Internet DRAFT - draft-weis-gdoi-iec62351-9
draft-weis-gdoi-iec62351-9
Network Working Group B. Weis
Internet-Draft M. Seewald
Intended status: Standards Track Cisco Systems
Expires: May 1, 2017 H. Falk
SISCO
October 28, 2016
GDOI Protocol Support for IEC 62351 Security Services
draft-weis-gdoi-iec62351-9-10
Abstract
The IEC 61850 power utility automation family of standards describe
methods using Ethernet and IP for distributing control and data
frames within and between substations. The IEC 61850-90-5 and IEC
62351-9 standards specify the use of the Group Domain of
Interpretation (GDOI) protocol (RFC 6407) to distribute security
transforms for some IEC 61850 security protocols. This memo defines
GDOI payloads to support those security protocols.
Status of This Memo
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This Internet-Draft will expire on May 1, 2017.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Acronyms and Abbreviations . . . . . . . . . . . . . . . 4
2. IEC 61850 Protocol Information . . . . . . . . . . . . . . . 4
2.1. ID Payload . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. SA TEK Payload . . . . . . . . . . . . . . . . . . . . . 6
2.3. KD Payload . . . . . . . . . . . . . . . . . . . . . . . 10
3. Security Considerations . . . . . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . 16
6.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Example ID, SA TEK, and KD payloads for IEC 61850 . 18
Appendix B. Implementation Considerations . . . . . . . . . . . 23
B.1. DER Length Fields . . . . . . . . . . . . . . . . . . . . 23
B.2. Groups with Multiple Senders . . . . . . . . . . . . . . 23
Appendix C. Data Attribute Format . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
Power substations use Generic Object Oriented Substation Events
(GOOSE) protocol [IEC-61850-8-1] to distribute control information to
groups of devices using a multicast strategy. Sources within the
power substations also distribute IEC 61850-9-2 sampled values data
streams [IEC-61850-9-2]. The IEC 62351-9 standard [IEC-62351-9]
describes key management methods for the security methods protecting
these IEC 61850 messages, including methods of device authentication
and authorization, and methods of policy and keying material
agreement for IEC 61850 message encryption and data integrity
protection. These key management methods include the use of GDOI
[RFC6407] to distribute the security policy and session keying
material used to protect IEC 61850 messages when the messages are
sent to a group of devices.
The protection of the messages is defined within IEC 62351-6
[IEC-62351-6], IEC 61850-8-1 [IEC-61850-8-1], and IEC 61850-9-2
[IEC-61850-9-2]. Protected IEC 61850 messages typically include the
output of a Message Authentication Code (MAC) and may also be
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encrypted using a symmetric cipher such as the Advanced Encryption
Standard (AES).
Section 5.5.2 of RFC 6407 specifies that the following information
needs to be provided in order to fully define a new Security
Protocol:
o The Protocol-ID for the particular Security Protocol.
o The SPI Size
o The method of SPI generation
o The transforms, attributes, and keys needed by the Security
Protocol.
This document defines GDOI payloads to distribute policy and keying
material to protect IEC 61850 messages, and defines the necessary
information to ensure interoperability between IEC 61850
implementations.
This memo extends RFC 6407 in order to define extensions needed by
IEC 62351-9. With the current IANA registry rules setup by RFC 6407,
this requires a standards action by the IETF - essentially that means
the production of this document. As the relevant IEC specifications
are not available to the IETF community, it is not possible for this
RFC to fully describe the security considerations applying.
Implementers therefore need to depend on the security analysis within
the IEC specifications. As two different Standards Development
Organizations are involved here, and since group key management is
inherently complex, it is possible some security issues have not been
identified, so additional analysis of the security of the combined
set of specifications may be advisable.
1.1. Requirements notation
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
[RFC2119].
1.2. Terminology
The following key terms are used throughout this document:
Generic Object Oriented Substation Events: Power substation control
model defined as per IEC 61850.
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IEC 61850 message: A message in the IEC 61850 family of protocols
carrying control or data between Substation devices.
