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Versions: 00 01 02

INTERNET-DRAFT                                           Donald Eastlake
Intended status: Proposed Standard                                Huawei
Expires: June 29, 2017                                 December 28, 2016

                          TRILL: Group Keying
               <draft-eastlake-trill-group-keying-01.txt>


Abstract

   This document specifies a general group keying protocol. It also
   provides use profiles for the application of this group keying
   protocol to multi-destination TRILL Extended RBridge Channel message
   security and TRILL over IP packet security.


Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the authors or the TRILL working group mailing list:
   trill@ietf.org.

   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/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.
















D. Eastlake                                                     [Page 1]


INTERNET-DRAFT                                       TRILL: Group Keying


Table of Contents

      1. Introduction............................................3
      1.1  Terminology and Acronyms..............................3

      2. Group Keying Protocol...................................5
      2.1 Assumptions............................................5
      2.2 Group Keying Procedure Overview........................5
      2.3 Transmission and Receipt of Group Data Messages........6
      2.4 Changes in Group Membership or GKd.....................6
      2.5 Group Keying Messages..................................7
      2.6 Set Key Message........................................9
      2.7 Use, Delete, Disuse, or Deleted Key Messages..........11
      2.8 Response Message......................................12
      2.8.1 Response Codes......................................14
      2.8 No-Op Message.........................................15
      2.9 General Security Considerations.......................16

      3. Extended RBridge Channel Group Keyed Security..........17
      3.1 Transmission of Group Keying Messages.................17
      3.2 Transmission of Protected Multi-destination Data......18

      4. TRILL Over IP Group Keyed Security.....................19
      4.1 Transmission of Group Keying Messages.................19
      4.2 Transmission of Protected Multi-destination Data......19

      5. IANA Considerations....................................20
      5.1 Group Keying Protocol.................................20
      5.2 Group Keying RBridge Channel Protocol Numbers.........21
      5.3 Group Secured Extended RBridge Channel SType..........21

      6. Security Considerations................................22

      Normative References......................................23
      Informative References....................................24

      Acknowledgements..........................................25
      Authors' Addresses........................................26














D. Eastlake                                                     [Page 2]


INTERNET-DRAFT                                       TRILL: Group Keying


1. Introduction

   This document specifies a general group keying protocol in Section 2.
   In addition, it provides, in Section 3, the use profile for the
   application of this group keying protocol to TRILL [RFC6325]
   [RFC7780] Extended RBridge Channel message security [RFC7178]
   [RFC7978]. It is anticipated that there will be other uses for this
   group keying protocol, for example in connection with link security
   in [TRILLoverIP].



1.1  Terminology and Acronyms

   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].

   This document uses terminology and acronyms defined in [RFC6325] and
   [RFC7178].  Some of these are repeated below for convenience along
   with additional new terms and acronyms.

      AES - Advanced Encryption Standard.

      Data Label - VLAN or FGL.

      DTLS - Datagram Transport Level Security [RFC6347].

      FGL - Fine Grained Label [RFC7172].

      GKd - A distinguished station in a group that is in charge of
         which group keying (Section 2) is in use.

      GKs - Stations in a group other than GKd (Section 2).

      HKDF - Hash based Key Derivation Function [RFC5869].

      IS-IS - Intermediate System to Intermediate System [RFC7176].

      keying material - The set of a Key ID, a secret key, and a cypher
         suite.

      PDU - Protocol Data Unit.

      RBridge - An alternative term for a TRILL switch.

      SHA - Secure Hash Algorithm [RFC6234].

      TRILL - Transparent Interconnection of Lots of Links or Tunneled
         Routing in the Link Layer.


D. Eastlake                                                     [Page 3]


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      TRILL switch - A device that implements the TRILL protocol
         [RFC6325] [RFC7780], sometimes referred to as an RBridge.


















































D. Eastlake                                                     [Page 4]


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2. Group Keying Protocol

   This section defines a general Group Keying Protocol that provides
   shared secret group keys.  Any particular use of this protocol will
   require a profiling giving further details and specifics for that
   use. The protocol is not suitable for discovery messages but is
   intended for use between members of a group that have already
   established pair-wise security.



2.1 Assumptions

   The following are assumed:
      - All pairs of stations in the group can engage in pairwise
        communication with unicast messages and each can groupcast a
        message to the other group members.
      - At any particular time, there is a distinguished station GKd in
        the group that is in charge of keying for the groupcast data
        messages to be sent to the group. The group wide shared secret
        keys established by GKd are referred to herein as "dynamic"
        keys.
      - Pairwise keying has been negotiated between GKd and each other
        station GKs1, GKs2, ... GKsN in the group. These keys are
        referred to in this protocol as "pairwise" keys.
      - One or more keys, other than the dynamic or pairwise keys, are
        already in place at all group member stations. These are
        referred to as "stable" keys.

