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Versions: 00 01                                                         
netmod                                                     O. G. D. Dios
Internet-Draft                                                S. Barguil
Intended status: Standards Track                              Telefonica
Expires: 31 December 2022                                   M. Boucadair
                                                                  Orange
                                                            29 June 2022


        Extensions to the Access Control Lists (ACLs) YANG Model
                      draft-dbb-netmod-acl-01

Abstract

   RFC 8519 defines a YANG data model for Access Control Lists (ACLs).
   This document discusses a set of extensions that fix many of the
   limitations of the ACL model as initially defined in RFC 8519.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Network Modeling
   Working Group mailing list (netmod@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/netmod/.

   Source for this draft and an issue tracker can be found at
   https://github.com/oscargdd/draft-dbb-netmod-enhanced-acl.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on 31 December 2022.

Copyright Notice

   Copyright (c) 2022 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 (https://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
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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Terminology
   3.  Problem Statement & Gap Analysis
     3.1.  Suboptimal Configuration: Lack of Manipulating Lists of
           Prefixes
     3.2.  Manageability: Impossibility to Use Aliases or Defined Sets
     3.3.  Bind ACLs to Devices, Not Only Interfaces
     3.4.  Partial or Lack of IPv4/IPv6 Fragment Handling
     3.5.  Suboptimal TCP Flags Handling
     3.6.  Rate-Limit Action
     3.7.  Payload-based Filtering
     3.8.  Reuse the ACLs Content Across Several Devices
   4.  Overall Module Structure
     4.1.  Enhanced ACL
     4.2.  Defined sets
     4.3.  TCP Flags Handling
     4.4.  Fragments Handling
     4.5.  Rate-Limit Traffic
   5.  YANG Modules
     5.1.  Enhanced ACL
   6.  Security Considerations (TBC)
   7.  IANA Considerations
     7.1.  URI Registration
     7.2.  YANG Module Name Registration
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  Acknowledgements
   Authors' Addresses

1.  Introduction

   [RFC8519] defines Acces control lists (ACLs) as a user-ordered set of
   filtering rules.  The model targets the configuration of the
   filtering behaviour of a device.  However, the model structure, as
   defined in [RFC8519], suffers from a set of limitations.  This
   document describes these limitations and proposes an enhanced ACL
   structure.  The YANG module in this document is solely based on
   augmentations to the ACL YANG module defined in [RFC8519].

   The motivation of such enhanced ACL structure is discussed in detail
   in Section 3.

   When managing ACLs, it is common for network operators to group
   matching elements in pre-defined sets.  The consolidation into
   matches allows reducing the number of rules, especially in large
   scale networks.  If it is needed, for example, to find a match
   against 100 IP addresses (or prefixes), a single rule will suffice
   rather than creating individual Access Control Entries (ACEs) for
   each IP address (or prefix).  In doing so, implementations would
   optimize the performance of matching lists vs multiple rules
   matching.

   The enhanced ACL structure is also meant to facilitate the management
   of network operators.  Instead of entering the IP address or port
   number literals, using user-named lists decouples the creation of the
   rule from the management of the sets.  Hence, it is possible to
   remove/add entries to the list without redefining the (parent) ACL
   rule.

   In addition, the notion of Access Control List (ACL) and defined sets
   is generalized so that it is not device-specific as per [RFC8519].
   ACLs and defined sets may be defined at network / administrative
   domain level and associated to devices.  This approach facilitates
   the reusability across multiple network elements.  For example,
   managing the IP prefix sets from a network level makes it easier to
   maintain by the security groups.

   Network operators maintain sets of IP prefixes that are related to
   each other, e.g., deny-lists or accept-lists that are associated with
   those provided by a VPN customer.  These lists are maintained and
   manipulated by security expert teams.

   Note that ACLs are used locally in devices but are triggered by other
   tools such as DDoS mitigation [RFC9132] or BGP Flow Spec [RFC8955]
   [RFC8956].  Therefore, supporting means to easily map to the
   filtering rules conveyed in messages triggered by hese tools is
   valuable from a network operation standpoint.

2.  Terminology

   The keywords *MUST*, *MUST NOT*, *REQUIRED*, *SHALL*, *SHALL NOT*,
   *SHOULD*, *SHOULD NOT*, *RECOMMENDED*, *MAY*, and *OPTIONAL*, when
   they appear in this document, are to be interpreted as described in
   [RFC2119].