1.3. Acronyms and Abbreviations
The following acronyms and abbreviations are used throughout this
document
AES Advanced Encryption Standard
GCKS Group Controller/Key Server
GDOI Group Domain of Interpretation
GM Group Member
GOOSE Generic Object Oriented Substation Events
KD Key Download
KEK Key Encryption Key
MAC Message Authentication Code
SA Security Association
SPI Security Parameter Index
TEK Traffic Encryption Key
2. IEC 61850 Protocol Information
The following sections describe the GDOI payload extensions that are
needed in order to distribute security policy and keying material for
the IEC 62351 Security Services. The Identification (ID) Payload is
used to describe an IEC 62351 GDOI group. The Security Association
(SA) Traffic Encryption Key (TEK) payload is used to describe the
policy defined by a Group Controller/Key Server (GCKS) for a
particular IEC 62351 traffic selector. No changes are required to
the Key Download (KD) Payload, but a mapping of IEC 62351 keys to KD
Payload key types is included.
All multioctet fields are in network byte order.
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2.1. ID Payload
The ID payload in a GDOI GROUPKEY-PULL exchange allows the Group
Member (GM) to declare the group it would like to join. A group is
defined by an ID payload as defined in GDOI [RFC6407] and reproduced
in Figure 1.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! ID Type ! DOI-Specific ID Data = 0 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
~ Identification Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 1: RFC 6407 Identification Payload
An ID Type name of ID_OID (value 13) is defined in this memo to
specify an Object Identifier (OID) [ITU-T-X.683] encoded using
Distinguished Encoding Rules (DER) [ITU-T-X.690]. Associated with
the OID may be an OID Specific Payload DER encoded as further
defining the group. Several OIDs are specified in [IEC-62351-9] for
use with IEC 61850. Each OID represents a GOOSE or Sampled Value
protocol, and in some cases IEC 61850 also specifies a particular
multicast destination address to be described in the OID Specific
Payload field. The format of the ID_OID Identification Data is
specified as shown in Figure 2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Length ! OID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Specific Payload Length ! OID Specific Payload ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 2: ID_OID Identification Data
The ID_OID Identification Data fields are defined as follows:
o OID Length (1 octet) -- Length of the OID field.
o OID (variable) -- An ASN.1 ObjectIdentifier encoded using DER
[ITU-T-X.690].
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o OID Specific Payload Length (2 octets) -- Length of the OID
Specific Payload. Set to zero if the OID does not require an OID
Specific Payload.
o OID Specific Payload (variable) -- OID specific selector encoded
in DER. If OID Specific Payload Length is set to zero this field
does not appear in the ID payload.
2.2. SA TEK Payload
The SA TEK payload contains security attributes for a single set of
policy associated with a group TEK. The type of policy to be used
with the TEK is described by a Protocol-ID field included in the SA
TEK. As shown in Figure 3 reproduced from RFC 6407, each Protocol-ID
describes a particular TEK Protocol-Specific Payload definition.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Protocol-ID ! TEK Protocol-Specific Payload ~
+-+-+-+-+-+-+-+-+ ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 3: RFC 6407 SA TEK Payload
The Protocol-ID name of GDOI_PROTO_IEC_61850 (value TBD1) is defined
in this memo for the purposes of distributing IEC 61850 policy. A
GDOI_PROTO_IEC_61850 SA TEK includes an OID and (optionally) an OID
Specific Payload that together define the selectors for the network
traffic. The selector fields are followed by security policy fields
indicating how the specified traffic is to be protected. The
GDOI_PROTO_IEC_61850 TEK Protocol-Specific Payload is defined as
shown in Figure 4.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Length ! OID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Specific Payload Length ! OID Specific Payload ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Auth Alg ! Enc Alg !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Remaining Lifetime Value !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SA Data Attributes ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 4: IEC-61850 SA TEK Payload
The GDOI_PROTO_IEC_61850 SA TEK Payload fields are defined as
follows:
o OID Length (1 octet) -- Length of the OID field.
o OID (variable) -- An ASN.1 ObjectIdentifier encoded using DER.
OIDs defined in IEC 61850 declare the type of IEC 61850 message to
be protected, as defined by [IEC-62351-9].
o OID Specific Payload Length (2 octets) -- Length of the OID
Specific Payload. This field is set to zero if the policy does
not include an OID Specific Payload.
o OID Specific Payload (variable) -- The traffic selector (e.g.,
multicast address) specific to the OID encoded using DER. Some
OID policy settings do not require the use of an OID Specific
Payload, in which case this field is not included in the TEK and
the OID Specific Payload Length is set to zero.
o SPI (4 octets) -- Identifier for the Current Key. This field
represents a SPI.
o Auth Alg (2 octets) -- Authentication Algorithm ID. Valid values
are define in Section 2.2.2.
o Enc Alg (2 octets) -- Confidentiality Algorithm ID. Valid values
are define in Section 2.2.3.
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o Remaining Lifetime value (4 octets) -- The number of seconds
remaining before this TEK expires. A value of zero (0) shall
indicate that the TEK does not have an expire time.
o SA Data Attributes (variable length) -- Contains zero or more
attributes associated with this SA. Section Section 2.2.4 defines
attributes.
2.2.1. Selectors
The OID and (optionally) an OID Specific Payload that together define
the selectors for the network traffic. While they may match the OID
and OID Specific Payload that the GM had previously requested in the
ID payload, there is no guarantee that this will be the case.
Including selectors in the SA TEK is important for at least the
following reasons:
o The KS policy may direct the KS to return multiple TEKs, each
representing different traffic selectors and it is important that
every GM receiving the set of TEKs explicitly identify the traffic
selectors associated with the TEK.
o The KS policy may include the use of a GDOI GROUPKEY-PUSH message,
which distributes new or replacement TEKs to group members. Since
the GROUPKEY-PUSH message does not contain an ID payload the TEK
definition must include the traffic selectors.
2.2.2. Authentication Algorithms
This memo defines the following Authentication Algorithms for use
with this TEK. These algorithms are defined in [IEC-TR-61850-90-5],
including requirements on one or more algorithms defined as mandatory
to implement.
o NONE. Specifies that a Authentication Algorithm is not required,
or when the accompanying confidentiality algorithm includes
authentication (e.g., AES-GCM-128). See Section 3 for cautionary
notes regarding using this value without any confidentiality
algorithm.
o HMAC-SHA256-128. Specifies the use of SHA-256 [FIPS180-3.2008]
combined with HMAC [RFC2104]. The output is truncated to 128
bits, as per [RFC2104]. The key size is the size of the hash
value produced by SHA-256 (256 bits).
o HMAC-SHA256. Specifies the use of SHA-256 [FIPS180-3.2008]
combined with HMAC [RFC2104]. The key size is the size of the
hash value produced by SHA-256 (256 bits).
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o AES-GMAC-128. Specifies the use of AES [FIPS197] in the Galois
Message Authentication Code (GMAC) mode [SP.800-38D] with a 128
bit key size.
o AES-GMAC-256. Specifies the use of AES [FIPS197] in the Galois
Message Authentication Code (GMAC) mode [SP.800-38D] with a 256
bit key size.
2.2.3. Confidentiality Algorithms
This memo defines the following Confidentiality Algorithms for use
with this TEK. These algorithms are defined in [IEC-TR-61850-90-5],
including requirements on one or more algorithms defined as mandatory
to implement.
o NONE. Specifies that Confidentiality is not required. NOTE: See
Section 3 for guidance for cautionary notes regarding using this
value.
o AES-CBC-128. Specifies the use of AES [FIPS197] in the Cipher
Block Chaining (CBC) mode [SP.800-38A] with a 128 bit key size.
This encryption algorithm does not provide authentication and MUST
NOT be used with the NONE Authentication Algorithm.
o AES-CBC-256. Specifies the use of AES [FIPS197] in the Cipher
Block Chaining (CBC) mode [SP.800-38A] with a 256 bit key size.
This encryption algorithm does not provide authentication and MUST
NOT be used with the NONE Authentication Algorithm.
o AES-GCM-128. Specifies the use of AES [FIPS197] in the Galois/
Counter Mode (GCM) mode [SP.800-38D] with a 128 bit key size.
This encryption algorithm provides authentication and is used with
a NONE Authentication Algorithm.
o AES-GCM-256. Specifies the use of AES [FIPS197] in the Galois/
Counter Mode (GCM) mode [SP.800-38D] with a 256 bit key size.
This encryption algorithm provides authentication and is used with
a NONE Authentication Algorithm.
2.2.4. SA Attributes
The following attributes may be present in an SA TEK. The attributes
must follow the format described in Appendix C).
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2.2.4.1. SA Time Activation Delay (SA_ATD)
A GCKS will sometimes distribute an SA TEK in advance of when it is
expected to be used. This is communicated to group members using the
SA Activation Time Delay (SA_ATD) attribute. When a GM receives an
SA_TEK with this attribute, it waits for the number of seconds
contained within the attribute before installing it for either
transmission or receiving.
This Activation Time Delay attribute applies only this SA, and MAY be
used in either a GROUPKEY-PULL or GROUPKEY-PUSH exchange. RFC 6407
also describe an ACTIVATION_TIME_DELAY attribute for the Group
Associated Policy (GAP) payload, which is applied to all Security
Associations and restricted to use in a GROUPKEY-PUSH message. If
both attributes are included in a GROUPKEY-PUSH payload, the value
contained in SA_ATD will be used.
2.2.4.2. Key Delivery Assurance (SA_KDA)
Group policy can include notifying a multicast source ("Publisher")
of an indication of whether multicast receivers ("Subscribers") have
previously received the SA TEK. This notification allows a Publisher
to set a policy as to whether to activate the new SA TEK or not based
on the percentage of Subscribers that are able to receive packets
protected by the SA TEK. The attribute value is a number between 0
and 100 (inclusive).
2.2.5. SPI Discussion
As noted in Section 1, RFC 6407 requires that characteristics of a
SPI must be defined. A SPI in a GDOI_PROTO_IEC_61850 SA TEK is
represented as a Key Identifier (KeyID). The SPI size is 4 octets.
The SPI is unilaterally chosen by the GCKS using any method chosen by
the implementation. However, an implementation needs to take care
not to duplicate a SPI value that is currently in use for a
particular group.
2.3. KD Payload
The KD Payload contains group keys for the policy specified in the SA
Payload. It is comprised of a set of Key Packets, each of which hold
the keying material associated with a SPI (i.e., an IEC 61850 Key
Identifier). The RFC 6407 KD payload format is reproduced in
Figure 5.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Number of Key Packets ! RESERVED2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
~ Key Packets ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 5: KD Payload
Each Key Packet holds the keying material associated with a
particular IEC 61850 Key Identifier, although GDOI refers to it as a
SPI. The keying material is described in a set of attributes
indicating an encryption key, integrity key, etc., in accordance with
the security policy of the group as defined by the associated SA
Payload. Each Key Packet has the following format, reproduced in
Figure 6.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! KD Type ! RESERVED ! Key Packet Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI Size ! SPI (variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
~ Key Packet Attributes ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 6: Key Packet
No changes are needed to GDOI in order to distribute IEC 61850 keying
material, but the keys MUST be distributed as defined in Section 5.6
of RFC 6407. The KD Type MUST be TEK (1).
A key associated with an IEC 61850 Authentication Algorithm
(distributed in the Auth Alg field) MUST be distributed as a
TEK_INTEGRITY_KEY attribute. The value of the attribute is
interpreted according to the type of key distributed in the SA TEK:
o HMAC-SHA256-128, HMAC-SHA256. The value is 32 octets.
o AES-GMAC-128. The value is 20 octets. The first 16 octets are
the 128-bit AES key, and the remaining four octets are used as the
salt value in the nonce.
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o AES-GMAC-256. The value is 36 octets. The first 32 octets are
the 256-bit AES key, and the remaining four octets are used as the
salt value in the nonce.
A key associated with an IEC 61850 Confidentiality Algorithm
(distributed in the Enc Alg SA TEK field) MUST be distributed as a
TEK_ALGORITHM_KEY attribute. The value of the attribute is
interpreted according to the type of key distributed in the SA TEK:
o AES-CBC-128. The value is 16 octets.
o AES-CBC-256. The value is 32 octets.
o AES-GCM-128. The value is 20 octets. The first 16 octets are the
128-bit AES key, and the remaining four octets are used as the
salt value in the nonce.
o AES-GCM-256. The value is 36 octets. The first 32 octets are the
256-bit AES key, and the remaining four octets are used as the
salt value in the nonce.
