Add './unrealircd spkifp' which will output the SPKI fingerprint

along with the exact password section to use in the link block
on the other side of the link.
Also used in tutorial now at
https://www.unrealircd.org/docs/Tutorial:_Linking_servers

unrealircd.in

@@ -205,6 +205,30 @@ __EOF__
 	echo '   all the time so your bug might as well be fixed already.'
 	echo ""
 	echo "Thanks!"
+elif [ "$1" = "spki" -o "$1" = "spkifp" ] ; then
+	cd @TMPDIR@ || exit 1
+	CERT="@CONFDIR@/ssl/server.cert.pem"
+	if [ "$2" != "" ]; then
+		CERT="$2"
+	fi
+	if [ ! -f "$CERT" ]; then
+		echo "Could not open certificate: $CERT"
+		exit 1
+	fi
+	openssl x509 -noout -in "$CERT" -pubkey | openssl asn1parse -noout -inform pem -out tmp.public.key
+	HASH="`openssl dgst -sha256 -binary tmp.public.key | openssl enc -base64`"
+	rm -f tmp.public.key
+	if [ "$HASH" = "" ]; then
+		echo "Sorry, something went wrong when generating the SPKI fingerprint."
+		echo "Is the 'openssl' tool properly installed?"
+		exit 1
+	fi
+	echo "The SPKI fingerprint for certificate $CERT is:"
+	echo "$HASH"
+	echo ""
+	echo "You normally add this password on the other side of the link as:"
+	echo "password \"$HASH\" { spkifp; };"
+	echo ""
 else
-	echo "Usage: unrealircd start|stop|rehash|restart|mkpasswd|version|croncheck|gencloak|reloadtls|upgrade-conf"
+	echo "Usage: unrealircd start|stop|rehash|restart|mkpasswd|version|croncheck|gencloak|reloadtls|spkifp|upgrade-conf"
 fi