Network Working Group M. Jethanandani
Internet-Draft B. Weis
Intended status: Standards Track K. Patel
Expires: January 2, 2012 Cisco Systems
July 1, 2011
Key Management for Pairwise Routing Protocol
draft-mahesh-karp-kmprp-00
Abstract
This document defines an automated method of Key Management for
routing protocol that need pair-wise keys.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 2, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Exchanges . . . . . . . . . . . . . . . . . . . . . . 3
2.1. RP_INIT . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. RP_AUTH . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. RP_ADD . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. INFORMATIONAL . . . . . . . . . . . . . . . . . . . . . . 5
3. Header and Payload Formats . . . . . . . . . . . . . . . . . . 5
3.1. Security Association Payload . . . . . . . . . . . . . . . 6
3.1.1. Proposal Substructure . . . . . . . . . . . . . . . . 6
3.1.1.1. Transforms Substructures . . . . . . . . . . . . . 8
3.1.1.1.1. KMPRP . . . . . . . . . . . . . . . . . . . . 8
3.1.1.1.2. TCP-AO Transforms . . . . . . . . . . . . . . 8
4. Operation Details . . . . . . . . . . . . . . . . . . . . . . 10
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Initial Key Specific Data Exchange . . . . . . . . . . . . 11
4.3. Key Specific Data Rollover Exchange . . . . . . . . . . . 11
5. Key Management Database (KMDB) . . . . . . . . . . . . . . . . 11
6. Protocol Interaction . . . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
Key management today is limited to statically configuring master keys
in individual routers. This document extends currently defined IKEv2
protocol to define an automated method of Key Management for Pairwise
Routing Protocol (KMPRP) that allows network devices to automatically
exchange key material related information between the network
devices.
2. Protocol Exchanges
The exchange of private keying material between two network devices
using a dedicated key management protocol is a requirement as
articulated in [I-D.ietf-karp-routing-tcp-analysis]. There is no
need to define an entirely new protocol for this purpose, when
existing mature protocol exchanges and methods have been vetted.
This draft makes use of the IKEv2 protocol exchanges, state machine,
and policy definitions to define a dedicated key management protocol.
However, as IKEv2 was developed exclusively for the use of IPsec,
these protocol exchanges are incorporated by reference into the
present key protocol definitions, and are exchanged using a dedicated
UDP port number (TDB - IANA). The use of a dedicated UDP port will
clearly differentiate this protocol from IKEv2.
In the following figures, the notations contained in the message are
defined as follows.
+----------+------------------------------+
| Notation | Payload |
+----------+------------------------------+
| AUTH | Authentication |
| CERT | Certificate |
| CERTREQ | Certificate Request |
| D | Delete |
| HDR | KMPRP Header (not a payload) |
| IDi | Identification - Initiator |
| IDr | Identification - Responder |
| KE | Key Exchange |
| Ni, Nr | Nonce |
| N | Notify |
| SA | Security Association |
| SK | Encrypted and Authenticated |
| TSi | Traffic Selector - Initiator |
| TSr | Traffic Selector - Responder |
+----------+------------------------------+
Acronyms Used in Protocol Exchange
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2.1. RP_INIT
The RP Initial Exchange (RP_INIT) is identical to the IKE_SA_INIT
exchange defined in Internet Key Exchange Protocol Version 2
[RFC5996]. The RP_INIT exchange is a two-message exchange that
allows the network devices to negotiate cryptographic algorithms,
exchange nonces, and do a Diffe-Hellman (DH) [DH] exchange, for their
routing protocols, after which protocols on these network devices can
communicate privately. Note that at this point the network devices
have not identified their peer. For the details of this exchange,
refer to IKE_SA_INIT in Internet Key Exchange Protocol Version 2
[RFC5996].
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SAi1, KEi, Ni -->
<-- HDR, SAr1, KEr, Nr, [CERTREQ,]
RP_INIT
2.2. RP_AUTH
Next, the network devices perform a RP Authentication exchange
(RP_AUTH), which is substantially the same as the IKE_AUTH exchange
defined in RFC 5996, except that the SA payload contains policy
specific to the routing protocol security policy (labeled SArpi and
SArpr) rather than IPsec policy (SAi2, SAr2 defined in RFC 5996).
The SArpi and SArpr payloads are described in Section 3; for the
details of the rest of the exchange please refer to IKE_AUTH in RFC
5996.
