RFC 2575
View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)
RFC 2575: View-based Access Control Model (VACM) for SNMP 🦋✨
okay bestie, let's get into this one. It's RFC 2575, titled View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP), and it's giving main character energy 💅
Quick intel from the title block 🎀:
- Network Working Group
- Authors: B. Wijnen (IBM T. J. Watson Research), R. Presuhn (BMC Software, Inc.), and K. McCloghrie (Cisco Systems, Inc.)
- Category: Standards Track
- Date: April 1999
- Obsoletes: RFC 2275
- Updates: (none listed)
Status of this Memo 📜
So this doc is an Internet standards track protocol for the Internet community, and it's literally asking for discussion and suggestions for improvements 💖 For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1). Distribution of this memo is unlimited 🌈
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.Abstract 🫶
This document describes the View-based Access Control Model for use in the SNMP architecture [RFC2571]. It defines the Elements of Procedure for controlling access to management information. The document also includes a MIB for remotely managing the configuration parameters for the View-based Access Control Model, which is so useful ngl 🔥
Table of Contents 🧚
1. Introduction 2
1.2. Access Control 3
1.3. Local Configuration Datastore 3
2. Elements of the Model 3
2.1. Groups 3
2.2. securityLevel 4
2.3. Contexts 4
2.4. MIB Views and View Families 4
2.4.1. View Subtree 5
2.4.2. ViewTreeFamily 5
2.5. Access Policy 6
3. Elements of Procedure 6
3.1. Overview of isAccessAllowed Process 8
3.2. Processing the isAccessAllowed Service Request 9
4. Definitions 10
5. Intellectual Property 27
6. Acknowledgements 28
7. Security Considerations 29
7.1. Recommended Practices 29
7.2. Defining Groups 30
7.3. Conformance 30
7.4. Access to the SNMP-VIEW-BASED-ACM-MIB 30
8. References 31
9. Editors' Addresses 32
A.1. Installation Parameters 33
B. Change Log 37
C. Full Copyright Statement 381. Introduction ✨
okay so the Architecture for describing Internet Management Frameworks [RFC2571] says an SNMP engine is made up of these four things 👑
1) a Dispatcher
2) a Message Processing Subsystem,
3) a Security Subsystem, and
4) an Access Control Subsystem.Applications use the services of these subsystems 💅
It's important to get the SNMP architecture and its terminology down so you can see where the View-based Access Control Model fits in and how it talks to the other subsystems 🧠 The reader is expected to already know the description and terminology of the SNMP architecture, as defined in [RFC2571], so go read that first bestie 🙈
The Access Control Subsystem of an SNMP engine is responsible for checking whether a specific type of access (read, write, notify) to a particular object (instance) is allowed 🔐
So this document defines one specific model of the Access Control Subsystem, called the View-based Access Control Model. Note that it's not necessarily the only Access Control Model, so no one's gatekeeping 🌸
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] 🎀
1.2. Access Control 🦋
Access Control happens (either implicitly or explicitly) in an SNMP entity when it processes SNMP retrieval or modification request messages from an SNMP entity 💖 For example, a Command Responder application applies Access Control when it processes requests it got from a Command Generator application. These requests contain Read Class and Write Class PDUs as defined in [RFC2571] ✨
Access Control also happens in an SNMP entity when an SNMP notification message gets generated (by a Notification Originator application). These notification messages contain Notification Class PDUs as defined in [RFC2571] 🔔
The View-based Access Control Model defines a set of services that an application (such as a Command Responder or a Notification Originator application) can use for checking access rights. The application itself is responsible for making the proper service calls for access checking, so that's on them 💅
1.3. Local Configuration Datastore 🧚
To implement the model in this document, an SNMP entity needs to keep information about access rights and policies 🗂️ This information is part of the SNMP engine's Local Configuration Datastore (LCD). See [RFC2571] for the definition of LCD 💜
To let an SNMP entity's LCD be configured remotely, parts of the LCD need to be accessible as managed objects. The View-based Access Control Model Configuration MIB, which is a MIB module that defines these managed object types, is included in this document 🌈
2. Elements of the Model 💖
This section has the definitions that make up the access control service provided by the View-based Access Control Model 🎀
2.1. Groups 👑
A group is a set of zero or more <securityModel, securityName> tuples on whose behalf SNMP management objects can be accessed. A group defines the access rights given to all securityNames that belong to that group. The combination of a securityModel and a securityName maps to at most one group. A group is identified by a groupName 🫶
The Access Control module assumes that the securityName has already been authenticated as needed, and it doesn't do any further authentication of its own 🔐
The View-based Access Control Model uses the securityModel and the securityName as inputs to the Access Control module when it's called to check for access rights. It determines the groupName as a function of securityModel and securityName 🧠
2.2. securityLevel 🔥
Different access rights for members of a group can be defined for different levels of security, i.e., noAuthNoPriv, authNoPriv, and authPriv. The securityLevel identifies the level of security that will be assumed when checking for access rights. See the SNMP Architecture document [RFC2571] for a definition of securityLevel 💅
The View-based Access Control Model requires that the securityLevel is passed as input to the Access Control module when it's called to check for access rights ✨
2.3. Contexts 🌸
An SNMP context is a collection of management information that an SNMP entity can access. An item of management information may exist in more than one context. An SNMP entity can potentially access many contexts. Details about naming management information can be found in the SNMP Architecture document [RFC2571] 🗃️
The View-based Access Control Model defines a vacmContextTable that lists the locally available contexts by contextName 🦋
2.4. MIB Views and View Families 🧚♀️
For security reasons, it's often valuable to restrict the access rights of some groups to only a subset of the management information in the management domain 🔒 To provide this capability, access to a context goes through a "MIB view", which details a specific set of managed object types (and optionally, the specific instances of object types) within that context 💖
For example, for a given context there will typically always be one MIB view that gives access to all management information in that context. Often there will be other MIB views, each containing some subset of the information. So the access allowed for a group can be restricted in the desired way by specifying its rights in terms of the particular (subset) MIB view it can access within each appropriate context 🎀
Since managed object types (and their instances) are identified through the tree-like naming structure of ISO's OBJECT IDENTIFIERs [ISO-ASN.1, RFC2578], it's convenient to define a MIB view as a combination of a set of "view subtrees", where each view subtree is a subtree within the managed object naming tree 🌳 So a simple MIB view (e.g., all managed objects within the Internet Network Management Framework) can be defined as a single view subtree, while more complicated MIB views (e.g., all information relevant to a particular network interface) can be represented by the union of multiple view subtrees ✨
While any set of managed objects can be described by the union of some number of view subtrees, some situations could need a very large number of them. This could happen, for example, when you specify all columns in one conceptual row of a MIB table, because they would appear in separate subtrees (one per column), each with a very similar format 😭 Because the formats are similar, the required set of subtrees can easily be combined into one structure. This structure is named a family of view subtrees after the set of subtrees it conceptually represents. A family of view subtrees can either be included in or excluded from a MIB view 🫶
2.4.1. View Subtree 🦋
A view subtree is the set of all MIB object instances that share a common ASN.1 OBJECT IDENTIFIER prefix in their names 💜 A view subtree is identified by the OBJECT IDENTIFIER value that is the longest OBJECT IDENTIFIER prefix common to all (potential) MIB object instances in that subtree 🌈
2.4.2. ViewTreeFamily 🧚
A family of view subtrees is a pairing of an OBJECT IDENTIFIER value (called the family name) together with a bit string value (called the family mask). The family mask shows which sub-identifiers of the associated family name are significant to the family's definition 🔥
For each possible managed object instance, that instance belongs to a particular ViewTreeFamily if both of the following conditions are true:
- the OBJECT IDENTIFIER name of the managed object instance contains at least as many sub-identifiers as the family name does, and
- each sub-identifier in the OBJECT IDENTIFIER name of the managed object instance matches the corresponding sub-identifier of the family name whenever the corresponding bit of the associated family mask is non-zero.
