Simple VPN solution using Multi-point Security Association
draft-yamaya-ipsecme-mpsa-05
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| Document | Type |
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|---|---|---|---|
| Authors | Arifumi Yamaya , Takafumi Ohya, Tomohiro Yamagata , Satoru Matsushima | ||
| Last updated | 2015-03-25 | ||
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draft-yamaya-ipsecme-mpsa-05
IPSecME Working Group A. Yamaya
Internet-Draft Furukawa Network Solution
Intended Status: Informational T. Ohya
Expires: September 26, 2015 NTT
T. Yamagata
KDDI
S. Matsushima
Softbank Telecom
March 25, 2015
Simple VPN solution using Multi-point Security Association
draft-yamaya-ipsecme-mpsa-05
Abstract
This document describes the over-lay network solution by utilizing
dynamically established IPsec multi-point Security Association (SA)
without individual connection.
Multi-point SA technology provides the simplified mechanism of the
Auto Discovery and Configuration function. This is applicable for
any IPsec tunnels such as IPv4 over IPv4, IPv4 over IPv6, IPv6 over
IPv4 and IPv6 over IPv6.
Status of this Memo
This Internet-Draft is submitted to IETF 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/.
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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 September 26, 2015.
Copyright and License Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Conventions Used in This Document . . . . . . . . . . . . 4
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Sequence . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Extended format . . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Vendor ID . . . . . . . . . . . . . . . . . . . . . . 8
3.2.2. MPSA_PUT . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Multi-point SA Management . . . . . . . . . . . . . . . . 14
3.3.1. Controller . . . . . . . . . . . . . . . . . . . . . . 14
3.3.2. CPE . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.3. Rekeying . . . . . . . . . . . . . . . . . . . . . . . 15
3.4. Forwarding . . . . . . . . . . . . . . . . . . . . . . . . 15
4. Peer discovery . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1 example of MPSA with BGP for route based VPN . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
5.1. Protected by MPSA . . . . . . . . . . . . . . . . . . . . . 17
5.2 Security issues not to be solved by MPSA . . . . . . . . . . 17
5.2.1 Attack from outside of the group . . . . . . . . . . . . 17
5.2.2 Attack from inside of the group . . . . . . . . . . . . 17
5.3 Forward secrecy and backward secrecy . . . . . . . . . . . . 17
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.1. Normative References . . . . . . . . . . . . . . . . . . . 18
6.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
As described in the problem statement document [ad-vpn-problem],
dynamic, secure and scalable system for establishing SAs is needed.
With multi-point SA, an endpoint automatically discovers other
endpoint. In this draft, an endpoint means an inexpensive CPE, which
can hardly establish large number of IPsec sessions simultaneously.
The CPEs also share a multi-point SA within the same group, and there
is no individual connection between them.
Scalability issue becomes serious in the service, such as triple play
which requires large number of sessions at the same time. MPSA
enables large scale simultaneous sessions even with inexpensive CPEs,
and can avoid scalability issue.
The latency between CPEs can be minimized because of stateless shared
multipoint SA, MPSA is suitable for video and voice services which is
very sensitive to latency.
It can avoid the exhaustive configuration for CPEs and controllers.
No reconfiguration is needed when a new CPE is added, removed, or
changed. It can avoid high load on the controllers.
1.1. Terminology
Multi-point SA - This is similar to Dynamic Full Mesh topology
described in [ad-vpn-problem]; direct connections exist in a hub and
spoke manner, but only one SA for data transfer is shared with all
CPEs.
1.2. Conventions Used in This Document
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].
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2. Motivation
There are two major topologies - Star topology and full-mesh topology
- to communicate securely on over-lay network by using IPsec.
Figure.1 shows star topology. The number of IPsec connection is the
same as the number of CPEs (CPE). Authentication, Authorization and
Accounting (AAA) of each CPE can be achieved on the gateway.
The problem of the star topology is all the traffic go through the
gateway, then it causes high load and latency.
