One document matched: draft-ietf-pana-ipsec-01.txt
Differences from draft-ietf-pana-ipsec-00.txt
PANA Working Group
Internet Draft M. Parthasarathy
Document: draft-ietf-pana-ipsec-01.txt Nokia
Expires: June 2004 January 2004
PANA enabling IPsec based Access Control
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [i].
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The PANA (Protocol for carrying Authentication for Network Access)
working group is developing protocol for authenticating clients to
the access network using IP based protocols. The PANA protocol
authenticates the client and also establishes a PANA security
association between the PANA client and PANA authentication agent at
the end of a successful authentication. This document discusses the
details for establishing an IPsec security association using the PANA
security association for enabling IPsec based access control.
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Table of Contents
1.0 Introduction..................................................2
2.0 Keywords......................................................3
3.0 Pre-requisites for IPsec SA establisment......................3
4.0 IKE Pre-shared key derivation.................................4
5.0 IKE and IPsec details.........................................5
6.0 Packet Formats................................................5
7.0 IPsec SPD entries.............................................6
8.0 Double IPsec..................................................9
9.0 Security considerations.......................................9
10.0 Normative References.........................................9
12.0 Acknowledgments.............................................10
13.0 Revision log................................................11
14.0 Author's Addresses..........................................11
15.0 Full Copyright Statement....................................11
1.0 Introduction
The PANA (Protocol for carrying Authentication for Network Access)
working group is developing protocol for authenticating clients to
the access network using IP based protocols. The PANA protocol
authenticates the client and also establishes a PANA security
association between the PANA client and PANA authentication agent at
the end of successful authentication. The PANA authentication agent
(PAA) indicates the results of the authentication using the PANA-
Bind-Request message wherein it can indicate the access control
method enforced by the access network. The PANA protocol [PANA-PROT]
does not discuss any details of IPsec [IPSEC] SA establishment, when
IPsec is used for access control. This document discusses the details
of establishing an IPsec security association between PANA client and
the enforcement point. When the IPsec SA is successfully established,
it can be used for access control and specifically used to prevent
the service theft mentioned in [PANA-THREATS].
Please refer to [PANAREQ] for terminology and definitions of terms
used in this document. The following picture illustrates what is
being protected with IPsec. As shown in Figure 1, PANA Authentication
Agent (PAA), Enforcement Point (EP) and the Access Router (AR) are
co-located. The IPsec security association protects the traffic
between PaC and EP. In IPsec terms, EP is a security gateway
(therefore a router) and forwards packets coming from the PaC to
other nodes.
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PaC ----------------------+
[D1] |
+------EP/PAA/AR
|
PaC ----------------------+
[D2]
|------IPsec------|
Figure 1
First, this document discusses some of the pre-requisites for IPsec
SA establishment. Next, it gives details on what should be
communicated between PAA and EP. Then, it gives the details of
IKE/IPsec exchange with packet formats and SPD entries. Finally, it
discusses the issues when IPsec is used for remote access together
with local access.
2.0 Keywords
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 [KEYWORDS].
3.0 Pre-requisites for IPsec SA establisment
This document assumes that the following have already happened before
the IPSEC SA is established.
1) PANA client (PaC) and PAA mutually authenticate each other using
EAP methods that derive Master Session Key (MSK).
2) PaC learns the IP address of the Enforcement point (EP) during
the PANA exchange.
3) PaC learns that the network uses IPsec [IPSEC] for securing the
link between PaC and EP during the PANA exchange.
4) PaC configures a link-local address before the PANA protocol
begins. At the end of authentication, it either acquires a
globally reachable address using [DHCP][DHCPV6] or using IKE or
auto-configures an address using stateless auto-configuration
[IPV6-ND] if IPv6 is being used.
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In the case of DHCP and IKE, EP can trivially learn the address
allocated to the client. In the case of auto-configuration
(which includes global address or addresses configured as in
[PRIV]), EP may not know the address assigned to the PaC. Thus,
it may not be able to setup the SPD entries appropriately before
IKE exchange starts. As most of the IKE implementations assume
that the SPD can be consulted during the SA negotiation, it may
require slightly a different behavior from IKE in the auto-
configuration case. In the case of auto-configuration, IKE
should be able to setup the SAs for the traffic selectors
specified by the PaC without consulting the SPD entry. If there
is already an SA for the same address, then the SA request MUST
be rejected with INVALID-ID-INFORMATION [IKE]. If PaC
authenticates itself successfully, EP should add the SPD entry
for protecting the subsequent data packets.
