Internet DRAFT - draft-gont-opsec-ipv6-eh-filtering
draft-gont-opsec-ipv6-eh-filtering
opsec F. Gont
Internet-Draft UTN-FRH / SI6 Networks
Intended status: Best Current Practice W. Liu
Expires: February 27, 2015 Huawei Technologies
R. Bonica
Juniper Networks
August 26, 2014
Recommendations on Filtering of IPv6 Packets Containing IPv6 Extension
Headers
draft-gont-opsec-ipv6-eh-filtering-02.txt
Abstract
This document provides advice on the filtering of IPv6 packets based
on the IPv6 Extension Headers and the IPv6 options they contain.
Additionally, it discusses the operational and interoperability
implications of discarding packets based on the IPv6 Extension
Headers and IPv6 options they contain.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 27, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
Gont, et al. Expires February 27, 2015 [Page 1]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Conventions Used in This Document . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
3. IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . 4
3.1. General Discussion . . . . . . . . . . . . . . . . . . . 4
3.2. General Security Implications . . . . . . . . . . . . . . 5
3.3. Advice on the Handling of IPv6 Packets with Specific IPv6
Extension Headers . . . . . . . . . . . . . . . . . . . . 5
3.4. Advice on the Handling of Packets with Unknown IPv6
Extension Headers . . . . . . . . . . . . . . . . . . . . 13
4. IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. General Discussion . . . . . . . . . . . . . . . . . . . 14
4.2. General Security Implications of IPv6 Options . . . . . . 14
4.3. Advice on the Handling of Packets with Specific IPv6
Options . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.4. Advice on the handling of Packets with Unknown IPv6
Options . . . . . . . . . . . . . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1. Normative References . . . . . . . . . . . . . . . . . . 26
8.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
Recent studies (see e.g.[I-D.gont-v6ops-ipv6-ehs-in-real-world])
suggest that there is widespread filtering of IPv6 packets that
contain IPv6 Extension Headers (EHs). While some operators
"officially" filter packets that contain IPv6 extension headers, it
is possible that some of the measured packet drops be the result of
improper configuration defaults, or inappropriate advice in this
area.
This document discusses the filtering of IPv6 packets based on the
IPv6 Extension Headers and the IPv6 options they contain. Since
various protocols may use IPv6 Extension Headers (possibly with IPv6
options), discarding packets based on the IPv6 Extension Headers or
IPv6 options they contain may have implications on the proper
Gont, et al. Expires February 27, 2015 [Page 2]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
functioning of such protocols. Thus, this document attempts to
discuss the operational and interoperability implications of such
filtering policies, and provide advice in this area. This document
is similar in nature to [RFC7126], which addresses the same problem
for the IPv4 case.
Section 2 of this document specifies the terminology and conventions
employed throughout this document. Section 3 of this document
discusses IPv6 extension headers and provides advice in the area of
filtering IPv6 packets that contain such IPv6 Extension Headers.
Section 4 of this document discusses IPv6 options and provides advice
in the area of filtering IPv6 packets that contain such options.
2. Terminology and Conventions Used in This Document
2.1. Terminology
The terms "fast path", "slow path", and associated relative terms
("faster path" and "slower path") are loosely defined as in Section 2
of [RFC6398].
The terms "permit" (allow the traffic), "drop" (drop with no
notification to sender), and "reject" (drop with appropriate
notification to sender) are employed as defined in [RFC3871].
Throughout this document we also employ the term "discard" as a
generic term to indicate the act of discarding a packet, irrespective
of whether the sender is notified of such drops.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2.2. Conventions
This document assumes that nodes comply with the requirements in
[RFC7045]. Namely (from [RFC7045]),
o If a forwarding node discards a packet containing a standard IPv6
extension header, it MUST be the result of a configurable policy
and not just the result of a failure to recognise such a header.
o The discard policy for each standard type of extension header MUST
be individually configurable.
o The default configuration SHOULD allow all standard extension
headers.
Gont, et al. Expires February 27, 2015 [Page 3]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
The advice provided in this document is only meant to guide an
operator in configuring forwarding devices, and is *not* to be
interpreted as advice regarding default configuration settings for
network devices. That is, this document provides advice with respect
to operational configurations, but does not change the implementation
defaults required by [RFC7045] and
[draft-gont-6man-ipv6-opt-transmit].
We recommend that a configuration option is made available to govern
the processing of each IPv6 Extension Header type and each IPv6
option type. Such configuration options may include the following
possible settings:
o Permit this IPv6 Extension Header or IPv6 Option type
o Drop (and log) packets containing this IPv6 Extension Header or
option type
o Reject (and log) packets containing this IPv6 Extension Header or
option type (where the packet drop is signaled with an ICMPv6
error message)
o Rate-limit the processing of packets containing this IPv6
Extension Header or option type
o Ignore this IPv6 Extension Header or option type (forwarding
packets that contain them)
We note that special care needs to be taken when devices log packet
drops/rejects. Devices should count the number of packets dropped/
rejected, but the logging of drop/reject events should be limited so
as to not overburden device resources.
