Add ARP spoofing protection for LinuxBridge agent
This patch adds ARP spoofing protection for the Linux Bridge agent based on ebtables. This code was written to be minimally invasive with the intent of back-porting to Kilo. The protection is enabled and disabled with the same 'prevent_arp_spoofing' agent config flag added for the OVS agent in I7c079b779245a0af6bc793564fa8a560e4226afe. The protection works by setting up an ebtables chain for each port and jumping all ARP traffic to that chain. The port-specific chains have a default DROP policy and then have allow rules installed that only allow ARP traffic with a source CIDR that matches one of the port's fixed IPs or an allowed address pair. Closes-Bug: #1274034 Change-Id: I0b0e3b1272472385dff060897ecbd25e93fd78e7
This commit is contained in:
Kevin Benton
parent
9ba8b79a7c
commit
04197bc4bb
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# Copyright (c) 2015 Mirantis, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import netaddr
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from oslo_concurrency import lockutils
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from oslo_log import log as logging
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from neutron.agent.linux import ip_lib
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from neutron.i18n import _LI
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LOG = logging.getLogger(__name__)
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SPOOF_CHAIN_PREFIX = 'neutronARP-'
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def setup_arp_spoofing_protection(vif, port_details):
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current_rules = ebtables(['-L']).splitlines()
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if not port_details.get('port_security_enabled', True):
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# clear any previous entries related to this port
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delete_arp_spoofing_protection([vif], current_rules)
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LOG.info(_LI("Skipping ARP spoofing rules for port '%s' because "
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"it has port security disabled"), vif)
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return
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# collect all of the addresses and cidrs that belong to the port
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addresses = {f['ip_address'] for f in port_details['fixed_ips']}
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if port_details.get('allowed_address_pairs'):
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addresses |= {p['ip_address']
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for p in port_details['allowed_address_pairs']}
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addresses = {ip for ip in addresses
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if netaddr.IPNetwork(ip).version == 4}
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if any(netaddr.IPNetwork(ip).prefixlen == 0 for ip in addresses):
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# don't try to install protection because a /0 prefix allows any
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# address anyway and the ARP_SPA can only match on /1 or more.
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return
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install_arp_spoofing_protection(vif, addresses, current_rules)
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def chain_name(vif):
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# start each chain with a common identifer for cleanup to find
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return '%s%s' % (SPOOF_CHAIN_PREFIX, vif)
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@lockutils.synchronized('ebtables')
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def delete_arp_spoofing_protection(vifs, current_rules=None):
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if not current_rules:
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current_rules = ebtables(['-L']).splitlines()
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# delete the jump rule and then delete the whole chain
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jumps = [vif for vif in vifs if vif_jump_present(vif, current_rules)]
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for vif in jumps:
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ebtables(['-D', 'FORWARD', '-i', vif, '-j',
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chain_name(vif), '-p', 'ARP'])
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for vif in vifs:
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if chain_exists(chain_name(vif), current_rules):
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ebtables(['-X', chain_name(vif)])
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def delete_unreferenced_arp_protection(current_vifs):
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# deletes all jump rules and chains that aren't in current_vifs but match
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# the spoof prefix
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output = ebtables(['-L']).splitlines()
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to_delete = []
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for line in output:
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# we're looking to find and turn the following:
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# Bridge chain: SPOOF_CHAIN_PREFIXtap199, entries: 0, policy: DROP
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# into 'tap199'
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if line.startswith('Bridge chain: %s' % SPOOF_CHAIN_PREFIX):
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devname = line.split(SPOOF_CHAIN_PREFIX, 1)[1].split(',')[0]
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if devname not in current_vifs:
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to_delete.append(devname)
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LOG.info(_LI("Clearing orphaned ARP spoofing entries for devices %s"),
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to_delete)
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delete_arp_spoofing_protection(to_delete, output)
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@lockutils.synchronized('ebtables')
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def install_arp_spoofing_protection(vif, addresses, current_rules):
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# make a VIF-specific ARP chain so we don't conflict with other rules
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vif_chain = chain_name(vif)
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if not chain_exists(vif_chain, current_rules):
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ebtables(['-N', vif_chain, '-P', 'DROP'])
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# flush the chain to clear previous accepts. this will cause dropped ARP
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# packets until the allows are installed, but that's better than leaked
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# spoofed packets and ARP can handle losses.
