Internet DRAFT - draft-ietf-storm-ipsec-ips-update
draft-ietf-storm-ipsec-ips-update
Storage Maintenance (storm) D. Black
Internet-Draft EMC
Updates: 3720, 3723, 3821, 3822, 4018, 4172, 4173, 4174, 5040, P. Koning
Intended status: Standards Track Dell
Expires: April 23, 2014 October 20, 2013
Securing Block Storage Protocols over IP: RFC 3723 Requirements Update
for IPsec v3
draft-ietf-storm-ipsec-ips-update-04
Abstract
RFC 3723 specifies IPsec requirements for block storage protocols
over IP (e.g., iSCSI) based on IPsec v2 (RFC 2401 and related RFCs);
those requirements have subsequently been applied to remote direct
data placement protocols, e.g., RDMAP. This document updates RFC
3723's IPsec requirements to IPsec v3 (RFC 4301 and related RFCs) and
makes some changes to required algorithms based on developments in
cryptography since RFC 3723 was published.
[RFC Editor: The "Updates:" list above has been truncated by xml2rfc.
The complete list is - Updates: 3720, 3723, 3821, 3822, 4018, 4172,
4173, 4174, 5040, 5041, 5042, 5043, 5044, 5045, 5046, 5047, 5048 (if
approved) ]
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 April 23, 2014.
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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
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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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Summary of Changes to RFC 3723 . . . . . . . . . . . . . 3
1.3. Other Updated RFCs . . . . . . . . . . . . . . . . . . . 4
2. ESP Requirements . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Data Origin Authentication and Data Integrity Transforms 6
2.2. Confidentiality Transform Requirements . . . . . . . . . 6
3. IKEv1 and IKEv2 Requirements . . . . . . . . . . . . . . . . 8
3.1. Authentication Requirements . . . . . . . . . . . . . . . 9
3.2. D-H Group and PRF Requirements . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Normative References . . . . . . . . . . . . . . . . . . 12
6.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
RFC 3723 [RFC3723] specifies IPsec requirements for block storage
protocols over IP (e.g., iSCSI [RFC3720]) based on IPsec v2 (RFC 2401
[RFC2401] and related RFCs); those requirements have subsequently
been applied to remote direct data placement protocols, e.g., RDMAP
[RFC5040]. This document updates RFC 3723's IPsec requirements to
IPsec v3 ([RFC4301] and related RFCs) to reflect developments since
RFC 3723 was published.
For brevity, this document uses the term "block storage protocols" to
refer to all protocols to which RFC 3723's requirements apply, see
Section 1.3 for details.
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In addition to the IPsec v2 requirements in RFC 3723, IPsec v3, as
specified in [RFC4301] and related RFCs (e.g., IKEv2 [RFC5996]),
SHOULD be implemented for block storage protocols. Retention of the
mandatory requirement for IPsec v2 provides interoperability with
existing implementations, and the strong recommendation for IPsec v3
encourages implementers to move forward to that newer version of
IPsec.
Cryptographic developments since the publication of RFC 3723
necessitate changes to the encryption transform requirements for
IPsec v2, as explained further in Section 2.2; these updated
requirements also apply to IPsec v3.
Block storage protocols can be expected to operate at high data rates
(multiple Gigabits/second). The cryptographic requirements in this
document are strongly influenced by that expectation; an important
example is that 3DES CBC is no longer recommended for block storage
protocols due to the frequent rekeying impacts of 3DES's 64-bit block
size at high data rates.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
1.2. Summary of Changes to RFC 3723
This document makes the following changes to RFC 3723:
o Adds requirements that IPsec v3 SHOULD be implemented (ESPv3 and
IKEv2) in addition to IPsec v2, (see Section 1).
o Requires extended sequence numbers for both ESPv2 and ESPv3, see
Section 2.
o Clarifies key size requirements for AES CBC MAC with XCBC
extensions (MUST implement 128 bit keys, see Section 2.1).
o Adds IPsec v3 requirements for AES GMAC and GCM (SHOULD implement
when IKEv2 is supported, see Section 2.1 and Section 2.2).
o Removes implementation requirements for 3DES CBC and AES CTR
(changes requirements for both to "MAY implement"). Adds a "MUST
implement" requirement for AES CBC (see Section 2.2).
o Adds specific IKEv2 implementation requirements (see Section 3).
