# pm-jaube-prg-bmf.rc -- Interface to Bayesian Mail Filter program
#
#   File id
#
#       Copyright (C) 1997-2010 Jari Aalto
#
#       This program is free software; you can redistribute it and/or
#       modify it under the terms of the GNU General Public License as
#       published by the Free Software Foundation; either version 2 of the
#       License, or (at your option) any later version
#
#       This program is distributed in the hope that it will be useful, but
#       WITHOUT ANY WARRANTY; without even the implied warranty of
#       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#       General Public License for more details at
#       <http://www.gnu.org/copyleft/gpl.html>.
#
#   Warning
#
#       Put all your Unsolicited Bulk Emacil (aka spam) filters towards the
#       end of your `~/.procmailrc'. The idea is that valid messages
#       are filed first (mailing lists, your work and private mail,
#       bounces) and only the uncategorized messages are checked last.
#
#       YOU CANNOT USE THIS PROCMAIL SUBROUTINE UNLESS YOU HAVE TRAINED THE
#       BAYESIAN PROGRAM FIRST!
#
#       To train:
#
#           $ ls spam/*.mail | xargs -n 1 bmf -s # feed individual messages
#           $ ls good/*.mail | xargs -n 1 bmf -n # feed individual messages
#
#       To test
#
#           $  bmf -p < test.mail | less
#
#   Overview of features
#
#       o   Implements interface to http://www.sf.net/projects/bmf
#           "Bayesian Mail Filter" project. The called binary is "bmf"
#           hence the name of this subroutine. Bmf program uses well
#           know statistical analysis which is much more reliable than
#           any hand made procmail scripts could ever achieve.
#       o   Variable `ERROR' is set if the message was UBE.
#       o   Results are available in headers `X-Spam-bmf-Status' and
#           `X-Spam-bmf-Flag' for further analysis.
#
#   Description
#
#       There are several bayesian based statistical analysis programs that
#       study the message's tokens and then classify it into two categories:
#       good or bad, or if you like, ham and spam. All the Bayesian programs
#       are not the same, so if you want to achive magic 99.99% probability
#       the only methodology to do that is to chain several programs in
#       serially. There is no single program that can solve the
#       UBE detection.
#
#       For serious discussion of strenghts of the different programs,
#       refer to a very good article "Spam Filters" by Sam Holden at
#       2004-08-16 <http://freshmeat.net/articles/view/964>. The
#       article evaluated throughly following programs:
#
#       o   Bayesian Mail Filter        (bayesian)
#       o   Bogofilter                  (bayesian)
#       o   dbacl                       (bayesian; multiple wordlists)
#       o   Quick Spam Filter           (bayesian)
#       o   SpamAssassin                (perl matching + bayesian)
#       o   SpamProbe                   (bayesian)
#       o   SPASTIC                     (procmail recipes)
#
#       This subroutine implements call interface to `bmf' program. Why
#       whould you need it? Because unfortunately `bmf' by default
#       use exactly the same headers as spamasassin and the two cannot
#       co-operate together: bmf would overwrite existing
#       spamassasin headers. This subroutine takes care of saving
#       previous headers and move `bmf' results to their own
#       `X-Spam-bmf-*' headers.
#
#   About bouncing message back
#
#       The general consensus is, that you should not send bounces.
#       The UBE sender is not there, because the address forged. Do
#       not increase the network traffic; you will not do any good to
#       anybody by bouncing messgas -- you just increase mail traffic
#       even more. Instead save the messages to folders and
#       periodically periodically check their contents.
#
#   Required settings
#
#       If `bmf' program is available, define this variable in your
#       `~/.procmailrc'. Use absolute path to make the external shell
#       quick; it'll save server load considerably.
#
#           JA_UBE_BMF_PRG = "/usr/bin/bmf"
#
#       If you _do_ _not_ have program installed, do not leave the
#       variable lying aroung, because it will keep this subroutine active.
#       Calling a non existing program is not a good idea, so it better to
#       empty the variable if the program is not available.
#
#   Required settings
#
#       None. No dependencies to other procmail modules.
#
#   Call arguments (variables to set before calling)
#
#       o   JA_UBE_BMF_PRG, path to program
#       o   JA_UBE_BMF_HEADER_PREFIX, the header name where the results
#           are put. If not defined, no headers are added. Default
#           value is `X-Spam-bmf'.
#       o   JA_UBE_BMF_FORCE, if set to _yes_ then call program no matter
#           what. Normally if there already are `X-Spam-bmf-*' headers,
#           it is assumed that the message has already been checked
#           and no new checking is needed.
#
#   Return values
#
#       o   ERROR, is set to short ube trigger recipe reason. Contains
#           content of `X-Spam-bmf-Status' header which you can check
#           for values
#       o   ERROR_MATCH contains detailed content of
#           `X-Spam-bmf-Status' header.
#
#       If headers were enabled, they will contain:
#
#           X-Spam-bmf-Status: Yes, hits=1.000000 required=0.900000, tests=bmf
#           X-Spam-bmf-Flag: YES
#
#   Usage example
#
#           PMSRC            = $HOME/procmail # procmail recipe dir
#
#           <other checks, mailing lists, work mail etc.>
#
#           JA_UBE_BMF_PRG   = "/usr/bin/nice -n 5 /usr/bin/bmf"
#           INCLUDERC        = $PMSRC/pm-jaube-prg-bmf.rc
#
#           #   The ERROR will contains word "yes" if it program classified
#           #   the message into "bad" category.
#
#           :0 :
#           * ERROR ?? yes
#           junk.mbox
#
#   File layout
#
#       The layout of this file is managed by Emacs packages tinyprocmail.el
#       and tinytab.el for the 4 tab text placement.
#       See project http://freshmeat.net/projects/emacs-tiny-tools/
#
#   Change Log
#
#       None

dummy = "
========================================================================
pm-jaube-prg-bmf.rc: init:"

