


NETMOD WG                                                 C. Wildes, Ed.
Internet-Draft                                        Cisco Systems Inc.
Intended status: Standards Track                         K. Koushik, Ed.
Expires: September 14, 2018                             Verizon Wireless
                                                          March 15, 2018

               A YANG Data Model for Syslog Configuration
                   draft-ietf-netmod-syslog-model-26

Abstract

   This document defines a YANG data model for the configuration of a
   syslog process.  It is intended this model be used by vendors who
   implement syslog in their systems.

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 http://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 September 14, 2018.

Copyright Notice

   Copyright (c) 2018 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.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  2
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.3.  NDMA Compliance  . . . . . . . . . . . . . . . . . . . . .  3

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     1.4.  Editorial Note (To be removed by RFC Editor) . . . . . . .  3
   2.  Design of the Syslog Model . . . . . . . . . . . . . . . . . .  3
     2.1.  Syslog Module  . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Syslog YANG Module . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  The ietf-syslog Module . . . . . . . . . . . . . . . . . .  8
   4.  Usage Examples . . . . . . . . . . . . . . . . . . . . . . . . 25
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
     6.1.  The IETF XML Registry  . . . . . . . . . . . . . . . . . . 26
     6.2.  The YANG Module Names Registry . . . . . . . . . . . . . . 26
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 27
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 29
   Appendix A. Implementer Guidelines . . . . . . . . . . . . . . . . 29
     Appendix A.1.  Extending Facilities  . . . . . . . . . . . . . . 29
     Appendix A.2.  Syslog Terminal Output  . . . . . . . . . . . . . 30
     Appendix A.3.  Syslog File Naming Convention . . . . . . . . . . 30
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31

1.  Introduction

   This document defines a YANG [RFC7950] configuration data model that
   may be used to configure the syslog feature running on a system.
   YANG models can be used with network management protocols such as
   NETCONF [RFC6241] to install, manipulate, and delete the
   configuration of network devices.

   The data model makes use of the YANG "feature" construct which allows
   implementations to support only those syslog features that lie within
   their capabilities.

   This module can be used to configure the syslog application
   conceptual layers as implemented on the target system.

   Essentially, a syslog process receives messages (from the kernel,
   processes, applications or other syslog processes) and processes
   them.  The processing may involve logging to a local file, and/or
   displaying on console, and/or relaying to syslog processes on other
   machines.  The processing is determined by the "facility" that
   originated the message and the "severity" assigned to the message by
   the facility.

   Such definitions of syslog protocol are defined in [RFC5424], and are
   used in this RFC.

   The YANG model in this document conforms to the Network Management
   Datastore Architecture defined in [draft-ietf-netmod-revised-
   datastores].

1.1.  Requirements Language




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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "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.  Terminology

   The term "originator" is defined in [RFC5424]: an "originator"
   generates syslog content to be carried in a message.

   The term "relay" is defined in [RFC5424]: a "relay" forwards
   messages, accepting messages from originators or other relays and
   sending them to collectors or other relays

   The term "collectors" is defined in [RFC5424]: a "collector" gathers
   syslog content for further analysis.

   The term "action" refers to the processing that takes place for each
   syslog message received.

1.3.  NDMA Compliance

   The YANG model in this document conforms to the Network Management
   Datastore Architecture defined in I-D.ietf-netmod-revised-datastores
   [I-D.ietf-netmod-revised-datastores].

1.4.  Editorial Note (To be removed by RFC Editor)

   This document contains many placeholder values that need to be
   replaced with finalized values at the time of publication.  This note
   summarizes all of the substitutions that are needed.  No other RFC
   Editor instructions are specified elsewhere in this document.

   Artwork in this document contains shorthand references to drafts in
   progress.  Please apply the following replacements:

   o  "I-D.ietf-netconf-keystore" --> the assigned RFC value for draft-
      ietf-netconf-keystore

   o  "I-D.ietf-netconf-tls-client-server" --> the assigned RFC value
      for draft-ietf-netconf-tls-client-server

   o  "zzzz" --> the assigned RFC value for this draft

   o  I-D.ietf-netmod-revised-datastores --> the assigned RFC value for
      draft-ietf-netmod-revised-datastores

2.  Design of the Syslog Model

   The syslog model was designed by comparing various syslog features



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   implemented by various vendors' in different implementations.

   This document addresses the common leafs between implementations and
   creates a common model, which can be augmented with proprietary
   features, if necessary.  This model is designed to be very simple for
   maximum flexibility.

   Some optional features are defined in this document to specify
   functionality that is present in specific vendor configurations.

   Syslog consists of originators and collectors.  The following diagram
   shows syslog messages flowing from originators, to collectors where
   filtering can take place.

