fix: sender relay credentials lookup by domain (#193)

In smtp_sasl_password_maps the search key has the form '@Domain' when
the lookup occurs by domain. Ensure a "@" is prepended to the
rule_subject value when compared to the '@Domain' form.

Refs NethServer/dev#7551

Author: DavidePrincipi

postfix/etc/postfix/relaycredentials.cf

@@ -7,7 +7,12 @@ dbpath = /srv/pcdb.sqlite
 query = SELECT FORMAT('%%s:%%s', username, password) AS credentials
   FROM relayrules
   WHERE enabled = 1 AND (
-    (rule_subject = '%s' AND rule_type = 'sender')
+    (rule_type = 'sender' AND
+      CASE INSTR('%s', '@')
+        WHEN 1 THEN ('@' || rule_subject) = '%s'
+        ELSE rule_subject = '%s'
+      END
+    )
     OR ('%s' IN (FORMAT('[%%s]:%%s', host, port), FORMAT('[%%s]', host)) AND rule_type != 'sender')
   ) AND username != ''
   LIMIT 1

tests/50__smtp/00__relay_rules.robot

@@ -27,6 +27,13 @@ Sender domain rule has less priority than address match
     ...                     credentials=u3:Nethesis,1234
     Should be relayed via SMTP  port=10002  smtp_user=${EMPTY}
 
+Sender domain rule provides the correct credentials
+    [Tags]    bug    bug-7551
+    Send SMTP message to    somebody@wildcard.test
+    ...                     from=noreply@addusers.test
+    ...                     credentials=u3:Nethesis,1234
+    Should be relayed via SMTP  port=10002  smtp_user=usr_bug7551
+
 Recipient domain rule has less priority than address match
     Send SMTP message to    someone@rcptrule.test
     ...                     from=u1@inbound.test
@@ -46,5 +53,6 @@ Add relay rules
     Add relay rule    sender      u1@inbound.test      127.0.0.1    10002    usr_u1
     Add relay rule    sender      u3@inbound.test      127.0.0.1    10002    usr_u3
     Add relay rule    recipient   rcptrule.test        127.0.0.1    10003    ${EMPTY}
+    Add relay rule    sender      addusers.test        127.0.0.1    10002    usr_bug7551
     Add relay rule    sender      g1@inbound.test      127.0.0.1    10002    usr_g1
     Add relay rule    recipient   dude@rcptrule.test   127.0.0.1    10004    usr_relay