When the configured value of the family mask is all ones, the view subtree family is identical to the single view subtree identified by the family name 💅
When the configured value of the family mask is shorter than needed to perform the above test, its value is implicitly extended with ones. So a view subtree family with a family mask of zero length always corresponds to a single view subtree 🌸
2.5. Access Policy 🧁
Okay bestie, so the View-based Access Control Model decides what a group is allowed to touch. A group is basically a squad of zero or more securityNames that all have the same access rights 👯♀️ For a particular context (identified by contextName) that a group (identified by groupName) wants into, using a particular securityModel and securityLevel, the group's rights come down to three views: a read-view, a write-view and a notify-view 💅
The read-view is the set of object instances the group is allowed to read 📖 Reading happens when a retrieval operation is processed, which is handling Read Class PDUs ✨
The write-view is the set of object instances the group is allowed to write ✍️ Writing happens when a write operation is processed, which is handling Write Class PDUs 🎀
The notify-view is the set of object instances the group is allowed to send in a notification 🔔 That's when sending a notification, aka sending Notification Class PDUs 🦋
3. Elements of Procedure 🎀
Okay so this section is the step-by-step for how an Access Control module that uses the View-based Access Control Model checks access rights whenever an application asks (like a Command Responder or a Notification Originator) 🧚 The abstract service primitive looks like this:
statusInformation = -- success or errorIndication
isAccessAllowed(
securityModel -- Security Model in use
securityName -- principal who wants access
securityLevel -- Level of Security
viewType -- read, write, or notify view
contextName -- context containing variableName
variableName -- OID for the managed object
)Here are the abstract data elements, bestie 💖
statusInformation- one of the following:accessAllowed- a MIB view was found and access is granted ✅notInView- a MIB view was found but access is denied 🙅♀️ ThevariableNameis not in the configured MIB view for the specifiedviewType(e.g., in the relevant entry in thevacmAccessTable).noSuchView- no MIB view found because no view has been configured for specifiedviewType(e.g., in the relevant entry in thevacmAccessTable).noSuchContext- no MIB view found because there's no entry in thevacmContextTablefor the specifiedcontextName💀noGroupName- no MIB view found because no entry has been configured in thevacmSecurityToGroupTablefor the specified combination ofsecurityModelandsecurityName.noAccessEntry- no MIB view found because no entry has been configured in thevacmAccessTablefor the specified combination ofcontextName,groupName(fromvacmSecurityToGroupTable),securityModelandsecurityLevel.otherError- failure, an undefined error occurred 😭
securityModel- the Security Model under which access is requested.securityName- the principal on whose behalf access is requested.securityLevel- the Level of Security under which access is requested.viewType- the view to be checked (read, write or notify).contextName- the context in which access is requested.variableName- the object instance to which access is requested.
3.1. Overview of isAccessAllowed Process 🗺️
This picture shows how the View-based Access Control Model makes its access decision, step by step 🌸
+--------------------------------------------------------------------+
| |
| +-> securityModel -+ |
| | (a) | |
| who -+ +-> groupName ----+ |
| (1) | | (x) | |
| +-> securityName --+ | |
| (b) | |
| | |
| where -> contextName ---------------------+ |
| (2) (e) | |
| | |
| | |
| +-> securityModel -------------------+ |
| | (a) | |
| how -+ +-> viewName -+ |
| (3) | | (y) | |
| +-> securityLevel -------------------+ | |
| (c) | +-> yes/no |
| | | decision |
| why ---> viewType (read/write/notify) ----+ | (z) |
| (4) (d) | |
| | |
| what --> object-type ------+ | |
| (5) (m) | | |
| +-> variableName (OID) ------+ |
| | (f) |
| which -> object-instance --+ |
| (6) (n) |
| |
+--------------------------------------------------------------------+How the decision for isAccessAllowed is made 🧠
- 1) The inputs to the isAccessAllowed service are:
- (a)
securityModel- the Security Model in use - (b)
securityName- the principal who wants to access - (c)
securityLevel- the Level of Security - (d)
viewType- read, write, or notify view - (e)
contextName- the context containingvariableName - (f)
variableName- the OID for the managed object, made up of:- object-type (m)
- object-instance (n)
- (a)
- 2) The partial "who" (1), represented by
securityModel(a) andsecurityName(b), is used as the indices (a,b) into the vacmSecurityToGroupTable to find a single entry that produces a group, represented bygroupName(x) 👀 - 3) The "where" (2), represented by
contextName(e), the "who" (thegroupName(x) from the previous step), and the "how" (3), represented bysecurityModel(a) andsecurityLevel(c), are used as indices (e,x,a,c) into the vacmAccessTable to find a single entry that contains three MIB views 🎯 - 4) The "why" (4), represented by
viewType(d), is used to pick the right MIB view, aviewName(y), from the vacmAccessEntry chosen in the previous step. ThatviewName(y) is an index into the vacmViewTreeFamilyTable and selects the set of entries that define the variableNames which are included in or excluded from the MIB view namedviewName(y) 🧩 - 5) The "what" (5) type of management data and the "which" (6) particular instance, represented by
variableName(f), gets checked to see if it's in the MIB view or not, which gives the yes/no decision (z) 🏁
3.2. Processing the isAccessAllowed Service Request 🔥
This is what an Access Control module does every time it gets an isAccessAllowed request 💅
- 1) The vacmContextTable is consulted for info about the SNMP context identified by
contextName. If that SNMP context isn't in the table, an errorIndication (noSuchContext) gets returned to the calling module 💀 - 2) The vacmSecurityToGroupTable is consulted to map