Finally, we note that when discarding packets, it is generally
desirable that the sender be signaled of the packet drop, since this
is of use for trouble-shooting purposes. However, throughout this
document (when recommending that packets be discarded) we generically
refer to the action as "discard" without specifying whether the
sender is signaled of the packet drop.
3. IPv6 Extension Headers
3.1. General Discussion
IPv6 [RFC2460] Extension Headers allow for the extension of the IPv6
protocol. Since both IPv6 Extension Headers and upper-layer
protocols share the same namespace ("Next Header" registry/
namespace), [RFC7045] identifies which of the currently assigned
Gont, et al. Expires February 27, 2015 [Page 4]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
Internet Protocol numbers identify IPv6 Extension Headers vs. upper-
layer protocols. This document discusses the filtering of packets
based on the IPv6 Extension Headers (as specified by [RFC7045]) they
contain.
NOTE: [RFC7112] specifies that non-fragmented IPv6 datagrams and
IPv6 First-Fragments MUST contain the entire IPv6 header chain
[RFC7112]. Therefore, intermediate systems can always enforce the
filtering policies discussed in this document, or resort to simply
discarding the offending packets when they fail to comply with the
requirements in [RFC7112].
3.2. General Security Implications
Depending on the specific device architecture, IPv6 packets that
contain IPv6 Extension Headers may cause the corresponding packets to
be processed on the slow path, and hence may be leveraged for the
purpose of Denial of Service (DoS) attacks [Cisco-EH] [FW-Benchmark].
Operators are urged to consider IPv6 Extension Header filtering and
IPv6 options handling capabilities of different devices as they make
deployment decisions in future.
3.3. Advice on the Handling of IPv6 Packets with Specific IPv6
Extension Headers
3.3.1. IPv6 Hop-by-Hop Options (Protocol Number=0)
3.3.1.1. Uses
The Hop-by-Hop Options header is used to carry optional information
that should be examined by every node along a packet's delivery path.
3.3.1.2. Specification
This Extension Header is specified in [RFC2460], and its processing
rules have been updated by [RFC7045]. At the time of this writing,
the following options have been specified for the Hop-by-Hop Options
extension header:
o Type 0x05: Router Alert [RFC2711]
o Type 0xC2: Jumbo Payload [RFC2675]
o Type 0x63: RPL Option [RFC6553]
o Type 0x08: SMF_DPD [RFC6621]
Gont, et al. Expires February 27, 2015 [Page 5]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
o Type 0x6D: MPL Option [I-D.ietf-roll-trickle-mcast]
o Type 0xEE: IPv6 DFF Header [RFC6971]
o Type 0x26: Quick-Start [RFC4782]
o Type 0x07: CALIPSO [RFC5570]
3.3.1.3. Specific Security Implications
Since this Extension Header should be processed by all intermediate-
systems en route, it can be leveraged to perform Denial of Service
attacks against the network infrastructure.
3.3.1.4. Operational and Interoperability Impact if Blocked
Discarding packets containing a Hop-by-Hop Option extension header
would break any of the protocols that rely on it for proper
functioning. For example, it would break RSVP [RFC2205] and
multicast deployments, and would cause IPv6 jumbograms to be
discarded.
3.3.1.5. Advice
The recommended configuration for the processing of these packets
depends on the features and capabilities of the underlying platform.
On platforms that allow forwarding of packets with HBH Options on the
fast path, we recommend that packets with a HBH Options extension
header be forwarded as normal (for instance, [RFC7045] allows for
implementations to ignore the HBH Options extension header when
forwarding packets). Otherwise, on platforms in which processing of
packets with a IPv6 HBH Options extension header is carried out in
the slow path, and an option is provided to rate-limit these packets,
we recommend that this option be selected. Finally, when packets
containing a HBH Options extension header are processed in the slow-
path, and the underlying platform does not have any mitigation
options available for attacks based on these packets, we recommend
that such platforms discard packets containing IPv6 HBH Options
extension headers.
Finally, we note that, for obvious reasons, RPL (Routing Protocol for
Low-Power and Lossy Networks) [RFC6550] routers must not discard
packets based on the presence of an IPv6 Hop-by-Hop Options Extension
Header.
Gont, et al. Expires February 27, 2015 [Page 6]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.2. Routing Header for IPv6 (Protocol Number=43)
3.3.2.1. Uses
The Routing header is used by an IPv6 source to list one or more
intermediate nodes to be "visited" on the way to a packet's
destination.
