#!/bin/sh
#
# /etc/local-COMMON/postfix/postfix.sh
# Copyright 2002-2010,2013-2016,2020 Jonas Smedegaard <dr@jones.dk>
#
# Auto-tweak plain installed postfix Debian package
#
# Depends: postfix (>= 3.4)
#
# FIXME:
#  * replace dkimproxy with opendkim: https://wiki.debian.org/opendkim
#
# TODO:
#  * Implement stuff from here: http://www.wsrcc.com/spam/
#  * Implement stuff from here: http://www.muine.org/~hoang/postfix.html
#  * Implement stuff from here: http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt
#  * Figure out a way to use chroot jail for TLS stuff.
#  * Use https://www.dnswl.org/

set -e

# Let's standardize sort
export LC_ALL=C

warn()	{
	echo >&2 "Warning: $1"
}

exit1()	{
	echo >&2 "Error: $1"
	echo >&2 "Exiting..."
	exit 1
}

FORCE=${FORCE:-}

REDPILL=${REDPILL:-REDPILL}
REALM=${REALM:-ORG}

# superseded by redpill config mailhost
TLS_CHAIN_FILES=${TLS_CHAIN_FILES:-}

# TODO: maybe use AMaViS default of 20 (and instead tune spamassassin)
# <https://www.ijs.si/software/amavisd/amavisd-new-docs.html#max_requests>
AMAVIS_MAXPROC=${AMAVIS_MAXPROC:-2}

# TODO: check if DKIMPROXY_MAXPROC_IN should be handled too
#DKIMPROXY_MAXPROC_IN=5
DKIMPROXY_MAXPROC_OUT=5

# resolve redpill config paths
realmsdir="/etc/local-$REDPILL"
thisrealm=$(cat "/etc/local-$REALM/realm" || dnsdomainname | tr '[:lower:]' '[:upper:]')
if ! [ -d "$realmsdir" ]; then
	warn "Realms directory \"$realmsdir\" does not exist."
fi
catfilefromownrealm() {
	set -e
	file=$1
	[ -d "$realmsdir" ] || exit 0

	cat "$realmsdir/$thisrealm/$file"
}
catallfilesfromotherrealms() {
	set -e
	file=$1
	[ -d "$realmsdir" ] || exit 0
	[ -f "$realmsdir/realms" ] || exit 0

	realms=$(sed 's/#.*//' < "$realmsdir/realms")

	for realm in $realms; do
		if [ "$thisrealm" != "$realm" ]; then
			cat "$realmsdir/$realm/$file"
		fi
	done
}
catfirstfile() {
	set -e
	file=$1
	context=${2:-postfix}
	configdir=
	for dir in /etc/local "/etc/local-$REALM" "/etc/local-$REDPILL" /etc/local-COMMON; do
		if [ -d "$dir/$context" ] && [ -f "$dir/$context/$file" ]; then
			configdir="$dir/$context"
			break
		fi
	done
	if [ -z "$configdir" ]; then
		exit1 "ERROR: file \"$file\" not found."
	fi
	cat "$configdir/$file"
}

# TODO: support trailing comment.
getperlvarfromfile() {
	set -e
	var=$1
	default=$2
	file=$3
	context=${4:-postfix}
	catfirstfile "$file" "$context" \
		| var=$var default=$default perl -n \
		-e '/^\$$ENV{"var"}\h*=\h*(\d+)/ and $s=$1; END {print length($s) ? $s : $ENV{"default"}}'
}

getlinesfromfile() {
	set -e
	param=$1
	shift
	replacements=
	for subparam in "$@"; do
		case "$subparam" in
		    *=)
			oldparam=$(echo "$subparam" | awk -F= '{print $1}')
			replacements="$replacements;s/,*[^,]*${oldparam}[^,]*,*/,/"
			continue
			;;
		    *=*=*)
			oldparam=$(echo "$subparam" | awk -F= '{print $1}')
			newparam=$(echo "$subparam" | awk -F= '{print $2}')
			newparamfile=$(echo "$subparam" | awk -F= '{print $3}')
			;;
		    *)
			oldparam=$subparam
			newparam=$subparam
			newparamfile=$subparam
			;;
		esac
		newparamvalues=$(getlinesfromfile "$newparamfile" | sed -e 's/.*=[ ]*//' -e 's/,/ /g')
		newstring=
		for newparamvalue in $newparamvalues; do
			newstring="${newstring}$newparam $newparamvalue,"
		done
		replacements="$replacements;s/$oldparam/$newstring/"
	done
	printf "%s = " "$param"
	catfirstfile "$param" | sed 's/#.*//' | tr '\n' ',' | sed -e 's/^[, 	]*//;s/[, 	]\+/,/g' -e 's/\^/ /g' -e "s/,\$//$replacements"
}

thismailhost="$(cat /etc/local/mailhost || catfilefromownrealm mailhost)"