   The terminology for describing YANG modules is defined in [RFC7950].
   The meaning of the symbols in the tree diagrams is defined in
   [RFC8340].

   In adition to the terms defined in [RFC8519], this document makes use
   of the following terms:

   *  Defined set: Refers to reusable description of one or multiple
      information elements (e.g., IP address, IP prefix, port number,
      ICMP type).

3.  Problem Statement & Gap Analysis

3.1.  Suboptimal Configuration: Lack of Manipulating Lists of Prefixes

   IP prefix related data nodes, e.g., "destination-ipv4-network" or
   "destination-ipv6-network", do not allow manipulating a list of IP
   prefixes, which may lead to manipulating large files.  The same issue
   is encountered when ACLs have to be in place to mitigate DDoS attacks
   (e.g., [RFC9132] when a set of sources are involved in such an
   attack.  The situation is even worse when both a list of sources and
   destination prefixes are involved.

   Figure 1 shows an example of the required ACL configuration for
   filtering traffic from two prefixes.

   {
     "ietf-access-control-list:acls": {
       "acl": [
         {
           "name": "first-prefix",
           "type": "ipv6-acl-type",
           "aces": {
             "ace": [
               {
                 "name": "my-test-ace",
                 "matches": {
                   "ipv6": {
                     "destination-ipv6-network":
                       "2001:db8:6401:1::/64",
                     "source-ipv6-network":
                       "2001:db8:1234::/96",
                     "protocol": 17,
                     "flow-label": 10000
                   },
                   "udp": {
                     "source-port": {
                       "operator": "lte",
                       "port": 80
                     },
                     "destination-port": {
                       "operator": "neq",
                       "port": 1010
                     }
                   }
                 },
                 "actions": {
                   "forwarding": "accept"
                 }
               }
             ]
           }
         },
         {
           "name": "second-prefix",
           "type": "ipv6-acl-type",
           "aces": {
             "ace": [
               {
                 "name": "my-test-ace",
                 "matches": {
                   "ipv6": {
                     "destination-ipv6-network":
                       "2001:db8:6401:c::/64",
                     "source-ipv6-network":
                       "2001:db8:1234::/96",
                     "protocol": 17,
                     "flow-label": 10000
                   },
                   "udp": {
                     "source-port": {
                       "operator": "lte",
                       "port": 80
                     },
                     "destination-port": {
                       "operator": "neq",
                       "port": 1010
                     }
                   }
                 },
                 "actions": {
                   "forwarding": "accept"
                 }
               }
             ]
           }
         }
       ]
     }
   }

      Figure 1: Example Illustrating Sub-optimal Use of the ACL Model
                             with a Prefix List

   Such configuration is suboptimal for both: - Network controllers that
   need to manipulate large files.  All or a subset fo this
   configuration will need to be passed to the undelrying network
   devices. - Devices may receive such confirguration and thus will need
   to maintain it locally.

   (Figure 2 depicts an example of an optimized strcuture:

   {
     "ietf-access-control-list:acls": {
       "acl": [
         {
           "name": "prefix-list-support",
           "type": "ipv6-acl-type",
           "aces": {
             "ace": [
               {
                 "name": "my-test-ace",
                 "matches": {
                   "ipv6": {
                     "destination-ipv6-network": [
                       "2001:db8:6401:1::/64",
                       "2001:db8:6401:c::/64"
                     ],
                     "source-ipv6-network":
                       "2001:db8:1234::/96",
                     "protocol": 17,
                     "flow-label": 10000
                   },
                   "udp": {
                     "source-port": {
                       "operator": "lte",
                       "port": 80
                     },
                     "destination-port": {
                       "operator": "neq",
                       "port": 1010
                     }
                   }
                 },
                 "actions": {
                   "forwarding": "accept"
                 }
               }
             ]
           }
         }
       ]
     }
   }

      Figure 2: Example Illustrating Optimal Use of the ACL Model in a
                              Network Context.

3.2.  Manageability: Impossibility to Use Aliases or Defined Sets

   The same approach as the one discussed for IP prefixes can be
   generalized by introduing the concept of "aliases" or "defined sets".

   The defined sets are reusable definitions across several ACLs.  Each
   category is modelled in YANG as a list of parameters related to the
   class it represents.  The following sets can be considered:

   *  Prefix sets: Used to create lists of IPv4 or IPv6 prefixes.

   *  Protocol sets: Used to create a list of protocols.

