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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 4261

     Internet Draft                                       Jesse Walker
     Expiration: February 2005                       Amol Kulkarni, Ed.
     File: draft-ietf-rap-cops-tls-08.txt                  Intel Corp.
 
 
 
                               COPS Over TLS
 
                         Last Updated: August 16, 2004
 
 
 
 Status of this Memo
 
    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of [RFC2026].
 
    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
    other groups may also distribute working documents as Internet-
    Drafts.
 
    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."
 
    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt
 
    The list of Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.
 
 
 Conventions used in this document
 
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
    this document are to be interpreted as described in [RFC2119].
 
 
 Abstract
 
    This memo describes how to use TLS to secure COPS connections over
    the Internet.
 
    Please send comments on this document to the rap@ops.ietf.org
    mailing list.
 
 
 
 
 
 
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 Table Of Contents
    Glossary..........................................................3
    1  Introduction...................................................3
    2  COPS Over TLS..................................................3
    3  Separate Ports versus Upward Negotiation.......................3
    4  COPS/TLS Objects and Error codes...............................4
    4.1 The StartTLS ClientSI Object..................................4
    4.2 Error Codes...................................................4
    5  COPS/TLS Secure Connection Initiation..........................4
    5.1 PDP Initiated Security Negotiation............................4
    5.2 PEP Initiated Security Negotiation............................5
    6  Connection Closure.............................................6
    6.1 PEP System Behavior...........................................6
    6.2 PDP System Behavior...........................................6
    7  Port Number....................................................7
    8  Endpoint Identification and Access Control.....................7
    8.1 PDP Identity..................................................8
    8.2 PEP Identity..................................................8
    9  Backward Compatibility.........................................9
    10 IANA Considerations............................................9
    11 Security Considerations........................................9
    12 Acknowledgements...............................................9
    13 References....................................................10
    13.1 Normative References........................................10
    13.2 Informative References......................................10
    14  Author Addresses.............................................10
    15  Intellectual Property Statement..............................11
    16 Full Copyright Statement......................................11
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 Glossary
       COPS - Common Open Policy Service. See [RFC2748].
       COPS/TCP - A plain-vanilla implementation of COPS.
       COPS/TLS - A secure implementation of COPS using TLS.
       PDP - Policy Decision Point. Also referred to as the Policy
             Server. See [RFC2753].
       PEP - Policy Enforcement Point. Also referred to as the Policy
             Client. See [RFC2753].
 
 1  Introduction
 
    COPS [RFC2748] was designed to distribute clear-text policy
    information from a centralized Policy Decision Point (PDP) to a set
    of Policy Enforcement Points (PEP) in the Internet. COPS provides
    its own security mechanisms to protect the per-hop integrity of the
    deployed policy. However, the use of COPS for sensitive applications
    such as some types of security policy distribution requires
    additional security measures, such as data privacy. This is because
    some organizations find it necessary to hide some or all of their
    security policies, e.g., because policy distribution to devices such
    as mobile platforms can cross domain boundaries.
 
    TLS [RFC2246] was designed to provide channel-oriented security. TLS
    standardizes SSL and may be used with any connection-oriented
    service. TLS provides mechanisms for both one- and two-way
    authentication, dynamic session keying, and data stream privacy and
    integrity.
 
    This document describes how to use COPS over TLS. "COPS over TLS" is
    abbreviated COPS/TLS.
 
 2  COPS Over TLS
 
    COPS/TLS is very simple: use COPS over TLS similar to how you would
    use COPS over TCP (COPS/TCP). Apart from a specific procedure used
    to initialize the connection, there is no difference between
    COPS/TLS and COPS/TCP.
 
 3  Separate Ports versus Upward Negotiation
 
    There are two ways in which insecure and secure versions of the same
    protocol can be run simultaneously.
 
    In the first method, the secure version of the protocol is also
    allocated a well-known port. This strategy of having well-known port
    numbers for both, the secure and insecure versions, is known as
    'Separate Ports'. The clients requiring security can simply connect
    to the well-known secure port. This method is easy to implement,
    with no modifications needed to existing insecure implementations.
    The disadvantage, however, is that it doesn't scale well, with a new
    port required for each secure implementation. More problems with
    this approach have been listed in [RFC2595].
 