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o Removes the requirement that IKEv1 use UDP port 500 (see
Section 3).
o Allows use of OCSP in addition to CRLs to check certificates, and
changes the Diffie-Hellman group size recommendation to a minimum
of 2048 bits (see Section 3).
1.3. Other Updated RFCs
RFC 3723's IPsec requirements have been applied to a number of
protocols. For that reason, in addition to updating RFC 3723's IPsec
requirements, this document also updates the IPsec requirements for
each protocol that uses RFC 3723, i.e., the following RFCs are
updated - in each case, the update is solely to the IPsec
requirements:
o [RFC3720] "Internet Small Computer Systems Interface (iSCSI)"
o [RFC3821] "Fibre Channel Over TCP/IP (FCIP)"
o [RFC3822] "Finding Fibre Channel over TCP/IP (FCIP) Entities Using
Service Location Protocol version 2 (SLPv2)"
o [RFC4018] "Finding Internet Small Computer Systems Interface
(iSCSI) Targets and Name Servers by Using Service Location
Protocol version 2 (SLPv2)"
o [RFC4172] "iFCP - A Protocol for Internet Fibre Channel Storage
Networking"
o [RFC4173] "Bootstrapping Clients using the Internet Small Computer
System Interface (iSCSI) Protocol"
o [RFC4174] "The IPv4 Dynamic Host Configuration Protocol (DHCP)
Option for the Internet Storage Name Service"
o [RFC5040] "A Remote Direct Memory Access Protocol Specification"
o [RFC5041] "Direct Data Placement over Reliable Transports"
o [RFC5042] "Direct Data Placement Protocol (DDP) / Remote Direct
Memory Access Protocol (RDMAP) Security"
o [RFC5043] "Stream Control Transmission Protocol (SCTP) Direct Data
Placement (DDP) Adaptation"
o [RFC5044] "Marker PDU Aligned Framing for TCP Specification"
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o [RFC5045] "Applicability of Remote Direct Memory Access Protocol
(RDMA) and Direct Data Placement (DDP)"
o [RFC5046] "Internet Small Computer System Interface (iSCSI)
Extensions for Remote Direct Memory Access (RDMA)"
o [RFC5047] "DA: Datamover Architecture for the Internet Small
Computer System Interface (iSCSI)"
o [RFC5048] "Internet Small Computer System Interface (iSCSI)
Corrections and Clarifications"
[RFC3721] and [RFC5387] are not updated by this document, as their
usage of RFC 3723 does not encompass its IPsec requirements.
In addition, this document's updated IPsec requirements apply to the
new specifications for iSCSI ([I-D.ietf-storm-iscsi-cons]) and iSER (
[I-D.ietf-storm-iser]).
This document uses the term "block storage protocols" to refer to the
protocols (listed above) to which RFC 3723's requirements (as updated
by the requirements in this document) apply.
2. ESP Requirements
RFC 3723 requires that implementations MUST support IPsec ESPv2
[RFC2406] in tunnel mode as part of IPsec v2 to provide security for
both control packets and data packets, and that when ESPv2 is
utilized, per-packet data origin authentication, integrity and replay
protection MUST be provided.
This document modifies RFC 3723 to require that implementations
SHOULD also support IPsec ESPv3 [RFC4303] in tunnel mode as part of
IPsec v3 to provide security for both control packets and data
packets; per-packet data origin authentication, integrity and replay
protection MUST be provided when ESPv3 is utilized.
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At the high speeds at which block storage protocols are expected to
operate, a single IPsec SA could rapidly exhaust the ESP 32-bit
sequence number space, requiring frequent rekeying of the SA, as
rollover of the ESP sequence number within a single SA is prohibited
for both ESPv2 [RFC2406] and ESPv3 [RFC4303] . In order to provide
the means to avoid this potentially undesirable frequent rekeying,
implementations that are capable of operating at speeds of 1 gigabit/
second or higher MUST implement extended (64-bit) sequence numbers
for ESPv2 (and ESPv3 if supported) and SHOULD use extended sequence
numbers for all block storage protocol traffic. Extended sequence
number negotiation as part of security association establishment is
specified in [RFC4304] for IKEv1 and [RFC5996] for IKEv2.