   *  Port number sets: Used to create lists of TCP or UDP port values
      (or any other transport protocol that makes uses of port numbers).
      The identity of the protcols is identified by the protocol set, if
      present.  Otherwise, a set apply to any protocol.

   *  ICMP sets: Uses to create lists of ICMP-based filters.  This
      applies only when the protocol is set to ICMP or ICMPv6.

   A candidate structure is shown in Figure 3:

        +--rw defined-sets
        |  +--rw prefix-sets
        |  |  +--rw prefix-set* [name mode]
        |  |     +--rw name        string
        |  |     +--rw ip-prefix*   inet:ip-prefix
        |  +--rw port-sets
        |  |  +--rw port-set* [name]
        |  |     +--rw name    string
        |  |     +--rw port*   inet:port-number
        |  +--rw protocol-sets
        |  |  +--rw protocol-set* [name]
        |  |     +--rw name             string
        |  |     +--rw protocol-name*   identityref
        |  +--rw icmp-type-sets
        |     +--rw icmp-type-set* [name]
        |        +--rw name     string
        |        +--rw types* [type]
        |           +--rw type              uint8
        |           +--rw code?             uint8
        |           +--rw rest-of-header?   binary

                    Figure 3: Examples of Defined Sets.

3.3.  Bind ACLs to Devices, Not Only Interfaces

   In the context of network management, an ACL may be enforced in many
   network locations.  As such, the ACL module should allow binding an
   ACL to multiple devices, not only (abstract) interfaces.

   The ACL name must, thus, be unique at the scale of the network, but
   still the same name may be used in many devices when enforcing node-
   specific ACLs.

3.4.  Partial or Lack of IPv4/IPv6 Fragment Handling

   [RFC8519] does not support fragment handling capability for IPv6 but
   offers a partial support for IPv4 by means of 'flags'.  Nevertheless,
   the use of 'flags' is problematic since it does not allow a bitmask
   to be defined.  For example, setting other bits not covered by the
   'flags' filtering clause in a packet will allow that packet to get
   through (because it won't match the ACE).

   Defining a new IPv4/IPv6 matching field called 'fragment' is thus
   required to efficiently handle fragment-related filtering rules.

3.5.  Suboptimal TCP Flags Handling

   [RFC8519] allows including flags in the TCP match fields, however
   that strcuture does not support matching operations as those
   supported in BGP Flow Spec.  Definig this field to be defined as a
   flag bitmask together with a set of operations is meant to
   efficiently handle TCP flags filtering rules.

3.6.  Rate-Limit Action

   [RFC8519] specifies that forwarding actions can be 'accept' (i.e.,
   accept matching traffic), 'drop' (i.e., drop matching traffic without
   sending any ICMP error message), or 'reject' (i.e., drop matching
   traffic and send an ICMP error message to the source).  Howover,
   there are situations where the matching traffic can be accepted, but
   with a rate-limit policy.  Such capability is not currently supported
   by [RFC8519].

3.7.  Payload-based Filtering

   Some transport protocols use existing protocols (e.g., TCP or UDP) as
   substrate.  The match criteria for such protocols may rely upon the
   'protocol' under 'l3', TCP/UDP match criteria, part of the TCP/UDP
   payload, or a combination thereof.  [RFC8519] does not support
   matching based on the payload.

   Likewise, the current version of the ACL model does not support
   filetering of encapsulated traffic.

3.8.  Reuse the ACLs Content Across Several Devices

   Having a global network view of the ACLs is highly valuable for
   service providers.  An ACL could be defined and applied following the
   hierarchy of the network topology.  So, an ACL can be defined at the
   network level and, then, that same ACL can be used (or referenced to)
   in several devices (including termination points) within the same
   network.

   This network/device ACLs differentiation introduces several new
   requirements, e.g.:

   *  An ACL name can be used at both network and device levels.

   *  An ACL content updated at the network level should imply a
      transaction that updates the relevant content in all the nodes
      using this ACL.

   *  ACLs defined at the device level have a local meaning for the
      specific node.

   *  A device can be associated with a router, a VRF, a logical system,
      or a virtual node.  ACLs can be applied in physical and logical
      infrastructure.

