One document matched: draft-ietf-pcp-authentication-02.xml
<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY rfc2629 PUBLIC "" "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2629.xml">
]>
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="exp" docName="draft-ietf-pcp-authentication-02"
ipr="trust200902">
<front>
<title abbrev="PCP Authentication">Port Control Protocol (PCP)
Authentication Mechanism</title>
<author fullname="Margaret Wasserman" initials="M." surname="Wasserman">
<organization>Painless Security</organization>
<address>
<postal>
<street>356 Abbott Street</street>
<city>North Andover</city>
<region>MA</region>
<code>01845</code>
<country>USA</country>
</postal>
<phone>+1 781 405 7464</phone>
<email>mrw@painless-security.com</email>
<uri>http://www.painless-security.com</uri>
</address>
</author>
<author fullname="Sam Hartman" initials="S." surname="Hartman">
<organization>Painless Security</organization>
<address>
<postal>
<street>356 Abbott Street</street>
<city>North Andover</city>
<region>MA</region>
<code>01845</code>
<country>USA</country>
</postal>
<email>hartmans@painless-security.com</email>
<uri>http://www.painless-security.com</uri>
</address>
</author>
<author fullname="Dacheng Zhang" initials="D." surname="Zhang">
<organization>Huawei</organization>
<address>
<postal>
<street/>
<city>Beijing</city>
<region/>
<code/>
<country>China</country>
</postal>
<phone/>
<facsimile/>
<email>zhangdacheng@huawei.com</email>
<uri/>
</address>
</author>
<date day="2" month="October" year="2013"/>
<abstract>
<t>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.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Using the Port Control Protocol (PCP) <xref target="RFC6887"/>, 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 their clients with Extensible
Authentication Protocol (EAP). The EAP messages are encapsulated within
PCP packets during transportation.</t>
<t>The following issues are considered in the design of this
extension:</t>
<t><list style="symbols">
<t>Loss of EAP messages during transportation</t>
<t>Disordered delivery of EAP messages</t>
<t>Generation of transport keys</t>
<t>Integrity protection and data origin authentication for PCP
messages</t>
<t>Algorithm agility</t>
</list>The mechanism described in this document meets the security
requirements to address the Advanced Threat Model described in the base
PCP specification <xref target="RFC6887"/>. This mechanism can be used
to secure PCP in the following situations::</t>
<t><list style="symbols">
<t>On security infrastructure equipment, such as corporate
firewalls, that does not create implicit mappings.</t>
<t>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.</t>
<t>For any implementation that wants to be more permissive in
authorizing explicit mappings than it is in authorizing implicit
mappings.</t>
<t>For implementations that support the THIRD_PARTY Option (unless
they can meet the constraints outlined in Section 14.1.2.2).</t>
<t>For implementations that wish to support any deployment scenario
that does not meet the constraints described in Section 14.1.</t>
</list></t>
</section>
<section title="Terminology ">
<t>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 <xref
target="RFC2119"/>.</t>
<t>Most of the terms used in this document are introduced in <xref
target="RFC6887"/>.</t>
<t>PCP Client: A PCP device (e.g., a host) which is responsible for
issuing PCP requests to a PCP server. In this document, a PCP client is
also a EAP peer <xref target="RFC3748"/>, and it is the responsibility
of a PCP client to provide the credentials when authentication is
required.</t>
<t>PCP Server: A PCP device (e.g., a NAT or a firewall) that implements
the server-side of the PCP protocol, via which PCP clients request and
manage explicit mappings. In this document, a PCP server is integrated
with an EAP authenticator <xref target="RFC3748"/>. Therefore, when
necessary, a PCP server can verify the credentials provided by a PCP
client and make an access control decision based on the authentication
result. </t>
<t>PCP Authentication (PCP Auth) Session: A series of PCP message
exchanges transferred between a PCP client and a PCP server. The PCP
message involved within a session includes the PCP Auth messages used to
perform authentication, key distribution and session management, and the
common PCP messages secured with the distributed keys. Each PCP Auth
session is assigned a distinctive Session ID.</t>
<t>Session Partner: A PCP device involved within a PCP Auth session.
