One document matched: draft-wei-karp-analysis-rp-sa-00.txt
Network Working Group Y. Wei, Ed.
Internet-Draft H. Wang
Expires: January 6, 2011 X. Liang
ZTE Corporation
July 5, 2010
Analysis of Security Association for Current Routing Protocol
draft-wei-karp-analysis-rp-sa-00
Abstract
This document analyzes the security associations used by current
routing protocols, including RIPv2, OSPFv2, ISIS, BFD, and BGP. It
also discusses the possible methods for the diversity issue of
routing protocol security association (SA).
Status of this Memo
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This Internet-Draft will expire on January 6, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Analysis of security associations for current routing
protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Summary for security associations of current routing
protocol . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Analysis of security associations of current routing
protocol . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Discussion of generic security association . . . . . . . . 8
3. security considerations . . . . . . . . . . . . . . . . . . . 9
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10
5. appendix: Existing SA definition . . . . . . . . . . . . . . . 11
5.1. RIPv2 SA . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. OSPFv2 SA . . . . . . . . . . . . . . . . . . . . . . . . 11
5.3. ISIS SA . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.4. BFD SA . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.5. TCP-AO . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
The karp (Keying and Authentication for Routing Protocols) working
group aims to secure the packets on the wire of the routing protocol
exchanges. This work has been divided into two phases, (1) Enhance
the routing protocol's current authentication mechanism; (2) Develop
an automated keying framework [ietf-karp-design-guide]. Currently,
there are a variety of routing protocols. Many routing protocols (or
groups of protocols) have already defined security association (SA)
for cryptographic message authentication and integrity protection,
which are listed in the appendix. SA is the basis for protecting the
packet of routing protocol; it may also affect the design of key
management protocol (KMP) and framework of the karp. As a start, it
is desirable to analyze existing security associations of routing
protocols.
The main idea of this document is as follows:
(1) Briefly overview of existing SA of routing protocols.
(2) Compare those typical fields in routing protocol SA one by one,
and identify potential issues.
(3) Discuss the possible methods for that problem.
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2. Analysis of security associations for current routing protocols
This section considers the security associations of the following
routing protocols: RIPv2, OSPFv2, ISIS, BFD, and BGP.
Note: Maybe there are lacks of commonly accepted term - BGP SA. This
document regards Master Key Tuple (MKT) in TCP-AO
[ietf-tcpm-tcp-auth-opt] as BGP SA.
2.1. Summary for security associations of current routing protocol
The security associations of current routing protocol are summarized
as follows:
-The RIPv2 SA [RFC4822] includes the following information: key
identifier, cryptographic algorithms, key length, sequence number,
and life time of SA.
-The OSPFv2 SA [RFC5709] includes the following information: key
identifier, cryptographic algorithms, key length, and life time of
SA.
-The ISIS SA [RFC5310] includes the following information: key
identifier, cryptographic algorithms, key length.
-The BFD SA [draft-bhatia-bfd-crypto-auth] includes the following
information: key identifier, cryptographic algorithms, key
identifier.
-The BGP SA [ietf-tcpm-tcp-auth-opt] includes the following
information: key identifier, cryptographic algorithms, master key,
key derivation function (KDF), sequence number, etc.
The details of these SAs are listed in the appendix.
2.2. Analysis of security associations of current routing protocol
The fields in the above security associations are analyzed as
follows:
- Key identifier: Key identifier (Key ID) is used to uniquely
identify a SA. All SAs used in routing protocols specify this field.
For example, OSPFv2 SA defines Key Identifier field to identify an
OSPF SA.
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+--------------/-----------------/------------------+
| SA of Routing| Name of Key ID | Length of Key ID |
| Protocol | | |
---------------|-----------------|-------------------
| RIPv2 | Key Identifier | 8 bits |
---------------|-----------------|-------------------
| OSPFv2 | Key Identifier | 8 bits |
---------------|-----------------|-------------------
| ISIS | Key Identifier | 2 octets |
---------------|-----------------|-------------------
| BFD | Authentication | 2 octets |
| | Key Identifier | |
---------------|-----------------|-------------------
| BGP | KeyID | 8 bits |
+--------------\-----------------\------------------+
The key identifier maybe manually be configured or generated by
automated key management protocol (KMP) which is one ongoing work in
karp. One obvious distinction among these routing protocols' SA is
that the length of key ID is different. If KMP generates key ID
according to specific routing protocol, the design of KMP will be
complex and bound to underlying routing protocol.
