Merge branch 'ext-2' into 'master'

Buster Compat and Improved TLS Settings

Dovecot updated some TLS parameters in their config file. This adds the new parameters in a backward compatible manner.

Prompted by that move, I also changed dovecot and postfix to a preset-based configuration of TLS. The default preset is `previous`, that should get you a equivalent configuration as before, regardless of being on stretch or buster (minus OpenSSL changes). Also, there are presets `modern`, `intermediate`, `old` directly from the new <https://ssl-config.mozilla.org>. But beware, at least dovecot currently errors on TLSv1.3-only `modern` although OpenSSL should be able to handle it. The preset **overrides** all manual configuration, so you should upgrade your custom variables.

Beware, that there are two **open bugs** on Debian's dovecot package which may impact your setup:
- [928492: doveadm errors on listing PAM users, because of a glibc change](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=928492)
- [930919: dsync no longer syncs Sieve scripts](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=930919)

For both bugs there is a patch on the dovecot repository that is already merged. But none made it into Debian yet.

See merge request !3

dovecot/defaults/main.yml

@@ -14,9 +14,10 @@ dovecot_max_uid: 0
 dovecot_tls_cert: /etc/ssl/private/fullchain.pem
 dovecot_tls_key: /etc/ssl/private/privkey.pem
 dovecot_tls_ca_dir: /etc/ssl/certs
-dovecot_tls_ciphers: "{{ tls_ciphers }}"
-dovecot_tls_dh_length: 4096
-dovecot_tls_protocols: 'TLSv1.1 TLSv1.2 !SSLv3'
+
+# possible values: modern, intermediate, old, previous
+# see also: https://ssl-config.mozilla.org/
+dovecot_tls_configuration: 'previous'
 
 dovecot_dsync: false
 dovecot_dsync_tls: false

dovecot/files/ffdhe2048.txt

+-----BEGIN DH PARAMETERS-----
+MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
++8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
+87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7
+YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
+7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
+ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
+-----END DH PARAMETERS-----
\ No newline at end of file

dovecot/files/ffdhe4096.txt

+-----BEGIN DH PARAMETERS-----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=
+-----END DH PARAMETERS-----
\ No newline at end of file

dovecot/tasks/main.yml

 ---
 
+- name: "include tls config vars (preset: {{ dovecot_tls_configuration }})"
+  include_vars:
+    file: "tls-{{ dovecot_tls_configuration }}.yml"
+  tags:
+    - dovecot
+    - mail
+
 - name: ensure all required dovecot packages are installed
   apt:
     name:
@@ -36,6 +43,20 @@
     - dovecot
     - mail
 
+- name: ensure dh params are available
+  copy:
+    src: "{{ dovecot_tls_dh_file }}"
+    dest: /etc/dovecot/dh.pem
+    owner: root
+    group: root
+    mode: '0644'
+  when: dovecot_tls_dh_file is string
+  notify:
+    - restart dovecot
+  tags:
+    - dovecot
+    - mail
+
 - name: ensure there is a folder for global sieve scripts
   file:
     dest: /var/lib/dovecot/sieve.d

dovecot/templates/conf.d/10-ssl.conf.j2

@@ -42,18 +42,39 @@ ssl_client_ca_dir = {{ dovecot_tls_ca_dir }}
 # auth_ssl_username_from_cert=yes.
 #ssl_cert_username_field = commonName
 
+{% if ansible_distribution_major_version|int < 10 %}
 # DH parameters length to use.
+{% if dovecot_tls_dh_length %}
 ssl_dh_parameters_length = {{ dovecot_tls_dh_length }}
+{% else %}
+#ssl_dh_parameters_length =
+{% endif %}
+{% else %}
+# DH parameters to use.
+{% if dovecot_tls_dh_file %}
+ssl_dh = </etc/dovecot/dh.pem
+{% else %}
+#ssl_dh =
+{% endif %}
+{% endif %}
 
+{% if ansible_distribution_major_version|int < 10 %}
 # SSL protocols to use
 ssl_protocols = {{ dovecot_tls_protocols }}
+{% else %}
+# Minimum TLS version to use
+ssl_min_protocol = {{ dovecot_tls_min_protocol }}
+{% endif %}
 
