RFCs in HTML Format


RFC 1445

          Network Working Group                                J. Galvin
          Request for Comments: 1445         Trusted Information Systems
                                                           K. McCloghrie
                                                      Hughes LAN Systems
                                                              April 1993


                               Administrative Model
                               for version 2 of the
                   Simple Network Management Protocol (SNMPv2)



        Table of Contents


          1 Introduction ..........................................    2
          1.1 A Note on Terminology ...............................    2
          2 Elements of the Model .................................    3
          2.1 SNMPv2 Party ........................................    3
          2.2 SNMPv2 Entity .......................................    6
          2.3 SNMPv2 Management Station ...........................    7
          2.4 SNMPv2 Agent ........................................    7
          2.5 View Subtree ........................................    7
          2.6 MIB View ............................................    8
          2.7 Proxy Relationship ..................................    8
          2.8 SNMPv2 Context ......................................   10
          2.9 SNMPv2 Management Communication .....................   10
          2.10 SNMPv2 Authenticated Management Communication ......   12
          2.11 SNMPv2 Private Management Communication ............   13
          2.12 SNMPv2 Management Communication Class ..............   14
          2.13 SNMPv2 Access Control Policy .......................   14
          3 Elements of Procedure .................................   17
          3.1 Generating a Request ................................   17
          3.2 Processing a Received Communication .................   18
          3.3 Generating a Response ...............................   21





          Galvin & McCloghrie                                   [Page i]

