Internet Draft                                       Jesse Walker
     Expiration: February March 2005                          Amol Kulkarni, Ed.
     File: draft-ietf-rap-cops-tls-08.txt draft-ietf-rap-cops-tls-09.txt                  Intel Corp.

                               COPS Over TLS

                         Last Updated: August 16, September 24, 2004

 Status of this Memo

    This document is an Internet-Draft and is in full conformance with subject to all provisions
    of Section 10 section 3 of RFC 3667 [RFC3667].  By submitting this Internet-
    Draft, each author represents that any applicable patent or other
    IPR claims of which he or she is aware have been or will be
    disclosed, and any of [RFC2026]. which he or she become aware will be
    disclosed, in accordance with RFC 3668.

    Internet-Drafts are working documents of the Internet Engineering
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 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 RFC 2119
    [RFC2119].

 Abstract

    This memo document describes how to use TLS Transport Layer Security (TLS)
    to secure COPS Common Open Policy Service (COPS) connections over the
    Internet.

    Please send comments on this

    This document to also updates RFC 2748 by modifying the contents of
    the rap@ops.ietf.org
    mailing list. Client-Accept message.

 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 Security ClientSI Object..................................4
    4.2 Error Codes...................................................4
    5  COPS/TLS Secure Connection Initiation..........................4
    5.1 PDP PEP Initiated Security Negotiation............................4 Negotiation............................5
    5.2 PEP PDP Initiated Security Negotiation............................5
    6  Connection Closure.............................................6
    6.1 PEP System Behavior...........................................6
    6.2 PDP System Behavior...........................................6 Behavior...........................................7
    7  Port Number....................................................7
    8  Endpoint Identification and Access Control.....................7
    8.1
    7.1 PDP Identity..................................................8
    8.2
    7.2 PEP Identity..................................................8
    9
    8  Backward Compatibility.........................................9
    10
    9 IANA Considerations............................................9
    11 Considerations.............................................9
    10 Security Considerations........................................9
    12 Acknowledgements...............................................9
    13 References....................................................10
    13.1
    11 References.....................................................9
    11.1 Normative References........................................10
    13.2
    11.2 Informative References......................................10
    14
    12  Author Addresses.............................................10
    13  IPR Disclosure Acknowledgement...............................10
    14  Disclaimer of Validity.......................................11
    15  Intellectual Property Statement..............................11
    16 Full  Copyright Statement......................................11 Statement..........................................11
    16  Disclaimer...................................................11
    17  Acknowledgements.............................................11
 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].

    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 Security ClientSI Object

    The StartTLS Security ClientSI object is used by the PDP and the PEP to start
    the TLS negotiation. This object can should be included either only in the
    ClientAccept message,
    Client-Open or a Request message. Also, the ClientType of
    any message containing this ClientSI object Client-Accept messages. It MUST NOT be 0. included in
    any other COPS message.

          0         1          2          3
    +----------+----------+----------+----------+
    |    Length (Octets)  | C-Num=9  | C-Type=1 C-Type=2 |
    +----------+----------+----------+----------+
    |       ////////      |        Flags        |
    +----------+----------+----------+----------+
    Note: //// implies the field is reserved, set to 0 and should be
          ignored on receipt.

    Flags:
         1 16 bits
         0x01 = StartTLS
         This flag indicates that the sender of the message wishes to
         initiate a TLS handshake.

    The Client-Type of any message containing this Named ClientSI object
    MUST be 0. Client-Type 0 is used to negotiate COPS connection level
    security and must only be used during the connection establishment
    phase. Please refer to section 4.1 of [RFC2748] for more details.

 4.2 Error Codes

    This section adds to the error codes described in section 2.2.8
    (Error Object) of [RFC2748].

    Error Code: 16 error-code-TBD-by-IANA = 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. to indicate a
    security-related connection closure.

 5  COPS/TLS Secure Connection Initiation
    Security negotiation may be initiated either by the PDP or the PEP.
    The PDP PEP can initiate a security negotiation either via a
    ClientAccept or a ClientClose Client-Open message, while
    a PEP PDP can initiate a negotiation via a Request Client-Accept message.

    Once the TLS connection is established, all COPS data MUST be sent
    as TLS "application data".

 5.1 PDP PEP Initiated Security Negotiation
    The

    A PEP initially opens a TCP connection MAY initiate security negotiation with the a PDP on using the
    standard COPS port and sends a ClientOpen Client-
    Open message. This ClientOpen The Client-Open message MUST have a ClientType Client-Type of 0.

