Internet DRAFT - draft-ietf-opsec-ip-options-filtering
draft-ietf-opsec-ip-options-filtering
Operational Security Capabilities for F. Gont
IP Network Infrastructure (opsec) UTN-FRH / SI6 Networks
Internet-Draft R. Atkinson
Intended status: BCP Consultant
Expires: June 12, 2014 C. Pignataro
Cisco
December 9, 2013
Recommendations on filtering of IPv4 packets containing IPv4 options.
draft-ietf-opsec-ip-options-filtering-07
Abstract
This document provides advice on the filtering of IPv4 packets based
on the IPv4 options they contain. Additionally, it discusses the
operational and interoperability implications of dropping packets
based on the IP 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 June 12, 2014.
Copyright Notice
Copyright (c) 2013 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
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology and Conventions Used in This Document . . . . 3
1.2. Operational Focus . . . . . . . . . . . . . . . . . . . . 4
2. IP Options . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. General Security Implications of IP options . . . . . . . . . 5
3.1. Processing Requirements . . . . . . . . . . . . . . . . . 5
4. Advice on the Handling of Packets with Specific IP Options . . 7
4.1. End of Option List (Type = 0) . . . . . . . . . . . . . . 7
4.2. No Operation (Type = 1) . . . . . . . . . . . . . . . . . 7
4.3. Loose Source and Record Route (LSRR) (Type = 131) . . . . 8
4.4. Strict Source and Record Route (SSRR) (Type = 137) . . . . 10
4.5. Record Route (Type = 7) . . . . . . . . . . . . . . . . . 11
4.6. Stream Identifier (Type = 136) (obsolete) . . . . . . . . 12
4.7. Internet Timestamp (Type = 68) . . . . . . . . . . . . . . 13
4.8. Router Alert (Type = 148) . . . . . . . . . . . . . . . . 14
4.9. Probe MTU (Type = 11) (obsolete) . . . . . . . . . . . . . 15
4.10. Reply MTU (Type = 12) (obsolete) . . . . . . . . . . . . . 16
4.11. Traceroute (Type = 82) . . . . . . . . . . . . . . . . . . 16
4.12. DoD Basic Security Option (Type = 130) . . . . . . . . . . 17
4.13. DoD Extended Security Option (Type = 133) . . . . . . . . 20
4.14. Commercial IP Security Option (CIPSO) (Type = 134) . . . . 22
4.15. VISA (Type = 142) . . . . . . . . . . . . . . . . . . . . 23
4.16. Extended Internet Protocol (Type = 145) . . . . . . . . . 23
4.17. Address Extension (Type = 147) . . . . . . . . . . . . . . 24
4.18. Sender Directed Multi-Destination Delivery (Type = 149) . 25
4.19. Dynamic Packet State (Type = 151) . . . . . . . . . . . . 25
4.20. Upstream Multicast Pkt. (Type = 152) . . . . . . . . . . . 26
4.21. Quick-Start (Type = 25) . . . . . . . . . . . . . . . . . 27
4.22. RFC3692-style Experiment (Types = 30, 94, 158, and 222) . 28
4.23. Other IP Options . . . . . . . . . . . . . . . . . . . . . 28
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
6. Security Considerations . . . . . . . . . . . . . . . . . . . 30
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1. Normative References . . . . . . . . . . . . . . . . . . . 31
8.2. Informative References . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
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1. Introduction
This document discusses the filtering of IPv4 packets based on the
IPv4 options they contain. Since various protocols may use IPv4
options to some extent, dropping packets based on the options they
contain may have implications on the proper functioning of the
protocol. Therefore, this document attempts to discuss the
operational and interoperability implications of such dropping.
Additionally, it outlines what a network operator might do in a
typical enterprise or Service Provider environments. This document
also draws and is partly derifed from [RFC6274], which also received
review from the operational community.
We note that data seems to indicate that there is a current
widespread practice of blocking IPv4 optioned packets. There are
various plausible approaches to minimize the potential negative
effects of IPv4 optioned packets while allowing some options
semantics. One approach is to allow for specific options that are
expected or needed, and a default deny. A different approach is to
deny unneeded options and a default allow. Yet a third possible
approach is to allow for end-to-end semantics by ignoring options and
treating packets as un-optioned while in transit. Experiments and
currently-available data tends to support the first or third
approaches as more realistic. Some results of regarding the current
state of affairs with respect to dropping packets containing IP
options can be found in [MEDINA] [FONSECA]. Additionally,
[BREMIER-BARR] points out that the deployed Internet already has many
routers that do not process IP options.
We also note that while this document provides advice on dropping
packets on a "per IP option type", not all devices (routers, security
gateways, and firewalls) may provide this capability with such
granularity. Additionally, even in cases in which such functionality
is provided, the operator might want to specify a dropping policy
with a coarser granularity (rather than on a "per IP option type"
granularity), as indicated above.
Finally, in scenarios in which processing of IP options by
intermediate systems is not required, a widespread approach is to
simply ignore IP options, and process the corresponding packets as if
they do not contain any IP options.
1.1. Terminology and Conventions Used in This Document
The terms "fast path", "slow path", and associated relative terms
("faster path" and "slower path") are loosely defined as in Section 2
of [RFC6398].
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Because of the security-oriented nature of this document, we are
deliberately including some historical citations. This is
intentional, and has the goal of explicitly retaining and showing
history, as well as removing ambiguity and confusion.
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].
1.2. Operational Focus
All of the recommendations in this document have been made in an
effort to optimise for operational community consensus, as best the
editors have been able to determine that. This has included not only
accepting feedback from public lists, but also accepting off-list
feedback from people at various network operators (e.g. ISPs,
content providers, educational institutions, commercial firms).
2. IP Options
IP options allow for the extension of the Internet Protocol. As
specified in [RFC0791], there are two cases for the format of an
option:
o Case 1: A single byte of option-type.
o Case 2: An option-type byte, an option-length byte, and the actual
option-data bytes.
IP options of Case 1 have the following syntax:
+-+-+-+-+-+-+-+-+- - - - - - - - -
| option-type | option-data
+-+-+-+-+-+-+-+-+- - - - - - - - -
The length of IP options of Case 1 is implicitly specified by the
option-type byte.
IP options of Case 2 have the following syntax:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
| option-type | option-length | option-data
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
In this case, the option-length byte counts the option-type byte and
the option-length byte, as well as the actual option-data bytes.
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All current and future options except "End of Option List" (Type = 0)
and "No Operation" (Type = 1), are of Class 2.
The option-type has three fields:
o 1 bit: copied flag.
o 2 bits: option class.
o 5 bits: option number.
The copied flag indicates whether this option should be copied to all
fragments in the event the packet carrying it needs to be fragmented:
o 0 = not copied.
o 1 = copied.
The values for the option class are:
o 0 = control.
o 1 = reserved for future use.
o 2 = debugging and measurement.
o 3 = reserved for future use.
This format allows for the creation of new options for the extension
of the Internet Protocol (IP).
Finally, the option number identifies the syntax of the rest of the
option.
The "IP OPTION NUMBERS" registry [IANA-IP] contains the list of the
currently assigned IP option numbers.
3. General Security Implications of IP options
3.1. Processing Requirements
Historically, most IP routers used a general-purpose CPU to process
IP packets and forward them towards their destination. This same CPU
usually also processed network management traffic (e.g., SNMP),
configuration commands (e.g., command line interface), and various
routing protocols (e.g., RIP, OSPF, BGP, IS-IS) or other control
protocols (e.g., RSVP, ICMP). In such architectures it has been
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common for the general-purpose CPU also to perform any packet
filtering that has been enabled on the router (or router interface).
An IP router built using this architecture often has a significant
(Distributed) Denial-of-Service (DDOS) attack risk if the router
control plane (e.g., CPU) is overwhelmed by a large number of IPv4
packets that contain IPv4 options.
From about 1995 onwards, a growing number of IP routers have
incorporated specialized IP packet processing silicon (i.e., FPGA,
ASIC), thereby separating the IP packet forwarding function from the
other functions of the router. Such router architectures tend to be
more resilient to DDOS attacks that might be seen in the global
public Internet. Depending upon various implementation and
configuration details, routers with a silicon packet forwarding
engine can handle high volumes of IP packets containing IP Options
without any adverse impact on packet forwarding rates or on the
router's control plane (e.g., general-purpose CPU). Some
implementations have a configuration knob simply to forward all IP
packets containing IP Options at wire-speed in silicon as if the IP
packet did not contain an IP option ("ignore options & forward").
Other implementations support wire-speed silicon-based packet
filtering, thereby enabling packets containing certain IP options to
be selectively dropped ("drop"), packets containing certain other IP
options to have those IP options ignored ("ignore options &
forward"), and other packets containing different IP options to have
those options processed, either on a general-purpose CPU or using
custom logic (e.g., FPGA, ASIC), while the packet is being forwarded
("process option & forward").
Broadly speaking, any IP packet that requires processing by an IP
router's general-purpose CPU can be a DDOS risk to that router's
general-purpose CPU (and thence to the router itself). However, at
present, the particular architectural and engineering details of the
particular IP router being considered are important to understand
when evaluating the operational security risks associated with a
particular IP packet type or IP option type.
Operators are urged to consider IP option filtering and IP option
handling capabilities of potential IP routers as they make deployment
decisions in future.
Additional considerations for protecting the control plane from
packets containing IP Options can be found in [RFC6192].
Finally, in addition to advice to operators, this document also
provides advice to router, security gateway, and firewall
implementers in terms of providing the capability to filter packets
with different granularities: both on a "per IP option type"
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granularity (to maximize flexibility) as well as more coarse filters
(to minimize configuration complexity).
4. Advice on the Handling of Packets with Specific IP Options
The following subsections contain a description of each of the IP
options that have so far been specified, a discussion of possible
interoperability implications if packets containing such options are
dropped, and specific advice on whether to drop packets containing
these options in a typical enterprise or Service Provider
environment.
4.1. End of Option List (Type = 0)
4.1.1. Uses
This option is used to indicate the "end of options" in those cases
in which the end of options would not coincide with the end of the
Internet Protocol Header.
4.1.2. Option Specification
Specified in RFC 791 [RFC0791].
4.1.3. Threats
No specific security issues are known for this IPv4 option.
4.1.4. Operational and Interoperability Impact if Blocked
Packets containing any IP options are likely to include an End of
Option List. Therefore, if packets containing this option are
dropped, it is very likely that legitimate traffic is blocked.
4.1.5. Advice
Routers, security gateways, and firewalls SHOULD NOT drop packets
because they contain this option.
4.2. No Operation (Type = 1)
4.2.1. Uses
The no-operation option is basically meant to allow the sending
system to align subsequent options in, for example, 32-bit
boundaries.
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4.2.2. Option Specification
Specified in RFC 791 [RFC0791].
4.2.3. Threats
No specific security issues are known for this IPv4 option.
4.2.4. Operational and Interoperability Impact if Blocked
Packets containing any IP options are likely to include a No
Operation option. Therefore, if packets containing this option are
dropped, it is very likely that legitimate traffic is blocked.
4.2.5. Advice
Routers, security gateways, and firewalls SHOULD NOT drop packets
because they contain this option.
4.3. Loose Source and Record Route (LSRR) (Type = 131)
RFC 791 states that this option should appear at most once in a given
packet. Thus, if a packet contains more than one LSRR option, it
should be dropped, and this event should be logged (e.g., a counter
could be incremented to reflect the packet drop). Additionally,
packets containing a combination of LSRR and SSRR options should be
dropped, and this event should be logged (e.g., a counter could be
incremented to reflect the packet drop).
4.3.1. Uses
This option lets the originating system specify a number of
intermediate systems a packet must pass through to get to the
destination host. Additionally, the route followed by the packet is
recorded in the option. The receiving host (end-system) must use the
reverse of the path contained in the received LSRR option.
The LSSR option can be of help in debugging some network problems.
Some ISP (Internet Service Provider) peering agreements require
support for this option in the routers within the peer of the ISP.
4.3.2. Option Specification
Specified in RFC 791 [RFC0791].
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4.3.3. Threats
The LSRR option has well-known security implications [RFC6274].
Among other things, the option can be used to:
o Bypass firewall rules.
o Reach otherwise unreachable internet systems.
o Establish TCP connections in a stealthy way.
o Learn about the topology of a network.
o Perform bandwidth-exhaustion attacks.
Of these attack vectors, the one that has probably received least
attention is the use of the LSRR option to perform bandwidth
exhaustion attacks. The LSRR option can be used as an amplification
method for performing bandwidth-exhaustion attacks, as an attacker
could make a packet bounce multiple times between a number of systems
by carefully crafting an LSRR option.
This is the IPv4-version of the IPv6 amplification attack that was
widely publicized in 2007 [Biondi2007]. The only difference is
that the maximum length of the IPv4 header (and hence the LSRR
option) limits the amplification factor when compared to the IPv6
counter-part.
Additionally, some implementations have been found to fail to include
proper sanity checks on the LSRR option, thus leading to security
issues. These specific issues are believed to be solved in all
modern implementations.
[Microsoft1999] is a security advisory about a vulnerability
arising from improper validation of the Pointer field of the LSRR
option.
Finally, we note that some systems were known for providing a system-
wide toggle to enable support for this option for those scenarios in
which this option is required. However, improper implementation of
such system-wide toggle caused those systems to support the LSRR
option even when explicitly configured not to do so.
[OpenBSD1998] is a security advisory about an improper
implementation of such a system-wide toggle in 4.4BSD kernels.
This issue was resolved in later versions of the corresponding
operating system.
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4.3.4. Operational and Interoperability Impact if Blocked
Network troubleshooting techniques that may employ the LSRR option
(such as ping or traceroute with the appropriate arguments) would
break when using the LSRR option (ping and traceroute without IPv4
options are not impacted). Nevertheless, it should be noted that it
is virtually impossible to use the LSRR option for troubleshooting,
due to widespread dropping of packets that contain such option.
4.3.5. Advice
Routers, security gateways, and firewalls SHOULD implement an option-
specific configuration knob whether packets with this option are
dropped, packets with this IP option are forwarded as if they did not
contain this IP option, or packets with this option are processed and
forwarded as per [RFC0791]. The default setting for this knob SHOULD
be "drop", and the default setting MUST be documented.
Please note that treating packets with LSRR as if they did not
contain this option can result in such packets being sent to a
different device that the initially intended destination. With
appropriate ingress filtering this should not open an attack vector
into the infrastructure. Nonetheless, it could result in traffic
that would never reach the initially intended destination. Dropping
these packets prevents unnecessary network traffic, and does not make
end-to-end communication any worse.
4.4. Strict Source and Record Route (SSRR) (Type = 137)
4.4.1. Uses
This option allows the originating system to specify a number of
intermediate systems a packet must pass through to get to the
destination host. Additionally, the route followed by the packet is
recorded in the option, and the destination host (end-system) must
use the reverse of the path contained in the received SSRR option.
This option is similar to the Loose Source and Record Route (LSRR)
option, with the only difference that in the case of SSRR, the route
specified in the option is the exact route the packet must take
(i.e., no other intervening routers are allowed to be in the route).
The SSSR option can be of help in debugging some network problems.
Some ISP (Internet Service Provider) peering agreements require
support for this option in the routers within the peer of the ISP.
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4.4.2. Option Specification
Specified in RFC 791 [RFC0791].
4.4.3. Threats
The SSRR option has the same security implications as the LSRR
option. Please refer to Section 4.3 for a discussion of such
security implications.
4.4.4. Operational and Interoperability Impact if Blocked
Network troubleshooting techniques that may employ the SSRR option
(such as ping or traceroute with the appropriate arguments) would
break when using the SSRR option (ping and traceroute without IPv4
options are not impacted). Nevertheless, it should be noted that it
is virtually impossible to use the SSRR option for trouble-shooting,
due to widespread dropping of packets that contain such option.
4.4.5. Advice
Routers, security gateways, and firewalls SHOULD implement an option-
specific configuration knob whether packets with this option are
dropped, packets with this IP option are forwarded as if they did not
contain this IP option, or packets with this option are processed and
forwarded as per [RFC0791]. The default setting for this knob SHOULD
be "drop", and the default setting MUST be documented.
Please note that treating packets with SSRR as if they did not
contain this option can result in such packets being sent to a
different device that the initially intended destination. With
appropriate ingress filtering this should not open an attack vector
into the infrastructure. Nonetheless, it could result in traffic
that would never reach the initially intended destination. Dropping
these packets prevents unnecessary network traffic, and does not make
end-to-end communication any worse.
4.5. Record Route (Type = 7)
4.5.1. Uses
This option provides a means to record the route that a given packet
follows.
4.5.2. Option Specification
Specified in RFC 791 [RFC0791].
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4.5.3. Threats
This option can be exploited to map the topology of a network.
However, the limited space in the IP header limits the usefulness of
this option for that purpose.
4.5.4. Operational and Interoperability Impact if Blocked
Network troubleshooting techniques that may employ the RR option
(such as ping with the RR option) would break when using the RR
option (ping without IPv4 options is not impacted). Nevertheless, it
should be noted that it is virtually impossible to use such
techniques due to widespread dropping of packets that contain RR
options.
4.5.5. Advice
Routers, security gateways, and firewalls SHOULD implement an option-
specific configuration knob whether packets with this option are
dropped, packets with this IP option are forwarded as if they did not
contain this IP option, or packets with this option are processed and
forwarded as per [RFC0791]. The default setting for this knob SHOULD
be "drop", and the default setting MUST be documented.
4.6. Stream Identifier (Type = 136) (obsolete)
The Stream Identifier option originally provided a means for the 16-
bit SATNET stream Identifier to be carried through networks that did
not support the stream concept.
However, as stated by Section 3.2.1.8 of RFC 1122 [RFC1122] and
Section 4.2.2.1 of RFC 1812 [RFC1812], this option is obsolete.
Therefore, it must be ignored by the processing systems. See also
[IANA-IP] and [RFC6814].
RFC 791 states that this option appears at most once in a given
datagram. Therefore, if a packet contains more than one instance of
this option, it should be dropped, and this event should be logged
(e.g., a counter could be incremented to reflect the packet drop).
4.6.1. Uses
This option is obsolete. There is no current use for this option.
4.6.2. Option Specification
Specified in RFC 791 [RFC0791], and deprecated in RFC 1122 [RFC1122]
and RFC 1812 [RFC1812]. This option has been formally obsoleted by
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[RFC6814].
4.6.3. Threats
No specific security issues are known for this IPv4 option.
4.6.4. Operational and Interoperability Impact if Blocked
None.
4.6.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets
containing a Stream Identifier option.
4.7. Internet Timestamp (Type = 68)
4.7.1. Uses
This option provides a means for recording the time at which each
system (or a specified set of systems) processed this datagram, and
may optionally record the addresses of the systems providing the
timestamps.
4.7.2. Option Specification
Specified by RFC 791 [RFC0791].
4.7.3. Threats
The timestamp option has a number of security implications [RFC6274].
Among them are:
o It allows an attacker to obtain the current time of the systems
that process the packet, which the attacker may find useful in a
number of scenarios.
o It may be used to map the network topology, in a similar way to
the IP Record Route option.
o It may be used to fingerprint the operating system in use by a
system processing the datagram.
o It may be used to fingerprint physical devices, by analyzing the
clock skew.
[Kohno2005] describes a technique for fingerprinting devices by
measuring the clock skew. It exploits, among other things, the
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timestamps that can be obtained by means of the ICMP timestamp
request messages [RFC0791]. However, the same fingerprinting method
could be implemented with the aid of the Internet Timestamp option.
4.7.4. Operational and Interoperability Impact if Blocked
Network troubleshooting techniques that may employ the Internet
Timestamp option (such as ping with the Timestamp option) would break
when using the Timestamp option (ping without IPv4 options is not
impacted). Nevertheless, it should be noted that it is virtually
impossible to use such techniques due to widespread dropping of
packets that contain Internet Timestamp options.
4.7.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets
containing an Internet Timestamp option.
4.8. Router Alert (Type = 148)
4.8.1. Uses
The Router Alert option has the semantic "routers should examine this
packet more closely, if they participate in the functionality denoted
by the Value of the option".
4.8.2. Option Specification
The Router Alert option is defined in RFC 2113 [RFC2113] and later
updates to it have been clarified by RFC 5350 [RFC5350]. It contains
a 16-bit Value governed by an IANA registry (see [RFC5350]).
4.8.3. Threats
The security implications of the Router Alert option have been
discussed in detail in [RFC6398]. Basically, the Router Alert option
might be exploited to perform a Denial of Service (DoS) attack by
exhausting CPU resources at the processing routers.
4.8.4. Operational and Interoperability Impact if Blocked
Applications that employ the Router Alert option (such as RSVP
[RFC2205]) would break.
4.8.5. Advice
This option SHOULD be allowed only in controlled environments, where
the option can be used safely. [RFC6398] identifies some such
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environments. In unsafe environments, packets containing this option
SHOULD be dropped.
A given router, security gateway, or firewall system has no way of
knowing a priori whether this option is valid in its operational
environment. Therefore, routers, security gateways, and firewalls
SHOULD, by default, ignore the Router Alert option. Additionally,
Routers, security gateways, and firewalls SHOULD have a configuration
setting that governs their reaction in the presence of packets
containing the Router Alert option. This configuration setting
SHOULD allow to honor and process the option, ignore the option, or
drop packets containing this option.
4.9. Probe MTU (Type = 11) (obsolete)
4.9.1. Uses
This option originally provided a mechanism to discover the Path-MTU.
It has been declared obsolete.
4.9.2. Option Specification
This option was originally defined in RFC 1063 [RFC1063], and was
obsoleted with RFC 1191 [RFC1191]. This option is now obsolete, as
RFC 1191 obsoletes RFC 1063 without using IP options.
4.9.3. Threats
This option is obsolete. This option could have been exploited to
cause a host to set its PMTU estimate to an inordinately low or an
inordinately high value, thereby causing performance problems.
4.9.4. Operational and Interoperability Impact if Blocked
None
This option is NOT employed with the modern "Path MTU Discovery"
(PMTUD) mechanism [RFC1191], which employs special ICMP messages
(Type 3, Code 4) in combination with the IP DF bit. PLPMTUD
[RFC4821] can perform PMTUD without the need of any special
packets.
4.9.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets that
contain a Probe MTU option.
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4.10. Reply MTU (Type = 12) (obsolete)
4.10.1. Uses
This option and originally provided a mechanism to discover the Path-
MTU. It is now obsolete.
4.10.2. Option Specification
This option was originally defined in RFC 1063 [RFC1063], and was
obsoleted with RFC 1191 [RFC1191]. This option is now obsolete, as
RFC 1191 obsoletes RFC 1063 without using IP options.
4.10.3. Threats
This option is obsolete. This option could have been exploited to
cause a host to set its PMTU estimate to an inordinately low or an
inordinately high value, thereby causing performance problems.
4.10.4. Operational and Interoperability Impact if Blocked
None
This option is NOT employed with the modern "Path MTU Discovery"
(PMTUD) mechanism [RFC1191], which employs special ICMP messages
(Type 3, Code 4) in combination with the IP DF bit. PLPMTUD
[RFC4821] can perform PMTUD without the need of any special
packets.
4.10.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets that
contain a Reply MTU option.
4.11. Traceroute (Type = 82)
4.11.1. Uses
This option originally provided a mechanism to trace the path to a
host.
4.11.2. Option Specification
This option was originally specified by RFC 1393 [RFC1393] as
"experimental", and it was never widely deployed on the public
Internet. This option has been formally obsoleted by [RFC6814].
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4.11.3. Threats
This option is obsolete. Because this option required each router in
the path both to provide special processing and to send an ICMP
message, it could have been exploited to perform a Denial of Service
(DoS) attack by exhausting CPU resources at the processing routers.
4.11.4. Operational and Interoperability Impact if Blocked
None
4.11.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets that
contain a Traceroute option.
4.12. DoD Basic Security Option (Type = 130)
4.12.1. Uses
This option is used by Multi-Level-Secure (MLS) end-systems and
intermediate systems in specific environments to [RFC1108]:
o Transmit from source to destination in a network standard
representation the common security labels required by computer
security models [Landwehr81],
o validate the datagram as appropriate for transmission from the
source and delivery to the destination, and,
o ensure that the route taken by the datagram is protected to the
level required by all protection authorities indicated on the
datagram.
The DoD Basic Security Option (BSO) was implemented in IRIX
[IRIX2008] and is currently implemented in a number of operating
systems (e.g., Security-Enhanced Linux [SELinux2008], Solaris
[Solaris2008], and Cisco IOS [Cisco-IPSO]). It is also currently
deployed in a number of high-security networks. These networks are
typically either in physically secure locations, protected by
military/governmental communications security equipment, or both.