   Originators
     +-------------+  +-------------+  +-------------+  +-------------+
     |  Various    |  |     OS      |  |             |  |   Remote    |
     | Components  |  |   Kernel    |  | Line Cards  |  |   Servers   |
     +-------------+  +-------------+  +-------------+  +-------------+
   
     +-------------+  +-------------+  +-------------+  +-------------+
     |    SNMP     |  |  Interface  |  |   Standby   |  |   Syslog    |
     |   Events    |  |   Events    |  |  Supervisor |  |   Itself    |
     +-------------+  +-------------+  +-------------+  +-------------+
   
     |                                                                |
     +----------------------------------------------------------------+
                  |
                  |
                  |
                  |
          +-------------+--------------+
          |             |              |
          v             v              v
   Collectors
     +----------+ +----------+ +----------------+
     |          | |  Log     | |Remote Relay(s)/|
     | Console  | |  File(s) | |Collector(s)    |
     +----------+ +----------+ +----------------+

   Figure 1. Syslog Processing Flow

   Collectors are configured using the leaves in the syslog model
   "actions" container which correspond to each message collector:

      console

      log file(s)

      remote relay(s)/collector(s)





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   Within each action, a selector is used to filter syslog messages.  A
   selector consists of a list of one or more filters specified by
   facility-severity pairs, and, if supported via the select-match
   feature, an optional regular expression pattern match that is
   performed on the [RFC5424] field.

   A syslog message is processed if:

       There is an element of facility-list (F, S) where
           the message facility matches F
           and the message severity matches S
       and/or the message text matches the regex pattern (if it
           is present)

   The facility is one of a specific syslog-facility, or all facilities.

   The severity is one of type syslog-severity, all severities, or none.
   None is a special case that can be used to disable a filter.  When
   filtering severity, the default comparison is that messages of the
   specified severity and higher are selected to be logged.  This is
   shown in the model as "default equals-or-higher".  This behavior can
   be altered if the select-adv-compare feature is enabled to specify a
   compare operation and an action.  Compare operations are: "equals" to
   select messages with this single severity, or "equals-or-higher" to
   select messages of the specified severity and higher.  Actions are
   used to log the message or block the message from being logged.

   Many vendors extend the list of facilities available for logging in
   their implementation.  An example is included in Extending Facilities
   (Appendix A.1).

2.1.  Syslog Module

   A simplified graphical representation of the data model is used in
   this document.  Please see [I-D.ietf-netmod-yang-tree-diagrams] for
   tree diagram notation.


















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   module: ietf-syslog
      +--rw syslog!
         +--rw actions
            +--rw console! {console-action}?
            |  +--rw facility-filter
            |  |  +--rw facility-list* [facility severity]
            |  |     +--rw facility            union
            |  |     +--rw severity            union
            |  |     +--rw advanced-compare {select-adv-compare}?
            |  |        +--rw compare?   enumeration
            |  |        +--rw action?    enumeration
            |  +--rw pattern-match?     string {select-match}?
            +--rw file {file-action}?
            |  +--rw log-file* [name]
            |     +--rw name               inet:uri
            |     +--rw facility-filter
            |     |  +--rw facility-list* [facility severity]
            |     |     +--rw facility            union
            |     |     +--rw severity            union
            |     |     +--rw advanced-compare {select-adv-compare}?
            |     |        +--rw compare?   enumeration
            |     |        +--rw action?    enumeration
            |     +--rw pattern-match?     string {select-match}?
            |     +--rw structured-data?   boolean {structured-data}?
            |     +--rw file-rotation
            |        +--rw number-of-files?   uint32 {file-limit-size}?
            |        +--rw max-file-size?     uint32 {file-limit-size}?
            |        +--rw rollover?          uint32
            |        |       {file-limit-duration}?
            |        +--rw retention?         uint32
            |                {file-limit-duration}?
            +--rw remote {remote-action}?
               +--rw destination* [name]
                  +--rw name                 string
                  +--rw (transport)
                  |  +--:(udp)
                  |  |  +--rw udp
                  |  |     +--rw address?   inet:host
                  |  |     +--rw port?      inet:port-number
                  |  +--:(tls)
                  |     +--rw tls
                  |        +--rw address?        inet:host
                  |        +--rw port?           inet:port-number
                  |        +--rw client-auth
                  |        |  +--rw (auth-type)?
                  |        |     +--:(certificate)
                  |        |        +--rw certificate?   leafref
                  |        +--rw server-auth
                  |        |  +--rw pinned-ca-certs?       leafref
                  |        |  +--rw pinned-server-certs?   leafref
                  |        +--rw hello-params
                  |                {tls-client-hello-params-config}?
                  |           +--rw tls-versions