RFC 1445 Administrative Model for SNMPv2 April 1993 4 Application of the Model .............................. 23 4.1 Non-Secure Minimal Agent Configuration .............. 23 4.2 Secure Minimal Agent Configuration .................. 26 4.3 MIB View Configurations ............................. 28 4.4 Proxy Configuration ................................. 32 4.4.1 Foreign Proxy Configuration ....................... 33 4.4.2 Native Proxy Configuration ........................ 37 4.5 Public Key Configuration ............................ 41 5 Security Considerations ............................... 44 6 Acknowledgements ...................................... 45 7 References ............................................ 46 8 Authors' Addresses .................................... 47 Galvin & McCloghrie [Page 1]
RFC 1445 Administrative Model for SNMPv2 April 1993 1. Introduction A network management system contains: several (potentially many) nodes, each with a processing entity, termed an agent, which has access to management instrumentation; at least one management station; and, a management protocol, used to convey management information between the agents and management stations. Operations of the protocol are carried out under an administrative framework which defines both authentication and authorization policies. Network management stations execute management applications which monitor and control network elements. Network elements are devices such as hosts, routers, terminal servers, etc., which are monitored and controlled through access to their management information. It is the purpose of this document, the Administrative Model for SNMPv2, to define how the administrative framework is applied to realize effective network management in a variety of configurations and environments. The model described here entails the use of distinct identities for peers that exchange SNMPv2 messages. Thus, it represents a departure from the community-based administrative model of the original SNMP [1]. By unambiguously identifying the source and intended recipient of each SNMPv2 message, this new strategy improves upon the historical community scheme both by supporting a more convenient access control model and allowing for effective use of asymmetric (public key) security protocols in the future. 1.1. A Note on Terminology For the purpose of exposition, the original Internet-standard Network Management Framework, as described in RFCs 1155, 1157, and 1212, is termed the SNMP version 1 framework (SNMPv1). The current framework is termed the SNMP version 2 framework (SNMPv2). Galvin & McCloghrie [Page 2]
RFC 1445 Administrative Model for SNMPv2 April 1993 2. Elements of the Model 2.1. SNMPv2 Party A SNMPv2 party is a conceptual, virtual execution environment whose operation is restricted (for security or other purposes) to an administratively defined subset of all possible operations of a particular SNMPv2 entity (see Section 2.2). Whenever a SNMPv2 entity processes a SNMPv2 message, it does so by acting as a SNMPv2 party and is thereby restricted to the set of operations defined for that party. The set of possible operations specified for a SNMPv2 party may be overlapping or disjoint with respect to the sets of other SNMPv2 parties; it may also be a proper or improper subset of all possible operations of the SNMPv2 entity. Architecturally, each SNMPv2 party comprises o a single, unique party identity, o a logical network location at which the party executes, characterized by a transport protocol domain and transport addressing information, o a single authentication protocol and associated parameters by which all protocol messages originated by the party are authenticated as to origin and integrity, and o a single privacy protocol and associated parameters by which all protocol messages received by the party are protected from disclosure. Galvin & McCloghrie [Page 3]
RFC 1445 Administrative Model for SNMPv2 April 1993 Conceptually, each SNMPv2 party may be represented by an ASN.1 value with the following syntax: SnmpParty ::= SEQUENCE { partyIdentity OBJECT IDENTIFIER, partyTDomain OBJECT IDENTIFIER, partyTAddress OCTET STRING, partyMaxMessageSize INTEGER, partyAuthProtocol OBJECT IDENTIFIER, partyAuthClock INTEGER, partyAuthPrivate OCTET STRING, partyAuthPublic OCTET STRING, partyAuthLifetime INTEGER, partyPrivProtocol OBJECT IDENTIFIER, partyPrivPrivate OCTET STRING, partyPrivPublic OCTET STRING } For each SnmpParty value that represents a SNMPv2 party, the following statements are true: o Its partyIdentity component is the party identity. o Its partyTDomain component is called the transport domain and indicates the kind of transport service by which the party receives network management traffic. An example of a transport domain is snmpUDPDomain (SNMPv2 over UDP, using SNMPv2 parties). o Its partyTAddress component is called the transport addressing information and represents a transport service address by which the party receives network management traffic. Galvin & McCloghrie [Page 4]
