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Network Working Group S. Sugimoto
Internet-Draft Ericsson
Intended status: Informational F. Dupont
Expires: June 17, 2008 CELAR
M. Nakamura
Hitachi
December 15, 2007
PF_KEY Extension as an Interface between Mobile IPv6 and IPsec/IKE
draft-sugimoto-mip6-pfkey-migrate-04
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document describes the need for an interface between Mobile IPv6
and IPsec/IKE and show how the two protocols can interwork. We
propose a set of extensions to the PF_KEY framework which allows
smooth and solid operation of IKE in a Mobile IPv6 environment. The
first extension is called PF_KEY MIGRATE and is for migrating the
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endpoint addresses of a IPsec Security Association pair in tunnel
mode. The second extension is named SADB_X_EXT_PACKET and allows IKE
to make the right choice for address selection in bootstrapping
process. Both extensions are helpful for assuring smooth
interworking between Mobile IPv6 and IPsec/IKE and achieving
performance optimization.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Needs for Interactions between Mobile IPv6 and IPsec/IKE . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. PF_KEY Extensions for Mobile IPv6 . . . . . . . . . . . . . . 4
4.1. PF_KEY MIGRATE Message . . . . . . . . . . . . . . . . . . 5
4.1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.2. Message Sequence . . . . . . . . . . . . . . . . . . . 6
4.1.3. Issuing PF_KEY MIGRATE Message . . . . . . . . . . . . 7
4.1.4. Processing PF_KEY MIGRATE Message . . . . . . . . . . 8
4.1.5. Applicability of PF_KEY MIGRATE to Other Systems . . . 9
4.1.6. NAT Traversal . . . . . . . . . . . . . . . . . . . . 10
4.1.7. Limitation of PF_KEY MIGRATE . . . . . . . . . . . . . 10
4.1.8. Interoperability Issue . . . . . . . . . . . . . . . . 10
4.2. PF_KEY Packet Extension . . . . . . . . . . . . . . . . . 11
4.2.1. Inserting Packet Extension to SADB_ACQUIRE Message . . 12
4.2.2. Extracting Home Registration Information from
Acquire Message . . . . . . . . . . . . . . . . . . . 12
4.2.3. Relation of Packet Extension to IKEv2 . . . . . . . . 13
5. Necessary Modifications to Mobile IPv6 and IPsec/IKE . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. PF_KEY MIGRATE Message Format . . . . . . . . . . . . 16
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 20
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1. Introduction
In Mobile IPv6 [RFC3775], the Mobile Node (MN) and the Home Agent
(HA) use some IPsec Security Associations (SAs) in tunnel mode to
protect some mobility signaling messages, mobile prefix discovery and
optionally payload traffic. Since the MN may change its attachment
point to the Internet, it is necessary to update its tunnel endpoint
address of the IPsec SAs. This indicates that corresponding entry in
IPsec databases (Security Policy (SPD) and SA (SAD) databases) should
be updated when MN performs movements. In addition, IKE requires
treatment to keep its IKE session alive in a Mobile IPv6 environment.
This document describes the need for an interface between Mobile IPv6
and IPsec/IKE and shows how the two protocols can interwork. We
propose a set of extensions to the PF_KEY framework [RFC2367] which
allows smooth and solid operation of IKE in an Mobile IPv6
environment. The first extension is called PF_KEY MIGRATE and is for
migrating the endpoint addresses of the IPsec SAs in tunnel mode.
The second extension is named SADB_X_EXT_PACKET and allows IKE to
make the right choice in address selection in the bootstrapping
process. Both extensions are helpful for assuring smooth
interworking between Mobile IPv6 and IPsec/IKE and achieving
performance optimization.
In this document, the term IKE implicitly stands for both IKEv1
[RFC2409] and IKEv2 [RFC4306]. In description with regard to any
functionality that is specific to either of the protocols, specific
protocol name shall be provided.
2. Needs for Interactions between Mobile IPv6 and IPsec/IKE
The section 4.4 of RFC 3776 [RFC3776] specifies the rules which
applies to IKE for MNs and HAs. The first requirement is to run IKE
over the Care-of Address (CoA) because the Home Address (HoA) is
usable only after the home registration so not yet in the
bootstrapping phase.