3.3.2.2. Specification
This Extension Header is specified in [RFC2460]. [RFC2460]
originally specified the Routing Header Type 0, which has been later
obsoleted by [RFC5095].
At the time of this writing, the following Routing Types have been
specified:
o Type 0: Source Route (DEPRECATED) [RFC2460] [RFC5095]
o Type 1: Nimrod (DEPRECATED)
o Type 2: Type 2 Routing Header [RFC6275]
o Type 3: RPL Source Route Header [RFC6554]
o Types 4-252: Unassigned
o Type 253: RFC3692-style Experiment 1 [RFC4727]
o Type 254: RFC3692-style Experiment 2 [RFC4727]
o Type 255: Reserved
3.3.2.3. Specific Security Implications
The security implications of RHT0 have been discussed in detail in
[Biondi2007] and [RFC5095].
3.3.2.4. Operational and Interoperability Impact if Blocked
Blocking packets containing a RHT0 or RTH1 has no operational
implications. However, blocking packets employing other routing
header types will break the protocols that rely on them.
Gont, et al. Expires February 27, 2015 [Page 7]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.2.5. Advice
Intermediate systems should discard packets containing a RHT0 or
RHT1. As required by [RFC7045], packets containing standardised and
undeprecated Routing Headers should be permitted.
3.3.3. Fragment Header for IPv6 (Protocol Number=44)
3.3.3.1. Uses
This Extension Header provides the fragmentation functionality for
IPv6.
3.3.3.2. Specification
This Extension Header is specified in [RFC2460].
3.3.3.3. Specific Security Implications
The security implications of the Fragment Header range from Denial of
Service attacks (e.g. based on flooding a target with IPv6 fragments)
to information leakage attacks
[I-D.ietf-6man-predictable-fragment-id].
3.3.3.4. Operational and Interoperability Impact if Blocked
Blocking packets that contain a Fragment Header will break any
protocol that may rely on fragmentation (e.g., the DNS [RFC1034]).
3.3.3.5. Advice
Intermediate systems should permit packets that contain a Fragment
Header.
3.3.4. Encapsulating Security Payload (Protocol Number=50)
3.3.4.1. Uses
This extension Header is employed for the IPsec suite [RFC4303].
3.3.4.2. Specification
This extension header is specified in [RFC4303].
Gont, et al. Expires February 27, 2015 [Page 8]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.4.3. Specific Security Implications
Besides the general implications of IPv6 Extension Headers, this
extension header could be employed to potentially perform a DoS
attack at the destination system by wasting CPU resources in
validating the contents of the packet.
3.3.4.4. Operational and Interoperability Impact if Blocked
Discarding packets that employ this extension header would break
IPsec deployments.
3.3.4.5. Advice
Intermediate systems should permit packets containing the
Encapsulating Security Payload extension header.
3.3.5. Authentication Header (Number=51)
3.3.5.1. Uses
The Authentication Header can be employed for provide authentication
services in IPv4 and IPv6.
3.3.5.2. Specification
This Extension Header is specified in [RFC4302].
3.3.5.3. Specific Security Implications
Besides the general implications of IPv6 Extension Headers, this
extension header could be employed to potentially perform a DoS
attack at the destination system by wasting CPU resources in
validating the contents of the packet.
3.3.5.4. Operational and Interoperability Impact if Blocked
Discarding packets that employ this extension header would break
IPsec deployments.
3.3.5.5. Advice
Intermediate systems should permit packets containing an
Authentication Header.
Gont, et al. Expires February 27, 2015 [Page 9]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.6. Destination Options for IPv6 (Protocol Number=60)
3.3.6.1. Uses
The Destination Options header is used to carry optional information
that needs be examined only by a packet's destination node(s).
3.3.6.2. Specification
This Extension Header is specified in [RFC2460]. At the time of this
writing, the following options have been specified for this extension
header:
o Type 0x04: Tunnel Encapsulation Limit [RFC2473]
o Type 0xC9: Home Address [RFC6275]
o Type 0x8B: ILNP Nonce [RFC6744]
o Type 0x8C: Line-Identification Option [RFC6788]
3.3.6.3. Specific Security Implications
No security implications are known, other than the general
implications of IPv6 extension headers.
3.3.6.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain a Destination Options header would
break protocols that rely on this EH type for conveying information,
including protocols such as ILNP [RFC6740] and Mobile IPv6 [RFC6275],
and IPv6 tunnels that employ the Tunnel Encapsulation Limit option.
3.3.6.5. Advice
Intermediate systems should permit packets that contain a Destination
Options Header.
3.3.7. Mobility Header (Number=135)
3.3.7.1. Uses
The Mobility Header is an extension header used by mobile nodes,
correspondent nodes, and home agents in all messaging related to the
creation and management of bindings in Mobile IPv6.
