Network                                                       P. Wouters
Internet-Draft                                                     Aiven
Updates: 7296 (if approved)                                    S. Prasad
Intended status: Standards Track                                 Red Hat
Expires: 25 September 2022                                 24 March 2022

            Labeled IPsec Traffic Selector support for IKEv2


   This document defines a new Traffic Selector (TS) Type for Internet
   Key Exchange version 2 to add support for negotiating Mandatory
   Access Control (MAC) security labels as a traffic selector of the
   Security Policy Database (SPD).  Security Labels for IPsec are also
   known as "Labeled IPsec".  The new TS type is TS_SECLABEL, which
   consists of a variable length opaque field specifying the security
   label.  This document updates the IKEv2 TS negotiation specified in
   RFC 7296 Section 2.9.

Status of This Memo

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   This Internet-Draft will expire on 25 September 2022.

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   extracted from this document must include Revised BSD License text as
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Traffic Selector clarification  . . . . . . . . . . . . .   3
     1.3.  Traffic Selector update . . . . . . . . . . . . . . . . .   4
   2.  TS_SECLABEL Traffic Selector Type . . . . . . . . . . . . . .   4
     2.1.  TS_SECLABEL payload format  . . . . . . . . . . . . . . .   4
     2.2.  TS_SECLABEL properties  . . . . . . . . . . . . . . . . .   4
   3.  Traffic Selector negotiation  . . . . . . . . . . . . . . . .   5
     3.1.  Example TS negotiation  . . . . . . . . . . . . . . . . .   6
     3.2.  Considerations for using multiple TS_TYPEs in a TS  . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Implementation Status . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Libreswan . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   In computer security, Mandatory Access Control usually refers to
   systems in which all subjects and objects are assigned a security
   label.  A security label is comprised of a set of security
   attributes.  The security labels along with a system authorization
   policy determine access.  Rules within the system authorization
   policy determine whether the access will be granted based on the
   security attributes of the subject and object.

   Traditionally, security labels used by Multilevel Systems (MLS) are
   comprised of a sensitivity level (or classification) field and a
   compartment (or category) field, as defined in [FIPS188] and
   [RFC5570].  As MAC systems evolved, other MAC models gained in
   popularity.  For example, SELinux, a Flux Advanced Security Kernel
   (FLASK) implementation, has security labels represented as colon-
   separated ASCII strings composed of values for identity, role, and
   type.  The security labels are often referred to as security

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   Traffic Selector (TS) payloads specify the selection criteria for
   packets that will be forwarded over the newly set up IPsec SA as
   enforced by the Security Policy Database (SPD, see [RFC4301]).  This
   document updates the Traffic Selector negotiation specified in
   Section 2.9 of [RFC7296].

   This document specifies a new Traffic Selector Type TS_SECLABEL for
   IKEv2 that can be used to negotiate security labels as additional
   selectors for the Security Policy Database (SPD) to further restrict
   the type of traffic allowed to be sent and received over the IPsec

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.2.  Traffic Selector clarification

   The negotiation of Traffic Selectors is specified in Section 2.9 of
   [RFC7296] where it defines two TS Types (TS_IPV4_ADDR_RANGE and
   TS_IPV6_ADDR_RANGE).  The Traffic Selector payload format is
   specified in Section 3.13 of [RFC7296].  However, the term Traffic
   Selector is used to denote the traffic selector payloads and
   individual traffic selectors of that payload.  Sometimes the exact
   meaning can only be learned from context or if the item is written in
   plural ("Traffic Selectors" or "TSs").  This section clarifies these
   terms as follows:

   A Traffic Selector (no acronym) is one selector for traffic of a
   specific Traffic Selector Type (TS_TYPE).  For example a Traffic
   Selector of TS_TYPE TS_IPV4_ADDR_RANGE for UDP traffic in the IP
   network covering all ports, is denoted as (17, 0,

   A Traffic Selector payload (TS) is a set of one or more Traffic
   Selectors of the same or different TS_TYPEs, but MUST include at
   least one TS_TYPE of TS_IPV4_ADDR_RANGE or TS_IPV6_ADDR_RANGE.  For
   example, the above Traffic Selector by itself in a TS payload is
   denoted as TS((17, 0,

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1.3.  Traffic Selector update

   The negotiation of Traffic Selectors is specified in Section 2.9 of
   [RFC7296] and states that the TSi/TSr payloads MUST contain at least
   one Traffic Selector type.  This document updates the text to mean
   that the TSi/TSr payloads MUST contain at least one Traffic Selector
   of type TS_IPV4_ADDR_RANGE or TS_IPV6_ADDR_RANGE, as other Traffic
   Selector types can be defined that are complimentary to these Traffic
   Selector Types and cannot be selected on their own without
   TS_IPV4_ADDR_RANGE or TS_IPV6_ADDR_RANGE.  The below defined
   TS_SECLABEL Traffic Selector Type is an example of this.

