627 lines
16 KiB
Python
Executable file
627 lines
16 KiB
Python
Executable file
#!/usr/bin/env python3
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from argparse import ArgumentParser, FileType
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from dataclasses import dataclass
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from enum import Enum
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from graphlib import TopologicalSorter
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from ipaddress import IPv4Network, IPv6Network
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from nftables import Nftables
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from pydantic import (
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BaseModel,
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Extra,
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FilePath,
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IPvAnyNetwork,
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ValidationError,
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conint,
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parse_obj_as,
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validator,
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root_validator,
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)
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from typing import Iterator, Generic, TypeAlias, TypeVar
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from yaml import safe_load
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import nft
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# ==========[ PYDANTIC ]========================================================
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T = TypeVar("T")
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class AutoSet(set[T], Generic[T]):
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@classmethod
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def __get_validators__(cls):
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yield cls.__validator__
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@classmethod
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def __validator__(cls, value):
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try:
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return parse_obj_as(set[T], value)
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except ValidationError:
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return {parse_obj_as(T, value)}
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class RestrictiveBaseModel(BaseModel):
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class Config:
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allow_mutation = False
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extra = Extra.forbid
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# ==========[ YAML MODEL ]======================================================
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# Ports
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Port: TypeAlias = conint(ge=0, lt=2**16)
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class PortRange(str):
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@classmethod
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def __get_validators__(cls):
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yield cls.validate
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@classmethod
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def validate(cls, v):
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try:
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start, end = v.split("..")
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except AttributeError:
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parse_obj_as(Port, v) # This is the expected error
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raise ValueError(
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"invalid port range: must be in the form start..end"
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)
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except ValueError:
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raise ValueError(
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"invalid port range: must be in the form start..end"
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)
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start, end = parse_obj_as(Port, start), parse_obj_as(Port, end)
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if start > end:
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raise ValueError("invalid port range: start must be less than end")
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return range(start, end)
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# Zones
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ZoneName: TypeAlias = str
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class ZoneEntry(RestrictiveBaseModel):
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addrs: AutoSet[IPvAnyNetwork] = AutoSet()
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file: FilePath | None = None
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negate: bool = False
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zones: AutoSet[ZoneName] = AutoSet()
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@root_validator()
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def validate_mutually_exactly_one(cls, values):
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fields = ["addrs", "file", "zones"]
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if sum(1 for field in fields if values.get(field)) != 1:
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raise ValueError(f"exactly one of {fields} must be set")
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return values
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# Blacklist
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class Blacklist(RestrictiveBaseModel):
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blocked: AutoSet[IPvAnyNetwork | ZoneName] = AutoSet()
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# Reverse Path Filter
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class ReversePathFilter(RestrictiveBaseModel):
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interfaces: AutoSet[str] = AutoSet()
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# Filters
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class Verdict(str, Enum):
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accept = "accept"
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drop = "drop"
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reject = "reject"
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class TcpProtocol(RestrictiveBaseModel):
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dport: AutoSet[Port | PortRange] = AutoSet()
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sport: AutoSet[Port | PortRange] = AutoSet()
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def __bool__(self):
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return bool(self.sport or self.dport)
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def __getitem__(self, key):
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return getattr(self, key)
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class UdpProtocol(RestrictiveBaseModel):
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dport: AutoSet[Port | PortRange] = AutoSet()
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sport: AutoSet[Port | PortRange] = AutoSet()
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def __bool__(self):
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return bool(self.sport or self.dport)
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def __getitem__(self, key):
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return getattr(self, key)
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class Protocols(RestrictiveBaseModel):
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icmp: bool = False
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ospf: bool = False
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tcp: TcpProtocol = TcpProtocol()
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udp: UdpProtocol = UdpProtocol()
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vrrp: bool = False
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def __getitem__(self, key):
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return getattr(self, key)
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class Rule(RestrictiveBaseModel):
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iif: str | None
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oif: str | None
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protocols: Protocols = Protocols()
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src: AutoSet[IPvAnyNetwork | ZoneName] | None
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dst: AutoSet[IPvAnyNetwork | ZoneName] | None
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verdict: Verdict = Verdict.accept
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class Filter(RestrictiveBaseModel):
