Port Control Protocol (PCP) Authentication Mechanism
draft-wasserman-pcp-authentication-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Dacheng Zhang , Margaret Cullen , Sam Hartman | ||
| Last updated | 2011-10-31 (Latest revision 2011-10-24) | ||
| Replaced by | draft-ietf-pcp-authentication, RFC 7652 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-wasserman-pcp-authentication-01
Network Working Group M. Wasserman
Internet-Draft S. Hartman
Intended status: Experimental Painless Security
Expires: May 3, 2012 D. Zhang
Huawei
October 31, 2011
Port Control Protocol (PCP) Authentication Mechanism
draft-wasserman-pcp-authentication-01
Abstract
An IPv4 or IPv6 host can use the Port Control Protocol (PCP) to
flexibly manage the IP address and port mapping information on
Network Address Translators (NATs) or firewalls, to facilitate
communications with remote hosts. However, the un-controlled
generation or deletion of IP address mappings on such network devices
may cause security risks and should be avoided. In some cases the
client may need to prove that it is authorized to modify, create or
delete PCP mappings. This document proposes an in-band
authentication mechanism for PCP that can be used in those cases.
The Extensible Authentication Protocol (EAP) is used to perform
authentication between PCP devices.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 3, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Session Initiation . . . . . . . . . . . . . . . . . . . . 5
3.2. Session Termination . . . . . . . . . . . . . . . . . . . 7
3.3. Result Codes . . . . . . . . . . . . . . . . . . . . . . . 7
4. PA Security Association . . . . . . . . . . . . . . . . . . . 7
5. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Authentication OpCode Format . . . . . . . . . . . . . . . 8
5.2. Authentication Tag Option . . . . . . . . . . . . . . . . 9
5.3. EAP Payload Option . . . . . . . . . . . . . . . . . . . . 10
5.4. PRF Option . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5. Hash Algorithm Option . . . . . . . . . . . . . . . . . . 11
5.6. Session Lifetime Option . . . . . . . . . . . . . . . . . 11
6. Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Authentication Data Generation . . . . . . . . . . . . . . 11
6.2. Authentication Data Validation . . . . . . . . . . . . . . 12
6.3. Sequence Number . . . . . . . . . . . . . . . . . . . . . 12
6.4. Retransmission Policies . . . . . . . . . . . . . . . . . 13
6.5. MTU Considerations . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
10. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
Using the Port Control Protocol (PCP) [I-D.ietf-pcp-base], an IPv4 or
IPv6 host can flexibly manage the IP address mapping information on
its network address translators (NATs) and firewalls, and control
their policies in processing incoming and outgoing IP packets.
Because NATs and firewalls both play important roles in network
security architectures, there are many situations in which
authentication and access control are required to prevent un-
authorized users from accessing such devices. This document proposes
a PCP security extension which enables PCP servers to authenticate
the clients that they are communicating with using Extensible
Authentication Protocol (EAP). The following issues are considered
in the design of this extension:
o Loss of EAP messages during transportation
o Disordered delivery of EAP messages
o Generation of transport keys
o Integrity protection and data origin authentication for PCP
messages
o Algorithm agility
The mechanism described in this document meets the security
requirements to address the Advanced Threat Model described in the
base PCP specification [I-D.ietf-pcp-base]. This mechanism can be
used to securely use PCP in the following situations::
o On Security infrastructure equipment, such as corporate firewalls,
that does not create implicit mappings.
o On equipment (such as CGNs or service provider firewalls) that
serve multiple administrative domains and do not have a mechanism
to securely partition traffic from those domains.
o For any implementation that wants to be more permissive in
authorizing explicit mappings than it is in authorizing implicit
mappings.
o For implementations that support the THIRD_PARTY Option (unless
they can meet the constraints outlined in Section 14.1.2.2).
o For implementations that wish to support any deployment scenario
that does not meet the constraints described in Section 14.1.
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2. Terminology
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].
Most of the terms used in this document are introduced in
[I-D.ietf-pcp-base].
PCP Client (PCC): A PCP device (e.g., a host) which is responsible
for issuing PCP requests to a PCP server. In this document, a PCC is
also a EAP peer [RFC3748], and it is the responsibility of a PCC to
provide the credentials when authentication is required.
