dotfiles/bin/nyfthon

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#!/usr/bin/env python3
from nftables import Nftables
from os import path
import sys
NFT = Nftables()
NAME = path.basename(__file__)
def error(message, code):
print("%s: %s" % (NAME, message), file = sys.stderr)
exit(code)
def error_no_arg(arg_name):
error("no %s provided" % (arg_name), 1)
def error_invalid_arg(arg_name, value):
error('invalid %s "%s"' % (arg_name, value), 2)
def allowed_ports(operation, protocol, port):
if operation != "add" and operation != "delete":
raise ValueError("not a valid nftables operation")
if protocol != "tcp" and protocol != "udp":
raise ValueError("not a valid protocol")
if port < 0 or port > 65535:
raise ValueError("not a valid port number")
NFT.cmd("%s element inet filter allowed_%s { %d }" % (operation, protocol, port))
def manage_ports(action, args):
match action:
case "allow":
operation = "add"
case "deny":
operation = "delete"
case _:
raise ValueError("invalid action")
try:
protocol = args.pop(0)
except IndexError:
error_no_arg("protocol")
try:
port = args.pop(0)
except IndexError:
error_no_arg("port")
try:
port = int(port)
except ValueError:
error_invalid_arg("port", port)
try:
allowed_ports(operation, protocol, port)
except ValueError as e:
error(e, 3)
if __name__ == "__main__":
sys.argv.pop(0)
try:
action = sys.argv.pop(0)
except IndexError:
error_no_arg("action")
match action:
case "help":
usage()
case "allow" | "deny":
manage_ports(action, sys.argv)
case _:
error_invalid_arg("action", action)