3. Security Considerations
GDOI is a security association (SA) management protocol for groups of
senders and receivers. This protocol performs authentication of
communicating protocol participants (Group Member, Group Controller/
Key Server). GDOI provides confidentiality of key management
messages, and it provides source authentication of those messages.
GDOI includes defenses against man-in-middle, connection hijacking,
replay, reflection, and denial-of-service (DOS) attacks on unsecured
networks. GDOI assumes the network is not secure and may be under
the complete control of an attacker. The Security Considerations
described in RFC 6407 are relevant to the distribution of GOOSE and
sampled values policy as defined in this memo.
Message Authentication is an optional property for IEC 62351 Security
Services, however when encryption is used authentication MUST also be
provided by using an authenticated encryption algorithm such as AES-
GCM-128 or by using a specific authentication algorithm such as HMAC-
SHA-256. Setting the Authentication Algorithm to NONE, but setting
the Confidentiality Algorithm to an algorithm that does not include
authentication (i.e., is marked with an N in the "Authenticated
Encryption" column of the IEC62351-9 Confidentiality Values IANA
Registry) is not safe, and MUST NOT be used.
When Message Authentication is used, a common practice is to truncate
the output of a MAC and include part of the bits in the integrity
protection field of the data security transform. Current guidance in
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[RFC2104] is to truncate no less than half of the length of the hash
output. The authentication algorithm HMAC-SHA256-128 defined in this
memo truncates the output to exactly half of the output, which
follows this guidance.
Confidentiality is an optional security property for IEC 62351
Security Services. Confidentiality Algorithm IDs SHOULD be included
in the IEC-61850 SA TEK Payload if the IEC 61850 messages are
expected to traverse public network links and not protected by
another level of encryption (e.g., an encrypted Virtual Private
Network). Current cryptographic advice indicates that the use of
AES-CBC-128 for confidentiality is sufficient for the foreseeable
future [SP.800-131], but some security policies may require the use
of AES-CBC-256.
IEC 62351 Security Services describes a variety of policy choices for
protecting network traffic, including the option of specifying no
protection at all. This is enabled with the use of NONE as an
Authentication Algorithm and/or Confidentiality Algorithm. The
following guidance is given regarding the use of NONE.
o Setting both Authentication Algorithm and Confidentiality
Algorithm to NONE is possible, but NOT RECOMMENDED. Setting such
a policy is sometimes necessary during a migration period, when
traffic is being protected incrementally and some traffic has not
yet been scheduled for protection. Alternatively, site security
policy for some packet flows requires inspection of packet data on
the private network followed by network-layer encryption before
delivery to a public network.
o Setting the Confidentiality Algorithm to NONE, but setting the
Authentication Algorithm to a MAC can be an acceptable policy in
the following conditions: the disclosed information in the data
packets is comprised of raw data values, and the disclosure of the
data files is believed to be of no more value to an observer than
traffic analysis on the frequency and size of packets protected
for confidentiality. Alternatively, site security policy for some
packet flows requires inspection of packet data on the private
network followed by network-layer encryption before delivery to a
public network.
o Setting the Authentication Algorithm to NONE, but setting the
Confidentiality Algorithm to an algorithm that does not includes
authentication is not safe, and MUST NOT be used.
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4. IANA Considerations
The following additions are made to the GDOI payloads registry
[GDOI-REG].
A new SA TEK Payload Values - Protocol-ID value is defined. Its type
is GDOI_PROTO_IEC_61850, with a value of TBD1.
A new registry is added defining Auth Alg values. The Attribute
Class is called "IEC62351-9 Authentication Values". The terms
Reserved, Expert Review and Private Use are to be applied as defined
in [RFC5226].