Such networks are typically built using commercial off-the-shelf
(COTS) IP routers and Ethernet switches, but are not normally
interconnected with the global public Internet. Multi-Level Secure
(MLS) systems are much more widely deployed now than they were at the
time the then-IESG decided to remove IPSO (IP Security Options) from
the IETF standards-track. Since nearly all MLS systems also support
IPSO BSO and IPSO ESO, this option is believed to have more
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deployment now than when the IESG removed this option from the IETF
standards-track. [RFC5570] describes a similar option recently
defined for IPv6 and has much more detailed explanations of how
sensitivity label options are used in real-world deployments.
4.12.2. Option Specification
It is specified by RFC 1108 [RFC1108]], which obsoleted RFC 1038
[RFC1038] (which in turn obsoleted the Security Option defined in RFC
791 [RFC0791]).
RFC 791 [RFC0791] defined the "Security Option" (Type = 130),
which used the same option type as the DoD Basic Security option
discussed in this section. Later, RFC 1038 [RFC1038] revised the
IP security options, and in turn was obsoleted by RFC 1108
[RFC1108]. The "Security Option" specified in RFC 791 is
considered obsolete by Section 3.2.1.8 of RFC 1122 [RFC1122] and
Section 4.2.2.1 of RFC 1812 [RFC1812], and therefore the
discussion in this section is focused on the DoD Basic Security
option specified by RFC 1108 [RFC1108].
Section 4.2.2.1 of RFC 1812 states that routers "SHOULD implement
this option".
Some private IP networks consider IP router-based per-interface
selective filtering of packets based on (a) the presence of an
IPSO option (including BSO and ESO) and (b) based on the contents
of that IPSO option to be important for operational security
reasons. The recent IPv6 CALIPSO option specification discusses
this in additional detail, albeit in an IPv6 context [RFC5570].
Such private IP networks commonly are built using both commercial
and open-source products - for hosts, guards, firewalls, switches,
routers, etc. Some commercial IP routers support this option, as
do some IP routers which are built on top of Multi-Level Secure
(MLS) operating systems (e.g., on top of Trusted Solaris
[Solaris2008] or Security-Enhanced Linux [SELinux2008]).
For example, many Cisco routers that run Cisco IOS include support
for selectively filtering packets that contain the IP Security
Options (IPSO) with per-interface granularity. This capability
has been present in many Cisco routers since the early 1990s
[Cisco-IPSO-Cmds]. Some government sector products reportedly
also support the IP Security Options (IPSO), for example CANEWARE
[RFC4949].
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Support for the IPSO Basic Security Option also is included in the
"IPsec Configuration Policy Information Model" [RFC3585] and in
the "IPsec Security Policy Database Configuration MIB" [RFC4807].
Section 4.6.1 of the IP Security Domain of Interpretation
[RFC2407] includes support for labeled IPsec security associations
compatible with the IP Security Options.
4.12.3. Threats
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.
4.12.4. Operational and Interoperability Impact if Blocked
If packets with this option are blocked or if the option is stripped
from the packet during transmission from source to destination, then
the packet itself is likely to be dropped by the receiver because it
isn't 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 BSO 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.
4.12.5. Advice
A given IP router, security gateway, or firewall has no way to know a
priori what environment it has been deployed into. Even closed IP
deployments generally use exactly the same commercial routers,
security gateways, and firewalls that are used in the public
Internet.
Since operational problems result in environments where this option
is needed if either the option is dropped or IP packets containing
this option are dropped, but no harm results if the option is carried
in environments where it is not needed, the default configuration
SHOULD NOT (a) modify or remove this IP option or (b) drop an IP
packet because the IP packet contains this option.
A given IP router, security gateway, or firewall MAY be configured to
drop this option or to drop IP packets containing this option in an
environment known to not use this option.
For auditing reasons, Routers, security gateways, and firewalls
SHOULD be capable of logging the numbers of packets containing the
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BSO on a per-interface basis. Also, Routers, security gateways, and
firewalls SHOULD be capable of dropping packets based on the BSO
presence as well as the BSO values.
4.13. DoD Extended Security Option (Type = 133)
4.13.1. Uses
This option permits additional security labeling information, beyond
that present in the Basic Security Option (Section 4.12), to be
supplied in an IP datagram to meet the needs of registered
authorities.
4.13.2. Option Specification
The DoD Extended Security Option (ESO) is specified by RFC 1108
[RFC1108].
Some private IP networks consider IP router-based per-interface
selective filtering of packets based on (a) the presence of an
IPSO option (including BSO and ESO) and (b) based on the contents
of that IPSO option to be important for operational security
reasons. The recent IPv6 CALIPSO option specification discusses
this in additional detail, albeit in an IPv6 context [RFC5570].
Such private IP networks commonly are built using both commercial
and open-source products - for hosts, guards, firewalls, switches,
routers, etc. Some commercial IP routers support this option, as
do some IP routers which are built on top of Multi-Level Secure
(MLS) operating systems (e.g., on top of Trusted Solaris
[Solaris2008] or Security-Enhanced Linux [SELinux2008]).
For example, many Cisco routers that run Cisco IOS include support
for selectively filtering packets that contain the IP Security
Options (IPSO) with per-interface granularity. This capability
has been present in many Cisco routers since the early 1990s
[Cisco-IPSO-Cmds]. Some government sector products reportedly
also support the IP Security Options (IPSO), for example CANEWARE
[RFC4949].
Support for the IPSO Extended Security Option also is included in
the "IPsec Configuration Policy Information Model" [RFC3585] and
in the "IPsec Security Policy Database Configuration MIB"
[RFC4807]. Section 4.6.1 of the IP Security Domain of
Interpretation [RFC2407] includes support for labeled IPsec
security associations compatible with the IP Security Options.
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4.13.3. Threats
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.
4.13.4. Operational and Interoperability Impact if Blocked
If packets with this option are blocked or if the option is stripped
from the packet during transmission from source to destination, then
the packet itself is likely to be dropped by the receiver because it
isn't 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 ESO 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.
4.13.5. Advice
A given IP router, security gateway, or firewall has no way to know a
priori what environment it has been deployed into. Even closed IP
deployments generally use exactly the same commercial routers,
security gateways, and firewalls that are used in the public
Internet.
Since operational problems result in environments where this option
is needed if either the option is dropped or IP packets containing
this option are dropped, but no harm results if the option is carried
in environments where it is not needed, the default configuration
SHOULD NOT (a) modify or remove this IP option or (b) drop an IP
packet because the IP packet contains this option.