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    The second method is known as 'Upward Negotiation'. In this method,
    the secure and insecure versions of the protocol run on the same
    port. The client connects to the server, both discover each others'
    capabilities, and start security negotiations if desired. This
    method usually requires some changes to the protocol being secured.
 
    COPS/TLS uses the Upward Negotiation method to secure COPS messages.
 
 4  COPS/TLS Objects and Error codes
 
    This section describes the COPS objects and error codes needed to
    support COPS/TLS.
 
 4.1 The StartTLS ClientSI Object
 
    The StartTLS ClientSI object is used by the PDP and the PEP to start
    the TLS negotiation. This object can be included either in the
    ClientAccept message, or a Request message. Also, the ClientType of
    any message containing this ClientSI object MUST be 0.
 
          0         1          2          3
    +----------+----------+----------+----------+
    |    Length (Octets)  | C-Num=9  | C-Type=1 |
    +----------+----------+----------+----------+
    |       ////////      |        Flags        |
    +----------+----------+----------+----------+
 
    Flags:
         1 = TLS
 
 4.2 Error Codes
 
    This section adds to the error codes described in section 2.2.8
    (Error Object) of [RFC2748].
 
    Error Code: 16 = TLS Required
 
    This error code should be used by either PEP or PDP if they require
    security but the other side doesn't support it.
 
 5  COPS/TLS Secure Connection Initiation
 
    Security negotiation may be initiated either by the PDP or the PEP.
    The PDP can initiate a security negotiation either via a
    ClientAccept or a ClientClose message, while a PEP can initiate a
    negotiation via a Request message.
 
    Once the TLS connection is established, all COPS data MUST be sent
    as TLS "application data".
 
 5.1 PDP Initiated Security Negotiation
 
 
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    The PEP initially opens a TCP connection with the PDP on the
    standard COPS port and sends a ClientOpen message. This ClientOpen
    message MUST have a ClientType of 0.
 
    The PDP then replies with a ClientAccept. In order to signal the PEP
    to start the TLS handshake, the PDP MUST include the StartTLS
    ClientSI object in the ClientAccept message.
 
    Note that in order to carry the StartTLS ClientSI object, the
    contents of the ClientAccept message defined in section 3.7 of
    [RFC2748] need to change to the following:
 
    <Client-Accept> ::= <Common Header>
                        <KA Timer>
                        [<ACCT Timer>]
                        [<ClientSI>]
                        [<Integrity>]
 
    Upon receiving the ClientAccept message with the StartTLS ClientSI
    object, the PEP SHOULD initiate the TLS handshake. If for any reason
    the PEP cannot initiate the handshake, it MUST close the connection.
 
    The message exchange is as follows:
    C: ClientOpen   (ClientType = 0)
    S: ClientAccept (ClientType = 0, StartTLS)
    <TLS handshake>
    C/S: <...further messages...>
 
    Until the TLS handshake is complete the PEP MUST NOT send any
    messages other than ClientClose and KeepAlive. Upon receiving any
    other message, a PDP expecting a TLS negotiation MUST issue a
    ClientClose message with an error code of 16.
 
 5.2 PEP Initiated Security Negotiation
 
    If a PEP wishes to use TLS on an existing non-secure COPS
    connection, it MUST issue a Request message with a ClientType of 0.
    The StartTLS ClientSI object MUST be included in the request.
 
    In response, the PDP SHOULD send a Decision message containing the
    appropriate Command-Code (1 = Install/Accept, 2 = Remove/Reject) in
    the Decision Flags object.
 
    If the request is accepted, the PEP MUST start the TLS handshake.
    After the TLS handshake is complete, the PDP MUST synchronize state
    with the PEP.
 