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                  |           |  +--rw tls-version*   identityref
                  |           +--rw cipher-suites
                  |              +--rw cipher-suite*   identityref
                  +--rw facility-filter
                  |  +--rw facility-list* [facility severity]
                  |     +--rw facility            union
                  |     +--rw severity            union
                  |     +--rw advanced-compare {select-adv-compare}?
                  |        +--rw compare?   enumeration
                  |        +--rw action?    enumeration
                  +--rw pattern-match?       string {select-match}?
                  +--rw structured-data?     boolean {structured-data}?
                  +--rw facility-override?   identityref
                  +--rw source-interface?    if:interface-ref
                  |       {remote-source-interface}?
                  +--rw signing! {signed-messages}?
                     +--rw cert-signers
                        +--rw cert-signer* [name]
                        |  +--rw name              string
                        |  +--rw cert
                        |  |  +--rw algorithm?
                        |  |  |       identityref
                        |  |  +--rw private-key?
                        |  |  |       union
                        |  |  +--rw public-key?
                        |  |  |       binary
                        |  |  +---x generate-private-key
                        |  |  |  +---w input
                        |  |  |     +---w algorithm?
                        |  |  |             identityref
                        |  |  +--rw certificates
                        |  |  |  +--rw certificate* [name]
                        |  |  |     +--rw name     string
                        |  |  |     +--rw value?   binary
                        |  |  +---x generate-certificate-signing-request
                        |  |     +---w input
                        |  |     |  +---w subject       binary
                        |  |     |  +---w attributes?   binary
                        |  |     +--ro output
                        |  |        +--ro certificate-signing-request
                        |  |                binary
                        |  +--rw hash-algorithm?   enumeration
                        +--rw cert-initial-repeat?   uint32
                        +--rw cert-resend-delay?     uint32
                        +--rw cert-resend-count?     uint32
                        +--rw sig-max-delay?         uint32
                        +--rw sig-number-resends?    uint32
                        +--rw sig-resend-delay?      uint32
                        +--rw sig-resend-count?      uint32

   Figure 2. ietf-syslog Module Tree

3.  Syslog YANG Module


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3.1.  The ietf-syslog Module

   This module imports typedefs from [RFC6991],
   [I-D.ietf-netmod-rfc7223bis], groupings from
   [I-D.ietf-netconf-keystore], and
   [I-D.ietf-netconf-tls-client-server], and it references [RFC5424],
   [RFC5425], [RFC5426], [RFC5848], [RFC8089], [RFC8174], and
   [Std-1003.1-2008].














































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   <CODE BEGINS> file "ietf-syslog@2018-03-15.yang"
   module ietf-syslog {
     yang-version 1.1;
   
     namespace "urn:ietf:params:xml:ns:yang:ietf-syslog";
     prefix syslog;
   
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types";
     }
   
     import ietf-interfaces {
       prefix if;
       reference
         "I-D.ietf-netmod-rfc7223bis: A YANG Data Model
          for Interface Management";
     }
   
     import ietf-tls-client {
       prefix tlsc;
       reference
         "I-D.ietf-netconf-tls-client-server:
          YANG Groupings for TLS Clients and TLS Servers";
     }
   
     import ietf-keystore {
       prefix ks;
       reference
         "I-D.ietf-netconf-keystore: YANG Data Model for a
          Keystore Mechanism";
     }
   
     organization
         "IETF NETMOD (Network Modeling) Working Group";
   
     contact
       "WG Web:   <http://tools.ietf.org/wg/netmod/>
        WG List:  <mailto:netmod@ietf.org>
   
        Editor:   Kiran Agrahara Sreenivasa
                  <mailto:kirankoushik.agraharasreenivasa@
                          verizonwireless.com>
   
        Editor:   Clyde Wildes
                  <mailto:cwildes@cisco.com>";
     description
       "This module contains a collection of YANG definitions
        for syslog configuration.
   
        Copyright (c) 2018 IETF Trust and the persons identified as
        authors of the code. All rights reserved.

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        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 Simplified 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).
   
        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
        'OPTIONAL' in the module text are to be interpreted as
        described in RFC 2119 (http://tools.ietf.org/html/rfc2119).
   
        This version of this YANG module is part of RFC zzzz
        (http://tools.ietf.org/html/rfczzzz); see the RFC itself for
        full legal notices.";
   
     revision 2018-03-15 {
       description
         "Initial Revision";
       reference
         "RFC zzzz: Syslog YANG Model";
     }
   
     feature console-action {
       description
         "This feature indicates that the local console action is
          supported.";
     }
   
     feature file-action {
       description
         "This feature indicates that the local file action is
          supported.";
     }
   
     feature file-limit-size {
       description
         "This feature indicates that file logging resources
          are managed using size and number limits.";
     }
   
     feature file-limit-duration {
       description
         "This feature indicates that file logging resources
          are managed using time based limits.";
     }
   
     feature remote-action {
       description
         "This feature indicates that the remote server action is
          supported.";
     }
   

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     feature remote-source-interface {
       description
         "This feature indicates that source-interface is supported
          supported for the remote-action.";
     }
   
     feature select-adv-compare {
       description
         "This feature represents the ability to select messages
          using the additional comparison operators when comparing
          the syslog message severity.";
     }
   
     feature select-match {
       description
         "This feature represents the ability to select messages
          based on a Posix 1003.2 regular expression pattern match.";
     }
   
     feature structured-data {
       description
         "This feature represents the ability to log messages
          in structured-data format.";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     feature signed-messages {
       description
         "This feature represents the ability to configure signed
          syslog messages.";
       reference
         "RFC 5848: Signed Syslog Messages";
     }
   
     typedef syslog-severity {
         type enumeration {
         enum "emergency" {
           value 0;
           description
             "The severity level 'Emergency' indicating that the
              system is unusable.";
         }
         enum "alert" {
           value 1;
           description
             "The severity level 'Alert' indicating that an action
              must be taken immediately.";
         }
         enum "critical" {
           value 2;
           description
             "The severity level 'Critical' indicating a critical
              condition.";

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         }
         enum "error" {
           value 3;
           description
             "The severity level 'Error' indicating an error
              condition.";
         }
         enum "warning" {
           value 4;
           description
             "The severity level 'Warning' indicating a warning
              condition.";
         }
         enum "notice" {
           value 5;
           description
             "The severity level 'Notice' indicating a normal but
              significant condition.";
         }
         enum "info" {
           value 6;
           description
             "The severity level 'Info' indicating an informational
              message.";
         }
         enum "debug" {
           value 7;
           description
             "The severity level 'Debug' indicating a debug-level
              message.";
         }
       }
       description
         "The definitions for Syslog message severity.
          Note that a lower value is a higher severity. Comparisons of
          equal-or-higher severity mean equal or lower numeric value";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity syslog-facility {
       description
         "This identity is used as a base for all syslog facilities.";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity kern {
       base syslog-facility;
       description
         "The facility for kernel messages (0).";
       reference
         "RFC 5424: The Syslog Protocol";
     }

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     identity user {
       base syslog-facility;
       description
         "The facility for user-level messages (1).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity mail {
       base syslog-facility;
       description
         "The facility for the mail system (2).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity daemon {
       base syslog-facility;
       description
         "The facility for the system daemons (3).";
       reference
         "RFC 5424: The Syslog Protocol";
      }
   
     identity auth {
       base syslog-facility;
       description
         "The facility for security/authorization messages (4).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity syslog {
       base syslog-facility;
       description
         "The facility for messages generated internally by syslogd
          facility (5).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity lpr {
       base syslog-facility;
       description
         "The facility for the line printer subsystem (6).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity news {
       base syslog-facility;
       description
         "The facility for the network news subsystem (7).";

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       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity uucp {
       base syslog-facility;
       description
         "The facility for the UUCP subsystem (8).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity cron {
       base syslog-facility;
       description
         "The facility for the clock daemon (9).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity authpriv {
       base syslog-facility;
       description
         "The facility for privileged security/authorization messages
          (10).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity ftp {
       base syslog-facility;
       description
         "The facility for the FTP daemon (11).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity ntp {
       base syslog-facility;
       description
         "The facility for the NTP subsystem (12).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity audit {
       base syslog-facility;
       description
         "The facility for log audit messages (13).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity console {

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       base syslog-facility;
       description
         "The facility for log alert messages (14).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity cron2 {
       base syslog-facility;
       description
         "The facility for the second clock daemon (15).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local0 {
       base syslog-facility;
       description
         "The facility for local use 0 messages (16).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local1 {
       base syslog-facility;
       description
         "The facility for local use 1 messages (17).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local2 {
       base syslog-facility;
       description
         "The facility for local use 2 messages (18).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local3 {
       base syslog-facility;
       description
         "The facility for local use 3 messages (19).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local4 {
       base syslog-facility;
       description
         "The facility for local use 4 messages (20).";
       reference
         "RFC 5424: The Syslog Protocol";
     }

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     identity local5 {
       base syslog-facility;
       description
         "The facility for local use 5 messages (21).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local6 {
       base syslog-facility;
       description
         "The facility for local use 6 messages (22).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     identity local7 {
       base syslog-facility;
       description
         "The facility for local use 7 messages (23).";
       reference
         "RFC 5424: The Syslog Protocol";
     }
   
     grouping severity-filter {
       description
         "This grouping defines the processing used to select
          log messages by comparing syslog message severity using
          the following processing rules:
           - if 'none', do not match.
           - if 'all', match.
           - else compare message severity with the specified severity
             according to the default compare rule (all messages of the
             specified severity and greater match) or if the
             select-adv-compare feature is present, use the
             advance-compare rule.";
       leaf severity {
         type union {
           type syslog-severity;
           type enumeration {
             enum none {
               value 2147483647;
               description
                 "This enum describes the case where no severities
                  are selected.";
             }
             enum all {
               value -2147483648;
               description
                 "This enum describes the case where all severities
                  are selected.";
             }
           }

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         }
         mandatory true;
         description
           "This leaf specifies the syslog message severity.";
       }
       container advanced-compare {
         when '../severity != "all" and
              ../severity != "none"' {
           description
             "The advanced compare container is not applicable for
              severity 'all' or severity 'none'";
         }
         if-feature select-adv-compare;
         leaf compare {
           type enumeration {
             enum equals {
               description
                 "This enum specifies that the severity comparison
                  operation will be equals.";
             }
             enum equals-or-higher {
               description
                 "This enum specifies that the severity comparison
                  operation will be equals or higher.";
             }
           }
           default equals-or-higher;
           description
             "The compare can be used to specify the comparison
              operator that should be used to compare the syslog message
              severity with the specified severity.";
         }
         leaf action {
           type enumeration {
             enum log {
               description
                 "This enum specifies that if the compare operation is
                  true the message will be logged.";
              }
             enum block {
               description
                 "This enum specifies that if the compare operation is
                  true the message will not be logged.";
             }
           }
           default log;
           description
             "The action can be used to specify if the message should
              be logged or blocked based on the outcome of the compare
              operation.";
         }
         description
           "This container describes additional severity compare
            operations that can be used in place of the default

