Type 40 (not skippable) (see [1] and section 8)
Subtype A number assigned to identify the way in which the
MN-FA Key Generation Nonce Request Subtype Data is
to be used when generating the registration key.
Length The 16-bit Length field indicates the length of the
extension. It is equal to the number of bytes in
the MN-FA Key Generation Nonce Request Subtype Data
plus 4 (for the Mobile Node SPI field).
Mobile Node SPI The Security Parameters Index that the mobile node
will assign for the Mobility Security Association
created for use with the registration key.
MN-FA Key Generation Nonce Request Subtype Data
Data needed to carry out the creation of the
registration key on behalf of the mobile node.
The MN-FA KeyGen Request defines a set of extensions, identified by
subtype, which may be used by a mobile node in a Mobile IP
Registration Request message to request that some other entity create
a Registration Key for use by the mobile node with the mobile node’s
new foreign agent.
This document defines the subtype 1 for the MN-FA Key Generation
Nonce >From AAA Request (MN-FA AAA KeyGen Request for short). The
MN-FA AAA KeyGen Request has a zero-length Subtype Data field and
MUST appear in the Registration Request before the MN-AAA
Authentication extension.
6.2. Generalized MN-FA Key Generation Nonce Reply Extension
The Generalized MN-FA Key Generation Nonce Reply extension (MN-FA
KeyGen Reply for short) supplies keying material requested by the
MN-FA KeyGen Request extension. Figure 2 illustrates the format of
the Generalized MN-FA Key Generation Nonce Reply Extension.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Subtype | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MN-FA Key Generation Nonce Reply Subtype Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The Generalized Mobile IP MN-FA Key
Generation Nonce Reply Extension
Type 41 (not skippable) (see [1] and section 8)
Subtype A number assigned to identify the way in which the MN-FA
Key Generation Nonce Reply Subtype Data is to be used to
obtain the registration key.
Length The 16-bit Length field is equal to the number of bytes in
the MN-FA Key Generation Nonce Reply Subtype Data.
MN-FA Key Generation Nonce Reply Subtype Data
An encoded copy of the keying material, along with any
other information needed by the recipient to create the
designated Mobility Security Association.
For each subtype, the format of the MN-FA Key Generation Nonce Reply
Subtype Data has to be separately defined according to the particular
method required to set up the Mobility Security Association.
For the subtype defined in this document, the MN-FA Key Generation
Nonce supplied in the data for a subtype of this extension may come
as a result of a request which was sent using a subtype of the
Generalized MN-FA Key Generation Nonce Request Extension. In such
cases, the SPI to be used when employing the Mobility Security
Association defined by the registration key is the same as given in
the original request.
Once the mobile node creates the Mobility Security Association with
the foreign agent, by using the transform indexed by the AAA SPI, it
stores that Mobility Security Association indexed by the FA SPI in
its list of Mobile Security Associations.
If the foreign agent receives a Registration Reply that has no MN-FA
Key Generation Nonce Reply extension, and if it has no existing
Mobility Security Association with the mobile node, the foreign agent
MAY change the Code value of the Registration Reply to MISSING_MN_FA
(see section 7), effectively causing the registration to fail.
This document defines subtype 1 of the MN-FA KeyGen Reply for the
MN-FA Key Generation Nonce From AAA extension (MN-FA AAA KeyGen Reply
for short), shown in figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AAA SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FA SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm Identifier | Key Generation Nonce ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The MN-FA Key Generation Nonce From AAA
Subtype-Specific Data
lifetime This field indicates the duration of time (in seconds) for
which the keying material used to create the registration
key is valid.
AAA SPI A 32-bit opaque value, indicating the SPI that the mobile
node must use to determine the transform to use for
establishing the Mobility Security Association between the
mobile node and its prospective foreign agent.
FA SPI The SPI for the Mobility Security Association to the FA
that the mobile node creates using the Key Generation
Nonce.
Algorithm Identifier
This field indicates the transform to be used (stored as
part of the Mobility Security Association with the foreign
agent, and selected from among the values in the
"Authentication Algorithm" table cited in section 4), for
future computations of the Mobile-Foreign Authentication
Extension.
Key Generation Nonce
A random [7] value of at least 128 bits.
The MN-FA AAA KeyGen Reply extension MUST appear in the Registration
Reply before the Mobile-Foreign Authentication extension.
The Key Generation Nonce is provided by the AAA server for use by the
mobile node in creating the registration key, which is used to secure
future Mobile IP registrations with the same foreign agent.
6.3. Generalized MN-HA Key Generation Nonce Request Extension
Figure 4 illustrates the Generalized MN-HA Key Generation Nonce
Request Extension (MN-HA KeyGen Request for short).
