Inhaltsverzeichnis

ACME Integration

ACME Integration

Complexity: Medium
Duration: 1-2 hours setup
Prerequisite: DNS/HTTP challenge access

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

Architecture

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

Certbot Installation

# 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

HTTP-01 Challenge

For publicly accessible web servers:

# 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

Auto-Renewal Cron:

# Automatically activated during certbot installation
# Check manually:
systemctl status certbot.timer
 
# Manual test
certbot renew --dry-run

DNS-01 Challenge

For internal servers or wildcards:

Cloudflare

# /etc/letsencrypt/cloudflare.ini
dns_cloudflare_api_token = YOUR_API_TOKEN

chmod 600 /etc/letsencrypt/cloudflare.ini
 
certbot certonly \
    --dns-cloudflare \
    --dns-cloudflare-credentials /etc/letsencrypt/cloudflare.ini \
    -d example.com \
    -d "*.example.com"

Route53 (AWS)

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

Azure DNS

# 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

Deployment Hooks

Hooks are executed after successful renewal.

Nginx Reload

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

chmod +x /etc/letsencrypt/renewal-hooks/deploy/reload-nginx.sh

Apache Reload

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

Docker Container

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

Notification

# /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

Private ACME CA (Step-CA)

For internal PKI with ACME support:

# 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

Add ACME Provisioner:

step ca provisioner add acme --type ACME

Certbot with private CA:

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

Post-Quantum Note

Status 2024: ACME protocol and Let's Encrypt do not yet support PQ signatures.

Hybrid Strategy:

# 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)

// 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);

Monitoring

# Certbot logs
tail -f /var/log/letsencrypt/letsencrypt.log
 
# Check certificate expiry
certbot certificates
 
# Prometheus Exporter (cert-exporter)
# Monitors all certificates for expiry

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

# Staging server for tests (no rate limits)
certbot certonly --staging --nginx -d test.example.com
 
# Debug mode
certbot certonly --nginx -d example.com --debug

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