A tunnel IPsec SA pair protects some signaling messages and
optionally all the traffic between the MN and HA. The initial SPD
entry uses the HoA for the MN endpoint address and updates this
address to the new CoA at each movement. A tunnel SA pair is created
on demand and is updated too. The RFC 3775 [RFC3775] assumes there
is an API which performs the update in the SPD and SAD on both the MN
and HA. This document is mainly about this API.
Mobile IPv6 specifies a flag named Key Management Mobility Capability
bit (K-bit) in Binding Update (BU) and Binding Acknowledgement (BA)
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messages (section 10.3.1 of [RFC3775]), which indicates the ability
of IKE sessions to survive movement. When both the MN and HA agree
to use this functionality, the IKE daemons dynamically update the IKE
session when the MN moves. In order to realize this, IKE daemons
should be notified by Mobile IPv6, and necessary information to
migrate the IKE session should be provided.
Mobile IPv6 may need to make an access to the SPD not only for
updating an endpoint address but also for the deletion/insertion of a
specific SPD entry. When the MN performs Foreign-to-Home movement,
IPsec SAs established between the MN and HA should be deleted, which
means that the SPD entry should have no effect any more. On the
other hand, when the MN performs Home-to-Foreign movement, the IPsec
SAs should be restored. Hence security policy entries that are
associated with tunnel mode SAs may dynamically be added/removed
(enabled/disabled) in along with MN's movements.
It should be noted that NEMO Basic Support [RFC3963] has similar
requirements for the Mobile Router (MR) and MR's HA (MRHA). In NEMO,
the MR works just as same as a MN registering its location
information to the MRHA and establishes a tunnel (IP-in-IP or IPsec
tunnel). When an IPsec tunnel is established between MR and MRHA,
the MR serves as a Security Gateway for the nodes connected to the
mobile network. The MR is responsible for handling its tunnel
endpoint properly.
3. Requirements
Given the need for an interface between Mobile IPv6 and IPsec/IKE,
there should be a minimum interface between the two protocols.
Followings are the requirements for the interface from a software
engineering point of view.
o Necessary modifications to the existing software, namely Mobile
IPv6 and IPsec/IKE, in order to realize proposed mechanisms,
should be kept minimum.
o Proposed mechanism should not be platform dependent. The
mechanism should be based on technology which is commonly
available on various platform. This seems to be essential for
achieving high portability of the implementation which supports
proposed mechanisms.
4. PF_KEY Extensions for Mobile IPv6
In order to fulfill the needs and requirements described in Section 2
and Section 3 we propose to extend the PF_KEY framework so that
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Mobile IPv6 and IPsec/IKE could interact with each other.
4.1. PF_KEY MIGRATE Message
The first extension is primarily for migrating an endpoint address of
an IPsec SA pair in tunnel mode from one to another, which results in
updating IPsec databases. A new PF_KEY message named MIGRATE is
introduced for the mechanism.
4.1.1. Overview
The figure below illustrates how Mobile IPv6 and IPsec/IKE components
interact with each other using PF_KEY MIGRATE messages in a dynamic
keying scenario. On left top, there is a Mobile IPv6 entity. It may
be possible that Mobile IPv6 component is completely implemented
inside the kernel (this is the case for our implementations because
it makes some facilities and extensions far easier at the cost of
maintaining a SPD image in daemons). In any case, Mobile IPv6 should
be the one which issues the MIGRATE messages. On right top, there is
an IKE daemon which is responsible for establishing SAs required for
Mobile IPv6 operation. In a manual keying scenario, the difference
is only that there is no IKE daemon running on the system.
+-------------+ +------------+
| | | |
| Mobile IPv6 | | IKE Daemon |
| | | |
+-------------+ +------------+
| 1. PF_KEY A 4. Update
| MIGRATE | SPD & SAD
+-----------+ +-----------+
| |
Userland V |
==========================[PF_KEY Socket]========================
Kernel | |
+----------+ +----------+
| 2. Update | 3. Update
V SPD V SAD
+-----------+ +------------+
| | | |
| SPD | | SAD |
| | | |
+-----------+ +------------+
The primary role of PF_KEY MIGRATE messages is to migrate endpoint
addresses of tunnel mode SA pairs requesting IPsec to update its
databases (SPD and SAD). In addition, the new message can be used by
IKE to enhance its mobility capability. When a PF_KEY MIGRATE
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message is properly processed by the kernel, it is sent to all open
sockets as normal PF_KEY messages. The processing of a sequence of
MIGRATE messages is done in following steps:
o Mobile IPv6 issues a PF_KEY MIGRATE message to the PF_KEY socket.
o The operating system (kernel) validates the message and checks if
corresponding security policy entry exists in SPD.
o When the message is confirmed to be valid, the target SPD entry is
updated according to the MIGRATE message. If there is any target
SA found that are also target of the update, those should also be
updated.
o After the MIGRATE message is successfully processed inside the
kernel, it will be sent to all open PF_KEY sockets.
o The IKE daemon receives the MIGRATE message from its PF_KEY socket
and updates its SPD and SAD images. The IKE daemon may also
update its state to keep the IKE session alive.
Note that the way IKE maintains its local copy of SPD (the SPD image)
is an implementation specific issue since there is no standard
interface to access SPD. Some IKE implementation may continuously
monitor the SPD inside the kernel. Some IKE implementation may
expect notification from the kernel when the SPD is modified. In
either way, the proposed mechanism gives a chance for IKE to keep its
SPD image up-to-date which is significant in Mobile IPv6 operation.
4.1.2. Message Sequence
Next, we will see how migration takes place in along with home
registration. The figure below shows sequence of mobility signaling
and PF_KEY MIGRATE messages while the MN roams around links. It is
assumed that in the initial state the tunnel endpoint address for a
given MN is set as its home address. In the initial home
registration, the MN and HA migrate the tunnel endpoint address from
the HoA to CoA1. It should be noted that no migration takes place
when the MN performs re-registration since the care-of address
remains the same. Accordingly, the MN performs movement and changes
its primary care-of address from CoA1 to CoA2. A PF_KEY MIGRATE
message is issued on both MN and HA for each direction. When the MN
returns to home, migration takes place updating the endpoint address
with the MN's home address.
With regard to the timing of issuing a MIGRATE message on the MN
side, the message can be issued immediately after the home
registration. That is, there is no need to wait until the
acknowledgment from the HA to issue migrate the endpoint addresses
stored in the IPsec databases. The Mobile IPv6 specification
([RFC3775] Section 11.6.3) actually allows the MN to start using the
new care-of address immediately after sending a BU message to the HA.
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This may help the MN to minimize the packet loss of its outbound
traffic during the handover.
MN HA
| |
~ ~
Movement->| BU (Initial home registration) |
|----------------------------------------->|
MIGRATE ->| BA |<- MIGRATE
(HoA->CoA1) |<-----------------------------------------| (HoA->CoA1)
| |
~ BU (Home re-registration) ~
|----------------------------------------->|
| BA |
|<-----------------------------------------|
| |
~ ~
| |
Movement->| BU (Home registration) |
|----------------------------------------->|
MIGRATE ->| BA |<- MIGRATE
(CoA1->CoA2)|<-----------------------------------------| (CoA1->CoA2)
| |
~ ~
Movement->| BU (Home de-registration) |
|----------------------------------------->|
MIGRATE ->| BA |<- MIGRATE
(CoA2->HoA) |<-----------------------------------------| (CoA2->HoA)
| |
4.1.3. Issuing PF_KEY MIGRATE Message
The Mobile IPv6 entity (MN or HA code) triggers the migration by
sending a PF_KEY MIGRATE message to its PF_KEY socket. Conceptually,
the PF_KEY MIGRATE message should contain following information:
o Selector information:
* source address/port
* destination address/port
* upper layer protocol (i.e., Mobility Header)
* direction (inbound/outbound)
o Old SA information:
* old source endpoint address
* old destination endpoint address
* IPsec protocol (ESP/AH)
* mode (Tunnel)
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o New SA information:
* new source endpoint address
* new destination endpoint address
* IPsec protocol (ESP/AH)
* mode (Tunnel)
Selector information is required for specifying the target SPD entry
to be updated. Basically the information should contain necessary
elements which characterize traffic selector as specified in the
IPsec architecture ([RFC2401], [RFC4301]). With regard to the upper
layer protocol, when the Mobile IPv6 stack is not fully aware of
IPsec configuration, an wild-card value could be given. In such
case, an upper layer protocol information should not be taken into
account for searching SPD entry. Plus, the direction of the security
policy (inbound/outbound) should be provided. The old SA information
is used to specify target security association to be updated. The
source and destination addresses of the target entry should be
overwritten with the ones included in the new SA information. Note
that the IPsec protocol and mode fields should not be updated by a
PF_KEY MIGRATE message.
A PF_KEY MIGRATE message should be formed based on security policy
configuration and binding record. The selector information and some
parts of the SA information (IPsec protocol and mode) should be taken
from the policy configuration. The rest of the information should be
taken from the sequential binding information. For example, in the
case where the MN updates its inbound security policy and
corresponding tunnel mode SA pair, the old source address should be
set as its previous CoA, and the new source address should be set as
its current CoA. Hence, the MN should sequentially keep track of its
CoA record. Such information shall be stored in binding update list
entry. For the same reason, the HA should keep track of previous
CoAs of MNs. Such information shall be stored in binding cache
entry.
Additionally, a piece of information which indicates a mobility
capability of IKE (K-bit) should be provided by any means. This
makes it possible for IKE to see if there is a need to update its
state (IKE endpoint addresses) in accordance with PF_KEY MIGRATE
messages.
A detailed message format of PF_KEY MIGRATE is provided in
Appendix A.
4.1.4. Processing PF_KEY MIGRATE Message
Since a PF_KEY MIGRATE message is applied to a single SPD entry, the
kernel should first check validity of the message. If the message is
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invalid, an EINVAL error MUST be returned as a return value for the
write() operation made to the PF_KEY socket. After the validation,
the kernel checks if the target SPD entry really exists. If no entry
is found, an ENOENT error MUST be returned. If a SPD entry is found
and successfully updated, a success (0) MUST be returned regardless
of subsequent result of SAD lookup/update. Note that there may be a
case where a corresponding SAD entry does not exist even if a SPD
entry is successfully updated. In any error case, a PF_KEY MIGRATE
message MUST NOT have any effect on the SPD and SAD.
With respect to the behavior of a normal process (including the IKE
daemon) which receives a PF_KEY MIGRATE message from a PF_KEY socket,
it SHOULD first check if the message does not include erroneous
information. When there is any error indicated, the process MUST
silently discard the PF_KEY MIGRATE message. Otherwise, the
processing of the message may continue.
4.1.5. Applicability of PF_KEY MIGRATE to Other Systems
The PF_KEY MIGRATE extension can also be applied to other systems
than Mobile IPv6. In some systems, there is a need to update
endpoint address of IPsec security association for various reasons
such as mobility management and multihoming.
In a Mobile VPN scenario (aka "road warrior"), client node roams
around different IP subnets while maintaining security association
with the security gateway. Just like the case in Mobile IPv6, both
of the IKE peers need to update the endpoint of the IPsec tunnel and
PF_KEY MIGRATE message can be used for the update.
In HIP mobility management scenario[I-D.ietf-hip-mm], a mobile host
can maintain a HIP association with its peer while moving around IP
subnets. When the mobile host changes its attachment point to the
Internet, it sends an UPDATE message to the peer reporting its new
locator. Since HIP association is represented by an IPsec security
association of ESP BEET mode, the same mechanism can be applied for
the purpose of updating endpoint. The procedure of MIGRATE can take
place when the mobile host detects movement and when the peer
receives the UPDATE message.
From the ID/Locator separation point of view, PF_KEY MIGRATE is
designed to update locators stored in an IPsec security association.
Hence, the message can be applied to IPsec security association in
tunnel mode. However, there are exceptional cases where IPsec
security associations are bundled. In some case, a transport mode
security association may be bundled with a tunnel mode security
association. For instance, a combination of AH (transport mode) and
ESP (tunnel mode) may assure confidentiality of the payload as well
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as data integrity of the whole IP packet including outer header. In
such case, PF_KEY MIGRATE message may be used for updating endpoint
addresses of IPsec transport mode.
4.1.6. NAT Traversal
Dual Stack Mobile IPv6 [I-D.ietf-mip6-nemo-v4traversal] supports a
scenario where a MN is connected to a network behind a Network
Address Translator (NAT). In such case, the MN assigns an IPv4
private address to its network interface but it is still capable of
registering its care-of address to the HA, using the NAT Traversal
technique [RFC3948]. The MN and HA leverage an IPsec tunnel to
protect the return routability messages.
