path: root/doc/rfc/rfc1038.txt

Network Working Group                                       M. St. Johns
Request for Comments: 1038                                          IETF
                                                            January 1988


                    Draft Revised IP Security Option


Status of this Memo

   This RFC is a pre-publication draft of the revised Internet Protocol
   Security Option.  This draft reflects the version as approved by
   the Protocol Standards Steering Group.  It is provided for
   informational purposes only.  The final version of this document will
   be available from Navy Publications and should not differ from
   this document in any major fashion.

   This document will be published as a change to the MIL-STD 1777,
   "Internet Protocol".  Distribution of this memo is unlimited.

9.3.13.1 Internet Options Defined.

   The following internet options are defined:

        CLASS NUMBER LENGTH DESCRIPTION
        _____ ______ ______ ___________

        0      00000   -    End of Option list:  This option occupies
                            only 1 octet; it has no length octet.
        0      00001   -    No Operation:  This option occupies only 1
                            octet; it has no length octet.
        0      00010   var. Basic Security:  Used to carry security
                            level and accrediting authority flags.
        0      00011   var. Loose Source Routing:  Used to route the
                            datagram based on information supplied by
                            the source.
        0      00101   var. Extended Security:  Used to carry additional
                            security information as required by
                            registered authorities.
        0      01001   var. Strict Source Routing:  Used to route the
                            datagram based on information supplied by
                            the source.
        0      00111   var. Record Route:  Used to trace the route a
                            datagram takes.
        0      01000    4   Stream ID:  Used to carry the stream
                            identifier.
        2      00100   var. Internet Timestamp:  Used to accumulate
                            timing information in transit.



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9.3.15.3  DoD Basic Security.

     Option type:  130      Option length: variable; minimum length:  4

   The option identifies the U.S. security level to which the datagram
   is to be protected, and the accrediting authorities whose protection
   rules apply to each datagram.

   The option is used by accredited trusted components of an internet
   to:

     a.  Validate the datagram as appropriate for transmission from the
         source.

     b.  Guarantee that the route taken by the datagram (including the
         destination) is protected to the level required by all
         indicated accrediting authorities.

     c.  Supply common label information required by computer security
         models.

     This option must be copied on fragmentation.  This option appears
     at most once in a datagram.

   The format of this option is as follows:


   +--------------+-----------+-------------+-------------//----------+
   |  10000010    |  XXXXXXXX | SSSSSSSS    |  AAAAAAA[1]    AAAAAAA0 |
   |              |           |             |         [0]             |
   +--------------+-----------+-------------+-------------//----------+
      TYPE = 130   LENGTH      CLASSIFICATION      PROTECTION
                   VARIABLE      PROTECTION         AUTHORITY
                                   LEVEL              FLAGS

                   FIGURE 10-A.  SECURITY OPTION FORMAT

9.3.15.3.1  Length.

   The length of the option is variable.  The minimum length option is
   4.

9.3.15.3.2  Classification Protection Level.

   This field specifies the U.S. classification level to which the
   datagram should be protected.  The information in the datagram should
   be assumed to be at this level until and unless it is regraded in
   accordance with the procedures of all indicated protecting



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   authorities.  This field specifies one of the four U.S.
   classification levels, and is encoded as follows:

                 11011110   -   Top Secret
                 10101101   -   Secret
                 01111010   -   Confidential
                 01010101   -   Unclassified

9.3.15.3.3  Protection Authorities Flags.

   This field indicates the National Access Program(s) with accrediting
   authority whose rules apply to the protection of the datagram.

      a.  Field Length:  This field is variable in length.  The low-
      order bit (Bit 7) of each octet is encoded as "zero" if it is the
      final octet in the field, or as "one" if there are additional
      octets.  Currently, only one octet is needed for this field
      (because there are less than seven authorities), and the final bit
      of the first octet is coded as "zero".

      b.  Source Flags:  The first seven bits (Bits 0 through 6) in each
      octet are source flags which are each associated with an authority
      as indicated below.  The bit corresponding to an authority is
      "one" if the datagram is to be protected in accordance with the
      rules of that authority.

9.3.15.3.4  Usage Rules.

   Use of the option requires that a host be aware of 1) the
   classification level, or levels, at which it is permitted to operate,
   and 2) the protection authorities responsible for its certification.
   The achievement of this is implementation dependent.  Rules for use
   of the option for different types of hosts are given below.

9.3.15.3.4.1  Unclassified Hosts, including gateways.

      a.  Output:  Unclassified hosts may either use or not use the
      option.  If it is used, classification level must be unclassified,
      bit 0 of the accreditation field (GENSER) must be one, and all
      other bits of the accreditation field must be 0.  While use of the
      option is permitted, it is recommended that unclassified hosts
      interested in maximizing interoperability with existing non-
      compliant implementations not use the option.

      b.  Input:  Unclassified hosts should accept for further
      processing IP datagrams without the option.  If the option is
      present on an incoming IP datagram, then the datagram is accepted
      for further processing only if the classification level is



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      unclassified, bit 0 of the accreditation field (GENSER) is one,
      and all other bits of the accreditation field are zero.
      Otherwise, the out-of-range procedure is followed.

9.3.15.3.4.2  Hosts accredited in the Dedicated, System-High, or
Compartmented Modes at a classification level higher than unclassified.

      a.  Output.  The use of the option is mandatory.  The
      classification level should be the dedicated level for dedicated
      hosts and the system-high level for system-high and compartmented
      hosts.  The accrediting authority flags should be one for all
      authorities which have accredited the hosts, and zero for all
      other authorities.

      b.  Input.  If 1) the option is present, 2) the classification
      level matches the host classification level, and 3) the
      accrediting authority flags for all accrediting authorities of the
      receiving host are one, and all others are zero, the IP datagram
      should be accepted for further processing.  Otherwise, the out-
      of-range procedure is followed.