Each PCP Auth session has two session partners (a PCP server and a PCP
client).</t>
<t>Session Lifetime: The life period associated with a PCP Auth session,
which decides the lifetime of the current authorization given to the PCP
client.</t>
<t>PCP Security Association (PCP SA): A PCP security association is
formed between a PCP client and a PCP server by sharing cryptographic
keying material and associated context. The formed duplex security
association is used to protect the bidirectional PCP signaling traffic
between the PCP client and PCP server.</t>
<t>Master Session Key (MSK): A key derived by the partners of a PCP Auth
session, using an EAP key generating method (e.g., the one defined in
<xref target="RFC5448"/>).</t>
<t>PCP Authentication (PCP Auth) message: A PCP message containing an
Authentication OpCode. Particularly, a PCP Auth message sent from a PCP
server to a PCP client is referred to as a PCP-Auth-Request, while PCP
Auth message sent from a PCP client to a PCP server is referred to as a
PCP-Auth-Answer. Therefore, a PCP-Auth-Request is actually a PCP
response message specified <xref target="RFC6887"/>, and a
PCP-Auth-Answer is a PCP request message.</t>
<t>Common PCP message: A PCP message which does not contain an
Authentication OpCode. This document specifies an authentication option
to provide integrity protection and message origin authentication for
the common PCP messages.</t>
</section>
<section title="Protocol Details">
<section anchor="initiation" title="Session Initiation">
<t>At be beginning of a PCP Auth Session, a set of PCP Auth messages
need to be exchanged between two PCP devices in order to carry out an
EAP authentication process. Each PCP Auth message is attached with an
Authentication OpCode and may optionally contain the Options for
various purposes (e.g., transporting authentication messages and
session managements). The Authentication OpCode consists of two
fields: Session ID, and Sequence Number. The Session ID field is used
to identify the session to which the message belongs. The sequence
number field is used to detect the disorder or the duplication
occurred during packet delivery.</t>
<t>When a PCP client intends to proactively initiate a PCP Auth
session with a PCP server, it sends a PCP-Auth-Initiation message (a
PCP-Auth-Answer message with the result code "INITIATION") to the PCP
server. In the message, the Session ID and Sequence Number fields of
the Authentication OpCode are set as 0. The PCP client MAY also append
a nonce option which consists of a random nonce with
PCP-Auth-Initiation message. After receiving the PCP-Auth-Initiation,
if the PCP server would like to initiate a PCP Auth session, it will
reply with a PCP-Auth-Request which contains an EAP Identity Request.
The Sequence Number field in the PCP-Auth-Request is set as 0, and the
Session ID field MUST be filled with the session identifier assigned
by the PCP server for this session. If there is a nonce option in the
received PCP-Auth-Initiation message, the PCP-Auth-Request MUST be
attached with a nonce option which contains the nonce value learned
from the PCP client. The nonce will then be used by the PCP client to
check the freshness of the PCP-Auth-Request from the PCP server. From
now on, every PCP Auth message within this session will use this
session identifier to distinguish itself from the messages not
belonging to the session. When receiving a PCP Auth message from an
unknown session, a PCP device MUST discard the message silently. If
the PCP client intends to simplify the authentication process, it can
append an EAP Identity Response message within the PCP-Auth-Initiation
message so as to inform the PCP server that it would like to perform
EAP authentication and skip the step of waiting for the EAP Identity
Request.</t>
<t>In the scenario where a PCP server receives a common PCP request
message from a PCP client which needs to be authenticated, the PCP
server can reply with a PCP-Auth-Request to initiate a PCP Auth
session; the result code field of the PCP-Auth-Request is set as
AUTHENTICATION-REQUIRED. In addition, the PCP server MUST assign a
session ID for the session and transfer it within the
PCP-Auth-Request. The Sequence Number field in the PCP-Auth-Request is
set as 0. In the PCP Auth messages exchanged afterwards in this
session, the session ID MUST be used in order to help session partners
distinguish the messages within this session from those not within.