2.1. Data Origin Authentication and Data Integrity Transforms
RFC 3723 requires that:
o HMAC-SHA1 MUST be implemented in the form of HMAC-SHA-1-96
[RFC2404].
o AES CBC MAC with XCBC extensions SHOULD be implemented [RFC3566].
This document clarifies RFC 3723's key size requirements for
implementations of AES CBC MAC with XCBC extensions; 128-bit keys
MUST be supported, and other key sizes MAY also be supported.
This document also adds a requirement for IPsec v3:
o Implementations that support IKEv2 [RFC5996] SHOULD also implement
AES GMAC [RFC4543]. AES GMAC implementations MUST support 128-bit
keys, and MAY support other key sizes.
The rationale for the added requirement is that GMAC is more amenable
to hardware implementations that may be preferable for the high data
rates at which block storage protocols can be expected to operate.
2.2. Confidentiality Transform Requirements
RFC 3723 requires that:
o 3DES in CBC mode (3DES CBC) [RFC2451], [triple-des-spec] MUST be
supported.
o AES in Counter mode (AES CTR) [RFC3686], SHOULD be supported.
o NULL encryption [RFC2410] MUST be supported.
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The 3DES CBC and AES CTR requirements are replaced by requirements
that both MAY be implemented. The NULL encryption requirement is not
changed by this document. The 3DES CBC requirement matched the basic
encryption interoperability requirement for IPsec v2. At the time of
RFC 3723's publication, AES Counter mode was the encryption transform
that was most amenable to hardware implementation, as hardware
implementation may be preferable for the high data rates at which
block storage protocols can be expected to operate. This document
changes both of these requirements based on cryptographic
developments since the publication of RFC 3723.
The requirement for 3DES CBC has become problematic due to 3DES's
64-bit block size, i.e., the core cipher encrypts or decrypts 64 bits
at a time. Security weaknesses in encryption start to appear as the
amount of data encrypted under a single key approaches the birthday
bound of 32GiB for a cipher with a 64-bit block size, see Appendix A
and [triple-des-birthday]. It is prudent to rekey well before that
bound is reached, and 32GiB or some significant fraction thereof is
less than the amount of data that a block storage protocol may
transfer in a single session. This may require frequent rekeying,
e.g., to obtain an order of magnitude (10x) safety margin by rekeying
after 3GiB on a multi-gigabit/sec link. In contrast, AES has a 128
bit block size, which results in a much larger birthday bound (2^68
bytes), see Appendix A. AES CBC [RFC3602] is the primary mandatory-
to-implement encryption transform for interoperability, and hence is
the appropriate mandatory-to-implement transform replacement for 3DES
CBC.
AES Counter mode (AES CTR) is no longer the encryption transform that
is most amenable to hardware implementation. That characterization
now applies to AES Galois Counter Mode (GCM) [RFC4106], which
provides both encryption and integrity protection in a single
cryptographic mechanism (in contrast, neither HMAC-SHA1 nor AES CBC
MAC with XCBC extensions is well suited for hardware implementation,
as both transforms do not pipeline well). AES GCM is also capable of
providing confidentiality protection for the IKEv2 key exchange
protocol, but not the IKEv1 protocol [RFC5282], and therefore the new
AES GCM "SHOULD" requirement is based on presence of support for
IKEv2.
For the reasons described in the preceding paragraphs, the
confidentiality transform requirements in RFC 3723 are replaced by
the following:
o 3DES in CBC mode MAY be implemented (replaces RFC 3723's "MUST
implement" requirement).
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o AES in Counter mode (AES CTR) MAY be implemented (replaces RFC
3723's "SHOULD implement" requirement).
o AES in CBC mode MUST be implemented. AES CBC implementations MUST
support 128-bit keys and MAY support other key sizes.
o Implementations that support IKEv2 SHOULD also implement AES GCM.
AES GCM implementations MUST support 128-bit keys, and MAY support
other key sizes.
o NULL encryption [RFC2410] MUST be supported.
The requirement for support of NULL encryption enables use of SAs
that provide data origin authentication and data integrity, but not
confidentiality.
Other transforms MAY be implemented in addition to those listed
above.
3. IKEv1 and IKEv2 Requirements
Note: to avoid ambiguity, the original IKE protocol [RFC2409] is
referred to as "IKEv1" in this document.