PCP Server (PCS): A PCP device (e.g., a NAT or a firewall) that
implements the server-side of the PCP protocol, via which PCCs
request and manage explicit mappings. In this document, a PCS is
integrated with an EAP authenticator [RFC3748]. Therefore, when
necessary, a PCS can verify the credentials provided by a PCC and
make an access control decision based on the authentication result.
PCP Authentication (PA) Session: A series of PCP message exchanges
transferred between a PCC and a PCS in order to perform
authentication, authorization, key distribution and secured PCP
communication. Each PA session is assigned a distinctive Session ID.
The PCP devices involved within a PA session are called session
partners. A typical PA session has two session partners.
PCP Security Association (PCP SA): A PCP security association is
formed between a PCC and a PCS by sharing cryptographic keying
material and associated context. The formed duplex security
association is used to protect the bidirectional PCP signaling
traffic between the PCC and PCS.
Session Lifetime: A duration associated with a PA session. For an
established PA session, the session lifetime is bound to the lifetime
of the current authorization decision given to the PCC. The session
lifetime can be extended by a new round of EAP authentication before
it expires. Until a PA session is established, the lifetime SHOULD
be set to a value that allows the PCC to detect a failed session in a
reasonable amount of time.
Master Session Key (MSK): A key derived by the partners of a PA
session, using a EAP key generating method specified in [RFC3748].
PA (PCP for Authentication) message: A PCP message containing an
Authentication OpCode for EAP authentication.
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3. Protocol Details
3.1. Session Initiation
To carry out an EAP authentication process between two PCP devices, a
set of PA messages need to be exchanged. Each PA message contains an
Authentication OpCode (and additional Options if needed). The
Authentication OpCode consists of four fields: Session ID, Flag, EAP
Type, and Sequence Number. The Session ID field is used to identify
the session which the message belongs to. The Flag field indicates
the type of the PCP message, while EAP Type is used to identify the
type of the attached EAP message. The sequence number field is used
to detect the disorder or the duplication occurred during packet
delivery.
The message exchanges conveyed within an PA session is introduced in
the remainder section.
When a PCC intends to initiate a PA session with a PCS, it sends a
PCC-Initiation message to the PCS. The Session ID and Sequence
Number fields of the OpCode in the PCC-Initiation are set as 0.
After receiving the PCC-Initiation, if the PCS would like to initiate
a PA session, it will reply with a PA-Request which contains an EAP
Identity Request. The Sequence Number field in the PA-Request is set
as 0, and the Session ID field MUST be filled with the identifier
assigned by the PCS for this session. Otherwise, the PCS discards
the message silently. If the PCC intends to simplify the
authentication process, it can append an EAP Identity Response
message within the PCC-Initiation request so as to skip over the step
of waiting for the EAP Identity Request and inform the PCS that it
would like to perform EAP authentication.
In the scenario where a PCS receives a PCP message other than a PCC-
Initiation from a PCC which needs to be authenticated, the PCS can
reply with a PA-Request to initiate a PA session; the result code
field of the PA-Request is set as AUTHENTICATION-REQUIRED. In
addition, the PCS MUST assign a session ID for the session and
transfer it within the initial PA-Request. In the PA messages
exchanged afterwards in this session, the session ID MUST be
appended. Therefore, in the subsequent communication, the PCC can
distinguish the messages in this session from those in other sessions
through the PCS IP address and the session ID. When the PCC receives
the initial PA-Request message from the PCS, it can reply with a PA-
Answer message to continue the session or silently discards the
request message according to its local policies.
In a PA session, PA-Request messages are sent from PCSs to PCCs while
PA-Answer messages are only sent from PCCs to PCSs. Correspondently,
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an EAP request messages MUST be transported within a PA-Request
message, and an EAP answer messages MUST be transported within a PA-
Answer message. Particularly, when a PCP device receives a PA-
Request or a PA-Answer message from its partner and cannot generate a
response within a pre-specified period due to certain reasons (e.g.,
waiting for human input to construct a EAP message), the PCP device
needs to reply with a PA-Acknowledge message to indicate that the
message has been received. Therefore, the partner does not have to
un-necessarily retransfer the PCP message.