Gont, et al. Expires February 27, 2015 [Page 10]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.7.2. Specification
This Extension Header is specified in [RFC6275].
3.3.7.3. Specific Security Implications
TBD.
3.3.7.4. Operational and Interoperability Impact if Blocked
Discarding packets containing this extension header would break
Mobile IPv6.
3.3.7.5. Advice
Intermediate systems should permit packets containing this extension
header.
3.3.8. Host Identity Protocol (Protocol Number=139)
3.3.8.1. Uses
This extension header is employed with the Host Identity Protocol
(HIP), an experimental protocol that allows consenting hosts to
securely establish and maintain shared IP-layer state, allowing
separation of the identifier and locator roles of IP addresses,
thereby enabling continuity of communications across IP address
changes.
3.3.8.2. Specification
This extension Header is specified in [RFC5201].
3.3.8.3. Specific Security Implications
TBD.
3.3.8.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain the Host Identity Protocol would
break HIP deployments.
3.3.8.5. Advice
Intermediate systems should permit packets that contain a Host
Identity Protocol extension header.
Gont, et al. Expires February 27, 2015 [Page 11]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.9. Shim6 Protocol (Protocol Number=140)
3.3.9.1. Uses
This extension header is employed by the Shim6 [RFC5533] Protocol.
3.3.9.2. Specification
This Extension Header is specified in [RFC5533].
3.3.9.3. Specific Security Implications
TBD.
3.3.9.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain this extension header will break
Shim6.
3.3.9.5. Advice
Intermediate systems should permit packets containing this extension
header.
3.3.10. Use for experimentation and testing (Protocol Numbers=253 and
254)
3.3.10.1. Uses
These IPv6 extension headers are employed for performing
RFC3692-Style experiments (see [RFC3692] for details).
3.3.10.2. Specification
These Extension Headers are specified in [RFC3692] and [RFC4727].
3.3.10.3. Specific Security Implications
The security implications of these extension headers will depend on
their specific use.
3.3.10.4. Operational and Interoperability Impact if Blocked
For obvious reasons, discarding packets that contain these extension
headers limits the ability to perform legitimate experiments across
IPv6 routers.
Gont, et al. Expires February 27, 2015 [Page 12]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.3.10.5. Advice
Intermediate systems should discard packets containing these
extension headers. Only in specific scenarios in which RFC3692-Style
experiments are to be performed should these extension headers be
permitted.
3.4. Advice on the Handling of Packets with Unknown IPv6 Extension
Headers
We refer to IPv6 extension headers that have not been assigned an
Internet Protocol Number by IANA (and marked as such) in
[IANA-PROTOCOLS] as "unknown IPv6 extension headers".
3.4.1. Uses
New IPv6 extension headers may be specified as part of future
extensions to the IPv6 protocol.
Since IPv6 Extension Headers and Upper-layer protocols employ the
same namespace, it is impossible to tell whether an unknown "Internet
Protocol Number" is being employed for an IPv6 Extension Header or an
Upper-Layer protocol.
3.4.2. Specification
The processing of unknown IPv6 extension headers is specified in
[RFC2460] and [RFC7045].
3.4.3. Specific Security Implications
For obvious reasons, it is impossible to determine specific security
implications of unknown IPv6 extension headers.
3.4.4. Operational and Interoperability Impact if Blocked
As noted in [RFC7045], discarding unknown IPv6 extension headers may
slow down the deployment of new IPv6 extension headers and transport
protocols. The corresponding IANA registry ([IANA-PROTOCOLS] should
be monitored such that filtering rules are updated as new IPv6
extension headers are standardized.
We note that since IPv6 extension headers and upper-layer protocols
share the same numbering space, discarding unknown IPv6 extension
headers may result in packets encapsulating unknown upper-layer
protocols being discarded.
Gont, et al. Expires February 27, 2015 [Page 13]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
3.4.5. Advice
Intermediate systems should discard packets containing unknown IPv6
extension headers.
4. IPv6 Options
4.1. General Discussion
The following subsections describe specific security implications of
different IPv6 options, and provide advice regarding filtering
packets that contain such options.
4.2. General Security Implications of IPv6 Options
The general security implications of IPv6 options are closely related
to those discussed in Section 3.2 for IPv6 Extension Headers.
Essentially, packets that contain IPv6 options might need to be
processed by an IPv6 router's general-purpose CPU,and hence could
present a DDoS risk to that router's general-purpose CPU (and thus to
the router itself). For some architectures, a possible mitigation
would be to rate-limit the packets that are to be processed by the
general-purpose CPU (see e.g. [Cisco-EH]).
4.3. Advice on the Handling of Packets with Specific IPv6 Options
The following subsections contain a description of each of the IPv6
options that have so far been specified, a discussion of possible
interoperability implications if packets containing such options are
discarded, and specific advice regarding whether packets containing
these options should be permitted.