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ebtables(['-F', vif_chain])
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for addr in addresses:
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ebtables(['-A', vif_chain, '-p', 'ARP', '--arp-ip-src', addr,
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'-j', 'ACCEPT'])
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# check if jump rule already exists, if not, install it
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if not vif_jump_present(vif, current_rules):
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ebtables(['-A', 'FORWARD', '-i', vif, '-j',
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vif_chain, '-p', 'ARP'])
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def chain_exists(chain, current_rules):
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for rule in current_rules:
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if rule.startswith('Bridge chain: %s' % chain):
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return True
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return False
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def vif_jump_present(vif, current_rules):
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searches = (('-i %s' % vif), ('-j %s' % chain_name(vif)), ('-p ARP'))
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for line in current_rules:
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if all(s in line for s in searches):
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return True
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return False
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# Used to scope ebtables commands in testing
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NAMESPACE = None
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def ebtables(comm):
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execute = ip_lib.IPWrapper(NAMESPACE).netns.execute
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return execute(['ebtables'] + comm, run_as_root=True)
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@ -66,6 +66,22 @@ agent_opts = [
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help=_("Set new timeout in seconds for new rpc calls after "
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"agent receives SIGTERM. If value is set to 0, rpc "
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"timeout won't be changed")),
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# TODO(kevinbenton): The following opt is duplicated between the OVS agent
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# and the Linuxbridge agent to make it easy to back-port. These shared opts
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# should be moved into a common agent config options location as part of
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# the deduplication work.
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cfg.BoolOpt('prevent_arp_spoofing', default=True,
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help=_("Enable suppression of ARP responses that don't match "
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"an IP address that belongs to the port from which "
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"they originate. Note: This prevents the VMs attached "
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"to this agent from spoofing, it doesn't protect them "
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"from other devices which have the capability to spoof "
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"(e.g. bare metal or VMs attached to agents without "
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"this flag set to True). Spoofing rules will not be "
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"added to any ports that have port security disabled. "
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"For LinuxBridge, this requires ebtables. For OVS, it "
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"requires a version that supports matching ARP "
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"headers."))
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]
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@ -47,6 +47,7 @@ from neutron.i18n import _LE, _LI, _LW
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from neutron.plugins.common import constants as p_const
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from neutron.plugins.ml2.drivers.l2pop.rpc_manager \
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import l2population_rpc as l2pop_rpc
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from neutron.plugins.ml2.drivers.linuxbridge.agent import arp_protect
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from neutron.plugins.ml2.drivers.linuxbridge.agent.common import config # noqa
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from neutron.plugins.ml2.drivers.linuxbridge.agent.common \
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import constants as lconst
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@ -768,6 +769,7 @@ class LinuxBridgeNeutronAgentRPC(service.Service):
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self.quitting_rpc_timeout = quitting_rpc_timeout
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def start(self):
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self.prevent_arp_spoofing = cfg.CONF.AGENT.prevent_arp_spoofing
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self.setup_linux_bridge(self.interface_mappings)
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configurations = {'interface_mappings': self.interface_mappings}
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if self.br_mgr.vxlan_mode != lconst.VXLAN_NONE:
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@ -895,6 +897,11 @@ class LinuxBridgeNeutronAgentRPC(service.Service):
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if 'port_id' in device_details:
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LOG.info(_LI("Port %(device)s updated. Details: %(details)s"),
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{'device': device, 'details': device_details})
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if self.prevent_arp_spoofing:
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port = self.br_mgr.get_tap_device_name(
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device_details['port_id'])
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arp_protect.setup_arp_spoofing_protection(port,
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device_details)
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if device_details['admin_state_up']:
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# create the networking for the port
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network_type = device_details.get('network_type')
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@ -948,6 +955,8 @@ class LinuxBridgeNeutronAgentRPC(service.Service):
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LOG.info(_LI("Port %s updated."), device)
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else:
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LOG.debug("Device %s not defined on plugin", device)
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if self.prevent_arp_spoofing:
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arp_protect.delete_arp_spoofing_protection(devices)
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return resync
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def scan_devices(self, previous, sync):
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@ -968,6 +977,10 @@ class LinuxBridgeNeutronAgentRPC(service.Service):
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'current': set(),
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'updated': set(),
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'removed': set()}
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# clear any orphaned ARP spoofing rules (e.g. interface was
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# manually deleted)
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if self.prevent_arp_spoofing:
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arp_protect.delete_unreferenced_arp_protection(current_devices)
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if sync:
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# This is the first iteration, or the previous one had a problem.
