Provided by: messagewall_1.0.8-3_i386 bug


       messagewall - a filtering SMTP proxy




       When  MessageWall  starts, it begins listening on port 25 of listen_ip,
       and opens up max_backends connections to backend_ip  on  port  25.   It
       accepts  messages  from  SMTP  clients  on  listen_ip,  assigns  them a
       "profile" based on their  envelope  destination  address  and  performs
       filtering  as  specified  in the "profile".  If the message passes this
       filtering, it is sent on to the backend for delivery.  Refused messages
       generate  errors during the SMTP conversation itself; MessageWall never
       generates bounce messages itself.

       If the backend  server  becomes  unavailable,  MessageWall  will  issue
       temporary  errors to connecting clients.  MessageWall never queues mail


       MessageWall needs to  bind  to  port  25  on  listen_ip  shortly  after
       starting, so it must be run as root.  After binding this IP, it chroots
       to the directory specified as root.  It then drops its UID and  GID  to
       user and group, respectively.  It also drops supplemental groups.

       Precautions  are taken inside MessageWall at all points for safe string
       and format handling to protect against buffer  overflows.   MessageWall
       never  launches  any external programs, and only opens files inside its
       chroot that were specified in the configuration file.  It  never  opens
       any files for writing.

       max_clients  and  max_per_ip  provide  DoS  protection  to the greatest
       extent possible in TCP.

       Please report any security issues to  <>.   While
       we  understand  that all security researchers have their own disclosure
       policies, we would appreciate 48 hours notice before public release  of
       an advisory, to give us time to develop and test appropriate fixes.


       Ian Gulliver <>



                                  2002-06-08                    messagewall(1)