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RFC 1472 - The Definitions of Managed Objects for the Security P


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Network Working Group                                      F. Kastenholz
Request for Comments: 1472                            FTP Software, Inc.
                                                               June 1993

                 The Definitions of Managed Objects for
                       the Security Protocols of
                      the Point-to-Point Protocol

Status of this Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

Abstract

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in TCP/IP-based internets.
   In particular, it describes managed objects used for managing the
   Security Protocols on subnetwork interfaces using the family of
   Point-to-Point Protocols [8, 9, 10, 11, & 12].

Table of Contents

   1. The Network Management Framework ......................    1
   2. Objects ...............................................    2
   2.1 Format of Definitions ................................    2
   3. Overview ..............................................    2
   3.1 Object Selection Criteria ............................    2
   3.2 Structure of the PPP .................................    2
   3.3 MIB Groups ...........................................    3
   4. Definitions ...........................................    4
   5. Acknowledgements ......................................    9
   6. Security Considerations ...............................   10
   7. References ............................................   11
   8. Author's Address ......................................   12

1.  The Network Management Framework

   The Internet-standard Network Management Framework consists of three
   components.  They are:

      STD 16/RFC 1155 which defines the SMI, the mechanisms used for
      describing and naming objects for the purpose of management.  STD
      16/RFC 1212 defines a more concise description mechanism, which is

      wholly consistent with the SMI.

      STD 17/RFC 1213 which defines MIB-II, the core set of managed
      objects for the Internet suite of protocols.

      STD 15/RFC 1157 which defines the SNMP, the protocol used for
      network access to managed objects.

   The Framework permits new objects to be defined for the purpose of
   experimentation and evaluation.

2.  Objects

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the subset of Abstract Syntax Notation One (ASN.1) [3]
   defined in the SMI.  In particular, each object type is named by an
   OBJECT IDENTIFIER, an administratively assigned name.  The object
   type together with an object instance serves to uniquely identify a
   specific instantiation of the object.  For human convenience, we
   often use a textual string, termed the descriptor, to refer to the
   object type.

2.1.  Format of Definitions

   Section 4 contains the specification of all object types contained in
   this MIB module.  The object types are defined using the conventions
   defined in the SMI, as amended by the extensions specified in [5,6].

3.  Overview

3.1.  Object Selection Criteria

   To be consistent with IAB directives and good engineering practice,
   an explicit attempt was made to keep this MIB as simple as possible.
   This was accomplished by applying the following criteria to objects
   proposed for inclusion:

      (1)  Require objects be essential for either fault or
           configuration management.  In particular, objects for
           which the sole purpose was to debug implementations were
           explicitly excluded from the MIB.

      (2)  Consider evidence of current use and/or utility.

      (3)  Limit the total number of objects.

      (4)  Exclude objects which are simply derivable from others in

           this or other MIBs.

3.2.  Structure of the PPP

   This section describes the basic model of PPP used in developing the
   PPP MIB. This information should be useful to the implementor in
   understanding some of the basic design decisions of the MIB.

   The PPP is not one single protocol but a large family of protocols.
   Each of these is, in itself, a fairly complex protocol.  The PPP
   protocols may be divided into three rough categories:

   Control Protocols
      The Control Protocols are used to control the operation of the
      PPP. The Control Protocols include the Link Control Protocol
      (LCP), the Password Authentication Protocol (PAP), the Link
      Quality Report (LQR), and the Challenge Handshake Authentication
      Protocol (CHAP).

   Network Protocols
      The Network Protocols are used to move the network traffic over
      the PPP interface.  A Network Protocol encapsulates the datagrams
      of a specific higher-layer protocol that is using the PPP as a
      data link.  Note that within the context of PPP, the term "Network
      Protocol" does not imply an OSI Layer-3 protocol; for instance,
      there is a Bridging network protocol.

   Network Control Protocols (NCPs)
      The NCPs are used to control the operation of the Network
      Protocols. Generally, each Network Protocol has its own Network
      Control Protocol; thus, the IP Network Protocol has its IP Control
      Protocol, the Bridging Network Protocol has its Bridging Network
      Control Protocol and so on.

   This document specifies the objects used in managing one of these
   protocols, namely the PPP Authentication Protocols.

3.3.  MIB Groups

   Objects in this MIB are arranged into several MIB groups.  Each group
   is organized as a set of related objects.

   These groups are the basic unit of conformance: if the semantics of a
   group are applicable to an implementation then all objects in the
   group must be implemented.

   The PPP MIB is organized into several MIB Groups, including, but not
   limited to, the following groups:

          o The PPP Link Group
          o The PPP LQR Group
          o The PPP LQR Extensions Group
          o The PPP IP Group
          o The PPP Bridge Group
          o The PPP Security Group

   This document specifies the following group:

   PPP Security Group
      The PPP Security Group contains all configuration and control
      variables that apply to PPP security.

      Implementation of this group is optional.  Implementation is
      optional since the variables in this group provide configuration
      and control for the PPP Security functions.  Thus, these variables
      should be protected by SNMPv2 security.  If an agent does not
      support SNMPv2 with privacy it is strongly advised that this group
      not be implemented.  See the section on "Security Considerations"
      at the end of this document.

4.  Definitions

          PPP-SEC-MIB DEFINITIONS ::= BEGIN

          IMPORTS
               Counter
                    FROM RFC1155-SMI
               OBJECT-TYPE
                    FROM RFC-1212
               ppp
                    FROM PPP-LCP-MIB;

               pppSecurity OBJECT IDENTIFIER ::= { ppp 2 }

               pppSecurityProtocols OBJECT IDENTIFIER ::= { pppSecurity 1 }

          -- The following uniquely identify the various protocols
          -- used by PPP security. These OBJECT IDENTIFIERS are
          -- used in the pppSecurityConfigProtocol and
          -- pppSecuritySecretsProtocol objects to identify to which
          -- protocols the table entries apply.

               pppSecurityPapProtocol OBJECT IDENTIFIER ::=
                         { pppSecurityProtocols 1 }
               pppSecurityChapMD5Protocol OBJECT IDENTIFIER ::=
                         { pppSecurityProtocols 2 }

          -- PPP Security Group
          -- Implementation of this group is optional.

          -- This table allows the network manager to configure
          -- which security protocols are to be used on which
          -- link and in what order of preference each is to be tried

          pppSecurityConfigTable   OBJECT-TYPE
               SYNTAX    SEQUENCE OF PppSecurityConfigEntry
               ACCESS    not-accessible
               STATUS    mandatory
               DESCRIPTION
                         "Table containing the configuration and
                         preference parameters for PPP Security."
               ::= { pppSecurity 2 }

          pppSecurityConfigEntry   OBJECT-TYPE
               SYNTAX    PppSecurityConfigEntry
               ACCESS    not-accessible
               STATUS    mandatory
               DESCRIPTION
                         "Security configuration information for a
                         particular PPP link."
               INDEX     { pppSecurityConfigLink,
                         pppSecurityConfigPreference }
               ::= { pppSecurityConfigTable 1 }

          PppSecurityConfigEntry ::= SEQUENCE {
               pppSecurityConfigLink
                    INTEGER,
               pppSecurityConfigPreference
                    INTEGER,
               pppSecurityConfigProtocol
                    OBJECT IDENTIFIER,
               pppSecurityConfigStatus
                    INTEGER
               }

          pppSecurityConfigLink   OBJECT-TYPE
               SYNTAX    INTEGER(0..2147483647)
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "The value of ifIndex that identifies the entry

