From a7cd31c6886d7d8b89e35117edd9de313355325e 2020-05-18 16:45:24
From: Branko Majic <branko@majic.rs>
Date: 2020-05-18 16:45:24
Subject: [PATCH] MAR-153: Use custom Diffie-Helman parameters for SMTP server in the mail_server role.

---

diff --git a/roles/mail_server/molecule/default/tests/test_default.py b/roles/mail_server/molecule/default/tests/test_default.py
index c7774ed477724fe5f8f291a5d4a869539ebc9488..f3a2e71b5faedc4bcfdf22bd6a9f710aaa08f8e9 100644
--- a/roles/mail_server/molecule/default/tests/test_default.py
+++ b/roles/mail_server/molecule/default/tests/test_default.py
@@ -355,3 +355,44 @@ def test_firewall_configuration_file(host):
         assert config.user == 'root'
         assert config.group == 'root'
         assert config.mode == 0o640
+
+
+def test_smtp_server_dh_parameter_file(host):
+    """
+    Tests if the Diffie-Helman parameter file has been generated
+    correctly.
+    """
+
+    hostname = host.run('hostname').stdout.strip()
+    dhparam_file_path = '/etc/ssl/private/%s_smtp.dh.pem' % hostname
+
+    with host.sudo():
+        dhparam_file = host.file(dhparam_file_path)
+        assert dhparam_file.is_file
+        assert dhparam_file.user == 'root'
+        assert dhparam_file.group == 'root'
+        assert dhparam_file.mode == 0o640
+
+        dhparam_info = host.run("openssl dhparam -noout -text -in %s", dhparam_file_path)
+
+        assert "DH Parameters: (2048 bit)" in dhparam_info.stdout
+
+
+def test_smtp_server_uses_correct_dh_parameters(host):
+    """
+    Tests if the SMTP server uses the generated Diffie-Helman parameter.
+    """
+
+    hostname = host.run('hostname').stdout.strip()
+
+    with host.sudo():
+        expected_dhparam = host.file('/etc/ssl/private/%s_smtp.dh.pem' % hostname).content_string.rstrip()
+
+    connection = host.run("gnutls-cli --no-ca-verification --starttls-proto=smtp --port 25 --priority 'NONE:+VERS-TLS1.2:+CTYPE-X509:+COMP-NULL:+SIGN-RSA-SHA384:+DHE-RSA:+SHA384:+AEAD:+AES-256-GCM' --verbose localhost")
+
+    output = connection.stdout
+    begin_marker = "-----BEGIN DH PARAMETERS-----"
+    end_marker = "-----END DH PARAMETERS-----"
+    used_dhparam = output[output.find(begin_marker):output.find(end_marker) + len(end_marker)]
+
+    assert used_dhparam == expected_dhparam
diff --git a/roles/mail_server/tasks/main.yml b/roles/mail_server/tasks/main.yml
index 3d01ef702fd067a5a530ef264146e365bd2ec95f..5858871cbebeb0f76eea8af77f0dbea58ac8300f 100644
--- a/roles/mail_server/tasks/main.yml
+++ b/roles/mail_server/tasks/main.yml
@@ -59,6 +59,16 @@
   notify:
     - Restart Postfix
 
+- name: Generate the SMTP server Diffie-Helman parameter
+  openssl_dhparam:
+    owner: root
+    group: root
+    mode: 0640
+    path: "/etc/ssl/private/{{ ansible_fqdn }}_smtp.dh.pem"
+    size: 2048
+  notify:
+    - Restart Postfix
+
 - name: Deploy IMAP TLS private key
   copy:
     dest: "/etc/ssl/private/{{ ansible_fqdn }}_imap.key"
diff --git a/roles/mail_server/templates/main.cf.j2 b/roles/mail_server/templates/main.cf.j2
index ad273cd8dd2de92d92cce6ce81a19bf093391f71..b3ab8923ce9e29cd6743e52ae5d5a328290233ca 100644
--- a/roles/mail_server/templates/main.cf.j2
+++ b/roles/mail_server/templates/main.cf.j2
@@ -54,6 +54,8 @@ smtpd_tls_security_level = may
 smtpd_tls_auth_only = yes
 smtpd_tls_cert_file = /etc/ssl/certs/{{ ansible_fqdn }}_smtp.pem
 smtpd_tls_key_file = /etc/ssl/private/{{ ansible_fqdn }}_smtp.key
+smtpd_tls_dh1024_param_file = /etc/ssl/private/{{ inventory_hostname }}_smtp.dh.pem
+smtpd_tls_dh512_param_file = /etc/ssl/private/{{ inventory_hostname }}_smtp.dh.pem
 smtpd_use_tls=yes
 smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
 smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache