One document matched: draft-gont-numeric-ids-history-00.txt
Network Working Group F. Gont
Internet-Draft SI6 Networks / UTN-FRH
Intended status: Informational I. Arce
Expires: January 9, 2017 Fundacion Sadosky
July 8, 2016
Unfortunate History of Transient Numeric Identifiers
draft-gont-numeric-ids-history-00
Abstract
This document performs an analysis of the security and privacy
implications of different types of "numeric identifiers" used in IETF
protocols, and tries to categorize them based on their
interoperability requirements and the associated failure severity
when such requirements are not met. It describes a number of
algorithms that have been employed in real implementations to meet
such requirements and analyzes their security and privacy properties.
Additionally, it provides advice on possible algorithms that could be
employed to satisfy the interoperability requirements of each
identifier type, while minimizing the security and privacy
implications, thus providing guidance to protocol designers and
protocol implementers. Finally, it provides recommendations for
future protocol specifications regarding the specification of the
aforementioned numeric identifiers.
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 January 9, 2017.
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Copyright Notice
Copyright (c) 2016 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
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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.
This document may not be modified, and derivative works of it may not
be created, and it may not be published except as an Internet-Draft.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Threat Model . . . . . . . . . . . . . . . . . . . . . . . . 5
4. IPv4/IPv6 Identification . . . . . . . . . . . . . . . . . . 5
5. TCP Initial Sequence Numbers (ISNs) . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Network protocols employ a variety of numeric identifiers for
different protocol entities, ranging from DNS Transaction IDs (TxIDs)
to transport protocol numbers (e.g. TCP ports) or IPv6 Interface
Identifiers (IIDs). These identifiers usually have specific
properties that must be satisfied such that they do not result in
negative interoperability implications (e.g. uniqueness during a
specified period of time), and associated failure severities when
such properties are not met, ranging from soft to hard failures.
For more than 30 years, a large number of implementations of the TCP/
IP protocol suite have been subject to a variety of attacks, with
effects ranging from Denial of Service (DoS) or data injection, to
information leakage that could be exploited for pervasive monitoring
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[RFC7528]. The root of these issues has been, in many cases, the
poor selection of identifiers in such protocols, usually as a result
of an insufficient or misleading specification. While it is
generally trivial to identify an algorithm that can satisfy the
interoperability requirements for a given identifier, there exists
practical evidence that doing so without negatively affecting the
security and/or privacy properties of the aforementioned protocols is
prone to error.
For example, implementations have been subject to security and/or
privacy issues resulting from:
o Predictable TCP Initial Sequence Numbers (ISNs) (see e.g.
[Morris1985])
o Predictable ephemeral transport protocol numbers (see e.g.
[RFC6056] and [Silbersack2005])
o Predictable IPv4 or IPv6 Fragment Identifiers (see e.g.
[RFC5722], [RFC6274], and [RFC7739])
o Predictable IPv6 IIDs (see e.g. [RFC7721] and [RFC7707])
o Predictable DNS TxIDs
Recent history indicate that when new protocols are standardized or
new protocol implementations are produced, the security and privacy
properties of the associated identifiers tend to be overlooked and
inappropriate algorithms to generate identifier values are either
suggested in the specification or selected by implementers.
This document contains a non-exhaustive timeline of vulnerability
disclosures related to some sample transient numeric identifiers and
other work that has led to advances in this area, with the goal of
illustrating that:
o Vulnerabilities related to how the values for some identifiers are
generated and assigned have affected implementations for an
extremely long period of time.
o Such vulnerabilities, even when addressed for a given protocol
version, were later reintroduced in new versions or new
implementations of the same protocol.
o Standardization efforts that discuss and provide advice in this
area can have a positive effect on protocol specifications and
protocol implementations.
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Other related documents (such as
[I-D.gont-numeric-ids-sec-considerations]) provide guidance in this
area.
2. Terminology
Identifier:
A data object in a protocol specification that can be used to
definitely distinguish a protocol object (a datagram, network
interface, transport protocol endpoint, session, etc) from all
other objects of the same type, in a given context. Identifiers
are usually defined as a series of bits and represented using
integer values. We note that different identifiers may have
additional requirements or properties depending on their specific
use in a protocol. We use the term "identifier" as a generic term
to refer to any data object in a protocol specification that
satisfies the identification property stated above.
Failure Severity:
The consequences of a failure to comply with the interoperability
requirements of a given identifier. Severity considers the worst
potential consequence of a failure, determined by the system
damage and/or time lost to repair the failure. In this document
we define two types of failure severity: "soft" and "hard".
Hard Failure:
A hard failure is a non-recoverable condition in which a protocol
does not operate in the prescribed manner or it operates with
excessive degradation of service. For example, an established TCP
connection that is aborted due to an error condition constitutes,
from the point of view of the transport protocol, a hard failure,
since it enters a state from which normal operation cannot be
recovered.
Soft Failure:
A soft failure is a recoverable condition in which a protocol does
not operate in the prescribed manner but normal operation can be
resumed automatically in a short period of time. For example, a
simple packet-loss event that is subsequently recovered with a
retransmission can be considered a soft failure.
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 RFC 2119 [RFC2119].
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3. Threat Model
Throughout this document, we assume an attacker does not have
physical or logical device to the device(s) being attacked. We
assume the attacker can simply send any traffic to the target
devices, to e.g. sample identifiers employed by such devices.
4. IPv4/IPv6 Identification
December 1998:
[Sanfilippo1998a] finds that predictable IPv4 Identification
values can be leveraged to count the number of packets sent by a
target node. [Sanfilippo1998b] explains how to leverage the same
vulnerability to implement a port-scanning technique known as
dumb/idle scan. A tool that implements this attack is publicly
released.
November 1999:
[Sanfilippo1999] discusses how to leverage predictable IPv4
Identification to uncover the rules of a number of firewalls.
November 1999:
[Bellovin2002] explains how the IPv4 Identification field can be
exploited to count the number of systems behind a NAT.
December 2003:
[Zalewski2003] explains a technique to perform TCP data injection
attack based on predictable IPv4 identification values which
requires less effort than TCP injection attacks performed with
bare TCP packets.
November 2005:
[Silbersack2005] discusses shortcoming in a number of techniques
to mitigate predictable IPv4 Identification values.
October 2007:
[Klein2007] describes a weakness in the pseudo random number
generator (PRNG) in use for the generation of the IP
Identification by a number of operating systems.
June 2011:
[Gont2011] describes how to perform idle scan attacks in IPv6.
November 2011:
Linux mitigates predictable IPv6 Identification values
[RedHat2011] [SUSE2011] [Ubuntu2011].
December 2011:
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[I-D.ietf-6man-predictable-fragment-id-08] describes the security
implications of predictable IPv6 Identification values, and
possible mitigations.
May 2012:
[Gont2012] notes that some major IPv6 implementations still employ
predictable IPv6 Identification values.
June 2015:
[I-D.ietf-6man-predictable-fragment-id-08] notes that some popular
host and router implementations still employ predictable IPv6
Identification values.
5. TCP Initial Sequence Numbers (ISNs)
September 1981:
[RFC0793], suggests the use of a global 32-bit ISN generator,
whose lower bit is incremented roughly every 4 microseconds.
However, such an ISN generator makes it trivial to predict the ISN
that a TCP will use for new connections, thus allowing a variety
of attacks against TCP.
February 1985:
[Morris1985] was the first to describe how to exploit predictable
TCP ISNs for forging TCP connections that could then be leveraged
for trust relationship exploitation.
April 1989:
[Bellovin1989] discussed the security implications of predictable
ISNs (along with a range of other protocol-based vulnerabilities).
February 1995:
[Shimomura1995] reported a real-world exploitation of the attack
described in 1985 (ten years before) in [Morris1985].
May 1996:
[RFC1948] was the first IETF effort, authored by Steven Bellovin,
to address predictable TCP ISNs. The same concept specified in
this document for TCP ISNs was later proposed for TCP ephemeral
ports [RFC6056], TCP Timestamps, and eventually even IPv6
Interface Identifiers [RFC7217].
March 2001:
[Zalewski2001] provides a detailed analysis of statistical
weaknesses in some ISN generators, and includes a survey of the
algorithms in use by popular TCP implementations.
May 2001:
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Vulnerability advisories [CERT2001] [USCERT2001] are released
regarding statistical weaknesses in some ISN generators, affecting
popular TCP/IP implementations.
March 2002:
[Zalewski2002] updates and complements [Zalewski2001]. It
concludes that "while some vendors [...] reacted promptly and
tested their solutions properly, many still either ignored the
issue and never evaluated their implementations, or implemented a
flawed solution that apparently was not tested using a known
approach" [Zalewski2002].
February 2012:
[RFC6528], after 27 years of Morris' original work [Morris1985],
formally updates [RFC0793] to mitigate predictable TCP ISNs.
August 2014:
[I-D.eddy-rfc793bis-04], the upcoming revision of the core TCP
protocol specification, incorporates the algorithm specified in
[RFC6528] as the recommended algorithm for TCP ISN generation.
