#!/bin/sh
#
# $Id: prequeue 386 2008-05-18 14:45:51Z root $
# $GeorgalisG: prequeue$
#
# primary goal here is to spam/virus filter in smtp for sender
# notification of rejections with zero forgery back-scatter, yet
# deliver locally with filter hooks so users have access to (and
# can report) false positives, if senders report them to rcpt.
#
# this script functions as a QMAILQUEUE program for "in SMTP"
# (active) filtering of email. It accepts stdin from qmail-smtpd,
# and expects associated environmentals including fd1. after
# defining functions and variables, it checks for $DENY (which
# may have been set by ipsvd), logging a drop if so. then it
# tests with clamav. continuing, it checks if $ACCEPT was set
# (by ipsvd) to bypass remaining tests. if not, sbl-xbl hits
# will create an ipsvd reject script for that ip (which can be
# purged after days, by cron, the ipsvd.cdb file should also
# be rebuilt by cron). RBLs and their action can be adjusted
# to taste. next, spamassassin passes or fails. SMTP rejected
# messages have appropriate headers added, their return-path
# is removed and a local delivery is attempted. users should
# filter 554 messages to a spam folder where old messages are
# automatically purged. for now, the various scanners run as
# user qmaild, so all programs have the read/write access they
# need. there may be better way (such as umask and supplementary
# groups), but...
#
# As root, run this once, to initialize
# pq="prequeue"
# install -o qmaild -g qmail -m 2770 -d ~qmaild/count ~qmaild/$pq ~qmaild/$pq/new ~qmaild/$pq/tmp  ~qmaild/$pq/cur 
#
# LICENSE: <george@galis.org> wrote this file. As long as you retain this
# notice, you can do anything with it or buy beer -- George Georgalis
#
# exit 31 = permanently refuse
# exit 71 = temporarily refuse
#

#set -x # for debug to /var/log/qmail/smtpd/current

ptr () { # reverse a dotted quad or subnet
 rev="$(echo "$1" | cut -d\. -f1).$2" ; ip="$(echo "$1" | cut -d\. -f2-)"
 [ "$ip" = "$1" ] && echo "${rev}" || ptr $ip $rev ;}

rmfrom () { # remove envelope from
	printf "F\x00" >${tmp}.env-$$
	tr '\0' '\n' <${tmp}.env | sed -e '1d' | tr '\n' '\0' >>${tmp}.env-$$
	mv ${tmp}.env-$$ ${tmp}.env ;}

count () { # increment a counter for stats
 printf '.' >>count/${prog}.$1
}

failforward () { # update ipsvd-instruct(5), cdb regenerated separately
 peerd="supervise/qmail-smtpd/peer" # ipsvd-cdb(8) config, group qmaild write perm
 peerm='#!/bin/sh\necho  "220 smtp port"\necho  "250 smtp host"\necho  "550'
 umask 002 ; printf "$peerm $opinion\"\n" >$peerd/$TCPREMOTEIP
 chmod +x $peerd/$TCPREMOTEIP
 echo "${prog}: failforward: $opinion" 1>&2 # to log
 rmfrom # remove envelope from
 formail -f -b -A "X-${prog}: 554 $host mail server permanently rejected message" \
	-A "$opinion" <"$tmp" | ./bin/qmail-queue 1<${tmp}.env # mark and queue
 rm -f "$tmp" ${tmp}.env
 count failforward
 exit 31 ;} # permanently refuse

fail () { # mark the message with failure report and refuse
 rmfrom # remove envelope from
 formail -f -b -A "X-${prog}: 554 $host mail server permanently rejected message" \
	-A "$opinion" <"$tmp" | ./bin/qmail-queue 1<${tmp}.env # mark and queue
 echo "${prog}: fail: $opinion" 1>&2 # to log
 rm -f "$tmp" ${tmp}.env
 count fail
 exit 31 ;} # permanently refuse

drop () { # just log the drop and delete the tmp
 echo "${prog}: drop: $opinion" 1>&2 # to log
 rm -f "$tmp" ${tmp}.env
 count drop
 exit 31 ;} # permanently refuse

warn () { # error, log then temporarily refuse
# formail -f -b -A "X-${prog}: 430 $host mail server temporarily rejected message" \
#	-A "$opinion" <"$tmp" | ./bin/qmail-queue 1<${tmp}.env # mark and queue
 echo "${prog}: warn: $opinion" 1>&2
 rm -f "$tmp" ${tmp}.env
 count warn
 exit 71 ;} # temporarily refuse

pass () { # mark it and pass to the regular queue
 echo "${prog}: pass: $opinion" 1>&2 # to log, before fd/2 is connected to qmail-queue
 formail -f -b -A "X-${prog}: 250 $host accepted message" \
	-A "$opinion" <"$tmp" | ./bin/qmail-queue 1<${tmp}.env ; testexit=$?
 count pass
 rm "$tmp" ${tmp}.env ; exit $testexit ;} # return whatever qmail-queue exits as

cd /var/qmail
pq="prequeue" # a maildir with qmaild write perms
now=$(date "+%x %r %Z")
host=$(head -n1 control/me)
prog=$(basename $0)
ptrip=$(ptr ${TCPREMOTEIP})
# $pq/tmp is a tmp for this operation, $pq is tmp for this program
# $pq is also a maildir for messages rejected by this program
tmp="$pq/$(/usr/pkg/bin/safecat $pq/tmp $pq)" || exit 71 # </dev/stdin # put message to disk, if possible
cat <&1 >"${tmp}.env" || exit 71 # save envelope
count '' # grand total

if [ -n "$DENY" ]; then
 opinion="${TCPREMOTEIP} $DENY"
 count fail.ipsvd
 drop
fi
 
score="X-clamav: $(clamdscan --config-file=/usr/local/etc/clamav/clamd.conf --no-summary ${tmp})" ; testexit=$?
case $testexit in
 0) true ; count pass.clamav ;; # no virus
 1) opinion="$(echo $score | sed -e "s;${PWD}/${tmp}: ;;") ($now)" ; count fail.clamav ; drop ;; # virus found
 *) opinion="$(echo $score | sed -e "s;${PWD}/${tmp}: ;;") ($now)" ; count warn.clamav ; warn ;; # clamav error
esac

# Check if $ACCEPT is set to tag message and bypass remaining tests
if [ -n "$ACCEPT" ]; then
 opinion="X-ipsvd: $ACCEPT ($now)"
 count pass.ipsvd
 pass
fi

opinion="X-sbl-xbl:$(dnstxt ${ptrip}sbl-xbl.spamhaus.org \
 | sed 's/http/ http/g' | grep http) ($now)" && count fail.sbl-xbl && failforward \
	|| count pass.sbl-xbl

# too many major ISP relays added
#opinion="X-sorbs-spam: $(dnstxt ${ptrip}spam.dnsbl.sorbs.net \
# | grep http)" && fail

# blocked yahoo groups... will restore after ACCEPT peer is fortified
# opinion="X-spamcop: $(dnstxt ${ptrip}bl.spamcop.net \
# | grep http) ($now)" && fail

# score upto 300KB with spamd, 250KB default, but no workie -s 307200 
score=$(spamc -x -c  <"$tmp") ; testexit=$?
opinion="X-spamc: ${score} ${TCPREMOTEIP} ${host} ($now)"
case $testexit in
 0) pass ; count pass.spamd ;; # ham
 1) fail ; count fail.spamd ;; # spam 
 *) warn ; count warn.spamd ;; # spamc error 
esac

count fail.bug
exit 81 # Internal bug