This document adds requirements for IKEv2 usage with block Storage
protocols and makes the following two changes to the IKEv1
requirements in RFC 3723 (the new D-H group requirement also applies
to IKEv2):
o When D-H groups are used, a D-H group of at least 2048 bits SHOULD
be offered as a part of all proposals to create IPsec Security
Associations. The recommendation for use of 1024 bit D-H groups
with 3DES CBC and HMAC-SHA1 has been removed; use of 1024 bit D-H
groups is NOT RECOMMENDED, and
o The requirement to use UDP port 500 is removed in order to allow
NAT traversal [RFC3947].
There are no other changes to RFC 3723's IKEv1 requirements, but many
of them are restated in this document in order to provide context for
the new IKEv2 requirements.
RFC 3723 requires that IKEv1 [RFC2409] be supported for peer
authentication, negotiation of security associations, and key
management, using the IPsec DOI [RFC2407], and further requires that
manual keying not be used since it does not provide the rekeying
support necessary for operation at high data rates. This document
adds a requirement that IKEv2 [RFC5996] SHOULD be supported for peer
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authentication, negotiation of security associations, and key
management. The manual keying prohibition in RFC 3723 is extended to
IKEv2; manual keying MUST NOT be used with any version of IPsec for
protocols to which the requirements in this document apply.
RFC 3723's requirements for IKEv1 mode implementation and usage are
unchanged; this document does not extend those requirements to IKEv2
because IKEv2 does not have modes.
When IPsec is used, the receipt of an IKEv1 Phase 2 delete message or
an IKEv2 INFORMATIONAL exchange that deletes the SA SHOULD NOT be
interpreted as a reason for tearing down the block storage protocol
connection (e.g., TCP-based). If additional traffic is sent, a new
SA will be created to protect that traffic.
The method used to determine whether a block storage protocol
connection should be established using IPsec is regarded as an issue
of IPsec policy administration, and thus is not defined in this
document. The method used by an implementation that supports both
IPsec v2 and v3 to determine which versions of IPsec are supported by
the a block storage protocol peer is also regarded as an issue of
IPsec policy administration, and thus is also not defined in this
document. If both IPsec v2 and v3 are supported by both endpoints of
a block storage protocol connection, use of IPsec v3 is RECOMMENDED.
3.1. Authentication Requirements
The authentication requirements for IKEv1 are unchanged by this
document, but are restated here for context along with the
authentication requirements for IKEv2:
a. Peer authentication using a pre-shared cryptographic key MUST be
supported. Certificate-based peer authentication using digital
signatures MAY be supported. For IKEv1 ([RFC2409]), peer
authentication using the public key encryption methods specified
in sections 5.2 and 5.3 of [RFC2409] SHOULD NOT be used.
b. When digital signatures are used for authentication, all IKEv1
and IKEv2 negotiators SHOULD use Certificate Request Payload(s)
to specify the certificate authority, and SHOULD check the
cerificate validity via the pertinent Certificate Revocation List
(CRL) or via use of the Online Certificate Status Protocol (OCSP)
[RFC6960] before accepting a PKI certificate for use in
authentication. OCSP support within the IKEv2 protocol is
specified in [RFC4806].
c. IKEv1 implementations MUST support Main Mode and SHOULD support
Aggressive Mode. Main Mode with pre-shared key authentication
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method SHOULD NOT be used when either the initiator or the target
uses dynamically assigned IP addresses. While in many cases pre-
shared keys offer good security, situations in which dynamically
assigned addresses are used force the use of a group pre-shared
key, which creates vulnerability to a man-in-the-middle attack.
These requirements do not apply to IKEv2 because it has no modes.
d. In the IKEv1 Phase 2 Quick Mode, exchanges for creating the Phase
2 SA, the Identification Payload MUST be present. This
requirement does not apply to IKEv2 because it has no modes.
e. The following identification type requirements apply to IKEv1.
ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol stack supports IPv6)
and ID_FQDN Identification Types MUST be supported; ID_USER_FQDN
SHOULD be supported. The IP Subnet, IP Address Range,
ID_DER_ASN1_DN, and ID_DER_ASN1_GN Identification Types SHOULD
NOT be used. The ID_KEY_ID Identification Type MUST NOT be used.
f. When IKEv2 is supported, the following identification
requirements apply. ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol
stack supports IPv6) and ID_FQDN Identification Types MUST be
supported; ID_RFC822_ADDR SHOULD be supported. The
ID_DER_ASN1_DN, and ID_DER_ASN1_GN Identification Types SHOULD
NOT be used. The ID_KEY_ID Identification Type MUST NOT be used.
The reasons for the identification requirements in items e and f
above are:
o IP Subnet and IP Address Range are too broad to usefully identify
an iSCSI endpoint.
o The _DN and _GN types are X.500 identities; it is usually better
to use an identity from subjectAltName in a PKI certificate.
o ID_KEY_ID is an opaque identifier that is not interoperable among
different IPsec implementations as specified. Heterogeneity in
some block storage protocol implementations can be expected (e.g.,
iSCSI initiator vs. iSCSI target implementations), and hence
heterogeneity among IPsec implementations is important.
3.2. D-H Group and PRF Requirements
This document does not change the support requirements for Diffe-
Hellman (D-H) groups and Pseudo-Random Functions (PRFs). See
[RFC4109] for IKEv1 requirements and [RFC4307] for IKEv2
requirements. Implementors are advised to check for subsequent RFCs
that update either of these RFCs, as such updates may change these
requirements.
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When DH groups are used, a DH group of at least 2048 bits SHOULD be
offered as a part of all proposals to create IPsec Security
Associations for both IKEv1 and IKEv2.
RFC 3723 requires that the IKEv1 Quick Mode key exchange that
provides perfect forward secrecy MUST be implemented. This document
extends that requirement to IKEv2; the CREATE_CHILD_SA key exchange
that provides perfect forward secrecy MUST be implemented for use of
IPsec with block storage protocols.
4. IANA Considerations
This document includes no request to IANA.
5. Security Considerations
This entire document is about security.
The security considerations sections of all of the referenced RFCs
apply, and particular note should be taken of the security
considerations for the encryption transforms whose requirement levels
are changed by this RFC:
o AES GMAC [RFC4543] (new requirement - SHOULD be supported when
IKEv2 is supported),
o 3DES CBC [RFC2451] (changed from "MUST be supported" to "MAY be
supported"),
o AES CTR [RFC3686] (changed from "SHOULD be supported" to "MAY be
supported"),
o AES CBC [RFC3602] (new requirement - MUST be supported), and
o AES GCM [RFC4106] (new requirement - SHOULD be supported when
IKEv2 is supported).
Of particular interest are the security considerations concerning the
use of AES GCM[RFC4106] and AES GMAC[RFC4543]; both modes are
vulnerable to catastrophic forgery attacks if a nonce is ever
repeated with a given key.
The requirement level for 3DES CBC has been reduced based on
considerations for high speed implementations; 3DES CBC remains an
optional encryption transform that may be suitable for
implementations limited to operating at lower speeds where the
required rekeying frequency for 3DES is acceptable.
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The requirement level for AES CTR has been reduced based solely on
hardware implementation considerations that favor AES GCM, as opposed
to changes in AES CTR's security properties. AES CTR remains an
optional security transform that is suitable for use in general as it
does not share 3DES CBC's requirement for frequent rekeying when
operating at high data rates.
Key sizes with comparable strength SHOULD be used for the
cryptographic algorithms and transforms for any individual IPsec
security association. See Section 5.6 of [SP800-57] for further
discussion.
6. References
6.1. Normative References
[I-D.ietf-storm-iscsi-cons]
Chadalapaka, M., Satran, J., Meth, K., and D. Black,
"iSCSI Protocol (Consolidated)", draft-ietf-storm-iscsi-
cons-10 (work in progress), July 2013.
[I-D.ietf-storm-iser]
Ko, M. and A. Nezhinsky, "iSCSI Extensions for RDMA
Specification", draft-ietf-storm-iser-15 (work in
progress), July 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, November 1998.
[RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[RFC2407] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, November 1998.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and
Its Use With IPsec", RFC 2410, November 1998.
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[RFC2451] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
Algorithms", RFC 2451, November 1998.
[RFC3566] Frankel, S. and H. Herbert, "The AES-XCBC-MAC-96 Algorithm
and Its Use With IPsec", RFC 3566, September 2003.
[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher
Algorithm and Its Use with IPsec", RFC 3602, September
2003.
[RFC3686] Housley, R., "Using Advanced Encryption Standard (AES)
Counter Mode With IPsec Encapsulating Security Payload
(ESP)", RFC 3686, January 2004.
