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Chapter 7: Static Website Hosting (3 OSes × 2 Web Servers)

7.10 Combination 5 — CentOS Stream 9 + Nginx

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On CentOS the commands are the same as on Amazon Linux, but remember the two extra guards – the SELinux label and firewalld. Once you do both, CentOS is also very easy.

sudo yum install -y nginx
sudo service nginx start
sudo systemctl enable nginx

sudo tee /etc/nginx/conf.d/mysite.conf > /dev/null <<'EOF'
server {
    listen 80;
    listen [::]:80;
    server_name YOUR_SERVER_NAME;
    root /var/www/mysite;
    index index.html;
    location / {
        try_files $uri $uri/ =404;
    }
    error_page 404 /404.html;
}
EOF
sudo sed -i "s/YOUR_SERVER_NAME/$(curl -s https://checkip.amazonaws.com)/" /etc/nginx/conf.d/mysite.conf

# SELinux: give the files the web-content label
sudo restorecon -Rv /var/www/mysite
ls -Z /var/www/mysite            # should show httpd_sys_content_t

# firewalld: only if it is active
if systemctl is-active --quiet firewalld; then
  sudo firewall-cmd --permanent --add-service=http --add-service=https
  sudo firewall-cmd --reload
fi

sudo nginx -t && sudo service nginx reload
curl -s http://localhost -H "Host: $(curl -s https://checkip.amazonaws.com)" | head -5

SELinux and custom folders

/var/www/... automatically gets the correct label, but a folder elsewhere (e.g. /data/site or /home/ec2-user/site) does not. For such folders add a rule, then relabel: sudo semanage fcontext -a -t httpd_sys_content_t "/data/site(/.*)?" and sudo restorecon -Rv /data/site (the semanage command comes from package policycoreutils-python-utils). Files moved with mv keep their old label — always run restorecon after moving.

Ravindra Bagale's Tip

Many students switch SELinux off with setenforce 0 when they get 403, and then forget about it. Instead, run sudo restorecon -Rv /var/www/mysite and check the httpd_sys_content_t label with ls -Z. Turning SELinux off is like sending the security guard home.

Lab

Chala, CentOS var Combination 5 kara. Mag ls -Z /var/www/mysite madhe label bagha, getenforce ne Enforcing aahe ka te check kara, aani browser madhe site ughda.

Extended teaching notes

Why this lesson matters

Cloud security is mostly IAM, network exposure, logging and secure defaults. The shared responsibility model means the provider patches the metal; you patch what you configure.

  • No public databases or public admin panels.
  • Roles / OIDC instead of long-lived access keys.
  • CloudTrail / Activity Logs / Audit Logs on and retained.
  • S3/Blob/GCS: Block Public Access; encrypt; least privilege.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.