prefix message-id in attachment-quarantine

This patch fixes #2785.

When using the attachment quarantine - the message is:
a) stored in the quarantine unaltered
b) sent on with the attachment removed

Currently we do not change the message in any other way - in particular
we do not change the message-id header of any of the 2 mails.

When a mail is released from the attachment quarantine it is sent by PMG
with the same message-id as the mail with the attachments removed.

This is a violation of RFC 5322 (see [0]), and additionally newer versions
of Exchange do accept 2 mails with the same message-id but silently discard
the second version, thus making the attachment quarantine unusable for
Exchange users.

This patch simply prefixes the message-id with 'pmg-aquar-$$' (where $$ is
the pid of the pmg-smtp-filter process) for the mail without attachment.

By keeping the original message-id in the headers tracing the mailflow should
be facilitated.

The Message-ID is left intact on the original message in order to keep DKIM
signatures valid (they are invalidated on the modified mail by the removal
of the attachment anyways).

[0] https://tools.ietf.org/html/rfc5322 (section 3.6.4)

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>

diff --git a/src/PMG/RuleDB/Remove.pm b/src/PMG/RuleDB/Remove.pm
index e57c21686f501eb550a6ec7da9647e94b4671cf8..6b27b915def67da95438262bc91b80efdcc4faca 100644 (file)
--- a/src/PMG/RuleDB/Remove.pm
+++ b/src/PMG/RuleDB/Remove.pm
@@ -224,6 +224,14 @@ sub execute {
            my $original_entity = $entity->dup;
            PMG::Utils::remove_marks($original_entity);
            if (my $qid = $queue->quarantine_mail($ruledb, 'A', $original_entity, $tg, $msginfo, $vars, $ldap)) {
+               # adapt the Message-ID header of the mail without attachment to
+               # prevent 2 different mails with the same Message-ID
+               my $message_id = $entity->head->get('Message-ID');
+               if (defined($message_id)) {
+                   $message_id =~ s/^(<?)(.+)(>?)$/$1pmg-aquar-$$-$2$3/;
+                   $entity->head->replace('Message-ID', $message_id);
+               }
+
                foreach (@$tg) {
                    syslog ('info', "$queue->{logid}: moved mail for <%s> to attachment quarantine - %s (rule: %s)", $_, $qid, $rulename);
                }