- Cryptographic algorithms and key: For the purpose of authentication
and integrity protection, the algorithm and key are used to produce
message authentication code (MAC), which is used to protect the
packet on the wire. Typically, key length is related to a specific
algorithm.
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+----------------/-------------------/-----------------------------+
| SA of Routing | Algorithms | Key Length |
| Protocol | | |
-----------------|-------------------|------------------------------
| RIPv2 | KEYED-MD5, | The length is variable |
| | HMAC-SHA-1, | and dependent on algorithm |
| | HMAC-SHA-256, | |
| | HMAC-SHA-384, | |
| | HMAC-SHA-512. | |
-----------------|-------------------|------------------------------
| OSPFv2 | Keyed-MD5, | Same as above |
| | HMAC-SHA-1, | |
| | HMAC-SHA-256, | |
| | HMAC-SHA-384, | |
| | HMAC-SHA-512 | |
-----------------|-------------------|------------------------------
| ISIS | HMAC-SHA-1, | Same as above |
| | HMAC-SHA-224, | |
| | HMAC-SHA-256, | |
| | HMAC-SHA-384, | |
| | HMAC-SHA-512 | |
-----------------|-------------------|------------------------------
| BFD | Keyed MD5, | Same as above |
| | Keyed SHA-1, | |
| | HMAC-SHA-1, | |
| | HMAC-SHA-256, | |
| | HMAC-SHA-384 | |
| | HMAC-SHA-512 | |
-----------------|-------------------|------------------------------
| BGP | Keyed MD5 | Same as above |
| | HMAC-SHA-1-96 | |
| | AES-128-CMAC-96 | |
+----------------\-------------------\-----------------------------+
The cryptographic algorithms used in routing protocol are almost the
same except for the protection of BGP, which is based on TCP-AO.
This case also shows that manual configuration or KMP are also
required to differentiate underlying routing protocol, which makes
them complex.
- Lifetime: It specifies whether the SA is valid or not. For
example, OSPFv2 SA [RFC5709] uses four fields (Key Start Accept, Key
Start Generate, Key Stop Generate, Key Stop Accept) to control the
lifetime of the SA.
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+---------------/--------------------+
| SA of Routing | Fields |
| Protocol | |
----------------|---------------------
| RIPv2 | Start Time |
| | Stop Time |
----------------|---------------------
| OSPFv2 | Key Start Accept |
| | Key Start Generate |
| | Key Stop Generate |
| | Key Stop Accept |
----------------|---------------------
| ISIS | None |
----------------|---------------------
| BFD | None |
+---------------\--------------------+
It can be seen that some routing protocols' SA define lifetime,
others do not. This implies that underlying routing protocol does
not exhibit unified interface to upper layer. In some cases, a
rekeying mechanism is used to trigger the lifetime of SA. However,
current routing protocol SA does not specify what to do when the key
expires.
-Sequence number: Sequence number is typically defined to avoid
replay attacks.
+---------------/---------------------+
| SA of Routing | Length of Sequence |
| Protocol | number |
---------------------------------------
| RIPv2 | 32bits |
---------------------------------------
| OSPFv2 | 32bits |
---------------------------------------
| ISIS | 32bits |
---------------------------------------
| BFD | 32bits |
---------------------------------------
| BGP | 32bits |
+---------------\---------------------+
The length of sequence number above is 32 bits, which is convenient
to the manual configuration or KMP because it is unrelated to
underlying routing protocol.