RFC 1445 Administrative Model for SNMPv2 April 1993 o Its partyMaxMessageSize component is called the maximum message size and represents the length in octets of the largest SNMPv2 message this party is prepared to accept. o Its partyAuthProtocol component is called the authentication protocol and identifies a protocol and a mechanism by which all messages generated by the party are authenticated as to integrity and origin. In this context, the value noAuth signifies that messages generated by the party are not authenticated as to integrity and origin. o Its partyAuthClock component is called the authentication clock and represents a notion of the current time that is specific to the party. The significance of this component is specific to the authentication protocol. o Its partyAuthPrivate component is called the private authentication key and represents any secret value needed to support the authentication protocol. The significance of this component is specific to the authentication protocol. o Its partyAuthPublic component is called the public authentication key and represents any public value that may be needed to support the authentication protocol. The significance of this component is specific to the authentication protocol. o Its partyAuthLifetime component is called the lifetime and represents an administrative upper bound on acceptable delivery delay for protocol messages generated by the party. The significance of this component is specific to the authentication protocol. o Its partyPrivProtocol component is called the privacy protocol and identifies a protocol and a mechanism by which all protocol messages received by the party are protected from disclosure. In this context, the value noPriv signifies that messages received by the party are not protected from disclosure. o Its partyPrivPrivate component is called the private privacy key and represents any secret value needed to support the privacy protocol. The significance of this Galvin & McCloghrie [Page 5]
RFC 1445 Administrative Model for SNMPv2 April 1993 component is specific to the privacy protocol. o Its partyPrivPublic component is called the public privacy key and represents any public value that may be needed to support the privacy protocol. The significance of this component is specific to the privacy protocol. If, for all SNMPv2 parties realized by a SNMPv2 entity, the authentication protocol is noAuth and the privacy protocol is noPriv, then that entity is called non-secure. 2.2. SNMPv2 Entity A SNMPv2 entity is an actual process which performs network management operations by generating and/or responding to SNMPv2 protocol messages in the manner specified in [2]. When a SNMPv2 entity is acting as a particular SNMPv2 party (see Section 2.1), the operation of that entity must be restricted to the subset of all possible operations that is administratively defined for that party. By definition, the operation of a SNMPv2 entity requires no concurrency between processing of any single protocol message (by a particular SNMPv2 party) and processing of any other protocol message (by a potentially different SNMPv2 party). Accordingly, implementation of a SNMPv2 entity to support more than one party need not be multi-threaded. However, there may be situations where implementors may choose to use multi- threading. Architecturally, every SNMPv2 entity maintains a local database that represents all SNMPv2 parties known to it - those whose operation is realized locally, those whose operation is realized by proxy interactions with remote parties or devices, and those whose operation is realized by remote entities. In addition, every SNMPv2 entity maintains a local database that represents all managed object resources (see Section 2.8) which are known to the SNMPv2 entity. Finally, every SNMPv2 entity maintains a local database that represents an access control policy (see Section 2.11) that defines the access privileges accorded to known SNMPv2 parties. Galvin & McCloghrie [Page 6]
RFC 1445 Administrative Model for SNMPv2 April 1993 2.3. SNMPv2 Management Station A SNMPv2 management station is the operational role assumed by a SNMPv2 party when it initiates SNMPv2 management operations by the generation of appropriate SNMPv2 protocol messages or when it receives and processes trap notifications. Sometimes, the term SNMPv2 management station is applied to partial implementations of the SNMPv2 (in graphics workstations, for example) that focus upon this operational role. Such partial implementations may provide for convenient, local invocation of management services, but they may provide little or no support for performing SNMPv2 management operations on behalf of remote protocol users. 2.4. SNMPv2 Agent A SNMPv2 agent is the operational role assumed by a SNMPv2 party when it performs SNMPv2 management operations in response to received SNMPv2 protocol messages such as those generated by a SNMPv2 management station (see Section 2.3). Sometimes, the term SNMPv2 agent is applied to partial implementations of the SNMPv2 (in embedded systems, for example) that focus upon this operational role. Such partial implementations provide for realization of SNMPv2 management operations on behalf of remote users of management services, but they may provide little or no support for local invocation of such services. 2.5. View Subtree A view subtree is the set of all MIB object instances which have a common ASN.1 OBJECT IDENTIFIER prefix to their names. A view subtree is identified by the OBJECT IDENTIFIER value which is the longest OBJECT IDENTIFIER prefix common to all (potential) MIB object instances in that subtree. When the OBJECT IDENTIFIER prefix identifying a view subtree is longer than the OBJECT IDENTIFIER of an object type defined according to the SMI [3], then the use of such a view subtree for access control has granularity at the object instance level. Such granularity is considered beyond the scope of a Galvin & McCloghrie [Page 7]