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            severity comparison. The compare leaf specifies the type of
            the compare that is done and the action leaf specifies the
            intended result.
            Example: compare->equals and action->block means
            messages that have a severity that are equal to the
            specified severity will not be logged.";
       }
     }
   
     grouping selector {
       description
         "This grouping defines a syslog selector which is used to
          select log messages for the log-actions (console, file,
          remote, etc.). Choose one or both of the following:
            facility [<facility> <severity>...]
            pattern-match regular-expression-match-string
          If both facility and pattern-match are specified, both must
          match in order for a log message to be selected.";
       container facility-filter {
         description
           "This container describes the syslog filter parameters.";
         list facility-list {
           key "facility severity";
           ordered-by user;
           description
             "This list describes a collection of syslog
              facilities and severities.";
           leaf facility {
             type union {
               type identityref {
                 base syslog-facility;
               }
               type enumeration {
                 enum all {
                   description
                     "This enum describes the case where all
                      facilities are requested.";
                 }
               }
             }
             description
               "The leaf uniquely identifies a syslog facility.";
           }
           uses severity-filter;
         }
       }
       leaf pattern-match {
         if-feature select-match;
         type string;
         description
           "This leaf describes a Posix 1003.2 regular expression
            string that can be used to select a syslog message for
            logging. The match is performed on the SYSLOG-MSG field.";
         reference

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           "RFC 5424: The Syslog Protocol
            Std-1003.1-2008 Regular Expressions";
       }
     }
   
     grouping structured-data {
       description
         "This grouping defines the syslog structured data option
          which is used to select the format used to write log
          messages.";
       leaf structured-data {
         if-feature structured-data;
         type boolean;
         default false;
         description
           "This leaf describes how log messages are written.
            If true, messages will be written with one or more
            STRUCTURED-DATA elements; if false, messages will be
            written with STRUCTURED-DATA = NILVALUE.";
         reference
           "RFC 5424: The Syslog Protocol";
       }
     }
   
     container syslog {
       presence "Enables logging.";
       description
         "This container describes the configuration parameters for
          syslog.";
       container actions {
         description
           "This container describes the log-action parameters
            for syslog.";
         container console {
           if-feature console-action;
           presence "Enables logging to the console";
           description
             "This container describes the configuration parameters
              for console logging.";
           uses selector;
         }
         container file {
           if-feature file-action;
           description
             "This container describes the configuration parameters for
              file logging. If file-archive limits are not supplied, it
              is assumed that the local implementation defined limits
              will be used.";
           list log-file {
             key "name";
             description
               "This list describes a collection of local logging
                files.";
             leaf name {

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               type inet:uri {
                 pattern 'file:.*';
               }
               description
                 "This leaf specifies the name of the log file which
                  MUST use the uri scheme file:.";
               reference
                   "RFC 8089: The file URI Scheme";
             }
             uses selector;
             uses structured-data;
             container file-rotation {
               description
                 "This container describes the configuration
                  parameters for log file rotation.";
               leaf number-of-files {
                 if-feature file-limit-size;
                 type uint32;
                 default 1;
                 description
                   "This leaf specifies the maximum number of log
                    files retained. Specify 1 for implementations
                    that only support one log file.";
               }
               leaf max-file-size {
                 if-feature file-limit-size;
                 type uint32;
                 units "megabytes";
                 description
                   "This leaf specifies the maximum log file size.";
               }
               leaf rollover {
                 if-feature file-limit-duration;
                 type uint32;
                 units "minutes";
                 description
                   "This leaf specifies the length of time that log
                    events should be written to a specific log file.
                    Log events that arrive after the rollover period
                    cause the current log file to be closed and a new
                    log file to be opened.";
               }
               leaf retention {
                 if-feature file-limit-duration;
                 type uint32;
                 units "minutes";
                 description
                   "This leaf specifies the length of time that
                    completed/closed log event files should be stored
                    in the file system before they are removed.";
               }
             }
           }
         }

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         container remote {
           if-feature remote-action;
           description
             "This container describes the configuration parameters
              for forwarding syslog messages to remote relays or
              collectors.";
           list destination {
             key "name";
             description
               "This list describes a collection of remote logging
                destinations.";
             leaf name {
               type string;
               description
                 "An arbitrary name for the endpoint to connect to.";
             }
             choice transport {
               mandatory true;
               description
                 "This choice describes the transport option.";
               case udp {
                 container udp {
                   description
                     "This container describes the UDP transport
                      options.";
                   reference
                     "RFC 5426: Transmission of Syslog Messages over
                      UDP";
                   leaf address {
                     type inet:host;
                     description
                       "The leaf uniquely specifies the address of
                        the remote host. One of the following must be
                        specified: an ipv4 address, an ipv6 address,
                        or a host name.";
                   }
                   leaf port {
                     type inet:port-number;
                     default 514;
                     description
                       "This leaf specifies the port number used to
                        deliver messages to the remote server.";
                   }
                 }
               }
               case tls {
                 container tls {
                   description
                     "This container describes the TLS transport
                      options.";
                   reference
                     "RFC 5425: Transport Layer Security (TLS)
                      Transport Mapping for Syslog ";
                   leaf address {

