email: setup: Find Let's Encrypt certificates

plinth/modules/email_server/audit/tls.py

@@ -2,11 +2,12 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
 import logging
+import os
 
 from plinth import actions
 
 from . import models
-from plinth.modules.email_server import postconf
+from plinth.modules.email_server import interproc, postconf
 
 # Mozilla Guideline v5.6, Postfix 1.17.7, OpenSSL 1.1.1d, intermediate
 # Generated 2021-08
@@ -52,6 +53,13 @@ postfix_config = {
     'tls_high_cipherlist': '$tls_medium_cipherlist',
 }
 
+dovecot_cert_config = '/etc/dovecot/conf.d/91-freedombox-ssl.conf'
+
+dovecot_cert_template = """# This file is managed by FreedomBox
+ssl_cert = <{cert}
+ssl_key = <{key}
+"""
+
 logger = logging.getLogger(__name__)
 
 
@@ -79,6 +87,50 @@ def repair_tls(diagnosis):
     postconf.set_many_unsafe(diagnosis.advice)
 
 
+def try_set_up_certificates():
+    cert_folder = find_cert_folder()
+    if not cert_folder:
+        logger.warning('Could not find a suitable TLS certificate')
+        return
+    logger.info('Using TLS certificate in %s', cert_folder)
+
+    cert = cert_folder + '/cert.pem'
+    key = cert_folder + '/privkey.pem'
+    write_postfix_cert_config(cert, key)
+    write_dovecot_cert_config(cert, key)
+
+
+def find_cert_folder() -> str:
+    directory = '/etc/letsencrypt/live'
+    domains_available = []
+    for item in os.listdir(directory):
+        if item[0] != '.' and os.path.isdir(directory + '/' + item):
+            domains_available.append(item)
+    domains_available.sort()
+
+    if len(domains_available) == 0:
+        return ''
+    if len(domains_available) == 1:
+        return directory + '/' + domains_available[0]
+    # XXX Cannot handle the case with multiple domains
+    if len(domains_available) > 1:
+        return ''
+
+
+def write_postfix_cert_config(cert, key):
+    postconf.set_many_unsafe({
+        'smtpd_tls_cert_file': cert,
+        'smtpd_tls_key_file': key
+    })
+
+
+def write_dovecot_cert_config(cert, key):
+    content = dovecot_cert_template.format(cert=cert, key=key)
+    with interproc.atomically_rewrite(dovecot_cert_config) as fd:
+        fd.write(content)
+
+
 def action_set_up():
     with postconf.mutex.lock_all():
         repair_tls(check_tls())
+        try_set_up_certificates()