                         in the interface table that is associated with
                         the local PPP entity's link for which this
                         particular security algorithm shall be
                         attempted. A value of 0 indicates the default
                         algorithm - i.e., this entry applies to all
                         links for which explicit entries in the table
                         do not exist."
               ::= { pppSecurityConfigEntry 1 }

          pppSecurityConfigPreference   OBJECT-TYPE
               SYNTAX    INTEGER(0..2147483647)
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "The relative preference of the security
                         protocol identified by
                         pppSecurityConfigProtocol. Security protocols
                         with lower values of
                         pppSecurityConfigPreference are tried before
                         protocols with higher values of
                         pppSecurityConfigPreference."
               ::= { pppSecurityConfigEntry 2 }

          pppSecurityConfigProtocol   OBJECT-TYPE
               SYNTAX    OBJECT IDENTIFIER
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "Identifies the security protocol to be
                         attempted on the link identified by
                         pppSecurityConfigLink at the preference level
                         identified by pppSecurityConfigPreference. "
               ::= { pppSecurityConfigEntry 3 }

          pppSecurityConfigStatus   OBJECT-TYPE
               SYNTAX    INTEGER  {
                         invalid(1),
                         valid(2)
                    }
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "Setting this object to the value invalid(1)
                         has the effect of invalidating the
                         corresponding entry in the

                         pppSecurityConfigTable. It is an
                         implementation-specific matter as to whether
                         the agent removes an invalidated entry from the
                         table.  Accordingly, management stations must
                         be prepared to receive tabular information from
                         agents that corresponds to entries not
                         currently in use.  Proper interpretation of
                         such entries requires examination of the
                         relevant pppSecurityConfigStatus object."
               DEFVAL    { valid }
               ::= { pppSecurityConfigEntry 4 }

          -- This table contains all of the ID/Secret pair information.

          pppSecuritySecretsTable   OBJECT-TYPE
               SYNTAX    SEQUENCE OF PppSecuritySecretsEntry
               ACCESS    not-accessible
               STATUS    mandatory
               DESCRIPTION
                         "Table containing the identities and secrets
                         used by the PPP authentication protocols.  As
                         this table contains secret information, it is
                         expected that access to this table be limited
                         to those SNMP Party-Pairs for which a privacy
                         protocol is in use for all SNMP messages that
                         the parties exchange.  This table contains both
                         the ID and secret pair(s) that the local PPP
                         entity will advertise to the remote entity and
                         the pair(s) that the local entity will expect
                         from the remote entity.  This table allows for
                         multiple id/secret password pairs to be
                         specified for a particular link by using the
                         pppSecuritySecretsIdIndex object."
               ::= { pppSecurity 3 }

          pppSecuritySecretsEntry   OBJECT-TYPE
               SYNTAX    PppSecuritySecretsEntry
               ACCESS    not-accessible
               STATUS    mandatory
               DESCRIPTION
                         "Secret information."
               INDEX     { pppSecuritySecretsLink,
                         pppSecuritySecretsIdIndex }
               ::= { pppSecuritySecretsTable 1 }

          PppSecuritySecretsEntry ::= SEQUENCE {
               pppSecuritySecretsLink
                    INTEGER,
               pppSecuritySecretsIdIndex
                    INTEGER,
               pppSecuritySecretsDirection
                    INTEGER,
               pppSecuritySecretsProtocol
                    OBJECT IDENTIFIER,
               pppSecuritySecretsIdentity
                    OCTET STRING,
               pppSecuritySecretsSecret
                    OCTET STRING,
               pppSecuritySecretsStatus
                    INTEGER
          }

          pppSecuritySecretsLink   OBJECT-TYPE
               SYNTAX    INTEGER(0..2147483647)
               ACCESS    read-only
               STATUS    mandatory
               DESCRIPTION
                         "The link to which this ID/Secret pair applies.
                         By convention, if the value of this object is 0
                         then the ID/Secret pair applies to all links."
               ::= { pppSecuritySecretsEntry 1 }

          pppSecuritySecretsIdIndex   OBJECT-TYPE
               SYNTAX    INTEGER(0..2147483647)
               ACCESS    read-only
               STATUS    mandatory
               DESCRIPTION
                         "A unique value for each ID/Secret pair that
                         has been defined for use on this link.  This
                         allows multiple ID/Secret pairs to be defined
                         for each link.  How the local entity selects
                         which pair to use is a local implementation
                         decision."
               ::= { pppSecuritySecretsEntry 2 }

          pppSecuritySecretsDirection   OBJECT-TYPE
               SYNTAX    INTEGER  {
                         local-to-remote(1),
                         remote-to-local(2)
                    }
               ACCESS    read-write

