#!/usr/bin/zsh --
# Program that delays mail files, to catch bulk-spam before it is send.
# This script spools the antiSPAM-delay directory.
#
# Program released under the terms of the GNU GPL3.
# This is free software. You are free to copy and redistribute.
# No warranty. See http://www.gnu.org for license details.
# (C) 2007 Jos Boersema
#
# Usage: prog MAIL_FILE [exim4in|headers|RECIPIENTS]
# Manual:
#        Configure user-variables
#            -> mkdir a spool-directory for spam-delay,
#               same as in maildlay-input
#            -> point REAL_MAIL_SPOOL to the spool directory that should
#               receive the mail-file after the delay
#            -> make /etc/maildlay
#               -> list users that should have all their mails
#                  send through without additional delay.
#                  -> write ``zerodelay:username'' in it, once for each user
#                       > cat /etc/maildlay
#                       zero-delay:hans
#                       zero-delay:grietje
#                       (...)
#            -> Decide on a delay-speed: DELAY_SPEED
#        Test: point REAL_MAIL_SPOOL to a test directory, send in mail
#              files using maildlay-input, then run maildlay-spool to
#              see if delays are correctly reduced and send to the
#              test directory.
#        Operation: cron job
#                   The interval at which this program is run determines
#                   the delay per recipient. The job should probably only 
#                   begin again after it has ended. Typically the job
#                   would run per 2 minutes, 5 minutes 15 minutes, etc.
#
#                   Example: with 5 minutes, a mail with 3 recipients is
#                   held for 10 to 15 minutes prior to sending, if 
#                   delay-speed is "1". If delay-speed is "3" the delay 
#                   is 5 minutes or less.
#                   If a user sends 1000 mails, a delay-speed of 10 means
#                   means the mail goes out at 10 mails per 5 minutes
#                   if the mails are individually stored. If it is one
#                   mail with a lot of recipients, then that mail waits
#                   until the end of 1000 mails / 10 mails-a-job * 5
#                   minutes a job = 500 minutes = 8 hours.
#                   When the maildlay-report program runs every 2 hours
#                   with a report-limit of 500 mails per user, the report
#                   is send in at least 6 hours before all mails have been
#                   send out. When there is one mail with a lot of
#                   recipients, they are all not yet send out before reported.
#                   (When the bulk is legitimate, the user can get stored
#                   in /etc/maildlay as trusted.)

########################################################################
#######             USER VARIABLES                          ############
########################################################################

# Set this to a directory that acts as a temporary bulk-spam delay buffer.
#SPAM_DELAY_SPOOL="/var/spool/mail/antispamdelay"
SPAM_DELAY_SPOOL="/tmp/antispamdelay"

# Set this to the real mail spool, where the mails should go after
# they went through the delay.
#REAL_MAIL_SPOOL="/var/spool/exim4/input"
REAL_MAIL_SPOOL="/tmp/input"

# Set to with how many number-of-recipients, the mail moves through
# to the point of moving out of the delay-spool per call of this prog.
# Set to 1 means a mail with 8 recipients gets reduced 7, 6, 5, ...
# Set to 2: 6, 4, 2 ...
DELAY_SPEED="1"

########################################################################
#######                  END                                ############
########################################################################

cd ${SPAM_DELAY_SPOOL} #change directory

#Do one spool action per user ...
for USERGO in $( ls * | sed -e 's/_Bye__.*//;s/_[0-9]*__.*//;' | uniq )
	do
		# priviledged users
		# Users that are trusted, for instance users that are known to send
		# legitimate bulk mail and users that need quick e-mail.
		if test -n "$( grep "zero-delay:${USERGO}" /etc/maildlay )"
			then
				for FILE in $( ls ${SPAM_DELAY_SPOOL}/${USERGO}_* ) 
					do
						ORIGFILE=$( echo ${FILE} | sed -e 's/.*_[0-9]*__//;s/.*_Bye__//;' )
						mv "${FILE}" "${REAL_MAIL_SPOOL}/${ORIGFILE}"
					done
		fi

		#Move each file recipient-number one step down, 0 = `Bye'
		# .. this loop is only taken once if at all ..
		for FILE in $( ls ${SPAM_DELAY_SPOOL}/${USERGO}_[0-9]*__* | head -1 ) 
			do
				DELAYN=$( echo "${FILE}" | sed -e 's/__.*//;s/.*_//;' )
				DELAYN=$(( ${DELAYN} - ${DELAY_SPEED} )) #can get below zero, -N
				ORIGFILE=$( echo ${FILE} | sed -e 's/.*_[0-9]*__//;' )
				FROMUSER=$( echo ${FILE:t} | sed -e 's/_.*//' )
				if test "0" = "${DELAYN}"
					then
						#reached 0 
						mv "${FILE}" "${REAL_MAIL_SPOOL}/${ORIGFILE}"
				elif test "-" = "${DELAYN[1]}"
					then
						#reached below zero
						mv "${FILE}" "${REAL_MAIL_SPOOL}/${ORIGFILE}"
				else
						#reduce delay-count
						mv "${FILE}" "${FROMUSER}_${DELAYN}__${ORIGFILE}"
				fi
			done
	done