[Remail] [RFC/RFT patch 1/2] remail: Optionally add X-Remail-Originally-From header

[Thomas Gleixner]

The 'From:' header mangling makes it unnecessarily hard to figure out the
name and email address of the person who posted to a list.

Provide an option for the list administrator which adds an

 'X-Remail-Originally-From: <mailname at sender.domain>'

header to the outgoing reencrypted mail.

Defaults to 'false' for backwards compatibility.

The header name might be odd, but List-* headers are a reserved name space
and 'Originally-From:' is already taken and defined for a different
purpose. As especially gmail is very picky about RFC defined headers, use
one in the custom 'X-' namespae which is definitely not used yet and does
not violate any real or established by use standards.

Suggested-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
---
 Documentation/man5/remail.config.rst |    8 ++++++++
 remail/config.py                     |    1 +
 remail/mail.py                       |   10 +++++++---
 remail/maillist.py                   |   14 ++++++++++----
 4 files changed, 26 insertions(+), 7 deletions(-)

--- a/Documentation/man5/remail.config.rst
+++ b/Documentation/man5/remail.config.rst
@@ -263,6 +263,7 @@ Base configuration items
       enabled:            True
       moderated:          True
       attach_sender_info: False
+      set_original_from:  False
       listid:             ...
       archive:
         ...
@@ -280,6 +281,7 @@ Base configuration items
       enabled:            True
       moderated:          True
       attach_sender_info: False
+      set_original_from:  False
 
   enabled:
 
@@ -304,6 +306,12 @@ Base configuration items
     lists and especially contact points so that the subscribers are able
     to contact the sender.
 
+  set_original_from:
+
+    Set the 'X-Remail-Original-From:' custom mail header to reflect the
+    original 'From:' mail header, which has to be rewritten due to
+    re-encryption.
+
   listid:
 
     Optional item to override the default list-id with a custom value.
--- a/remail/config.py
+++ b/remail/config.py
@@ -270,6 +270,7 @@ list_defaults = {
     'enabled'             : False,
     'moderated'           : False,
     'attach_sender_info'  : False,
+    'set_original_from'   : False,
 }
 
 class list_config(object):
--- a/remail/mail.py
+++ b/remail/mail.py
@@ -80,6 +80,7 @@ import re
         'Content-Transfer-Encoding',
         'Content-Language',
         'Envelope-to',
+        'X-Remail-Original-From',
     ]
 
     # Get all headers and remove them from the message
@@ -106,7 +107,7 @@ import re
     server.send_message(msg, sender, [to])
     server.quit()
 
-def msg_deliver(msg, account, mfrom, sender, use_smtp):
+def msg_deliver(msg, account, mfrom, sender, use_smtp, origfrom):
     '''
     Deliver the message. Replace or set the mandatory headers, sanitize
     and order them properly to make gmail happy.
@@ -116,6 +117,9 @@ import re
     msg_set_header(msg, 'Return-path', sender)
     msg_set_header(msg, 'Envelope-to', get_raw_email_addr(account.addr))
 
+    if origfrom:
+            msg_set_header(msg, 'X-Remail-Original-From', encode_addr(origfrom))
+
     sanitize_headers(msg)
 
     # Set unixfrom with the current date/time
@@ -128,7 +132,7 @@ import re
     else:
         print(msg.as_string())
 
-def send_mail(msg_out, account, mfrom, sender, listheaders, use_smtp):
+def send_mail(msg_out, account, mfrom, sender, listheaders, use_smtp, origfrom=None):
         '''
         Send mail to the account. Make sure that the message
         is correct and all required headers and only necessary
@@ -138,7 +142,7 @@ import re
         for key, val in listheaders.items():
             msg_out[key] = val
 
-        msg_deliver(msg_out, account, mfrom, sender, use_smtp)
+        msg_deliver(msg_out, account, mfrom, sender, use_smtp, origfrom)
 
 # Minimal check for a valid email address
 re_mail = re.compile('^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,})+$')
--- a/remail/maillist.py
+++ b/remail/maillist.py
@@ -86,11 +86,16 @@ import os
             self.gpg.encrypt(msg, account)
         return msg
 
-    def send_encrypted_mail(self, msg_plain, account, mfrom):
+    def send_encrypted_mail(self, msg_plain, account, mfrom, origfrom):
         try:
             msg_out = self.encrypt(msg_plain, account)
+
+            if not self.config.set_original_from:
+                origfrom = None
+
             send_mail(msg_out, account, mfrom, self.config.listaddrs.bounce,
-                      self.config.listheaders, self.use_smtp)
+                      self.config.listheaders, self.use_smtp, origfrom)
+
         except (RemailGPGException, RemailSmimeException) as ex:
             '''
             GPG and S/MIME exceptions are not fatal. If they happen
@@ -268,7 +273,8 @@ import os
 
         msgid = msg.get('Message-Id', '<No ID>')
         msgto = msg.get('To')
-        msgfrom = get_raw_email_addr(msg.get('From'))
+        origfrom = msg.get('From')
+        msgfrom = get_raw_email_addr(origfrom)
         sinfo = sender_info(msg)
 
         # Archive the incoming mail
@@ -298,7 +304,7 @@ import os
         for account in dest.accounts.values():
             if not account.enabled:
                 continue
-            self.send_encrypted_mail(msg_plain, account, mfrom)
+            self.send_encrypted_mail(msg_plain, account, mfrom, origfrom)
         return True
 
     def handle_log(self):