A given IP router, security gateway, or firewall MAY be configured to
drop this option or to drop IP packets containing this option in an
environment known to not use this option.
For auditing reasons, Routers, security gateways, and firewalls
SHOULD be capable of logging the numbers of packets containing the
ESO on a per-interface basis. Also, Routers, security gateways, and
firewalls SHOULD be capable of dropping packets based on the ESO
presence as well as the ESO values.
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4.14. Commercial IP Security Option (CIPSO) (Type = 134)
4.14.1. Uses
This option was proposed by the Trusted Systems Interoperability
Group (TSIG), with the intent of meeting trusted networking
requirements for the commercial trusted systems market place.
It was implemented in IRIX [IRIX2008] and is currently implemented in
a number of operating systems (e.g., Security-Enhanced Linux
[SELinux2008], and Solaris [Solaris2008]). It is also currently
deployed in a number of high-security networks.
4.14.2. Option Specification
This option is specified in [I-D.ietf-cipso-ipsecurity] and
[FIPS1994]. There are zero known IP router implementations of CIPSO.
Several MLS operating systems support CIPSO, generally the same MLS
operating systems that support IPSO.
The TSIG proposal was taken to the Commercial Internet Security
Option (CIPSO) Working Group of the IETF [CIPSOWG1994], and an
Internet-Draft was produced [I-D.ietf-cipso-ipsecurity]. The
Internet-Draft was never published as an RFC, but the proposal was
later standardized by the U.S. National Institute of Standards and
Technology (NIST) as "Federal Information Processing Standard
Publication 188" [FIPS1994].
4.14.3. Threats
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.
4.14.4. Operational and Interoperability Impact if Blocked
If packets with this option are blocked or if the option is stripped
from the packet during transmission from source to destination, then
the packet itself is likely to be dropped by the receiver because it
isn't 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 CIPSO 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.
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4.14.5. Advice
Because of the design of this option, with variable syntax and
variable length, it is not practical to support specialized filtering
using the CIPSO information. No routers or firewalls are known to
support this option. However, Routers, security gateways, and
firewalls SHOULD NOT by default modify or remove this option from IP
packets and SHOULD NOT by default drop packets because they contain
this option. For auditing reasons, routers, security gateways, and
firewalls SHOULD be capable of logging the numbers of packets
containing the CIPSO on a per-interface basis. Also, Routers,
security gateways, and firewalls SHOULD be capable of dropping
packets based on the CIPSO presence.
4.15. VISA (Type = 142)
4.15.1. Uses
This options was part of an experiment at USC and was never widely
deployed.
4.15.2. Option Specification
The original option specification is not publicly available. This
option has been formally obsoleted by [RFC6814].
4.15.3. Threats
Not possible to determine (other the general security implications of
IP options discussed in Section 3), since the corresponding
specification is not publicly available.
4.15.4. Operational and Interoperability Impact if Blocked
None.
4.15.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets that
contain this option.
4.16. Extended Internet Protocol (Type = 145)
4.16.1. Uses
The EIP option was introduced by one of the proposals submitted
during the IPng efforts to address the problem of IPv4 address
exhaustion.
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4.16.2. Option Specification
Specified in [RFC1385]. This option has been formally obsoleted by
[RFC6814].
4.16.3. Threats
This option is obsolete. This option was used (or was intended to be
used) to signal that a packet superficially similar to an IPv4 packet
actually containted a different protocol, opening up the possibility
that an IPv4 node that simply ignored this option would process a
received packet in a manner inconsistent with the intent of the
sender. There are no know threats arising from this option, other
than the general security implications of IP options discussed in
Section 3.
4.16.4. Operational and Interoperability Impact if Blocked
None.
4.16.5. Advice
Routers, security gateways, and firewalls SHOULD drop packets that
contain this option.
4.17. Address Extension (Type = 147)
4.17.1. Uses
The Address Extension option was introduced by one of the proposals
submitted during the IPng efforts to address the problem of IPv4
address exhaustion.
4.17.2. Option Specification
Specified in [RFC1475]. This option has been formally obsoleted by
[RFC6814].
4.17.3. Threats
There are no know threats arising from this option, other than the
general security implications of IP options discussed in Section 3.
4.17.4. Operational and Interoperability Impact if Blocked
None.
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4.17.5. Advice
Routers, security gateways, and firewalls SHOULD drop packets that
contain this option.
4.18. Sender Directed Multi-Destination Delivery (Type = 149)
4.18.1. Uses
This option originally provided unreliable UDP delivery to a set of
addresses included in the option.
4.18.2. Option Specification
This option is specified in RFC 1770 [RFC1770]. It has been formally
obsoleted by [RFC6814].
4.18.3. Threats
This option could have been exploited for bandwidth-amplification in
Denial of Service (DoS) attacks.
4.18.4. Operational and Interoperability Impact if Blocked
None.
4.18.5. Advice
Routers, security gateways, and firewalls SHOULD drop IP packets that
contain a Sender Directed Multi-Destination Delivery option.
4.19. Dynamic Packet State (Type = 151)
4.19.1. Uses
The Dynamic Packet State option was used to specify specified Dynamic
Packet State (DPS) in the context of the differentiated service
architecture.
4.19.2. Option Specification
The Dynamic Packet State option was specified in
[I-D.stoica-diffserv-dps]. The aforementioned document was meant to
be published as "Experimental", but never made it into an RFC. This
option has been formally obsoleted by [RFC6814].
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4.19.3. Threats
Possible threats include theft of service and Denial of Service.
However, we note that is option has never been widely implemented or
deployed.
4.19.4. Operational and Interoperability Impact if Blocked
None.
4.19.5. Advice
Routers, security gateways, and firewalls SHOULD drop packets that
contain this option.
4.20. Upstream Multicast Pkt. (Type = 152)
4.20.1. Uses
This option was meant to solve the problem of doing upstream
forwarding of multicast packets on a multi-access LAN.
4.20.2. Option Specification
This option was originally specified in [I-D.farinacci-bidir-pim].
It was never formally standardized in the RFC series, and was never
widely implemented and deployed. Its use was obsoleted by [RFC5015],
which employs a control plane mechanism to solve the problem of doing
upstream forwarding of multicast packets on a multi-access LAN. This
option has been formally obsoleted by [RFC6814].