RFC 1445 Administrative Model for SNMPv2 April 1993 SNMPv2 entity acting in an agent role. As such, no implementation of a SNMPv2 entity acting in an agent role is required to support values of viewSubtree [6] which have more sub-identifiers than is necessary to identify a particular leaf object type. However, access control information is also used in determining which SNMPv2 entities acting in a manager role should receive trap notifications (Section 4.2.6 of [2]). As such, agent implementors might wish to provide instance- level granularity in order to allow a management station to use fine-grain configuration of trap notifications. 2.6. MIB View A MIB view is a subset of the set of all instances of all object types defined according to the SMI [3] (i.e., of the universal set of all instances of all MIB objects), subject to the following constraints: o Each element of a MIB view is uniquely named by an ASN.1 OBJECT IDENTIFIER value. As such, identically named instances of a particular object type (e.g., in different agents) must be contained within different MIB views. That is, a particular object instance name resolves within a particular MIB view to at most one object instance. o Every MIB view is defined as a collection of view subtrees. 2.7. Proxy Relationship A proxy relationship exists when, in order to process a received management request, a SNMPv2 entity must communicate with another, logically remote, entity. A SNMPv2 entity which processes management requests using a proxy relationship is termed a SNMPv2 proxy agent. When communication between a logically remote party and a SNMPv2 entity is via the SNMPv2 (over any transport protocol), then the proxy party is called a SNMPv2 native proxy relationship. Deployment of SNMPv2 native proxy relationships is a means whereby the processing or bandwidth costs of management may be amortized or shifted - thereby facilitating Galvin & McCloghrie [Page 8]
RFC 1445 Administrative Model for SNMPv2 April 1993 the construction of large management systems. When communication between a logically remote party and a SNMPv2 entity party is not via the SNMPv2, then the proxy party is called a SNMPv2 foreign proxy relationship. Deployment of foreign proxy relationships is a means whereby otherwise unmanageable devices or portions of an internet may be managed via the SNMPv2. The transparency principle that defines the behavior of a SNMPv2 entity in general applies in particular to a SNMPv2 proxy relationship: The manner in which one SNMPv2 entity processes SNMPv2 protocol messages received from another SNMPv2 entity is entirely transparent to the latter. The transparency principle derives directly from the historical SNMP philosophy of divorcing architecture from implementation. To this dichotomy are attributable many of the most valuable benefits in both the information and distribution models of the Internet-standard Network Management Framework, and it is the architectural cornerstone upon which large management systems may be built. Consistent with this philosophy, although the implementation of SNMPv2 proxy agents in certain environments may resemble that of a transport-layer bridge, this particular implementation strategy (or any other!) does not merit special recognition either in the SNMPv2 management architecture or in standard mechanisms for proxy administration. Implicit in the transparency principle is the requirement that the semantics of SNMPv2 management operations are preserved between any two SNMPv2 peers. In particular, the "as if simultaneous" semantics of a Set operation are extremely difficult to guarantee if its scope extends to management information resident at multiple network locations. For this reason, proxy configurations that admit Set operations that apply to information at multiple locations are discouraged, although such operations are not explicitly precluded by the architecture in those rare cases where they might be supported in a conformant way. Also implicit in the transparency principle is the requirement that, throughout its interaction with a proxy agent, a Galvin & McCloghrie [Page 9]