securityModelandsecurityNameto agroupName. If that combination isn't in the table, an errorIndication (noGroupName) gets returned to the calling module. - 3) The vacmAccessTable is consulted for info about the
groupName,contextName,securityModelandsecurityLevel. If that combination isn't in the table, an errorIndication (noAccessEntry) gets returned to the calling module. - 4) Now pick the view based on
viewType:- a) If the
viewTypeis "read", the read view gets used for checking access rights 📖 - b) If the
viewTypeis "write", the write view gets used for checking access rights ✍️ - c) If the
viewTypeis "notify", the notify view gets used for checking access rights 🔔
- a) If the
If the view to be used is the empty view (zero length viewName), an errorIndication (noSuchView) gets returned to the calling module 🫠
- 5) Last step, the final check 🏆
- a) If there's no view configured for the specified
viewType, an errorIndication (noSuchView) gets returned to the calling module. - b) If the specified
variableName(object instance) is not in the MIB view (see the DESCRIPTION clause for vacmViewTreeFamilyTable in section 4), an errorIndication (notInView) gets returned to the calling module 🙈
- a) If there's no view configured for the specified
Otherwise,
- c) The specified
variableNameis in the MIB view, so a statusInformation of success (accessAllowed) is returned to the calling module 🎉
4. Definitions ✨
Okay, the MIB module starts here, and this is where the actual definitions begin 🧚 The module header goes like this:
SNMP-VIEW-BASED-ACM-MIB DEFINITIONS ::= BEGINokay so the IMPORTS block is basically the bestie list 🧚 it says which definitions we're borrowing from other MIB modules, and then the actual module starts ✨
IMPORTS
MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF
MODULE-IDENTITY, OBJECT-TYPE,
snmpModules FROM SNMPv2-SMI
TestAndIncr,
RowStatus, StorageType FROM SNMPv2-TC
SnmpAdminString,
SnmpSecurityLevel,
SnmpSecurityModel FROM SNMP-FRAMEWORK-MIB;
snmpVacmMIB MODULE-IDENTITY
LAST-UPDATED "9901200000Z" -- 20 Jan 1999, midnight
ORGANIZATION "SNMPv3 Working Group"
CONTACT-INFO "WG-email: snmpv3@lists.tislabs.com
Subscribe: majordomo@lists.tislabs.com
In message body: subscribe snmpv3
Chair: Russ Mundy
Trusted Information Systems
postal: 3060 Washington Rd
Glenwood MD 21738
USA
email: mundy@tislabs.com
phone: +1-301-854-6889
Co-editor: Bert Wijnen
IBM T.J. Watson Research
postal: Schagen 33
3461 GL Linschoten
Netherlands
email: wijnen@vnet.ibm.com
phone: +31-348-432-794
Co-editor: Randy Presuhn
BMC Software, Inc
postal: 965 Stewart Drive
Sunnyvale, CA 94086
USA
email: randy_presuhn@bmc.com
phone: +1-408-616-3100
Co-editor: Keith McCloghrie
Cisco Systems, Inc.
postal: 170 West Tasman Drive
San Jose, CA 95134-1706
USA
email: kzm@cisco.com
phone: +1-408-526-5260
"
DESCRIPTION "The management information definitions for the
View-based Access Control Model for SNMP.
"
-- Revision history
REVISION "9901200000Z" -- 20 Jan 1999, midnight
DESCRIPTION "Clarifications, published as RFC2575"
REVISION "9711200000Z" -- 20 Nov 1997, midnight
DESCRIPTION "Initial version, published as RFC2275"
::= { snmpModules 16 }
-- Administrative assignments ****************************************
vacmMIBObjects OBJECT IDENTIFIER ::= { snmpVacmMIB 1 }
vacmMIBConformance OBJECT IDENTIFIER ::= { snmpVacmMIB 2 }
-- Information about Local Contexts **********************************
vacmContextTable OBJECT-TYPE
SYNTAX SEQUENCE OF VacmContextEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The table of locally available contexts.
This table provides information to SNMP Command
Generator applications so that they can properly
configure the vacmAccessTable to control access to
all contexts at the SNMP entity.
This table may change dynamically if the SNMP entity
allows that contexts are added/deleted dynamically
(for instance when its configuration changes). Such
changes would happen only if the management
instrumentation at that SNMP entity recognizes more
(or fewer) contexts.
The presence of entries in this table and of entries
in the vacmAccessTable are independent. That is, a
context identified by an entry in this table is not
necessarily referenced by any entries in the
vacmAccessTable; and the context(s) referenced by an
entry in the vacmAccessTable does not necessarily
currently exist and thus need not be identified by an
entry in this table.
This table must be made accessible via the default
context so that Command Responder applications have
a standard way of retrieving the information.
This table is read-only. It cannot be configured via
SNMP.
"
::= { vacmMIBObjects 1 }
vacmContextEntry OBJECT-TYPE
SYNTAX VacmContextEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "Information about a particular context."
INDEX {
vacmContextName
}
::= { vacmContextTable 1 }
VacmContextEntry ::= SEQUENCE
{
vacmContextName SnmpAdminString
}
vacmContextName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS read-only
STATUS current
DESCRIPTION "A human readable name identifying a particular
context at a particular SNMP entity.
The empty contextName (zero length) represents the
default context.
"
::= { vacmContextEntry 1 }
-- Information about Groups ******************************************
vacmSecurityToGroupTable OBJECT-TYPE
SYNTAX SEQUENCE OF VacmSecurityToGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "This table maps a combination of securityModel and
securityName into a groupName which is used to define
an access control policy for a group of principals.
"
::= { vacmMIBObjects 2 }
vacmSecurityToGroupEntry OBJECT-TYPE
SYNTAX VacmSecurityToGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An entry in this table maps the combination of a
securityModel and securityName into a groupName.
"
INDEX {
vacmSecurityModel,
vacmSecurityName
}
::= { vacmSecurityToGroupTable 1 }
VacmSecurityToGroupEntry ::= SEQUENCE
{
vacmSecurityModel SnmpSecurityModel,
vacmSecurityName SnmpAdminString,
vacmGroupName SnmpAdminString,
vacmSecurityToGroupStorageType StorageType,
vacmSecurityToGroupStatus RowStatus
}
vacmSecurityModel OBJECT-TYPE
SYNTAX SnmpSecurityModel(1..2147483647)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The Security Model, by which the vacmSecurityName
referenced by this entry is provided.