When the PCP client receives this initial PCP-Auth-Request message
from the PCP server, it can reply with a PCP-Auth-Answer message or
silently discard the request message according to its local policies.
In the PCP-Auth-Answer message, the PCP client MAY append a nonce
option which consists of a random nonce with PCP-Auth-Initiation
message. If so, in the next PCP-Auth-Request message, the PCP sever
MUST forward the nonce back within a nonce option.</t>
<t>In a PCP Auth session, PCP-Auth-Request messages are sent from PCP
servers to PCP clients while PCP-Auth-Answer messages are only sent
from PCP clients to PCP servers. Correspondently, an EAP request
message MUST be transported within a PCP-Auth-Request message, and an
EAP answer message MUST be transported within a PCP-Auth-Answer
message. When a PCP device receives a PCP-Auth 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 MAY reply with a PCP-Auth-Acknowledge
message (a PCP-Auth message with the result code
"PACKET-RECEIVED-ACK") to notify the packet has been received, and
thus un-necessarily retransmission of the PCP Auth message can be
avoided.</t>
<t>In this approach, it is mandated for a PCP client and a PCP server
to perform a key-generating EAP method in authentication. Therefore,
after a successful authentication procedure, a Master Session Key
(MSK) will be generated. If the PCP client and the PCP server 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
packets. On this occasion, the PCP server needs to append the initial
PCP-Auth-Request message with a set of PRF Options and MAC Algorithm
Options. Each PRF Option contains a PRF that the PCP server supports,
and each MAC Algorithm Option contains a MAC (Message Authentication
Code) algorithm that the PCP server supports. After receiving the
request, the PCP client selects a PRF and a MAC algorithm which it
would like to use, and sends back a PCP-Auth-Answer with a PRF Option
and a MAC Algorithm Option for the selected algorithm.</t>
<t>The last PCP-Auth-Request message transported within a PCP Auth
session carries the EAP authentication and PCP authorization results.
If the EAP authentication succeeds, the result code of the last
PCP-Auth-Request is AUTHENTICATION-SUCCEED. In this case, before
sending out the PCP-Auth-Request, the PCP server must derive a
transport key and use it to generate digests to protect the integrity
and authenticity of the PCP-Auth-Request. Such digests are transported
within Authentication Tag Options. In addition, the PCP-Auth-Request
may need to be appended with a Session Lifetime Option which includes
the life-time of the PCP Auth session (i.e., the life-time of the
MSK). If the PCP client also authenticate the PCP server, the PCP
client then generates the PCP SA and uses the derived traffic key to
secure the packet receiving acknowledgement. From then on, all the PCP
messages within the session are secured with the traffic key and the
MAC algorithm sepcified in the PCP SA, unless re-authentication is
performed. If the EAP authentication fails, the result code of the
last PCP-Auth-Request is AUTHENTICATION-FAILED. If the EAP
authentication succeeds but Authorization fails, the result code of
the last PCP-Auth-Request is AUTHORIZATION-FAILED. In the latter two
cases, the PCP Auth session MUST be terminated immediately after the
last PCP authentication message exchange. </t>
</section>
<section anchor="termination" title="Session Termination">
<t>A PCP Auth session can be explicitly terminated by sending a
termination-indicating PCP Auth message (a PCP Auth message with a
result code "SESSION-TERMINATION" ) from either session partner. After
receiving a termination-indicating message from the session partner, a
PCP device MUST respond with a termination-indicating PCP Auth message
and remove the PCP Auth SA immediately. When the session partner
initiating the termination process receives the acknowledge message,
it will remove the associated PCP Auth SA immediately.</t>
</section>
<section title="Session Re-Authentication">
<t>A session partner may select to perform EAP re-authentication if it
would like to update the PCP SA (e.g., update the MSK, or extend the