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2.3. Discussion of generic security association
As shown in section 2.2, the definition and its value of SA is
different for each routing protocol. This document just covers part
of routing protocol. Some other routing protocols such as OSPFv3,
RIPng depends on the protection of IPsec SA [RFC4301]. If this case
is taken into consideration, the differences among these SAs are more
bigger. It is required to consider the diversity of routing protocol
SA when starting the karp's work. Here are two possible ways to deal
with this issue.
(1) Each routing protocol (or category) has its own specific manual
configuration or KMP. The advantage is that it can be implemented
easily and straightforwardly. The disadvantage is obvious: The
system is complex and cumbersome because there exist a dozen of
routing protocols. In this case, the karp's work seems complicated.
(2)A generic SA (gSA) is introduced to hide the diversity of
underlying routing protocol SA. It can be regarded as abstract
layer; it is a bridge between manual configuration or KMP protocol
and routing protocol. The advantages are as follows: (1)It provides
a unified interface to manual configuration or KMP protocol. (2)It
decouples KMP with underlying routing protocol, which addresses the
requirement identified in [I-D.ietf-karp-threats-req]. (3)KMP and
routing protocol can be evolved independently. (4)The complexity of
the design of KMP is greatly reduced. The disadvantage of this
method may be that a new layer is added, which produces extra cost.
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3. security considerations
To be completed.
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4. IANA considerations
To be completed.
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5. appendix: Existing SA definition
This section is for information. It can be safely removed in the
future.
5.1. RIPv2 SA
RIPv2 Security Association:[RFC4822]
KEY-IDENTIFIER (KEY-ID) - The unsigned 8-bit KEY-ID value is used to
identify the RIPv2 Security Association in use for this packet.
AUTHENTICATION ALGORITHM - This specifies the cryptographic algorithm
and algorithm mode used with the RIPv2 Security Association.
AUTHENTICATION KEY - This is the value of the cryptographic
authentication key used with the associated Authentication Algorithm.
SEQUENCE NUMBER - This is an unsigned 32-bit number.
START TIME - This is a local representation of the day and time that
this Security Association first becomes valid.
STOP TIME - This is a local representation of the day and time that
this Security Association becomes invalid
5.2. OSPFv2 SA
OSPFv2 Security Association: [RFC5709]
Key Identifier (KeyID) - This is an 8-bit unsigned value used to
uniquely identify an OSPFv2 SA and is configured either by the router
administrator (or, in the future, possibly by some key management
protocol specified by the IETF). The receiver uses this to locate
the appropriate OSPFv2 SA to use. The sender puts this KeyID value
in the OSPF packet based on the active OSPF configuration.
Authentication Algorithm - This indicates the authentication
algorithm (and also the cryptographic mode, such as HMAC) to be used.
This information SHOULD never be sent over the wire in cleartext
form. At present, valid values are Keyed-MD5, HMAC-SHA-1, HMAC-SHA-
256, HMAC-SHA-384, and HMAC-SHA-512.
Authentication Key - This is the cryptographic key used for
cryptographic authentication with this OSPFv2 SA.
Key Start Accept - The time that this OSPF router will accept packets
that have been created with this OSPF Security Association.
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Key Start Generate - The time that this OSPF router will begin using
this OSPF Security Association for OSPF packet generation.
Key Stop Generate - The time that this OSPF router will stop using
this OSPF Security Association for OSPF packet generation.
Key Stop Accept - The time that this OSPF router will stop accepting
packets generated with this OSPF Security Association.
5.3. ISIS SA
An IS-IS Security Association contains a set of parameters shared
between any two legitimate IS-IS speakers. Parameters associated
with an IS-IS SA: [RFC5310]
Key Identifier (Key ID) - This is a two-octet unsigned integer used
to uniquely identify an IS-IS SA, as manually configured by the
network operator. The receiver determines the active SA by looking
at the Key ID field in the incoming PDU. The sender, based on the
active configuration, selects the Security Association to use and
puts the correct Key ID value associated with the Security
Association in the IS-IS PDU. If multiple valid and active IS-IS
Security Associations exist for a given outbound interface at the
time an IS-IS PDU is sent, the sender may use any of those Security
Associations to protect the packet.