[RFC3720] Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M.,
and E. Zeidner, "Internet Small Computer Systems Interface
(iSCSI)", RFC 3720, April 2004.
[RFC3723] Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
Travostino, "Securing Block Storage Protocols over IP",
RFC 3723, April 2004.
[RFC3821] Rajagopal, M., Rodriguez, E., and R. Weber, "Fibre Channel
Over TCP/IP (FCIP)", RFC 3821, July 2004.
[RFC3822] Peterson, D., "Finding Fibre Channel over TCP/IP (FCIP)
Entities Using Service Location Protocol version 2
(SLPv2)", RFC 3822, July 2004.
[RFC3947] Kivinen, T., Swander, B., Huttunen, A., and V. Volpe,
"Negotiation of NAT-Traversal in the IKE", RFC 3947,
January 2005.
[RFC4018] Bakke, M., Hufferd, J., Voruganti, K., Krueger, M., and T.
Sperry, "Finding Internet Small Computer Systems Interface
(iSCSI) Targets and Name Servers by Using Service Location
Protocol version 2 (SLPv2)", RFC 4018, April 2005.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)", RFC
4106, June 2005.
[RFC4109] Hoffman, P., "Algorithms for Internet Key Exchange version
1 (IKEv1)", RFC 4109, May 2005.
[RFC4172] Monia, C., Mullendore, R., Travostino, F., Jeong, W., and
M. Edwards, "iFCP - A Protocol for Internet Fibre Channel
Storage Networking", RFC 4172, September 2005.
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[RFC4173] Sarkar, P., Missimer, D., and C. Sapuntzakis,
"Bootstrapping Clients using the Internet Small Computer
System Interface (iSCSI) Protocol", RFC 4173, September
2005.
[RFC4174] Monia, C., Tseng, J., and K. Gibbons, "The IPv4 Dynamic
Host Configuration Protocol (DHCP) Option for the Internet
Storage Name Service", RFC 4174, September 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, 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.
[RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the
Internet Key Exchange Version 2 (IKEv2)", RFC 4307,
December 2005.
[RFC4543] McGrew, D. and J. Viega, "The Use of Galois Message
Authentication Code (GMAC) in IPsec ESP and AH", RFC 4543,
May 2006.
[RFC5040] Recio, R., Metzler, B., Culley, P., Hilland, J., and D.
Garcia, "A Remote Direct Memory Access Protocol
Specification", RFC 5040, October 2007.
[RFC5041] Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
Data Placement over Reliable Transports", RFC 5041,
October 2007.
[RFC5042] Pinkerton, J. and E. Deleganes, "Direct Data Placement
Protocol (DDP) / Remote Direct Memory Access Protocol
(RDMAP) Security", RFC 5042, October 2007.
[RFC5043] Bestler, C. and R. Stewart, "Stream Control Transmission
Protocol (SCTP) Direct Data Placement (DDP) Adaptation",
RFC 5043, October 2007.
[RFC5044] Culley, P., Elzur, U., Recio, R., Bailey, S., and J.
Carrier, "Marker PDU Aligned Framing for TCP
Specification", RFC 5044, October 2007.
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[RFC5046] Ko, M., Chadalapaka, M., Hufferd, J., Elzur, U., Shah, H.,
and P. Thaler, "Internet Small Computer System Interface
(iSCSI) Extensions for Remote Direct Memory Access
(RDMA)", RFC 5046, October 2007.
[RFC5048] Chadalapaka, M., "Internet Small Computer System Interface
(iSCSI) Corrections and Clarifications", RFC 5048, October
2007.
[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption
Algorithms with the Encrypted Payload of the Internet Key
Exchange version 2 (IKEv2) Protocol", RFC 5282, August
2008.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
5996, September 2010.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, June 2013.
[SP800-57]
Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid,
"NIST Special Publication 800-57: Recommendation for Key
Management - Part 1: General (Revision 3)", July 2012,
<http://csrc.nist.gov/publications/nistpubs/800-57/
sp800-57_part1_rev3_general.pdf>.
[triple-des-birthday]
McGrew, D., "Impossible plaintext cryptanalysis and
probable-plaintext collision attacks of 64-bit block
cipher modes (Cryptology ePrint Archive: Report 2012/
623)", November 2012, <http://eprint.iacr.org/2012/623>.