4.0 IKE Pre-shared key derivation
If the network chooses IPsec to secure the link between PaC and EP,
PAA should communicate the IKE pre-shared key, the IP address of the
PaC and the PANA session ID to EP before the IKE exchange begins. As
EP and PAA are assumed to be co-located,this might be just an API
call.
The IKE exchange between PaC and PAA is equivalent to the 4-way
handshake in [IEEE80211i] following the EAP exchange. The IKE
exchange establishes the IPsec SA similar to the pair-wise transient
keys (PTK) established in [IEEE80211i]. The IKE exchange provides
both key confirmation and protected cipher-suite negotiation.
IKE pre-shared key is derived as follows.
IKE Pre-shared Key = HMAC-SHA-1 (MSK, "IKE-preshared key" |
Session ID | MSK-ID)
The values have the following meaning:
MSK: The Master Session Key (MSK) is provided by the EAP method as
part of the PANA/EAP protocol execution. Please refer to [EAP-KEY]
for details.
Session ID: The value as defined in the PANA protocol [PANA-PROT],
identifies a particular session of a client.
MSK-ID: This identifies the MSK within a given session. During the
lifetime of the PANA session, there could be multiple EAP re-
authentications. As EAP re-authentication changes the MSK, MSK-ID is
used to identify the right MSK. This AVP is yet to be defined in
[PANA-PROT].
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The character "|" denotes concatenation as defined in [IKE].
During EAP re-authentication, the MSK changes. Whenever the MSK
changes, a new value of MSK-ID is established between the PaC and
PAA/EP. If there is already an IKE SA established, it can continue to
be used till it expires. A change in the value of MSK need not result
in re-negotiating a new IKE SA or IPsec SA immediately. But any new
negotiation of IKE SA should use the new pre-shared key derived from
the latest MSK and is indicated by the MSK-ID in the above equation.
5.0 IKE and IPsec details
IKE [IKE] MUST be used for establishing the IPsec SA. The details
specified in this document would work with IKEv2 [IKEV2] also. Any
difference between them would be explicitly noted. PANA authenticates
the client and derives the keys to protect the traffic. Hence, manual
keying cannot be used. Aggressive mode with pre-shared key MUST be
supported. PaC and EP SHOULD use its PANA session ID [PANA-PROT] as
the payload of ID_KEY_ID in aggressive mode for establishing the
phase I SA. IP addresses cannot be used as identifier as the PaC may
be re-authenticated multiple times and hence may not uniquely
identify the pre-shared key. For the same reason, main mode of IKE
cannot be used as it requires addresses to be used as identifiers.
After Phase I SA is established, quick mode exchange is performed to
establish an ESP tunnel mode IPsec SA for protecting the traffic
between PaC and EP. The identities used during Phase II are explained
below. The next few sections discuses the packet formats and SPD
entries.
6.0 Packet Formats
Following acronyms are used throughout this document.
PaC's link-local address is denoted by PAC-LINK-LOCAL.
PaC's global address (which could be either auto-configured or
assigned using [DHCP][DHCPv6][IKE][IKEv2] or addresses specified in
[PRIV] if IPv6 is being used) is denoted by PAC-GLOBAL-ADDR.
EP's link-local address is denoted by EP-LINK-LOCAL.
The node with which the PaC is communicating is denoted by END-ADDR.
The link-local address is used as the outer header of the tunneled
packet as mentioned below.
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Following is the packet format on the wire for packets sent from PaC
to EP:
IPv4/IPv6 header (source = PAC-LINK-LOCAL,
destination = EP-LINK-LOCAL)
ESP header
IPv4/IPv6 header (source = PAC-GLOBAL-ADDR,
destination = END-ADDR)
Following is the packet format on the wire for packets sent from EP
to PaC:
IPv4/IPv6 header (source = EP-LINK-LOCAL,
destination = PAC-LINK-LOCAL)
ESP header
IPv4/IPv6 header (source = END-ADDR,
destination = PAC-GLOBAL-ADDR)
7.0 IPsec SPD entries
The SPD entries for IPv4 and IPv6 are specified separately as they
are different.