6. IANA Considerations
There are no IANA registries within this document. The RFC-Editor
can remove this section before publication of this document as an
RFC.
7. Security Considerations
The entire document is about the security and privacy implications of
identifiers.
8. Acknowledgements
The authors would like to thank (in alphabetical order) Steven
Bellovin, Joseph Lorenzo Hall, Gre Norcie, and Martin Thomson, for
providing valuable comments on [I-D.gont-predictable-numeric-ids], on
which this document is based.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC6528] Gont, F. and S. Bellovin, "Defending against Sequence
Number Attacks", RFC 6528, DOI 10.17487/RFC6528, February
2012, <http://www.rfc-editor.org/info/rfc6528>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
[RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments",
RFC 5722, DOI 10.17487/RFC5722, December 2009,
<http://www.rfc-editor.org/info/rfc5722>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<http://www.rfc-editor.org/info/rfc6151>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<http://www.rfc-editor.org/info/rfc7217>.
9.2. Informative References
[RFC6274] Gont, F., "Security Assessment of the Internet Protocol
Version 4", RFC 6274, DOI 10.17487/RFC6274, July 2011,
<http://www.rfc-editor.org/info/rfc6274>.
[RFC7528] Higgs, P. and J. Piesing, "A Uniform Resource Name (URN)
Namespace for the Hybrid Broadcast Broadband TV (HbbTV)
Association", RFC 7528, DOI 10.17487/RFC7528, April 2015,
<http://www.rfc-editor.org/info/rfc7528>.
[RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks",
RFC 1948, DOI 10.17487/RFC1948, May 1996,
<http://www.rfc-editor.org/info/rfc1948>.
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[CPNI-TCP]
Gont, F., "Security Assessment of the Transmission Control
Protocol (TCP)", United Kingdom's Centre for the
Protection of National Infrastructure (CPNI) Technical
Report, 2009, <http://www.gont.com.ar/papers/
tn-03-09-security-assessment-TCP.pdf>.
[Zalewski2001]
Zalewski, M., "Strange Attractors and TCP/IP Sequence
Number Analysis", 2001,
<http://lcamtuf.coredump.cx/oldtcp/tcpseq.html>.
[Zalewski2002]
Zalewski, M., "Strange Attractors and TCP/IP Sequence
Number Analysis - One Year Later", 2001,
<http://lcamtuf.coredump.cx/newtcp/>.
[Bellovin1989]
Bellovin, S., "Security Problems in the TCP/IP Protocol
Suite", Computer Communications Review, vol. 19, no. 2,
pp. 32-48, 1989, <https://www.cs.columbia.edu/~smb/papers/
ipext.pdf>.
[Joncheray1995]
Joncheray, L., "A Simple Active Attack Against TCP", Proc.
Fifth Usenix UNIX Security Symposium, 1995.
[Morris1985]
Morris, R., "A Weakness in the 4.2BSD UNIX TCP/IP
Software", CSTR 117, AT&T Bell Laboratories, Murray Hill,
NJ, 1985, <https://pdos.csail.mit.edu/~rtm/
papers/117.pdf>.
[USCERT2001]
US-CERT, , "US-CERT Vulnerability Note VU#498440: Multiple
TCP/IP implementations may use statistically predictable
initial sequence numbers", 2001,
<http://www.kb.cert.org/vuls/id/498440>.
[CERT2001]
CERT, , "CERT Advisory CA-2001-09: Statistical Weaknesses
in TCP/IP Initial Sequence Numbers", 2001,
<http://www.cert.org/advisories/CA-2001-09.html>.
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[Shimomura1995]
Shimomura, T., "Technical details of the attack described
by Markoff in NYT", Message posted in USENET's
comp.security.misc newsgroup Message-ID:
<3g5gkl$5j1@ariel.sdsc.edu>, 1995,
<http://www.gont.com.ar/docs/post-shimomura-usenet.txt>.
[I-D.eddy-rfc793bis-04]
Eddy, W., "Transmission Control Protocol Specification",
draft-eddy-rfc793bis-04 (work in progress), August 2014.
[RFC6056] Larsen, M. and F. Gont, "Recommendations for Transport-
Protocol Port Randomization", BCP 156, RFC 6056,
DOI 10.17487/RFC6056, January 2011,
<http://www.rfc-editor.org/info/rfc6056>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC7739] Gont, F., "Security Implications of Predictable Fragment
Identification Values", RFC 7739, DOI 10.17487/RFC7739,
February 2016, <http://www.rfc-editor.org/info/rfc7739>.
[RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly
Errors at High Data Rates", RFC 4963,
DOI 10.17487/RFC4963, July 2007,
<http://www.rfc-editor.org/info/rfc4963>.
[Bellovin2002]
Bellovin, S., "A Technique for Counting NATted Hosts",
IMW'02 Nov. 6-8, 2002, Marseille, France, 2002.
[Fyodor2004]
Fyodor, , "Idle scanning and related IP ID games", 2004,
<http://www.insecure.org/nmap/idlescan.html>.
[Sanfilippo1998a]
Sanfilippo, S., "about the ip header id", Post to Bugtraq
mailing-list, Mon Dec 14 1998,
<http://seclists.org/bugtraq/1998/Dec/48>.
[Sanfilippo1998b]
Sanfilippo, S., "Idle scan", Post to Bugtraq mailing-list,
1998, <http://www.kyuzz.org/antirez/papers/dumbscan.html>.
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[Sanfilippo1999]
Sanfilippo, S., "more ip id", Post to Bugtraq mailing-
list, 1999,
<http://www.kyuzz.org/antirez/papers/moreipid.html>.
[Silbersack2005]
Silbersack, M., "Improving TCP/IP security through
randomization without sacrificing interoperability",
EuroBSDCon 2005 Conference, 2005,
<http://citeseerx.ist.psu.edu/viewdoc/
download?doi=10.1.1.91.4542&rep=rep1&type=pdf>.
[Zalewski2003]
Zalewski, M., "A new TCP/IP blind data injection
technique?", 2003,
<http://lcamtuf.coredump.cx/ipfrag.txt>.
[Klein2007]
Klein, A., "OpenBSD DNS Cache Poisoning and Multiple O/S
Predictable IP ID Vulnerability", 2007,
<http://www.trusteer.com/files/OpenBSD_DNS_Cache_Poisoning
_and_Multiple_OS_Predictable_IP_ID_Vulnerability.pdf>.
[Gont2011]
Gont, F., "Hacking IPv6 Networks (training course)", Hack
In Paris 2011 Conference Paris, France, June 2011.
[RedHat2011]
RedHat, , "RedHat Security Advisory RHSA-2011:1465-1:
Important: kernel security and bug fix update", 2011,
<https://rhn.redhat.com/errata/RHSA-2011-1465.html>.
[Ubuntu2011]
Ubuntu, , "Ubuntu: USN-1253-1: Linux kernel
vulnerabilities", 2011,
<http://www.ubuntu.com/usn/usn-1253-1/>.
[SUSE2011]
SUSE, , "SUSE Security Announcement: Linux kernel security
update (SUSE-SA:2011:046)", 2011,
<http://lists.opensuse.org/
opensuse-security-announce/2011-12/msg00011.html>.
[Gont2012]
Gont, F., "Recent Advances in IPv6 Security", BSDCan 2012
Conference Ottawa, Canada. May 11-12, 2012, May 2012.
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[I-D.ietf-6man-predictable-fragment-id-08]
Gont, F., "Security Implications of Predictable Fragment
Identification Values", draft-ietf-6man-predictable-
fragment-id-08 (work in progress), June 2015.
[I-D.ietf-6man-default-iids]
Gont, F., Cooper, A., Thaler, D., and S. (Will),
"Recommendation on Stable IPv6 Interface Identifiers",
draft-ietf-6man-default-iids-11 (work in progress), April
2016.
[RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
Considerations for IPv6 Address Generation Mechanisms",
RFC 7721, DOI 10.17487/RFC7721, March 2016,
<http://www.rfc-editor.org/info/rfc7721>.
[RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<http://www.rfc-editor.org/info/rfc7707>.
[I-D.gont-predictable-numeric-ids]
Gont, F. and I. Arce, "Security and Privacy Implications
of Numeric Identifiers Employed in Network Protocols",
draft-gont-predictable-numeric-ids-00 (work in progress),
February 2016.
[I-D.gont-numeric-ids-sec-considerations]
Gont, F. and I. Arce, "Security Considerations for
Transient Numeric Identifiers Employed in Network
Protocols", draft-gont-numeric-ids-sec-considerations-00
(work in progress), June 2016.
Authors' Addresses
Fernando Gont
SI6 Networks / UTN-FRH
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
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Ivan Arce
Fundacion Dr. Manuel Sadosky
Av. Cordoba 744 Piso 5 Oficina I
Ciudad Autonoma de Buenos Aires, Buenos Aires C1054AAT
Argentina
Phone: +54 11 4328 5164
Email: stic@fundacionsadosky.org.ar
URI: http://www.fundacionsadosky.org.ar
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