4.  Overall Module Structure

4.1.  Enhanced ACL

   module: ietf-acl-enh
     augment /ietf-acl:acls/ietf-acl:acl:
       +--rw defined-sets
          +--rw ipv4-prefix-sets
          |  +--rw prefix-set* [name]
          |     +--rw name           string
          |     +--rw description?   string
          |     +--rw prefix*        inet:ipv4-prefix
          +--rw ipv6-prefix-sets
          |  +--rw prefix-set* [name]
          |     +--rw name           string
          |     +--rw description?   string
          |     +--rw prefix*        inet:ipv6-prefix
          +--rw port-sets
          |  +--rw port-set* [name]
          |     +--rw name    string
          |     +--rw port* [id]
          |        +--rw id                              string
          |        +--rw (port)?
          |           +--:(port-range-or-operator)
          |              +--rw port-range-or-operator
          |                 +--rw (port-range-or-operator)?
          |                    +--:(range)
          |                    |  +--rw lower-port    inet:port-number
          |                    |  +--rw upper-port    inet:port-number
          |                    +--:(operator)
          |                       +--rw operator?     operator
          |                       +--rw port          inet:port-number
          +--rw protocol-sets
          |  +--rw protocol-set* [name]
          |     +--rw name        string
          |     +--rw protocol*   union
          +--rw icmp-type-sets
             +--rw icmp-type-set* [name]
                +--rw name     string
                +--rw types* [type]
                   +--rw type              uint8
                   +--rw code?             uint8
                   +--rw rest-of-header?   binary
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches:
       +--rw (payload)?
          +--:(prefix-pattern)
             +--rw prefix-pattern {match-on-payload}?
                +--rw offset?       identityref
                +--rw offset-end?   uint64
                +--rw operator?     operator
                +--rw prefix?       binary
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches/ietf-acl:l3/ietf-acl:ipv4:
       +--rw ipv4-fragment
       |  +--rw operator?   operator
       |  +--rw type?       fragment-type
       +--rw source-ipv4-prefix-list?        leafref
       +--rw destination-ipv4-prefix-list?   leafref
       +--rw next-header-set?                leafref
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches/ietf-acl:l3/ietf-acl:ipv6:
       +--rw ipv6-fragment
       |  +--rw operator?   operator
       |  +--rw type?       fragment-type
       +--rw source-ipv6-prefix-list?        leafref
       +--rw destination-ipv6-prefix-list?   leafref
       +--rw protocol-set?                   leafref
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches/ietf-acl:l4/ietf-acl:tcp:
       +--rw flags-bitmask
       |  +--rw operator?   operator
       |  +--rw bitmask?    uint16
       +--rw source-tcp-port-set?
       |       -> ../../../../defined-sets/port-sets/port-set/name
       +--rw destination-tcp-port-set?
               -> ../../../../defined-sets/port-sets/port-set/name
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches/ietf-acl:l4/ietf-acl:udp:
       +--rw source-udp-port-set?
       |       -> ../../../../defined-sets/port-sets/port-set/name
       +--rw destination-udp-port-set?
               -> ../../../../defined-sets/port-sets/port-set/name
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:matches/ietf-acl:l4/ietf-acl:icmp:
       +--rw icmp-set?   leafref
     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace
               /ietf-acl:actions:
       +--rw rate-limit?   decimal64

                        Figure 4: Enhanced ACL tree

4.2.  Defined sets

   The augmented ACL structure includes several containers to manage
   reusable sets of elements that can be matched in an ACL entry.  Each
   set is uniquely identified by a name, and can be called from the
   relevant entry.  The following sets are defined:

   *  IPv4 Prefix set: It contains a list of IPv4 prefixes.  A match
      will be considered if the IP address (source or destination,
      depending on the ACL entry) is contained in any of the prexifes.

   *  IPv6 Prefix set: It contains a list of IPv6 prefixes.  A match
      will be considered if the IP address (source or destination,
      depending on the ACL entry) is contained in any of the prexifes.

   *  Port sets: It contains a list of port numbers to be used in TCP /
      UDP entries.  The ports can be individual port numbers, a range of
      ports, and an operation.

   *  Protocol sets: It contains a list of protocol values.  Each
      protocol can be identified either by a number (e.g., 17) or a name
      (e.g., UDP).

   *  ICMP sets: It contains a list of ICMP types, each of them
      identified by a type value, optionally the code and the rest of
      the header.

4.3.  TCP Flags Handling

   The augmented ACL structure includes a new leaf 'flags-bitmask' to
   better handle flags.

   Clients that support both 'flags-bitmask' and 'flags' matching fields
   MUST NOT set these fields in the same request.

   Figure 5 shows an example of a request to install a filter to discard
   incoming TCP messages having all flags unset.