session life period) instead of initiating a new PCP Auth session.</t>
<t>When the PCP server initiates re-authentication, it sends a
PCP-Auth-Request message containing the EAP message for
re-authentication to the PCP client. The result code of the
PCP-Auth-Request message is set to "RE-AUTHENTICATION", which
indicates the message is for an re-authentication process. If the PCP
client would like to start the re-authentication, it will send an
PCP-Auth-Answer message containing the EAP message for
re-authentication to the PCP server, The result code of the
PCP-Auth-Answer message is set to "RE-AUTHENTICATION". Then, the
session partners exchange PCP Auth messages to transfer EAP messages
for the re-authentication. During the re-authentication procedure, the
session partners protect the integrity of PCP Auth messages with the
key and MAC algorithm specified in the current PCP SA; the sequence
numbers associated with the packet will never be rolled back and keep
increasing according to Section 6.3.</t>
<t>If the EAP re-authentication succeeds, the result code of the last
PCP-Auth-Request is "AUTHENTICATION-SUCCEED". In this case, before
sending out the PCP-Auth-Request, the PCP server must update the SA
and use the new key to generate digests to protect the integrity and
authenticity of the PCP-Auth-Request and any subsequent PCP message.
In addition, the PCP-Auth-Request MAY be appended with a Session
Lifetime Option which indicates the new life-time of the PCP Auth
session.</t>
<t>If the EAP authentication fails, the result code of the last
PCP-Auth-Request is "AUTHENTICATION-FAILED". If the EAP authentication
succeeds but Authorization fails, the result code of the last
PCP-Auth-Request is "AUTHORIZATION-FAILED". In the latter two cases,
the PCP Auth session MUST be terminated immediately after the last PCP
authentication message exchange.</t>
</section>
</section>
<section title="PA Security Association">
<t>At the beginning of a PCP Auth session, a session SHOULD generate a
PCP Auth SA to maintain its state information during the session. The
parameters of a PCP Auth SA are listed as follows:</t>
<t><list style="symbols">
<t>IP address and UDP port number of the PCP client</t>
<t>IP address and UDP port number of the PCP server</t>
<t>Session Identifier</t>
<t>Sequence number for the next outgoing PCP message</t>
<t>Sequence number for the next incoming PCP message</t>
<t>Last outgoing message payload</t>
<t>Retransmission interval</t>
<t>MSK: The master session key generated by the EAP method.</t>
<t>MAC algorithm: The algorithm that the transport key should use to
generate digests for PCP messages.</t>
<t>Pseudo-random function: The pseudo random function negotiated in
the initial PCP-Auth-Request and PCP-Auth-Answer exchange for the
transport key derivation</t>
<t>Transport key: the key derived from the MSK to provide integrity
protection and data origin authentication for the messages in the
PCP Auth session. The life-time of the transport key SHOULD be
identical to the life-time of the session.</t>
<t>The nonce selected by the PCP client at the initiation of the
session.</t>
<t>Key ID: the ID associated with Transport key.</t>
</list></t>
<t>Particularly, the transport key is computed in the following way:
Transport key = prf(MSK, "IETF PCP"| Session_ID| Nonce| key ID),
where:</t>
<t><list style="symbols">
<t>The prf: The pseudo-random function assigned in the Pseudo-random
function parameter.</t>
<t>MSK: The master session key generated by the EAP method.</t>
<t>"IETF PCP": The ASCII code representation of the non-NULL
terminated string (excluding the double quotes around it).</t>
<t>Session_ID: The ID of the session which the MSK is derived
from.</t>
<t>Nonce: The nonce selected by the client and transported in the
Initial PCP-Auth-Answer packet. If the PCP client does not select
one, this value is set as 0.</t>
<t>Key ID: The ID assigned for the traffic key.</t>
</list></t>
</section>
<section title="Result Code">
<t>This message use the result code field specified in the PCP headers
to transport the information for authentication and session management.