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                     type inet:host;
                     description
                       "The leaf uniquely specifies the address of
                        the remote host. One of the following must be
                        specified: an ipv4 address, an ipv6 address,
                        or a host name.";
                   }
                   leaf port {
                     type inet:port-number;
                     default 6514;
                     description
                       "TCP port 6514 has been allocated as the default
                        port for syslog over TLS.";
                   }
                   uses tlsc:tls-client-grouping;
                 }
               }
             }
             uses selector;
             uses structured-data;
             leaf facility-override {
               type identityref {
                 base syslog-facility;
               }
               description
                 "If specified, this leaf specifies the facility used
                  to override the facility in messages delivered to
                  the remote server.";
             }
             leaf source-interface {
               if-feature remote-source-interface;
               type if:interface-ref;
               description
                 "This leaf sets the source interface to be used to
                  send messages to the remote syslog server. If not
                  set, messages can be sent on any interface.";
             }
             container signing {
               if-feature signed-messages;
               presence
                 "If present, syslog-signing options is activated.";
               description
                 "This container describes the configuration
                  parameters for signed syslog messages.";
               reference
                 "RFC 5848: Signed Syslog Messages";
               container cert-signers {
                 description
                   "This container describes the signing certificate
                    configuration for Signature Group 0 which covers
                    the case for administrators who want all Signature
                    Blocks to be sent to a single destination.";
                 list cert-signer {
                   key "name";

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                   description
                     "This list describes a collection of syslog
                      message signers.";
                   leaf name {
                     type string;
                     description
                       "This leaf specifies the name of the syslog
                        message signer.";
                   }
                   container cert {
                     uses ks:private-key-grouping;
                     uses ks:certificate-grouping;
                     description
                      "This is the certificate that is periodically
                       sent to the remote receiver. Selection of the
                       certificate also implicitly selects the private
                       key used to sign the syslog messages.";
                   }
                   leaf hash-algorithm {
                     type enumeration {
                       enum SHA1 {
                         value 1;
                         description
                           "This enum describes the SHA1 algorithm.";
                       }
                       enum SHA256 {
                         value 2;
                         description
                           "This enum describes the SHA256 algorithm.";
                       }
                     }
                     description
                       "This leaf describes the syslog signer hash
                        algorithm used.";
                   }
                 }
                 leaf cert-initial-repeat {
                   type uint32;
                   default 3;
                   description
                   "This leaf specifies the number of times each
                    Certificate Block should be sent before the first
                    message is sent.";
                 }
                 leaf cert-resend-delay {
                   type uint32;
                   units "seconds";
                   default 3600;
                   description
                     "This leaf specifies the maximum time delay in
                      seconds until resending the Certificate Block.";
                 }
                 leaf cert-resend-count {
                   type uint32;

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                   default 0;
                   description
                     "This leaf specifies the maximum number of other
                      syslog messages to send until resending the
                      Certificate Block.";
                 }
                 leaf sig-max-delay {
                   type uint32;
                   units "seconds";
                   default 60;
                   description
                     "This leaf specifies when to generate a new
                      Signature Block. If this many seconds have
                      elapsed since the message with the first message
                      number of the Signature Block was sent, a new
                      Signature Block should be generated.";
                 }
                 leaf sig-number-resends {
                   type uint32;
                   default 0;
                   description
                     "This leaf specifies the number of times a
                      Signature Block is resent. (It is recommended to
                      select a value of greater than 0 in particular
                      when the UDP transport RFC 5426 is used.).";
                 }
                 leaf sig-resend-delay {
                   type uint32;
                   units "seconds";
                   default 5;
                   description
                     "This leaf specifies when to send the next
                      Signature Block transmission based on time. If
                      this many seconds have elapsed since the previous
                      sending of this Signature Block, resend it.";
                 }
                 leaf sig-resend-count {
                   type uint32;
                   default 0;
                   description
                     "This leaf specifies when to send the next
                      Signature Block transmission based on a count.
                      If this many other syslog messages have been
                      sent since the previous sending of this
                      Signature Block, resend it. A value of 0 means
                      that you don't resend based on the number of
                      messages.";
                 }
               }
             }
           }
         }
       }
     }

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   }
   <CODE ENDS>

   Figure 3. ietf-syslog Module

4.  Usage Examples

      Requirement:
      Enable console logging of syslogs of severity critical
   
      <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog">
        <actions>
          <console>
            <facility-filter>
              <facility-list>
                <facility>all</facility>
                <severity>critical</severity>
              </facility-list>
            </facility-filter>
          </console>
        </actions>
      </syslog>
   