     {
        "ietf-access-control-list:acls": {
          "acl": [{
            "name": "tcp-flags-example",
            "aces": {
              "ace": [{
                "name": "null-attack",
                "matches": {
                  "tcp": {
                    "flags-bitmask": {
                      "operator": "not any",
                      "bitmask": 4095
                    }
                  }
                },
                "actions": {
                  "forwarding": "drop"
                }
              }]
            }
          }]
        }
      }

             Figure 5: Example to Deny TCP Null Attack Messages

4.4.  Fragments Handling

   The augmented ACL structure includes a new leaf 'fragment' to better
   handle fragments.

   Clients that support both 'fragment' and 'flags' matching fields MUST
   NOT set these fields in the same request.

   Figure 6 shows the content of a POST request to allow the traffic
   destined to 198.51.100.0/24 and UDP port number 53, but to drop all
   fragmented packets.  The following ACEs are defined (in this order):

   *  "drop-all-fragments" ACE: discards all fragments.

   *  "allow-dns-packets" ACE: accepts DNS packets destined to
      198.51.100.0/24.

   {
        "ietf-access-control-list:acls": {
          "acl": [
            {
              "name": "dns-fragments",
              "type": "ipv4-acl-type",
              "aces": {
                "ace": [
                  {
                    "name": "drop-all-fragments",
                    "matches": {
                      "ipv4": {
                        "ipv4-fragment": {
                          "operator": "match",
                          "type": "isf"
                        }
                      }
                    },
                    "actions": {
                      "forwarding": "drop"
                    }
                  },
                  {
                    "name": "allow-dns-packets",
                    "matches": {
                      "ipv4": {
                        "destination-ipv4-network": "198.51.100.0/24"
                      },
                      "udp": {
                        "destination-port": {
                          "operator": "eq",
                          "port": 53
                        }
                      },
                      "actions": {
                        "forwarding": "accept"
                      }
                    }
                  }
                ]
              }
            }
          ]
        }
      }

         Figure 6: Example Illustrating Canddiate Filtering of IPv4
                            Fragmented Packets.

   Figure 7 shows an example of the body of a POST request to allow the
   traffic destined to 2001:db8::/32 and UDP port number 53, but to drop
   all fragmented packets.  The following ACEs are defined (in this
   order):

   *  "drop-all-fragments" ACE: discards all fragments (including atomic
      fragments).  That is, IPv6 packets that include a Fragment header
      (44) are dropped.

   *  "allow-dns-packets" ACE: accepts DNS packets destined to
      2001:db8::/32.

       {
        "ietf-access-control-list:acls": {
          "acl": [
            {
              "name": "dns-fragments",
              "type": "ipv6-acl-type",
              "aces": {
                "ace": [
                  {
                    "name": "drop-all-fragments",
                    "matches": {
                      "ipv6": {
                        "ipv6-fragment": {
                          "operator": "match",
                          "type": "isf"
                        }
                      }
                    },
                    "actions": {
                      "forwarding": "drop"
                    }
                  },
                  {
                    "name": "allow-dns-packets",
                    "matches": {
                      "ipv6": {
                        "destination-ipv6-network": "2001:db8::/32"
                      },
                      "udp": {
                        "destination-port": {
                          "operator": "eq",
                          "port": 53
                        }
                      }
                    },
                    "actions": {
                      "forwarding": "accept"
                    }
                  }
                ]
              }
            }
          ]
        }
      }

         Figure 7: Example Illustrating Canddiate Filtering of IPv6
                            Fragmented Packets.

4.5.  Rate-Limit Traffic

   In order to support rate-limiting (see Section 3.6), a new action
   called "rate-limit" is defined.

   (#example_5) shows an ACL example to rate-limit incoming SYNs during
   a SYN flood attack.

     {
        "ietf-access-control-list:acls": {
          "acl": [{
            "name": "tcp-flags-example-with-rate-limit",
            "aces": {
              "ace": [{
                "name": "rate-limit-syn",
                "matches": {
                  "tcp": {
                    "flags-bitmask": {
                      "operator": "match",
                      "bitmask": 2
                    }
                  }
                },
                "actions": {
                  "forwarding": "accept",
                  "rate-limit": "20.00"
                }
              }]
            }
          }]
        }
      }

               Figure 8: Example Rate-Limit Incoming TCP SYNs

5.  YANG Modules

5.1.  Enhanced ACL

   <CODE BEGINS> file "ietf-acl-enh@2022-06-16.yang"
   module ietf-acl-enh {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-acl-enh";
     prefix enh-acl;

     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-access-control-list {
       prefix ietf-acl;
       reference
         "RFC 8519: YANG Data Model for Network Access
                    Control Lists (ACLs), Section 4.1";
     }
     import ietf-packet-fields {
       prefix packet-fields;
       reference
         "RFC 8519: YANG Data Model for Network Access
                    Control Lists (ACLs), Section 4.2";
     }

     organization
       "IETF NETMOD Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
        WG List:  <mailto:netmod@ietf.org>

        Author:    Mohamed Boucadair
                  <mailto:mohamed.boucadair@orange.com>
        Author:    Samier Barguil
                  <mailto:samier.barguilgiraldo.ext@telefonica.com>
        Author:    Oscar Gonzalez de Dios
                  <mailto:oscar.gonzalezdedios@telefonica.com>";
     description
       "This module contains YANG definitions for enhanced ACLs.

        Copyright (c) 2022 IETF Trust and the persons identified as
        authors of the code. All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2022-06-16 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: xxxxx";
     }

     feature match-on-payload {
       description
         "Match based on a pattern is supported.";
     }

     identity offset-type {
       description
         "Base identity for payload offset type.";
     }

     identity layer3 {
       base offset-type;
       description
         "IP header.";
     }

     identity layer4 {
       base offset-type;
       description
         "Transport header (e.g., TCP or UDP).";
     }

     identity payload {
       base offset-type;
       description
         "Transport payload. For example, this represents the beginning
          of the TCP data right after any TCP options.";
     }

     typedef operator {
       type bits {
         bit not {
           position 0;
           description
             "If set, logical negation of operation.";
         }
         bit match {
           position 1;
           description
             "Match bit.  If set, this is a bitwise match operation
              defined as '(data & value) == value'; if unset, (data &
              value) evaluates to TRUE if any of the bits in the value
              mask are set in the data , i.e., '(data & value) != 0'.";
         }
       }
       description
         "How to apply the defined bitmask.";
     }

     typedef fragment-type {
       type bits {
         bit df {
           position 0;
           description
             "Don't fragment bit for IPv4.
              Must be set to 0 when it appears in an IPv6 filter.";
         }
         bit isf {
           position 1;
           description
             "Is a fragment.";
         }
         bit ff {
           position 2;
           description
             "First fragment.";
         }
         bit lf {
           position 3;
           description
             "Last fragment.";
         }
       }
       description
         "Different fragment types to match against.";
     }

     grouping tcp-flags {
       description
         "Operations on TCP flags.";
       leaf operator {
         type operator;
         default "match";
         description
           "How to interpret the TCP flags.";
       }
       leaf bitmask {
         type uint16;
         description
           "Bitmask values can be encoded as a 1- or 2-byte bitmask.
            When a single byte is specified, it matches byte 13
            of the TCP header, which contains bits 8 though 15
            of the 4th 32-bit word.  When a 2-byte encoding is used,
            it matches bytes 12 and 13 of the TCP header with
            the bitmask fields corresponding to the TCP data offset
            field being ignored for purposes of matching.";
       }
     }

     grouping fragment-fields {
       description
         "Operations on fragment types.";
       leaf operator {
         type operator;
         default "match";
         description
           "How to interpret the fragment type.";
       }
       leaf type {
         type fragment-type;
         description
           "What fragment type to look for.";
       }
     }