    The message exchange is as follows:
    <...existing COPS/TCP connection...>
    C: Request   (ClientType = 0, StartTLS)
    S: Decision  (ClientType = 0, Install)
    <TLS handshake>
    S: Synchronize
 
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    If the PEP's TLS request is rejected by the PDP, the PEP MAY choose
    to continue using the non-secure connection. Else, it MUST close the
    connection by sending a ClientClose message with an error code of
    16.
 
 6  Connection Closure
 
    TLS provides facilities to securely close its connections. Reception
    of a valid closure alert assures an implementation that no further
    data will arrive on that connection. The TLS specification requires
    TLS implementations to initiate a closure alert exchange before
    closing a connection. It also permits TLS implementations to close
    connections without waiting to receive closure alerts from the peer,
    provided they send their own first. A connection closed in this way
    is known as an "incomplete close". TLS allows implementations to
    reuse the session in this case, but COPS/TLS makes no use of this
    capability.
 
    A connection closed without first sending a closure alert is known
    as a "premature close". Note that a premature close does not call
    into question the security of the data already received, but simply
    indicates that subsequent data might have been truncated. Because
    TLS is oblivious to COPS message boundaries, it is necessary to
    examine the COPS data itself (specifically the Message header) to
    determine whether truncation occurred.
 
 6.1 PEP System Behavior
 
    PEP implementations MUST treat premature closes as errors and any
    data received as potentially truncated. The COPS protocol allows the
    PEP system to find out whether truncation took place. A PEP system
    detecting an incomplete close SHOULD recover gracefully.
 
    PEP systems MUST send a closure alert before closing the connection.
    PEPs unprepared to receive any more data MAY choose not to wait for
    the PDP system's closure alert and simply close the connection, thus
    generating an incomplete close on the PDP side.
 
 6.2 PDP System Behavior
 
    COPS permits a PEP to close the connection at any time, and requires
    PDPs to recover gracefully. In particular, PDPs SHOULD be prepared
    to receive an incomplete close from the PEP, since a PEP often shuts
    down for operational reasons unrelated to the transfer of policy
    information between the PEP and PDP.
 
        Implementation note: The PDP ordinarily expects to be able to
        signal end of data by closing the connection. However, the PEP
        may have already sent the closure alert and dropped the
        connection.
 
 
 
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    PDP systems MUST attempt to initiate an exchange of closure alerts
    with the PEP system before closing the connection. PDP systems MAY
    close the connection after sending the closure alert, thus
    generating an incomplete close on the PEP side.
 
 7  Port Number
 
    The first data a PDP expects to receive from the PEP is a Client-
    Open message. The first data a TLS server (and hence a COPS/TLS PDP)
    expects to receive is the ClientHello. Consequently, COPS/TLS runs
    over a separate port in order to distinguish it from COPS alone.
    When COPS/TLS runs over a TCP/IP connection, the TCP port is any
    non-well-known port of the PDP's choice. This port MUST be
    communicated to the COPS/TCP PDP running on the well-known COPS TCP
    port. The PEP may use any TCP port. This does not preclude COPS/TLS
    from running over another transport. TLS only presumes a reliable
    connection-oriented data stream.
 
 8  Endpoint Identification and Access Control
 
    All PEP implementations of COPS/TLS MUST support an access control
    mechanism to identify authorized PDPs. This requirement provides a
    level of assurance that the policy arriving at the PEP is actually
    valid. PEP implementations SHOULD require the use of this access
    control mechanism for operation of COPS over TLS. When access
    control is enabled, the PEP implementation MUST NOT initiate
    COPS/TLS connections to systems not authorized as PDPs by the access
    control mechanism.
 
    Similarly, PDP COPS/TLS implementations MUST support an access
    control mechanism permitting them to restrict their services to
    authorized PEP systems only. However, implementations MAY choose not
    to use an access control mechanism at the PDP, as organizations
    might not consider the types of policy being deployed as sensitive,
    and therefore do not need to incur the expense of managing
    credentials for the PEP systems. If access controls are used,
    however, the PDP implementation MUST terminate COPS/TLS connections
    from unauthorized PEP systems and log an error if an auditable
    logging mechanism is present.
 