4.3.1. Pad1 (Type=0x00)
4.3.1.1. Uses
This option is used when necessary to align subsequent options and to
pad out the containing header to a multiple of 8 octets in length.
4.3.1.2. Specification
This option is specified in [RFC2460].
4.3.1.3. Specific Security Implications
None.
Gont, et al. Expires February 27, 2015 [Page 14]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.1.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain this option would potentially break
any protocol that relies on IPv6 extension headers.
4.3.1.5. Advice
Intermediate systems should not discard packets based on the presence
of this option.
4.3.2. PadN (Type=0x01)
4.3.2.1. Uses
This option is used when necessary to align subsequent options and to
pad out the containing header to a multiple of 8 octets in length.
4.3.2.2. Specification
This option is specified in [RFC2460].
4.3.2.3. Specific Security Implications
Because of the possible size of this option, it could be leveraged as
a large-bandwidth covert channel.
4.3.2.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain this option would potentially break
any protocol that relies on IPv6 extension headers.
4.3.2.5. Advice
Intermediate systems should not discard IPv6 packets based on the
presence of this option.
4.3.3. Jumbo Payload (Type=0XC2)
4.3.3.1. Uses
The Jumbo payload option provides the means of specifying payloads
larger than 65535 bytes.
4.3.3.2. Specification
This option is specified in [RFC2675].
Gont, et al. Expires February 27, 2015 [Page 15]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.3.3. Specific Security Implications
TBD.
4.3.3.4. Operational and Interoperability Impact if Blocked
Discarding packets based on the presence of this option will cause
IPv6 jumbograms to be discarded.
4.3.3.5. Advice
Intermediate systems should discard packets that contain this option.
An operator should permit this option only in specific scenarios in
which support for IPv6 jumbograms is desired.
4.3.4. RPL Option (Type=0x63)
4.3.4.1. Uses
The RPL Option provides a mechanism to include routing information
with each datagram that an RPL router forwards.
4.3.4.2. Specification
This option is specified in [RFC6553].
4.3.4.3. Specific Security Implications
TBD.
4.3.4.4. Operational and Interoperability Impact if Blocked
This option is meant to be employed within an RPL instance. As a
result, discarding packets based on the presence of this option (e.g.
at an ISP) will not result in interoperability implications.
4.3.4.5. Advice
Non-RPL routers should discard packets that contain an RPL option.
4.3.5. Tunnel Encapsulation Limit (Type=0x04)
4.3.5.1. Uses
The Tunnel Encapsulation Limit option can be employed to specify how
many further levels of nesting the packet is permitted to undergo.
Gont, et al. Expires February 27, 2015 [Page 16]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.5.2. Specification
This option is specified in [RFC2473].
4.3.5.3. Specific Security Implications
TBD.
4.3.5.4. Operational and Interoperability Impact if Blocked
Discarding packets based on the presence of this option could result
in tunnel traffic being discarded.
4.3.5.5. Advice
Intermediate systems should not discard packets based on the presence
of this option.
4.3.6. Router Alert (Type=0x05)
4.3.6.1. Uses
The Router Alert option [RFC2711] is typically employed for the RSVP
protocol [RFC2205] and the MLD protocol [RFC2710].
4.3.6.2. Specification
This option is specified in [RFC2711].
4.3.6.3. Specific Security Implications
Since this option causes the contents of the packet to be inspected
by the handling device, this option could be leveraged for performing
DoS attacks.
4.3.6.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain this option would break RSVP and
multicast deployments.
4.3.6.5. Advice
Intermediate systems should discard packets that contain this option.
Only in specific environments where support for RSVP or similar
protocols is desired should this option be permitted.
Gont, et al. Expires February 27, 2015 [Page 17]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.7. Quick-Start (Type=0x26)
4.3.7.1. Uses
This IP Option is used in the specification of Quick-Start for TCP
and IP, which is an experimental mechanism that allows transport
protocols, in cooperation with routers, to determine an allowed
sending rate at the start and, at times, in the middle of a data
transfer (e.g., after an idle period) [RFC4782].
4.3.7.2. Specification
This option is specified in [RFC4782], on the "Experimental" track.
4.3.7.3. Specific Security Implications
Section 9.6 of [RFC4782] notes that Quick-Start is vulnerable to two
kinds of attacks:
o attacks to increase the routers' processing and state load, and,
o attacks with bogus Quick-Start Requests to temporarily tie up
available Quick-Start bandwidth, preventing routers from approving
Quick-Start Requests from other connections.
We note that if routers in a given environment do not implement and
enable the Quick-Start mechanism, only the general security
implications of IP options (discussed in Section 4.2) would apply.