RFC 1445 Administrative Model for SNMPv2 April 1993 management station is supplied with no information about the nature or progress of the proxy mechanisms by which its requests are realized. That is, it should seem to the management station - except for any distinction in underlying transport address - as if it were interacting via SNMPv2 directly with the proxied device. Thus, a timeout in the communication between a proxy agent and its proxied device should be represented as a timeout in the communication between the management station and the proxy agent. Similarly, an error response from a proxied device should - as much as possible - be represented by the corresponding error response in the interaction between the proxy agent and management station. 2.8. SNMPv2 Context A SNMPv2 context is a collection of managed object resources accessible by a SNMPv2 entity. The object resources identified by a context are either local or remote. A SNMPv2 context referring to local object resources is identified as a MIB view. In this case, a SNMPv2 entity uses local mechanisms to access the management information identified by the SNMPv2 context. A remote SNMPv2 context referring to remote object resources is identified as a proxy relationship. In this case, a SNMPv2 entity acts as a proxy agent to access the management information identified by the SNMPv2 context. 2.9. SNMPv2 Management Communication A SNMPv2 management communication is a communication from one specified SNMPv2 party to a second specified SNMPv2 party about management information that is contained in a SNMPv2 context accessible by the appropriate SNMPv2 entity. In particular, a SNMPv2 management communication may be o a query by the originating party about information accessible to the addressed party (e.g., getRequest, getNextRequest, or getBulkRequest), Galvin & McCloghrie [Page 10]
RFC 1445 Administrative Model for SNMPv2 April 1993 o an indicative assertion to the addressed party about information accessible to the originating party (e.g., Response, InformRequest, or SNMPv2-Trap), o an imperative assertion by the originating party about information accessible to the addressed party (e.g., setRequest), or o a confirmation to the addressed party about information received by the originating party (e.g., a Response confirming an InformRequest). A management communication is represented by an ASN.1 value with the following syntax: SnmpMgmtCom ::= [2] IMPLICIT SEQUENCE { dstParty OBJECT IDENTIFIER, srcParty OBJECT IDENTIFIER, context OBJECT IDENTIFIER, pdu PDUs } For each SnmpMgmtCom value that represents a SNMPv2 management communication, the following statements are true: o Its dstParty component is called the destination and identifies the SNMPv2 party to which the communication is directed. o Its srcParty component is called the source and identifies the SNMPv2 party from which the communication is originated. o Its context component identifies the SNMPv2 context containing the management information referenced by the communication. o Its pdu component has the form and significance attributed to it in [2]. Galvin & McCloghrie [Page 11]
RFC 1445 Administrative Model for SNMPv2 April 1993 2.10. SNMPv2 Authenticated Management Communication A SNMPv2 authenticated management communication is a SNMPv2 management communication (see Section 2.9) for which the originating SNMPv2 party is (possibly) reliably identified and for which the integrity of the transmission of the communication is (possibly) protected. An authenticated management communication is represented by an ASN.1 value with the following syntax: SnmpAuthMsg ::= [1] IMPLICIT SEQUENCE { authInfo ANY, -- defined by authentication protocol authData SnmpMgmtCom } For each SnmpAuthMsg value that represents a SNMPv2 authenticated management communication, the following statements are true: o Its authInfo component is called the authentication information and represents information required in support of the authentication protocol used by the SNMPv2 party originating the message. The detailed significance of the authentication information is specific to the authentication protocol in use; it has no effect on the application semantics of the communication other than its use by the authentication protocol in determining whether the communication is authentic or not. o Its authData component is called the authentication data and represents a SNMPv2 management communication. Galvin & McCloghrie [Page 12]
RFC 1445 Administrative Model for SNMPv2 April 1993 2.11. SNMPv2 Private Management Communication A SNMPv2 private management communication is a SNMPv2 authenticated management communication (see Section 2.10) that is (possibly) protected from disclosure. A private management communication is represented by an ASN.1 value with the following syntax: SnmpPrivMsg ::= [1] IMPLICIT SEQUENCE { privDst OBJECT IDENTIFIER, privData [1] IMPLICIT OCTET STRING } For each SnmpPrivMsg value that represents a SNMPv2 private management communication, the following statements are true: o Its privDst component is called the privacy destination and identifies the SNMPv2 party to which the communication is directed. o Its privData component is called the privacy data and represents the (possibly encrypted) serialization (according to the conventions of [5]) of a SNMPv2 authenticated management communication (see Section 2.10). Galvin & McCloghrie [Page 13]