    Implementations of COPS/TLS MUST use X.509 v3 certificates
    conforming to [RFC3280] to identify PDP and PEP systems. COPS/TLS
    systems MUST perform certificate verification processing conforming
    to [RFC3280].
 
    If a subjectAltName extension of type dNSName or iPAddress is
    present in the PDP's certificate, it MUST be used as the PDP
    identity. If both types are present, dNSName SHOULD be used as the
    PDP identity. If neither of the types is present, the most specific
    Common Name field in the Subject field of the certificate SHOULD be
    used.
 
 
 
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    Matching is performed using the matching rules specified by
    [RFC3280]. If more than one identity of a given type is present in
    the certificate (e.g. more than one dNSName name in the
    subjectAltName certificate extension), a match in any one of the
    provided identities is acceptable. Generally, the COPS system uses
    the first name for matching, except as noted below in the IP
    address checking requirements.
 
 8.1 PDP Identity
 
    Generally, COPS/TLS requests are generated by the PEP consulting
    bootstrap policy information that identifies PDPs that the PEP is
    authorized to connect to. This policy provides the PEP with the
    hostname or IP address of the PDP. How this bootstrap policy
    information arrives at the PEP is outside the scope of this
    document. However, all PEP implementations MUST provide a mechanism
    to securely deliver or configure the bootstrap policy.
 
    All PEP implementations MUST be able to securely acquire the signing
    certificates of authorized Certificate Authorities that issue PDP
    certificates. Also, the PEPs MUST support a mechanism to securely
    acquire an access control list or filter identifying the CA's set of
    authorized PDPs.
 
    PEP implementations that participate in multiple domains, such as
    those on mobile platforms, MAY use different CAs and access control
    lists in each domain.
 
    If the PDP hostname or IP address is available via the bootstrap
    policy, the PEP MUST check it against the PDP's identity as
    presented in the PDP's TLS Certificate message.
 
    In some cases the bootstrap policy will identify the authorized PDP
    only by an IP address of the PDP system. In this case, the
    subjectAltName MUST be present in the certificate, and it MUST
    include an iPAdress format matching the expected name of the policy
    server.
 
    If the hostname of the PDP does not match the identity in the
    certificate, a PEP on a user oriented system MUST either notify the
    user (PEP systems MAY afford the user the opportunity to continue
    with the connection in any case) or terminate the connection with a
    bad certificate error. PEPs on unattended systems MUST log the error
    to an appropriate audit log (if available) and MUST terminate the
    connection with a bad certificate error. Unattended PEP systems MAY
    provide a configuration setting that disables this check, but then
    MUST provide a setting which enables it.
 
 8.2 PEP Identity
 
    When PEP systems are not access controlled, the PDP need have no
    external knowledge of what the PEP's identity ought to be and so
    checks are neither possible nor necessary. In this case, there is no
 
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    requirement for PEP systems to register with a certificate
    authority, and COPS over TLS uses one-way authentication, of the PDP
    to the PEP.
 
    When PEP systems are access controlled, PEPs MUST be PKI clients in
    the sense of [RFC3280]. In this case, COPS over TLS uses two-way
    authentication, and the PDP MUST perform the same identity checks
    for the PEPs as described above for the PDP.
 
    When access controls are in effect at the PDP, PDP implementations
    MUST have a mechanism to securely acquire the signing certificates
    of the Certificate Authorities issuing certificates to any of the
    PEPs they support.
 
 9  Backward Compatibility
 
    The PEP and PDP SHOULD be backward compatible with peers that have
    not been modified to support COPS/TLS. They SHOULD handle errors
    generated in response to the StartTLS ClientSI object.
 
    In case a PEP does not start the TLS handshake upon receiving the
    StartTLS ClientSI object, the PDP MUST close the connection.
 
 10 IANA Considerations
 
    The IANA shall add the following Error-Code to the cops-parameters
    document:
 
    Error-Code: 16
    Description: TLS Required
 
 11 Security Considerations
 
    A COPS PDP and PEP MUST check the results of the TLS negotiation to
    see whether an acceptable degree of authentication and privacy have
    been achieved. If the negotiation has resulted in unacceptable
    algorithms or key lengths, either side MAY choose to terminate the
    connection.
 
