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
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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
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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:
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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 }
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-- 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
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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
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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 }
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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
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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
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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
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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
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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.
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[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
Kastenholz [Page 13]