RFC 1445 Administrative Model for SNMPv2 April 1993 2.12. SNMPv2 Management Communication Class A SNMPv2 management communication class corresponds to a specific SNMPv2 PDU type defined in [2]. A management communication class is represented by an ASN.1 INTEGER value according to the type of the identifying PDU (see Table 1). Get 1 GetNext 2 Response 4 Set 8 -- unused 16 GetBulk 32 Inform 64 SNMPv2-Trap 128 Table 1: Management Communication Classes The value by which a communication class is represented is computed as 2 raised to the value of the ASN.1 context- specific tag for the appropriate SNMPv2 PDU. A set of management communication classes is represented by the ASN.1 INTEGER value that is the sum of the representations of the communication classes in that set. The null set is represented by the value zero. 2.13. SNMPv2 Access Control Policy A SNMPv2 access control policy is a specification of a local access policy in terms of a SNMPv2 context and the management communication classes which are authorized between a pair of SNMPv2 parties. Architecturally, such a specification comprises four parts: o the targets of SNMPv2 access control - the SNMPv2 parties that may perform management operations as requested by management communications received from other parties, o the subjects of SNMPv2 access control - the SNMPv2 parties that may request, by sending management Galvin & McCloghrie [Page 14]
RFC 1445 Administrative Model for SNMPv2 April 1993 communications to other parties, that management operations be performed, o the managed object resources of SNMPv2 access control - the SNMPv2 contexts which identify the management information on which requested management operations are to be performed, and o the policy that specifies the classes of SNMPv2 management communications pertaining to a particular SNMPv2 context that a particular target is authorized to accept from a particular subject. Conceptually, a SNMPv2 access policy is represented by a collection of ASN.1 values with the following syntax: AclEntry ::= SEQUENCE { aclTarget OBJECT IDENTIFIER, aclSubject OBJECT IDENTIFIER, aclResources OBJECT IDENTIFIER, aclPrivileges INTEGER } For each such value that represents one part of a SNMPv2 access policy, the following statements are true: o Its aclTarget component is called the target and identifies the SNMPv2 party to which the partial policy permits access. o Its aclSubject component is called the subject and identifies the SNMPv2 party to which the partial policy grants privileges. o Its aclResources component is called the managed object resources and identifies the SNMPv2 context referenced by the partial policy. o Its aclPrivileges component is called the privileges and represents a set of SNMPv2 management communication classes which, when they reference the specified SNMPv2 Galvin & McCloghrie [Page 15]
RFC 1445 Administrative Model for SNMPv2 April 1993 context, are authorized to be processed by the specified target party when received from the specified subject party. The application of SNMPv2 access control policy only occurs on receipt of management communications; it is not applied on transmission of management communications. Note, however, that ASN.1 values, having the syntax AclEntry, are also used in determining the destinations of a SNMPv2-Trap [2]. Galvin & McCloghrie [Page 16]
RFC 1445 Administrative Model for SNMPv2 April 1993 3. Elements of Procedure This section describes the procedures followed by a SNMPv2 entity in processing SNMPv2 messages. These procedures are independent of the particular authentication and privacy protocols that may be in use. 3.1. Generating a Request This section describes the procedure followed by a SNMPv2 entity whenever either a management request or a trap notification is to be transmitted by a SNMPv2 party. (1) A SnmpMgmtCom value is constructed for which the srcParty component identifies the originating party, for which the dstParty component identifies the receiving party, for which the context component identifies the desired SNMPv2 context, and for which the pdu component represents the desired management operation. (2) The local database of party information is consulted to determine the authentication protocol and other relevant information for the originating and receiving SNMPv2 parties. (3) A SnmpAuthMsg value is constructed with the following properties: Its authInfo component is constructed according to the authentication protocol specified for the originating party. In particular, if the authentication protocol for the originating SNMPv2 party is identified as noAuth, then this component corresponds to the OCTET STRING value of zero length. Its authData component is the constructed SnmpMgmtCom value. (4) The local database of party information is consulted to determine the privacy protocol and other relevant information for the receiving SNMPv2 party. Galvin & McCloghrie [Page 17]
RFC 1445 Administrative Model for SNMPv2 April 1993
