Let’s Encrypt in CentOS 6 und CentOS 7 einrichten

Message

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Failed loading XML... 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Let’s Encrypt in CentOS 6 und CentOS 7 einrichten

Let’s Encrypt empfiehlt einige Clients, die mit CentOS kompatibel sind. Wir denken, dass CertBot von der non-profit Electronic Frontier Foundation eine sehr gute Wahl ist, wenn dieser richtig eingerichtet ist und beschreiben daher diesen.

System Update

Für eine korrekte Funktion benötigt CertBot viele Pakete. Daher führen wir zunächst ein Update aller Pakete aus:

yum -y update

Dann wird das EPEL (Extra Packages for Enterprise Linux) Repositrory installiert, um die aktuellsten Python Pakete für CertBot zu erhalten:

# yum -y install epel-release

Achtung: Wenn der Server individuell konfiguriert wurde, kann eine Update die Webseite beeinflussen. Wenn dies geschieht, sollte ein Serverexperte konsultiert werden.

CertBot von EFF holen

CertBot ist im CentOS 7 EPEL Repository verfügbar, unter CentOS 7 wird CertBot also installiert durch Eingabe von:

yum -y install python-certbot-apache

Unter CentOS 6 wird das Programm wie folgt heruntergeladen und ausführbar gemacht:

# wget https://dl.eff.org/certbot-auto
# chmod 755 certbot-auto

Apache mit CertBot konfigurieren

Unter CentOS 6 und 7 ist Apache der übliche Webserver. Wir beschreiben daher hier die Konfiguration mit diesem.

CertBot bietet ein Plugin um Apache zu konfigurieren. Zum Starten folgenden Befehl eingeben:

certbot --apache

CertBot listet dann alle Domains auf, die auf dem Webserver eingerichtet sind und fragt danach, für welche Domains SSL konfiguriert werden soll.

Domains auswählen mit Pfeiltasten und Leertaste

Die nächsten beiden Schritte fragen nach der Administrator Email-Adresse und nach Bestätigung der Lizenzbestimmungen. Danach wird gefragt, ob alle Zugriffe über HTTPS erfolgen sollen.

empfehlenswert ist die komplette Verschlüsselung

Eine komplette Verschlüsselung der ganzen Webseite ist immer vorzuziehen, da dies vor Fälschen der Inhalte und vielen webbasierten Attacken schützt. Wenn die Webseite allerdings hart kodierte Links enthält, also http://homepage.eu, resultiert daraus ein Zertifikat-Fehler - also alle Links auf https ändern.

Automatische Verlängerung konfigurieren

Let's Encrypt Zertifikate laufen nach 90 Tagen ab. Also sollte ein Cron Job eingerichtet werden, der diese alle 85 Tage verlängert. Davor sollte ein Testlauf (Dry Run) durchgeführt werden, um sicher zu gehen, dass alles funktioniert:

# certbot renew --dry-run

Wenn alles in Ordnung ist, folgenden Befehl in die Crontab (täglich) aufnehmen:

certbot renew --quiet

Mögliche Probleme

CertBot macht einiges einfacher, aber es kann zu Problemen bei der Einrichtung kommen, wie z.B.

Apache Konfiguration blockiert Zugriff auf versteckte Verzeichnisse
Der Let's Encrypt Client schreibt in ein Verzeichnis names '.well-known' um die Identität des Client zu verifizieren. Also sicherstellen, dass die Apache Konfiguration den Zugriff auf versteckte Verzeichnisse erlaubt.
Domain weisst nicht auf den Server
Sicherstellen, dass die Domains (und Subdomains) auf den Server verweisen.
Webseite mit Passwort-Schutz
Den Passwortschutz aufheben, falls einer besteht.
Paket-Konflikte bei unterschiedlichen Repositories
Beim Update des Servers oder der Nutzung verschiedener Pakete können Versions-Konflikte auftreten. Sorgfälltig kontrollieren, dass keine Anwendungen beeinträchtigt werden - insbesondere wenn Python Web Applikationen eingesetzt werden.