It is possible for the PF_KEY MIGRATE message to handle IPv4 private
address when the MN is behind a NAT device. In a NAT Traversal case,
the endpoint address of the MN is characterized by the IP address and
the pair of source and destination port numbers used for the UDP
encapsulation. Therefore, in a NAT Traversal scenario, a Mobile IPv6
module MUST issue a PF_KEY MIGRATE message along with the pair of
source and destination port numbers of a UDP encapsulation, to handle
IPv4 private address.
4.1.7. Limitation of PF_KEY MIGRATE
Currently, a Security Parameter Index (SPI) is not included in the
old SA information to specify target SAD entry. This helps to lessen
operational burden of Mobile IPv6. However, this simplification can
produce ambiguity in searching for the target security association
entry. When the unique SPD level is available, it should be used
because it avoids this problem both by marking the SAs to update and
by limiting SA sharing.
It should be noted that delivery of PF_KEY MIGRATE messages cannot be
guaranteed, which is common to other PF_KEY messages. It may be
possible that a MIGRATE message is lost. In such case, there will be
inconsistency between the binding record managed by Mobile IPv6 and
IPsec database inside the kernel or the IKE daemon. Once a PF_KEY
MIGRATE message is lost, it would not be possible for the receiver to
process some subsequent MIGRATE messages properly. Reinitialization
of the Mobile IPv6 stack and IPsec databases may be needed for
recovery.
4.1.8. Interoperability Issue
It is a choice of implementers whether to support the PF_KEY MIGRATE
message in their MIPv6 and IPsec/IKE implementations. However,
asymmetry in the support of the PF_KEY MIGRATE message may cause an
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interoperability issue in some case.
It should be noted that an interoperability issue may be raised when
the HA does not support PF_KEY MIGRATE message whereas the MN does
support the mechanism. This is based on the working assumption that
HA serves as a responder in the IKE negotiations conducted to
maintain the IPsec SAs required for MIPv6 operation. It is unlikely
that the HA serves as an initiator in the IKE negotiation in the
MIPv6 network scenario for practical reasons. Thus, the HA without
the support of PF_KEY MIGRATE suffers from having the old information
in the IPsec database. More specifically, the HA may forward the IP
packets destined for the MN to a wrong destination.
Therefore, it is RECOMMENDED that HA implements PF_KEY MIGRATE
message or equivalent function to avoid an interoperability issue
with regard to the dynamic update of IPsec database.
4.2. PF_KEY Packet Extension
In the bootstrapping stage of Mobile IPv6, the MN and HA need to
establish IPsec SA to protect signaling messages of Mobile IPv6 such
as BU and BA. When IKE is used to establish and maintain the SA
pairs, the IKE negotiation is the very first transaction made between
the MN and HA.
As mentioned in [RFC3776], a care is needed for the address
management of the IKE negotiation in Mobile IPv6 environments. In
particular, IKE negotiation to be made to establish a transport mode
IPsec SA pair is tricky in a sense that the IKE endpoint and the SA
address on the MN side are different; IKE endpoint must be an IP
address other than the home address of the MN, whereas the SA address
must be the MN's home address. This is because the home address
cannot be used prior to the initial home registration. The best
candidate for the IKE endpoint on MN side is the primary care-of
address of the MN since it is verified by the Mobile IPv6 module to
work.
For the above reasons, there is a need to guide IKE module to make
the right choice of IKE endpoint and SA address. More specifically,
IKE module should be notified on which IP address the IKE negotiation
should run.
A simple solution which enables the notification is to add the
information of the triggering packet to the SADB_ACQUIRE message.
The extension is called Packet Extension, which allows a receiver of
a SADB_ACQUIRE message (e.g. IKE module) to inspect the triggering
packet and take necessary action, such as choosing specific IP
address as an IKE endpoint for the subsequent IKE negotiation.
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The following is a structure of an extended SADB_ACQUIRE message. As
the figure shows, information of the triggering packet is appended to
the SADB_ACQUIRE message.
<base, address(SD), address(P)*, identity(SD)*,
sensitivity*, proposal, packet*>
4.2.1. Inserting Packet Extension to SADB_ACQUIRE Message
The IPsec subsystem MAY include a Packet Extension to a SADB_ACQUIRE
message when absence of IPsec SA is detected during outbound packet
processing. The IP packet to be included in the Packet Extension
MUST be the very IP packet which triggered the ACQUIRE message IPsec
sublayer.
The information of the triggering packet MUST contain IP header, IP
header options (in the case of IPv4), IP extension headers (in the
case of IPv6), and the transport layer protocol header if there is
any.
More than one packet extensions MUST NOT be appended to a
SADB_ACQUIRE message.
The figure below shows the format of the Packet Extension which
conforms the extension header specified in [RFC2367].
struct sadb_x_packet {
uint16_t sadb_packet_len;
uint16_t sadb_packet_exttype;
uint32_t sadb_packet_copylen;
};
/* sizeof(struct sadb_x_packet) == 8 */
/* followed by an IP packet header which triggered
the SADB_ACQUIRE message */
sadb_packet_copylen Indicates the exact length of the packet header
that follows the extension header. Note that the 64 bit alignment
rule applies to the Packet Extension thus there could be padding
appended to meet the alignment requirement. This padding SHOULD
be set to zero by the sender (kernel) and MUST be ignored by the
receiver.
4.2.2. Extracting Home Registration Information from Acquire Message
A receiver of a SADB_ACQUIRE message with a Packet Extension MAY
extract and process the extension header.
A Mobile IPv6 aware IKE daemon should be able to process a Packet
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Extension which includes the IPv6 packet containing the initial home
registration BU message. An IPv6 packet which contains following
information is suspected to be a home registration Binding Update
message:
o A mobility header message with message type 5 (BU).
o In the BU message, Home Registration (H) bit is set.
The source address field of the IPv6 header is supposed to be the
home address of the MN. In some systems, a home address destination
option may be present in the IP packet. In such case, a care is
needed to extract the care-of address of the MN. In any case, the
care-of address MUST be extracted from the alternate care-of address,
if the option is present in the packet.
Recommendation: Mobile IPv6 module is recommended to include an
alternate care-of address option in every BU message, regardless of
the type of IPsec protocol (AH or ESP) which is used to protect the
message.
4.2.3. Relation of Packet Extension to IKEv2
The Packet Extension is useful not only for Mobile IPv6 usage but
also for other network scenarios where IKEv2 is used as a key
management protocol.
In IKEv2 [RFC4306], it is specified that the first traffic selector
of TSi and TSr should contain the information of triggering packet
when an initiator requests establishment of IPsec SA triggered by a
data packet. The Packet Extension can provide the information of the
triggering packet to the IKE module.
5. Necessary Modifications to Mobile IPv6 and IPsec/IKE
In order to realize the proposed mechanism, there are some necessary
modifications to Mobile IPv6 and IPsec/IKE. Following are the
summary of necessary modifications, which could be of interest to
implementors of Mobile IPv6 and/or IPsec/IKE.
o Modifications to Mobile IPv6:
* The Mobile IPv6 code can make an access to PF_KEY socket. In
particular, the Mobile IPv6 code should have privilege to write
messages into a PF_KEY socket.
* Issuing PF_KEY MIGRATE messages: in order to send MIGRATE
messages, it is required that the Mobile IPv6 code has some
knowledge of its IPsec configuration and precise binding
record. The Mobile IPv6 code may be aware of exact IPsec
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configuration in form or security policy. It would also be
possible that the Mobile IPv6 code is only aware of minimum
IPsec configuration whether if IPsec is utilized or not.
o Modifications to IPsec:
* Processing PF_KEY MIGRATE messages: the kernel should be able
to process PF_KEY MIGRATE messages sent by the Mobile IPv6
code. Unless the message is invalid, it should be sent to all
open PF_KEY sockets.
* Enabling Packet Extensions (SADB_X_EXT_PACKET): the kernel
should be able to append a SADB_X_EXT_PACKET extension to
SADB_ACQUIRE messages when they are triggered by an output of a
data packet.
o Modifications to IKE:
* Processing PF_KEY MIGRATE messages: the IKE code may update its
local copy of IPsec databases (SPD and SAD) in accordance with
received PF_KEY MIGRATE messages. In addition, it may update
its state / IKE session with new endpoint addresses indicated
by PF_KEY MIGRATE messages.