 # SSL ciphers to use
-#ssl_cipher_list = HIGH:!LOW:!SSLv2:!EXP:!aNULL:!MD5:!RC4:!SHA1
+{% if dovecot_tls_ciphers %}
 ssl_cipher_list = {{ dovecot_tls_ciphers }}
+{% else %}
+#ssl_cipher_list =
+{% endif %}
 
 # Prefer the server's order of ciphers over client's.
-ssl_prefer_server_ciphers = yes
+ssl_prefer_server_ciphers = {{ 'yes' if dovecot_tls_prefer_server_ciphers else 'no' }}
 
 # SSL crypto device to use, for valid values run "openssl engine"
 #ssl_crypto_device =

dovecot/vars/tls-intermediate.yml

+---
+
+dovecot_tls_protocols: 'TLSv1.2 TLSv1.3'
+dovecot_tls_min_protocol: 'TLSv1.2'
+dovecot_tls_ciphers: 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384'
+dovecot_tls_dh_length: 4096 # 2048
+dovecot_tls_dh_file: ffdhe4096.txt # ffdhe2048.txt
+dovecot_tls_prefer_server_ciphers: false

dovecot/vars/tls-modern.yml

+---
+
+dovecot_tls_protocols: 'TLSv1.3'
+dovecot_tls_min_protocol: 'TLSv1.3'
+dovecot_tls_ciphers: null
+dovecot_tls_dh_length: null
+dovecot_tls_dh_file: null
+dovecot_tls_prefer_server_ciphers: false

dovecot/vars/tls-old.yml

+---
+
+dovecot_tls_protocols: 'TLSv1 TLSv1.1 TLSv1.2 !SSLv3'
+dovecot_tls_min_protocol: 'TLSv1'
+dovecot_tls_ciphers: 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA'
+dovecot_tls_dh_length: 2048 # 1024
+dovecot_tls_dh_file: ffdhe2048.txt # openssl dhparam 1024 > ffdhe1024.txt
+dovecot_tls_prefer_server_ciphers: true

dovecot/vars/tls-previous.yml

+---
+
+dovecot_tls_protocols: 'TLSv1.1 TLSv1.2 !SSLv3'
+dovecot_tls_min_protocol: 'TLSv1.1'
+dovecot_tls_ciphers: "{{ tls_ciphers }}"
+dovecot_tls_dh_length: 4096
+dovecot_tls_dh_file: ffdhe4096.txt # ffdhe2048.txt
+dovecot_tls_prefer_server_ciphers: true

postfix/defaults/main.yml

@@ -6,8 +6,10 @@ postfix_virtual_domains: []
 
 postfix_tls_cert: /etc/ssl/private/fullchain.pem
 postfix_tls_key: /etc/ssl/private/privkey.pem
-postfix_tls_ciphers: "{{ tls_ciphers }}"
-postfix_tls_protocols: '!SSLv2 !SSLv3'
+
+# possible values: modern, intermediate, old, previous
+# see also: https://ssl-config.mozilla.org/
+postfix_tls_configuration: 'previous'
 
 postfix_prefer_lmtp: false
 postfix_enable_memcached: false

postfix/files/ffdhe2048.txt

+-----BEGIN DH PARAMETERS-----
+MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
++8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
+87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7
+YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
+7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
+ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
+-----END DH PARAMETERS-----
\ No newline at end of file

postfix/files/ffdhe4096.txt

+-----BEGIN DH PARAMETERS-----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=
+-----END DH PARAMETERS-----
\ No newline at end of file

postfix/tasks/main.yml

 ---
 
+- name: "include tls config vars (preset: {{ postfix_tls_configuration }})"
+  include_vars:
+    file: "tls-{{ postfix_tls_configuration }}.yml"
+  tags:
+    - postfix
+    - mail
+
 - name: ensure all required postfix packages are installed
   apt:
     name:
@@ -35,6 +42,20 @@
     - postfix
     - mail
 