#ENABLE_POSTGREY=
#if [ -x /usr/sbin/postgrey ]; then
#	# FIXME: Use this somehow, and only warn below
#	ENABLE_POSTGREY=1
#else
#	exit1 "ERROR: Greylisting support (Debian package postgrey) missing."
#fi
dovecot=
ENABLE_DOVECOT_LMTP=
ENABLE_DOVECOT_DELIVER=
if [ -x /usr/sbin/dovecot ]; then
	dovecot=1
	if [ -x /usr/lib/dovecot/lmtp ]; then
		ENABLE_DOVECOT_LMTP=1
	elif [ -x /usr/lib/dovecot/deliver ]; then
		warn "Dovecot LMTP missing - (Debian package dovecot-lmtp)."
		ENABLE_DOVECOT_DELIVER=1
	else
		warn "Dovecot deliver missing."
	fi
else
	warn "Dovecot missing - (Debian package dovecot-core or dovecot)."
fi
ENABLE_TLS=
[ -z "$thismailhost" ] || TLS_CHAIN_FILES="/etc/ssl/private/$thismailhost.chain.key"
if [ -f "$TLS_CHAIN_FILES" ]; then
	ENABLE_TLS=1
else
	warn "No TLS - requires key+cert chain file \"$TLS_CHAIN_FILES\". More info at <https://www.postfix.org/postconf.5.html#smtpd_tls_chain_files>"
fi
# TODO: enable only on systems with user accounts
ENABLE_SUBMISSION=1
# TODO: check that dovecot SASL is configured
ENABLE_SASL_INBOUND=
if [ -n "$ENABLE_TLS" ] && [ -n "$dovecot" ] && [ -n "$ENABLE_SUBMISSION" ]; then
	ENABLE_SASL_INBOUND=1
else
	warn "No inbound SASL authentication - requires TLS encryption and Dovecot."
fi
ENABLE_AMAVIS=
if [ -x /usr/sbin/amavisd ] || [ -x /usr/sbin/amavisd-new ]; then
	ENABLE_AMAVIS=1
else
	warn "AMaViS missing (Debian package amavisd-new)."
fi
ENABLE_DKIMPROXY=
if [ -x /usr/sbin/dkimproxy.in ]; then
	if [ "1" = "$ENABLE_AMAVIS" ]; then
		ENABLE_DKIMPROXY=1
	else
		warn "No DKIM/Domainkey - requires DKIMproxy and AMaViS."
	fi
else
	warn "DKIMproxy missing (Debian package dkimproxy)."
fi

confdir=/etc/postfix

_postconf() {
	postconf -c "$tempdir" "$1" "$(echo "$2" | tr '\n' ' ' | sed -e 's/ $//')"
}

postmapfiles=

tempdir=$(mktemp -td postfix.XXXXXX)
cp -a -t "$tempdir" "$confdir"/*

# Inspired by D. J. Bernstein: http://cr.yp.to/smtp/greeting.html
_postconf -e smtpd_banner="\$myhostname NO UCE ESMTP \$mail_name (Debian/GNU)"

_postconf -e "$(getlinesfromfile permit_mx_backup_networks)"
_postconf -e "$(getlinesfromfile smtpd_client_restrictions reject_rhsbl_client)"
_postconf -e "$(getlinesfromfile smtpd_helo_restrictions)"
_postconf -e "$(getlinesfromfile smtpd_sender_restrictions reject_rhsbl_sender ${ENABLE_DKIMPROXY:-sender_access_regex=})"
_postconf -e "$(getlinesfromfile smtpd_recipient_restrictions reject_maps_rbl=reject_rbl_client=maps_rbl_domains)"
_postconf -e "$(getlinesfromfile smtpd_data_restrictions)"

