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# -*- coding: utf-8 -*-
# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from hashlib import sha256
from typing import List, Optional
import attr
from netaddr import IPSet
from ._base import Config, ConfigError
@attr.s
class ShardedFederationSendingConfig:
"""Algorithm for choosing which federation sender instance is responsible
for which destionation host.
"""
instances = attr.ib(type=List[str])
def should_send_to(self, instance_name: str, destination: str) -> bool:
"""Whether this instance is responsible for sending transcations for
the given host.
"""
# If multiple federation senders are not defined we always return true.
if not self.instances or len(self.instances) == 1:
return True
# We shard by taking the hash, modulo it by the number of federation
# senders and then checking whether this instance matches the instance
# at that index.
#
# (Technically this introduces some bias and is not entirely uniform, but
# since the hash is so large the bias is ridiculously small).
dest_hash = sha256(destination.encode("utf8")).digest()
dest_int = int.from_bytes(dest_hash, byteorder="little")
remainder = dest_int % (len(self.instances))
return self.instances[remainder] == instance_name
class FederationConfig(Config):
section = "federation"
def read_config(self, config, **kwargs):
# Whether to send federation traffic out in this process. This only
# applies to some federation traffic, and so shouldn't be used to
# "disable" federation
self.send_federation = config.get("send_federation", True)
federation_sender_instances = config.get("federation_sender_instances") or []
self.federation_shard_config = ShardedFederationSendingConfig(
federation_sender_instances
)
# FIXME: federation_domain_whitelist needs sytests
self.federation_domain_whitelist = None # type: Optional[dict]
federation_domain_whitelist = config.get("federation_domain_whitelist", None)
if federation_domain_whitelist is not None:
# turn the whitelist into a hash for speed of lookup
self.federation_domain_whitelist = {}
for domain in federation_domain_whitelist:
self.federation_domain_whitelist[domain] = True
self.federation_ip_range_blacklist = config.get(
"federation_ip_range_blacklist", []
)
# Attempt to create an IPSet from the given ranges
try:
self.federation_ip_range_blacklist = IPSet(
self.federation_ip_range_blacklist
)
# Always blacklist 0.0.0.0, ::
self.federation_ip_range_blacklist.update(["0.0.0.0", "::"])
except Exception as e:
raise ConfigError(
"Invalid range(s) provided in federation_ip_range_blacklist: %s" % e
)
def generate_config_section(self, config_dir_path, server_name, **kwargs):
return """\
# Restrict federation to the following whitelist of domains.
# N.B. we recommend also firewalling your federation listener to limit
# inbound federation traffic as early as possible, rather than relying
# purely on this application-layer restriction. If not specified, the
# default is to whitelist everything.
#
#federation_domain_whitelist:
# - lon.example.com
# - nyc.example.com
# - syd.example.com
# Prevent federation requests from being sent to the following
# blacklist IP address CIDR ranges. If this option is not specified, or
# specified with an empty list, no ip range blacklist will be enforced.
#
# As of Synapse v1.4.0 this option also affects any outbound requests to identity
# servers provided by user input.
#
# (0.0.0.0 and :: are always blacklisted, whether or not they are explicitly
# listed here, since they correspond to unroutable addresses.)
#
federation_ip_range_blacklist:
- '127.0.0.0/8'
- '10.0.0.0/8'
- '172.16.0.0/12'
- '192.168.0.0/16'
- '100.64.0.0/10'
- '169.254.0.0/16'
- '::1/128'
- 'fe80::/64'
- 'fc00::/7'
"""
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