Enable SPF checking on lists

This requires an external program and only works on Debian hosts.

Newer versions of exim (4.91) have SPF functionality built-in, but
they are not yet available to us.

Change-Id: Idfe6bfa5a404b61c8761aa1bfa2212e4b4e32be9

.zuul.yaml

@@ -447,6 +447,26 @@
       - playbooks/group_vars/letsencrypt.yaml
       - playbooks/roles/letsencrypt.*
 
+- job:
+    name: system-config-run-lists
+    parent: system-config-run
+    description: |
+      Run the playbook for a list server.
+    nodeset:
+      nodes:
+        - name: bridge.openstack.org
+          label: ubuntu-bionic
+        - name: lists.openstack.org
+          label: ubuntu-xenial
+    files:
+      - .zuul.yaml
+      - modules/openstack_project/manifests/lists.pp
+      - playbooks/host_vars/lists.openstack.org.yaml
+      - roles/exim
+    vars:
+      run_playbooks:
+        - playbooks/remote_puppet_else.yaml
+
 - job:
     name: system-config-run-nodepool
     parent: system-config-run
@@ -674,6 +694,7 @@
             voting: false
         - system-config-run-dns
         - system-config-run-eavesdrop
+        - system-config-run-lists
         - system-config-run-nodepool
         - system-config-run-mirror
         - system-config-run-docker-registry
@@ -700,6 +721,7 @@
         - system-config-run-base
         - system-config-run-dns
         - system-config-run-eavesdrop
+        - system-config-run-lists
         - system-config-run-nodepool
         - system-config-run-mirror
         - system-config-run-docker-registry

playbooks/host_vars/lists.openstack.org.yaml

@@ -1,5 +1,6 @@
 mm_domains: 'lists.openstack.org:lists.zuul-ci.org:lists.airshipit.org:lists.starlingx.io:lists.opendev.org'
 exim_local_domains: "@:{{ mm_domains }}"
+exim_enable_spf: true
 exim_aliases:
   root: "{{ ','.join(listadmins|default([])) }}"
   interop-wg: openstack-discuss

roles/exim/defaults/main.yaml

@@ -25,3 +25,4 @@ exim_routers:
   - system_aliases: '{{ exim_system_aliases_router }}'
   - localuser: '{{ exim_localuser_router }}'
 exim_transports: []
+exim_enable_spf: false

roles/exim/tasks/Debian.yaml

@@ -0,0 +1,10 @@
+- name: Install Exim
+  package:
+    state: present
+    name: '{{ package }}'
+
+- name: Install SPF tools
+  when: exim_enable_spf
+  package:
+    state: present
+    name: spf-tools-perl

roles/exim/templates/exim4.conf.j2

@@ -488,6 +488,51 @@ acl_check_rcpt:
   # require verify = csa
   #############################################################################
 
+  # Use spfquery to perform a pair of SPF checks (for details, see
+  # http://www.openspf.org/)
+  #
+  # This is quite costly in terms of DNS lookups (~6 lookups per mail).  Do not
+  # enable if that's an issue.  Also note that if you enable this, you must
+  # install "spf-tools-perl" which provides the spfquery command.
+  # Missing spf-tools-perl will trigger the "Unexpected error in
+  # SPF check" warning.
+  {% if exim_enable_spf %}
+  deny
+    message = [SPF] $sender_host_address is not allowed to send mail from \
+              ${if def:sender_address_domain {$sender_address_domain}{$sender_helo_name}}.  \
+              Please see \
+              http://www.openspf.org/Why?scope=${if def:sender_address_domain \
+              {mfrom}{helo}};identity=${if def:sender_address_domain \
+              {$sender_address}{$sender_helo_name}};ip=$sender_host_address
+    log_message = SPF check failed.
+    condition = ${run{/usr/bin/spfquery.mail-spf-perl --ip \
+                   ${quote:$sender_host_address} --identity \
+                   ${if def:sender_address_domain \
+                       {--scope mfrom  --identity ${quote:$sender_address}}\
+                       {--scope helo --identity ${quote:$sender_helo_name}}}}\
+                   {no}{${if eq {$runrc}{1}{yes}{no}}}}
+
+  defer
+    message = Temporary DNS error while checking SPF record.  Try again later.
+    condition = ${if eq {$runrc}{5}{yes}{no}}
+
+  warn
+    condition = ${if <={$runrc}{6}{yes}{no}}
+    add_header = Received-SPF: ${if eq {$runrc}{0}{pass}\
+                                {${if eq {$runrc}{2}{softfail}\
+                                 {${if eq {$runrc}{3}{neutral}\
+                                  {${if eq {$runrc}{4}{permerror}\
+                                   {${if eq {$runrc}{6}{none}{error}}}}}}}}}\
+                                } client-ip=$sender_host_address; \
+                                ${if def:sender_address_domain \
+                                   {envelope-from=${sender_address}; }{}}\
+                                helo=$sender_helo_name
+
+  warn
+    log_message = Unexpected error in SPF check.
+    condition = ${if >{$runrc}{6}{yes}{no}}
+  {% endif %}
+
   # At this point, the address has passed all the checks that have been
   # configured, so we accept it unconditionally.