4.20.3. Threats
This option is obsolete. A router that ignored this option instead
of processing it as specified in [I-D.farinacci-bidir-pim] could have
forwarded multicast packets to an unintended destination.
4.20.4. Operational and Interoperability Impact if Blocked
None.
4.20.5. Advice
Routers, security gateways, and firewalls SHOULD drop packets that
contain this option.
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4.21. Quick-Start (Type = 25)
4.21.1. 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].
4.21.2. Option Specification
Specified in RFC 4782 [RFC4782], on the "Experimental" track.
4.21.3. Threats
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.
4.21.4. Operational and Interoperability Impact if Blocked
The Quick-Start functionality would be disabled, and additional
delays in e.g., TCP's connection establishment could be introduced
(please see Section 4.7.2 of [RFC4782]. We note, however, that
Quick-Start has been proposed as 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].
4.21.5. Advice
A given router, security gateway, or firewall system has no way of
knowing a priori whether this option is valid in its operational
environment. Therefore, routers, security gateways, and firewalls
SHOULD, by default, ignore the Quick Start option. Additionally,
Routers, security gateways, and firewalls SHOULD have a configuration
setting that governs their reaction in the presence of packets
containing the Quick Start option. This configuration setting SHOULD
allow to honor and process the option, ignore the option, or drop
packets containing this option. The default configuration is to
ignore the Quick Start option.
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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 3) would apply.
4.22. RFC3692-style Experiment (Types = 30, 94, 158, and 222)
Section 2.5 of RFC 4727 [RFC4727] allocates an option number with all
defined values of the "copy" and "class" fields for RFC3692-style
experiments. This results in four distinct option type codes: 30,
94, 158, and 222.
4.22.1. Uses
It is only appropriate to use these values in explicitly configured
experiments; they MUST NOT be shipped as defaults in implementations.
4.22.2. Option Specification
Specified in RFC 4727 [RFC4727] in the context of RFC3692-style
experiments.
4.22.3. Threats
No specific security issues are known for this IPv4 option.
4.22.4. Operational and Interoperability Impact if Blocked
None.
4.22.5. Advice
Routers, security gateways, and firewalls SHOULD have configuration
knobs for IP packets that contain RFC3692-style Experiment options to
select between "ignore & forward" and "drop & log"). Otherwise, no
legitimate experiment using these options will be able to traverse
any IP router.
Special care needs to be taken in the case of "drop & log". Devices
SHOULD count the number of packets dropped, but the logging of drop
events SHOULD be limited to not overburden device resources.
The aforementioned configuration knob SHOULD default to "drop & log".
4.23. Other IP Options
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4.23.1. Specification
Unrecognized IP Options are to be ignored. Section 3.2.1.8 of RFC
1122 [RFC1122] and Section 4.2.2.6 of RFC 1812 [RFC1812] specify this
behavior as follows:
RFC 1122: "The IP and transport layer MUST each interpret those IP
options that they understand and silently ignore the
others."
RFC 1812: "A router MUST ignore IP options which it does not
recognize."
This document adds that unrecognized IP Options MAY also be logged.
Further, routers, security gateways, and firewalls MUST provide the
ability to log drop events of IP packets containing unrecognized or
obsolete options.
A number of additional options are listed in the "IP OPTIONS NUMBERS"
IANA registry [IANA-IP] as of the time this document was last edited.
Specifically:
Copy Class Number Value Name
---- ----- ------ ----- -------------------------------------------
0 0 10 10 ZSU - Experimental Measurement
1 2 13 205 FINN - Experimental Flow Control
0 0 15 15 ENCODE - ???
1 0 16 144 IMITD - IMI Traffic Descriptor
1 0 22 150 - Unassigned (Released 18 Oct. 2005)
The ENCODE option (type 15) has been formally obsoleted by [RFC6814].
4.23.2. Threats
The lack of open specifications for these options makes it impossible
to evaluate their security implications.
4.23.3. Operational and Interoperability Impact if Blocked
The lack of open specifications for these options makes it impossible
to evaluate the operational and interoperability impact if packets
containing these options are blocked.
4.23.4. Advice
Routers, security gateways, and firewalls SHOULD have configuration
knobs for IP packets containing these options (or other options not
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recognized) to select between "ignore & forward" and "drop & log").
Section 4.23.1 points out that [RFC1122] and [RFC1812] specify that
unrecognized IP options MUST be ignored. However, the previous
paragraph states that routers, security gateways, and firewalls
SHOULD have a configuration option for dropping and logging IP
packets containing unrecognized options. While is is acknowledged
that this advice contradicts the previous RFC requirements, the
advice in this document reflects current operational reality.
Special care needs to be taken in the case of "drop & log". Devices
SHOULD count the number of packets dropped, but the logging of drop
events SHOULD be limited to not overburden device resources.
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
This document provides advice on the filtering of IP packets that
contain IP options. Dropping such packets can help to mitigate the
security issues that arise from use of different IP options. Many of
the IPv4 options listed in this document are deprecated and cause no
operational impact if dropped. However, dropping packets containing
IPv4 options that are in use can cause real operational problems in
deployed networks. Therefore, the practice of dropping all IPv4
packets containing one or more IPv4 options without careful
consideration is not recommended.
7. Acknowledgements
The authors would like to thank (in alphabetical order) Ron Bonica,
C. M. Heard, Merike Kaeo, Panos Kampanakis, Suresh Krishnan, Arturo
Servin, SM, and Donald Smith for providing thorough reviews and
valuable comments. Merike Kaeo also contributed text used in this
document.
The authors also wish to thank various network operations folks who
supplied feedback on earlier versions of this document, but did not
wish to be named explicitly in this document.
Part of this document is initially based on the document "Security
Assessment of the Internet Protocol" [CPNI2008] that is the result of
a project carried out by Fernando Gont on behalf of UK CPNI (formerly
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NISCC). Fernando Gont would like to thank UK CPNI (formerly NISCC)
for their continued support.
8. References
8.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers",
RFC 1812, June 1995.
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
February 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007.
[RFC6398] Le Faucheur, F., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, October 2011.
[RFC6814] Pignataro, C. and F. Gont, "Formally Deprecating Some IPv4
Options", RFC 6814, November 2012.
8.2. Informative References
[BREMIER-BARR]
Bremier-Barr, A. and H. Levy, "Spoofing prevention
method", Proceedings of IEEE InfoCom 2005 Volume 1, pp.