+---------------------------------------------+
| IPsec Gateway |
| |
| +--------------(A<->C)--------------+ |
| | +---(A<->B)---+ +---(B<->C)---+ | |
+---:|-|:-----------:|---|:-----------:|-|:---+
:| |: :| |: :| |:
:| |: :| |: :| |:
:| |: :| |: :| |:
+---:v-v:---+ :| |: +---:v-v:---+
| | :| |: | |
| CPE_A | :| |: | CPE_C |
| | :| |: | |
+-----------+ +--:v---v:--+ +-----------+
| |
| CPE_B |
| |
+-----------+
Figure 1
Figure.2 shows Full-mesh topology. There is no gateways. Each CPE
establishes IPsec connection independently. The latency on this
topology is relatively low compared to star topology.
In large system, there are huge number ((N^2-N)/2) of IPsec
connections. AAA of each CPE is hard to manage in this topology.
Moreover, when a CPE is added, removed or changed, reconfiguration is
needed for all rest of the CPEs.
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+-----------+ +-----------+
| |.....................| |
| CPE_A <-------(A<->C)-------> CPE_C |
| |.....................| |
+---: ^ :---+ +---: ^ :---+
: | : : | :
: | : +-----------+ : | :
: | :........| |........: | :
: +-(A<->B)--> CPE_B <--(B<->C)-+ :
:............| |............:
+-----------+
Figure 2
The solution in this document eliminates the problems listed above.
Figure 3 shows topology of multi-point SA. Traffic between CPEs does
not go through the controller, low latency, AAA of each CPE can be
achieved, the number of IPsec connection is almost same as star
topology, and no reconfiguration is needed for all the rest of CPEs
even when a CPE is added, removed or changed. MPSA controller do not
necessarily need to be router. It is possible to change MPSA
controller for a software, because a communication load which spans
IPsec Gateway by multi-point SA is not big.
+---------------------------------------------+
| MPSA Controller |
| |
+---: | :------------: | :------------: | :---+
: | : : | : : | :
: | : : | : : | :
----------------------------------------- SA to distribute
: | : : | : : | : Multi-point SA
: | : : | : : | :
+---: v :---+ +---: v :---+ +---: v :---+
| | | | | |
| CPE_A | | CPE_B | | CPE_C |
| | | | | |
+--- ^ ^ ---+ +--- ^ ^ ---+ +--- ^ ^ ---+
.....| |..............| |..............| |.....
| | | | | | \
| +----(A<->B)---+ +---(B<->C)----+ | Multi-point SA
+--------------(A<->C)--------------+ for data transfer
.............................................../
Figure 3
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3. Procedure
3.1. Sequence
The multi-point SA capability of the remote host is determined by
an exchange of Vendor ID payloads. In the IKE_SA_INIT exchange,
the Vendor ID payload for this specification is sent if the multi-
point SA is used.
CPE Controller
----------- -----------
HDR, SAi1, KEi,
Ni, V(MPSA) -->
<-- HDR, SAr1, KEr,
Nr, [CERTREQ,] V(MPSA)
MPSA: multi-point SA
The initial exchange (including IKE_AUTH) is same as [IKEV2],
other than Vendor ID payload included in IKE_SA_INIT.
After the initial exchange has finished successfully, a new
INFORMATIONAL exchange is used to distribute multi-point SA to the
CPE, with the Notify payload of MPSA_PUT that includes
cryptographic algorithm, nonce, keying material, SPI and so on.
Keys for multi-point SA is generated according to the contents of
the Notify payload by the CPE. The response of the Notify payload
has empty Encrypted payload.
CPE Controller
----------- -----------
<-- HDR, SK {N(MPSA_PUT)}
HDR, SK {} -->
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3.2. Extended format
3.2.1. Vendor ID
This document defines a new Vendor ID. The content of the payload
is described below.
"multi-point SA"
3.2.2. MPSA_PUT
This document defines a new Notify Message Type MPSA_PUT. The
Notify Message Type of MPSA_PUT is 40960. Notification Data of
MPSA_PUT has a Proposal-substructure-like format. It consists of
Transform-substructure-like structures that have following data.