   When keying material is stored by a station, it is accompanied by a
   "use flag" indicating whether or not that keying material is usable
   for groupcast transmissions.



2.2 Group Keying Procedure Overview

   GKd sends unicast keying messages to the other stations in the group
   and they respond as specified below and in further detail in the
   particular use profile for this Group Keying Protocol. All such
   keying messages MUST be encrypted and authenticated using the
   pairwise keys as further specified in the use profile.

   Typically, GKd sends a keying message to each GKs with keying
   material.  After successful acknowledgement of receipt from each GKs,
   GKd sends a keying message to each GKs instructing it to use the
   dynamic key GKd has set. It would be common for GKd to set a new
   dynamic key at each GKs while an older dynamic key is in use so that
   GKd can more promptly roll over to the new key when appropriate.



D. Eastlake                                                     [Page 5]


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   To avoid an indefinite build up of keying material at a GKs, keys
   have a lifetime specified by GKd and GKd can send a message deleting
   a key. (GKd can also send a message indicating that a key is no
   longer to be used but leaving it set.) Should the space available at
   a GKs for keying material be exhausted, on receipt of a Set Key
   keying message for a new key ID GKs discards a dynamic key it has and
   originates a Delete Key message to the source of that dynamic key.



2.3 Transmission and Receipt of Group Data Messages

   If a group has only two members, then pairwise security is used
   between them.

   When a group has more than two members and a station in the group
   transmits a data message to the group, if the transmitter has one or
   more keys set by GKd that it has been instructed to use, it uses one
   of those keys and its associated cypher suite to groupcast the data
   message.  If it has no such key, then it uses serial unicast to send
   the data message to each other member of the group, negotiating
   pairwise keys with them if it does not already have such pairwise
   keys. Thus it is a responsibility of GKd not to authorize the use of
   a groupcast key until it knows that all the GKs have that key.

   When a station in the group receives data that has been groupcast to
   the group, if the receiver has the key referenced by the data message
   the receiver decrypts and verifies it. If verification fails or if
   the receiver does not have the required key, the receiver discards
   the data message. Thus whether GKs has been directed to "use" a key
   by GKd is relevant only to transmission, not reception.



2.4 Changes in Group Membership or GKd

   When a new station joins the group, GKd should send that station the
   currently in-use group key and instruct it to use that key and send
   it other keys known to the group members and intended for future use.

   If GKd detects that one or more stations that were members of the
   group are no longer members of the group, it SHOULD generate and
   distribute a new group key to the remaining group members, instruct
   them to use this new key, and delete from them any old keys known to
   the departed group member station(s) or at least instructing them to
   disuse such old keys that are marked for use; however, in the case of
   groups with large and/or highly dynamic membership, where a station
   might frequently leave and then rejoin, it may, as a practical
   matter, be necessary to rekey less frequently.



D. Eastlake                                                     [Page 6]


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   A new group member can become GKd due to the previous GKd leaving the
   group or a configuration change or the like. A GKs MUST NOT use
   keying material set by a station that it determines is not GKd. To
   avoid a gap in service, a station that is not GKd MAY set keying
   material at other stations in the group; however, such a non-GKd
   station cannot set the use flag for any such keying material. It is
   RECOMENDED that the second highest priority station to be GKd set
   such keying material at all other stations in the group. Should a
   station run out of room for keying material, it SHOULD discard keying
   material set by a station with lower priority to be GKd before
   discarding keying material set by a higher priority station and among
   keys set by GKd is SHOULD discard the lest recently used first.



2.5 Group Keying Messages

   Keying messages start with a Version number. This document specifies
   Version zero.

   Keying messages are structured as
      o  a Version number,
      o  a Response flag,
      o  a Key ID length,
      o  the Key ID of a stable key,
      o  a group keying use profile identifier,
      o  possible padding, and finally
      o  an AES key wrapped [RFC5649] [RFC3394] vector of additional
         fields wrapped using the stable key identified and using
         AES-256, as shown in Figure 2.1 below.

   Keying messages are always sent unicast and encrypted and
   authenticated with the appropriate pairwise key, all as further
   specified for the particular use profile. It will typically be
   possible for GKd to calculate the keying message once, including the
   AES wrapping under a stable key, then send that message to various
   GKs using the different pairwise keys for each GKs.