2.  TS_SECLABEL Traffic Selector Type

   This document defines a new TS Type, TS_SECLABEL that contains a
   single new opaque Security Label.

2.1.  TS_SECLABEL payload format

                           1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      |   TS Type     |    Reserved   |       Selector Length         |
      |                                                               |
      ~                         Security Label*                       ~
      |                                                               |

                  Figure 1: Labeled IPsec Traffic Selector

   *Note: All fields other than TS Type and Selector Length depend on
   the TS Type.  The fields shown is for TS Type TS_SECLABEL, the
   selector this document defines.

   *  TS Type (one octet) - Set to 10 for TS_SECLABEL,

   *  Selector Length (2 octets, unsigned integer) - Specifies the
      length of this Traffic Selector substructure including the header.

   *  Security Label - An opaque byte stream of at least one octet.

2.2.  TS_SECLABEL properties

   The TS_SECLABEL Traffic Selector Type does not support narrowing or
   wildcards.  It MUST be used as an exact match value.

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   The Security Label contents are opaque to the IKE implementation.
   That is, the IKE implementation might not have any knowledge of the
   meaning of this selector, other than as a type and opaque value to
   pass to the SPD.

   A zero length Security Label MUST NOT be used.  If a received TS
   payload contains a TS_TYPE of TS_SECLABEL with a zero length Security
   Label, that specific Traffic Selector MUST be ignored.  If no other
   Traffic Selector of TS_TYPE TS_SECLABEL can be selected, a
   TS_UNACCEPTABLE Error Notify message MUST be returned.  A zero length
   Security Label MUST NOT be interpreted as a wildcard security label.

   If multiple Security Labels are allowed for a given IP protocol,
   start and end address/port match, the initiator includes all of the
   acceptable TS_SECLABEL's and the responder MUST select one of them.

   If the Security Label traffic selector is optional from a
   configuration point of view, the initiator will have to choose which
   TS payload to attempt first.  If it includes the Security Label and
   receives a TS_UNACCEPTABLE, it can attempt a new Child SA negotiation
   without that Security Label.

   A responder that selected a TS with TS_SECLABEL MUST use the Security
   Label for all selector operations on the resulting TS.  It MUST NOT
   select a TS_SECLABEL without using the specified Security Label, even
   if it deems the Security Label optional, as the initiator has
   indicated (and expects) that Security Label will be set for all
   traffic matching the negotiated TS.

3.  Traffic Selector negotiation

   This document updates the [RFC7296] specification as follows:

   Each TS payload (TSi and TSr) MUST contain at least one TS_TYPE of

   Each TS payload (TSi or TSr) MAY contain one or more other TS_TYPEs,
   such as TS_SECLABEL.

   A responder MUST create each TS response by creating one of more
   (narrowed or not) TS_IPV4_ADDR_RANGE or TS_IPV6_ADDR_RANGE entries,
   plus one of each further TS_TYPE present in the offered TS by the
   initiator.  If this is not possible, it MUST return a TS_UNACCEPTABLE
   Error Notify payload.

   If a specific TS_TYPE (other than TS_IPV4_ADDR_RANGE or
   TS_IPV6_ADDR_RANGE which are mandatory) is deemed optional, the
   initiator SHOULD first try to negotiate the Child SA with the TS

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   payload including the optional TS_TYPE.  Upon receiving
   TS_UNACCEPTABLE, it SHOULD attempt a new Child SA negotiation using
   the same TS but without the optional TS_TYPE.

