feat: use daemon_name for OpenDKIM sign-verify decision instead of IP

On FreeBSD 127.0.0.2 is not assigned to any interface by default,
so 127.0.0.2 source address hack cannot be used to make OpenDKIM
verify the signature instead of signing.

This change sets InternalHosts to `-` so no IP addresses
make OpenDKIM sign the message. Instead of IP address,
OpenDKIM in the outgoing pipeline is explicitly told
to sign messages by setting `{daemon_name}` macro to `ORIGINATING`.

chatmaild/src/chatmaild/filtermail.py

@@ -307,12 +307,9 @@ class IncomingBeforeQueueHandler:
             return error
         log_info("re-injecting the mail that passed checks")
 
-        # the smtp daemon on reinject_port_incoming gives it to dkim milter
-        # which looks at source address to determine whether to verify or sign
         client = SMTPClient(
             "localhost",
             self.config.postfix_reinject_port_incoming,
-            source_address=("127.0.0.2", 0),
         )
         client.sendmail(
             envelope.mail_from, envelope.rcpt_tos, envelope.original_content

cmdeploy/src/cmdeploy/opendkim/final.lua

@@ -1,4 +1,5 @@
-if odkim.internal_ip(ctx) == 1 then
+mtaname = odkim.get_mtasymbol(ctx, "{daemon_name}")
+if mtaname == "ORIGINATING" then
 	-- Outgoing message will be signed,
 	-- no need to look for signatures.
 	return nil

cmdeploy/src/cmdeploy/opendkim/opendkim.conf

@@ -65,3 +65,9 @@ PidFile			/run/opendkim/opendkim.pid
 # The trust anchor enables DNSSEC. In Debian, the trust anchor file is provided
 # by the package dns-root-data.
 TrustAnchorFile		/usr/share/dns/root.key
+
+# Sign messages when `-o milter_macro_daemon_name=ORIGINATING` is set.
+MTA ORIGINATING
+
+# No hosts are treated as internal, ORIGINATING daemon name should be set explicitly.
+InternalHosts -

cmdeploy/src/cmdeploy/postfix/master.cf.j2

@@ -31,7 +31,6 @@ submission inet n       -       y       -       5000    smtpd
   -o smtpd_sender_restrictions=$mua_sender_restrictions
   -o smtpd_recipient_restrictions=
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
-  -o milter_macro_daemon_name=ORIGINATING
   -o smtpd_client_connection_count_limit=1000
   -o smtpd_proxy_filter=127.0.0.1:{{ config.filtermail_smtp_port }}
 smtps     inet  n       -       y       -       5000    smtpd
@@ -49,7 +48,6 @@ smtps     inet  n       -       y       -       5000    smtpd
   -o smtpd_recipient_restrictions=
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
   -o smtpd_client_connection_count_limit=1000
-  -o milter_macro_daemon_name=ORIGINATING
   -o smtpd_proxy_filter=127.0.0.1:{{ config.filtermail_smtp_port }}
 #628       inet  n       -       y       -       -       qmqpd
 pickup    unix  n       -       y       60      1       pickup
@@ -81,6 +79,7 @@ filter    unix -        n       n       -       -       lmtp
 # Local SMTP server for reinjecting outgoing filtered mail.
 127.0.0.1:{{ config.postfix_reinject_port }} inet  n       -       n       -       100      smtpd
   -o syslog_name=postfix/reinject
+  -o milter_macro_daemon_name=ORIGINATING
   -o smtpd_milters=unix:opendkim/opendkim.sock
   -o cleanup_service_name=authclean