D. Eastlake                                                     [Page 7]


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      +-+-+-+-+-+-+-+-+
      |Ver|R|KeyID1Lng|                  1 byte
      +-+-+-+-+-+-+-+-+...
      | KeyID1  ...                      KeyID1Lngth bytes
      +-+-+-+-+-+-+-+-+...
      | Use Type      |                  1 byte
      +-+-+-+-+-+-+-+-+
      | Pad1 Length   |                  1 byte
      +-+-+-+-+-+-+-+-+...
      | Padding                          Pad1 Length bytes
      +-+-+-+-+-+-+-+-+...
      |AES Wrap Length|                  1 byte
      +-+-+-+-+-+-+-+-+...
      |
      | AES Wrapped Material             Variable size
      |
      +-+-+-+-+-+-+-+-...

                     Figure 2.1. Keying Message Structure

      The fields in Figure 2.1 are as follows:

         Ver - Group Keying protocol version. This document specifies
             version zero.

         R - Response flag. If set to one, indicates a response message.
             If set to zero, indicated a request or no-op message.

         KeyID1Lngth, KeyID1 - KeyID1 identifies the stable AES-256 key
             wrapping key (also known as the Key Encrypting Key (KEK))
             as further specified in the use profile. KeyID1Lngth is a
             byte that gives the length of KeyID1 in bytes as an
             unsigned integer.

         Use Type - Specifies the particular group security use profile
             such as RBridge Extension (Section 3) or IP link
             [TRILLoverIP].

         Pad1 Length, Pad1 - Padding to obscure the non-padded message
             size. Pad1 Length may be from 0 to 255 and gives the length
             of the padding as an unsigned integer. Each byte of padding
             MUST be equal to Pad1 Length. For example, 3 bytes of
             padding with length is 0x03030303.

         AES Wrap Length - An unsigned byte that gives the length of the
             AES Wrapped Material in units of 8 bytes. The length of AES
             key wrapped material is, as specified in [RFC5649], always
             a multiple of 8 bytes (64 bits) and not less than 16 bytes.
             Thus an AES Wrap Length of 0 or 1 is invalid.



D. Eastlake                                                     [Page 8]


INTERNET-DRAFT                                       TRILL: Group Keying


         AES Wrapped Material - The output of the AES Key Wrapping
             operation on the message vector of fields using the
             specified stable key.

   The vector of fields contained within the AES-256 key wrapping is
   specified for the various keying messages in subsections below. The
   contents of this wrapped vector are protected by the AES wrapping as
   well as being authenticated and super-encrypted by the pairwise keyed
   security used for sending the overall keying message. The stable key
   used for AES wrapping MUST be different from the outer message
   pairwise key.

   Each group keying message contains, in the AES wrapped vector of
   fields, a message type and a message ID set by the sender of a
   request.  These fields are returned in the corresponding response to
   assist in the matching of response to requests, except that there is
   no response to the No-Op message.

   If no response is received to a request (other than a No-Op message)
   for an amount of time configurable in milliseconds from 1 to ( 2**15
   - 1 ), the request is re-transmitted with the same message ID.  These
   retries can occur up to a configurable number of times from 1 to 8.
   Unless otherwise provided in the particular use profile, the default
   response delay threshold is 200 milliseconds and the default maximum
   number of retries is 3.

   Keying messages are sent with a priority configurable on a per device
   per use type basis. The default priority is specified in the use
   profile.

   Since the minimum length of the AES Wrapped Material is 16 bytes
   [RFC5649], the minimum valid size of a keying message is 20 bytes,
   even if KeyID1 Length and Pad1 Length are zero. All multi-byte fields
   are in network order, that is, with the most significant byte first.



2.6 Set Key Message

   The structure of the wrapped vector of fields for the Set Key keying
   message is as show in Figure 2.2. A recipient automatically
   determines the overall length provided for this vector of fields
   inside the AES wrapping as a byproduct of the process of AES
   unwrapping [RFC5649].








D. Eastlake                                                     [Page 9]


INTERNET-DRAFT                                       TRILL: Group Keying


      +-+-+-+-+-+-+-+-+
      | Msg Type = 1  |                  1 bytes
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Msg ID                           3 bytes      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Pad2 Length   |                  1 bytes
      +-+-+-+-+-+-+-+-+...
      | Padding                          Pad2 Length bytes
      +-+-+-+-+-+-+-+-+...
      | Other                            Variable size
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Lifetime                      |  2 bytes
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | KeyID2 Length |                  1 byte
      +-+-+-+-+-+-+-+-+
      | KeyID2  ...                      KeyID2 Length bytes
      +-+-+-+-+-+-+-+-+
      | CypherSuiteLng|                  1 byte
      +-+-+-+-+-+-+-+-+
      | CypherSuite ...                  CypherSuiteLng bytes
      +-+-+-+-+-+-+-+-...
      | Key  ...                         Variable size
      +-+-+-+-+-+-+-+-...

