An Auditor’s Checklist for Securing WordPress Backends on OVH

OVH WordPress Backend: An Auditor’s Security Checklist

This document outlines a rigorous checklist for auditing the security posture of WordPress backends hosted on OVH infrastructure. It targets security engineers and compliance officers, focusing on actionable steps and specific configurations relevant to the OVH environment.

1. Server-Level Hardening (OVH Dedicated/VPS)

Assuming a dedicated server or VPS environment on OVH, the initial security layer is the operating system and its associated services. We’ll focus on common Linux distributions like Ubuntu or Debian.

1.1. SSH Access Control

Restrict SSH access to authorized personnel and implement strong authentication mechanisms. Disable root login and password authentication.

1.1.1. Disable Root Login

Edit the SSH daemon configuration file:

sudo nano /etc/ssh/sshd_config

Locate or add the following line and ensure it’s set to ‘no’:

PermitRootLogin no

1.1.2. Disable Password Authentication

In the same sshd_config file, set PasswordAuthentication to no. This enforces the use of SSH keys.

PasswordAuthentication no

After making these changes, restart the SSH service:

sudo systemctl restart sshd

1.2. Firewall Configuration (UFW Example)

Implement a host-based firewall to allow only necessary ports. UFW (Uncomplicated Firewall) is a common choice on Ubuntu.

1.2.1. Default Policies

Deny all incoming traffic by default and allow all outgoing traffic.

sudo ufw default deny incoming
sudo ufw default allow outgoing

1.2.2. Allow Essential Ports

Allow SSH (port 22), HTTP (port 80), and HTTPS (port 443). If using a custom SSH port, adjust accordingly.

sudo ufw allow ssh
sudo ufw allow http
sudo ufw allow https

1.2.3. Enable Firewall

Enable UFW and check its status.

sudo ufw enable
sudo ufw status verbose

1.3. Intrusion Detection/Prevention System (IDS/IPS)

Deploy and configure an IDS/IPS like Fail2ban to protect against brute-force attacks and suspicious activity.

1.3.1. Install Fail2ban

sudo apt update
sudo apt install fail2ban

1.3.2. Configure SSH Protection

Create a local jail configuration to override defaults. This example sets a ban time of 1 hour and a find time of 10 minutes with 3 failed attempts.

sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local

[sshd]
enabled = true
port = ssh
filter = sshd
logpath = /var/log/auth.log
maxretry = 3
findtime = 10m
bantime = 1h

Restart Fail2ban to apply changes:

sudo systemctl restart fail2ban

2. Web Server Configuration (Nginx Example)

Secure the web server serving WordPress. Nginx is a common and performant choice. This section assumes Nginx is installed and configured for WordPress.

2.1. TLS/SSL Configuration

Ensure all traffic is served over HTTPS. Use strong cipher suites and up-to-date TLS versions.

2.1.1. Nginx Server Block (Virtual Host)

Example Nginx configuration for a WordPress site, enforcing HTTPS and using recommended SSL parameters.

server {
    listen 80;
    server_name yourdomain.com www.yourdomain.com;
    return 301 https://$host$request_uri; # Redirect HTTP to HTTPS
}

server {
    listen 443 ssl http2;
    server_name yourdomain.com www.yourdomain.com;

    ssl_certificate /etc/letsencrypt/live/yourdomain.com/fullchain.pem; # Path to your SSL certificate
    ssl_certificate_key /etc/letsencrypt/live/yourdomain.com/privkey.pem; # Path to your SSL private key

    # Recommended SSL settings for strong security
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers on;
    ssl_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384';
    ssl_session_cache shared:SSL:10m;
    ssl_session_timeout 10m;
    ssl_session_tickets off;
    ssl_stapling on;
    ssl_stapling_verify on;
    resolver 8.8.8.8 8.8.4.4 valid=300s; # Use public DNS resolvers
    resolver_timeout 5s;

    # HSTS Header (optional, but recommended for production)
    # add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;

    root /var/www/yourdomain.com/html; # Path to your WordPress installation
    index index.php index.html index.htm;

    location / {
        try_files $uri $uri/ /index.php?$args;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php/php7.4-fpm.sock; # Adjust PHP version as needed
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }

    # Deny access to sensitive files
    location ~ /\.ht {
        deny all;
    }

    location = /favicon.ico { log_not_found off; access_log off; }
    location = /robots.txt { log_not_found off; access_log off; allow all; }

    # Prevent direct access to wp-config.php and .htaccess
    location ~* wp-config\.php { deny all; }
    location ~* \.(htaccess|htpasswd)$ { deny all; }

    # Caching for static assets (optional, but good practice)
    location ~* \.(css|js|jpg|jpeg|png|gif|ico|svg|webp)$ {
        expires 30d;
        add_header Cache-Control "public, no-transform";
    }
}

2.2. Request Filtering and Security Headers

Implement measures to block common web attacks and enhance browser security.

2.2.1. Block Common Exploits

Add rules to block requests containing suspicious patterns, such as SQL injection attempts or directory traversal.

location ~* /(?:wp-config\.php|xmlrpc\.php|wp-load\.php|wp-settings\.php|wp-cron\.php|upgrade\.php|install\.php) {
    deny all;
}

location ~* \.(?:bak|config|sql|fla|psd|ini|log|sh|inc|swp|dist|po|pot|mo|tl?|php[345]?|phtml) {
    deny all;
}

# Block common exploit patterns
if ($request_uri ~* "(?:etc/passwd|etc/shadow|~|\.\./|\.\.)") {
    return 403;
}

# Block access to .git, .svn, .hg directories
location ~ /\.git {
    deny all;
}
location ~ /\.svn {
    deny all;
}
location ~ /\.hg {
    deny all;
}

2.2.2. Security Headers

Add security headers to mitigate various attacks like XSS and clickjacking.

add_header X-Frame-Options "SAMEORIGIN";
add_header X-Content-Type-Options "nosniff";
add_header X-XSS-Protection "1; mode=block";
add_header Referrer-Policy "strict-origin-when-cross-origin";
# add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline'; object-src 'none'; style-src 'self' 'unsafe-inline'; img-src 'self' data:;"; # CSP is complex and requires careful tuning

After modifying Nginx configuration, test and reload the service:

sudo nginx -t
sudo systemctl reload nginx

3. PHP Configuration and Security

PHP is the engine behind WordPress. Securing its configuration is paramount.

3.1. PHP-FPM Configuration

Ensure PHP-FPM runs with minimal privileges and is configured securely.

3.1.1. User and Group

Edit the PHP-FPM pool configuration file (e.g., /etc/php/7.4/fpm/pool.d/www.conf). Set the user and group to a non-root, dedicated user for the web server (e.g., www-data).

user = www-data
group = www-data

3.1.2. Disable Dangerous Functions

Restrict the execution of potentially harmful PHP functions. This is a critical security measure.

disable_functions = exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source,pcntl_exec,pcntl_fork,pcntl_wait,pcntl_signal,pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait3,pcntl_wait4,pcntl_signal_dispatch,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,pcntl_strerror,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