Particularly, the values of following result codes are specified.</t>
<t><list style="empty">
<t>TBD INITIATION </t>
<t>TBD PACKET-RECEIVED-ACK </t>
<t>TBD AUTHENTICATION-REQUIRED </t>
<t>TBD AUTHENTICATION-FAILED </t>
<t>TBD AUTHENTICATION-SUCCEED </t>
<t>TBD AUTHORIZATION-FAILED </t>
<t>TBD SESSION-TERMINATION</t>
</list></t>
</section>
<section title="Packet Format ">
<section title="Packet Format of PCP Auth Messages">
<t>The format of PCP-Auth-request messages is identical to the
response packet format specified in Section 7.2 of <xref
target="RFC6887"/>.</t>
<t>As illustrated in Figure 1, the PCP-Auth-Answer messages use the
requester header specified in Section 7.1 of [RFC6887]. The only
difference is that eight reserved bits are used to transfer the result
codes (e.g., "INITIATION"). Other fields in Figure 1 are described in
Section 7.1 of <xref target="RFC6887"/>.</t>
<figure>
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version = 2 |R| Opcode | Reserved | Result Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Requested Lifetime (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| PCP Client's IP Address (128 bits) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: (optional) Opcode-specific information :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: (optional) PCP Options :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. PCP-Auth-Answer message Format]]></artwork>
</figure>
</section>
<section title="Authentication OpCode Format">
<t>The following figure illustrates the format of an authentication
OpCode: <figure>
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
</figure></t>
<t><list style="empty">
<t>Session ID: This field contains a 32-bit PCP Auth session
identifier. </t>
<t>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.</t>
</list></t>
<t/>
</section>
<section title="Nonce Option">
<t>Because the session identifier of PCP Auth session is determined by
the PCP server, a PCP client does not know the session identifier
which will be used when it sends out a PCP-Auth-Initiation message. In
order to prevent an attacker from interrupting the authentication
process by sending off-line generated PCP-Auth-Request messages, the
PCP client needs to generate a random number as nonce in the
PCP-Auth-Initiation message. The PCP server will append the nonce
within the initial PCP-Auth-Request message. If the PCP-Auth-Request
message does not carry the correct nonce, the message will be
discarded silently.<figure>
<artwork><![CDATA[ 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
</figure><list style="empty">
<t>Option-Length: The length of the Nonce Option (in octet),
including the 4 octet fixed header and the variable length of the
authentication data.</t>
<t>Nonce: A random 32 bits number which is transported within a
PCC-Initiate message and the corresponding reply message from the
PCP server.</t>
</list></t>
</section>
<section title="Authentication Tag Option">
<t><figure>
<artwork><![CDATA[ 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Authentication Data (Variable) |
~ ~
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
</figure></t>
<t><list style="empty">
<t>Option-Length: The length of the Authentication Tag Option (in
octet), including the 12 octet fixed header and the variable
length of the authentication data.</t>
<t>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.</t>
<t>Key ID: The ID associated with the traffic key used to generate
authentication data. This field is filled with zero if MSK is
directly used to secure the message.</t>
<t>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. This field MUST end on a 32-bit boundary,
padded with 0's when necessary.</t>
</list></t>
</section>
<section title="EAP Payload Option">
<t><figure>
<artwork><![CDATA[ 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 |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
</figure></t>
<t><list style="empty">
<t>Option-Length: The length of the EAP Payload Option (in octet),
including the 4 octet fixed header and the variable length of the
EAP message.</t>
<t>EAP Message: The EAP message transferred. Note this field MUST
end on a 32-bit boundary, padded with 0's when necessary.</t>
</list></t>
</section>
<section title="PRF Option">
<t><figure>
<artwork><![CDATA[ 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
</figure>PRF: The Pseudo-Random Function which the sender supports
to generate an MSK. This field contains an IKEv2 Transform ID of
Transform Type 2 <xref target="RFC4306"/>.</t>
</section>
<section title="MAC Algorithm Option">
<t><figure>
<artwork><![CDATA[ 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 ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
</figure>MAC Algorithm ID: Indicate the MAC algorithm which the
sender supports to generate authentication data. The MAC Algorithm ID
field contains an IKEv2 Transform ID of Transform Type 3 <xref
target="RFC4306"/>.</t>
</section>
<section title="Session Lifetime Option">
<t><figure>
<artwork><![CDATA[ 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
</figure>Session Lifetime: The life time of the PCP Auth Session,
which is decided by the authorization result.</t>
</section>
<section title="Received Packet Option">
<t>This option is used in a PCP-Auth-Acknowledgement message to