                 Figure 2.2. Set Key Message Inner Structure

      The fields are as follows:

         Msg Type = 1 for Set Key message

         Msg ID - A 3 byte quantity to be included in the corresponding
             response message to assist in matching requests and
             responses. Msg ID zero has a special meaning in responses
             and MUST NOT be used in a Set Key message or any other
             group keying request message.

         Pad2 Length, Pad2 - Padding to obscure the size of the unapdded
             AES wrapped data. Pad2 Length may be from 0 to 255 and
             gives the length of the padding as an unsigned integer.
             Each byte of padding MUST be equal to Pad1 Length. For
             example, 2 bytes of padding with length byte is 0x020202.

         Other - Additional information if specified in the use profile.
             If Other information in this message is not mentioned in
             the use profile, there is none and this portion of the
             wrapped information is null. If a use profile specifies
             Other information it must be possible to determine its
             length so that following fields can be properly parsed and
             so that the size of the Key field can be deduced.



D. Eastlake                                                    [Page 10]


INTERNET-DRAFT                                       TRILL: Group Keying


         Lifetime - A 2-byte unsigned integer. After that number of
             seconds plus one second, the key and associated information
             being set MUST be discarded. Unless otherwise specified for
             a particular use profile of this group keying protocol, the
             default Lifetime is 15,000 seconds or a little over four
             hours.

         KeyID2 Length, KeyID2 - KeyID2 identifies the group key and
             associated information being set as further specified in
             the use profile. KeyID2 Length is an unsigned byte that
             gives the length of KeyID2 in bytes.

         CypherSuiteLng, CypherSuite - CypherSuite identifies the cypher
             suite associated with the key being set as further
             specified in the use profile. CypherSuite Length is an
             unsigned byte the gives the length of CypherSuite in bytes.

         Key - This is the actually group shared secret keying material
             being set. Its length is deduced from the overall length of
             the vector of fields (found by the AES unwrap operation)
             and the length of the preceding fields.

   If GKs already has a dynamic key set under KeyID2, the key's value
   and associated cypher suite are compared with those in the Set Key
   messages. If they are the same, the only receiver action is to update
   the Lifetime information associated with KeyID2 and send a Response
   message. If they are different, the lifetime, cypher suite, and key
   (and possibly Other material) are replaced, the use flag is cleared,
   and a Response message sent.



2.7 Use, Delete, Disuse, or Deleted Key Messages

   The structure of the wrapped material for the Use Key, Delete Key,
   and Disuse Key keying messages are the same as each other except for
   the message type. This structure is shown in Figure 2.3















D. Eastlake                                                    [Page 11]


INTERNET-DRAFT                                       TRILL: Group Keying


      +-+-+-+-+-+-+-+-+
      | Msg Type = t  |                  1 byte
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Msg ID                           3 bytes      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Pad2 Length   |                  1 bytes
      +-+-+-+-+-+-+-+-+...
      | Padding                          Pad2 Length bytes
      +-+-+-+-+-+-+-+-+...
      | Other                            Variable size
      +-+-+-+-+-+-+-+-+...
      | KeyID2 Length |                  1 byte
      +-+-+-+-+-+-+-+-+
      | KeyID2  ...                      KeyID2 bytes
      +-+-+-+-+-+-+-+-+

           Figure 2.3. Use, Delete, Disuse, or Deleted Key Message

      The Msg Type field specifies the particular message as follows:

      Msg Type   Message
      --------   ----------
           2     Use Key
           3     Delete Key
           4     Disuse Key
           5     Deleted Key

   The remaining fields are as specified in Section 2.4. KeyID2
   indicates the key to be used, deleted, for which use should cease, or
   which has been deleted, depending on the message type.

   It is RECOMMENDED that these messages be padded so as to be the same
   length as a typical Set Key message.

   The Deleted Key is sent by a station believing itself to be GKd
   instructing some GKs to delete a key.  When a GKs spontaneously
   deletes a key, it sends a Deleted Key message to the station from
   which it received the key. The message types for Delete Key and
   Deleted Key are different to minimize confusion in corner cases such
   as the GKd changing while messages are in flight. The Msg ID used in
   a Deleted Key message is created by the sending GKs from a space of
   Msg IDs associated with that GKs which is independent of the Msg IDs
   used in requests originated by GKd.



2.8 Response Message

   The structure of the wrapped material for the Response group keying
   message is as show below in Figure 2.4. A response message is


D. Eastlake                                                    [Page 12]


INTERNET-DRAFT                                       TRILL: Group Keying


   indicated by the R bit in the first byte of the message outside the
   key wrapping.

   A response MUST NOT be sent due to the receipt of a response. The R
   bit is outside of the key wrapping so that this rule can be enforced
   even in cases of difficulty in unwrapping.