536-547, IEEE, March 2005.
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[Biondi2007]
Biondi, P. and A. Ebalard, "IPv6 Routing Header Security",
CanSecWest 2007 Security Conference <http://
www.secdev.org/conf/IPv6_RH_security-csw07.pdf>, 2007.
[CIPSOWG1994]
CIPSOWG, "Commercial Internet Protocol Security Option
(CIPSO) Working Group", 1994, <http://www.ietf.org/
proceedings/94jul/charters/cipso-charter.html>.
[CPNI2008]
Gont, F., "Security Assessment of the Internet Protocol",
<http://www.cpni.gov.uk/Docs/InternetProtocol.pdf>, 2008.
[Cisco-IPSO]
Cisco Systems, Inc., "Cisco IOS Security Configuration
Guide, Release 12.2 - Configuring IP Security Options",
2006, <http://www.cisco.com/en/US/docs/ios/12_2/security/
configuration/guide/scfipso.html>.
[Cisco-IPSO-Cmds]
Cisco Systems, Inc., "Cisco IOS Security Command
Reference, Release 12.2 - IP Security Options Commands",
<http://www.cisco.com/en/US/docs/ios/12_2/security/
command/reference/srfipso.html>.
[FIPS1994]
FIPS, "Standard Security Label for Information Transfer",
Federal Information Processing Standards Publication. FIP
PUBS 188, <http://csrc.nist.gov/publications/fips/fips188/
fips188.pdf>, 1994.
[FONSECA] Fonseca, R., Porter, G., Katz, R., Shenker, S., and I.
Stoica, "IP Options are not an option", December 2005.
[I-D.farinacci-bidir-pim]
Estrin, D. and D. Farinacci, "Bi-Directional Shared Trees
in PIM-SM", draft-farinacci-bidir-pim (work in progress),
May 1999.
[I-D.ietf-cipso-ipsecurity]
IETF CIPSO Working Group, "COMMERCIAL IP SECURITY OPTION
(CIPSO 2.2)", draft-ietf-cipso-ipsecurity-01 (work in
progress), 1992.
[I-D.stoica-diffserv-dps]
Stoica, I., Zhang, H., Baker, F., and Y. Bernet, "Per Hop
Behaviors Based on Dynamic Packet State",
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Internet-Draft Filtering of IP-optioned packets December 2013
draft-stoica-diffserv-dps-02 (work in progress),
October 2002.
[IANA-IP] Internet Assigned Numbers Authority, "IP OPTION NUMBERS",
April 2011,
<http://www.iana.org/assignments/ip-parameters>.
[IRIX2008]
IRIX, "IRIX 6.5 trusted_networking(7) manual page", 2008,
<http://techpubs.sgi.com/library/tpl/cgi-bin/
getdoc.cgi?coll=0650&db=man&fname=/usr/share/catman/a_man/
cat7/trusted_networking.z>.
[Kohno2005]
Kohno, T., Broido, A., and kc. Claffy, "Remote Physical
Device Fingerprinting", IEEE Transactions on Dependable
and Secure Computing Vol. 2, No. 2, 2005.
[Landwehr81]
Landwehr, C., "Formal Models for Computer Security", ACM
Computing Surveys Vol 13, No 3, September 1981, Assoc for
Computing Machinery, New York, NY, USA, 1981.
[MEDINA] Medina, A., Allman, M., and S. Floyd, "Measuring
Interactions Between Transport Protocols and Middleboxes",
Proc. 4th ACM SIGCOMM/USENIX Conference on
Internet Measurement, October 2004.
[Microsoft1999]
Microsoft, "Microsoft Security Program: Microsoft Security
Bulletin (MS99-038). Patch Available for "Spoofed Route
Pointer" Vulnerability", 1999, <http://www.microsoft.com/
technet/security/bulletin/ms99-038.mspx>.
[OpenBSD1998]
OpenBSD, "OpenBSD Security Advisory: IP Source Routing
Problem", 1998,
<http://www.openbsd.org/advisories/sourceroute.txt>.
[RFC1038] St. Johns, M., "Draft revised IP security option",
RFC 1038, January 1988.
[RFC1063] Mogul, J., Kent, C., Partridge, C., and K. McCloghrie, "IP
MTU discovery options", RFC 1063, July 1988.
[RFC1108] Kent, S., "U.S", RFC 1108, November 1991.
[RFC1385] Wang, Z., "EIP: The Extended Internet Protocol", RFC 1385,
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November 1992.
[RFC1393] Malkin, G., "Traceroute Using an IP Option", RFC 1393,
January 1993.
[RFC1475] Ullmann, R., "TP/IX: The Next Internet", RFC 1475,
June 1993.
[RFC1770] Graff, C., "IPv4 Option for Sender Directed Multi-
Destination Delivery", RFC 1770, March 1995.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2407] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, November 1998.
[RFC3585] Jason, J., Rafalow, L., and E. Vyncke, "IPsec
Configuration Policy Information Model", RFC 3585,
August 2003.
[RFC4782] Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick-
Start for TCP and IP", RFC 4782, January 2007.
[RFC4807] Baer, M., Charlet, R., Hardaker, W., Story, R., and C.
Wang, "IPsec Security Policy Database Configuration MIB",
RFC 4807, March 2007.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
RFC 4949, August 2007.
[RFC5350] Manner, J. and A. McDonald, "IANA Considerations for the
IPv4 and IPv6 Router Alert Options", RFC 5350,
September 2008.
[RFC5570] StJohns, M., Atkinson, R., and G. Thomas, "Common
Architecture Label IPv6 Security Option (CALIPSO)",
RFC 5570, July 2009.
[RFC6192] Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
Router Control Plane", RFC 6192, March 2011.
[RFC6274] Gont, F., "Security Assessment of the Internet Protocol
Version 4", RFC 6274, July 2011.
[SELinux2008]
National Security Agency, "Security-Enhanced Linux - NSA/
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CSS", January 2009,
<http://www.nsa.gov/research/selinux/index.shtml>.
[Solaris2008]
"Solaris Trusted Extensions - Labeled Security for
Absolute Protection", 2008, <http://www.sun.com/software/
solaris/ds/trusted_extensions.jsp#3>.
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
RJ Atkinson
Consultant
McLean, VA 22103
USA
Email: rja.lists@gmail.com
Carlos Pignataro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: cpignata@cisco.com
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