# ................................................... User variables ...

#   You must define program path, because we don't know
#   if it has been installed in this system or not

JA_UBE_BMF_PRG           = ${JA_UBE_BMF_PRG:-""}
JA_UBE_BMF_PRG_OPT       = ${JA_UBE_BMF_PRG_OPT:-"-p"}

#   The header name prefix with no colon at the end. If this variable
#   is empty, then `formail' is not called and no headers are added to
#   the message. This saves a shell call and will make this repice a
#   bit faster.  The return status can still be checked from variable
#   ERROR

JA_UBE_BMF_HEADER_PREFIX = ${JA_UBE_BMF_HEADER_PREFIX:-"X-Spam-Bmf-"}

#   Should we run the check even if there aready were header
#   JA_UBE_BMF_HEADER_PREFIX? Setting to 'yes' might mean:
#
#   o   We suspect that someone else had added the header, so don't
#       trust it but generate our own
#   o   We don't trust the local MDA's result (if it had invoked
#       bmf for us), because we want' to run the message
#       through our own trained database
#   o   Or, we're simply testing and have several INCLUDERC=$RC_UBE_BMF
#       calls in our ~/.procmailrc to find out what location would be the
#       best (beginning, middle, last) by examining the procmail LOGFILE.

JA_UBE_BMF_FORCE         = ${JA_UBE_BMF_FORCE:-"no"}

# ............................................................ do it ...

ERROR    # Kill variable

# The condition below reads:
# - Require that variable is defined (contains path to 'bmf' program)
# - Run immediately: if there is no X-spambmf header
# - OR Run immediately: (even if there were headers) forced evaluation

:0
*  JA_UBE_BMF_PRG ??   [a-z]
*$ 9876543210^0    !  ^$JA_UBE_BMF_HEADER_PREFIX
*  9876543210^0    !   JA_UBE_BMF_FORCE ?? yes
{

    #  Unfortunately bmf inserts same headers as Spamassassin (SA), so
    #  we must first save previous SA values. Kill variables first
    #
    #  Note: the initial value is set here to header name, so that if
    #  there is no previous SA headers, they will be left empty. This
    #  works fine, because e.g. "formail -I X-Name:" does nothing when
    #  message does not include "X-Name:" header.

    dummy = "pm-jaube-prg-bmf.rc: saving previous X-Spam-* headers"

    jaubeBmfSaStatus = "X-Spam-Status:"
    jaubeBmfSaFlag   = "X-Spam-Flag:"

    :0
    *   ^\/X-Spam-Status:.*
    * ! ^\/X-Spam-Status:.*tests=bmf
    {
        jaubeBmfSaStatus = $MATCH

        :0
        * ^\/X-Spam-Flag:.*
        {
            jaubeBmfSaFlag = $MATCH
        }
    }

    # Now run the filter with -p "pass through".

    jaubeBmfStatus
    jaubeBmfFlag

    :0 fw : bmf$LOCKEXT
    | $JA_UBE_BMF_PRG ${JA_UBE_BMF_PRG_OPT}

    # After previous call, there should be these headers. It is unfortunate,
    # that "tests=bmf" is not included with "No" case
    #
    #   X-Spam-Status: No, hits=0.000000 required=0.900000
    #   X-Spam-Status: Yes, hits=1.000000 required=0.900000, tests=bmf
    #   X-Spam-Flag: YES

    :0 a
    * ^X-Spam-Status: \/.+
    {

        :0
        * ^X-Spam-Status: \/.+tests=bmf
        {
            ERROR = $MATCH
        }

        jaubeBmfStatus = "${JA_UBE_BMF_HEADER_PREFIX}Status: $MATCH"
        jaubeBmfFlag   = "${JA_UBE_BMF_HEADER_PREFIX}Flag:"  # Initial value

        :0
        * ^X-Spam-Flag: \/.*
        {
            jaubeBmfFlag = "$jaubeBmfFlag $MATCH"
        }

        dummy = "pm-jaube-prg-bmf.rc: restore X-Spam-* / add X-Spam-Bmf headers"

        #   Rearrange headers nicely and put back all Spamassassin values

        :0 fhw
        * ! jaubeBmfSaStatus  ?? ^^^^
        * ! jaubeBmfSaFlag    ?? ^^^^
        * ! jaubeBmfStatus    ?? ^^^^
        * ! jaubeBmfFlag      ?? ^^^^
        | ${FORMAIL:-formail}       \
            -I "$jaubeBmfSaStatus"  \
            -I "$jaubeBmfSaFlag"    \
            -I "$jaubeBmfStatus"    \
            -I "$jaubeBmfFlag"
    }
}

dummy = "pm-jaube-prg-bmf.rc: end: $ERROR"

# pm-jaube-prg-bmf.rc ends here