      Enable remote logging of syslogs to udp destination
      foo.example.com for facility auth, severity error
   
      <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog">
        <actions>
          <remote>
            <destination>
              <name>remote1</name>
              <udp>
                <address>foo.example.com</address>
              </udp>
              <facility-filter>
                <facility-list>
                  <facility>auth</facility>
                  <severity>error</severity>
                </facility-list>
              </facility-filter>
            </destination>
          </remote>
        </actions>
      </syslog>

   Figure 4. ietf-syslog Examples

5.  Acknowledgements

   The authors wish to thank the following who commented on this
   proposal:




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   Andy Bierman, Martin Bjorklund, Alex Campbell, Alex Clemm, Francis
   Dupont, Jim Gibson, Jeffrey Haas, Bob Harold, John Heasley, Giles
   Heron, Lisa Huang, Mahesh Jethanandani, Warren Kumari, Jeffrey K
   Lange, Jan Lindblad, Chris Lonvick, Alexey Melnikov, Kathleen
   Moriarty, Tom Petch, Adam Roach, Juergen Schoenwaelder, Phil Shafer,
   Yaron Sheffer, Jason Sterne, Peter Van Horne, Kent Watsen, Bert
   Wijnen, Dale R Worley, and Aleksandr Zhdankin.

6.  IANA Considerations

6.1.  The IETF XML Registry

   This document registers one URI in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registration is
   requested:

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

6.2.  The YANG Module Names Registry

   This document registers one YANG module in the YANG Module Names
   registry [RFC7895].  Following the format in [RFC7950], the following
   registration is requested:

      name:         ietf-syslog
      namespace:    urn:ietf:params:xml:ns:yang:ietf-syslog
      prefix:       ietf-syslog
      reference:    RFC zzzz
   

7.  Security Considerations

   The YANG module defined in this document is designed to be accessed
   via YANG based management protocols, such as NETCONF [RFC6241] and
   RESTCONF [RFC8040].  Both of these protocols have mandatory-to-
   implement secure transport layers (e.g., SSH, TLS) with mutual
   authentication.

   The NETCONF access control model (NACM) [RFC6536] provides the means
   to restrict access for particular users to a pre-configured subset of
   all available protocol operations and content.











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   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 should be considered sensitive or
   vulnerable in all network environments.  Logging in particular is
   used to assess the state of systems and can be used to indicate a
   network compromise.  If logging were to be disabled through malicious
   means, attacks may not be readily detectable.  Therefore write
   operations (e.g., edit-config) to these data nodes without proper
   protection can have a negative effect on network operations and on
   network security.

   In addition there are data nodes that require careful analysis and
   review.  These are the subtrees and data nodes and their sensitivity/
   vulnerability:

      facility-filter/pattern-match: When writing this node,
         implementations MUST ensure that the regular expression pattern
         match is not constructed to cause a regular expression denial
         of service attack due to a pattern that causes the regular
         expression implementation to work very slowly (exponentially
         related to input size).

      remote/destination/signing/cert-signer: When writing this subtree,
         implementations MUST NOT specify a private key that is used for
         any other purpose.

   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:

      remote/destination/transport: This subtree contains information
         about other hosts in the network, and the TLS transport
         certificate properties if TLS is selected as the transport
         protocol.

      remote/destination/signing: This subtree contains information
         about the syslog message signing properties including signing
         certificate information.

   There are no RPC operations defined in this YANG module.

8.  References

8.1.  Normative References

   [I-D.ietf-netconf-keystore]
              Watsen, K., "YANG Data Model for a "Keystore" Mechanism",
              Internet-Draft draft-ietf-netconf-keystore-04, October
              2017.

   [I-D.ietf-netconf-tls-client-server]

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              Watsen, K. and G. Wu, "YANG Groupings for TLS Clients and
              TLS Servers", Internet-Draft draft-ietf-netconf-tls-
              client-server-05, October 2017.

   [I-D.ietf-netmod-rfc7223bis]
              Bjorklund, M., "A YANG Data Model for Interface
              Management", Internet-Draft draft-ietf-netmod-
              rfc7223bis-03, January 2018.

   [RFC2119]  Bradner, 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>.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, DOI
              10.17487/RFC5424, March 2009, <http://www.rfc-editor.org/
              info/rfc5424>.

   [RFC5425]  Miao, F., Ed., Ma, Y.Ed.,  and J. Salowey, Ed., "Transport
              Layer Security (TLS) Transport Mapping for Syslog", RFC
              5425, DOI 10.17487/RFC5425, March 2009, <https://www.rfc-
              editor.org/info/rfc5425>.

   [RFC5426]  Okmianski, A., "Transmission of Syslog Messages over UDP",
              RFC 5426, DOI 10.17487/RFC5426, March 2009, <http://www
              .rfc-editor.org/info/rfc5426>.

