#!/bin/bash
#
# This file is an example post-data hook that will run standard filtering
# utilities if they are available.
#
#  - greylist (from greylistd) to do greylisting.
#  - spamc (from Spamassassin) to filter spam.
#  - rspamc (from rspamd) to filter spam.
#  - clamdscan (from ClamAV) to filter virus.
#  - dkimsign (from driusan/dkim) to do DKIM signing.
#
# If it exits with code 20, it will be considered a permanent error.
# Otherwise, temporary.

set -e


# Note greylistd needs you to add the user to the "greylist" group:
#   usermod -a -G greylist mail
if [ "$AUTH_AS" == "" ] && [ "$SPF_PASS" == "0" ] && \
	command -v greylist >/dev/null && \
	groups | grep -q greylist;
then
	REMOTE_IP=$(echo "$REMOTE_ADDR" | rev | cut -d : -f 2- | rev)
	if ! greylist update "$REMOTE_IP" "$MAIL_FROM" 1>&2; then
		echo "greylisted, please try again"
		exit 75  # temporary error
	fi
	echo "X-Greylist: pass"
fi


TF="$(mktemp --tmpdir post-data-XXXXXXXXXX)"
trap 'rm "$TF"' EXIT

# Save the message to the temporary file, so we can pass it on to the various
# filters.
cat > "$TF"


if command -v spamc >/dev/null; then
        if ! SL=$(spamc -c - < "$TF") ; then
                echo "spam detected"
                exit 20  # permanent
        fi
        echo "X-Spam-Score: $SL"
fi


if command -v rspamc >/dev/null; then
	ACTION=$( rspamc < "$TF" 2>/dev/null | grep Action: | cut -d " " -f 2- )
	case "$ACTION" in
		greylist)
			echo "greylisted, please try again"
			exit 75  # temporary error
			;;
		reject)
			echo "spam detected"
			exit 20  # permanent error
			;;
	esac
	echo "X-Spam-Action:" "$ACTION"
fi


if command -v clamdscan >/dev/null; then
        if ! clamdscan --no-summary --infected - < "$TF" 1>&2 ; then
                echo "virus detected"
                exit 20  # permanent
        fi
        echo "X-Virus-Scanned: pass"
fi

# DKIM sign with https://github.com/driusan/dkim.
#
# Do it only if all the following are true:
#  - User has authenticated.
#  - dkimsign binary exists.
#  - domains/$DOMAIN/dkim_selector file exists.
#  - certs/$DOMAIN/dkim_privkey.pem file exists.
#
# Note this has not been thoroughly tested, so might need further adjustments.
if [ "$AUTH_AS" != "" ] && command -v dkimsign; then
	DOMAIN=$( echo "$MAIL_FROM" | cut -d '@' -f 2 )
	if [ -f "domains/$DOMAIN/dkim_selector" ] \
			&& [ -f "certs/$DOMAIN/dkim_privkey.pem" ]; then
		dkimsign -n -hd \
			-key "certs/$DOMAIN/dkim_privkey.pem" \
			-s $(cat "domains/$DOMAIN/dkim_selector") \
			-d "$DOMAIN" \
			< "$TF"
	fi
fi