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@ -86,8 +86,9 @@ agent_opts = [
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"(e.g. bare metal or VMs attached to agents without "
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"this flag set to True). Spoofing rules will not be "
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"added to any ports that have port security disabled. "
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"This requires a version of OVS that supports matching "
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"ARP headers.")),
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"For LinuxBridge, this requires ebtables. For OVS, it "
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"requires a version that supports matching ARP "
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"headers.")),
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cfg.BoolOpt('dont_fragment', default=True,
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help=_("Set or un-set the don't fragment (DF) bit on "
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"outgoing IP packet carrying GRE/VXLAN tunnel.")),
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@ -76,19 +76,19 @@ class PeerMachines(fixtures.Fixture):
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:type machines: FakeMachine list
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"""
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AMOUNT = 2
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CIDR = '192.168.0.1/24'
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def __init__(self, bridge, ip_cidr=None, gateway_ip=None):
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def __init__(self, bridge, ip_cidr=None, gateway_ip=None, amount=2):
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super(PeerMachines, self).__init__()
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self.bridge = bridge
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self.ip_cidr = ip_cidr or self.CIDR
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self.gateway_ip = gateway_ip
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self.amount = amount
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def _setUp(self):
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self.machines = []
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for index in range(self.AMOUNT):
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for index in range(self.amount):
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ip_cidr = net_helpers.increment_ip_cidr(self.ip_cidr, index)
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self.machines.append(
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self.useFixture(
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@ -0,0 +1,100 @@
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# Copyright (c) 2015 Mirantis, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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from neutron.plugins.ml2.drivers.linuxbridge.agent import arp_protect
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from neutron.tests.common import machine_fixtures
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from neutron.tests.common import net_helpers
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from neutron.tests.functional import base as functional_base
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no_arping = net_helpers.assert_no_arping
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arping = net_helpers.assert_arping
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class LinuxBridgeARPSpoofTestCase(functional_base.BaseSudoTestCase):
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def setUp(self):
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super(LinuxBridgeARPSpoofTestCase, self).setUp()
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lbfixture = self.useFixture(net_helpers.LinuxBridgeFixture())
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self.addCleanup(setattr, arp_protect, 'NAMESPACE', None)
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arp_protect.NAMESPACE = lbfixture.namespace
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bridge = lbfixture.bridge
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self.source, self.destination, self.observer = self.useFixture(
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machine_fixtures.PeerMachines(bridge, amount=3)).machines
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def _add_arp_protection(self, machine, addresses, extra_port_dict=None):
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port_dict = {'fixed_ips': [{'ip_address': a} for a in addresses]}
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if extra_port_dict:
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port_dict.update(extra_port_dict)
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name = net_helpers.VethFixture.get_peer_name(machine.port.name)
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arp_protect.setup_arp_spoofing_protection(name, port_dict)
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self.addCleanup(arp_protect.delete_arp_spoofing_protection,
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[name])
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def test_arp_no_protection(self):
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arping(self.source.namespace, self.destination.ip)
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arping(self.destination.namespace, self.source.ip)
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def test_arp_correct_protection(self):
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self._add_arp_protection(self.source, [self.source.ip])
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self._add_arp_protection(self.destination, [self.destination.ip])
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arping(self.source.namespace, self.destination.ip)
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arping(self.destination.namespace, self.source.ip)
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def test_arp_fails_incorrect_protection(self):
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self._add_arp_protection(self.source, ['1.1.1.1'])
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self._add_arp_protection(self.destination, ['2.2.2.2'])
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no_arping(self.source.namespace, self.destination.ip)
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no_arping(self.destination.namespace, self.source.ip)
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def test_arp_protection_removal(self):
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self._add_arp_protection(self.source, ['1.1.1.1'])
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self._add_arp_protection(self.destination, ['2.2.2.2'])
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no_arping(self.observer.namespace, self.destination.ip)
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no_arping(self.observer.namespace, self.source.ip)
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name = net_helpers.VethFixture.get_peer_name(self.source.port.name)
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arp_protect.delete_arp_spoofing_protection([name])
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# spoofing should have been removed from source, but not dest
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arping(self.observer.namespace, self.source.ip)
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no_arping(self.observer.namespace, self.destination.ip)
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def test_arp_protection_update(self):
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self._add_arp_protection(self.source, ['1.1.1.1'])
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self._add_arp_protection(self.destination, ['2.2.2.2'])
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no_arping(self.observer.namespace, self.destination.ip)
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no_arping(self.observer.namespace, self.source.ip)
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self._add_arp_protection(self.source, ['192.0.0.0/1'])
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# spoofing should have been updated on source, but not dest
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arping(self.observer.namespace, self.source.ip)
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no_arping(self.observer.namespace, self.destination.ip)
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def test_arp_protection_port_security_disabled(self):
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self._add_arp_protection(self.source, ['1.1.1.1'])
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no_arping(self.observer.namespace, self.source.ip)
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self._add_arp_protection(self.source, ['1.1.1.1'],
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{'port_security_enabled': False})
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arping(self.observer.namespace, self.source.ip)
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def test_arp_protection_dead_reference_removal(self):
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self._add_arp_protection(self.source, ['1.1.1.1'])
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self._add_arp_protection(self.destination, ['2.2.2.2'])
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no_arping(self.observer.namespace, self.destination.ip)
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no_arping(self.observer.namespace, self.source.ip)
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name = net_helpers.VethFixture.get_peer_name(self.source.port.name)
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# This should remove all arp protect rules that aren't source port
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arp_protect.delete_unreferenced_arp_protection([name])
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no_arping(self.observer.namespace, self.source.ip)
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arping(self.observer.namespace, self.destination.ip)
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@ -89,6 +89,7 @@ class TestLinuxBridgeAgent(base.BaseTestCase):
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super(TestLinuxBridgeAgent, self).setUp()
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# disable setting up periodic state reporting
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cfg.CONF.set_override('report_interval', 0, 'AGENT')
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cfg.CONF.set_override('prevent_arp_spoofing', False, 'AGENT')
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cfg.CONF.set_default('firewall_driver',
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'neutron.agent.firewall.NoopFirewallDriver',
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group='SECURITYGROUP')
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