Table of Contents
Nginx is a free, open-source, and widely used web server. It is essential to secure the Nginx web server to defend it from DDoS and other attacks, and ModSecurity can help.
ModSecurity is a free and open-source web application firewall used to protect web servers from external threats. It is used by many websites, cPanel, and other hosting control panels to protect their web applications and servers from SQL injection, cross-site scripting, and local file inclusion attack. Originally it was designed to secure only the Apache web servers. Now it can also work with the Nginx web server.
In this post, we will show you how to install ModSecurity with Nginx on Oracle Linux 8.
Step 1 – Install Required Dependencies
First, you will need to install some required dependencies needed to compile Nginx with ModSecurity. You can install all of them with the following command:
dnf install gcc-c++ flex bison yajl curl-devel curl zlib-devel pcre-devel autoconf automake git curl make libxml2-devel pkgconfig libtool httpd-devel redhat-rpm-config git wget openssl openssl-devel vim
Next, install other packages that are not available in Oracle Linux:
dnf install https://rpmfind.net/linux/centos/8-stream/PowerTools/x86_64/os/Packages/doxygen-1.8.14-12.el8.x86_64.rpm dnf install https://yum.oracle.com/repo/OracleLinux/OL8/codeready/builder/x86_64/getPackage/yajl-devel-2.1.0-10.el8.x86_64.rpm
Next, install the EPEL and Remi repositories using the following command:
dnf install epel-release https://rpms.remirepo.net/enterprise/remi-release-8.rpm -y
Next, install GeoIP using the following command:
dnf --enablerepo=remi install GeoIP-devel -y
Step 2 – Install ModSecurity On Oracle Linux 8
First, download the latest version of ModSecurity from the Git Hub repository using the following command:
git clone --depth 1 -b v3/master --single-branch https://github.com/SpiderLabs/ModSecurity
Once the download is completed, navigate to the ModSecurity directory and install other modules with the following command:
cd ModSecurity git submodule init git submodule update
Next, compile and install ModSecurity with the following command:
./build.sh ./configure make make install
Step 3 – Compile Nginx with LibModsecurity Support
In order to enable LibModsecurity support in Nginx, you will need to compile Nginx with support for LibModsecurity.
First, download the ModSecurity-nginx connector using the following command:
cd /root git clone https://github.com/SpiderLabs/ModSecurity-nginx.git
Next, download the latest stable version of Nginx with the following command:
wget http://nginx.org/download/nginx-1.19.10.tar.gz
Next, extract the downloaded file using the following command:
tar xzf nginx-1.19.10.tar.gz
Next, create an Nginx user with the following command:
useradd -r -M -s /sbin/nologin -d /usr/local/nginx nginx
Next, change the directory to the Nginx source and compile it using the following command:
cd nginx-1.19.10 ./configure --user=nginx --group=nginx --with-pcre-jit --with-debug --with-http_ssl_module --with-http_realip_module --add-module=/root/ModSecurity-nginx
Next, install it using the following command:
make make install
Next, copy a sample ModSecurity configuration file and Unicode mapping file with the following command:
cp /root/ModSecurity/modsecurity.conf-recommended /usr/local/nginx/conf/modsecurity.conf cp /root/ModSecurity/unicode.mapping /usr/local/nginx/conf/
Next, back up the Nginx configuration file:
cp /usr/local/nginx/conf/nginx.conf{,.bak}
Next, edit the Nginx configuration file with the following command:
nano /usr/local/nginx/conf/nginx.conf
Remove all lines and add the following lines:
user nginx;
worker_processes 1;
pid /run/nginx.pid;
events {
worker_connections 1024;
}
http {
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
server {
listen 80;
server_name nginx.example.com;
modsecurity on;
modsecurity_rules_file /usr/local/nginx/conf/modsecurity.conf;
access_log /var/log/nginx/access_kifarunix-demo.log;
error_log /var/log/nginx/error_kifarunix-demo.log;
location / {
root html;
index index.html index.htm;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root html;
}
}
}
Save and close the file, then create an Nginx log directory:
mkdir /var/log/nginx
Step 4 – Create a Systemd Service File for Nginx
Next, you will need to create a systemd service file to manage the Nginx service. You can create it using the following command:
nano /etc/systemd/system/nginx.service
Add the following lines:
[Unit] Description=The nginx HTTP and reverse proxy server After=network.target remote-fs.target nss-lookup.target [Service] Type=forking PIDFile=/run/nginx.pid ExecStartPre=/usr/bin/rm -f /run/nginx.pid ExecStartPre=/usr/sbin/nginx -t ExecStart=/usr/sbin/nginx ExecReload=/bin/kill -s HUP $MAINPID KillSignal=SIGQUIT TimeoutStopSec=5 KillMode=mixed PrivateTmp=true [Install] WantedBy=multi-user.target
Save and close the file, then create a symlink of Nginx binary using the following command:
ln -s /usr/local/nginx/sbin/nginx /usr/sbin/
Next, reload the systemd daemon to apply the changes:
systemctl daemon-reload
Next, start the Nginx service and enable it to start at system reboot:
systemctl enable --now nginx
You can check the status of Nginx with the following command:
systemctl status nginx
You will get the following output:
● nginx.service - The nginx HTTP and reverse proxy server
Loaded: loaded (/etc/systemd/system/nginx.service; enabled; vendor preset: disabled)
Active: active (running) since Wed 2022-06-29 12:22:20 EDT; 7s ago
Process: 52249 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS)
Process: 52247 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
Process: 52246 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS)
Main PID: 52251 (nginx)
Tasks: 2 (limit: 11409)
Memory: 3.6M
CGroup: /system.slice/nginx.service
├─52251 nginx: master process /usr/sbin/nginx
└─52252 nginx: worker process
Jun 29 12:22:20 oraclelinux8 systemd[1]: Starting The nginx HTTP and reverse proxy server...