4.3.7.4. Operational and Interoperability Impact if Blocked
The Quick-Start functionality would be disabled, and additional
delays in TCP's connection establishment (for example) could be
introduced. (Please see Section 4.7.2 of [RFC4782].) We note,
however, that Quick-Start has been proposed as a mechanism that could
be of use in controlled environments, and not as a mechanism that
would be intended or appropriate for ubiquitous deployment in the
global Internet [RFC4782].
4.3.7.5. Advice
Intermediate systems should not discard IPv6 packets based on the
presence of this option.
Gont, et al. Expires February 27, 2015 [Page 18]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.8. CALIPSO (Type=0x07)
4.3.8.1. Uses
This option is used for encoding explicit packet Sensitivity Labels
on IPv6 packets. It is intended for use only within Multi-Level
Secure (MLS) networking environments that are both trusted and
trustworthy.
4.3.8.2. Specification
This option is specified in [RFC5570].
4.3.8.3. Specific Security Implications
Presence of this option in a packet does not by itself create any
specific new threat. Packets with this option ought not normally be
seen on the global public Internet.
4.3.8.4. Operational and Interoperability Impact if Blocked
If packets with this option are discarded or if the option is
stripped from the packet during transmission from source to
destination, then the packet itself is likely to be discarded by the
receiver because it is not properly labeled. In some cases, the
receiver might receive the packet but associate an incorrect
sensitivity label with the received data from the packet whose
CALIPSO was stripped by an intermediate router or firewall.
Associating an incorrect sensitivity label can cause the received
information either to be handled as more sensitive than it really is
("upgrading") or as less sensitive than it really is ("downgrading"),
either of which is problematic.
4.3.8.5. Advice
Intermediate systems that do not operate in Multi-Level Secure (MLS)
networking environments should discard packets that contain this
option.
4.3.9. SMF_DPD (Type=0x08)
4.3.9.1. Uses
This option is employed in the (experimental) Simplified Multicast
Forwarding (SMF) for unique packet identification for IPv6 I-DPD, and
as a mechanism to guarantee non-collision of hash values for
different packets when H-DPD is used.
Gont, et al. Expires February 27, 2015 [Page 19]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.9.2. Specification
This option is specified in [RFC6621].
4.3.9.3. Specific Security Implications
TBD.
4.3.9.4. Operational and Interoperability Impact if Blocked
TBD.
4.3.9.5. Advice
TBD.
4.3.10. Home Address (Type=0xC9)
4.3.10.1. Uses
The Home Address option is used by a Mobile IPv6 node while away from
home, to inform the recipient of the mobile node's home address.
4.3.10.2. Specification
This option is specified in [RFC6275].
4.3.10.3. Specific Security Implications
TBD.
4.3.10.4. Operational and Interoperability Impact if Blocked
Discarding IPv6 packets based on the presence of this option will
break Mobile IPv6.
4.3.10.5. Advice
Intermediate systems should not discard IPv6 packets based on the
presence of this option.
4.3.11. Endpoint Identification (Type=0x8A)
4.3.11.1. Uses
The Endpoint Identification option was meant to be used with the
Nimrod routing architecture [NIMROD-DOC], but has never seen
widespread deployment.
Gont, et al. Expires February 27, 2015 [Page 20]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.11.2. Specification
This option is specified in [NIMROD-DOC].
4.3.11.3. Specific Security Implications
TBD.
4.3.11.4. Operational and Interoperability Impact if Blocked
None.
4.3.11.5. Advice
Intermediate systems should discard packets that contain this option.
4.3.12. ILNP Nonce (Type=0x8B)
4.3.12.1. Uses
This option is employed by Identifier-Locator Network Protocol for
IPv6 (ILNPv6) for providing protection against off-path attacks for
packets when ILNPv6 is in use, and as a signal during initial
network-layer session creation that ILNPv6 is proposed for use with
this network-layer session, rather than classic IPv6.
4.3.12.2. Specification
This option is specified in [RFC6744].
4.3.12.3. Specific Security Implications
TBD.
4.3.12.4. Operational and Interoperability Impact if Blocked
Discarding packets that contain this option will break INLPv6
deployments.
4.3.12.5. Advice
Intermediate systems should not discard packets based on the presence
of this option.
Gont, et al. Expires February 27, 2015 [Page 21]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.13. Line-Identification Option (Type=0x8C)
4.3.13.1. Uses
This option is used by an Edge Router to identify the subscriber
premises in scenarios where several subscriber premises may be
logically connected to the same interface of an Edge Router.
4.3.13.2. Specification
This option is specified in [RFC6788].
4.3.13.3. Specific Security Implications
TBD.
4.3.13.4. Operational and Interoperability Impact if Blocked
Since this option is meant to be employed in Router Solicitation
messages, discarding packets based on the presence of this option at
intermediate systems will result in no interoperability implications.
