====== ACME Integration ======

<WRAP round info>
**Complexity:** Medium \\
**Duration:** 1-2 hours setup \\
**Prerequisite:** DNS/HTTP challenge access
</WRAP>

Integration of the ACME protocol (RFC 8555) for automatic certificate renewal with post-quantum support.

----

===== Architecture =====

<mermaid>
sequenceDiagram
    participant Client as ACME Client
    participant CA as ACME CA
    participant DNS as DNS/HTTP Server
    participant App as Application

    Client->>CA: 1. Create account
    Client->>CA: 2. Create order (CSR)
    CA->>Client: 3. Challenge (DNS-01/HTTP-01)
    Client->>DNS: 4. Fulfill challenge
    CA->>DNS: 5. Validate challenge
    CA->>Client: 6. Issue certificate
    Client->>App: 7. Deploy certificate
    Client->>App: 8. Reload service
</mermaid>

----

===== Certbot Installation =====

<code bash>
# Debian/Ubuntu
apt update && apt install certbot python3-certbot-nginx

# RHEL/CentOS
dnf install certbot python3-certbot-nginx

# With DNS plugin (Cloudflare)
apt install python3-certbot-dns-cloudflare
</code>

----

===== HTTP-01 Challenge =====

**For publicly accessible web servers:**

<code bash>
# Nginx
certbot --nginx -d example.com -d www.example.com

# Apache
certbot --apache -d example.com -d www.example.com

# Standalone (port 80 free)
certbot certonly --standalone -d example.com

# Webroot (existing server)
certbot certonly --webroot -w /var/www/html -d example.com
</code>

**Auto-Renewal Cron:**

<code bash>
# Automatically activated during certbot installation
# Check manually:
systemctl status certbot.timer

# Manual test
certbot renew --dry-run
</code>

----

===== DNS-01 Challenge =====

**For internal servers or wildcards:**

==== Cloudflare ====

<code ini>
# /etc/letsencrypt/cloudflare.ini
dns_cloudflare_api_token = YOUR_API_TOKEN
</code>

<code bash>
chmod 600 /etc/letsencrypt/cloudflare.ini

certbot certonly \
    --dns-cloudflare \
    --dns-cloudflare-credentials /etc/letsencrypt/cloudflare.ini \
    -d example.com \
    -d "*.example.com"
</code>

==== Route53 (AWS) ====

<code bash>
# AWS credentials in ~/.aws/credentials
certbot certonly \
    --dns-route53 \
    -d example.com \
    -d "*.example.com"
</code>

==== Azure DNS ====

<code bash>
# With certbot-dns-azure plugin
pip install certbot-dns-azure

certbot certonly \
    --authenticator dns-azure \
    --dns-azure-credentials /etc/letsencrypt/azure.ini \
    -d example.com
</code>

----

===== Deployment Hooks =====

Hooks are executed after successful renewal.

==== Nginx Reload ====

<code bash>
# /etc/letsencrypt/renewal-hooks/deploy/reload-nginx.sh
#!/bin/bash
systemctl reload nginx
echo "$(date): Nginx reloaded" >> /var/log/certbot-deploy.log
</code>

<code bash>
chmod +x /etc/letsencrypt/renewal-hooks/deploy/reload-nginx.sh
</code>

==== Apache Reload ====

<code bash>
# /etc/letsencrypt/renewal-hooks/deploy/reload-apache.sh
#!/bin/bash
systemctl reload apache2
</code>

==== Docker Container ====

<code bash>
# /etc/letsencrypt/renewal-hooks/deploy/docker-reload.sh
#!/bin/bash
docker exec nginx nginx -s reload
# or
docker-compose restart nginx
</code>

==== Notification ====

<code bash>
# /etc/letsencrypt/renewal-hooks/post/notify.sh
#!/bin/bash
DOMAINS=$(echo $RENEWED_DOMAINS | tr ' ' '\n')
echo "Renewed: $DOMAINS" | mail -s "Certificate renewed" admin@example.com
</code>

----

===== Private ACME CA (Step-CA) =====

For internal PKI with ACME support:

<code bash>
# Install Step-CA
wget https://github.com/smallstep/certificates/releases/download/v0.25.0/step-ca_0.25.0_amd64.deb
dpkg -i step-ca_0.25.0_amd64.deb

# Initialize CA
step ca init --name="Internal CA" --dns=ca.internal.example.com --address=:443
</code>

**Add ACME Provisioner:**

<code bash>
step ca provisioner add acme --type ACME
</code>

**Certbot with private CA:**

<code bash>
certbot certonly \
    --server https://ca.internal.example.com/acme/acme/directory \
    --standalone \
    -d internal-server.example.com
</code>

----

===== Post-Quantum Note =====

<WRAP round important>
**Status 2024:** ACME protocol and Let's Encrypt do not yet support PQ signatures.
</WRAP>

**Hybrid Strategy:**

<code bash>
# 1. ACME certificate for TLS handshake (ECDSA)
certbot certonly --nginx -d example.com

# 2. Additional PQ certificate for hybrid mode
# (parallel via own PKI with WvdS)
</code>

<code csharp>
// C#: Create hybrid certificate in parallel
using var ecdsa = ECDsa.Create(ECCurve.NamedCurves.nistP384);
var request = new CertificateRequest(
    "CN=example.com", ecdsa, HashAlgorithmName.SHA384);

// With PQ extension for future-proof clients
var cert = request.CreateSelfSigned(
    DateTimeOffset.UtcNow,
    DateTimeOffset.UtcNow.AddDays(90),
    CryptoMode.Hybrid);
</code>

----

===== Monitoring =====

<code bash>
# Certbot logs
tail -f /var/log/letsencrypt/letsencrypt.log

# Check certificate expiry
certbot certificates

# Prometheus Exporter (cert-exporter)
# Monitors all certificates for expiry
</code>

----

===== Troubleshooting =====

| Problem | Cause | Solution |
|---------|-------|----------|
| ''Challenge failed'' | Port 80/443 blocked | Check firewall |
| ''DNS propagation'' | DNS cache | Wait (up to 60 min) or reduce TTL |
| ''Rate limit exceeded'' | Too many requests | Use staging server |
| ''unauthorized'' | Domain validation failed | Check DNS records |

<code bash>
# Staging server for tests (no rate limits)
certbot certonly --staging --nginx -d test.example.com

# Debug mode
certbot certonly --nginx -d example.com --debug
</code>

----

===== Checklist =====

| # | Checkpoint | Done |
|---|------------|------|
| 1 | DNS/HTTP challenge configured | |
| 2 | Certbot installed and tested | |
| 3 | Auto-renewal activated (timer) | |
| 4 | Deploy hook configured | |
| 5 | Monitoring set up | |
| 6 | Notification on error | |

----

===== Related Documentation =====

  * [[.:scheduled-renewal|Scheduled Renewal]] - Alternative without ACME
  * [[..:monitoring:ablauf-monitoring|Expiry Monitoring]] - Monitor certificates
  * [[en:int:pqcrypt:szenarien:tls:start|TLS/mTLS]] - Server configuration

----

<< [[.:start|<- Automation]] | [[.:cicd-code-signing|-> CI/CD Code Signing]] >>

----
//Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional//

{{tag>acme letsencrypt certbot automation operator}}