[triple-des-spec]
American Bankers Association, ABA., "American National
Standard for Financial Services X9.52-1998 - Triple Data
Encryption Algorithm Modes of Operation", July 1998.
6.2. Informative References
[RFC3721] Bakke, M., Hafner, J., Hufferd, J., Voruganti, K., and M.
Krueger, "Internet Small Computer Systems Interface
(iSCSI) Naming and Discovery", RFC 3721, April 2004.
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[RFC4806] Myers, M. and H. Tschofenig, "Online Certificate Status
Protocol (OCSP) Extensions to IKEv2", RFC 4806, February
2007.
[RFC5045] Bestler, C. and L. Coene, "Applicability of Remote Direct
Memory Access Protocol (RDMA) and Direct Data Placement
(DDP)", RFC 5045, October 2007.
[RFC5047] Chadalapaka, M., Hufferd, J., Satran, J., and H. Shah,
"DA: Datamover Architecture for the Internet Small
Computer System Interface (iSCSI)", RFC 5047, October
2007.
[RFC5387] Touch, J., Black, D., and Y. Wang, "Problem and
Applicability Statement for Better-Than-Nothing Security
(BTNS)", RFC 5387, November 2008.
Appendix A. Block Cipher Birthday Bounds
This Appendix provides the birthday bounds for the 3DES and AES
ciphers based on [triple-des-birthday], which states: "Theory advises
against using a w-bit block cipher to encrypt more than 2^(w/2)
blocks with a single key; this is known as the birthday bound."
For a cipher with a 64-bit block size (e.g., 3DES), w=64, so the
birthday bound is 2^32 blocks. As each block contains 8 (2^3) bytes,
the birthday bound is 2^35 bytes = 2^5 gibibytes, i.e., 32 GiB, where
1 gibibyte (GiB) = 2^30 bytes. Note that a gigabyte (decimal
quantity) is not the same as a gibibyte (binary quantity), 1 gigabyte
(GB) = 10^6 bytes.
For a cipher with a 128-bit block size (e.g., AES), w=128, so the
birthday bound is 2^64 blocks. As each block contains 16 (2^4)
bytes, the birthday bound is 2^68 bytes = 2^8 exbibytes, i.e., 256
EiB, where 1 exbibyte (EiB) = 2^60 bytes. Note that an exabyte
(decimal quantity) is not the same as an exbibyte (binary quantity),
1 exabyte (EB) = 10^9 bytes.
Appendix B. Contributors
David McGrew's observations about the birthday bound implications of
3DES's 64-bit block size on the ipsec@ietf.org mailing list lead to
changing from 3DES CBC to AES CBC as the mandatory to implement
encryption algorithm based on the birthday bound discussion in
Appendix A.
The original authors of RFC 3723 were: Bernard Aboba, Joshua Tseng,
Jesse Walker, Venkat Rangan and Franco Travostino. Comments from
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Francis Dupont, Yaron Sheffer, Tom Talpey, Sean Turner and Tom Yu
have improved this document and are gratefully acknowledged.
Appendix C. Change Log
This section should be removed before this document is published as
an RFC
Changes from -00 to -01:
o Make it clearer that RFC 3723's encryption implementation
requirements are being changed.
o State that D-H group and PRF implementation requirements are
unchanged and provide references to RFCs where they can be found
(new section 3.2).
o Add requirements for perfect forward secrecy implementation (also
in 3.2).
o Use the correct GMAC reference.
o Many other editorial changes.
Changes from -01 to -02.
o Remove "IP Storage" terminology, use "Block Storage" in title and
body, based on RFC 3723.
o Add appendix on birthday bound calculations.
o Clean up and tighten requirements text, with a focus on making key
size requirements clearer.
o Add summary of changes from RFC 3723.
o Many other editorial changes.
Changes from -02 to -03
o Editorial changes
Changes from -03 to -04
o Extend ESN requirement to ESPv2.
o Allow OCSP in addition to CRLs to check certificates.
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o Add security considerations text, primarily on changes to
encryption requirements.
o Editorial changes
Authors' Addresses
David Black
EMC
176 South Street
Hopkinton, MA 01748
USA
Phone: +1 508 293-7953
Email: david.black@emc.com
Paul Koning
Dell
300 Innovative Way
Nashua, NH 03062
USA
Phone: +1 603 249-7703
Email: paul_koning@Dell.com
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