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SK {IDi, [CERT,] [CERTREQ,]
[IDr,] AUTH, SArpi,
TSi, TSr} -->
<-- HDR, SK {IDr, [CERT,] AUTH,
SArpr, TSi, TSr}
RP_AUTH
In the RP_AUTH exchange, the Initiator proposes one or more sets of
policies for one routing protocol in the SArpi. The Responder
returns the one policy contained in SArpi that it accepts. Based on
this policy, appropriate keying material is derived from the existing
shared keying material. At the successful conclusion of the RP_AUTH
exchange, the initiator and responder have agreed upon a single set
of policy and keying material for a particular routing protocol.
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2.3. RP_ADD
The network devices may then destroy the state associated with the RP
SA, continuing to use the RP policy and keying material, or they may
choose to retain them for the further use. If both the network
devices choose to retain them, they may use the RP SA to subsequently
agree upon replacement policy for the same RP, or agree upon policy
and keying material for another routing protocol. Either case will
require the use of the RP Additional Exchange (RP_ADD), similar to
the IKEv2 CREATE_CHILD_SA exchange as defined in RFC 5996.
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SK {SArpi, Ni, [KEi ],
TSi, TSr} -->
<-- HDR, SK {SArpr, Nr, [KEr ],
TSi, TSr}
RP_ADD
In the RP_ADD exchange, the SA payloads in the RP_ADD exchange are
used identically as in the RP_AUTH exchange. For details on the rest
of the exchange, refer to the CREATE_CHILD_SA exchange as defined in
RFC 5996.
2.4. INFORMATIONAL
The IKEv2 INFORMATIONAL exchange is also useful for deleting specific
RP SAs or sending status information. The Notify (N) and Delete (D)
payloads are as those defined by IKEv2 [IKEV2-PARAMS]. For example,
if the Responder refused to accept one of Proposals sent by the
Initiator, it would return an INFORMATIONAL exchange of type
NO_PROPOSAL_CHOSEN instead of the response to RP_ADD.
Peer (Initiator) Peer (Responder)
------------------- ------------------
HDR, SK {[N,] [D,] ... } -->
<-- HDR, SK {[N,] [D,] ... }
INFORMATIONAL
3. Header and Payload Formats
The protocol defined in this memo uses a HDR identical to the Generic
Payload Header defined in section 3.2 of RFC 5996. The new exchanges
defined in this memo are not used with IKEv2. A new IANA registry is
to be created to identify the RP exchange types and payloads
described in this section.
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3.1. Security Association Payload
The Security Association (SA) payload contains a list of Proposals,
which describe one or more sets of policy that a router is willing to
use to protect a routing protocol. It is identical to the SA payload
described in RFC 5996, and the details of the fields are described
there.
In the Initiator's message, the SArpi payload contains a list of
Proposal payloads (as defined in the next section), each of which
contains a single set of policy that can be applied to the packets
described in the Traffic Selector (TS) payloads in the same exchange.
For example, the TS payloads may describe a set of IP addresses and
ports which are a BGP connection, and the SA payload contains a list
of proposals describing what policy the router is willing to use to
protect that BGP traffic. Each set of policy is given a particular
"Proposal Number" uniquely identifying this set of policy.
The responder includes a single Proposal payload in it's SA policy,
which denotes the choice it has made amongst the initiator's list of
Proposals. Any attributes of a selected transform MUST be returned
unmodified as explained in IKEv2 [RFC5996] section 3.3.6. The
initiator of an exchange MUST check that the accepted offer is
consistent with one of its proposals, and if not MUST terminate the
exchange.
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 |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Proposals> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Security Association Payload
The Security Association Payload fields are defined as in RFC 5996.
3.1.1. Proposal Substructure
The Proposal (P) substructure of the Security Association Payload
contains an identification for the set of policy choices, the
security protocol offered in the proposal, and details of the
cryptographic choices offered.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 (last) or 2 | Reserved | Proposal Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Proposal Num | Protocol ID | RT Protocol|Num Transforms |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Transforms> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Proposal Payload
o 0 (last) or 2 (more) (1 octet) - Specifies whether this is the last
Proposal Substructure in the SA.
o RESERVED (1 octet) - MUST be sent as zero; MUST be ignored on
receipt.
o Proposal Length (2 octets, unsigned integer) - Length of this
proposal, including all transforms and attributes that follow.
o Proposal Num (1 octet) - When a proposal is made, the first
proposal in an SA payload MUST be 1, and subsequent proposals MUST be
one more than the previous proposal (indicating an OR of the two
proposals). When a proposal is accepted, the proposal number in the
SA payload MUST match the number on the proposal sent that was
accepted.
o Protocol ID (1 octet) - Specifies the protocol identifier for the
current negotiation.
Protocol Protocol ID Reference
----------------------------------------------
KMPRP 1
TCP-AO 2 RFC 5925
LDP Discovery Key 3 TBD
Standards Action 4-128
Private Use 129-255
Protocol ID
o RT Protocol (1 octet) - Specifies the routing protocol identifier
for the current negotiation.