+- name: ensure dh params are available
+  copy:
+    src: "{{ postfix_tls_dh_file }}"
+    dest: /etc/postfix/dh.pem
+    owner: root
+    group: root
+    mode: '0644'
+  when: postfix_tls_dh_file is string
+  notify:
+    - restart postfix
+  tags:
+    - postfix
+    - mail
+
 - name: ensure memcached config is present
   template:
     src: memcached.conf.j2

postfix/templates/main.cf.j2

@@ -38,16 +38,32 @@ smtpd_relay_restrictions =
 	defer_unauth_destination
 
 smtpd_use_tls = yes
+smtpd_tls_security_level = may
 smtpd_tls_auth_only = yes
 smtpd_tls_cert_file = {{ postfix_tls_cert }}
 smtpd_tls_key_file = {{ postfix_tls_key }}
-smtpd_tls_eecdh_grade = ultra
-smtpd_tls_mandatory_ciphers = high
-smtpd_tls_mandatory_protocols = {{ postfix_tls_protocols }}
-smtpd_tls_protocols = {{ postfix_tls_protocols }}
 smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
 smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
-tls_high_cipherlist = {{ postfix_tls_ciphers }}
+smtpd_tls_protocols = {{ postfix_tls_protocols }}
+smtpd_tls_mandatory_protocols = {{ postfix_tls_protocols }}
+{% if postfix_tls_mandatory_ciphers %}
+smtpd_tls_mandatory_ciphers = {{ postfix_tls_mandatory_ciphers }}
+{% endif %}
+{% if postfix_tls_preempt_cipherlist %}
+tls_preempt_cipherlist = {{ 'yes' if postfix_tls_preempt_cipherlist else 'no' }}
+{% endif %}
+{% if postfix_tls_eecdh_grade %}
+smtpd_tls_eecdh_grade = {{ postfix_tls_eecdh_grade }}
+{% endif %}
+{% if postfix_tls_high_cipherlist %}
+tls_high_cipherlist = {{ postfix_tls_high_cipherlist }}
+{% endif %}
+{% if postfix_tls_medium_cipherlist %}
+tls_medium_cipherlist = {{ postfix_tls_medium_cipherlist }}
+{% endif %}
+{% if postfix_tls_dh_file %}
+smtpd_tls_dh1024_param_file = /etc/postfix/dh.pem
+{% endif %}
 
 alias_maps = cdb:/etc/aliases
 alias_database = cdb:/etc/aliases

postfix/vars/tls-intermediate.yml

+---
+
+postfix_tls_protocols: '!SSLv2, !SSLv3, !TLSv1, !TLSv1.1'
+postfix_tls_mandatory_ciphers: medium
+postfix_tls_preempt_cipherlist: false
+postfix_tls_eecdh_grade: null
+postfix_tls_high_cipherlist: null
+postfix_tls_dh_file: ffdhe2048.txt # ffdhe4096.txt
+postfix_tls_medium_cipherlist: 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384'

postfix/vars/tls-modern.yml

+---
+
+postfix_tls_protocols: '!SSLv2, !SSLv3, !TLSv1, !TLSv1.1, !TLSv1.2'
+postfix_tls_mandatory_ciphers: null
+postfix_tls_preempt_cipherlist: false
+postfix_tls_eecdh_grade: null
+postfix_tls_high_cipherlist: null
+postfix_tls_medium_cipherlist: null
+postfix_tls_dh_file: null

postfix/vars/tls-old.yml

+---
+
+postfix_tls_protocols: '!SSLv2, !SSLv3'
+postfix_tls_mandatory_ciphers: medium
+postfix_tls_preempt_cipherlist: true
+postfix_tls_eecdh_grade: null
+postfix_tls_high_cipherlist: null
+postfix_tls_dh_file: ffdhe2048.txt # ffdhe4096.txt
+postfix_tls_medium_cipherlist: 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA'

postfix/vars/tls-previous.yml

+---
+
+postfix_tls_protocols: '!SSLv2 !SSLv3'
+postfix_tls_mandatory_ciphers: high
+postfix_tls_preempt_cipherlist: null
+postfix_tls_eecdh_grade: ultra
+postfix_tls_high_cipherlist: "{{ tls_ciphers }}"
+postfix_tls_medium_cipherlist: null
+postfix_tls_dh_file: null