Type 42 (not skippable) (see [1] and section 8)
Subtype a number assigned to identify the way in which the
MN-HA Key Generation Nonce Request Subtype Data is
to be used when generating the registration key.
Length The 16-bit Length field indicates the length of the
extension. It is equal to the number of bytes in
the MN-HA Key Generation Nonce Request.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Subtype | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mobile Node SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MN-HA Key Generation Nonce Request Subtype Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: The Generalized Mobile IP MN-HA Key Generation
Nonce Request Extension
Subtype Data plus 4 (for the Mobile Node SPI field).
Mobile Node SPI The Security Parameters Index that the mobile node
will assign for the Mobility Security Association
created for use with the registration key.
MN-HA Key Generation Nonce Request Subtype Data
Data needed to carry out the creation of the MN-HA
key on behalf of the mobile node.
The MN-HA KeyGen Request Extension defines a set of extensions,
identified by subtype, which may be used by a mobile node in a Mobile
IP Registration Request message to request that some other entity
create an MN-HA key for use by the mobile node with the mobile node’s
new home agent.
This document defines the subtype 1 for the MN-HA Key Generation
Nonce from AAA Request (MN-HA AAA KeyGen Request for short). The
MN-HA AAA KeyGen Request has a zero-length Subtype Data field and
MUST appear in the Registration Request before the MN-AAA
Authentication extension.
6.4. Generalized MN-HA Key Generation Nonce Reply Extension
The Generalized MN-HA Key Generation Nonce Reply extension (MN-HA
KeyGen Reply for short) supplies keying material requested by the
MN-HA KeyGen Request extension. Figure 5 illustrates the format of
the Generalized MN-HA Key Generation Nonce Reply Extension.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Subtype | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MN-HA Key Generation Nonce Reply Subtype Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: The Generalized Mobile IP MN-HA Key
Generation Nonce Reply Extension
Type 43 (not skippable) (see [1] and section 8)
Subtype a number assigned to identify the way in which the MN-HA
Key Generation Nonce Reply Subtype Data is to be used to
obtain the MN-HA key.
Length The 16-bit Length field indicates the length of the
extension. It is equal to the number of bytes in the MN-
HA Key Generation Nonce Reply Subtype Data plus 4 (for the
Lifetime field).
Lifetime This field indicates the duration of time (in seconds) for
which the MN-HA key is valid.
MN-HA Key Generation Nonce Reply Subtype Data
Data used to derive the MN-HA key, along with any other
information needed by the mobile node to create the
designated Mobility Security Association with the home
agent.
For each subtype, the format of the MN-HA Key Generation Nonce Reply
Subtype Data has to be separately defined according to the particular
method required to set up the Mobility Security Association.
This document defines subtype 1 of the MN-HA KeyGen Reply for the
MN-HA Key Generation Nonce From AAA extension (MN-HA AAA KeyGen Reply
for short), shown in figure 6.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AAA SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HA SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm Identifier | Replay Method |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Generation Nonce ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: The MN-HA Key Generation Nonce From AAA
Subtype-Specific Data
AAA SPI A 32-bit opaque value, indicating the SPI that the mobile
node must use to determine the transform to use for
establishing the Mobility Security Association between the
mobile node and its home agent.
HA SPI The SPI for the Mobility Security Association to the HA
that the mobile node creates using the Key Generation
Nonce.
Algorithm Identifier
This field indicates the transform to be used for future
computations of the Mobile-Home Authentication Extension
(see section 4).
Replay Method
This field contains the replay method to be used for
future Registration messages (see section 4).
Key Generation Nonce
A random [7] value of at least 128 bits.
The MN-HA AAA KeyGen Reply subtype-specific data is shown in figure
6. The Mobile Node calculates the MN-HA key using the Key Generation
Nonce provided by the AAA server. The calculation proceeds by using
the key shared between the mobile node and the AAA server that has
previously been configured for securing all such communication
requirements with the AAA server which will be contacted within the
AAA infrastructure (see appendix A). The MN-HA key is intended for
use by the mobile node to secure future Mobile IP registrations with
its home agent. The MN-HA AAA KeyGen Reply extension MUST appear in
the Registration Reply before the MN-HA Authentication extension.
Once the mobile node creates the MN-HA Key, by using the transform
specified in the AAA SPI, it stores the HA Security Information
indexed by the HA SPI in its list of Mobile Security Associations.
The mobile node uses the Identification field data from the
Registration Reply as its initial synchronization data with the home
agent.
7. Error Values
Each entry in the following table contains the name of the Code [1]
value to be returned in a Registration Reply, the value for that
Code, and the section in which the error is first mentioned in this
specification.