      +-+-+-+-+-+-+-+-+
      | Msg Type = n  |                  1 byte
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Msg ID                           3 bytes      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Pad2 Length   |                  1 bytes
      +-+-+-+-+-+-+-+-+...
      | Padding                          Pad2 Length bytes
      +-+-+-+-+-+-+-+-+...
      | Other                            Variable size
      +-+-+-+-+-+-+-+-+...
      | Response Code |                  1 byte
      +-+-+-+-+-+-+-+-+
      | ReqPartLength |                  1 byte
      +-+-+-+-+-+-+-+-+...
      | Request Part                     ReqPartLenth bytes
      +-+-+-+-+-+-+-+-...

                 Figure 2.4. Response Message Inner Structure

      Except as specified below, the fields are as specified for the Key
      Set message.

         Msg Type, Msg ID - The content of these field is copied from
             the message in reply to which this Response message is sent
             unless there is an error that stops the replying station
             from determining them, in which case the special value zero
             is used for the Msg Type and Msg ID. Errors where the Msg
             Type and ID could not be determined are indicated by a
             Response Code with their high order bit set to one, that
             is, the 0b10000000 bit set.

         Response Code - An unsigned byte giving the response as
             enumerated in Table 2.2 in Section 2.8.1.  Any Response
             Code other than a success indicates that the receiver took
             no action on the request other than sending an error
             Response message.

         ReqPartLength, Request Part: It is usually usefully to include
             some or all of the request in error responses.
             -  If the Response Code high order two bits are zero, the
                request succeeded and ReqPartLength MUST be set to zero
                so Request Part will be null.


D. Eastlake                                                    [Page 13]


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             -  If the Response Code high order two bits are zero one
                (0b01), then there was an error in the part of the
                request inside the AES key wrapping but the unwrap
                process was successful. ReqPartLength is the length of
                the request message material include in the Request Part
                field. The included request material is from the
                unwrapped vector of fields started with the Msg Type
                byte.
             - If the Response Code high order bit is one (the
                0b10000000 is set), then there was an error parsing the
                material outside the AES key wrap or an error in the AES
                unwrapping process. ReqPartLength is the length of the
                request message part included in the Request Part field.
                The included part of the request starts with the first
                byte of the message (the byte containing the version,
                response flag, and KeyID1 Length).



2.8.1 Response Codes

   The high order two bits of the Response Code have meaning as shown in
   Table 2.1.

      Top 2 Bits    Category
      ----------    ----------
          0b00      Success
          0b01      AES wrap contents
          0b10/11   Outside of AES wrap contents

      Response  Response
       Decimal      Hex    Meaning
      --------  --------  ----------
            0       0x00   Success
            1       0x01   Success and the key at an existing key ID was
                                 changed
         2-47  0x02-0x2F   Unassigned
        48-63  0x30-0x3F   Reserved for special success codes defined in
                                 use profiles
           64       0x40   Malformed inner fields (see Note 2 below)
           65       0x41   Unknown or zero Msg Type in a request
           66       0x42   Zero Msg ID in a request
           68       0x43   Invalid length KeyID2
           69       0x44   Unknown KeyID2
           70       0x45   Invalid length CypherSuite
           71       0x46   Unknown CyperSuite
           72       0x47   Bad Key (see Note 3 below)
       73-111  0x49-0x6F   Unassigned
      112-127  0x70-0x7F   Reserved for error codes defined in use
                                 profiles and related to the AES wrapped


D. Eastlake                                                    [Page 14]


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                                 contents
          128       0x80   Malformed message (see Note 1 below)
          129       0x81   Invalid length KeyID1
          130       0x82   Unknown KeyID1
          131       0x83   Unknown Use Type
          131       0x84   AES unwrap fails test 1, see Section 3
                                 [RFC5649]
          132       0x85   AES unwrap fails test 2, see Section 3
                                 [RFC5649]
          133       0x86   AES unwrap fails test 3, see Section 3
                                 [RFC5649]
      134-175  0x86-0x7F   Unassigned
      176-191  0xB0-0xBF   Reserved for error codes defined in use
                                 profiles and related to parts of
                                 message outside the AES wrap contents
          192       0xC0   No keys set
          193       0xC1   Referenced key unknown
          194       0xC2   Referenced key known but use flag not set
      195-255  0xC3-0xFF   Reserved

Response Code Notes:

   Note 1  Message is too short or too long, AES wrapped material is too
           short, Padding bytes are not the required value, or similar
           fundamental message format problems.

   Note 2  The AES wrapped inner vector of fields is too short or too
           long, Padding bytes are not the required value, or similar
           fundamental vector of fields format problems.

   Note 3  Key is not a valid length for CypherSuite or other internal
           checks on key (for example, parity bits in a 64 bit DES key
           (not that you should be using DES)) fail.