7.1 IPv4 SPD entries
PaC's SPD OUT:
IF source = PAC-GLOBAL-ADDR & destination = any
THEN USE ESP TUNNEL MODE SA:
outer source = PAC-LINK-LOCAL
outer destination = EP-LINK-LOCAL
PaC's SPD IN:
IF source = any & destination = PAC-GLOBAL-ADDR
THEN USE ESP TUNNEL MODE SA:
outer source = EP-LINK-LOCAL
outer destination = PAC-LINK-LOCAL
EP's SPD OUT:
IF source = any & destination = PAC-GLOBAL-ADDR
THEN USE ESP TUNEL MODE SA:
outer source = EP-LINK-LOCAL
outer destination = PAC-LINK-LOCAL
EP's SPD IN:
IF source = PAC-GLOBAL-ADDR & destination = any
THEN USE ESP TUNNEL MODE SA:
outer source = PAC-LINK-LOCAL
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outer destination = EP-LINK-LOCAL
During the IPsec SA setup, PaC uses PAC-GLOBAL-ADDR as its phase 2
identity (IDci) and EP uses ID_IPV4_ADDR_RANGE or ID_IPV4_ADDR_SUBNET
as its phase 2 identity. The starting address is zero IP address and
the end address is all ones for ID_IPV4_ADDR_RANGE. The starting
address is zero IP address and the end address is all zeroes for
ID_IPV4_ADDR_SUBNET.
7.2 IPv6 SPD entries
The IPv6 SPD entries are slightly different from IPv4 to prevent the
neighbor and router discovery [IPV6-ND] packets from being protected
with IPsec. The first three entries of the following SPD tables
bypass IPsec protection for neighbor and router discovery packets.
The latest version of the IPsec [IPSEC-BIS] document allows traffic
selectors to be based on ICMPv6 type and code values. In that case,
the first three entries can be based on ICMPv6 type and code values.
All traffic destined to global address is always sent to the default
router (EP) i.e, the global prefix is not considered to be on-link.
This can be achieved by turning off the "L" bit in the router
advertisement.
Pac's SPD OUT:
IF source = ::/128 & destination = any
THEN BYPASS
IF source = fe80::/10 & destination = any
THEN BYPASS
IF source = any & destination = fe80::/10
THEN BYPASS
IF source = PAC-GLOBAL-ADDR & destination = any
THEN USE ESP TUNNEL MODE SA:
outer source = PAC-LINK-LOCAL
outer destination = EP-LINK-LOCAL
PaC's SPD IN:
IF source = ::/128 & destination = any
THEN BYPASS
IF source = fe80::/10 & destination = any
THEN BYPASS
IF source = any & destination = fe80::/10
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THEN BYPASS
IF source = any & destination = PAC-GLOBAL-ADDR
THEN USE ESP TUNNEL MODE SA:
outer source = EP-LINK-LOCAL
outer destination = PAC-LINK-LOCAL
EP's SPD OUT:
IF source = ::/128 & destination = any
THEN BYPASS
IF source = fe80::/10 & destination = any
THEN BYPASS
IF source = any & destination = fe80::/10
THEN BYPASS
IF source = any & destination = PAC-GLOBAL-ADDR
THEN USE ESP TUNNEL MODE SA:
outer source = EP-LINK-LOCAL
outer destination = PAC-LINK-LOCAL
EP's SPD IN:
IF source = ::/128 & destination = any
THEN BYPASS
IF source = fe80::/10 & destination = any
THEN BYPASS
IF source = any & destination = fe80::/10
THEN BYPASS
IF source = PAC-GLOBAL-ADDR & destination = any
THEN USE ESP TUNNEL MODE SA:
outer source = PAC-LINK-LOCAL
outer destination = EP-LINK-LOCAL
During the IPsec SA setup, PaC uses PAC-GLOBAL-ADDR as its phase 2
identity (IDci) and EP uses ID_IPV6_ADDR_RANGE or ID_IPV6_ADDR_SUBNET
as its phase 2 identity. The starting address is zero IP address and
the end address is all ones for ID_IPV6_ADDR_RANGE. The starting
address is zero IP address and the end address is all zeroes for
ID_IPV6_ADDR_SUBNET.