    The PDP then replies with a ClientAccept. In order to signal the PEP
    to start the TLS handshake, the PDP 0
    and MUST include the StartTLS Security ClientSI object in object.

    Upon receiving the ClientAccept message. Client-Open message, the PDP SHOULD respond with
    a Client-Accept message containing the Security ClientSI object.

    Note that in order to carry the StartTLS Security ClientSI object, the
    contents of the ClientAccept Client-Accept 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 appropriate Client-Accept message, the PEP SHOULD
    initiate the TLS handshake.

    The message exchange is as follows:
    C: Client-Open   (Client-Type = 0, Security)
    S: Client-Accept (Client-Type = 0, Security)
    <TLS handshake>
    C/S: <...further messages...>

    Instead of sending a Client-Accept message, the PDP may choose to
    close the connection if it does not wish to open a secure connection
    with the StartTLS PEP. It MUST include the error code error-code-TBD-by-IANA
    in the ensuing Client-Close message.

    A PEP expecting the Security ClientSI object in a Client-Accept
    message MUST close the connection if the ClientSI object is missing.
    It MUST include the error code error-code-TBD-by-IANA in the ensuing
    Client-Close message.

 5.2 PDP Initiated Security Negotiation

    The PEP initially opens a TCP connection with the PDP on the
    standard COPS port and sends a Client-Open message. This Client-Open
    message MUST have a Client-Type of 0.

    The PDP SHOULD then reply with a Client-Accept message. In order to
    signal the PEP to start the TLS handshake, the PDP MUST include the
    Security ClientSI object in the Client-Accept message.

    Upon receiving the Client-Accept message with the Security 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 Client-Open   (Client-Type = 0)
    S: ClientAccept (ClientType Client-Accept (Client-Type = 0, StartTLS) Security)
    <TLS handshake>
    C/S: <...further messages...>

    Until

    Before completion of the TLS handshake is complete handshake, the PEP MUST NOT send any
    messages other than ClientClose Client-Close and KeepAlive. Keep-Alive. Upon receiving any
    other message, a PDP expecting a TLS negotiation MUST issue a
    ClientClose
    Client-Close message with an error code of 16.

 5.2 PEP Initiated Security Negotiation

    If a PEP wishes error-code-TBD-by-IANA.

    A PDP wishing to use TLS on an existing non-secure COPS
    connection, it MUST issue a Request message negotiate security with a ClientType of 0.
    The StartTLS ClientSI object PEP having a non-secure
    connection 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 Client-Close 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
    If the PEP's TLS request is rejected by the PDP, error code error-code-
    TBD-by-IANA and wait for the PEP MAY choose to continue using reconnect. Upon receiving the non-secure connection. Else,
    Client-Open message, it MUST close SHOULD use the
    connection by sending a ClientClose Client-Accept message with an error code of
    16. to
    initiate security negotiation.

 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.

    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 deployments 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 deployments 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.

    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

 7.1 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 deployments 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

 7.2 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
    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

 8  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 Security 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

 9 IANA Considerations

    The IANA shall add the following Error-Code to the cops-parameters
    document:
    registry located at http://www.iana.org/assignments/cops-parameters.

    Error-Code: 16 error-code-TBD-by-IANA
    Description: TLS Required

 11

    For the Named ClientSI object for Client-Type 0, the IANA shall add
    the following Flags value:
    0x01 = StartTLS

    Further values for the Flags field and the reserved field can only
    be assigned by IETF Consensus rule as defined in [RFC2434].

 10 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 Security
    ClientSI object from the ClientAccept Client-Open or Request Client-Accept 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.

    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

 11 References
 13.1
 11.1 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

 11.2 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 3207, February 2002.

       [RFC2434] Alvestrand, H., Narten, T., "Guidelines for writing an
       IANA Considerations Section in RFCs", BCP 26, RFC 2434, October
       1998.

 12  Author Addresses

       Jesse R. Walker
       Intel Corporation
       2111 N.E. 25th Avenue
       Hillsboro, OR  97214
       USA
       jesse.walker[at]intel.com
       jesse[dot]walker[at]intel[dot]com

       Amol Kulkarni
       Intel Corporation
       JF3-206
       2111 N.E. 25th Avenue
       Hillsboro, OR  97214
       USA
       amol.kulkarni[at]intel.com
 15  Intellectual Property Statement
       amol[dot]kulkarni[at]intel[dot]com

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    accordance with RFC 3668.

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 17  Acknowledgements

    This document freely plagiarizes and adapts Eric Rescorla's similar
    document [RFC2818] that specifies how HTTP runs over TLS.
    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.

    Funding for the RFC Editor function is currently provided by the
    Internet Society.