Authentication Algorithm - This signifies the authentication
algorithm to be used with the IS-IS SA. At present, the following
values are possible: HMAC-SHA-1, HMAC-SHA-224, HMAC-SHA-256, HMAC-
SHA-384, and HMAC-SHA-512.
Authentication Key - This value denotes the cryptographic
authentication key associated with the IS-IS SA. The length of this
key is variable and depends upon the authentication algorithm
specified by the IS-IS SA.
5.4. BFD SA
The BFD protocol does not include an in-band mechanism to create or
manage BFD Security Associations (BFD SA). A BFD SA contains a set
of shared parameters between any two legitimate BFD routers.
Parameters associated with a BFD SA: [draft-bhatia-bfd-crypto-auth]
Authentication Key Identifier (Key ID) - This is a two octet unsigned
integer used to uniquely identify the BFD SA, as manually configured
by the network operator (or, in the future, possibly by some key
management protocol specified by the IETF). The receiver determines
the active SA by looking at this field in the incoming packet. The
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sender puts this Key ID in the BFD packet based on the active
configuration.
Authentication Algorithm - This indicates the authentication
algorithm to be used with the BFD SA. The following values are
possible: Keyed MD5, Keyed SHA-1, HMAC-SHA-1, HMAC-SHA-256, HMAC-SHA-
384 and HMAC-SHA-512.
Authentication Key - This indicates the cryptographic key associated
with this BFD SA. The length of this key is variable and depends
upon the authentication algorithm specified by the BFD SA.
5.5. TCP-AO
A Master Key Tuple (MKT) describes TCP-AO properties to be associated
with one or more connections. It is composed of the following:
[ietf-tcpm-tcp-auth-opt]
IDs - The values used in the KeyID or RNextKeyID of a TCP-AO option;
used to differentiate MKTs in concurrent use (KeyID), as well as to
indicate when MKTs are ready for use in the opposite direction
(RNextKeyID). Each MKT has two IDs - a SendID and a RecvID. The
SendID is inserted as the KeyID of the TCP-OP option of outgoing
segments, and the RecvID is matched against the KeyID of the TCP-AO
option of incoming segments. MKT IDs MUST support any value, 0-255
inclusive. There are no reserved ID values.
Master key - A byte sequence used for generating traffic keys, this
may be derived from a separate shared key by an external protocol
over a separate channel.
Implementations are advised to keep master key values in a private,
protected area of memory or other storage.
Key Derivation Function (KDF) - Indicates the key derivation function
and its parameters, as used to generate traffic keys from master
keys.
Message Authentication Code (MAC) algorithm - Indicates the MAC
algorithm and its parameters as used for this connection.
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6. References
[ietf-karp-design-guide]
Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", February
2010.
[ietf-karp-threats-req]
Lebovitz, G., "KARP Threats and Requirements", February
2010.
[ietf-tcpm-tcp-auth-opt]
Touch, J., Mankin, A., and R. Al., "The TCP Authentication
Option", January 2010.
[draft-bhatia-bfd-crypto-auth]
Bhatia, M. and V. Manral, "Generic Cryptographic
Authentication", June 2010.
[RFC4822] Atkinson, R. and M. Fanto, "RIPv2 Cryptographic
Authentication", February 2007.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", December 2005.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", February 2009.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Li, T., and
R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", October 2009.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", June 2006.
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", August 1998.
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Authors' Addresses
Yinxing Wei (editor)
ZTE Corporation
No. 68, Zijinghua Road, Yuhuatai District
Nanjing, Jiangsu 210012
China
Phone: +86 25 52877993
Email: wei.yinxing@zte.com.cn
Hongyan Wang
ZTE Corporation
No. 68, Zijinghua Road, Yuhuatai District
Nanjing, Jiangsu 210012
China
Phone: +86 25 52877993
Email: wang.hongyan4@zte.com.cn
Xiaoping
ZTE Corporation
No. 68, Zijinghua Road, Yuhuatai District
Nanjing, Jiangsu 210012
China
Phone: +86 25 52877993
Email: liang.xiaoping@zte.com.cn
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