In this work, it is mandated for a PCC and a PCS to perform a key-
generating EAP method in authentication, and so a successful EAP
authentication process will result in a MSK. If the PCC and the PCS
want to generate a traffic key using the MSK, they need to agree upon
a Pseudo-Random Function (PRF) for the transport key derivation and a
MAC algorithm to provide data origin authentication for subsequent
PCP signaling packets. On this occasion, the PCS needs to append the
initial PA-Request message with a set of PRF Options and MAC
Algorithm Options which contain the PRFs and the MAC (Message
Authentication Code) algorithms the PCS supports respectively. After
receiving the request, the PCC selects a PRF and a MAC algorithm
which it intends to support, and sends back a PA-Answer with a PRF
Option and a MAC Algorithm Option for the selected algorithms.
The last PA-Request message transported within a PA session carries
the EAP authentication and PCP authorization results. The last PA-
Request and PA-Answer messages MUST have their the 'C' (Complete) bit
set.
If the EAP authentication successes, the result code of the last PA-
Request is Authentication-Success. In this case, before sending out
the PA-Request, the PCS must derive a transport key and use it to
generate digests to protect the integrity and authenticity of the PA-
Request and any subsequent PCP message. Such digests are transported
within Authentication Tag Options. In addition, the PA-Request needs
to be appended with a Session Lifetime Option which indicates the
life time of the PA session (i.e., the life time of the MSK).
If the EAP authentication fails, the result code of the last PA-
Request is Authentication-Failed. If the EAP authentication
successes but Authorization fails, the result code of the last PA-
Request is Authorization-Failed. In the latter two cases, the PA
session MUST be terminated immediately after the last PCP
authentication message exchange.
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3.2. Session Termination
A PA session can be explicitly terminated by sending a termination-
indicating PA acknowledge message from either session partner. After
receiving a termination-indicating message from the session partner,
the other PCP device involved in the session MUST response with a
termination-indicating PA Acknowledge message and remove the PA SA
immediately. When the session partner initiating the termination
process receives the acknowledge message, it will remove the
associated PA SA immediately.
3.3. Result Codes
Following result codes are defined in the solution:
XXX AUTHENTICATION-REQUIRED
XXX AUTHENTICATION-FAILED
XXX AUTHENTICATION-SUCCESS
XXX AUTHORIZATION-FAILED
4. PA Security Association
At the beginning a PA session, a session SHOULD generate a PA SA to
maintain its state information during the session. A The parameters
of a PA SA is listed as follows:
o IP address and UDP port number of the PCC
o IP address and UDP port number of the PCS
o Session Identifier
o Sequence number for the next outgoing PCP message
o Sequence number for the next incoming PCP message
o Last transmitted message payload
o Retransmission interval
o MSK
o MAC algorithm: The algorithm that the transport key should use to
generate digests for PCP messages.
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o Pseudo-random function: The pseudo random function negotiated in
the initial PA-Request and PA-Answer exchange for the transport
key derivation
o Transport key: the key derived from the MSK to provide integrity
protection and data origin authentication for the messages in the
PA session. The life time of the transport key SHOULD be
identical to the life time of the session.
Particularly, the transport key is computed in the following way:
Transport key = prf(MSK, "IETF PCP"| Session_ID), where:
o The prf: The pseudo-random function assigned in the Pseudo-random
function parameter.
o MSK: The master session key generated by the EAP method.
o "IETF PCP": The ASCII code representation of the non-NULL
terminated string (excluding the double quotes around it).
o Session_ID: The ID of the session which the MSK is derived from
5. Packet Format
5.1. Authentication OpCode Format
The following figure illustrates the format of an authentication
Opcode:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | EAP Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: The Flags field is two octets. The following bits are
assigned:
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I C R A K T r r r r r r r r r r|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* I (Initiation): This bit is set in a PCC-Initiation message.
* C (Complete): If the message is the last PA-Request or PA-
Answer message in the session, this bit MUST be set. For other
messages, this bit MUST be cleared.
* R (Request): This bit is set in a PA-Request message.
* A (Answer): This bit is set in a PA-Answer message.