RFC 1445 Administrative Model for SNMPv2 April 1993 Target Subject Context Privileges chico groucho ducksoup 35 (Get, GetNext & GetBulk) groucho chico ducksoup 132 (Response & SNMPv2-Trap) harpo zeppo bigstore 35 (Get, GetNext & GetBulk) zeppo harpo bigstore 132 (Response & SNMPv2-Trap) Table 15: Access Information for Native Proxy As represented in Table 13, the proxy agent party operates at UDP port 161 at IP address 1.2.3.5 using the party identity chico; the example manager operates at UDP port 2002 at IP address 1.2.3.4 using the identity groucho; the proxy source party operates at UDP port 161 at IP address 1.2.3.5 using the party identity zeppo; and, the proxy destination party operates at UDP port 161 at IP address 1.2.3.6 using the party identity harpo. Messages generated by all four SNMPv2 parties are authenticated as to origin and integrity by using the authentication protocol v2md5AuthProtocol and distinct, private authentication keys. Although these private authentication key values ("0123456789ABCDEF", "GHIJKL0123456789", "MNOPQR0123456789", and "STUVWX0123456789") are presented here for expository purposes, knowledge of private keys is not normally afforded to human beings and is confined to those portions of the protocol implementation that require it. Table 14 shows the proxy relationships known to the proxy agent. In particular, the SNMPv2 context ducksoup refers to a relationship that is satisfied when the SNMPv2 party zeppo communicates with the SNMPv2 party harpo and references the SNMPv2 context bigstore. In order to interrogate the proxied device associated with the party harpo, the management station groucho constructs a SNMPv2 GetNext request contained with a SnmpMgmtCom value which references the SNMPv2 context ducksoup, and transmits it to the party chico operating (see Table 11) at UDP port 161 and IP address 1.2.3.5. This request is authenticated using the private authentication key "0123456789ABCDEF". When that request is received by the party chico, the originator of the message is verified as being the party groucho by using local knowledge (see Table 13) of the private Galvin & McCloghrie [Page 39]
RFC 1445 Administrative Model for SNMPv2 April 1993 authentication key "0123456789ABCDEF". Because party groucho is authorized to issue GetNext (as well as Get and GetBulk) requests with respect to party chico and the SNMPv2 context ducksoup by the relevant access control policy (Table 15), the request is accepted. Because the local database of context information indicates that the SNMPv2 context ducksoup refers to a proxy relationship, the request is satisfied by its translation into a corresponding SNMPv2 GetNext request directed from party zeppo to party harpo referencing SNMPv2 context bigstore. This new communication is authenticated using the private authentication key "STUVWX0123456789" and transmitted to party harpo at the IP address 1.2.3.6. When this new request is received by the party harpo, the originator of the message is verified as being the party zeppo by using local knowledge of the private authentication key "STUVWX0123456789". Because party zeppo is authorized to issue GetNext (as well as Get and GetBulk) requests with respect to party harpo and the SNMPv2 context bigstore by the relevant access control policy (Table 15), the request is accepted. A SNMPv2 Response message representing the results of the query is then generated by party harpo to party zeppo referencing SNMPv2 context bigstore. This response communication is authenticated as to origin and integrity using the private authentication key "MNOPQR0123456789" and transmitted to party zeppo at IP address 1.2.3.5 (the source address for the corresponding request). When this response is received by party zeppo, the originator of the message is verified as being the party harpo by using local knowledge (see Table 13) of the private authentication key "MNOPQR0123456789". Because party harpo is authorized to issue Response communications with respect to party zeppo and SNMPv2 context bigstore by the relevant access control policy (Table 15), the response is accepted, and is used to construct a response to the original GetNext request, indicating a SNMPv2 context of ducksoup. This response, from party chico to party groucho, is authenticated as to origin and integrity using the private authentication key "GHIJKL0123456789" and is transmitted to the party groucho at IP address 1.2.3.4 (the source address for the original request). When this response is received by the party groucho, the originator of the message is verified as being the party chico by using local knowledge (see Table 13) of the private Galvin & McCloghrie [Page 40]
RFC 1445 Administrative Model for SNMPv2 April 1993 authentication key "GHIJKL0123456789". Because party chico is authorized to issue Response communications with respect to party groucho and SNMPv2 context ducksoup by the relevant access control policy (Table 15), the response is accepted, and the interrogation is complete. 4.5. Public Key Configuration This section presents an example configuration predicated upon a hypothetical security protocol. This hypothetical protocol would be based on asymmetric (public key) cryptography as a means for providing data origin authentication (but not protection against disclosure). This example illustrates the consistency of the administrative model with public key technology, and the extension of the example to support protection against disclosure should be apparent. Identity ollie stan (agent) (manager) Domain snmpUDPDomain snmpUDPDomain Address 1.2.3.4, 161 1.2.3.5, 2004 Auth Prot pkAuthProtocol pkAuthProtocol Auth Priv Key "0123456789ABCDEF" "" Auth Pub Key "0123456789abcdef" "ghijkl0123456789" Auth Clock 0 0 Auth Lifetime 300 300 Priv Prot noPriv noPriv Priv Priv Key "" "" Priv Pub Key "" "" Table 16: Party Information for Public Key Agent The example configuration comprises a single SNMPv2 agent that interacts with a single SNMPv2 management station. Tables 16 and 17 present information about SNMPv2 parties that is by the agent and manager, respectively, while Table 5 presents information about the local access policy that is known to both manager and agent. Galvin & McCloghrie [Page 41]