Note, this object may not take the 'any' (0) value.
"
::= { vacmSecurityToGroupEntry 1 }
vacmSecurityName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The securityName for the principal, represented in a
Security Model independent format, which is mapped by
this entry to a groupName.
"
::= { vacmSecurityToGroupEntry 2 }
vacmGroupName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The name of the group to which this entry (e.g., the
combination of securityModel and securityName)
belongs.
This groupName is used as index into the
vacmAccessTable to select an access control policy.
However, a value in this table does not imply that an
instance with the value exists in table vacmAccesTable.
"
::= { vacmSecurityToGroupEntry 3 }
vacmSecurityToGroupStorageType OBJECT-TYPE
SYNTAX StorageType
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The storage type for this conceptual row.
Conceptual rows having the value 'permanent' need not
allow write-access to any columnar objects in the row.
"
DEFVAL { nonVolatile }
::= { vacmSecurityToGroupEntry 4 }
vacmSecurityToGroupStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The status of this conceptual row.
Until instances of all corresponding columns are
appropriately configured, the value of the
corresponding instance of the vacmSecurityToGroupStatus
column is 'notReady'.
In particular, a newly created row cannot be made
active until a value has been set for vacmGroupName.
The RowStatus TC [RFC2579] requires that this
DESCRIPTION clause states under which circumstances
other objects in this row can be modified:
The value of this object has no effect on whether
other objects in this conceptual row can be modified.
"
::= { vacmSecurityToGroupEntry 5 }🎀 the groups part is where we map who's asking (securityModel + securityName) onto a groupName, and then that groupName is what the access rules hang off of 💖 okay now for the big one, the access rights section 🔥
-- Information about Access Rights ***********************************
vacmAccessTable OBJECT-TYPE
SYNTAX SEQUENCE OF VacmAccessEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The table of access rights for groups.
Each entry is indexed by a groupName, a contextPrefix,
a securityModel and a securityLevel. To determine
whether access is allowed, one entry from this table
needs to be selected and the proper viewName from that
entry must be used for access control checking.
To select the proper entry, follow these steps:
1) the set of possible matches is formed by the
intersection of the following sets of entries:
the set of entries with identical vacmGroupName
the union of these two sets:
- the set with identical vacmAccessContextPrefix
- the set of entries with vacmAccessContextMatch
value of 'prefix' and matching
vacmAccessContextPrefix
intersected with the union of these two sets:
- the set of entries with identical
vacmSecurityModel
- the set of entries with vacmSecurityModel
value of 'any'
intersected with the set of entries with
vacmAccessSecurityLevel value less than or equal
to the requested securityLevel
2) if this set has only one member, we're done
otherwise, it comes down to deciding how to weight
the preferences between ContextPrefixes,
SecurityModels, and SecurityLevels as follows:
a) if the subset of entries with securityModel
matching the securityModel in the message is
not empty, then discard the rest.
b) if the subset of entries with
vacmAccessContextPrefix matching the contextName
in the message is not empty,
then discard the rest
c) discard all entries with ContextPrefixes shorter
than the longest one remaining in the set
d) select the entry with the highest securityLevel
Please note that for securityLevel noAuthNoPriv, all
groups are really equivalent since the assumption that
the securityName has been authenticated does not hold.
"
::= { vacmMIBObjects 4 }Okay bestie, now we get to the actual access rules, the part where the permissions get decided 💅🎀
vacmAccessEntry OBJECT-TYPE
SYNTAX VacmAccessEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An access right configured in the Local Configuration
Datastore (LCD) authorizing access to an SNMP context.
Entries in this table can use an instance value for
object vacmGroupName even if no entry in table
vacmAccessSecurityToGroupTable has a corresponding
value for object vacmGroupName.
"
INDEX { vacmGroupName,
vacmAccessContextPrefix,
vacmAccessSecurityModel,
vacmAccessSecurityLevel
}
::= { vacmAccessTable 1 }
VacmAccessEntry ::= SEQUENCE
{
vacmAccessContextPrefix SnmpAdminString,
vacmAccessSecurityModel SnmpSecurityModel,
vacmAccessSecurityLevel SnmpSecurityLevel,
vacmAccessContextMatch INTEGER,
vacmAccessReadViewName SnmpAdminString,
vacmAccessWriteViewName SnmpAdminString,
vacmAccessNotifyViewName SnmpAdminString,
vacmAccessStorageType StorageType,
vacmAccessStatus RowStatus
}
vacmAccessContextPrefix OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "In order to gain the access rights allowed by this
conceptual row, a contextName must match exactly
(if the value of vacmAccessContextMatch is 'exact')
or partially (if the value of vacmAccessContextMatch
is 'prefix') to the value of the instance of this
object.
"
::= { vacmAccessEntry 1 }
vacmAccessSecurityModel OBJECT-TYPE
SYNTAX SnmpSecurityModel
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "In order to gain the access rights allowed by this
conceptual row, this securityModel must be in use.
"
::= { vacmAccessEntry 2 }
vacmAccessSecurityLevel OBJECT-TYPE
SYNTAX SnmpSecurityLevel
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The minimum level of security required in order to
gain the access rights allowed by this conceptual
row. A securityLevel of noAuthNoPriv is less than
authNoPriv which in turn is less than authPriv.
If multiple entries are equally indexed except for
this vacmAccessSecurityLevel index, then the entry
which has the highest value for
vacmAccessSecurityLevel is selected.
"
::= { vacmAccessEntry 3 }
vacmAccessContextMatch OBJECT-TYPE
SYNTAX INTEGER
{ exact (1), -- exact match of prefix and contextName
prefix (2) -- Only match to the prefix
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION "If the value of this object is exact(1), then all
rows where the contextName exactly matches
vacmAccessContextPrefix are selected.
If the value of this object is prefix(2), then all
rows where the contextName whose starting octets
exactly match vacmAccessContextPrefix are selected.
This allows for a simple form of wildcarding.
"
DEFVAL { exact }
::= { vacmAccessEntry 4 }
vacmAccessReadViewName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The value of an instance of this object identifies
the MIB view of the SNMP context to which this
conceptual row authorizes read access.
The identified MIB view is that one for which the
vacmViewTreeFamilyViewName has the same value as the
instance of this object; if the value is the empty
string or if there is no active MIB view having this
value of vacmViewTreeFamilyViewName, then no access
is granted.
"
DEFVAL { ''H } -- the empty string
::= { vacmAccessEntry 5 }
vacmAccessWriteViewName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The value of an instance of this object identifies
the MIB view of the SNMP context to which this
conceptual row authorizes write access.