9.3.15.3.4.3  Hosts accredited in the Multi-Level or Controlled Mode for
network transmission.

      a.  Output.  The use of the option is mandatory.  The
      classification level of an IP datagram should be within the range
      of levels for which the host is accredited.  The protection
      authorities flags should be one for all authorities under whose
      rules the datagram should be protected.

      b.  Input.  In the specific case where a multi-level or controlled
      host is accredited to directly interface with an unclassified
      environment, the host may accept IP datagrams without a basic
      security option.  Such datagrams should be assumed to be
      implicitly labelled unclassified, GENSER, and should be so
      labelled explicitly if they are later output.  In all other cases,
      the IP datagrams should have the basic security option on input,
      and the out-of-range procedure should be followed if it is not.

   There are two cases to be considered where the option is present.
   The first case is where the system environment permits the values in
   the option to be trusted to be correct for some range of values; the
   second is where the values cannot be trusted to be correct.  For each
   multi-level or controlled host, every input channel for IP datagrams
   must be considered and classed appropriately.  If a channel does have
   a trusted range, then the values of both the classification level and
   the protection authorities are checked to insure that they fall
   within that range and the range of accredited values for the



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   receiving host.  If within both ranges, the IP datagram is accepted
   for further processing; otherwise the out-of-range procedure is
   followed.  If the label cannot be trusted, then the receiving host
   must possess some accredited means of knowing what the correct
   marking should be (e.g., a trusted channel to a system-high host at a
   known level).  On receipt of an IP datagram, the host compares the
   actual values in the option to the correct values.  If the values
   match, the datagram is accepted for further processing; otherwise,
   the out-of-range procedure is followed.

9.3.15.3.4.4  Out-Of-Range Procedure.

   If an IP datagram is received which does not meet the input
   requirements, then:

      a)  The data field should be overwritten with ones.

      b) If the problem is a missing required Basic or Extended security
      option, an ICMP "parameter problem" message is sent to the
      originating host with the code field set to 1 (one) to indicate
      "missing required option" and the pointer field set to the option
      type of the missing option.  Otherwise, an ICMP "parameter
      problem" message is sent to the originating host with code field
      set to 0 (zero) and with the pointer field pointing to the
      position of the out-of-range security option.

      c) If the receiving host has an interface to a local security
      officer or equivalent, the problem should be identified across
      that interface in an appropriate way.

9.3.15.3.4.5  Trusted Intermediary Procedure.

   Certain devices in the internet may act as intermediaries to validate
   that communications between two hosts are authorized, based on a
   combination of knowledge of the hosts and the values in the IP
   security option.  These devices may receive IP datagrams which are in
   range for the intermediate device, but are either not within the
   acceptable range for the sender, or for the ultimate receiver.  In
   the former case, the datagram should be treated as described above
   for an out-of-range option.  In the latter case, a "destination
   unreachable" ICMP message should be sent, with the code value of 10
   (ten), indicating "Communication with Destination Host
   Administratively Prohibited".








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9.3.15.4  DoD Extended Security Option

    Option type:  133          Option length:  variable

   This option permits additional security related information, beyond
   that present in the Basic Security Option, to be supplied in an IP
   datagram to meet the needs of registered authorities.  If this option
   is required by an authority for a specific system, it must be
   specified explicitly in any Request for Proposal.  It is not
   otherwise required.  This option must be copied on fragmentation.
   This option may appear multiple times within a datagram.

   The format for this option is as follows:

          +------------+-------------+-------------+--------//-------+
          | 10000101   |  000LLLLL   |  AAAAAAAA   |   add sec info  |
          +------------+-------------+-------------+--------//-------+
           type = 133    LENGTH = Var.   ADDITIONAL    ADDITIONAL
                                         SECURITY      SECURITY
                                         INFO          INFO
                                         AUTHORITY
                                         CODE

                               FIGURE 10-B.

9.3.15.4.1  Additional Security Info Authority Code.

   length = 8 bits

   The values of this field are assigned by DCA Code R130, Washington,
   D.C.  20305-2000.  Each value corresponds to a requestor who, once
   assigned, becomes the authority for the remainder of the option
   definition for that value.

9.3.15.4.2  Additional Security Information.

   length - variable

   This field contains any additional security information as specified
   by the authority.











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      BIT
      NUMBER     AUTHORITY

        0        GENSER

        1        SIOP

        2        DSCCS-SPINTCOM

        3        DSCCS-CRITICOM

      4-7        Unassigned

   AUTHORITY                                 SOURCE OF ANNEX DESCRIBING
                                             CURRENT CODING OF ADDITIONAL
                                             SECURITY INFORMATION

   GENSER
   National Access Program, less SIOP        Defense Communications
                                             Agency
                                             ATTN:  Code R130
                                             Washington, DC  20305

   SIOP
   National Access Program                   Department of Defense
                                             Organization of the
                                             Joint Chiefs of Staff
                                             Attn: J6T
                                             Washington, DC

   DSCCS-SPINTCOM
   National Access Program                   Defense Intelligence Agency
                                             Attn: DSE4
                                             Bolling AFB, MD

   DSCCS-CRITICOM
   National Access Program                   National Security Agency
                                             9800 Savage Road
                                             Attn: T03
                                             Ft. Meade, MD 20755-6000











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