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input: list[Rule] = list()
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output: list[Rule] = list()
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forward: list[Rule] = list()
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# Nat
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class SNat(RestrictiveBaseModel):
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addr: IPvAnyNetwork
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persistent: bool = True
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class Nat(RestrictiveBaseModel):
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src: ZoneName
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snat: SNat
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# Root model
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class Firewall(RestrictiveBaseModel):
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zones: dict[ZoneName, ZoneEntry] = dict()
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blacklist: Blacklist = Blacklist()
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reverse_path_filter: ReversePathFilter = ReversePathFilter()
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filter: Filter = Filter()
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nat: list[Nat] = list()
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# ==========[ ZONES ]===========================================================
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class ZoneFile(RestrictiveBaseModel):
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__root__: AutoSet[IPvAnyNetwork]
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@dataclass
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class ResolvedZone:
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addrs: set[IPvAnyNetwork]
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negate: bool
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Zones: TypeAlias = dict[ZoneName, ResolvedZone]
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def resolve_zones(yaml_zones: dict[ZoneName, ZoneEntry]) -> Zones:
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zones: Zones = {}
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zone_graph = {name: entry.zones for (name, entry) in yaml_zones.items()}
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for name in TopologicalSorter(zone_graph).static_order():
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if yaml_zones[name].addrs:
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zones[name] = ResolvedZone(
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yaml_zones[name].addrs, yaml_zones[name].negate
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)
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elif yaml_zones[name].file is not None:
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with open(yaml_zones[name].file, "r") as file:
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try:
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yaml_addrs = ZoneFile(__root__=safe_load(file))
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except Exception as e:
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raise Exception(
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f"YAML parsing of the included file '{yaml_zones[name].file}' failed: {e}"
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)
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zones[name] = ResolvedZone(
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yaml_addrs.__root__, yaml_zones[name].negate
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)
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elif yaml_zones[name].zones:
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addrs: set[IPvAnyNetwork] = set()
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for zone in yaml_zones[name].zones:
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addrs.update(yaml_zones[zone].addrs)
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zones[name] = ResolvedZone(addrs, yaml_zones[name].negate)
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return zones
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# ==========[ PARSER ]==========================================================
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def unmarshall_ports(elements: set[Port | PortRange]) -> Iterator[int]:
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for element in elements:
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if isinstance(element, int):
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yield element
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if isinstance(element, range):
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yield from element
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def split_v4_v6(
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addrs: Iterator[IPvAnyNetwork],
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) -> tuple[set[nft.Immediate[IPv4Network]], set[nft.Immediate[IPv6Network]]]:
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v4, v6 = set(), set()
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for addr in addrs:
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match addr:
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case IPv4Network():
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v4.add(nft.Immediate(addr))
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case IPv6Network():
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v6.add(nft.Immediate(addr))
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return v4, v6
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def zones_into_ip(
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elements: set[IPvAnyNetwork | ZoneName],
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zones: Zones,
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allow_negate: bool = True,
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) -> Iterator[IPvAnyNetwork]:
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for element in elements:
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match element:
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case ZoneName():
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try:
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zone = zones[element]
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except KeyError:
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raise ValueError(f"zone '{element}' does not exist")
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if not allow_negate and zone.negate:
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raise ValueError(f"zone '{element}' cannot be negated")
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yield from zone.addrs
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case IPv4Network() | IPv6Network():
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yield element
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def parse_blacklist(blacklist: Blacklist, zones: Zones) -> nft.Table:
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# Sets blacklist_v4 and blacklist_v6
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set_v4 = nft.Set(name="blacklist_v4", type="ipv4_addr", flags=["interval"])
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set_v6 = nft.Set(name="blacklist_v6", type="ipv6_addr", flags=["interval"])
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ip_v4, ip_v6 = split_v4_v6(
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zones_into_ip(blacklist.blocked, zones, allow_negate=False)
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)
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set_v4.elements.extend(ip_v4)
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set_v6.elements.extend(ip_v6)
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# Chain filter
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chain_filter = nft.Chain(
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name="filter",
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type="filter",
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hook="prerouting",
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policy="accept",
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priority=-310,
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)
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rule_v4 = nft.Match(
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op="==",
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left=nft.Payload(protocol="ip", field="saddr"),
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right=nft.Immediate("@blacklist_v4"),
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)
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rule_v6 = nft.Match(
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op="==",
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left=nft.Payload(protocol="ip6", field="saddr"),
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right=nft.Immediate("@blacklist_v6"),
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)