RFC 1445 Administrative Model for SNMPv2 April 1993 Identity ollie stan (agent) (manager) Domain snmpUDPDomain snmpUDPDomain Address 1.2.3.4, 161 1.2.3.5, 2004 Auth Prot pkAuthProtocol pkAuthProtocol Auth Priv Key "" "GHIJKL0123456789" Auth Pub Key "0123456789abcdef" "ghijkl0123456789" Auth Clock 0 0 Auth Lifetime 300 300 Priv Prot noPriv noPriv Priv Priv Key "" "" Priv Pub Key "" "" Table 17: Party Information for Public Key Management Station As represented in Table 16, the example agent party operates at UDP port 161 at IP address 1.2.3.4 using the party identity ollie; the example manager operates at UDP port 2004 at IP address 1.2.3.5 using the identity stan. Both ollie and stan authenticate all messages that they generate as to origin and integrity by using the hypothetical SNMPv2 authentication protocol pkAuthProtocol and their distinct, private authentication keys. Although these private authentication key values ("0123456789ABCDEF" and "GHIJKL0123456789") are presented here for expository purposes, knowledge of private keys is not normally afforded to human beings and is confined to those portions of the protocol implementation that require it. In most respects, the interaction between manager and agent in this configuration is almost identical to that in the example of the minimal, secure SNMPv2 agent described above. The most significant difference is that neither SNMPv2 party in the public key configuration has knowledge of the private key by which the other party authenticates its transmissions. Instead, for each received authenticated SNMPv2 communication, the identity of the originator is verified by applying an asymmetric cryptographic algorithm to the received message together with the public authentication key for the originating party. Thus, in this configuration, the agent knows the manager's public key ("ghijkl0123456789") but not its private key ("GHIJKL0123456789"); similarly, the manager knows the agent's public key ("0123456789abcdef") but not its Galvin & McCloghrie [Page 42]
RFC 1445 Administrative Model for SNMPv2 April 1993 private key ("0123456789ABCDEF"). Galvin & McCloghrie [Page 43]
RFC 1445 Administrative Model for SNMPv2 April 1993 5. Security Considerations In order to participate in the administrative model set forth in this memo, SNMPv2 implementations must support local, non- volatile storage of the local database of party information. Accordingly, every attempt has been made to minimize the amount of non-volatile storage required. Galvin & McCloghrie [Page 44]
RFC 1445 Administrative Model for SNMPv2 April 1993 6. Acknowledgements This document is based, almost entirely, on RFC 1351. Galvin & McCloghrie [Page 45]
RFC 1445 Administrative Model for SNMPv2 April 1993 7. References [1] Case, J., Fedor, M., Schoffstall, M., Davin, J., "Simple Network Management Protocol", STD 15, RFC 1157, SNMP Research, Performance Systems International, MIT Laboratory for Computer Science, May 1990. [2] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Protocol Operations for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1448, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993. [3] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Structure of Management Information for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1442, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993. [4] McCloghrie, K., and Galvin, J., "Party MIB for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1447, Hughes LAN Systems, Trusted Information Systems, April 1993. [5] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Transport Mappings for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1449, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993. [6] Galvin, J., and McCloghrie, K., "Security Protocols for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1446, Trusted Information Systems, Hughes LAN Systems, April 1993. [7] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Management Information Base for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1450, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993. Galvin & McCloghrie [Page 46]
RFC 1445 Administrative Model for SNMPv2 April 1993 8. Authors' Addresses James M. Galvin Trusted Information Systems, Inc. 3060 Washington Road, Route 97 Glenwood, MD 21738 Phone: +1 301 854-6889 EMail: galvin@tis.com



Back to RFC index

 

 



Sponsered-Sites:

Register domain name and transfer | Cheap webhosting service | Domain name registration

 

 

""