   [RFC5848]  Kelsey, J., Callas, J. and A. Clemm, "Signed Syslog
              Messages", RFC 5848, DOI 10.17487/RFC5848, May 2010,
              <http://www.rfc-editor.org/info/rfc5848>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types", RFC
              6991, DOI 10.17487/RFC6991, July 2013, <https://www.rfc-
              editor.org/info/rfc6991>.

   [RFC7895]  Bierman, A., Bjorklund, M. and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
              <http://www.rfc-editor.org/info/rfc7895>.

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

   [RFC8089]  Kerwin, M., "The "file" URI Scheme", RFC 8089, DOI
              10.17487/RFC8089, February 2017, <https://www.rfc-
              editor.org/info/rfc8089>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <http://www.rfc-editor.org/info/rfc8174>.

   [Std-1003.1-2008]



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              The Open Group, ""Chapter 9: Regular Expressions".  The
              Open Group Base Specifications Issue 6, IEEE Std
              1003.1-2008, 2016 Edition.", September 2016, <http://
              pubs.opengroup.org/onlinepubs/9699919799/>.

8.2.  Informative References

   [I-D.ietf-netmod-revised-datastores]
              Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.
              and R. Wilton, "Network Management Datastore
              Architecture", Internet-Draft draft-ietf-netmod-revised-
              datastores-10, January 2018.

   [I-D.ietf-netmod-yang-tree-diagrams]
              Bjorklund, M. and L. Berger, "YANG Tree Diagrams",
              Internet-Draft draft-ietf-netmod-yang-tree-diagrams-06,
              February 2018.

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

   [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,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536, DOI
              10.17487/RFC6536, March 2012, <https://www.rfc-editor.org/
              info/rfc6536>.

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

Appendix A.  Implementer Guidelines

Appendix A.1.  Extending Facilities

   Many vendors extend the list of facilities available for logging in
   their implementation.  Additional facilities may not work with the
   syslog protocol as defined in [RFC5424] and hence such facilities
   apply for local syslog-like logging functionality.

   The following is an example that shows how additional facilities
   could be added to the list of available facilities (in this example
   two facilities are added):







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   module example-vendor-syslog-types {
     namespace "http://example.com/ns/vendor-syslog-types";
     prefix vendor-syslogtypes;
   
     import ietf-syslog {
       prefix syslogtypes;
     }
   
     organization "Example, Inc.";
     contact
       "Example, Inc.
        Customer Service
   
        E-mail: syslog-yang@example.com";
   
     description
       "This module contains a collection of vendor-specific YANG type
        definitions for SYSLOG.";
   
     revision 2017-08-11 {
       description
         "Version 1.0";
       reference
         "Vendor SYSLOG Types: SYSLOG YANG Model";
     }
   
     identity vendor_specific_type_1 {
       base syslogtypes:syslog-facility;
       description
         "Adding vendor specific type 1 to syslog-facility";
     }
   
     identity vendor_specific_type_2 {
       base syslogtypes:syslog-facility;
       description
         "Adding vendor specific type 2 to syslog-facility";
     }
   }

Appendix A.2.  Syslog Terminal Output

   Terminal output with requirements more complex than the console
   subtree currently provides, are expected to be supported via vendor
   extensions rather than handled via the file subtree.

Appendix A.3.  Syslog File Naming Convention

   The syslog/file/log-file/file-rotation container contains
   configuration parameters for syslog file rotation.  This section
   describes how these fields might be used by an implementer to name
   syslog files in a rotation process.  This information is offered as
   an informative guide only.


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Internet-Draft             Syslog Management                  March 2018


   When an active syslog file with a name specified by log-file/name,
   reaches log-file/max-file-size and/or syslog events arrive after the
   period specified by log-file/rollover, the logging system can close
   the file, can compress it, and can name the archive file <log-file/
   name>.0.gz.  The logging system can then open a new active syslog
   file <log-file/name>.

   When the new syslog file reaches either of the size limits referenced
   above, <log-file/name>.0.gz can be renamed <log-file/name>.1.gz and
   the new syslog file can be closed, compressed and renamed <log-file/
   name>.0.gz.  Each time that a new syslog file is closed, each of the
   prior syslog archive files named <log-file/name>.<n>.gz can be
   renamed to <log-file/name>.<n + 1>.gz.

   Removal of archive log files could occur when either or both:

   - log-file/number-of-files specified - the logging system can create
   up to log-file/number-of-files syslog archive files after which, the
   contents of the oldest archived file could be overwritten.

   - log-file/retention specified - the logging system can remove those
   syslog archive files whose file expiration time (file creation time
   plus the specified log-file/retention time) is prior to the current
   time.

Authors' Addresses

   Clyde Wildes, editor
   Cisco Systems Inc.
   170 West Tasman Drive
   San Jose, CA 95134
   US
   
   Phone: +1 408 527-2672
   Email: cwildes@cisco.com


   Kiran Koushik, editor
   Verizon Wireless
   500 W Dove Rd.
   Southlake, TX 76092
   US
   
   Phone: +1 512 650-0210
   Email: kirankoushik.agraharasreenivasa@verizonwireless.com








Wildes & Koushik       Expires September 14, 2018              [Page 31]