indicate a packet with the contained sequence number has been
received.<figure>
<artwork><![CDATA[ 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Received Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
</figure>Received Sequence Number: The sequence number of the last
received PCP packet.</t>
</section>
</section>
<section title="Processing Rules">
<t/>
<section title="Authentication Data Generation">
<t>If a PCP SA is generated as the result of a successful EAP
authentication process, every subsequent PCP message within the
session MUST carry an Authentication Tag Option which contains the
digest of the PCP message for data origin authentication and integrity
protection.</t>
<t>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 PCP message being
protected. 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 to 0. After this, the device generates a digest for the
entire PCP message (including the PCP header and Authentication Tag
Option) with the MAC algorithm and the selected traffic key, and input
the generated digest into the Authentication Data field.</t>
</section>
<section title="Authentication Data Validation">
<t>When a device receives a PCP packet with an Authentication Tag
Option, it needs to use the session ID transported in the option to
locate the proper SA, and then find the associated transport key
(using key ID) and the MAC algorithm. If no proper SA is found, the
PCP packet MUST be discarded silently. After storing the value of the
Authentication field of the Authentication Tag Option, the device
fills the Authentication field with zeros. Then, the device generates
a digest for the packet (including the PCP header and Authentication
Tag Option) 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 with, and the validation succeeds. Otherwise, the packet MUST
be discarded.</t>
</section>
<section title="Retransmission Policies">
<t>In order to provide reliable transmission over PCP messages, the
retransmission poclies needs to be considered.</t>
<t>In the base PCP protocol, only PCP clients are responsible for
reliable delivery of PCP request messages according to policies
specified in Section 8.1.1 of [RFC6887], However, in this document,
both PCP clients and PCP servers need to provide reliable delivery of
PCP Auth messages. Therefore, such retransmission policy can be also
applied by the PCP servers.</t>
</section>
<section title="Sequence Number">
<t>PCP adopts UDP to transport signaling messages. As an un-reliable
transport protocol, UDP does not guarantee 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 carry an monotonically
increasing sequence number. During a PCP Auth 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 and
increments the sequence number maintained in the SA 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 does not match
the incoming sequence number the device maintains. After confirming
that the received packet is valid, the device increments the incoming
sequence number maintained in the SA by 1.</t>
<t>The above rules are not applied to PCP-Auth-Acknowledgement
messages whose result code fields are set as PACKET-RECEIVED-ACK. This
type of message is optionally used to avoid un-necessary packet
retransmission and the reliable transmission does not have to be
guaranteed. Therefore, when receiving or sending out a
PCP-Auth-Acknowledgement message, the device MUST not increase the
corresponding sequence number stored in the SA. Otherwise, the lost of
a PCP-Auth-Acknowledgement message during transportation will cause
the mismatching issues with the sequence numbers.</t>
<t>Another exception is message retransmission. When a device does not
receive any response from its session partner in a certain period, it
needs to retransmit the last outgoing PCP Auth message with a limited
rate. The duplicate messages and the original message MUST use the
identical sequence number. When the device receives such duplicate PCP
Auth messages from its session partner, it MUST try to answer them by
sending the last outgoing PCP Auth message with a limited rate unless
it has received another valid message with a larger sequence number
from its session. In such cases, the maintained incoming and outgoing
sequence numbers will not be affected by the message
retransmission.</t>
</section>
<section title="MTU Considerations">
<t>EAP methods are responsible for MTU handling, so no special
facilities are required in this protocol to deal with MTU issues.</t>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>TBD</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>This section applies only to the in-band key management mechanism. It
will need to be updated if the WG choose to pursue the out-of-band key
management mechanism discussed above.</t>
<t>In this work, after a successful EAP authentication process performed
between two PCP devices, a MSK will be exported. The MSK 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.</t>
<t>However, before a transport key has been generated, the PCP Auth
messages exchanged within a PCP Auth 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
PCP-Auth-Request and PCP-Auth-Answer exchange is vulnerable to spoofing
attacks as these messages are not authenticated and integrity protected.