2.8 No-Op Message

   The No-Op message is a dummy message intended for use in disguising
   metadata deducable from keying message transmissions. It requires no
   response although a recipient can always decided to send a No-Op
   message to a station from which it has received such a message.

      +-+-+-+-+-+-+-+-+
      | Msg Type = 6  |                  1 byte
      +-+-+-+-+-+-+-+-+
      | Pad2 Length   |                  1 bytes
      +-+-+-+-+-+-+-+-+...
      | Padding                          Pad2 Length bytes
      +-+-+-+-+-+-+-+-...


D. Eastlake                                                    [Page 15]


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                 Figure 2.5. No-Op Message Inner Structure

   The Msg Type is set to 6 to indicate a No-Op message.

   Pad2 Length and Padding are as specified in Section 2.6. It is
   RECOMMENDED that Pad2 Length in a No-Op message be such as to make
   its length confusable with the length of a Set Key message.



2.9 General Security Considerations

   This section gives some general security considerations of this group
   keying protocol as distinguished from security considerations of a
   particular use profile.

   The method by which the stations in the group discover each other is
   specified in the group keying use profile. GKd controls group access
   and generally learns whatever it needs to know about GKs during the
   pairwise authentication and pairwise keying process.

   The group keying provided by this protocol is shared secret keying.
   This means that data messages can only be authenticated as coming
   from some group member but not as coming from a specific group
   member. If this level of authentication is insufficient, GKd can
   simply not set keys or not set them as usable. This will force all
   stations in the group that are configured to use security for multi-
   destination transmissions to the group to serial unicast data to the
   other group members using pairwise keying.

   The content value of padding fields in the Group Keying protocol is
   fixed so that it cannot be used as a covert channel. The length of
   padding could still be so used.



















D. Eastlake                                                    [Page 16]


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3. Extended RBridge Channel Group Keyed Security

   This section specifies a profile of the group keying protocol defined
   in Section 2. This profile provides shared secret keying to secure
   multi-destination Extended RBridge Channel messages [RFC7978].  The
   keys put in place by the group keying protocol are available for use
   as DTLS pre-shared keys with the DTLS and Composite Security of
   multi-destination Extended RBridge Channel messages as specified in
   Section 3.2.

   For this group keying use profile, a group is identified by TRILL
   Data Label (VLAN or FGL [RFC7172]) and consists of the data reachable
   [RFC7780] RBridges with interest in that Data Label. GKd is the
   RBridge in the group that, of those group members supporting the
   Group Keying Protocol, is the highest priority to be a TRILL
   distribution tree root. If not all members of the group support the
   Group Keying Protocol, then there are two cases for multi-destination
   Channel Tunnel RBridge Channel messages:
   (1) If the sender and at least two other group members support the
       Group Keying Protocol, it SHOULD, for efficiency, send a secured
       multi-destination RBridge Channel message to cover the group and
       serially unicast to the group members not supporting the Group
       Keying Protocol.
   (2) In other cases the sender serially transmits the data to the
       group members using pairwise security.



3.1 Transmission of Group Keying Messages

   Keying messages themselves are sent as unicast Extended RBridge
   Channel messages carrying a Group Keying protocol (see Section 5.2)
   RBridge Channel message. They MUST use DTLS Pairwise or Composite
   (STypes 2 or 3) security.

   The RBridge Channel fields profile for this Group Keying Use Type is
   as follows:

      Priority of Group Keying messages for this SHOULD be 6 unless the
            network manager chooses to use a lower priority after
            determining that such lower priority group keying messages
            will yield acceptable performance. Priority 7 SHOULD NOT be
            used as it may cause interference with the establishment and
            maintenance of adjacency.

      Use Type = 1

      KeyID1 Length = 2, KeyID1 is an [RFC5310] key ID.

      CypherSuiteLng = 2, CypherSuite is the cypher suite used in


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            groupcast extended RBridge Channel data messages for the
            corresponding KeyID2. This a DTLS [RFC6347] cypher suite.

      KeyID2 Length = 1, KeyID2 is the index under which a group key is
            set. Group keys are, in effect, indexed by this KeyID2 and
            the nickname of the GKd as used in the Ingress Nickname
            field of the TRILL Header of Group Keying messages.



3.2 Transmission of Protected Multi-destination Data

   Protected Extended RBridge Channel [RFC7978] messages are multicast
   (M bit set to one in the TRILL Header) and set the SType field to a
   new value for "Group Secured" (See Section 5.3). The data is
   formatted as one byte of Key ID followed by data formatted as TLS 1.2
   [RFC5246] application_data using the cyphersuite and keying material
   stored under the Key ID.


































D. Eastlake                                                    [Page 18]


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4. TRILL Over IP Group Keyed Security

   This section specifies a profile of the group keying protocol defined
   in Section 2. This profile provides shared secret keying to secure
   TRILL over IP messages [TRILLoverIP].  The keys put in place by the
   group keying protocol are available for use as IPSEC keys.