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8.0 Double IPsec
If the PaC uses IPsec for secure remote access e.g., Corporate VPN
access, there will be separate SPD entries protecting the traffic
to/from remote network. In this case, IPsec may need to be applied
twice, once for protecting the remote access and once for protecting
the local access. This is the same as the iterative tunneling
discussed in [IPSEC].
When the IPsec SA is established with the remote security gateway,
the IKE packets from the PaC to the remote security gateway may or
may not need IPsec protection on the local link depending on the
configuration at the EP. If EP requires IPsec protection for all
packets, then the PaC should configure SPD entries appropriately so
that IKE packets destined to EP are bypassed whereas IKE packets to
the remote SG are protected. If EP does not require IPsec protection
for IKE packets destined to remote security gateway, it needs to
configure SPD entries that would bypass them.
9.0 Security considerations
This document discusses the use of IPsec for access control when PANA
is used for authenticating the clients to the access network.
If the PAA does not verify whether PaC is authorized to use an IP
address, it is possible for the PaC to steal the traffic destined to
some other PaC. The use of IPsec does not prevent this attack. PAA
may use other mechanisms to prevent this attack.
When IPv6 is used, the SPD entries bypass all link-local traffic
without applying IPsec. This should not be a limitation as the link-
local address is used only by link-local services e.g.
neighbor/router discovery, which uses a different mechanism to
protect their traffic. Moreover, this limitation may not be there in
the future if IPsec extends the SPD selectors to specify ICMP types.
10.0 Normative References
Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9,
RFC 2026, October 1996.
[IPSEC] S. Kent et al., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998
11.0 Informative References
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[PANAREQ] A. Yegin et al., "Protocol for Carrying Authentication for
Network Access (PANA) Requirements and Terminology", draft-ietf-
pana-requirements-04.txt
[PANA-PROT] D.Fosberg et al., "Protocol for Carrying Authentication
for Network Access", draft-ietf-pana-01.txt
[PANA-THREATS] M.Parthasarathy, "PANA Threat analysis and security
requirements", draft-ietf-pana-threats-eval-04.txt
[KEYWORDS] S. Bradner, "Key words for use in RFCS to indicate
requirement levels", RFC 2119, March 1997
[IKE] D. Harkins et al., "Internet Key Exchange", RFC 2409, November
1998
[IKEV2] Charlie Kauffman et al., "Internet Key Exchange(IKEv2)
Protocol", draft-ietf-ipsec-ikev2-11.txt
[IPSEC-BIS] S.Kent, "Security Architecture for the Internet
Protocol", draft-ietf-ipsec-rfc2401bis-00.txt
[DHCP] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
March 1997
[DHCPV6] R. Droms et. al, "Dynamic Host Configuration Protocol for
IPv6", RFC 3315, July 2003
[IPV6-ND] T. Narten et al., "Neighbor Discovery for IP version 6
(IPv6) ", RFC 2461, December 1998
[PRIV] T. Narten et al., "Privacy Extensions for Stateless Address
Autoconfiguration in IPv6", RFC 3041, January 2001
[EAP-KEY] D.Simon et al., "EAP Key Management Framework", draft-
aboba-ppext-key-problem-07.txt
[IEEE80211i] IEEE Draft 802.11I/D5.0, "Draft Supplement to STANDARD
FOR Telecommunications and Information Exchange between Systems –
LAN/MAN Specific Requirements - Part 11: Wireless Medium Access
Control (MAC) and physical layer specifications: Specification for
Enhanced Security", August 2003.
12.0 Acknowledgments
The author would like to thank Francis Dupont, Pasi Eronen, Yoshihiro
Ohba, Jari Arkko, Hannes Tschofenig and other PANA WG members for
their valuable comments and discussions.
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13.0 Revision log
Changes between revision 00 and 01
-Specified the use of ESP tunnel mode SA instead of IP-IP transport
mode SA after working group discussion.
-Specified the IKE pre-shared key derivation.
14.0 Author's Addresses
Mohan Parthasarathy
313 Fairchild Drive
Mountain View CA-94043
Phone: 408-734-8820
Email: mohanp@sbcglobal.net
15.0 Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
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English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
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Funding for the RFC Editor function is currently provided by the
Internet Society.
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