Name Value
---- -----
Reserved 0
NONE 1
HMAC-SHA256-128 2
HMAC-SHA256 3
AES-GMAC-128 4
AES-GMAC-256 5
Expert Review 6-61439
Private Use 61440-65535
A new registry is added defining Enc Alg values. The Attribute Class
is called "IEC62351-9 Confidentiality Values". The terms Expert
Review and Private Use are to be applied as defined in [RFC5226].
Name Value Authenticated Encryption
---- ----- ------------------------
Reserved 0
NONE 1
AES-CBC-128 2 N
AES-CBC-256 3 N
AES-GCM-128 4 Y
AES-GCM-256 5 Y
Expert Review 6-61439
Private Use 61440-65535
A new registry for SA TEK attributes is defined. The Attribute call
is called "GDOI SA TEK Attributes". The terms Expert Review and
Expert Review are to be applied as defined in [RFC5226]. In the
table, attributes that are defined as TV are marked as Basic (B);
attributes that are defined as TLV are marked as Variable (V).
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Attribute Value Type
--------- ----- ----
Reserved 0
SA_ATD 1 V
SA_KDA 2 B
Expert Review 3-28671
Private Use 28672-32767
A new registry for ID Types is defined for the Identification Payload
when the DOI is GDOI. The registry is taken from the ID Types
registry for the IPsec DOI, which were previously assumed. Values
1-12 are defined identically to the equivalent values in the IPsec
DOI. Value 13 is defined in this memo. The terms Expert Review and
Private Use are to be applied as defined in [RFC5226].
Name Value
---- -----
Reserved 0
ID_IPV4_ADDR 1
ID_FQDN 2
ID_USER_FQDN 3
ID_IPV4_ADDR_SUBNET 4
ID_IPV6_ADDR 5
ID_IPV6_ADDR_SUBNET 6
ID_IPV4_ADDR_RANGE 7
ID_IPV6_ADDR_RANGE 8
ID_DER_ASN1_DN 9
ID_DER_ASN1_GN 10
ID_KEY_ID 11
ID_LIST 12
ID_OID 13
Expert Review 14-61439
Private Use 61440-65535
5. Acknowledgements
The authors thanks Sean Turner, Steffen Fries, Yoav Nir, Vincent
Roca, Dennis Bourget, and David Boose for their thoughtful reviews,
each of which resulted in substantial improvements to the memo. Joe
Salowey provided valuable guidance as document shepherd during the
publication process. The authors are indebted to Kathleen Moriarty
for her agreement to sponsor the publication of the document.
6. References
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6.1. Normative References
[IEC-62351-9]
International Electrotechnical Commission, "IEC 62351 Part
9 - Key Management", IEC 62351-9 , January 2013.
[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>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011, <http://www.rfc-editor.org/info/rfc6407>.
6.2. Informative References
[FIPS180-3.2008]
National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-3, October 2008,
<http://csrc.nist.gov/publications/fips/fips180-3/
fips180-3_final.pdf>.
[FIPS197] "Advanced Encryption Standard (AES)", United States of
America, National Institute of Science and
Technology, Federal Information Processing Standard (FIPS)
197, November 2001.
[GDOI-REG]
Internet Assigned Numbers Authority, "Group Domain of
Interpretation (GDOI) Payload Type Values", IANA Registry,
December 2004, <http://www.iana.org/assignments/gdoi-
payloads/gdoi-payloads.xml>.
[IEC-61850-8-1]
International Electrotechnical Commission, "Specific
Communication networks and systems for power utility
automation - Part 8-1: Specific communication service
mapping (SCSM) - Mappings to MMS (ISO 9506-1 and ISO
9506-2) and to ISO/IEC 8802-3", IEC-61850-8-1 , June 2011.
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[IEC-61850-9-2]
International Electrotechnical Commission, "Communication
networks and systems for power utility automation - Part
9-2: Specific communication service mapping (SCSM) -
Sampled values over ISO/IEC 8802-3", IEC-61850-2 ,
September 2011.
[IEC-62351-6]
International Electrotechnical Commission, "Power systems
management and associated information exchange - Data and
communications security - Part 6: Security for IEC 61850",
IEC-62351-6 , June 2007.