   For this group keying use profile, a group is identified by an IP
   multicast address and consists of the adjacent [RFC7177] RBridges
   reachable with that multicast address. GKd is the RBridge in the
   group that, of those group members supporting the Group Keying
   Protocol, has the highest priority to be a TRILL distribution tree
   root. If not all members of the group support the Group Keying
   Protocol, then there are two cases for multi-destination TRILL over
   IP messages:
   (1) If the sender and at least two other group members support the
       Group Keying Protocol, it SHOULD, for efficiency, send a secured
       IPSEC message to cover the group and serially unicast to the
       group members not supporting the Group Keying Protocol.
   (2) In other cases the sender serially transmits the data to the
       group members using pairwise security.



4.1 Transmission of Group Keying Messages
   tbd

      Use Type = 2

   tbd



4.2 Transmission of Protected Multi-destination Data

   tbd
















D. Eastlake                                                    [Page 19]


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5. IANA Considerations

   This section gives IANA Considerations.



5.1 Group Keying Protocol

   IANA is requested to perform the following actions:

      1. Establish a protocol parameters web page for "Group Keying
         Protocol Parameters" with the initial registries on that page
         as specified below in this section.

      2. Establish a "Message Type" registry on the Group Keying
         Protocol Parameters page as follows:

         Registration Procedure: IETF Review

         Reference: [this document]

             Type     Description     Reference
            -------   -----------     ---------------
                  0   Reserved                  [This document]
                  1   Set Key                   [This document]
                  2   Use Key                   [This document]
                  3   Delete Key                [This document]
                  4   Disuse Key                [This document]
                  5   Deleted Key               [This document]
                  6   No-Op                     [This document]
              7-250   Unassigned
            251-254   Reserved for Private Use  [This document]
                255   Reserved                  [This document]

      3. Establish a "Group Keying Use Profile" registry on the Group
         Keying Protocol Parameters page as follows:

         Registration Procedure: IETF Review

         Reference: [This document]

             Profile    Description               Reference
            ---------   -----------               ---------
                   0    Reserved                  [This document]
                   1    Extended RBridge Channel  [This document]
                   2    TRILL over IP             [This document]
               3-250    Unassigned
             251-254    Reserved for Private Use  [This document]
                 255    Reserved                  [This document]



D. Eastlake                                                    [Page 20]


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      4. Establish a "Response Code" registry on the Group Keying
         Protocol Parameters page as show below taking entries from the
         Response Code table in Section 2.8.1 above.  In the table of
         values, the Reference column should be "[This document]" except
         where the Meaning is "Unassigned" or "Reserved".

         Registration Procedure: IETF Review

         Reference: [This document]

         Note: The top two bits of the Response Code indicate a category
         as specified in Section 2.8.1 of [this document].

            Response    Response
             Decimal       Hex     Meaning      Reference
            --------   ---------  -----------   ---------
                  0        0x00    Success      [this document]
                ...         ...    ...
                255        0xFF    Reserved



5.2 Group Keying RBridge Channel Protocol Numbers

   IANA is requested to assign TBD1 as the RBridge Channel protocol
   numbers, from the range assigned by Standards Action, for use when
   the "Group Keying" protocol is transmitted over Extended RBridge
   Channel messages.

   The added RBridge Channel protocols registry entry on the TRILL
   Parameters web page is as follows:

         Protocol  Description       Reference
         --------  --------------    ------------------
           TBD1    Group Keying      Section 2 of [this document]



5.3 Group Secured Extended RBridge Channel SType

   IANA is requested to assign TBD2 as the Group Secured SType in the
   "Extended RBridge Channel Security Types Subregistry" on the TRILL
   Parameters web page as follows:

         SType  Description    Reference
         -----  -------------  ----------
          TBD2  Group Secured  Section 3.2 of [this document]





D. Eastlake                                                    [Page 21]


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6. Security Considerations

   TBD

   See [RFC7457] in connection with TLS and DTLS security.















































D. Eastlake                                                    [Page 22]


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Normative References

   [RFC2119] - BBradner, S., "Key words for use in RFCs to Indicate
         Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119,
         March 1997, <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3394] - Schaad, J. and R. Housley, "Advanced Encryption Standard
         (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
         September 2002, <http://www.rfc-editor.org/info/rfc3394>.

   [RFC5246] - Dierks, T. and E. Rescorla, "The Transport Layer Security
         (TLS) Protocol Version 1.2", RFC 5246, August 2008,
         <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
         and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC
         5310, DOI 10.17487/RFC5310, February 2009, <http://www.rfc-
         editor.org/info/rfc5310>.