Error Name Value Section
---------------------- ----- ---------
MISSING_MN_FA 107 6.2
8. IANA Considerations
This document defines 4 new extensions (see Section 6) taken from the
(non-skippable) numbering space defined for Mobile IP registration
extensions defined in RFC 3344 [1] as extended in RFC 2356 [8]. The
values for these extensions are:
Name Value Section
--------------------- ------- ---------
MN-FA-KeyGen Request 40 6.1
MN-FA-KeyGen Reply 41 6.2
MN-HA-KeyGen Request 42 6.3
MN-HA-KeyGen Reply 43 6.4
IANA has created and will maintain a new registry for the KeyGen
Request/Reply subtypes. The initial contents of the registry is a
single entry for the subtypes defined in this document:
Name Value Section
----------------------------- ------- ---------
KeyGen Request/Reply from AAA 1 6
New subtypes for these two registries are assigned through Standards
Action as defined in [9].
IANA has assigned a code value for error MISSING_MN_FA, listed in
section 7. This value has been taken from the space of error values
conventionally associated with rejection by the foreign agent (i.e.,
64-127).
IANA has created and will maintain a namespace for the Replay Method
Identifier. This specification makes use of 2 and 3; all other
values other than zero (0) and (1) are available for assignment,
pending review and approval by a Designated Expert [9].
9. Security Considerations
The extensions in this document are intended to provide the
appropriate level of security for Mobile IP entities (mobile node,
foreign agent, and home agent) to calculate the Authentication Data
needed by authentication extensions used with Mobile IP registration
messages. The Mobility Security Associations resulting from use of
these extensions do not offer any higher level of security than what
is already implicit in use of the AAA Security Association between
the mobile node and the AAAH. In order to deny any adversary the
luxury of unbounded time to analyze and break the secrecy of the AAA
Security Association between the mobile node and the AAA server, that
AAA Security Association MUST be refreshed periodically.
The provisioning and refreshing of the AAA key in the MN and AAA
server is outside the scope of this document.
Since the Reply extensions defined in this specification only carry
Key Generation Nonces, which are used to derive keys, they do not
expose any data that could be used in an attack aimed at recovering
the key shared between the mobile node and the AAA. The authors do
not believe this specification introduces any new security
vulnerability.
10. Acknowledgements
Thanks to Fredrik Johansson, Tom Hiller, and the members of the IESG
for their useful comments. Thanks especially to Tom Hiller who has
contributed many textual improvements to later revisions of this
document.
11. References
11.1. Normative References
[1] Perkins, C., Ed., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[2] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC
2486, January 1999.
[3] Perkins, C. and P. Calhoun, "Mobile IPv4 Challenge/Response
Extension", RFC 3012, November 2000.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] Calhoun, P. and C. Perkins, "Mobile IP Network Access Identifier
Extension for IPv4", RFC 2794, March 2000.
[6] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997.
[7] Eastlake, D., Crocker, S., and J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
[8] Montenegro, G. and V. Gupta, "Sun’s SKIP Firewall Traversal for
Mobile IP", RFC 2356, June 1998.
[9] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
11.2. Informative References
[10] Mitton, D., St.Johns, M., Barkley, S., Nelson, D., Patil, B.,
Stevens, M., and B. Wolff, "Authentication, Authorization, and
Accounting: Protocol Evaluation", RFC 3127, June 2001.
[11] Rigney, C., Willens, S., Rubens, A., and A. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865, June
2000.
[12] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko,
"Diameter Base Protocol", RFC 3588, September 2003.
[13] Glass, S., Hiller, T., Jacobs, S., and C. Perkins, "Mobile IP
Authentication, Authorization, and Accounting Requirements", RFC
2977, October 2000.
[14] Calhoun, P. and C. Perkins, "DIAMETER mobile IP extensions",
Work in Progress, February 2004.
Appendix A. AAA Infrastructure
In this appendix, we attempt to capture the main features of a basic
model for operation of AAA servers that is assumed for understanding
of the use of the Mobile IP registration extensions described in this
document. This information has been adapted from the discussion in
RFC 2977 [13].
Within the Internet, a mobile node belonging to one administrative
domain (called the home domain) often needs to use resources provided
by another administrative domain (called the foreign domain). A
foreign agent that handles the mobile node’s Registration Request is
likely to require that the mobile node provide some credentials that
can be authenticated before access to the resources is permitted.
These credentials may be provided as part of the Mobile-AAA
Authentication extension [3], relying on the existence of an AAA
infrastructure such as is described in this section, and also
described in RFC 2977 and RFC 3012 [3]. Such credentials are
typically managed by entities within the mobile node’s home domain.
They may be also used for setting up secure communications with the
mobile node and the foreign agent, or between the mobile node and its
home agent if necessary.
Local Domain Home Domain
+--------------+ +----------------------+
| +------+ | | +------+ |
| | | | | | | |