     grouping payload {
       description
         "Operations on payload match.";
       leaf offset {
         type identityref {
           base offset-type;
         }
         description
           "Indicates the payload offset.";
       }
       leaf offset-end {
         type uint64;
         description
           "Indicates the number of bytes to cover when
            performing the prefix match.";
       }
       leaf operator {
         type operator;
         default "match";
         description
           "How to interpret the prefix match.";
       }
       leaf prefix {
         type binary;
         description
           "The pattern to match against.";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl" {
       description
         "add a new container to store sets (prefix
          sets, port sets, etc";
       container defined-sets {
         description
           "Predefined sets of attributes used in policy match
            statements.";
         container ipv4-prefix-sets {
           description
             "Data definitions for a list of IPv4 or IPv6
              prefixes which are matched as part of a policy.";
           list prefix-set {
             key "name";
             description
               "List of the defined prefix sets";
             leaf name {
               type string;
               description
                 "Name of the prefix set -- this is used as a label to
                  reference the set in match conditions.";
             }
             leaf description {
               type string;
               description
                 "Defined Set description";
             }
             leaf-list prefix {
               type inet:ipv4-prefix;
               description
                 "List of IPv4 prefixes to be used in match
                  conditions.";
             }
           }
         }
         container ipv6-prefix-sets {
           description
             "Data definitions for a list of IPv6 prefixes
              which are matched as part of a policy.";
           list prefix-set {
             key "name";
             description
               "List of the defined prefix sets";
             leaf name {
               type string;
               description
                 "Name of the prefix set -- this is used as a label to
                  reference the set in match conditions.";
             }
             leaf description {
               type string;
               description
                 "A textual description of the prefix list.";
             }
             leaf-list prefix {
               type inet:ipv6-prefix;
               description
                 "List of IPv6 prefixes to be used in match
                  conditions.";
             }
           }
         }
         container port-sets {
           description
             "Data definitions for a list of ports which can
              be matched in policies.";
           list port-set {
             key "name";
             description
               "List of port set definitions.";
             leaf name {
               type string;
               description
                 "Name of the portset -- this is used as a label to
                  reference the set in match conditions.";
             }
             list port {
               key "id";
               description
                 "Port numbers along with the operator on which to
                  match.";
               leaf id {
                 type string;
                 description
                   "Identifier of the list of ports.";
               }
               choice port {
                 description
                   "Choice of specifying the port number or referring
                    to a group of port numbers.";
                 container port-range-or-operator {
                   description
                     "Indicates a set of ports.";
                   uses packet-fields:port-range-or-operator;
                 }
               }
             }
           }
         }
         container protocol-sets {
           description
             "Data definitions for a list of protocols which can
              be matched in policies.";
           list protocol-set {
             key "name";
             description
               "List of protocol set definitions.";
             leaf name {
               type string;
               description
                 "Name of the protocols set -- this is used as a label to
                  reference the set in match conditions.";
             }
             leaf-list protocol {
               type union {
                 type uint8;
                 type string; //Check if we can reuse an IANA-maintained module
               }
               description
                 "Value of the protocl set.";
             }
           }
         }
         container icmp-type-sets {
           description
             "Data definitions for a list of ICMP types which can
              be matched in policies.";
           list icmp-type-set {
             key "name";
             description
               "List of ICMP type set definitions.";
             leaf name {
               type string;
               description
                 "Name of the ICMP type set -- this is used as a label to
                  reference the set in match conditions.";
             }
             list types {
               key "type";
               description
                 "Includes a list of ICMP types.";
               uses packet-fields:acl-icmp-header-fields;
             }
           }
         }
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches" {
       description
         "Add a new match types.";
       choice payload {
         description
           "Match a prefix pattern.";
         container prefix-pattern {
           if-feature "match-on-payload";
           description
             "Rule to perform payload-based match.";
           uses payload;
         }
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches/ietf-acl:l3/ietf-acl:ipv4" {
       description
         "Handle non-initial and initial fragments for IPv4 packets.";
       container ipv4-fragment {
         description
           "Indicates how to handle IPv4 fragments.";
         uses fragment-fields;
       }
       leaf source-ipv4-prefix-list {
         type leafref {
           path "../../../../defined-sets/ipv4-prefix-sets/prefix-set/name";
         }
         description
           "reference to a prefix list to match the source address";
       }
       leaf destination-ipv4-prefix-list {
         type leafref {
           path "../../../../defined-sets/ipv4-prefix-sets/prefix-set/name";
         }
         description
           "reference to a prefix list to match the destination address";
       }
       leaf next-header-set {
         type leafref {
           path "../../../../defined-sets/protocol-sets/protocol-set/name";
         }
         description
           "reference to a protocol set to match the next-header field";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches/ietf-acl:l3/ietf-acl:ipv6" {
       description
         "Handle non-initial and initial fragments for IPv6 packets.";
       container ipv6-fragment {
         description
           "Indicates how to handle IPv6 fragments.";
         uses fragment-fields;
       }
       leaf source-ipv6-prefix-list {
         type leafref {
           path "../../../../defined-sets/ipv6-prefix-sets/prefix-set/name";
         }
         description
           "reference to a prefix list to match the source address";
       }
       leaf destination-ipv6-prefix-list {
         type leafref {
           path "../../../../defined-sets/ipv6-prefix-sets/prefix-set/name";
         }
         description
           "reference to a prefix list to match the destination address";
       }
       leaf protocol-set {
         type leafref {
           path "../../../../defined-sets/protocol-sets/protocol-set/name";
         }
         description
           "reference to a protocol set to match the protocol field";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches/ietf-acl:l4/ietf-acl:tcp" {
       description
         "Handle TCP flags and port sets.";
       container flags-bitmask {
         description
           "Indicates how to handle TCP flags.";
         uses tcp-flags;
       }
       leaf source-tcp-port-set {
         type leafref {
           path "../../../../defined-sets/port-sets/port-set/name";
         }
         description
           "Reference to a port set to match the source port.";
       }
       leaf destination-tcp-port-set {
         type leafref {
           path "../../../../defined-sets/port-sets/port-set/name";
         }
         description
           "Reference to a port set to match the destination port.";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches/ietf-acl:l4/ietf-acl:udp" {
       description
         "Handle UDP port sets.";
       leaf source-udp-port-set {
         type leafref {
           path "../../../../defined-sets/port-sets/port-set/name";
         }
         description
           "Reference to a port set to match the source port.";
       }
       leaf destination-udp-port-set {
         type leafref {
           path "../../../../defined-sets/port-sets/port-set/name";
         }
         description
           "Reference to a port set to match the destination port.";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:matches/ietf-acl:l4/ietf-acl:icmp" {
       description
         "Handle ICMP type sets.";
       leaf icmp-set {
         type leafref {
           path "../../../../defined-sets/icmp-type-sets/icmp-type-set/name";
         }
         description
           "Reference to an ICMP type set to match the ICMP type field.";
       }
     }