[IEC-TR-61850-90-5]
International Electrotechnical Commission, "Communication
networks and systems for power utility automation - Part
90-5: Use of IEC 61850 to transmit synchrophasor
information according to IEEE C37.118", IEC 62351-9 , May
2012.
[ITU-T-X.683]
"Information technology - Abstract Syntax Notation One
(ASN.1): Parameterization of ASN.1 specifications", SERIES
X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS OSI
networking and system aspects - Abstract Syntax Notation
One (ASN.1) , July 2002, <http://www.itu.int/ITU-
T/studygroups/com17/languages/X.683-0207.pdf>.
[ITU-T-X.690]
"Information technology-ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", SERIES X: DATA NETWORKS, OPEN SYSTEM
COMMUNICATIONS AND SECURITY OSI networking and system
aspects - Abstract Syntax Notation One (ASN.1) , 2008,
<https://www.itu.int/rec/T-REC-X.690-200811-I>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>.
[SP.800-131]
Barker, E. and A. Roginsky, "Recommendation for the
Transitioning of Cryptographic Algorithms and Key
Lengths", United States of America, National Institute of
Science and Technology DRAFT NIST Special Publication
800-131, June 2010.
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[SP.800-38A]
Dworkin, M., "Recommendation for Block Cipher Modes of
Operation", United States of America, National Institute
of Science and Technology, NIST Special Publication
800-38A 2001 Edition, December 2001.
[SP.800-38D]
Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) and GMAC", United
States of America, National Institute of Science and
Technology, NIST Special Publication 800-38D, November
2007.
Appendix A. Example ID, SA TEK, and KD payloads for IEC 61850
An IED begins a GROUPKEY-PULL exchange and requests keys and security
policy for 61850_UDP_ADDR_GOOSE (OID = 1.2.840.10070.61850.8.1.2 as
defined in [IEC-61850-9-2]) and IP multicast address 233.252.0.1
encoded as specified in [IEC-61850-9-2].
OID and OID Specific Payload protocol fields are variable length
fields. To improve readability, their representations in Figure 7
and Figure 8 are "compressed" in the figure, as indicated by a
trailing "~" for these fields. Implementations should be aware that
because these fields are variably sized, some payload fields may not
be conveniently aligned on an even octet.
Note 2: The actual DER for the OID Specific Payload field is defined
in [IEC-62351-6].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! ID Type=13 ! DOI-Specific ID Data = 0 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Len=13 ! OID=<06 0B 2A 86 48 CE 56 83 E3 1A 08 01 02> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Specific Payload Len ! OID SP=<DER for 233.252.0.1> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 7: Sample Identification Payload
The Key Server responds with the following SA TEK payload including
two GDOI_PROTO_IEC_61850 Protocol-Specific TEK payloads in the second
GROUPKEY-PULL message. The first one is to be activated immediately,
and has a lifetime of 3600 seconds (0x0E10) remaining. The second
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has a lifetime of 12 hours (0xA8C0) and should be activated in 3300
seconds (0x0CE4), which givens a 5 minute (300 seconds) overlap of
the two SAs.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! DOI = 2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Situation = 0 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SA Attr NP=16 (SA TEK) ! RESERVED2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! NP=16 (SA TEK)! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Prot-ID=TBD1 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Len=13 ! OID=<06 0B 2A 86 48 CE 56 83 E3 1A 08 01 02> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Specific Payload Len !OID SP=<DER for 233.252.0.1> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI=1 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! AuthAlg=1 (HMAC-SHA256-128) ! EncAlg=2 (AES-CBC-128) !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Remaining Lifetime=0x0E01 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SA Attr NP=16 (SA TEK) ! RESERVED2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! NP=0 ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Prot-ID=TBD1 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Len=13 ! OID=<06 0B 2A 86 48 CE 56 83 E3 1A 08 01 02> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! OID Specific Payload Len !OID SP=<DER for 233.252.0.1> ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI=2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! AuthAlg=0 (NONE) ! EncAlg=4 (AES-GCM-128) !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Remaining Lifetime=0xA8C0 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Type=1 (SA_ATD) ! Length=4 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Value=0x0CE4 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 8: Sample IEC-61850 SA Payload
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The IED acknowledges that it is capable and willing to use this
policy in the third GROUPKEY-PULL message. In response the KS sends
a KD payload to the requesting IED. This concludes the GROUPKEY-PULL
exchange.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Next Payload ! RESERVED ! Payload Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! Number of Key Packets=2 ! RESERVED2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! KD Type=1 ! RESERVED ! Key Packet Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI Size=4 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI=1 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! TYPE=TEK_INTEGRITY_KEY (2) ! LENGTH=32 (256-bit key) !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! !