The identified MIB view is that one for which the
vacmViewTreeFamilyViewName has the same value as the
instance of this object; if the value is the empty
string or if there is no active MIB view having this
value of vacmViewTreeFamilyViewName, then no access
is granted.
"
DEFVAL { ''H } -- the empty string
::= { vacmAccessEntry 6 }
vacmAccessNotifyViewName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The value of an instance of this object identifies
the MIB view of the SNMP context to which this
conceptual row authorizes access for notifications.
The identified MIB view is that one for which the
vacmViewTreeFamilyViewName has the same value as the
instance of this object; if the value is the empty
string or if there is no active MIB view having this
value of vacmViewTreeFamilyViewName, then no access
is granted.
"
DEFVAL { ''H } -- the empty string
::= { vacmAccessEntry 7 }
vacmAccessStorageType OBJECT-TYPE
SYNTAX StorageType
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The storage type for this conceptual row.
Conceptual rows having the value 'permanent' need not
allow write-access to any columnar objects in the row.
"
DEFVAL { nonVolatile }
::= { vacmAccessEntry 8 }
vacmAccessStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The status of this conceptual row.
The RowStatus TC [RFC2579] requires that this
DESCRIPTION clause states under which circumstances
other objects in this row can be modified:
The value of this object has no effect on whether
other objects in this conceptual row can be modified.
"
::= { vacmAccessEntry 9 }
-- Information about MIB views ***************************************
-- Support for instance-level granularity is optional.
--
-- In some implementations, instance-level access control
-- granularity may come at a high performance cost. Managers
-- should avoid requesting such configurations unnecessarily.
vacmMIBViews OBJECT IDENTIFIER ::= { vacmMIBObjects 5 }
vacmViewSpinLock OBJECT-TYPE
SYNTAX TestAndIncr
MAX-ACCESS read-write
STATUS current
DESCRIPTION "An advisory lock used to allow cooperating SNMP
Command Generator applications to coordinate their
use of the Set operation in creating or modifying
views.
When creating a new view or altering an existing
view, it is important to understand the potential
interactions with other uses of the view. The
vacmViewSpinLock should be retrieved. The name of
the view to be created should be determined to be
unique by the SNMP Command Generator application by
consulting the vacmViewTreeFamilyTable. Finally,
the named view may be created (Set), including the
advisory lock.
If another SNMP Command Generator application has
altered the views in the meantime, then the spin
lock's value will have changed, and so this creation
will fail because it will specify the wrong value for
the spin lock.
Since this is an advisory lock, the use of this lock
is not enforced.
"
::= { vacmMIBViews 1 }Next up: the MIB views table, where things get even more fun 🦋
okay so this is where the view trees get spicy 🌈 the table is basically a big list of "included" and "excluded" subtrees, and the entries are what decide who gets to see what 👀
vacmViewTreeFamilyTable OBJECT-TYPE
SYNTAX SEQUENCE OF VacmViewTreeFamilyEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "Locally held information about families of subtrees
within MIB views.
Each MIB view is defined by two sets of view subtrees:
- the included view subtrees, and
- the excluded view subtrees.
Every such view subtree, both the included and the
excluded ones, is defined in this table.
To determine if a particular object instance is in
a particular MIB view, compare the object instance's
OBJECT IDENTIFIER with each of the MIB view's active
entries in this table. If none match, then the
object instance is not in the MIB view. If one or
more match, then the object instance is included in,
or excluded from, the MIB view according to the
value of vacmViewTreeFamilyType in the entry whose
value of vacmViewTreeFamilySubtree has the most
sub-identifiers. If multiple entries match and have
the same number of sub-identifiers (when wildcarding
is specified with the value of vacmViewTreeFamilyMask),
then the lexicographically greatest instance of
vacmViewTreeFamilyType determines the inclusion or
exclusion.
An object instance's OBJECT IDENTIFIER X matches an
active entry in this table when the number of
sub-identifiers in X is at least as many as in the
value of vacmViewTreeFamilySubtree for the entry,
and each sub-identifier in the value of
vacmViewTreeFamilySubtree matches its corresponding
sub-identifier in X. Two sub-identifiers match
either if the corresponding bit of the value of
vacmViewTreeFamilyMask for the entry is zero (the
'wild card' value), or if they are equal.
A 'family' of subtrees is the set of subtrees defined
by a particular combination of values of
vacmViewTreeFamilySubtree and vacmViewTreeFamilyMask.
In the case where no 'wild card' is defined in the
vacmViewTreeFamilyMask, the family of subtrees reduces
to a single subtree.
When creating or changing MIB views, an SNMP Command
Generator application should utilize the
vacmViewSpinLock to try to avoid collisions. See
DESCRIPTION clause of vacmViewSpinLock.
When creating MIB views, it is strongly advised that
first the 'excluded' vacmViewTreeFamilyEntries are
created and then the 'included' entries.
When deleting MIB views, it is strongly advised that
first the 'included' vacmViewTreeFamilyEntries are
deleted and then the 'excluded' entries.
If a create for an entry for instance-level access
control is received and the implementation does not
support instance-level granularity, then an
inconsistentName error must be returned.
"
::= { vacmMIBViews 2 }
vacmViewTreeFamilyEntry OBJECT-TYPE
SYNTAX VacmViewTreeFamilyEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "Information on a particular family of view subtrees
included in or excluded from a particular SNMP
context's MIB view.
Implementations must not restrict the number of
families of view subtrees for a given MIB view,
except as dictated by resource constraints on the
overall number of entries in the
vacmViewTreeFamilyTable.
If no conceptual rows exist in this table for a given
MIB view (viewName), that view may be thought of as
consisting of the empty set of view subtrees.
"
INDEX { vacmViewTreeFamilyViewName,
vacmViewTreeFamilySubtree
}
::= { vacmViewTreeFamilyTable 1 }
VacmViewTreeFamilyEntry ::= SEQUENCE
{
vacmViewTreeFamilyViewName SnmpAdminString,
vacmViewTreeFamilySubtree OBJECT IDENTIFIER,
vacmViewTreeFamilyMask OCTET STRING,
vacmViewTreeFamilyType INTEGER,
vacmViewTreeFamilyStorageType StorageType,
vacmViewTreeFamilyStatus RowStatus
}
vacmViewTreeFamilyViewName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The human readable name for a family of view subtrees.
"
::= { vacmViewTreeFamilyEntry 1 }
vacmViewTreeFamilySubtree OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The MIB subtree which when combined with the
corresponding instance of vacmViewTreeFamilyMask
defines a family of view subtrees.
"
::= { vacmViewTreeFamilyEntry 2 }
vacmViewTreeFamilyMask OBJECT-TYPE
SYNTAX OCTET STRING (SIZE (0..16))
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The bit mask which, in combination with the
corresponding instance of vacmViewTreeFamilySubtree,
defines a family of view subtrees.
Each bit of this bit mask corresponds to a
sub-identifier of vacmViewTreeFamilySubtree, with the
most significant bit of the i-th octet of this octet
string value (extended if necessary, see below)
corresponding to the (8*i - 7)-th sub-identifier, and
the least significant bit of the i-th octet of this
octet string corresponding to the (8*i)-th
sub-identifier, where i is in the range 1 through 16.
Each bit of this bit mask specifies whether or not
the corresponding sub-identifiers must match when
determining if an OBJECT IDENTIFIER is in this
family of view subtrees; a '1' indicates that an
exact match must occur; a '0' indicates 'wild card',
i.e., any sub-identifier value matches.
Thus, the OBJECT IDENTIFIER X of an object instance
is contained in a family of view subtrees if, for
each sub-identifier of the value of
vacmViewTreeFamilySubtree, either:
the i-th bit of vacmViewTreeFamilyMask is 0, or
the i-th sub-identifier of X is equal to the i-th
sub-identifier of the value of
vacmViewTreeFamilySubtree.
If the value of this bit mask is M bits long and
there are more than M sub-identifiers in the
corresponding instance of vacmViewTreeFamilySubtree,
then the bit mask is extended with 1's to be the
required length.
Note that when the value of this object is the
zero-length string, this extension rule results in
a mask of all-1's being used (i.e., no 'wild card'),
and the family of view subtrees is the one view
subtree uniquely identified by the corresponding
instance of vacmViewTreeFamilySubtree.
Note that masks of length greater than zero length
do not need to be supported. In this case this
object is made read-only.
"
DEFVAL { ''H }
::= { vacmViewTreeFamilyEntry 3 }
vacmViewTreeFamilyType OBJECT-TYPE
SYNTAX INTEGER { included(1), excluded(2) }
MAX-ACCESS read-create
STATUS current
DESCRIPTION "Indicates whether the corresponding instances of
vacmViewTreeFamilySubtree and vacmViewTreeFamilyMask
define a family of view subtrees which is included in
or excluded from the MIB view.
"
DEFVAL { included }
::= { vacmViewTreeFamilyEntry 4 }
vacmViewTreeFamilyStorageType OBJECT-TYPE
SYNTAX StorageType
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The storage type for this conceptual row.
Conceptual rows having the value 'permanent' need not
allow write-access to any columnar objects in the row.
"
DEFVAL { nonVolatile }
::= { vacmViewTreeFamilyEntry 5 }
vacmViewTreeFamilyStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION "The status of this conceptual row.
The RowStatus TC [RFC2579] requires that this
DESCRIPTION clause states under which circumstances
other objects in this row can be modified:
The value of this object has no effect on whether
other objects in this conceptual row can be modified.
"
::= { vacmViewTreeFamilyEntry 6 }
-- Conformance information *******************************************
vacmMIBCompliances OBJECT IDENTIFIER ::= { vacmMIBConformance 1 }
vacmMIBGroups OBJECT IDENTIFIER ::= { vacmMIBConformance 2 }
-- Compliance statements *********************************************
vacmMIBCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION "The compliance statement for SNMP engines which
implement the SNMP View-based Access Control Model
configuration MIB.
"
MODULE -- this module
MANDATORY-GROUPS { vacmBasicGroup }
OBJECT vacmAccessContextMatch
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmAccessReadViewName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmAccessWriteViewName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmAccessNotifyViewName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmAccessStorageType
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmAccessStatus
MIN-ACCESS read-only
DESCRIPTION "Create/delete/modify access to the
vacmAccessTable is not required.
"
OBJECT vacmViewTreeFamilyMask
WRITE-SYNTAX OCTET STRING (SIZE (0))
MIN-ACCESS read-only
DESCRIPTION "Support for configuration via SNMP of subtree
families using wild-cards is not required.
"
OBJECT vacmViewTreeFamilyType
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmViewTreeFamilyStorageType
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT vacmViewTreeFamilyStatus
MIN-ACCESS read-only
DESCRIPTION "Create/delete/modify access to the
vacmViewTreeFamilyTable is not required.
"
::= { vacmMIBCompliances 1 }
-- Units of conformance **********************************************vacmBasicGroup OBJECT-GROUP
OBJECTS {
vacmContextName,
vacmGroupName,
vacmSecurityToGroupStorageType,
vacmSecurityToGroupStatus,
vacmAccessContextMatch,
vacmAccessReadViewName,
vacmAccessWriteViewName,
vacmAccessNotifyViewName,
vacmAccessStorageType,
vacmAccessStatus,
vacmViewSpinLock,
vacmViewTreeFamilyMask,
vacmViewTreeFamilyType,
vacmViewTreeFamilyStorageType,
vacmViewTreeFamilyStatus
}
STATUS current
DESCRIPTION "A collection of objects providing for remote
configuration of an SNMP engine which implements
the SNMP View-based Access Control Model.
"
::= { vacmMIBGroups 1 }
END5. Intellectual Property 🔥
Okay, legal corner, but it's actually important 💅. The IETF doesn't take a side on whether any intellectual property or other rights someone claims over the tech in this doc are valid, how far they reach, or whether you can get a license for them. It also doesn't say it has gone looking for those rights 🙈. If you want the IETF's rules on rights for standards-track and standards-related docs, check out BCP-11 📚. Copies of any claims of rights that were filed for publication, plus any promises to grant licenses, or the outcome of someone trying to get a general license or permission to use those proprietary rights (for implementers or users of this spec), can all be requested from the IETF Secretariat 🎀.
The IETF also invites anyone interested to flag any copyrights, patents, patent applications, or other proprietary rights that might cover technology you'd need to practice this standard 🦋. Send that info to the IETF Executive Director ✨.
6. Acknowledgements 🫶
This doc is the result of the hard work of the SNMPv3 Working Group 💜. Huge shoutouts to these SNMPv3 WG members, who deserve all the praise:
- Harald Tveit Alvestrand (Maxware)
- Dave Battle (SNMP Research, Inc.)
- Alan Beard (Disney Worldwide Services)
- Paul Berrevoets (SWI Systemware/Halcyon Inc.)
- Martin Bjorklund (Ericsson)
- Uri Blumenthal (IBM T.J. Watson Research Center)
- Jeff Case (SNMP Research, Inc.)
- John Curran (BBN)
- Mike Daniele (Compaq Computer Corporation)
- T. Max Devlin (Eltrax Systems)
- John Flick (Hewlett Packard)
- Rob Frye (MCI)
- Wes Hardaker (U.C.Davis, Information Technology - D.C.A.S.)
- David Harrington (Cabletron Systems Inc.)
- Lauren Heintz (BMC Software, Inc.)
- N.C. Hien (IBM T.J. Watson Research Center)
- Michael Kirkham (InterWorking Labs, Inc.)
- Dave Levi (SNMP Research, Inc.)
- Louis A Mamakos (UUNET Technologies Inc.)
- Joe Marzot (Nortel Networks)
- Paul Meyer (Secure Computing Corporation)
- Keith McCloghrie (Cisco Systems)
- Bob Moore (IBM)
- Russ Mundy (TIS Labs at Network Associates)
- Bob Natale (ACE*COMM Corporation)
- Mike O'Dell (UUNET Technologies Inc.)
- Dave Perkins (DeskTalk)
- Peter Polkinghorne (Brunel University)
- Randy Presuhn (BMC Software, Inc.)
- David Reeder (TIS Labs at Network Associates)
- David Reid (SNMP Research, Inc.)
- Aleksey Romanov (Quality Quorum)
- Shawn Routhier (Epilogue)
- Juergen Schoenwaelder (TU Braunschweig)
- Bob Stewart (Cisco Systems)
- Mike Thatcher (Independent Consultant)
- Bert Wijnen (IBM T.J. Watson Research Center)
The design is based on recommendations from the IETF Security and Administrative Framework Evolution for SNMP Advisory Team 🌸. The members of that Advisory Team were:
- David Harrington (Cabletron Systems Inc.)
- Jeff Johnson (Cisco Systems)
- David Levi (SNMP Research Inc.)
- John Linn (Openvision)
- Russ Mundy (Trusted Information Systems) chair
- Shawn Routhier (Epilogue)
- Glenn Waters (Nortel)
- Bert Wijnen (IBM T. J. Watson Research Center)
As recommended by the Advisory Team and the SNMPv3 Working Group Charter, the design pulls in as much as is practical from previous RFCs and drafts 🧚. So a special thank you goes to the authors of the earlier designs known as SNMPv2u and SNMPv2* 👑:
- Jeff Case (SNMP Research, Inc.)
- David Harrington (Cabletron Systems Inc.)
- David Levi (SNMP Research, Inc.)
- Keith McCloghrie (Cisco Systems)
- Brian O'Keefe (Hewlett Packard)
- Marshall T. Rose (Dover Beach Consulting)
- Jon Saperia (BGS Systems Inc.)
- Steve Waldbusser (International Network Services)
- Glenn W. Waters (Bell-Northern Research Ltd.)
7. Security Considerations 💀
Okay, this is the serious part, bestie, so we're keeping it real 😭.
7.1. Recommended Practices
This doc is meant for use in the SNMP architecture ✨. The View-based Access Control Model described here checks access rights to management information based on:
- contextName, representing a set of management information at the managed system where the Access Control module is running.
- groupName, representing a set of zero or more securityNames. The combination of a securityModel and a securityName is mapped into a group in the View-based Access Control Model.
- securityModel under which access is requested.
- securityLevel under which access is requested.
- operation performed on the management information.
- MIB views for read, write or notify access.
When the User-based Access Control module is called to check access rights, it's assumed that the calling module already made sure the authentication and privacy aspects match the securityLevel being passed in 🔐.
When you create or delete entries in the vacmViewTreeFamilyTable, the order matters a LOT 😳. Follow the sequence recommended in the DESCRIPTION clause of the vacmViewTreeFamilyTable definition. If you don't, unwanted access might get granted while the entries are changing 🚨.
7.2. Defining Groups
The groupNames are used to give access to a group of zero or more securityNames 🍓. In the View-Based Access Control Model, a groupName counts as existing if it's listed in the vacmSecurityToGroupTable.
By mapping a securityModel and securityName combo into a groupName, an SNMP Command Generator application can add or delete securityNames to and from a group, as long as proper access is allowed 🦋.
Also, it's really important to realize that grouping <securityModel, securityName> tuples in the vacmSecurityToGroupTable does NOT take securityLevel into account 👀. So the security admin should use the securityLevel index in the vacmAccessTable to keep noAuthNoPriv separate from authPriv and/or authNoPriv access 💅.
7.3. Conformance
For an implementation of the View-based Access Control Model to be conformant, it MUST implement the SNMP-VIEW-BASED-ACM-MIB according to the vacmMIBCompliance 📋. It also SHOULD implement the initial configuration, described in appendix A 🌈.
7.4. Access to the SNMP-VIEW-BASED-ACM-MIB
The objects in this MIB control access to all the MIB data accessible through the SNMP engine, and in many environments they may be considered sensitive 🥺. It's super important to closely control (both read and write) access to these MIB objects, by using appropriately configured Access Control models (for example, the View-based Access Control Model specified in this document) 🔒.
8. References 📚
- [RFC2578] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
- [RFC2579] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
- [RFC2571] Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for describing SNMP Management Frameworks", RFC 2571, April 1999.
- [RFC2572] Case, J., Harrington, D., Presuhn, R. and B. Wijnen, "Message Processing and Dispatching for the Simple Network Management Protocol (SNMP)", RFC 2572, April 1999.
- [RFC2574] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", RFC 2574, April 1999.
- [ISO-ASN.1] Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Organization for Standardization. International Standard 8824, (December, 1987).
9. Editors' Addresses ✉️
Bert Wijnen
IBM T. J. Watson Research
Schagen 33
3461 GL Linschoten
Netherlands
Phone: +31-348-432-794
EMail: wijnen@vnet.ibm.com
Randy Presuhn
BMC Software, Inc
965 Stewart Drive
Sunnyvale, CA 94086
USA
Phone: +1-408-616-3100
EMail: randy_presuhn@bmc.com
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Phone: +1-408-526-5260
EMail: kzm@cisco.comAPPENDIX A - Installation 🎀
A.1. Installation Parameters
During installation, an authoritative SNMP engine that supports this View-based Access Control Model SHOULD be configured with a few initial parameters 🌟. For the View-based Access Control Model, these include:
1) A security configuration
The choice of security configuration decides whether initial configuration gets implemented, and if so, how 💫. You pick exactly one of three options:
- initial-minimum-security-configuration
- initial-semi-security-configuration
- initial-no-access-configuration
With an initial-no-access-configuration, there's no initial configuration at all, so the steps below don't apply 🙈.
2) A default context
One entry in the vacmContextTable with a contextName of "" (the empty string) represents the default context 🧸. Heads up: this table gets created automatically if a default context exists ✨.
vacmContextName ""3) An initial group
One entry in the vacmSecurityToGroupTable allows access to the group "initial" 🦋.
vacmSecurityModel 3 (USM)
vacmSecurityName "initial"
vacmGroupName "initial"
vacmSecurityToGroupStorageType anyValidStorageType
vacmSecurityToGroupStatus active4) Initial access rights 🔑
okay so there are three vacmAccessTable entries we need to set up, bestie 🧚
- read-notify access for securityModel USM, securityLevel "noAuthNoPriv" on behalf of securityNames that belong to the group "initial" to the
<restricted>MIB view in the default context with contextName "". - read-write-notify access for securityModel USM, securityLevel "authNoPriv" on behalf of securityNames that belong to the group "initial" to the
<internet>MIB view in the default context with contextName "". - if privacy is supported, read-write-notify access for securityModel USM, securityLevel "authPriv" on behalf of securityNames that belong to the group "initial" to the
<internet>MIB view in the default context with contextName "".
that translates into these entries in the vacmAccessTable 💅
One entry for unauthenticated access (noAuthNoPriv):
vacmGroupName "initial"
vacmAccessContextPrefix ""
vacmAccessSecurityModel 3 (USM)
vacmAccessSecurityLevel noAuthNoPriv
vacmAccessContextMatch exact
vacmAccessReadViewName "restricted"
vacmAccessWriteViewName ""
vacmAccessNotifyViewName "restricted"
vacmAccessStorageType anyValidStorageType
vacmAccessStatus activeOne entry for authenticated access (authNoPriv) with optional privacy (authPriv):
vacmGroupName "initial"
vacmAccessContextPrefix ""
vacmAccessSecurityModel 3 (USM)
vacmAccessSecurityLevel authNoPriv
vacmAccessContextMatch exact
vacmAccessReadViewName "internet"
vacmAccessWriteViewName "internet"
vacmAccessNotifyViewName "internet"
vacmAccessStorageType anyValidStorageType
vacmAccessStatus active5) Two MIB views 🌈, and the second one depends on your security configuration. the vibe shifts depending on which one you pick 🫶
- One view, the
<internet>view, for authenticated access:- the
<internet>MIB view is the following subtree:"internet" (subtree 1.3.6.1)
- the
- A second view, the
<restricted>view, for unauthenticated access. This view is configured according to the selected security configuration:- For the initial-no-access-configuration there is no default initial configuration, so no MIB views are pre-scribed. 🙈
- For the initial-semi-secure-configuration, the
<restricted>MIB view is the union of these subtrees: - For the initial-minimum-secure-configuration, the
<restricted>MIB view is the following subtree:"internet" (subtree 1.3.6.1)
this translates into the following "internet" entry in the vacmViewTreeFamilyTable 🦋
minimum-secure semi-secure
---------------- ---------------
vacmViewTreeFamilyViewName "internet" "internet"
vacmViewTreeFamilySubtree 1.3.6.1 1.3.6.1
vacmViewTreeFamilyMask "" ""
vacmViewTreeFamilyType 1 (included) 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType anyValidStorageType
vacmViewTreeFamilyStatus active activeand in addition, it translates into the following "restricted" entries in the vacmViewTreeFamilyTable 🎀
minimum-secure semi-secure
---------------- ---------------
vacmViewTreeFamilyViewName "restricted" "restricted"
vacmViewTreeFamilySubtree 1.3.6.1 1.3.6.1.2.1.1
vacmViewTreeFamilyMask "" ""
vacmViewTreeFamilyType 1 (included) 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType anyValidStorageType
vacmViewTreeFamilyStatus active active
vacmViewTreeFamilyViewName "restricted"
vacmViewTreeFamilySubtree 1.3.6.1.2.1.11
vacmViewTreeFamilyMask ""
vacmViewTreeFamilyType 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType
vacmViewTreeFamilyStatus active
vacmViewTreeFamilyViewName "restricted"
vacmViewTreeFamilySubtree 1.3.6.1.6.3.10.2.1
vacmViewTreeFamilyMask ""
vacmViewTreeFamilyType 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType
vacmViewTreeFamilyStatus active
vacmViewTreeFamilyViewName "restricted"
vacmViewTreeFamilySubtree 1.3.6.1.6.3.11.2.1
vacmViewTreeFamilyMask ""
vacmViewTreeFamilyType 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType
vacmViewTreeFamilyStatus active
vacmViewTreeFamilyViewName "restricted"
vacmViewTreeFamilySubtree 1.3.6.1.6.3.15.1.1
vacmViewTreeFamilyMask ""
vacmViewTreeFamilyType 1 (included)
vacmViewTreeFamilyStorageType anyValidStorageType
vacmViewTreeFamilyStatus activeB. Change Log 📝
okay the glow-up history 💖 these are the changes made since RFC2275:
- Added text to vacmSecurityToGroupStatus DESCRIPTION clause to clarify under which conditions an entry in the vacmSecurityToGroupTable can be made active.
- Added REVISION clauses to MODULE-IDENTITY.
- Clarified text in vacmAccessTable DESCRIPTION clause.
- Added a DEFVAL clause to vacmAccessContextMatch object.
- Added missing columns in Appendix A and re-arranged for clarity.
- Fixed oids in appendix A.
- Use the PDU Class terminology instead of RFC1905 PDU types.
- Added section 7.4 about access control to the MIB.
- Fixed references to new/revised documents.
- Fixed Editor contact information.
- Fixed spelling errors.
- Removed one vacmAccesEntry from sample in appendix A.
- Made some more clarifications.
- Updated acknowledgement section.
C. Full Copyright Statement ⭐
Copyright (C) The Internet Society (1999). All Rights Reserved.
so the deal with this document 🧾 you can copy it and share it with others, and you can make derivative works that comment on or explain it or help with implementing it. you can prepare, copy, publish and distribute those, in whole or in part, with no restrictions of any kind, as long as the above copyright notice and this paragraph are included on all such copies and derivative works. however, this document itself may not be modified in any way, like removing the copyright notice or references to the Internet Society or other Internet organizations. the exception is when it's needed for developing Internet standards, in which case the procedures for copyrights defined in the Internet Standards process must be followed, or when it's needed to translate it into languages other than English.
the limited permissions above are perpetual and will not be revoked by the Internet Society or its successors or assigns. forever and ever 💜
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Acknowledgement 🫶
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📦 where this page comes from
- ietf: rfc2575 1999-04
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms