Add ability to enable unattended upgrades

This commit adds the ability to enable automatic package upgrades via
openstack-ansible-security.  To enable, add the following variable to
your /etc/openstack_deploy/user_variables.yml file:

unattended_upgrades_enabled: true

To have the unattended upgrades system send e-mail notifications
when packages need updating or errors are encountered, add the
following to user_variables.yml:

unattended_upgrades_notifications: true

As many organisations do not subscribe to auto updates, this
functionality will remain disabled by default.

Note that the first iteration of this change does not allow deep
customisation of unatteded-upgrades.  This means that as it stands
only trusty-security (or $distro-security) updates will be applied.

Closes-Bug: #1568075

Change-Id: I22ba1a02acfbe2befb601af6a4099d53d988d856

defaults/main.yml

@@ -306,3 +306,7 @@ sudoers_remove_authenticate: no                   # V-58901
 #
 # V-38651 - System default umask for bash must be 077
 #umask_bash: 077                                  # V-38651
+
+## Unattended upgrades (APT) configuration
+unattended_upgrades_enabled: false
+unattended_upgrades_notifications: false

doc/source/developer-notes/V-38481.rst

@@ -1,10 +1,18 @@
 **Exception**
 
-Operating system patching is left up to the deployer to configure based on
-their business requirements and toleration for risk. Enabling automated
-updates in Ubuntu can be done with changes to the apt configuration.
+Operating system patching policies vary from organization to organization and
+are typically established based on business requirements and risk tolerance.
 
-Ubuntu's documentation on `automatic updates`_ covers a few options for
-configuring apt.
+If desired, automatic updates (using the ``unattended-upgrades`` package)
+can be enabled via openstack-ansible-security by setting the following
+variable to ``true``:
 
-.. _automatic updates: https://help.ubuntu.com/lts/serverguide/automatic-updates.html
+.. code-block:: yaml
+
+    unattended_upgrades: true
+
+Note that this will only apply updates made available to the distro-security
+(eg. trusty-security) repositories.
+
+**Deployers are urged to fully understand the impact of enabling automatic
+update before making the change.**

files/20auto-upgrades

@@ -0,0 +1,2 @@
+APT::Periodic::Update-Package-Lists "1";
+APT::Periodic::Unattended-Upgrade "1";

tasks/apt.yml

@@ -60,3 +60,36 @@
     - auth
     - cat1
     - V-38462
+
+- name: Install unattended-upgrades package (for V-38481)
+  apt:
+    name: unattended-upgrades
+    state: present
+  when: unattended_upgrades_enabled | bool
+  tags:
+    - apt
+    - cat2
+    - V-38481
+
+- name: V-38481 - System security patches and updates must be installed and up-to-date
+  copy:
+    src: 20auto-upgrades
+    dest: /etc/apt/apt.conf.d/20auto-upgrades
+  when: unattended_upgrades_enabled | bool
+  tags:
+    - apt
+    - cat2
+    - V-38481
+
+- name: Enable unattended upgrades notifications (for V-38481)
+  lineinfile:
+    dest: /etc/apt/apt.conf.d/50unattended-upgrades
+    regexp: '^(\/\/)?Unattended-Upgrade::Mail "root";'
+    line: 'Unattended-Upgrade::Mail "root";'
+  when:
+    - unattended_upgrades_enabled | bool
+    - unattended_upgrades_notifications | bool
+  tags:
+    - apt
+    - cat2
+    - V-38481

tests/test.yml

@@ -19,5 +19,28 @@
     - name: Ensure apt cache is updated before testing
       apt:
         update_cache: yes
+  post_tasks:
+    - name: Stat 20auto-upgrades file
+      stat:
+        path: /etc/apt/apt.conf.d/20auto-upgrades
+      register: auto_upgrades_file
+    - name: Slurp contents of 50unattended-upgrades file
+      slurp:
+        src: /etc/apt/apt.conf.d/50unattended-upgrades
+      register: unattended_upgrades_file_encoded
+    - name: Decode slurp'd 50-unattended-upgrades file
+      set_fact:
+        unattended_upgrades_file: "{{ unattended_upgrades_file_encoded.content | b64decode }}"
+    - name: Ensure auto updates has been enabled
+      assert:
+        that:
+          - auto_upgrades_file.stat.exists
+    - name: Ensure that auto update notifications has been enabled
+      assert:
+        that:
+          - "'\nUnattended-Upgrade::Mail \"root\";\n' in unattended_upgrades_file"
   roles:
     - role: "{{ rolename }}"
+  vars:
+    unattended_upgrades_enabled: true
+    unattended_upgrades_notifications: true