! !
! !
! HMAC-SHA256 Key !
! !
! !
! !
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! TYPE=TEK_ALGORITHM_KEY (1) ! LENGTH=16 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! !
! AES-CBC-128 Key !
! !
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! KD Type=1 ! RESERVED ! Key Packet Length !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI Size=4 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! SPI=2 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! TYPE=TEK_ALGORITHM_KEY (1) ! LENGTH=20 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
! !
! AES-GCM-128 Key & Salt !
! !
! !
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
Figure 9: Sample KD Payload
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Appendix B. Implementation Considerations
Several topics have been suggested as useful for implementors.
B.1. DER Length Fields
The ID and SA TEK payloads defined in this memo include explicit
lengths for fields formatted as DER. This includes the OID Length
and OID Specific Payload Length fields shown in Figure 2 and
Figure 4. Strictly speaking, these lengths are redundant since the
length of the DER value is also encoded within the DER fields. It
would be possible to determine the lengths of the fields from those
encoded values. However, many implementations will find the explicit
length fields convenient when constructing and sanity checking the
GDOI messages including these payloads. Implementations will thus be
spared from manipulating the DER itself when performing activities
that do not otherwise require parsing in order to obtain values
therein.
B.2. Groups with Multiple Senders
GCKS policy may specify more than one protected type of IEC 61850
message within a GDOI group. This is represented within a GDOI SA
Payload by the presence of an SA TEK Payload for each multicast group
that is protected as part of group policy. The OID contained in each
of the SA TEK Payloads may be identical, but the value of each OID
Specific Payload would be unique. Typically, the OID Specific
Payload defines a destination address, and typically there is a
single sender to that destination address.
Appendix C. Data Attribute Format
Data attributes attached to an SA TEK following the Data Attribute
format described in this section. Data attributes can be in Type/
Value (TV) format (useful when a value is defined to be less than two
octets in size) or in Type/Length/Value (TLV) form.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
!A! Attribute Type ! AF=0 Attribute Length !
!F! ! AF=1 Attribute Value !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AF=0 Attribute Value .
. AF=1 Not Transmitted .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Data Attributes
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The Data Attributes fields are defined as follows:
o Attribute Type (2 octets) - Unique identifier for each type of
attribute. These attributes are defined as part of the DOI-
specific information. The most significant bit, or Attribute
Format (AF), indicates whether the data attributes follow the
Type/Length/Value (TLV) format or a shortened Type/Value (TV)
format. If the AF bit is a zero (0), then the Data Attributes are
of the Type/Length/Value (TLV) form. If the AF bit is a one (1),
then the Data Attributes are of the Type/Value form.
o Attribute Length (2 octets) - Length in octets of the Attribute
Value. When the AF bit is a one (1), the Attribute Value is only
2 octets and the Attribute Length field is not present.
o Attribute Value (variable length) - Value of the attribute
associated with the DOI-specific Attribute Type. If the AF bit is
a zero (0), this field has a variable length defined by the
Attribute Length field. If the AF bit is a one (1), the Attribute
Value has a length of 2 octets.
Authors' Addresses
Brian Weis
Cisco Systems
170 W. Tasman Drive
San Jose, California 95134-1706
USA
Phone: +1 408 526 4796
Email: bew@cisco.com
Maik Seewald
Cisco Systems
Am Soeldnermoos 17
D-85399 Hallbergmoos
Germany
Phone: +49 619 6773 9655
Email: maseewal@cisco.com
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Herb Falk
SISCO
6605 19-1/2 Mile Road
Sterling Heights, MI 48314
USA
Phone: +1 586 254 0020 x105
Email: herb@sisconet.com
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