     augment "/ietf-acl:acls/ietf-acl:acl/ietf-acl:aces"
           + "/ietf-acl:ace/ietf-acl:actions" {
       description
         "rate-limit action.";
       leaf rate-limit {
         when "../ietf-acl:forwarding = 'ietf-acl:accept'" {
           description
             "rate-limit valid only when accept action is used.";
         }
         type decimal64 {
           fraction-digits 2;
         }
         description
           "Indicates a rate-limit for the matched traffic.";
       }
     }
   }
   <CODE ENDS>

6.  Security Considerations (TBC)

   The YANG modules specified in this document define a schema for data
   that is designed to be accessed via network management protocol such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   *  TBC

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   *  TBC

7.  IANA Considerations

7.1.  URI Registration

   This document requests IANA to register the following URI in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

            URI: urn:ietf:params:xml:ns:yang:ietf-acl-enh
            Registrant Contact: The IESG.
            XML: N/A; the requested URI is an XML namespace.

7.2.  YANG Module Name Registration

   This document requests IANA to register the following YANG module in
   the "YANG Module Names" subregistry [RFC6020] within the "YANG
   Parameters" registry.

            name: ietf-acl-enh
            namespace: urn:ietf:params:xml:ns:yang:ietf-ietf-acl-enh
            maintained by IANA: N
            prefix: enh-acl
            reference: RFC XXXX

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,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/rfc/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/rfc/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/rfc/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/rfc/rfc6242>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/rfc/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8040>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8341>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8446>.

   [RFC8519]  Jethanandani, M., Agarwal, S., Huang, L., and D. Blair,
              "YANG Data Model for Network Access Control Lists (ACLs)",
              RFC 8519, DOI 10.17487/RFC8519, March 2019,
              <https://www.rfc-editor.org/rfc/rfc8519>.

   [RFC8956]  Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed.,
              "Dissemination of Flow Specification Rules for IPv6",
              RFC 8956, DOI 10.17487/RFC8956, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8956>.

8.2.  Informative References

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8340>.

   [RFC8955]  Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              RFC 8955, DOI 10.17487/RFC8955, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8955>.

   [RFC9132]  Boucadair, M., Ed., Shallow, J., and T. Reddy.K,
              "Distributed Denial-of-Service Open Threat Signaling
              (DOTS) Signal Channel Specification", RFC 9132,
              DOI 10.17487/RFC9132, September 2021,
              <https://www.rfc-editor.org/rfc/rfc9132>.

Appendix A.  Acknowledgements

   Many thanks to Jon Shallow and Miguel Cros for the discussion when
   preparing this document.

Authors' Addresses

   Oscar Gonzalez de Dios
   Telefonica
   Email: oscar.gonzalezdedios@telefonica.com


   Samier Barguil
   Telefonica
   Email: samier.barguilgiraldo.ext@telefonica.com


   Mohamed Boucadair
   Orange
   Email: mohamed.boucadair@orange.com