* K (acKnowledgement): This bit is set and only set in a PA-
Acknowledgement message.
* T (Termination): If this bit is set in a PA-Acknowledgement
message, the message is used for session-termination
indication.
Message Type: The Message Type field is two octets. This field is
used to indicate the type of the EAP message attached within the
message. Message Type allocation is managed by IANA [IANAWEB].
Session ID: This field contains a 32-bit PA session identifier.
Sequence Number: This field contains a 32-bit sequence number. In
this solution, a sequence number needs to be incremented on every
new (non-retransmission) outgoing packet in order to provide
ordering guarantee for PCP.
5.2. Authentication Tag Option
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Reserved | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Authentication Data (Variable) |
~ ~
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length: The length of the Authentication Tag Option (in
octet), including the 8 octet fixed header and the variable length
of the authentication data.
Session ID: A 32-bit field used to indicates the identifier of the
session that the message belongs to and identifies the secret key
used to create the message digest appended to the PCP message.
Authentication Data: A Variable length field that carries the
Message Authentication Code for the PCP packet. The generation of
the digest can be various according to the algorithms specified in
different PCP SAs.
5.3. EAP Payload Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Reserved | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| EAP Message |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
EAP Message: The EAP message transferred. Note this field MUST
end on a 32-bit boundary, padded with 0's when necessary.
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5.4. PRF Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Reserved | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PRF |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PRF: The pseudo-random Function which the sender supports to
generate a MSK.
5.5. Hash Algorithm Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Reserved | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MAC Algorithm: The MAC algorithm which the sender supports to
generate authentication data.
5.6. Session Lifetime Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Reserved | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Session Lifetime: The life period of the PA Session, which is decided
by the authorization result.
6. Processing Rules
6.1. Authentication Data Generation
If a PCP SA is generated as the result of an successful EAP
authentication process, every subsequent PCP message within the
session needs carry an Authentication Tag Option which contains the
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digest of the PCP message for data orgin authentication and integrity
protection.
Before generating a digest for a PCP message, a device needs to first
select a traffic key in the session and append the Authentication Tag
Option at the end of the protected PCP message. The length of the
Authentication Data field is decided by the MAC algorithm adopted in
the session. The device then fills the Session ID field and the PCP
SA ID field, and sets the Authentication Data field as 0. After
this, the device generates a digest for the PCP message with the MAC
algorithm and the selected traffic key, and input the generated
digest into the Authentication Data field.
6.2. Authentication Data Validation
When a device receives a PCP pacekt with an Authentication Tag
Option, it needs to use the session ID transported in the option to
locate the proper session ID, and then find out the associated
transport key and the MAC algorithm. After storing the value of the
Authentication field of the Authentication Tag Option, the device
fills the the Authentication field with zeros. Then, the device
generates a digest for the packet with the transport key and the MAC
algorithm found in the first step. If the value of the newly
generated digest is identical to the stored one, the device can
ensure that the packet has not been tampered during the
transportation. The validation successes. Otherwise, the packet
MUST be discarded.
6.3. Sequence Number
PCP adopts UDP to transport signaling messages. As an un-reliable
transporting protocol, UDP does not guarantee the ordered packet
delivery and does not provide any protection from packet loss. In
order to ensure the EAP messages are exchanged in a reliable way,
every PCP packet exchanged during EAP authentication must carries an
monotonically increased sequence number. During a PA session, a PCP
device needs to maintain two sequence numbers, one for incoming
packets and one for outgoing packets. When generating an outgoing
PCP packet, the device attaches the outgoing sequence number to the
packet. If the outgoing packet, the device then increments the
sequence number by 1. When receiving a PCP packet from its session
partner, the device will not accept it if the sequence number carried
in the packet matches the incoming sequence number the device
maintains. After confirming that the received packet is valid, the
device increments the incoming sequence number by 1. However, the
above rules are not applied to PA-Acknowledgement messages. When
receiving or sending out a PA-Acknowledgement message, the device
MUST not inicrease the correspondent sequence number. Another
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exception is message retransmission. When a device does not receive
any response message from its session partner in a certain period, it
needs to retransmit the last sent message with a limited rate. The
value of the sequence number in the duplicate messages MUST be
identical to that of the original message. When the device receives
such duplicate messages from its session partner, it MUST tries to
answer them by sending the last outgoing message within a limited
rate unless it has received another valid message with a larger
sequence number from its session. Note that in these cases the
outgoing sequence number will not be affected by the message
retransmission.