4.3.13.5. Advice
Intermediate devices should discard packets that contain this option.
4.3.14. Deprecated (Type=0x4D)
4.3.14.1. Uses
No information has been found about this option type.
4.3.14.2. Specification
No information has been found about this option type.
4.3.14.3. Specific Security Implications
No information has been found about this option type, and hence it
has been impossible to perform the corresponding security assessment.
4.3.14.4. Operational and Interoperability Impact if Blocked
Unknown.
Gont, et al. Expires February 27, 2015 [Page 22]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.14.5. Advice
Intermediate systems should discard packets that contain this option.
4.3.15. MPL Option (Type=0x6D)
4.3.15.1. Uses
This option is used with the Multicast Protocol for Low power and
Lossy Networks (MPL), that provides IPv6 multicast forwarding in
constrained networks.
4.3.15.2. Specification
This option is specified in [I-D.ietf-roll-trickle-mcast], and is
meant to be included only in Hop-by-Hop Option headers.
4.3.15.3. Specific Security Implications
TBD.
4.3.15.4. Operational and Interoperability Impact if Blocked
TBD.
4.3.15.5. Advice
TBD.
4.3.16. IP_DFF (Type=0xEE)
4.3.16.1. Uses
This option is employed with the (Experimental) Depth-First
Forwarding (DFF) in Unreliable Networks.
4.3.16.2. Specification
This option is specified in [RFC6971].
4.3.16.3. Specific Security Implications
TBD.
Gont, et al. Expires February 27, 2015 [Page 23]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.3.16.4. Operational and Interoperability Impact if Blocked
TBD.
4.3.16.5. Advice
TBD.
4.3.17. RFC3692-style Experiment (Types = 0x1E, 0x3E, 0x5E, 0x7E, 0x9E,
0xBE, 0xDE, 0xFE)
4.3.17.1. Uses
These options can be employed for performing RFC3692-style
experiments. It is only appropriate to use these values in
explicitly configured experiments; they must not be shipped as
defaults in implementations.
4.3.17.2. Specification
Specified in RFC 4727 [RFC4727] in the context of RFC3692-style
experiments.
4.3.17.3. Specific Security Implications
The specific security implications will depend on the specific use of
these options.
4.3.17.4. Operational and Interoperability Impact if Blocked
For obvious reasons, discarding packets that contain these options
limits the ability to perform legitimate experiments across IPv6
routers.
4.3.17.5. Advice
Intermediate systems should discard packets that contain these
options. Only in specific environments where RFC3692-style
experiments are meant to be performed should these options be
permitted.
4.4. Advice on the handling of Packets with Unknown IPv6 Options
We refer to IPv6 options that have not been assigned an IPv6 option
type in the corresponding registry ([IANA-IPV6-PARAM]) as "unknown
IPv6 options".
Gont, et al. Expires February 27, 2015 [Page 24]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
4.4.1. Uses
New IPv6 options may be specified as part of future protocol work.
4.4.2. Specification
The processing of unknown IPv6 options is specified in [RFC2460].
4.4.3. Specific Security Implications
For obvious reasons, it is impossible to determine specific security
implications of unknown IPv6 options.
4.4.4. Operational and Interoperability Impact if Blocked
Discarding unknown IPv6 options may slow down the deployment of new
IPv6 options. As noted in [draft-gont-6man-ipv6-opt-transmit], the
corresponding IANA registry ([IANA-IPV6-PARAM] should be monitored
such that IPv6 option filtering rules are updated as new IPv6 options
are standardized.
4.4.5. Advice
Enterprise intermediate systems that process the contents of IPv6
extension headers should discard packets that contain unknown
options. Other intermediate systems that process the contents of
IPv6 extension headers should permit packets that contain unknown
options.
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
This document provides advice on the filtering of IPv6 packets that
contain IPv6 Extension Headers (and possibly IPv6 options).
Discarding such packets can help to mitigate the security issues that
arise from the use of different IPv6 Extension Headers and options.
7. Acknowledgements
The authors of this document would like to thank (in alphabetical
order) Mikael Abrahamsson, Brian Carpenter, Mike Heard, and Donald
Smith, for providing valuable comments on earlier versions of this
document.
Gont, et al. Expires February 27, 2015 [Page 25]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
This document borrows some text an analysis from [RFC7126], authored
by Fernando Gont, Randall Atkinson, and Carlos Pignataro.
8. References
8.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC2675] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms",
RFC 2675, August 1999.
[RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, October
1999.
[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, October 1999.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December
2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC4304] Kent, S., "Extended Sequence Number (ESN) Addendum to
IPsec Domain of Interpretation (DOI) for Internet Security
Association and Key Management Protocol (ISAKMP)", RFC
4304, December 2005.
Gont, et al. Expires February 27, 2015 [Page 26]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006.