Description Trans. Reference
Type
-------------------------------------------------------
Encryption Algorithm (ENCR) 1 RFC5996
Pseudorandom Function (PRF) 2 RFC5996
Integrity Algorithm (INTEG) 3 RFC5996
Nonce (NONCE) 241
SK_d (SKD) 242
Lifetime (LIFE) 243
Rollover time 1 (ROLL1) 244
Rollover time 2 (ROLL2) 245
o Nonce - For Transform Type 241, the Transform ID is 1. The
attribute contains actual nonce value with attribute type 16384.
The size of the Nonce Data is between 16 and 256 octets.
Name Number
---------------------------------------------------
NONCE_NONCE 1
Attribute Type Value Attribute Format
------------------------------------------------------------
Nonce Value 16384 TLV
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o SK_d - For Transform Type 242, the Transform ID is 1. The
attribute contains actual SK_d value with attribute type 16385.
The length of SK_d Data is the preferred key length of the PRF.
Name Number
---------------------------------------------------
SKD_SK_D 1
Attribute Type Value Attribute Format
------------------------------------------------------------
SK_d Value 16385 TLV
o Lifetime - For For Transform Type 243, the Transform ID is 1. The
attribute contains actual lifetime value with attribute type
16386. The length of Lifetime Value is 4 octets. Lifetime is
stored in seconds as effective time of the multi-point SA.
Name Number
---------------------------------------------------
LIFE_LIFETIME 1
Attribute Type Value Attribute Format
------------------------------------------------------------
Lifetime Value 16386 TLV
o Rollover time 1 - For Transform Type 244, the Transform ID is 1.
The attribute contains actual rollover time 1 value with attribute
type 16387. The length of Rollover time 1 Value is 4 octets.
Rollover time 1 defines activation time delay for new outbound
multi-point SA.
Name Number
---------------------------------------------------
ROLL1_ROLLOVER1 1
Attribute Type Value Attribute Format
------------------------------------------------------------
Rollover1 Value 16387 TLV
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o Rollover time 2 - For Transform Type 245, the Transform ID is 1.
The attribute contains actual rollover time 2 value with attribute
type 16388. The length of Rollover time 2 Value is 4 octets.
Rollover time 2 defines deactivation time delay for old inbound
multi-point SA.
Name Number
---------------------------------------------------
ROLL2_ROLLOVER2 1
Attribute Type Value Attribute Format
------------------------------------------------------------
Rollover2 Value 16388 TLV
Therefore, the format of the MPSA_PUT of the Notify Message is
described below.
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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 |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol ID | SPI Size | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Parameter Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 (last) or 2 | RESERVED | Proposal Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Proposal Num | Protocol ID | SPI Size |Num Transforms|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Parameter Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 (last) or 3 | RESERVED | Transform Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Transform Type | RESERVED | Transform ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Transform Attributes ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 (last) or 3 | RESERVED | Transform Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Transform Type | RESERVED | Transform ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Transform Attributes ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | RESERVED | Transform Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Transform Type | RESERVED | Transform ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Transform Attributes ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The following example shows a N(MPSA_PUT) notification message. The
SPIs in the Proposal-like and Tranform-like substructure are the same
value. Following values are defined by the example.
Protocol: ESP
ENCR: AES-CBC (256bits)
PRF: SHA-1
INTEG: HAMC-SHA-1-96
NONCE: 241
SKD: 242
LIFE: 243
ROLL1: 244
ROLL2: 245
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 0 (last) |C| RESERVED | Payload Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Notify | 3 (ESP) | SPI Size = 4 | MPSA_PUT |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| Security Parameter Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 0 (last) | RESERVED | Proposal Length |
Pro- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
posal-| Prop Num = 1 | 3 (ESP) | SPI Size = 4 |Num Transforms|
like +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| Security Parameter Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ENCR | 1 (ENCR) | RESERVED | 12 (ENCR_AES_CBC) |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\|1| 14 (Key Length) | 256 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
PRF +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| 2 (PRF) | RESERVED | 2 (PRF_HMAC_SHA1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
INTEG +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| 3 (INTEG) | RESERVED | 2 (AUTH_HMAC_SHA1_96) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
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/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | 241 (NONCE) | RESERVED | 1 |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NONCE |0| 16384 (Nonce) | Attribute Length |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | |
\ ~ [Nonce] ~
\| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | 242 (SKD) | RESERVED | 1 |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
SKD |0| 16385 (SK_d) | Attribute Length |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | |
\ ~ [SK_d] ~
\| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | 243 (LIFE) | RESERVED | 1 |
LIFE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ |0| 16386 (Lifetime) | Attribute Length = 4 |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| [Lifetime] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | 244 (ROLL1) | RESERVED | 1 |
ROLL1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ |0| 16386 (Lifetime) | Attribute Length = 4 |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| [RolloverTime1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/| 3 | RESERVED | Transform Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | 245 (ROLL2) | RESERVED | 1 |
ROLL2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ |0| 16386 (Lifetime) | Attribute Length = 4 |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\| [RolloverTime2] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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3.3. Multi-point SA Management
3.3.1. Controller
Controller generates a multi-point SA for a group before connecting
to any CPEs.