6.4. Retransmission Policies
This work provides a retransmission mechanism for reliable PA message
delivery. The timer, the variables, and the rules used in this
mechanism is mostly brought from PANA[RFC5191].
The retransmission behavior is controlled and described by the
following variables:
RT: Retransmission timeout from the previous (re)transmission
IRT: Base value for RT for the initial retransmission
MRC: Maximum retransmission count
MRT: Maximum retransmiting time interval
RAND: Randomization factor
With each message transmission or retransmission, the sender sets RT
according to the rules given below.
If RT expires before receiving any reply, the sender re-calculates RT
and retransmits the message. Each of the computations of a new RT
include a randomization factor (RAND), which is a random number
chosen with a uniform distribution between -0.1 and +0.1. The
randomization factor is included to minimize the synchronization of
messages. The algorithm for choosing a random number does not need
to be cryptographically sound. The algorithm SHOULD produce a
different sequence of random numbers from each invocation. RT for
the first message retransmission is based on IRT:
RT = IRT
RT for each subsequent message retransmission is based on the
previous value of RT (RTprev):
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RT = (2+RAND) * RTprev
MRT specifies an upper bound on the value of RT (disregarding the
randomization added by the use of RAND). If MRT has a value of 0,
there is no upper limit on the value of RT. Otherwise:
if (RT > MRT)
RT = (1+RAND) * MRT
MRC specifies an upper bound on the number of times a sender may
retransmit a message. Unless MRC is zero, the message exchange fails
once the sender has transmitted the message MRC times. In this case,
the sender needs to start a session termination process illustrated
in Section 3.2.
6.5. MTU Considerations
TBD
7. IANA Considerations
TBD
8. Security Considerations
In this work, a successful EAP authentication process performed
between two PCP devices will result in the generation of a MSK which
can be used to derive the transport keys to generate MAC digests for
subsequent PCP message exchanges. This work does not exclude the
possibility of using the MSK to generate keys for different security
protocols to enable per-packet cryptographic protection. The methods
of deriving the transport key for the security protocols is out of
scope of this document.
However, before a transport key has been generated, the PA messages
exchanged within a PA session have little cryptographic protection,
and if there is no already established security channel between two
session partners, these messages are subject to man-in-the-middle
attacks and DOS attacks. For instance, the initial PA-Request and
PA-Answer exchange is vulnerable to spoofing attacks as these
messages are not authenticated and integrity protected. In order to
prevent very basic DOS attacks, a PCP device SHOULD generate state
information as little as possible in the initial PA-Request and PA-
Answer exchanges. The choice of EAP method is also very important.
The selected EAP method must be resilient to the attacks possibly
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occurred in a insecure network environment, and the user-identity
confidentiality, protection against dictionary attacks, and session-
key establishment must be supported
9. Acknowledgements
This document was written using the xml2rfc tool described in RFC
2629 [RFC2629].
Some of the ideas in this document were adopted from PANA[RFC5191].
10. Change Log
10.1. Changes from -00 to -01
o Editorial changes, added use cases to introduction.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)",
draft-ietf-pcp-base-16 (work in progress), October 2011.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
Yegin, "Protocol for Carrying Authentication for Network
Access (PANA)", RFC 5191, May 2008.
Wasserman, et al. Expires May 3, 2012 [Page 15]
Internet-Draft PCP Authentication October 2011
Authors' Addresses
Margaret Wasserman
Painless Security
356 Abbott Street
North Andover, MA 01845
USA
Phone: +1 781 405 7464
Email: mrw@painless-security.com
URI: http://www.painless-security.com
Sam Hartman
Painless Security
356 Abbott Street
North Andover, MA 01845
USA
Email: hartmans@painless-security.com
URI: http://www.painless-security.com
Dacheng Zhang
Huawei
Beijing,
China
Phone:
Fax:
Email: zhangdacheng@huawei.com
URI:
Wasserman, et al. Expires May 3, 2012 [Page 16]