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Routing (RT) Protocol Protocol ID Reference
---------------------------------------------
BGP 1 RFC 4271
LDP 2 RFC 5036
MSDP 3 RFC 3618
PIM PORT 4
PCEP 5 RFC 5440
Routing Protocol
o Num Transforms (1 octet) - Specifies the number of transforms in
this proposal.
o Transforms (variable) - One or more transform substructures.
3.1.1.1. Transforms Substructures
Each Proposal has a list of Transform (T) substructures, each of
which describe a particular set of cryptographic policy choices.
This is useful for an initiator to propose multiple cryptographic
choices for the same policy described in its associated Proposal
payload.
3.1.1.1.1. KMPRP
This transform payload is used negotiate policy to protect the KMPRP
exchanges. The Transforms are identical to the Transforms specified
to negotiate IKE policy in Section 3.3.2 of IKEv2 [RFC5996].
3.1.1.1.2. TCP-AO Transforms
The TCP-AO [RFC5925] transform payload contains the following fields.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 (last) or 3 | RESERVED | Transform Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SendID |Auth Alg | KDF | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TCP-AO Transforms
o 0 (last) or 3 (more) (1 octet) - Specifies whether this is the last
Transform Substructure in the Proposal.
o RESERVED (1 octet) - MUST be sent as zero; MUST be ignored on
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receipt.
o Transform Length (2 octets) - The length (in octets) of the
Transform Substructure including Header and Attributes.
o SendID (1 octet) - The TCP-AO KeyID that the sender will use to
represent this Transform. The KeyID will be used to generate the
keys independently on each network device at the end of the exchange.
o Auth Alg (1 octet) - The Authentication algorithm defined as a part
of this Transform. Values are defined in Cryptographic Algorithms
for the TCP Authentication Option [RFC5926].
Auth Alg ID
------------------------------
HMAC-SHA-1-96 1
AES-128-CMAC-96 2
Standards Action 3-128
Private Use 129-255
Authentication Algorithm
o KDF (1 octet) - The KDF defined as a part of this Transform.
Values are defined in Cryptographic Algorithms for the TCP
Authentication Option [RFC5926].
KDF ID
------------------------------
KDF_HMAC_SHA1 1
KDF_AES_128_CMAC 2
Standards Action 3-128
Private Use 129-255
Key Derivation Functions
o Flags (1 octet) - Indicates specific options for TCP-AO. The bits
are as follows:
+-+-+-+-+-+-+-+-+
|O|X|X|X|X|X|X|X|
+-+-+-+-+-+-+-+-+
In the description below, a bit being 'set' means its value is '1',
while 'cleared' means its value is '0'. 'X' bits MUST be cleared
when sending and MUST be ignored on receipt.
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o O (Options) - This bit indicates whether or not TCP Options are to
be included in the bytes protected by the authentication
calculation. This bit is set to indicate that TCP Options are to
be ignored and cleared to indicate that TCP Options are protected.
When a TCP-AO transform is chosen, keying material for the TCP-AO
master key is generated as follows, where Ni and Nr are unique to
this exchange. The value SK_D is defined in RFC 5996, and refers to
the value derived from SKEYSEED that is used to derive new keys
(e.g., for TCP-AO).
<TCP-AO master key> = prf+(SK_d, Ni | Nr)
4. Operation Details
4.1. General
KMPRP is used to dynamically derive key material information between
the two network devices trying to establish or maintain a routing
protocol neighbor adjacency. Typically network devices running the
routing protocols establish neighbor adjacencies at the routing
protocol level. These routing protocols may run different security
algorithms that provide transport level security for the protocol
neighbor adjacencies. Depending on the security algorithm used, the
routing protocols are configured with security algorithm specific
keys that are either long term keys or short term session keys.
These keys are specific to the security algorithms used to enforce
transport level security for the routing protocols.
A routing protocol causes KMPRP to execute when it needs key material
to establish neighbor adjacency. This can be as a result of the
routing protocol neighbor being configured, neighbor changed or
updated, a local rekey policy decision, or some other event dictated
by the implementation. The key material would allow the network
devices to then independently generate the same key and establish a
KMPRP neighbor adjacency between them. This is typically done by the
Initiator (KMPRP speaker) initiating a KMPRP RP_INIT exchange
mentioned in the section 2.1 towards its KMPRP peer. As part of
RP_INIT exchange, KMPRP will send a message to the KMPRP peer's well
known KMPRP UDP port [TBD] by IANA. The format of the message is
explained in section 3. The procedure to exchange key information is
explained in section 3. Once the key material information is
successfully exchanged by both the KMPRP speaker, the KMPRP neighbor
adjacency may be torn down.