After the initial exchanges have finished, controller distributes the
same multi-point SA information to CPEs within the group by sending
N(MPSA_PUT).
SPI and Nonce is generated similar way of [IKEv2]. SK_d is generated
from random numbers similar to Nonce.
The same SPI value is stored to Notify payload and Proposal-like
substructure.
The multi-point SA will not be negotiated between controller and CPE,
but will be notified from controller to CPE one way.
Controller initiates rekey before Lifetime expiration. As the
Lifetime, controller notifies the effective time left of the multi-
point SA.
3.3.2. CPE
After the initial exchange has finished, CPE obtains multi-point SA
information by receiving N(MPSA_PUT) from controller. The keys for
the multi-point SA are generated in the same procedure described in
[IKEv2], except Ni | Nr is replaced by Nonce.
Therefore, KEYMAT is derived by PRF listed below.
KEYMAT = prf+(SK_d, Nonce)
The multi-point SA is protected in a cryptographic manner by ENCR and
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INTEG which uses the generated keys.
The SPI value for the multi-point SA is the same of its in Notify
message.
CPE uses the same multi-point SA as both inbound and outbound SAs.
CPE deletes both of inbound and outbound SA when Lifetime is
expired.
Rollover time 1, 2 have no meaning when no old multi-point SA exists.
3.3.3. Rekeying
Rekeying should be finished before Lifetime expiration of current
multi-point SA. Rekeying of multi-point SA will be performed as
follows.
- Controller generates a new multi-point SA
- Controller distributes a new multi-point SA to all CPEs within the
group
- CPE replaces the current multi-point SA to new one
CPE replaces multi-point SA using rollover method like [GDOI].
3.4. Forwarding
Each CPE sends and receives encapsulated packets using the multi-
point SA.
The destination address of encapsulated packet will be determined
with routing information, which can achieved by static configuration
or route exchange mechanism such as BGP on encapsulated environment
described in [MESH].
It is applicable for any IPsec tunnels such as IPv4 over IPv4, IPv4
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over IPv6, IPv6 over IPv4 and IPv6 over IPv6.
4. Peer discovery
MPSA does not provide peer discovery function by itself. However,
other mechanism, such as BGP, can be employed with MPSA for automatic
peer discovery. One example is a use of BGP, described in [MESH], to
learn peer information as next-hops.
4.1 example of MPSA with BGP for route based VPN
Between controller and each peer, IKE_SA and CHILD_SA are established
by IKEv2. On the IKE_SA, an MPSA management message (MPSA_PUT) is
served from the controller to the peer.
On the CHILD_SA, the controller and the peer establish a iBGP session
to exchange route information (NLRIs). Controller can act as a BGP
route reflector (RR), which can reflect NLRIs among all iBGP peers of
the controller. In other words, the peer can learn all NLRIs
advertised by all other peers.
According to [ENCAPS], each peer can advertise ESP peer address as
well as conventional NLRIs, all of those can be reflected by RR on
the controller.
At this point, each peer can have all other peer addresses as well as
route information. The peer can decide a peer address by mean of
recursive route lookup from the destination address of a packet to be
forwarded. This decision can be made by the peer itself, without any
additional communication with the controller.
Instead of [ENCAPS], each peer can also do it by [RNH]. Each peer
learns all other peer addresses by BGP Remote-Next-Hop attributes and
decides a peer address from a packet to be forwarded, as same as
using [ENCAPS].