* Processing of Packet Extensions (SADB_X_EXT_PACKET): the IKE
code may process SADB_X_EXT_PACKET extensions and extract
necessary information from triggering packets. In order for
the IKE code to be MIPv6-aware, it should properly extract the
home address, care-of address, and HA address from IP packets
which carry home registration BU messages.
6. Security Considerations
The proposed schemes in this document do not raise any security issue
with regard to the authenticity of the IP packets to be handled under
the protection of an IPsec SA pair in tunnel mode. This is because
authenticity of the IP packet has nothing to do with IP addresses in
the IP header.
7. Conclusion
o There is a need for Mobile IPv6 and IPsec/IKE to interact with
each other to provide full support of IPsec security functions.
o An extension to the PF_KEY framework (PF_KEY MIGRATE message) is
proposed, which makes it possible for the IPsec/IKE to migrate an
endpoint address of tunnel IPsec SAs from one to another.
o PF_KEY MIGRATE messages also make it possible for IKE to survive
movements by updating its IKE session.
o In order for the IKE to perform key negotiations and rekeying,
effort should be made to keep its SPD image up-to-date.
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o The proposed mechanism was implemented on both Linux and BSD
platforms and confirmed to be working well.
o Currently, large portion of the proposed mechanism is
implementation dependent due to lack of standard interface to
access the SPD (PF_POLICY?).
8. References
8.1. Normative References
[RFC2367] McDonald, D., Metz, C., and B. Phan, "PF_KEY Key
Management API, Version 2", RFC 2367, July 1998.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC3776] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and
Home Agents", RFC 3776, June 2004.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
8.2. Informative References
[I-D.ietf-hip-mm]
Henderson, T., "End-Host Mobility and Multihoming with the
Host Identity Protocol", draft-ietf-hip-mm-05 (work in
progress), March 2007.
[I-D.ietf-mip6-nemo-v4traversal]
Soliman, H., "Mobile IPv6 support for dual stack Hosts and
Routers (DSMIPv6)", draft-ietf-mip6-nemo-v4traversal-06
(work in progress), November 2007.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, January 2005.
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[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
Appendix A. PF_KEY MIGRATE Message Format
The figure below shows the message format of PF_KEY MIGRATE. The
message consists of 6 parts (boundary of each part is marked with
">"). The message starts with PF_KEY base message header followed by
two address extensions. A pair of address extensions hold source and
destination address of the selector. Rest of the message are
specific to IPsec implementation on BSD. sadb_x_policy{} structure
holds additional information of security policy. The last part of
the message is a pair of sadb_x_ipsecrequest{} structures that hold
old and new SA information.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------+---------------+---------------+---------------+
| ...version | sadb_msg_type | sadb_msg_errno| ...msg_satype |
+---------------+---------------+---------------+---------------+
| sadb_msg_len | sadb_msg_reserved |
+---------------+---------------+---------------+---------------+
| sadb_msg_seq |
+---------------+---------------+---------------+---------------+
| sadb_msg_pid |
>+---------------+---------------+---------------+---------------+
| sadb_address_len | sadb_address_exttype |
+---------------+---------------+---------------+---------------+
| _address_proto| ..._prefixlen | sadb_address_reserved |
+---------------+---------------+---------------+---------------+
~ selector source address (64-bit aligned sockaddr) ~
>+---------------+---------------+---------------+---------------+
| sadb_address_len | sadb_address_exttype |
+---------------+---------------+---------------+---------------+
| _address_proto| ..._prefixlen | sadb_address_reserved |
+---------------+---------------+---------------+---------------+
~ selector destination address (64-bit aligned sockaddr) ~
>+---------------+---------------+---------------+---------------+
| sadb_x_policy_len | sadb_x_policy_exttype |
+---------------+---------------+---------------+---------------+
| sadb_x_policy_type | ..._dir | ..._reserved |
+---------------+---------------+---------------+---------------+
| sadb_x_policy_id |
+---------------+---------------+---------------+---------------+
| sadb_x_policy_priority |
>+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_len | sadb_x_ipsecrequest_proto |
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+---------------+---------------+---------------+---------------+
| ..._mode | ..._level | sadb_x_ipsecrequest_reserved1 |
+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_reqid |
+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_reserved2 |
+---------------+---------------+---------------+---------------+
~ old tunnel source address (64-bit aligned ... ~
+---------------+---------------+---------------+---------------+
~ old tunnel destination address ... pair of sockaddr) ~
>+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_len | sadb_x_ipsecrequest_proto |
+---------------+---------------+---------------+---------------+
| ..._mode | ..._level | sadb_x_ipsecrequest_reserved1 |
+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_reqid |
+---------------+---------------+---------------+---------------+
| sadb_x_ipsecrequest_reserved2 |
+---------------+---------------+---------------+---------------+
~ new tunnel source address (64-bit aligned ... ~
+---------------+---------------+---------------+---------------+
~ new tunnel destination address ... pair of sockaddr) ~
+---------------+---------------+---------------+---------------+
Following is a structure of PF_KEY base message header specified in
[RFC2367]. A new message type for PF_KEY MIGRATE (i.e.,
SADB_X_MIGRATE) should be specified in member sadb_msg_type.