3.1.  Example TS negotiation

   An initiator could send:

         TSi = ((17,24233,198.51.12-198.51.12),
                TS_SECLABEL1, TS_SECLABEL2)

         TSr = ((17,53,,
                TS_SECLABEL1, TS_SECLABEL2)

                  Figure 2: initiator TS payloads example

   The responder could answer with the following example:

         TSi = ((0,0,198.51.0-198.51.255),

         TSr = (((0,0,,

                  Figure 3: responder TS payloads example

3.2.  Considerations for using multiple TS_TYPEs in a TS

   It would be unlikely that the traffic for TSi and TSr would have a
   different Security Label, but this specification does allow this to
   be specified.  If the initiator does not support this, and wants to
   prevent the responder from picking different labels for the TSi / TSr
   payloads, it should attempt a Child SA negotiation with only the
   first Security Label first, and upon failure retry a new Child SA
   negotiation with only the second Security Label.

   If different IP ranges can only use different specific Security
   Labels, than these should be negotiated in two different Child SA
   negotiations.  If in the example above, the initiator only allows with TS_SECLABEL1, and 198.51.0/24 with TS_SECLABEL2,
   than it MUST NOT combine these two ranges and security labels into
   one Child SA negotiation.

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   The mechanism of narrowing of Traffic Selectors with
   TS_IPV4_ADDR_RANGE and TS_IPV6_ADDR_RANGE does not apply to
   TS_SECLABEL as the Security Label itself is not interpreted and
   cannot be narrowed.  It MUST be matched exactly.  Since a rekey MUST
   NOT narrow down the Traffic Selectors narrower than the scope
   currently in use, the only valid choice of TS_SECLABEL for a rekey is
   the identical TS_SECLABEL that is in use by the Child SA being
   rekeyed.  If the TS_LABEL is missing from the TS during the rekey
   negotiation, the negotiation MUST fail with TS_UNACCEPTABLE.

4.  Security Considerations

   It is assumed that the Security Label can be matched by the IKE
   implementation to its own configured value, even if the IKE
   implementation itself cannot interpret the Security Label value.

   A packet that matches an SPD entry for all components except the
   Security Label would be treated as "not matching".  If no other SPD
   entries match, the (mis-labeled) traffic might end up being
   transmitted in the clear.  It is presumed that other Mandatory Access
   Control methods are in place to prevent mis-labeled traffic from
   reaching the IPsec subsystem, or that the IPsec subsystem itself
   would install a REJECT/DISCARD rule in the SPD to prevent unlabeled
   traffic otherwise matching a labeled security SPD rule from being
   transmitted without IPsec protection.

5.  IANA Considerations

   This document defines one new entry in the IKEv2 Traffic Selector
   Types registry:

   [Note to RFC Editor (please remove before publication): This value
   has already bee added via Early Allocation.

      Value   TS Type                      Reference
      -----   ---------------------------  -----------------
      10     TS_SECLABEL   [this document]

                                  Figure 4

6.  Implementation Status

   [Note to RFC Editor: Please remove this section and the reference to
   [RFC7942] before publication.]

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC7942].

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   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may

   According to [RFC7942], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

   Authors are requested to add a note to the RFC Editor at the top of
   this section, advising the Editor to remove the entire section before
   publication, as well as the reference to [RFC7942].

6.1.  Libreswan

   Organization:  The Libreswan Project


   Description:  Implementation has been released as part of libreswan
      version 4.4.

   Level of maturity:  beta

   Coverage:  Implements the entire draft using SElinux based labels

   Licensing:  GPLv2

   Implementation experience:  No interop testing has been done yet.
      The code works as proof of concept, but is not yet production
      ready when using multiple different labels with on-demand kernel

   Contact:  Libreswan Development:

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7.  Acknowledgements

   A large part of the introduction text was taken verbatim from
   [draft-jml-ipsec-ikev2-security-label] whose authors are J Latten, D.
   Quigley and J.  Lu.  Valery Smyslov provided valuable input regarding
   IKEv2 Traffic Selector semantics.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

8.2.  Informative References

              Latten, J., Quigley, D., and J. Lu, "Security Label
              Extension to IKE", 28 January 2011.

   [FIPS188]  NIST, "National Institute of Standards and Technology,
              "Standard Security Label for Information Transfer"",
              Federal Information Processing Standard (FIPS) Publication
              188, September 1994,

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <>.

   [RFC5570]  StJohns, M., Atkinson, R., and G. Thomas, "Common
              Architecture Label IPv6 Security Option (CALIPSO)",
              RFC 5570, DOI 10.17487/RFC5570, July 2009,

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   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,

Authors' Addresses

   Paul Wouters

   Sahana Prasad
   Red Hat

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