In addition, because the PRF and MAC algorithms are transported at this
stage, an attacker may try to remove the PRF and MAC options containing
strong algorithms from the initial PCP-Auth-Request message and force
the client choose the weakest algorithms. Therefore, the server needs to
guarantee that all the PRF and MAC algorithms it provids support are
strong enough.</t>
<t>In order to prevent very basic DOS attacks, a PCP device SHOULD
generate state information as little as possible in the initial
PCP-Auth-Request and PCP-Auth-Answer exchanges. The choice of EAP method
is also very important. The selected EAP method must be resilient to the
attacks possibly in an insecure network environment, and the
user-identity confidentiality, protection against dictionary attacks,
and session-key establishment must be supported.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t/>
</section>
<section title="Change Log">
<section title="Changes from wasserman-pcp-authentication-02 to ietf-pcp-authentication-00">
<t><list style="symbols">
<t>Added discussion of in-band and out-of-band key management
options, leaving choice open for later WG decision.</t>
<t>Removed support for fragmenting EAP messages, as that is
handled by EAP methods.</t>
</list></t>
</section>
<section title="Changes from wasserman-pcp-authentication-01 to -02">
<t><list style="symbols">
<t>Add a nonce into the first two exchanged PCP Auth message
between the PCP client and PCP server. When a PCP client initiate
the session, it can use the nonce to detect offline attacks.</t>
<t>Add the key ID field into the authentication tag option so that
a MSK can generate multiple traffic keys.</t>
<t>Specify that when a PCP device receives a PCP-Auth-Request or a
PCP-Auth-Answer message from its partner the PCP device needs to
reply with a PCP-Auth-Acknowledge message to indicate that the
message has been received.</t>
<t>Add the support of fragmenting EAP messages.</t>
</list></t>
</section>
<section title="Changes from ietf-pcp-authentication-00 to -01">
<t><list style="symbols">
<t>Editorial changes, added use cases to introduction.</t>
</list></t>
</section>
<section title="Changes from ietf-pcp-authentication-01 to -02">
<t><list style="symbols">
<t>Add the support of re-authentication initiated by PCP
server.</t>
<t>Specify that when a PCP device receives a PCP-Auth-Request or a
PCP-Auth-Answer message from its partner the PCP device MAY reply
with a PCP-Auth-Acknowledge message to indicate that the message
has been received.</t>
<t>Discuss the format of the PCP-Auth-Acknowledge message.</t>
<t>Remove the redundant information from the Auth OpCode, and
specify new result codes transported in PCP packet headers</t>
<t/>
</list></t>
</section>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.3748'?>
<?rfc include='reference.RFC.4306'?>
<?rfc include='reference.RFC.5191'?>
<?rfc include='reference.RFC.5448'?>
<?rfc include='reference.RFC.6887'?>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 14:24:34 |