Jun 29 12:22:20 oraclelinux8 nginx[52247]: nginx: the configuration file /usr/local/nginx/conf/nginx.conf syntax is ok
Jun 29 12:22:20 oraclelinux8 nginx[52247]: nginx: configuration file /usr/local/nginx/conf/nginx.conf test is successful
Jun 29 12:22:20 oraclelinux8 systemd[1]: nginx.service: Failed to parse PID from file /run/nginx.pid: Invalid argument
Jun 29 12:22:20 oraclelinux8 systemd[1]: Started The nginx HTTP and reverse proxy server.
Step 5 – Enable ModSecurity Rule
By default, ModSecurity has been configured for detection-only mode, so you must enable the ModSecurity rule in the modsecurity.conf file.
To enable it, run the following command:
sed -i 's/SecRuleEngine DetectionOnly/SecRuleEngine On/' /usr/local/nginx/conf/modsecurity.conf
Also enable the audit log with the following command:
sed -i 's#/var/log/modsec_audit.log#/var/log/nginx/modsec_audit.log#' /usr/local/nginx/conf/modsecurity.conf
Step 6 – Install OWASP ModSecurity Core Rule Set
OWASP provides generic attack detection rules for ModSecurity, so it is recommended to download and integrate with ModSecurity for better security.
git clone https://github.com/SpiderLabs/owasp-modsecurity-crs.git /usr/local/nginx/conf/owasp-crs
Next, rename the OWASP rule configuration file using the following command:
cp /usr/local/nginx/conf/owasp-crs/crs-setup.conf{.example,}
Next, define the OWASP rule in the ModSecurity configuration file:
echo -e "Include owasp-crs/crs-setup.conf\nInclude owasp-crs/rules/*.conf" >> /usr/local/nginx/conf/modsecurity.conf
Next, restart the Nginx service to apply the changes:
systemctl restart nginx
Step 7 – Verify ModSecurity
At this point, Nginx is installed and configured with ModSecurity support. Now, it’s time to test it.
Execute the code injection using the curl command:
curl localhost/index.html?exec=/bin/bash
If ModSecurity is working fine, you should get the “403 Forbidden” error as shown below:
<html> <head><title>403 Forbidden</title></head> <body> <center><h1>403 Forbidden</h1></center> <hr><center>nginx/1.19.10</center> </body> </html>
You can also verify the ModSecurity log for more information:
tail -100 /var/log/nginx/modsec_audit.log
You should see the following output:
ModSecurity: Warning. Matched "Operator `PmFromFile' with parameter `unix-shell.data' against variable `ARGS:exec' (Value: `/bin/bash' ) [file "/usr/local/nginx/conf/owasp-crs/rules/REQUEST-932-APPLICATION-ATTACK-RCE.conf"] [line "496"] [id "932160"] [rev ""] [msg "Remote Command Execution: Unix Shell Code Found"] [data "Matched Data: bin/bash found within ARGS:exec: /bin/bash"] [severity "2"] [ver "OWASP_CRS/3.2.0"] [maturity "0"] [accuracy "0"] [tag "application-multi"] [tag "language-shell"] [tag "platform-unix"] [tag "attack-rce"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/WEB_ATTACK/COMMAND_INJECTION"] [tag "WASCTC/WASC-31"] [tag "OWASP_TOP_10/A1"] [tag "PCI/6.5.2"] [hostname "127.0.0.1"] [uri "/index.html"] [unique_id "165651983136.006138"] [ref "o1,8v21,9t:urlDecodeUni,t:cmdLine,t:normalizePath,t:lowercase"] ModSecurity: Access denied with code 403 (phase 2). Matched "Operator `Ge' with parameter `5' against variable `TX:ANOMALY_SCORE' (Value: `5' ) [file "/usr/local/nginx/conf/owasp-crs/rules/REQUEST-949-BLOCKING-EVALUATION.conf"] [line "80"] [id "949110"] [rev ""] [msg "Inbound Anomaly Score Exceeded (Total Score: 5)"] [data ""] [severity "2"] [ver "OWASP_CRS/3.2.0"] [maturity "0"] [accuracy "0"] [tag "application-multi"] [tag "language-multi"] [tag "platform-multi"] [tag "attack-generic"] [hostname "127.0.0.1"] [uri "/index.html"] [unique_id "165651983136.006138"] [ref ""] ---cnJj4Dnx---I-- ---cnJj4Dnx---J-- ---cnJj4Dnx---Z--
Conclusion
In this guide, we learned how to install ModSecurity with Nginx on Oracle Linux 8. Your server is not fully protected with ModSecurity and it can able to protect from a wide range of attacks. Give it a try on your dedicated server from Atlantic.Net!
