to identify vulnerabilities in web applications and attack these vulnerabilities.

HTTP request sniffing attack defense method in Nginx reverse proxy

1. Enable HTTPS protocol

HTTPS protocol is an encrypted communication protocol that can effectively prevent HTTP requests Sniffing attack. Enabling the HTTPS protocol requires the installation of a valid SSL certificate. Currently, the more popular SSL certificates include free Let's Encrypt and paid Symantec, DigiCert, etc. Enabling the HTTPS protocol in the Nginx reverse proxy can be achieved through the following configuration:

server {
    listen 443;
    server_name example.com;
    ssl on;
    ssl_certificate /path/to/cert.crt;
    ssl_certificate_key /path/to/cert.key;

    location / {
        proxy_pass http://backend;
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

The above configuration can achieve an attack by hijacking the SSL handshake process and forcing the client to downgrade to the unencrypted HTTP protocol. This attack method is called For SSL stripping attacks, you need to enable SSL certificate binding in the configuration of the Nginx server:

server {
    listen 80;
    server_name example.com;
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl;
    server_name example.com;
    ssl_certificate /path/to/cert.crt;
    ssl_certificate_key /path/to/cert.key;

    if ($ssl_protocol = "") {
        return 403;
    }

    location / {
        proxy_pass http://backend;
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

2. Set HTTP request headers

Setting some HTTP request headers in the Nginx server can effectively prevent HTTP Request sniffing attack. Setting the HTTP request header requires modifying the Nginx server configuration file. You can usually add the following settings in the http block of the Nginx configuration file:

add_header X-Frame-Options SAMEORIGIN;
add_header X-XSS-Protection "1; mode=block";
add_header X-Content-Type-Options nosniff;

The above configuration can make the browser's CSP policy more secure and will prompt the browser not to Parsing the response as HTML should be downloaded, but that doesn't make it impossible for an attacker to sniff the request.

3. Use Firewall and Web Application Firewall

Firewall and Web Application Firewall can inspect and filter requests to detect and prevent HTTP request sniffing attacks. Firewalls can enable rules for greater security, for example:

• Only allow clients to use specific IP addresses or network access services
• Block HTTP request headers with different Or timed out requests

4. Use IP/Port binding

Using IP/Port binding is a simple way to prevent the load due to sniffing attacks Balance failure. In the Nginx server load balancing configuration, use the IP address to limit client access, and you can also restrict the client from accessing specific ports on the Nginx server. For example:

upstream backend {
    ip_hash;
    server backend1.example.com:80;
    server backend2.example.com:80;
}

server {
    listen 192.0.2.1:80;
    server_name example.com;
    location / {
        proxy_pass http://backend;
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

The above configuration can make the client only pass 192.0 .2.1:80 port to access the Nginx server, thus effectively preventing sniffing attacks.

Summary

HTTP request sniffing attack in Nginx reverse proxy is a common attack method, which can be achieved by enabling HTTPS protocol, setting HTTP request header, using Firewall and Web Application Firewall firewall And IP/Port binding and other methods for defense. Although the above methods can improve the security of applications, in actual applications, more appropriate defense methods need to be selected based on the actual situation of the application to ensure the security and stability of the application.

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