struct sadb_msg {
uint8_t sadb_msg_version;
uint8_t sadb_msg_type;
uint8_t sadb_msg_errno;
uint8_t sadb_msg_satype;
uint16_t sadb_msg_len;
uint16_t sadb_msg_reserved;
uint32_t sadb_msg_seq;
uint32_t sadb_msg_pid;
};
Following is a structure of address extension header specified in
[RFC2367]. Upper layer protocol should be specified in member
sadb_address_proto.
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struct sadb_address {
uint16_t sadb_address_len;
uint16_t sadb_address_exttype;
uint8_t sadb_address_proto;
uint8_t sadb_address_prefixlen;
uint16_t sadb_address_reserved;
};
Following is a structure for holding attributes that are relevant to
security policy, which is available on BSD IPsec implementation.
Direction of the target security policy should be specified in member
sadb_x_policy_dir.
struct sadb_x_policy {
uint16_t sadb_x_policy_len;
uint16_t sadb_x_policy_exttype;
uint16_t sadb_x_policy_type;
uint8_t sadb_x_policy_dir;
uint8_t sadb_x_policy_reserved;
uint32_t sadb_x_policy_id;
uint32_t sadb_x_policy_priority;
};
Following is a structure for holding attributes that are relevant to
security association, which is available on BSD IPsec implementation.
IPsec protocol (ESP or AH) and mode (Tunnel) of the target security
association should be provided in member sadb_x_ipsecrequest_proto
and sadb_x_ipsecrequest_mode, respectively.
struct sadb_x_ipsecrequest {
uint16_t sadb_x_ipsecrequest_len;
uint16_t sadb_x_ipsecrequest_proto;
uint8_t sadb_x_ipsecrequest_mode;
uint8_t sadb_x_ipsecrequest_level;
uint16_t sadb_x_ipsecrequest_reserved1;
uint32_t sadb_x_ipsecrequest_reqid;
uint32_t sadb_x_ipsecrequest_reserved2;
};
Appendix B. Acknowledgements
The authors gratefully acknowledge the contribution of (in
alphabetical order): Arnaud Ebalard, Sebastien Decugis, Mitsuru
Kanda, Kazunori Miyazawa, Tsuyoshi Momose Shoichi Sakane, Keiichi
Shima, Noriaki Takamiya, and Hideaki Yoshifuji.
Support of NAT Traversal was suggested by Kazunori Miyazawa.
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Kazunori Miyazawa provided valuable comments on Packet Extension.
Arnaud Ebalard provided valuable comments on Packet Extension based
on his implementation experience.
This document was generated by xml2rfc.
Authors' Addresses
Shinta Sugimoto
Nippon Ericsson K.K.
Koraku Mori Building
1-4-14, Koraku, Bunkyo-ku
Tokyo 112-0004
Japan
Phone: +81 3 3830 2241
Email: shinta.sugimoto@ericsson.com
Francis Dupont
CELAR
Email: Francis.Dupont@fdupont.fr
Masahide Nakamura
Hitachi Communication Technologies, Ltd.
216 Totsuka-cho, Totsuka-ku
Yokohama 244-8567
Japan
Phone: +81 45 865 7003
Email: masahide.nakamura.cz@hitachi.com
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