[RFC4782] Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick-
Start for TCP and IP", RFC 4782, January 2007.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095, December
2007.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008.
[RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
Shim Protocol for IPv6", RFC 5533, June 2009.
[RFC5570] StJohns, M., Atkinson, R., and G. Thomas, "Common
Architecture Label IPv6 Security Option (CALIPSO)", RFC
5570, July 2009.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC6398] Le Faucheur, F., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, October 2011.
[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553, March
2012.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554, March
2012.
[RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621,
May 2012.
[RFC6740] Atkinson,, RJ., "Identifier-Locator Network Protocol
(ILNP) Architectural Description", RFC 6740, November
2012.
Gont, et al. Expires February 27, 2015 [Page 27]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
[RFC6744] Atkinson,, RJ., "IPv6 Nonce Destination Option for the
Identifier-Locator Network Protocol for IPv6 (ILNPv6)",
RFC 6744, November 2012.
[RFC6788] Krishnan, S., Kavanagh, A., Varga, B., Ooghe, S., and E.
Nordmark, "The Line-Identification Option", RFC 6788,
November 2012.
[RFC6971] Herberg, U., Cardenas, A., Iwao, T., Dow, M., and S.
Cespedes, "Depth-First Forwarding (DFF) in Unreliable
Networks", RFC 6971, June 2013.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045, December 2013.
[RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of
Oversized IPv6 Header Chains", RFC 7112, January 2014.
[draft-gont-6man-ipv6-opt-transmit]
Gont, F., Liu, W., and R. Bonica, "Transmission and
Processing of IPv6 Options", IETF Internet Draft, work in
progress, August 2014.
8.2. Informative References
[Biondi2007]
Biondi, P. and A. Ebalard, "IPv6 Routing Header Security",
CanSecWest 2007 Security Conference, 2007,
<http://www.secdev.org/conf/IPv6_RH_security-csw07.pdf>.
[Cisco-EH]
Cisco Systems, , "IPv6 Extension Headers Review and
Considerations", Whitepaper. October 2006,
<http://www.cisco.com/en/US/technologies/tk648/tk872/
technologies_white_paper0900aecd8054d37d.pdf>.
[FW-Benchmark]
Zack, E., "Firewall Security Assessment and Benchmarking
IPv6 Firewall Load Tests", IPv6 Hackers Meeting #1,
Berlin, Germany. June 30, 2013,
<http://www.ipv6hackers.org/meetings/ipv6-hackers-1/zack-
ipv6hackers1-firewall-security-assessment-and-
benchmarking.pdf>.
[I-D.gont-v6ops-ipv6-ehs-in-real-world]
Gont, F., Linkova, J., Chown, T., and W. Will, "IPv6
Extension Headers in the Real World", draft-gont-v6ops-
ipv6-ehs-in-real-world-00 (work in progress), August 2014.
Gont, et al. Expires February 27, 2015 [Page 28]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
[I-D.ietf-6man-predictable-fragment-id]
Gont, F., "Security Implications of Predictable Fragment
Identification Values", draft-ietf-6man-predictable-
fragment-id-01 (work in progress), April 2014.
[I-D.ietf-roll-trickle-mcast]
Hui, J. and R. Kelsey, "Multicast Protocol for Low power
and Lossy Networks (MPL)", draft-ietf-roll-trickle-
mcast-09 (work in progress), April 2014.
[IANA-IPV6-PARAM]
Internet Assigned Numbers Authority, "Internet Protocol
Version 6 (IPv6) Parameters", December 2013,
<http://www.iana.org/assignments/ipv6-parameters/
ipv6-parameters.xhtml>.
[IANA-PROTOCOLS]
Internet Assigned Numbers Authority, "Protocol Numbers",
2014, <http://www.iana.org/assignments/protocol-numbers/
protocol-numbers.xhtml>.
[NIMROD-DOC]
Nimrod Documentation Page, ,
"http://ana-3.lcs.mit.edu/~jnc/nimrod/", .
[RFC3871] Jones, G., "Operational Security Requirements for Large
Internet Service Provider (ISP) IP Network
Infrastructure", RFC 3871, September 2004.
[RFC7126] Gont, F., Atkinson, R., and C. Pignataro, "Recommendations
on Filtering of IPv4 Packets Containing IPv4 Options", BCP
186, RFC 7126, February 2014.
Authors' Addresses
Fernando Gont
UTN-FRH / SI6 Networks
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
Gont, et al. Expires February 27, 2015 [Page 29]
Internet-Draft Filtering of IPv6 packets with EHs August 2014
Will(Shucheng) Liu
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Email: liushucheng@huawei.com
Ronald P. Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
US
Phone: 571 250 5819
Email: rbonica@juniper.net
Gont, et al. Expires February 27, 2015 [Page 30]
