Fixes #3143 - unprocessible mail "FrozenError: can't modify frozen String"

app/models/channel/email_parser.rb

@@ -709,11 +709,13 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
       end
     end
 
+    file_body = String.new(file.body.to_s)
+
     # generate file name based on content type
     if filename.blank? && headers_store['Content-Type'].present? && headers_store['Content-Type'].match?(%r{^message/rfc822}i)
       begin
         parser = Channel::EmailParser.new
-        mail_local = parser.parse(file.body.to_s)
+        mail_local = parser.parse(file_body)
         filename = if mail_local[:subject].present?
                      "#{mail_local[:subject]}.eml"
                    elsif headers_store['Content-Description'].present?
@@ -813,7 +815,7 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
     headers_store.delete('Content-Disposition')
 
     attach = {
-      data:        file.body.to_s,
+      data:        file_body,
       filename:    filename,
       preferences: headers_store,
     }

test/data/mail/mail092.box

@@ -0,0 +1,62 @@
+Return-Path: <>
+X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on
+	mail.example.com
+X-Original-To: test@example.com
+Delivered-To: receiver@example.org
+X-policyd-weight:  NOT_IN_SPAMCOP=-1.5 NOT_IN_IX_MANITU=-1.5 CL_IP_EQ_HELO_IP=-2 (check from: .. - helo: .mail.example. - helo-domain: .example.)  FROM/MX_MATCHES_NOT_HELO(DOMAIN)=1; rate: -4
+Received: from mail.example.com (mail.example.com [127.0.0.1])
+	by mail.example.com (Postfix) with ESMTPS id 82CC2418018B
+	for <receiver@example.org>; Wed, 22 Jul 2020 13:43:07 +0200 (CEST)
+Received: from bouncer (unknown [127.0.0.1])
+	by mail.example.com (Postfix) with ESMTP id 39A27804391D
+	for <receiver@example.org>; Wed, 22 Jul 2020 13:43:06 +0200 (CEST)
+To: receiver@example.org
+Subject: Undelivered Mail Returned to Sender
+Auto-Submitted: auto-replied
+MIME-Version: 1.0
+Content-Type: multipart/report; report-type=delivery-status; boundary="5E5F521185D1.1207995974/gmmr"
+From: MAILER-DAEMON (Mail Delivery System) <postmaster@example.com>
+Message-Id: <20200722114311.82CC2418018B@mail.example.com>
+Date: Wed, 22 Jul 2020 13:43:07 +0200 (CEST)
+X-KasLoop: m0506075
+
+This is a MIME-encapsulated message.
+
+--5E5F521185D1.1207995974/gmmr
+Content-Description: Notification
+Content-Type: text/plain; charset=us-ascii
+
+This is the mail system at Centrum Holdings
+
+I'm sorry to have to inform you that your message could not
+be delivered to one or more recipients. It's attached below.
+
+For further assistance, please contact your system administrator.
+
+If you do so, please include this problem report. You can
+delete your own text from the attached returned message.
+
+                   The mail system
+
+--5E5F521185D1.1207995974/gmmr
+Content-Description: Delivery report
+Content-Type: message/delivery-status
+
+Reporting-MTA: dns; mail.example.com
+X-Postfix-Queue-ID: 242788039D8C
+X-Postfix-Sender: rfc822; receiver@example.org
+Arrival-Date: Wed, 22 Jul 2020 13:43:06 +0200 (CEST)
+
+Final-Recipient: rfc822; receiver@example.org
+Action: failed
+Status: 5.2.2
+Diagnostic-Code: X-Postfix; Mailbox is full
+
+--5E5F521185D1.1207995974/gmmr
+Content-Description: Undelivered Message
+Content-Type: message/rfc822
+Content-Transfer-Encoding: 8bit
+
+
+--5E5F521185D1.1207995974/gmmr--
+

test/data/mail/mail092.yml

@@ -0,0 +1,45 @@
+--- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+from: MAILER-DAEMON <postmaster@example.com> (Mail Delivery System)
+from_email: postmaster@example.com
+from_display_name: MAILER-DAEMON
+to: receiver@example.org
+subject: Undelivered Mail Returned to Sender
+body: |
+  This is the mail system at Centrum Holdings
+
+  I'm sorry to have to inform you that your message could not
+  be delivered to one or more recipients. It's attached below.
+
+  For further assistance, please contact your system administrator.
+
+  If you do so, please include this problem report. You can
+  delete your own text from the attached returned message.
+
+                     The mail system
+content_type: text/plain
+attachments:
+- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+  data: |
+    Reporting-MTA: dns; mail.example.com
+    X-Postfix-Queue-ID: 242788039D8C
+    X-Postfix-Sender: rfc822; receiver@example.org
+    Arrival-Date: Wed, 22 Jul 2020 13:43:06 +0200 (CEST)
+
+    Final-Recipient: rfc822; receiver@example.org
+    Action: failed
+    Status: 5.2.2
+    Diagnostic-Code: X-Postfix; Mailbox is full
+  filename: Delivery report.txt
+  preferences: !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+    Content-Type: message/delivery-status
+    Content-Description: Delivery report
+    Mime-Type: message/delivery-status
+    Charset: UTF-8
+- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+  data: ''
+  filename: Undelivered Message.eml
+  preferences: !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+    Content-Type: message/rfc822
+    Content-Description: Undelivered Message
+    Mime-Type: message/rfc822
+    Charset: UTF-8