               STATUS    mandatory
               DESCRIPTION
                         "This object defines the direction in which a
                         particular ID/Secret pair is valid.  If this
                         object is local-to-remote then the local PPP
                         entity will use the ID/Secret pair when
                         attempting to authenticate the local PPP entity
                         to the remote PPP entity.  If this object is
                         remote-to-local then the local PPP entity will
                         expect the ID/Secret pair to be used by the
                         remote PPP entity when the remote PPP entity
                         attempts to authenticate itself to the local
                         PPP entity."
               ::= { pppSecuritySecretsEntry 3 }

          pppSecuritySecretsProtocol   OBJECT-TYPE
               SYNTAX    OBJECT IDENTIFIER
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "The security protocol (e.g. CHAP or PAP) to
                         which this ID/Secret pair applies."
               ::= { pppSecuritySecretsEntry 4 }

          pppSecuritySecretsIdentity   OBJECT-TYPE
               SYNTAX    OCTET STRING (SIZE(0..255))
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "The Identity of the ID/Secret pair.  The
                         actual format, semantics, and use of
                         pppSecuritySecretsIdentity depends on the
                         actual security protocol used.  For example, if
                         pppSecuritySecretsProtocol is
                         pppSecurityPapProtocol then this object will
                         contain a PAP Peer-ID. If
                         pppSecuritySecretsProtocol is
                         pppSecurityChapMD5Protocol then this object
                         would contain the CHAP NAME parameter."
               ::= { pppSecuritySecretsEntry 5 }

          pppSecuritySecretsSecret   OBJECT-TYPE
               SYNTAX    OCTET STRING (SIZE(0..255))
               ACCESS    read-write
               STATUS    mandatory

               DESCRIPTION
                         "The secret of the ID/Secret pair.  The actual
                         format, semantics, and use of
                         pppSecuritySecretsSecret depends on the actual
                         security protocol used.  For example, if
                         pppSecuritySecretsProtocol is
                         pppSecurityPapProtocol then this object will
                         contain a PAP Password. If
                         pppSecuritySecretsProtocol is
                         pppSecurityChapMD5Protocol then this object
                         would contain the CHAP MD5 Secret."
               ::= { pppSecuritySecretsEntry 6 }

          pppSecuritySecretsStatus   OBJECT-TYPE
               SYNTAX    INTEGER  {
                         invalid(1),
                         valid(2)
                    }
               ACCESS    read-write
               STATUS    mandatory
               DESCRIPTION
                         "Setting this object to the value invalid(1)
                         has the effect of invalidating the
                         corresponding entry in the
                         pppSecuritySecretsTable. It is an
                         implementation-specific matter as to whether
                         the agent removes an invalidated entry from the
                         table.  Accordingly, management stations must
                         be prepared to receive tabular information from
                         agents that corresponds to entries not
                         currently in use.  Proper interpretation of
                         such entries requires examination of the
                         relevant pppSecuritySecretsStatus object."
               DEFVAL    { valid }
               ::= { pppSecuritySecretsEntry 7 }

          END

5.  Acknowledgements

   This document was produced by the PPP working group.  In addition to
   the working group, the author wishes to thank the following
   individuals for their comments and contributions:

          Bill Simpson -- Daydreamer
          Glenn McGregor -- Merit

          Jesse Walker -- DEC
          Chris Gunner -- DEC

6.  Security Considerations

   The PPP MIB affords the network operator the ability to configure and
   control the PPP links of a particular system, including the PPP
   authentication protocols. This represents a security risk.