    A man-in-the-middle attack can be launched by deleting the StartTLS
    ClientSI object from the ClientAccept or Request messages. To
    prevent this, the PEP and PDP MUST use the Integrity object as
    defined in [RFC2748].
 
    A downgrade attack against a PEP requesting TLS negotiation is
    possible by modifying the PDP's Decision message flag to 'Remove'.
    Again, this can be avoided by using the Integrity object as defined
    in [RFC2748].
 
 12 Acknowledgements
 
    This document freely plagiarizes and adapts Eric Rescorla's similar
    document [RFC2818] that specifies how HTTP runs over TLS.
 
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    Discussions with David Durham, Scott Hahn and Ylian Sainte-Hillaire
    also lead to improvements in this document.
    The authors wish to thank Uri Blumenthal for doing a thorough
    security review of the document.
 
 13 References
 13.1 Normative References
 
       [RFC2026] Bradner, S., "The Internet Standards Process - Revision
       3", RFC 2026, October 1996
 
       [RFC2119] Bradner, S., "Key Words for use in RFCs to indicate
       Requirement Levels", RFC 2119, March 1997.
 
       [RFC2748] Durham, D., Boyle, J., Cohen, R., Herzog, R., Rajan,
       R., Sastry, A., "The COPS (Common Open Policy Service) Protocol",
       RFC 2748, January 2000.
 
       [RFC3280] Housley, R., Ford, W., Polk, W., Solo, D., "Internet
       X.509 Public Key Infrastructure Certificate and Certificate
       Revocation List (CRL) Profile ", RFC 3280, April 2002.
 
       [RFC2246] Dierks, T., Allen, C., "The TLS Protocol", RFC 2246,
       January 1999.
 
 13.2 Informative References
 
       [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
 
       [RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
       2595, June 1999.
 
       [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP
       over Transport Layer Security", RFC 3207, February 2002.
 
 
 14  Author Addresses
 
       Jesse R. Walker
       Intel Corporation
       2111 N.E. 25th Avenue
       Hillsboro, OR  97214
       USA
       jesse.walker[at]intel.com
 
       Amol Kulkarni
       Intel Corporation
       JF3-206
       2111 N.E. 25th Avenue
       Hillsboro, OR  97214
       USA
       amol.kulkarni[at]intel.com
 
 
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 15  Intellectual Property Statement
 
    The IETF takes no position regarding the validity or scope of any
    intellectual property or other rights that might be claimed to
    pertain to the implementation or use of the technology described in
    this document or the extent to which any license under such rights
    might or might not be available; neither does it represent that it
    has made any effort to identify any such rights. Information on the
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    claims of rights made available for publication and any assurances
    of licenses to be made available, or the result of an attempt made
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    proprietary rights by implementors or users of this specification
    can be obtained from the IETF Secretariat.
 
    The IETF invites any interested party to bring to its attention any
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    rights which may cover technology that may be required to practice
    this standard. Please address the information to the IETF Executive
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    The IETF has been notified of intellectual property rights claimed
    in regard to some or all of the specification contained in this
    document. For more information consult the online list of claimed
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 16 Full Copyright Statement
 
    Copyright (C) The Internet Society (2004). All Rights Reserved.
 
    This document and translations of it may be copied and furnished to
    others, and derivative works that comment on or otherwise explain it
    or assist in its implementation may be prepared, copied, published
    and distributed, in whole or in part, without restriction of any
    kind, provided that the above copyright notice and this paragraph
    are included on all such copies and derivative works. However, this
    document itself may not be modified in any way, such as by removing
    the copyright notice or references to the Internet Society or other
    Internet organizations, except as needed for the purpose of
    developing Internet standards in which case the procedures for
    copyrights defined in the Internet Standards process must be
    followed, or as required to translate it into languages other than
    English.
 
    The limited permissions granted above are perpetual and will not be
    revoked by the Internet Society or its successors or assignees.
 
    This document and the information contained herein is provided on an
    "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
    TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
    BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 
 
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    HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
    MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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