The master key data received from KMPRP peers are stored in the
separate Key Management Database known as KMDB. KMDB follows the
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guidelines in[I-D.ietf-karp-crypto-key-table], and each entry
consists of Key specific information, Security algorithm to which the
Key is applicable to, Routing Protocol Clients of interest, and the
announcing KMPRP Peer. KMDB is also used to notify the routing
protocols about the key updates. Typically key material information
is exchanged whenever a routing protocol is about to create a new
neighbor adjacency. This is considered as an Initial Key exchange
mode. Key material information is also exchanged to refresh existing
key data on an already existing neighbor adjacency. This is
considered as Key rollover exchange mode. The following sections
describes their detail behavior.
4.2. Initial Key Specific Data Exchange
Routing protocols informs KMPRP of its new neighbor adjacency. It
does so by creating a local entry in KMDB which consists of a
Security algorithm, Key specific information, routing protocol client
and the routing protocol neighbor. Upon a successful creation of
such an entry KMPRP initiates KMPRP peering with the neighbor and
starts initial KMPRP RP_INIT exchange explained in section 2.1
followed by the RP_AUTH exchanged explained in section 2.2. Once the
key related information is successfully exchanged, KMDB may invoke
the routing protocol client to provide key specific information
updates if any.
4.3. Key Specific Data Rollover Exchange
Key rollover exchange may be initiated at a pre-configured time
interval or as part of a manual configuration and is outside the
scope of this document. The procedure of Key Rollover exchange is
exactly same as the Initial Key specific data exchange described
above.
5. Key Management Database (KMDB)
Protocol interaction between KMPRP and its client routing protocols
is typically done using KMDB. Routing protocols update KMDB by
installing a new Key related information or purging an existing Key
specific information. As part of the KMDB update, KMPRP initiates
peering connections with its appropriate KMPRP peers to announce the
updated key related information. KMPRP may also receive an updated
key related information from its peers which gets installed in KMDB.
Whenever KMPRP updates KMDB with updated key information from its
peers, it notifies client routing protocols of its updates.
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6. Protocol Interaction
Routing protocols could end up with multiple keys when updated by
KMDB. Typically, routing protocols should use the keys till the
point its peers have transitioned to a new key. Once the peers have
transitioned to a new key, routing protocols could put the old keys
on timers and eventually free them. The reason to put them on timer
and not free them right away is to ensure that all out of order
packets in TCP are handled correctly.
7. IANA Considerations
A new UDP port number will need to be assigned for systems that want
to implement this protocol.
A new IANA registry is to be created to identify the RP exchange
types and payloads.
Note to RFC Editor: this section may be removed on publication as an
RFC.
8. Security Considerations
TBD
9. Acknowledgements
During the development of TCP-AO, Gregory Lebovitz noted that a
protocol based on an IKEv2 exchange would be a good automated key
management method for deriving a TCP-AO master key.
Many protocol definitions and protocol formats come from RFC 5996,
either by reference or inclusion.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
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[RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
for the TCP Authentication Option (TCP-AO)", RFC 5926,
June 2010.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010.
10.2. Informative References
[DH] Diffie, W. and M. Hellman, "New Directions in
Cryptography", IEEE Transactions on Information
Theory, V.IT-22 n. 6, June 1977.
[I-D.ietf-karp-crypto-key-table]
Housley, R. and T. Polk, "Database of Long-Lived Symmetric
Cryptographic Keys", draft-ietf-karp-crypto-key-table-01
(work in progress), May 2011.
[I-D.ietf-karp-routing-tcp-analysis]
Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Security According to KARP Design
Guide", draft-ietf-karp-routing-tcp-analysis-00 (work in
progress), June 2011.
[IKEV2-PARAMS]
"Internet Key Exchange Version 2 (IKEv2) Parameters", <htt
p://www.iana.org/assignments/ikev2-parameters/
ikev2-parameters.xml>.
Authors' Addresses
Mahesh Jethanandani
Cisco Systems
170 Tasman Drive
San Jose, California CA
USA
Phone: +1 (408) 527-8230
Fax:
Email: mjethanandani@gmail.com
URI:
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Brian Weis
Cisco Systems
170 W. Tasman Drive
San Jose, California 95134
USA
Phone: +1 (408) 526-4796
Fax:
Email: bew@cisco.com
URI:
Keyur Patel
Cisco Systems
170 Tasman Drive
San Jose, California 95134
USA
Phone: _1 (408) 526-7183
Fax:
Email: keyupate@cisco.com
URI:
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