5. Security Considerations
MPSA uses IKEv2 to protect MPSA management message, MPSA_PUT. Thus,
CPEs are authenticated by IKEv2. Using a shared SA for communication
between CPEs, MPSA does not provide the following features.
- Data origin authentication
- Anti-replay protection
MPSA itself does not provide access control for user datagrams, but
peer discovery may be able to provide access control as well as those
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of route based VPN. For example, using BGP for peer discovery
described in 4.1, access control could be provided by filtering
exchanged routes at the controller. In this case, filtering by source
address, protocol and ports can not be achieved. If you need it, you
could do by other security policy rules as local setting at CPEs .
5.1. Protected by MPSA
- Authenticating CPEs and controller Authentication is provided by
IKEv2 with pre-shared key or RSA signature. MPSA management messages
are exchanged after IKEv2 negotiation.
- Confidentiality and integrity Packets are encapsulated by ESP, so
that MPSA provides confidentiality and integrity against outside of
the group, but does not them against members of the group
5.2 Security issues not to be solved by MPSA
5.2.1 Attack from outside of the group
- Anti-replay protection
MPSA does not provide anti-replay protection, because sequence number
synchronization between peers needs additional mechanism. Using a
closed network as a transport might be effective to mitigate this
kind of attacks.
- Leaking a IKE_SA key
If an attacker could sniff packets on a IKE_SA, and key of the SA
were leaked, the attacker may get a key of MPSA by decoding a sniffed
MPSA_PUT message.
5.2.2 Attack from inside of the group
If there is a malicious CPE or a CPE is hijacked by an attacker, MPSA
can be attacked in the following way because MPSA, including
cryptograghic key, is shared by all CPEs.
- An attacker can impersonate another CPE. A closed network that
prohibits source address spoofing could mitigate the impersonating.
- An attacker can decode packets between the other CPEs if the
attacker could sniff packets.
5.3 Forward secrecy and backward secrecy
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MPSA MAY be rekeyed when a CPE is removed from the group, for the
removed CPE not to access the other CPEs communication after that, or
when a CPE is added from the group, for it not to do before that. If
not rekeyed, a removed/added CPE could access
5. IANA Considerations
This memo includes no request to IANA.
6. References
6.1. Normative References
[IKEv2] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010, <http://www.rfc-
editor.org/info/rfc5996>.
[IKEv2] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet
Key Exchange Protocol Version 2 (IKEv2)", RFC 5996,
September 2010.
6.2. Informative References
[GDOI] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, October 2011,
<http://www.rfc-editor.org/info/rfc6407>.
[MESH] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, June 2009, <http://www.rfc-
editor.org/info/rfc5565>.
[ad-vpn-problem]Manral, V. and S. Hanna, "Auto-Discovery VPN Problem
Statement and Requirements", RFC 7018, September 2013,
<http://www.rfc-editor.org/info/rfc7018>.
[GDOI] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain of
Interpretation", RFC 6407, October 2011.
[MESH] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, June 2009.
[ad-vpn-problem] Manral, V. and S. Hanna, "Auto-Discovery VPN Problem
Statement and Requirements", RFC 7018, September 2013.
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[RNH] Van de Velde, G., Patel, K., Rao, D., Raszuk, R., and Bush, R.,
"BGP Remote-Next-Hop", draft-vandevelde-idr-remote-next-
hop-07, June 2014
Authors' Addresses
Arifumi Yamaya
Furukawa Network Solution Corp.
5-1-9, Higashi-Yawata, Hiratsuka
Kanagawa 254-0016, JAPAN
Email: yamaya@fnsc.co.jp
Takafumi Ohya
NTT Corporation
Nishi-shinjuku, Shinjuku-ku,
Tokyo 163-8019, JAPAN
Email: takafumi.ooya@hco.ntt.co.jp
Tomohiro Yamagata
KDDI Corporation
Garden Air Tower
Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN
Email: to-yamagata@kddi.com
Satoru Matsushima
Softbank Telecom Corp.
1-9-1, Higashi-Shimbashi, Minato-Ku
Tokyo 105-7322, JAPAN
Email: satoru.matsushima@g.softbank.co.jp
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