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chain_filter.rules.append(nft.Rule([rule_v4, nft.Verdict("drop")]))
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chain_filter.rules.append(nft.Rule([rule_v6, nft.Verdict("drop")]))
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# Resulting table
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table = nft.Table(name="blacklist", family="inet")
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table.chains.extend([chain_filter])
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table.sets.extend([set_v4, set_v6])
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return table
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def parse_reverse_path_filter(rpf: ReversePathFilter) -> nft.Table:
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# Set disabled_ifs
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disabled_ifs = nft.Set(name="disabled_ifs", type="ifname")
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disabled_ifs.elements.extend(map(nft.Immediate, rpf.interfaces))
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# Chain filter
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chain_filter = nft.Chain(
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name="filter",
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type="filter",
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hook="prerouting",
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policy="accept",
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priority=-300,
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)
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rule_iifname = nft.Match(
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op="!=",
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left=nft.Meta("iifname"),
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right=nft.Immediate("@disabled_ifs"),
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)
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rule_fib = nft.Match(
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op="==",
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left=nft.Fib(flags=["saddr", "iif"], result="oif"),
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right=nft.Immediate(False),
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)
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rule_pkttype = nft.Match(
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op="==",
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left=nft.Meta("pkttype"),
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right=nft.Immediate("host"),
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)
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chain_filter.rules.append(
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nft.Rule([rule_iifname, rule_fib, rule_pkttype, nft.Verdict("drop")])
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)
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# Resulting table
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table = nft.Table(name="reverse_path_filter", family="inet")
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table.chains.extend([chain_filter])
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table.sets.extend([disabled_ifs])
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return table
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class InetRuleBuilder:
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def __init__(self):
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self._v4 = []
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self._v6 = []
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def add_any(self, match):
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self.add_v4(match)
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self.add_v6(match)
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def add_v4(self, match):
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if self._v4 is not None:
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self._v4.append(match)
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def add_v6(self, match):
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if self._v6 is not None:
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self._v6.append(match)
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def disable_v4(self):
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self._v4 = None
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def disable_v6(self):
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self._v6 = None
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@property
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def rules(self):
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print(self._v4)
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if self._v4 is not None:
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yield nft.Rule(self._v4)
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if self._v6 is not None and self._v6 != self._v4:
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yield nft.Rule(self._v6)
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def parse_filter_rule(rule: Rule, zones: Zones) -> list[nft.Rule]:
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builder = InetRuleBuilder()
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for attr in ("iif", "oif"):
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if getattr(rule, attr, None) is not None:
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builder.add_any(
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nft.Match(
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op="==",
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left=nft.Meta(f"{attr}name"),
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right=nft.Immediate(getattr(rule, attr)),
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)
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)
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for attr, field in (("src", "saddr"), ("dst", "daddr")):
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if getattr(rule, attr, None) is not None:
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addr_v4, addr_v6 = split_v4_v6(
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zones_into_ip(getattr(rule, attr), zones)
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)
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if addr_v4:
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builder.add_v4(
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nft.Match(
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op="==",
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left=nft.Payload(protocol="ip", field=field),
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right=nft.Immediate(addr_v4),
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)
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)
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else:
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builder.disable_v4()
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if addr_v6:
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builder.add_v6(
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nft.Match(
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op="==",
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left=nft.Payload(protocol="ip6", field=field),
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right=nft.Immediate(addr_v6),
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)
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)
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else:
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builder.disable_v6()
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protos = {
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"icmp": ("icmp", "icmpv6"),
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"ospf": (89, 89),
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"vrrp": (112, 112),
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"tcp": ("tcp", "tcp"),
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"udp": ("udp", "udp"),
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}
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protos_v4 = {
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v for p, (v, _) in protos.items() if getattr(rule.protocols, p)
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}
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protos_v6 = {
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v for p, (_, v) in protos.items() if getattr(rule.protocols, p)
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}
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if protos_v4:
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builder.add_v4(
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nft.Match(
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op="==",
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left=nft.Payload(protocol="ip", field="protocol"),
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right=nft.Immediate(protos_v4),
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)
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)