   [RFC5649] - Housley, R. and M. Dworkin, "Advanced Encryption Standard
         (AES) Key Wrap with Padding Algorithm", RFC 5649, DOI
         10.17487/RFC5649, September 2009, <http://www.rfc-
         editor.org/info/rfc5649>.

   [RFC5869] - Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-
         Expand Key Derivation Function (HKDF)", RFC 5869, May 2010,
         <http://www.rfc-editor.org/info/rfc5869>.

   [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
         Ghanwani, "Routing Bridges (RBridges): Base Protocol
         Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011,
         <http://www.rfc-editor.org/info/rfc6325>.

   [RFC6347] - Rescorla, E. and N. Modadugu, "Datagram Transport Layer
         Security Version 1.2", RFC 6347, January 2012, <http://www.rfc-
         editor.org/info/rfc6347>.

   [RFC7172] - Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R.,
         and D. Dutt, "Transparent Interconnection of Lots of Links
         (TRILL): Fine-Grained Labeling", RFC 7172, DOI
         10.17487/RFC7172, May 2014, <http://www.rfc-
         editor.org/info/rfc7172>.

   [RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,
         D., and A. Banerjee, "Transparent Interconnection of Lots of
         Links (TRILL) Use of IS-IS", RFC 7176, May 2014,
         <http://www.rfc-editor.org/info/rfc7176>.

   [RFC7177] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H.,
         and V. Manral, "Transparent Interconnection of Lots of Links


D. Eastlake                                                    [Page 23]


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         (TRILL): Adjacency", RFC 7177, DOI 10.17487/RFC7177, May 2014,
         <http://www.rfc-editor.org/info/rfc7177>.

   [RFC7178] - Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
         Ward, "Transparent Interconnection of Lots of Links (TRILL):
         RBridge Channel Support", RFC 7178, DOI 10.17487/RFC7178, May
         2014, <http://www.rfc-editor.org/info/rfc7178>.

   [RFC7780] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
         Ghanwani, A., and S. Gupta, "Transparent Interconnection of
         Lots of Links (TRILL): Clarifications, Corrections, and
         Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,
         <http://www.rfc-editor.org/info/rfc7780>.

   [RFC7978] - Eastlake 3rd, D., Umair, M., and Y. Li, "Transparent
         Interconnection of Lots of Links (TRILL): RBridge Channel
         Header Extension", RFC 7978, DOI 10.17487/RFC7978, September
         2016, <http://www.rfc-editor.org/info/rfc7978>.

   [TRILLoverIP] - M. Cullen, D. Eastlake, M. Zhang, D. Zhang,
         "Transparent Interconnection of Lots of Links (TRILL) over IP",
         draft-ietf-trill-over-ip, work in progress.



Informative References

   [RFC6234] - Eastlake 3rd, D. and T. Hansen, "US Secure Hash
         Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI
         10.17487/RFC6234, May 2011, <http://www.rfc-
         editor.org/info/rfc6234>.

   [RFC7457] - Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
         Known Attacks on Transport Layer Security (TLS) and Datagram
         TLS (DTLS)", RFC 7457, February 2015, <http://www.rfc-
         editor.org/info/rfc7457>.
















D. Eastlake                                                    [Page 24]


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Acknowledgements

   The contributions of the following are hereby gratefully
   acknowledged:

         TBD

   The document was prepared in raw nroff. All macros used were defined
   within the source file.











































D. Eastlake                                                    [Page 25]


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Authors' Addresses

      Donald E. Eastlake, 3rd
      Huawei Technologies
      155 Beaver Street
      Milford, MA 01757 USA

      Phone: +1-508-333-2270
      EMail: d3e3e3@gmail.com











































D. Eastlake                                                    [Page 26]


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Copyright, Disclaimer, and Additional IPR Provisions

   Copyright (c) 2016 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
   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.  The definitive version of
   an IETF Document is that published by, or under the auspices of, the
   IETF. Versions of IETF Documents that are published by third parties,
   including those that are translated into other languages, should not
   be considered to be definitive versions of IETF Documents. The
   definitive version of these Legal Provisions is that published by, or
   under the auspices of, the IETF. Versions of these Legal Provisions
   that are published by third parties, including those that are
   translated into other languages, should not be considered to be
   definitive versions of these Legal Provisions.  For the avoidance of
   doubt, each Contributor to the IETF Standards Process licenses each
   Contribution that he or she makes as part of the IETF Standards
   Process to the IETF Trust pursuant to the provisions of RFC 5378. No
   language to the contrary, or terms, conditions or rights that differ
   from or are inconsistent with the rights and licenses granted under
   RFC 5378, shall have any effect and shall be null and void, whether
   published or posted by such Contributor, or included with or in such
   Contribution.





















D. Eastlake                                                    [Page 27]


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