# FIXME: clear only specific line (not whole file) when dkimproxy unused
if [ -f "$tempdir/sender_access_regex" ]; then
	if [ -n "$ENABLE_DKIMPROXY" ]; then
		grep -q -F '/^/  FILTER dkimsign:[127.0.0.1]:10026' "$tempdir/sender_access_regex" \
		|| echo '/^/  FILTER dkimsign:[127.0.0.1]:10026' >> "$tempdir/sender_access_regex"
	else
		if grep -q -F '/^/  FILTER dkimsign:[127.0.0.1]:10026' "$tempdir/sender_access_regex"; then
			echo "echo '' > \"$confdir/sender_access_regex\"" >> "$tempdir/COMMANDS"
			rm "$tempdir/sender_access_regex"
		fi
	fi
	postmapfiles="$postmapfiles sender_access_regex"
fi

# Support exceptions to default response
# (Day Old Bread (dob) lists need to reject only temporarily)
_postconf -e rbl_reply_maps="hash:$confdir/rbl_reply_map"
sed 's/#.*//' \
	< /etc/local-COMMON/postfix/rbl_reply_map \
	> "$tempdir/rbl_reply_map"
postmapfiles="$postmapfiles rbl_reply_map"

# Verify senders of common suspicious and known verifiable domains
# (exclude verification of postmaster@ to not verify verification probes)
# (add own domains before peers for (rare) cases of duplicates)
# FIXME: somehow do this step only if enabled in smtpd_sender_restrictions
# TODO: Properly implement exception exclusion like yahoo (which does not want to be checked any longer!)
grep -v yahoo \
	< /etc/local-COMMON/postfix/maildomains \
	| sort \
	| sed 's/$/	reject_unverified_sender/' \
	> "$tempdir/sender_access"
( catfilefromownrealm maildomains | sort; catallfilesfromotherrealms maildomains | sort ) \
	| sed 's/\(.*\)$/postmaster@\1	permit\n\1	reject_unverified_sender/' \
	>> "$tempdir/sender_access"
[ ! -f "$tempdir/sender_access.addon" ] || cat "$tempdir/sender_access.addon" \
	>> "$tempdir/sender_access"
postmapfiles="$postmapfiles sender_access"
_postconf -e unverified_sender_reject_code=550

# Trust recipient verification too
_postconf -e unverified_recipient_reject_code=550

if [ -n "$ENABLE_DOVECOT_LMTP" ]; then
	_postconf -e mailbox_transport=lmtp:unix:private/dovecot-lmtp
	_postconf -X mailbox_command
elif [ -n "$ENABLE_DOVECOT_DELIVER" ]; then
	_postconf -X mailbox_transport
	_postconf -e mailbox_command=/usr/lib/dovecot/deliver
else
	_postconf -X mailbox_transport
	_postconf -X mailbox_command
fi

# outbound opportunistic encryption
_postconf -e smtp_tls_security_level=may
if [ -n "$ENABLE_TLS" ]; then
	_postconf -e smtp_tls_chain_files="$TLS_CHAIN_FILES"
	_postconf -e smtp_tls_CApath=/etc/ssl/certs
else
	_postconf -X smtp_tls_chain_files
fi
_postconf -e smtp_tls_loglevel=1

# enforce TLS trust path towards peers
catallfilesfromotherrealms mailhost | sort \
	| sed 's/^/[/;s/$/]:submission	secure/' \
	> "$tempdir/tls_policy"
[ ! -f "$tempdir/tls_policy.addon" ] || cat "$tempdir/tls_policy.addon" \
	>> "$tempdir/tls_policy"
postmapfiles="$postmapfiles tls_policy"
_postconf -e smtp_tls_policy_maps="hash:$confdir/tls_policy"

# inbound opportunistic encryption
if [ -n "$ENABLE_TLS" ]; then
	_postconf -e smtpd_tls_security_level=may
	_postconf -e smtpd_tls_chain_files="$TLS_CHAIN_FILES"
	_postconf -e smtpd_tls_loglevel=1
	_postconf -e smtpd_tls_auth_only=yes
	_postconf -e smtpd_tls_received_header=yes
else
	_postconf -e smtpd_tls_security_level=none
	_postconf -X smtpd_tls_chain_files
	_postconf -X smtpd_tls_loglevel
	_postconf -X smtpd_tls_auth_only
	_postconf -X smtpd_tls_received_header
fi
# Avoid smtpd_tls_CApath or smtpd_tls_CAfile to trick outlook.com
# See <http://postfix.1071664.n5.nabble.com/Problems-with-incoming-mails-from-outlook-com-td78356.html>
_postconf -X smtpd_tls_CApath
_postconf -X smtpd_tls_CAfile