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if protos_v6:
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builder.add_v6(
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nft.Match(
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op="==",
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left=nft.Payload(protocol="ip6", field="nexthdr"),
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right=nft.Immediate(protos_v6),
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)
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)
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proto_ports = (
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("udp", "dport"),
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("udp", "sport"),
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("tcp", "dport"),
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("tcp", "sport"),
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)
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for proto, port in proto_ports:
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if rule.protocols[proto][port]:
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ports = set(unmarshall_ports(rule.protocols[proto][port]))
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builder.add_any(
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nft.Match(
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op="==",
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left=nft.Payload(protocol=proto, field=port),
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right=nft.Immediate(ports),
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),
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)
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builder.add_any(nft.Verdict(rule.verdict.value))
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return builder.rules
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# Create a chain "{hook}_filter" and for each rule from the DSL:
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# - Create a specific chain "{hook}_rules_{i}"
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# - If needed, add a network range in the set "{hook}_set_{i}"
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# - Add a rule to "input_filter" that jumps to chain "{hook}_rules_{i}"
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def parse_filter_rules(
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hook: str, rules: list[Rule], zones: Zones
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) -> nft.Chain:
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chain = nft.Chain(
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name=hook,
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type="filter",
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hook=hook,
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policy="drop", # TODO: Correct default policy
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priority=0,
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)
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chain.rules.append(nft.Rule([nft.Jump("conntrack")]))
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for rule in rules:
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chain.rules.extend(list(parse_filter_rule(rule, zones)))
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return chain
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def parse_filter(filter: Filter, zones: Zones) -> nft.Table:
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# Conntrack
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chain_conntrack = nft.Chain(name="conntrack")
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rule_ct_accept = nft.Match(
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op="==",
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left=nft.Ct("state"),
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right=nft.Immediate({"established", "related"}),
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)
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rule_ct_drop = nft.Match(
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op="in",
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left=nft.Ct("state"),
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right=nft.Immediate("invalid"),
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)
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chain_conntrack.rules = [
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nft.Rule([rule_ct_accept, nft.Verdict("accept")]),
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nft.Rule([rule_ct_drop, nft.Counter(), nft.Verdict("drop")]),
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]
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# Resulting table
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table = nft.Table(name="filter", family="inet")
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table.chains.append(chain_conntrack)
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# Input/Output/Forward chains
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for name in ("input", "output", "forward"):
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chain = parse_filter_rules(name, getattr(filter, name), zones)
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table.chains.append(chain)
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return table
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def parse_firewall(firewall: Firewall, zones: Zones) -> nft.Ruleset:
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# Tables
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blacklist = parse_blacklist(firewall.blacklist, zones)
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rpf = parse_reverse_path_filter(firewall.reverse_path_filter)
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filter = parse_filter(firewall.filter, zones)
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# Resulting ruleset
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ruleset = nft.Ruleset(flush=True)
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ruleset.tables.extend([blacklist, rpf, filter])
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return ruleset
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# ==========[ MAIN ]============================================================
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def send_to_nftables(cmd: nft.JsonNftables) -> int:
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nft = Nftables()
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try:
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nft.json_validate(cmd)
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except Exception as e:
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print(f"JSON validation failed: {e}")
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return 1
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rc, output, error = nft.json_cmd(cmd)
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if rc != 0:
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print(f"nft returned {rc}: {error}")
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return 1
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if len(output):
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print(output)
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return 0
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def main() -> int:
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parser = ArgumentParser()
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parser.add_argument("file", type=FileType("r"), help="YAML rule file")
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args = parser.parse_args()
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try:
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firewall = Firewall(**safe_load(args.file))
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except Exception as e:
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print(f"YAML parsing failed of the file '{args.file.name}': {e}")
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return 1
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try:
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zones = resolve_zones(firewall.zones)
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except Exception as e:
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print(f"Zone resolution failed: {e}")
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return 1
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try:
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json = parse_firewall(firewall, zones)
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except Exception as e:
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print(f"Firewall translation failed: {e}")
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return 1
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return send_to_nftables(json.to_nft())
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if __name__ == "__main__":
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exit(main())
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