   These risks are addressed in the following manners:

      (1)  All variables which represent a significant security risk
           are placed in separate, optional, MIB Groups. As the MIB
           Group is the quantum of implementation within a MIB, the
           implementor of the MIB may elect not to implement these
           groups.

      (2)  The implementor may choose to implement the variables
           which present a security risk so that they may not be
           written, i.e., the variables are READ-ONLY. This method
           still presents a security risk, and is not recommended,
           in that the variables, specifically the PPP
           Authentication Protocols' variables, may be easily read.

      (3)  Using SNMPv2, the operator can place the variables into
           MIB views which are protected in that the parties which
           have access to those MIB views use authentication and
           privacy protocols, or the operator may elect to make
           these views not accessible to any party.  In order to
           facilitate this placement, all security-related variables
           are placed in separate MIB Tables. This eases the
           identification of the necessary MIB View Subtree.

      (4)  The PPP Security Protocols MIB (this document) contains
           several objects which are very sensitive from a security
           point of view.

   Specifically, this MIB contains objects that define the PPP Peer
   Identities (which can be viewed as "userids") and the secrets used to
   authenticate those Peer Identities (similar to a "password" for the
   "userid").

   Also, this MIB contains variables which would allow a network manager
   to control the operation of the security features of PPP.  An
   intruder could disable PPP security if these variables were not
   properly protected.

   Thus, in order to preserve the integrity, security and privacy of the

   PPP security features, an implementation will allow access to this
   MIB only via SNMPv2 and then only for parties which are privacy
   enhanced.  Other access modes, e.g., SNMPv1 or SNMPv2 without
   privacy- enhancement, are very dangerous and the security of the PPP
   service may be compromised.

7.  References

   [1] Rose M., and K. McCloghrie, "Structure and Identification of
       Management Information for TCP/IP-based internets", STD 16, RFC
       1155, Performance Systems International, Hughes LAN Systems, May
       1990.

   [2] McCloghrie K., and M. Rose, Editors, "Management Information Base
       for Network Management of TCP/IP-based internets", STD 17, RFC
       1213, Performance Systems International, March 1991.

   [3] Information processing systems - Open Systems Interconnection -
       Specification of Abstract Syntax Notation One (ASN.1),
       International Organization for Standardization, International
       Standard 8824, December 1987.

   [4] Information processing systems - Open Systems Interconnection -
       Specification of Basic Encoding Rules for Abstract Notation One
       (ASN.1), International Organization for Standardization,
       International Standard 8825, December 1987.

   [5] Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions",
       STD 16, RFC 1212, Performance Systems International, Hughes LAN
       Systems, March 1991.

   [6] Rose, M., Editor, "A Convention for Defining Traps for use with
       the SNMP", RFC 1215, Performance Systems International, March
       1991.

   [7] McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
       1229, Hughes LAN Systems, Inc., May 1991.

   [8] Simpson, W., "The Point-to-Point Protocol for the Transmission of
       Multi-protocol Datagrams over Point-to-Point Links, RFC 1331,
       Daydreamer, May 1992.

   [9] McGregor, G., "The PPP Internet Protocol Control Protocol", RFC
       1332, Merit, May 1992.

  [10] Baker, F., "Point-to-Point Protocol Extensions for Bridging", RFC
       1220, ACC, April 1991.

  [11] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
       1334, L&A, Daydreamer, October 1992.

  [12] Simpson, W., "PPP Link Quality Monitoring", RFC 1333, Daydreamer,
       May 1992.

8.  Author's Address

   Frank Kastenholz
   FTP Software, Inc.
   2 High Street
   North Andover, Mass 01845 USA

   Phone: (508) 685-4000
   EMail: kasten@ftp.com

 

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