# obsolete TLS-related settings
_postconf -X smtpd_use_tls
_postconf -X lmtp_tls_CApath
_postconf -X smtp_tls_CAfile
_postconf -X lmtp_tls_CAfile
_postconf -X smtp_tls_cert_file
_postconf -X smtp_tls_key_file
_postconf -X smtpd_tls_cert_file
_postconf -X smtpd_tls_key_file
_postconf -X smtpd_tls_ask_ccert
_postconf -X smtp_tls_note_starttls_offer
_postconf -X smtpd_tls_session_cache_database
_postconf -X smtpd_tls_session_cache_timeout
_postconf -X smtp_tls_session_cache_database
_postconf -X tls_random_exchange_name
_postconf -X tls_random_source

# submission
# <http://www.postfix.org/SASL_README.html>
# <https://doc.dovecot.org/configuration_manual/howto/postfix_and_dovecot_sasl/#using-sasl-with-postfix-submission-port>
if [ -n "$ENABLE_SUBMISSION" ]; then
	_postconf -Me submission/inet="
submission inet	n	-	y	-	-	smtpd
	-o syslog_name=postfix/\$service_name
	-o smtpd_tls_security_level=encrypt
"
	_postconf -Me smtps/inet="
smtps inet	n	-	y	-	-	smtpd
	-o syslog_name=postfix/\$service_name
	-o smtpd_tls_wrappermode=yes
	-o smtpd_sasl_auth_enable=yes
"
	if [ -n "$ENABLE_SASL_INBOUND" ]; then
		_postconf -Pe submission/inet/smtpd_sasl_auth_enable=yes
		_postconf -Pe smtps/inet/smtpd_sasl_auth_enable=yes
	else
		_postconf -PX submission/inet/smtpd_sasl_auth_enable
		_postconf -PX smtps/inet/smtpd_sasl_auth_enable
	fi
else
	_postconf -MX submission/inet
	_postconf -MX smtps/inet
fi
if [ -n "$ENABLE_SASL_INBOUND" ]; then
	_postconf -e smtpd_sasl_local_domain=\$mydomain
	_postconf -e smtpd_sasl_type=dovecot
	_postconf -e smtpd_sasl_path=private/auth
	_postconf -e broken_sasl_auth_clients=yes
else
	_postconf -X smtpd_sasl_local_domain
	_postconf -X smtpd_sasl_type
	_postconf -X smtpd_sasl_path
	_postconf -X broken_sasl_auth_clients
fi

# obsolete SASL-related settings
_postconf -X smtpd_sasl_auth_enable
_postconf -X smtpd_sasl_security_options

if [ -n "$ENABLE_AMAVIS" ]; then
	amavis_maxproc=$(getperlvarfromfile max_servers "$AMAVIS_MAXPROC" amavisd.conf.addon amavis)
	_postconf -Me amavisfeed/unix="
amavisfeed unix -	-	n	-	$amavis_maxproc	lmtp
	-o lmtp_data_done_timeout=1200s
	-o lmtp_send_xforward_command=yes
	-o disable_dns_lookups=yes
	-o max_use=$amavis_maxproc
"
	_postconf -Me 127.0.0.1:10025/inet='
127.0.0.1:10025 inet n	-	n	-	-	smtpd
	-o content_filter=
	-o local_recipient_maps=
	-o relay_recipient_maps=
	-o smtpd_restriction_classes=
	-o smtpd_delay_reject=no
	-o smtpd_client_restrictions=permit_mynetworks,reject
	-o smtpd_helo_restrictions=
	-o smtpd_sender_restrictions=
	-o smtpd_recipient_restrictions=permit_mynetworks,reject
	-o smtpd_data_restrictions=reject_unauth_pipelining
	-o smtpd_end_of_data_restrictions=
	-o mynetworks=127.0.0.0/8
	-o smtpd_error_sleep_time=0
	-o smtpd_soft_error_limit=1001
	-o smtpd_hard_error_limit=1000
	-o smtpd_client_connection_count_limit=0
	-o smtpd_client_connection_rate_limit=0
	-o receive_override_options=no_unknown_recipient_checks,no_header_body_checks,no_milters
'
	_postconf -e receive_override_options=no_address_mappings
	if [ -n "$ENABLE_DKIMPROXY" ]; then
		_postconf -e content_filter='amavisfeed:[127.0.0.1]:10028'
		_postconf -Pe pickup/unix/content_filter='dkimsign:127.0.0.1:10028'
		if [ -n "$ENABLE_SUBMISSION" ]; then
			_postconf -Pe submission/inet/content_filter='dkimsign:[127.0.0.1]:10028'
			_postconf -Pe smtps/inet/content_filter='dkimsign:[127.0.0.1]:10028'
		fi
		# FIXME: supersede DKIMPROXY_MAXPROC_OUT from /etc/default/dkimproxy
		_postconf -Me dkimsign/unix="
dkimsign unix	-	-	n	-	$DKIMPROXY_MAXPROC_OUT	smtp
	-o smtp_send_xforward_command=yes
	-o smtp_discard_ehlo_keywords=8bitmime,starttls
"
		_postconf -Me 127.0.0.1:10029/inet='
127.0.0.1:10029 inet n	-	n	-	-	smtpd
	-o content_filter=
	-o receive_override_options=no_unknown_recipient_checks,no_header_body_checks,no_milters
	-o smtpd_helo_restrictions=
	-o smtpd_client_restrictions=
	-o smtpd_sender_restrictions=
	-o smtpd_recipient_restrictions=permit_mynetworks,reject
	-o mynetworks=127.0.0.0/8
	-o smtpd_authorized_xforward_hosts=127.0.0.0/8
'
	else
		_postconf -MX dkimsign/unix
		_postconf -MX 127.0.0.1:10029/inet
		_postconf -e content_filter='amavisfeed:[127.0.0.1]:10024'
		_postconf -PX pickup/unix/content_filter
		if [ -n "$ENABLE_SUBMISSION" ]; then
			_postconf -PX submission/inet/content_filter
			_postconf -PX smtps/inet/content_filter
		fi
	fi
else
	_postconf -MX amavisfeed/unix
	_postconf -MX 127.0.0.1:10025/inet
	_postconf -X content_filter
	_postconf -X receive_override_options
fi

# obsolete settings
_postconf -X smtpd_helo_required
_postconf -X maps_rbl_domains
_postconf -X max_use
_postconf -MX smtp-amavis/unix

diff -ruNw "$confdir" "$tempdir" || if [ $? -gt 1 ]; then exit $?; else needs_reload=1; fi

if [ "1" = "$FORCE" ]; then
	do_update=y
elif [ "1" = "$needs_reload" ]; then
	printf 'Above is the intended changes. OK to update (y/N)? '
	read -r do_update
fi
case $do_update in
    y|Y)
	if [ -f "$tempdir/COMMANDS" ]; then
		sh -s < "$tempdir/COMMANDS"
	fi
	rm -f "$tempdir/COMMANDS"

	diff -q "$confdir/master.cf" "$tempdir/master.cf" || if [ $? -gt 1 ]; then exit $?; else needs_restart=1; fi

	cp -a -f -t "$confdir" "$tempdir"/*
	rm -rf "$tempdir"

	for file in $postmapfiles; do
		postmap "$confdir/$file"
	done

	if [ "1" = "$needs_restart" ]; then
		service postfix restart
	else
		service postfix force-reload
	fi

	if [ "1" = "$needs_reload" ]; then
		echo >&2 "Changes applied!"
	fi
	;;
    *)
	if [ "1" = "$needs_reload" ]; then
		exit1 "Aborted!"
	fi
	;;
esac

if [ "1" != "$needs_reload" ]; then
	echo >&2 "No changes needed!"
fi

# Based on this: http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt
# Support for trusted MX backup networks added
# PCRE stuff avoided, as PCRE is only optional on newest Debian packages
# RBLs replaced with those recommended by http://www.antispews.org/
# spam filter based on these: http://www.postfix.org/FILTER_README.html
#   https://www.ijs.si/software/amavisd/amavisd-new-docs.html
# TLS based on this: http://www.postfix.org/TLS_README.html

# Here's a convenient overview of different blackholes:
#   http://rbls.org/