Wildcard SSL certificate

  certbot certonly --manual -d "*.costan.ro" -d "costan.ro"

The above tool spits out a DNS challenge that we need to set as a DNS TXT record.

It depends on your DNS provider but usually is as simple as adding a new record.

  grep acme /etc/nsd/zones/costan.ro

_acme-challenge                       IN  TXT     "PDFYVU1v3Jlo6Yeo50-LHiokC8PwNeZl_-FCz13CKPs"

Check using local DNS server first (mind @ns.costan.ro local DNS server at the end)

  dig +short TXT _acme-challenge.costan.ro @ns.costan.ro

PDFYVU1v3Jlo6Yeo50-LHiokC8PwNeZl_-FCz13CKPs

Wait for DNS propagation and check using public (or default) DNS server. This "wait" part is important otherwise LetsEncrypt won't be able to resolve the DNS challenge and SSL generation process will fail.

  dig +short TXT _acme-challenge.costan.ro @8.8.8.8

PDFYVU1v3Jlo6Yeo50-LHiokC8PwNeZl_-FCz13CKPs

Once the DNS TXT change is propagated press "ENTER" and certbot tool will generate all certificate files.

  certbot certificates

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Found the following certs:
  Certificate Name: costan.ro
    Serial Number: 4f6208230dcfb39f339295c19a5eb7781fa
    Key Type: ECDSA
    Domains: *.costan.ro
    Expiry Date: 2023-03-19 12:40:17+00:00 (VALID: 89 days)
    Certificate Path: /etc/letsencrypt/live/costan.ro/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/costan.ro/privkey.pem
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Change configuration files for all public services (Postfix, Dovecot, Nsd, etc) and point to newly generated fullchain.pem and privkey.pem files.

  postconf -n | grep -E "smtpd_tls_.*_file"

smtpd_tls_cert_file = /etc/letsencrypt/live/costan.ro/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/costan.ro/privkey.pem

  doveconf ssl_cert ssl_key

ssl_cert = </etc/letsencrypt/live/costan.ro/fullchain.pem
ssl_key = </etc/letsencrypt/live/costan.ro/privkey.pem

And last, check installed SSL cert using an SSLlabs online checker or openssl tool.

  openssl s_client -connect www.costan.ro:443

Basic config files with a few cmd line settings.

  cat /etc/letsencrypt/cli.ini

key-type = ecdsa
email = letsencrypt@costan.ro
authenticator = manual
agree-tos = true

This script will update _acme-challenge in DNS config, sign and reload the zone.

  cat /etc/letsencrypt/renewal-hooks/auth.sh

#!/usr/bin/env sh

echo CERTBOT_DOMAIN=$CERTBOT_DOMAIN
echo CERTBOT_VALIDATION=$CERTBOT_VALIDATION
echo CERTBOT_REMAINING_CHALLENGES=$CERTBOT_REMAINING_CHALLENGES
echo CERTBOT_ALL_DOMAINS=$CERTBOT_ALL_DOMAINS

echo Sed: replace _acme_challenge in /etc/nsd/zones/$CERTBOT_DOMAIN ...:
sed -Ei "s/_acme-challenge(.+)\"(.+)\"/_acme-challenge\1\"$CERTBOT_VALIDATION\"/" /etc/nsd/zones/$CERTBOT_DOMAIN

echo NSD: sign/reload $CERTBOT_DOMAIN zone...
cd /etc/nsd/zones/
ldns-signzone -n -p -e 20240316174119 costan.ro Kcostan.ro.+008+03304 Kcostan.ro.+008+19957
nsd-control reconfig
nsd-control reload $CERTBOT_DOMAIN

echo Wait for DNS propagation...
sleep 15s

echo "DONE."

And finally the magic command.

  certbot renew --manual-auth=/etc/letsencrypt/renewal-hooks/auth.sh -v

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Processing /etc/letsencrypt/renewal/costan.ro.conf
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Certificate is due for renewal, auto-renewing...
Plugins selected: Authenticator manual, Installer None
Renewing an existing certificate for *.costan.ro
Performing the following challenges:
dns-01 challenge for costan.ro
Running manual-auth-hook command: /etc/letsencrypt/renewal-hooks/auth.sh
Hook '--manual-auth-hook' for costan.ro ran with output:
CERTBOT_DOMAIN=costan.ro
CERTBOT_VALIDATION=uY5-sXNpcCtIQoVmA7jy-kIg4-ipseBLjjOzyoTQzpI
CERTBOT_REMAINING_CHALLENGES=0
CERTBOT_ALL_DOMAINS=costan.ro
Sed: replace _acme_challenge in /etc/nsd/zones/costan.ro ...:
NSD: sign/reload costan.ro zone...
reconfig start, read /etc/nsd/nsd.conf
ok
ok
Wait for DNS propagation...
DONE.
Waiting for verification...
Cleaning up challenges

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Congratulations, all renewals succeeded:
/etc/letsencrypt/live/costan.ro/fullchain.pem (success)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  certbot certificates

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Found the following certs:
  Certificate Name: costan.ro
    Serial Number: 3fc9af33d62a240238dc4c1fb3a3dc616e6
    Key Type: ECDSA
    Domains: *.costan.ro
    Expiry Date: 2023-06-14 10:13:39+00:00 (VALID: 89 days)
    Certificate Path: /etc/letsencrypt/live/costan.ro/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/costan.ro/privkey.pem
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -