RFC 2786
Diffie-Helman USM Key Management Information Base and Textual Convention
RFC 2786: Diffie-Helman USM Key Management Information Base and Textual Convention 🎀
okay bestie, let's talk about RFC 2786 🦋 It's an Experimental document from the Network Working Group, written by M. St. Johns at Excite@Home and dated March 2000. It doesn't list anything it obsoletes or updates, so it's a standalone main character 💅
Status of This Memo ✨
So this memo defines an Experimental Protocol for the Internet community 🧚 It is NOT an Internet standard of any kind, and the authors are literally begging for discussion and suggestions for improvement 🙈 Distribution is unlimited, so share it with everyone 💜
Copyright Notice 🌸
Copyright (C) The Internet Society (2000). All Rights Reserved.
IESG Note 💀
ngl this one is important 🫶 This document specifies an experimental MIB. If you read, implement, or use this MIB, know that the IETF might someday charter a Working Group to build a standards track MIB for the same problem space. That future MIB could be incompatible with this one, so don't get too attached 😭
Abstract 🔥
Okay so this memo adds an experimental chunk to the Management Information Base (MIB), the thing network management protocols use 🍓 It defines a textual convention for Diffie-Helman key agreement exchanges, plus a set of objects that extend the usmUserTable so you can use a DH key exchange in addition to the key change method described in [12]. In other words, this MIB brings forward secrecy to the USM model 👑 It also has objects you can use to kick start security on an SNMPv3 agent when the out of band path is authenticated but not necessarily private or confidential.
The KeyChange textual convention in [12] does make secure key changes, but it has a flaw. If a third party knows the original key (say the agent came from the factory with a standard default key) and can capture every SNMP exchange, that third party ends up knowing the new key too 😬 The Diffie-Helman key change in this memo limits knowledge of the new key to just the agent and the manager making the change ✨ In other words, this process adds forward secrecy to the key change process.
The recommendation in [12] is to populate the usmUserTable out of band, meaning not via SNMP 🎀 If you only have a few agents, you can do it through a console port by hand. If you have lots of agents, like in a cable modem system, the manual approach just doesn't scale 💅 Put the two mechanisms in this memo together, the DH key change mechanism and the DH key ignition mechanism, and you get manageable use of SNMPv3 USM across a system of millions of devices 🌈
This memo specifies a MIB module that is compliant with the SNMP SMIv2[5][6][7] 🦋 The objects fit the SNMP framework and existing SNMP standards, and they're meant to be used with the SNMPv3 User Security Model MIB and other security related MIBs.
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 [16] 📚
This memo is a private submission by the author, but it's relevant to the SNMPv3 working group within the Internet Engineering Task Force 🫶 Comments are welcome and should go to the author.
Table of Contents 💖
1 The SNMP Management Framework ................................. 2
1.1 Structure of the MIB ........................................ 3
2 Theory of Operation ........................................... 4
2.1 Diffie-Helman Key Changes ................................... 4
2.2 Diffie-Helman Key Ignition .................................. 4
3 Definitions ................................................... 6
4 References .................................................... 17
5 Security Considerations ....................................... 18
6 Intellectual Property ......................................... 19
7 Author's Address .............................................. 19
8 Full Copyright Statement ...................................... 201. The SNMP Management Framework ✨
The SNMP Management Framework is made up of five major components, and it's giving full architecture 🏗️
- An overall architecture, described in RFC 2271 [1].
- Mechanisms for describing and naming objects and events for the purpose of management. The first version of this Structure of Management Information (SMI) is called SMIv1 and is described in STD 16, RFC 1155 [2], STD 16, RFC 1212 [3] and RFC 1215 [4]. The second version, called SMIv2, is described in STD 58, RFC 2578 [5], STD 58, RFC 2579 [6] and STD 58, RFC 2580 [7].
- Message protocols for transferring management information. The first version of the SNMP message protocol is called SNMPv1 and is described in STD 15, RFC 1157 [8]. A second version, SNMPv2c, which is not an Internet standards track protocol, is described in RFC 1901 [9] and RFC 1906 [10]. The third version of the message protocol is called SNMPv3 and is described in RFC 1906 [10], RFC 2272 [11] and RFC 2274 [12].
- Protocol operations for accessing management information. The first set of protocol operations and associated PDU formats is described in STD 15, RFC 1157 [8]. A second set of protocol operations and associated PDU formats is described in RFC 1905 [13].
- A set of fundamental applications described in RFC 2273 [14], plus the view-based access control mechanism described in RFC 2275 [15].
Managed objects are accessed through a virtual information store called the Management Information Base, or MIB 🌷 Objects in the MIB are defined using the mechanisms in the SMI.
This memo specifies a MIB module that is compliant to the SMIv2 💅 A MIB conforming to SMIv1 can be produced through the appropriate translations. The translated MIB must be semantically equivalent, except where objects or events are left out because no translation is possible (use of Counter64). Some machine readable information in SMIv2 gets turned into textual descriptions in SMIv1 during translation. But losing that machine readable information is not considered to change the semantics of the MIB, so it's all good 🫶
1.1. Structure of the MIB 🧩
This MIB has three groups and a single textual convention:
- The
DHKeyChangetextual convention defines the process for changing a secret key value via a Diffie-Helman key exchange. - The
usmDHPublicObjectsgroup contains a single object that describes the public Diffie-Helman parameters required by any instance of aDHKeyChangetyped object. - The
usmDHUserKeyTableaugments and extends theusmUserTabledefined in the SNMPv3 User-based Security Model MIB [12]. It provides objects that let you update the Authentication and Privacy keys for a row in this table through a Diffie-Helman key exchange. - The
usmDHKickstartTablegives a management station a way to agree on a set of authentication and confidentiality keys, and their associated row in theusmUserTable🔑
2. Theory of Operation 🔮
2.1. Diffie-Helman Key Changes 🦋
Okay so here's the flow. When a row is created in the usmUserTable, or when an object changes (either one in the usmDHUserKeyTable or its associated value in the usmUserTable), the agent generates a random number. From that random number, the agent uses the DH parameters and transforms to derive a DH public value, and that value gets published to the associated MIB object 🌸 The management station reads one or more of the objects in the usmDHUserKeyTable to get the agent's DH public values.
Next, the management station generates its own random number and derives a DH public value from it (as described in the DHKeyChange Textual Convention). Then it does an SNMP SET against the object in the usmDHUserKeyTable ✨ The set is the concatenation of the agent's derived DH public value and the manager's derived DH public value. Including the agent's value makes sure the DHKeyChange object hasn't changed in the meantime 👀
When the set completes successfully, the underlying key (authentication or confidentiality) for the associated object in the usmUserTable changes to a key derived from the DH shared secret 🔥 Both the agent and the management station can calculate this value, since each knows its own random number and the other's DH public number. That's the magic of Diffie-Helman, periodt 💅
2.2. Diffie-Helman Key Ignition 🔥
okay so [12] says the usmUserTable should be filled in out of band, like, manually 📝 ngl that works fine if you only have a few agents, or they all share the same key material, and you can physically get to the device. but it does NOT scale 😭 we're talking millions of devices spread across thousands of locations, hundreds of markets, and multiple countries. so yeah, it's not it for a cable modem system, and it may not go super well with other big consumer broadband IP stuff either 🌈
the good news 🎀 the methods in the objects under usmDHKickstartGroup can fill in the usmUserTable when you can get at least limited integrity for the provisioning process, but you can't guarantee confidentiality. and here's the bestie part ✨ because of the DH exchange, every agent ends up with operational USM keys that are different from every other device in the system. so if one device gets compromised, the whole system doesn't go down with it 🫶
the vendor who builds these objects is expected to provide one or more usmSecurityNames that map to a set of accesses defined in the VACM [15] tables. for example, the vendor might give you a 'root' user who has read-write access to the entire device, an 'operator' user who can see the network specific monitoring objects and can also reset the device, and a 'customer' user who gets a subset of the monitoring objects. that last one helps the customer debug the device when they're dealing with customer service questions 💁♀️
how the setup works 🦋 the system manager (the org or person who owns the group of devices) generates one or more random numbers, called R. the manager then derives the DH Public Numbers R' from those random numbers, pairs each public number with a security name, and configures the agent with that pairing. the configuration happens either manually (if there are only a few devices) or through some kind of distributed configuration file. the actual mechanism is outside the scope of this document, so that's a whole other story 📚
then the agent makes its own random number for each name/number pair, and publishes the DH Public Number it derived from that random number in the usmDHKickstartTable. it publishes this alongside the manager's public number and the security name it was given 🧚
once the agent is initialized, an SNMP Manager can read the usmDHKickstartTable using the security name 'dhKickstart' with no authentication. the manager looks for one or more entries in this table where it knows the random number that was used to derive the usmDHKickstartMgrPublic number. with its private random number and the usmDHKickstartMyPublic number, the manager can calculate the DH shared secret. from that shared secret, it derives the operational authentication and confidentiality keys for the usmUserTable row that has the matching security name. with those keys and the security name, the manager can use normal USM mechanisms to get into the rest of the agent's MIB space 💜
3. Definitions ✨
okay here comes the MIB itself 💅
SNMP-USM-DH-OBJECTS-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE,
-- OBJECT-IDENTITY,
experimental, Integer32
FROM SNMPv2-SMI
TEXTUAL-CONVENTION
FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP
FROM SNMPv2-CONF
usmUserEntry
FROM SNMP-USER-BASED-SM-MIB
SnmpAdminString
FROM SNMP-FRAMEWORK-MIB;
snmpUsmDHObjectsMIB MODULE-IDENTITY
LAST-UPDATED "200003060000Z" -- 6 March 2000, Midnight
ORGANIZATION "Excite@Home"
CONTACT-INFO "Author: Mike StJohns
Postal: Excite@Home
450 Broadway
Redwood City, CA 94063
Email: stjohns@corp.home.net
Phone: +1-650-556-5368"
DESCRIPTION
"The management information definitions for providing forward
secrecy for key changes for the usmUserTable, and for providing a
method for 'kickstarting' access to the agent via a Diffie-Helman
key agreement."
REVISION "200003060000Z"
DESCRIPTION
"Initial version published as RFC 2786."
::= { experimental 101 } -- IANA DHKEY-CHANGE 101
-- Administrative assignments
usmDHKeyObjects OBJECT IDENTIFIER ::= { snmpUsmDHObjectsMIB 1 }
usmDHKeyConformance OBJECT IDENTIFIER ::= { snmpUsmDHObjectsMIB 2 }
-- Textual conventions
DHKeyChange ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Upon initialization, or upon creation of a row containing an
object of this type, and after any successful SET of this value, a
GET of this value returns 'y' where y = g^xa MOD p, and where g is
the base from usmDHParameters, p is the prime from
usmDHParameters, and xa is a new random integer selected by the
agent in the interval 2^(l-1) <= xa < 2^l < p-1. 'l' is the
optional privateValueLength from usmDHParameters in bits. If 'l'
is omitted, then xa (and xr below) is selected in the interval 0
<= xa < p-1. y is expressed as an OCTET STRING 'PV' of length 'k'
which satisfies
k
y = SUM 2^(8(k-i)) PV'i
i=1
where PV1,...,PVk are the octets of PV from first to last, and
where PV1 <> 0.
A successful SET consists of the value 'y' expressed as an OCTET
STRING as above concatenated with the value 'z'(expressed as an
OCTET STRING in the same manner as y) where z = g^xr MOD p, where
g, p and l are as above, and where xr is a new random integer
selected by the manager in the interval 2^(l-1) <= xr < 2^l <
p-1. A SET to an object of this type will fail with the error
wrongValue if the current 'y' does not match the 'y' portion of
the value of the varbind for the object. (E.g. GET yout, SET
concat(yin, z), yout <> yin).
Note that the private values xa and xr are never transmitted from
manager to device or vice versa, only the values y and z.
Obviously, these values must be retained until a successful SET on
the associated object.
The shared secret 'sk' is calculated at the agent as sk = z^xa MOD
p, and at the manager as sk = y^xr MOD p.
Each object definition of this type MUST describe how to map from
the shared secret 'sk' to the operational key value used by the
protocols and operations related to the object. In general, if n
bits of key are required, the author suggests using the n
right-most bits of the shared secret as the operational key value."
REFERENCE
"-- Diffie-Hellman Key-Agreement Standard, PKCS #3;
RSA Laboratories, November 1993"
SYNTAX OCTET STRING
-- Diffie Hellman public values
usmDHPublicObjects OBJECT IDENTIFIER ::= { usmDHKeyObjects 1 }
usmDHParameters OBJECT-TYPE
SYNTAX OCTET STRING
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The public Diffie-Hellman parameters for doing a Diffie-Hellman
key agreement for this device. This is encoded as an ASN.1
DHParameter per PKCS #3, section 9. E.g.
DHParameter ::= SEQUENCE {
prime INTEGER, -- p
base INTEGER, -- g
privateValueLength INTEGER OPTIONAL }
Implementors are encouraged to use either the values from
Oakley Group 1 or the values of from Oakley Group 2 as specified
in RFC-2409, The Internet Key Exchange, Section 6.1, 6.2 as the
default for this object. Other values may be used, but the
security properties of those values MUST be well understood and
MUST meet the requirements of PKCS #3 for the selection of
Diffie-Hellman primes.
In addition, any time usmDHParameters changes, all values of
type DHKeyChange will change and new random numbers MUST be
generated by the agent for each DHKeyChange object."
REFERENCE
"-- Diffie-Hellman Key-Agreement Standard, PKCS #3,
RSA Laboratories, November 1993
-- The Internet Key Exchange, RFC 2409, November 1998,
Sec 6.1, 6.2"
::= { usmDHPublicObjects 1 }
usmDHUserKeyTable OBJECT-TYPE
SYNTAX SEQUENCE OF UsmDHUserKeyEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table augments and extends the usmUserTable and provides
4 objects which exactly mirror the objects in that table with the
textual convention of 'KeyChange'. This extension allows key
changes to be done in a manner where the knowledge of the current
secret plus knowledge of the key change data exchanges (e.g. via
wiretapping) will not reveal the new key."
::= { usmDHPublicObjects 2 }
usmDHUserKeyEntry OBJECT-TYPE
SYNTAX UsmDHUserKeyEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A row of DHKeyChange objects which augment or replace the
functionality of the KeyChange objects in the base table row."
AUGMENTS { usmUserEntry }
::= {usmDHUserKeyTable 1 }
UsmDHUserKeyEntry ::= SEQUENCE {
usmDHUserAuthKeyChange DHKeyChange,
usmDHUserOwnAuthKeyChange DHKeyChange,
usmDHUserPrivKeyChange DHKeyChange,
usmDHUserOwnPrivKeyChange DHKeyChange
}
usmDHUserAuthKeyChange OBJECT-TYPE
SYNTAX DHKeyChange
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The object used to change any given user's Authentication Key
using a Diffie-Hellman key exchange.
The right-most n bits of the shared secret 'sk', where 'n' is the
number of bits required for the protocol defined by
usmUserAuthProtocol, are installed as the operational
authentication key for this row after a successful SET."
::= { usmDHUserKeyEntry 1 }
usmDHUserOwnAuthKeyChange OBJECT-TYPE
SYNTAX DHKeyChange
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The object used to change the agents own Authentication Key
using a Diffie-Hellman key exchange.
The right-most n bits of the shared secret 'sk', where 'n' is the
number of bits required for the protocol defined by
usmUserAuthProtocol, are installed as the operational
authentication key for this row after a successful SET."
::= { usmDHUserKeyEntry 2 }
usmDHUserPrivKeyChange OBJECT-TYPE
SYNTAX DHKeyChange
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The object used to change any given user's Privacy Key using
a Diffie-Hellman key exchange.
The right-most n bits of the shared secret 'sk', where 'n' is the
number of bits required for the protocol defined by
usmUserPrivProtocol, are installed as the operational privacy key
for this row after a successful SET."
::= { usmDHUserKeyEntry 3 }
usmDHUserOwnPrivKeyChange OBJECT-TYPE
SYNTAX DHKeyChange
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The object used to change the agent's own Privacy Key using a
Diffie-Hellman key exchange.
The right-most n bits of the shared secret 'sk', where 'n' is the
number of bits required for the protocol defined by
usmUserPrivProtocol, are installed as the operational privacy key
for this row after a successful SET."
::= { usmDHUserKeyEntry 4 }
usmDHKickstartGroup OBJECT IDENTIFIER ::= { usmDHKeyObjects 2 }Okay bestie, the kickstart table is giving "secret setup menu" energy ✨🧚 It's a list of little mappings between Diffie-Hellman key agreement values and rows in the usmUserTable, and the rows show up when the device gets handed a public value plus a name pair at startup 🎀
usmDHKickstartTable OBJECT-TYPE
SYNTAX SEQUENCE OF UsmDHKickstartEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table of mappings between zero or more Diffie-Helman key
agreement values and entries in the usmUserTable. Entries in this
table are created by providing the associated device with a
Diffie-Helman public value and a usmUserName/usmUserSecurityName
pair during initialization. How these values are provided is
outside the scope of this MIB, but could be provided manually, or
through a configuration file. Valid public value/name pairs
result in the creation of a row in this table as well as the
creation of an associated row (with keys derived as indicated) in
the usmUserTable. The actual access the related usmSecurityName
has is dependent on the entries in the VACM tables. In general,
an implementor will specify one or more standard security names
and will provide entries in the VACM tables granting various
levels of access to those names. The actual content of the VACM
table is beyond the scope of this MIB.
Note: This table is expected to be readable without authentication
using the usmUserSecurityName 'dhKickstart'. See the conformance
statements for details."
::= { usmDHKickstartGroup 1 }
usmDHKickstartEntry OBJECT-TYPE
SYNTAX UsmDHKickstartEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry in the usmDHKickstartTable. The agent SHOULD either
delete this entry or mark it as inactive upon a successful SET of
any of the KeyChange-typed objects in the usmUserEntry or upon a
successful SET of any of the DHKeyChange-typed objects in the
usmDhKeyChangeEntry where the related usmSecurityName (e.g. row of
usmUserTable or row of ushDhKeyChangeTable) equals this entry's
usmDhKickstartSecurityName. In otherwords, once you've changed
one or more of the keys for a row in usmUserTable with a
particular security name, the row in this table with that same
security name is no longer useful or meaningful."
INDEX { usmDHKickstartIndex }
::= {usmDHKickstartTable 1 }
UsmDHKickstartEntry ::= SEQUENCE {
usmDHKickstartIndex Integer32,
usmDHKickstartMyPublic OCTET STRING,
usmDHKickstartMgrPublic OCTET STRING,
usmDHKickstartSecurityName SnmpAdminString
}
usmDHKickstartIndex OBJECT-TYPE
SYNTAX Integer32 (1..2147483647)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Index value for this row."
::= { usmDHKickstartEntry 1 }
usmDHKickstartMyPublic OBJECT-TYPE
SYNTAX OCTET STRING
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The agent's Diffie-Hellman public value for this row. At
initialization, the agent generates a random number and derives
its public value from that number. This public value is published
here. This public value 'y' equals g^r MOD p where g is the from
the set of Diffie-Hellman parameters, p is the prime from those
parameters, and r is a random integer selected by the agent in the
interval 2^(l-1) <= r < p-1 < 2^l. If l is unspecified, then r is
a random integer selected in the interval 0 <= r < p-1
The public value is expressed as an OCTET STRING 'PV' of length
'k' which satisfies
k
y = SUM 2^(8(k-i)) PV'i
i = 1
where PV1,...,PVk are the octets of PV from first to last, and
where PV1 != 0.
The following DH parameters (Oakley group #2, RFC 2409, sec 6.1,
6.2) are used for this object:
g = 2
p = FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
FFFFFFFF FFFFFFFF
l=1024
"
REFERENCE
"-- Diffie-Hellman Key-Agreement Standard, PKCS#3v1.4;
RSA Laboratories, November 1993
-- The Internet Key Exchange, RFC2409;
Harkins, D., Carrel, D.; November 1998"
::= { usmDHKickstartEntry 2 }
usmDHKickstartMgrPublic OBJECT-TYPE
SYNTAX OCTET STRING
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The manager's Diffie-Hellman public value for this row. Note
that this value is not set via the SNMP agent, but may be set via
some out of band method, such as the device's configuration file.
The manager calculates this value in the same manner and using the
same parameter set as the agent does. E.g. it selects a random
number 'r', calculates y = g^r mod p and provides 'y' as the
public number expressed as an OCTET STRING. See
usmDHKickstartMyPublic for details.
When this object is set with a valid value during initialization,
a row is created in the usmUserTable with the following values:
usmUserEngineID localEngineID
usmUserName [value of usmDHKickstartSecurityName]
usmUserSecurityName [value of usmDHKickstartSecurityName]
usmUserCloneFrom ZeroDotZero
usmUserAuthProtocol usmHMACMD5AuthProtocol
usmUserAuthKeyChange -- derived from set value
usmUserOwnAuthKeyChange -- derived from set value
usmUserPrivProtocol usmDESPrivProtocol
usmUserPrivKeyChange -- derived from set value
usmUserOwnPrivKeyChange -- derived from set value
usmUserPublic ''
usmUserStorageType permanent
usmUserStatus active
A shared secret 'sk' is calculated at the agent as sk =
mgrPublic^r mod p where r is the agents random number and p is the
DH prime from the common parameters. The underlying privacy key
for this row is derived from sk by applying the key derivation
function PBKDF2 defined in PKCS#5v2.0 with a salt of 0xd1310ba6,
and iterationCount of 500, a keyLength of 16 (for
usmDESPrivProtocol), and a prf (pseudo random function) of
'id-hmacWithSHA1'. The underlying authentication key for this row
is derived from sk by applying the key derivation function PBKDF2
with a salt of 0x98dfb5ac , an interation count of 500, a
keyLength of 16 (for usmHMAC5AuthProtocol), and a prf of
'id-hmacWithSHA1'. Note: The salts are the first two words in the
ks0 [key schedule 0] of the BLOWFISH cipher from 'Applied
Cryptography' by Bruce Schnier - they could be any relatively
random string of bits.
The manager can use its knowledge of its own random number and the
agent's public value to kickstart its access to the agent in a
secure manner. Note that the security of this approach is
directly related to the strength of the authorization security of
the out of band provisioning of the managers public value
(e.g. the configuration file), but is not dependent at all on the
strength of the confidentiality of the out of band provisioning
data."
REFERENCE
"-- Password-Based Cryptography Standard, PKCS#5v2.0;
RSA Laboratories, March 1999
-- Applied Cryptography, 2nd Ed.; B. Schneier,
Counterpane Systems; John Wiley & Sons, 1996"
::= { usmDHKickstartEntry 3 }
usmDHKickstartSecurityName OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The usmUserName and usmUserSecurityName in the usmUserTable
associated with this row. This is provided in the same manner and
at the same time as the usmDHKickstartMgrPublic value -
e.g. possibly manually, or via the device's configuration file."
::= { usmDHKickstartEntry 4 }
> Heads up: the security reasoning for the manager's public value lives in the code block above, so read that DESCRIPTION closely 💀🔥
-- Conformance Information
usmDHKeyMIBCompliances OBJECT IDENTIFIER ::= { usmDHKeyConformance 1 }
usmDHKeyMIBGroups OBJECT IDENTIFIER ::= { usmDHKeyConformance 2 }
-- Compliance statements
usmDHKeyMIBCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for this module."
MODULE
GROUP usmDHKeyMIBBasicGroup
DESCRIPTION
"This group MAY be implemented by any agent which
implements the usmUserTable and which wishes to provide the
ability to change user and agent authentication and privacy
keys via Diffie-Hellman key exchanges."
GROUP usmDHKeyParamGroup
DESCRIPTION
"This group MUST be implemented by any agent which
implements a MIB containing the DHKeyChange Textual
Convention defined in this module."
GROUP usmDHKeyKickstartGroup
DESCRIPTION
"This group MAY be implemented by any agent which
implements the usmUserTable and which wishes the ability to
populate the USM table based on out-of-band provided DH
ignition values.
Any agent implementing this group is expected to provide
preinstalled entries in the vacm tables as follows:
In the usmUserTable: This entry allows access to the
system and dhKickstart groups
usmUserEngineID localEngineID
usmUserName 'dhKickstart'
usmUserSecurityName 'dhKickstart'
usmUserCloneFrom ZeroDotZero
usmUserAuthProtocol none
usmUserAuthKeyChange ''
usmUserOwnAuthKeyChange ''
usmUserPrivProtocol none
usmUserPrivKeyChange ''
usmUserOwnPrivKeyChange ''
usmUserPublic ''
usmUserStorageType permanent
usmUserStatus active
In the vacmSecurityToGroupTable: This maps the initial
user into the accessible objects.
vacmSecurityModel 3 (USM)
vacmSecurityName 'dhKickstart'
vacmGroupName 'dhKickstart'
vacmSecurityToGroupStorageType permanent
vacmSecurityToGroupStatus active
In the vacmAccessTable: Group name to view name translation.
vacmGroupName 'dhKickstart'
vacmAccessContextPrefix ''
vacmAccessSecurityModel 3 (USM)
vacmAccessSecurityLevel noAuthNoPriv
vacmAccessContextMatch exact
vacmAccessReadViewName 'dhKickRestricted'
vacmAccessWriteViewName ''
vacmAccessNotifyViewName 'dhKickRestricted'
vacmAccessStorageType permanent
vacmAccessStatus active
In the vacmViewTreeFamilyTable: Two entries to allow the
initial entry to access the system and kickstart groups.
vacmViewTreeFamilyViewName 'dhKickRestricted'
vacmViewTreeFamilySubtree 1.3.6.1.2.1.1 (system)
vacmViewTreeFamilyMask ''
vacmViewTreeFamilyType 1
vacmViewTreeFamilyStorageType permanent
vacmViewTreeFamilyStatus active
vacmViewTreeFamilyViewName 'dhKickRestricted'
vacmViewTreeFamilySubtree (usmDHKickstartTable OID)
vacmViewTreeFamilyMask ''
vacmViewTreeFamilyType 1
vacmViewTreeFamilyStorageType permanent
vacmViewTreeFamilyStatus active
"
OBJECT usmDHParameters
MIN-ACCESS read-only
DESCRIPTION
"It is compliant to implement this object as read-only for
any device."
::= { usmDHKeyMIBCompliances 1 }
-- Units of Compliance
usmDHKeyMIBBasicGroup OBJECT-GROUP OBJECTS { usmDHUserAuthKeyChange, usmDHUserOwnAuthKeyChange, usmDHUserPrivKeyChange, usmDHUserOwnPrivKeyChange } STATUS current DESCRIPTION "" ::= { usmDHKeyMIBGroups 1 }
usmDHKeyParamGroup OBJECT-GROUP OBJECTS { usmDHParameters } STATUS current DESCRIPTION "The mandatory object for all MIBs which use the DHKeyChange textual convention." ::= { usmDHKeyMIBGroups 2 }
usmDHKeyKickstartGroup OBJECT-GROUP OBJECTS { usmDHKickstartMyPublic, usmDHKickstartMgrPublic, usmDHKickstartSecurityName } STATUS current DESCRIPTION "The objects used for kickstarting one or more SNMPv3 USM associations via a configuration file or other out of band, non-confidential access." ::= { usmDHKeyMIBGroups 3 }
END
# 4. References 📚✨
- [1] Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for Describing SNMP Management Frameworks", RFC 2571, April 1999.
- [2] Rose, M. and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based Internets", STD 16, RFC 1155, May 1990.
- [3] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16, RFC 1212, March 1991.
- [4] Rose, M., "A Convention for Defining Traps for use with the SNMP", RFC 1215, March 1991.
- [5] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
- [6] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
- [7] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999.
- [8] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "Simple Network Management Protocol", STD 15, RFC 1157, May 1990.
- [9] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901, January 1996.
- [10] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Transport Mappings for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1906, January 1996.
- [11] Case, J., Harrington D., Presuhn R. and B. Wijnen, "Message Processing and Dispatching for the Simple Network Management Protocol (SNMP)", RFC 2572, April 1999.
- [12] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", RFC 2574, April 1999.
- [13] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Protocol Operations for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
- [14] Levi, D., Meyer, P. and B. Stewart, "SNMPv3 Applications", RFC 2573, April 1999.
- [15] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)", RFC 2575, April 1999.
- [16] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
- [17] "Diffie-Hellman Key-Agreement Standard, Version 1.4", PKCS #3, RSA Laboratories, November 1993.
- [18] Harkins, D. and D. Carrel, "The Internet Key Exchange", RFC 2409, November 1988.
- [19] Eastlake, D., Crocker, S. and J. Schiller, "Randomness Recommendations for Security", RFC 1750, December 1994.
---
# 5. Security Considerations 🔐💀
<red>okay bestie, this part is SERIOUS</red> 😭 Objects in the usmDHUserKeyTable should be considered to have the same security sensitivity as the objects of the KeyChange type in usmUserTable, and they should get the same level of protection. Specifically, the VACM should not grant more or less access to these objects than it grants to the usmUserTable KeyChange object. 🔒
The improper selection of parameters for use with Diffie-Hellman key changes may adversely affect the security of the agent. ⚠️ Please see the body of the MIB for specific recommendations or requirements on the selection of the DH parameters. 🦋
An unauthenticated DH exchange is subject to "man-in-the-middle" attacks. 👀 The use of the DH exchange in any specific environment should balance risk versus threat. ⚖️
Good security from a DH exchange requires a good source of random numbers. 🎲 If your application cannot provide a reasonable source of randomness, do not use a DH exchange. 🚫 For more information, see "Randomness Recommendations for Security" [19]. 💜
# 6. Intellectual Property 🧠
The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document, or the extent to which any license under such rights might or might not be available. It also doesn't say it has made any effort to identify any such rights. ✨ Information on the IETF's procedures for rights in standards-track and standards-related documentation can be found in BCP-11. 📜 Copies of claims of rights made available for publication, and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification, can be obtained from the IETF Secretariat. 🗂️
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. 📮 Please address that information to the IETF Executive Director. 💌
# 7. Author's Address 🖋️
Michael C. StJohns Excite@Home 450 Broadway Redwood City, CA 94063 USA
Phone: +1-650-556-5368 EMail: stjohns@corp.home.net
# 9. Full Copyright Statement ©️
<lavender>Copyright (C) The Internet Society (2000). All Rights Reserved.</lavender> 💜
This document and translations of it may be copied and furnished to others. 📄 Derivative works that comment on or otherwise explain it, or that assist in its implementation, may be prepared, copied, published and distributed, in whole or in part, without restriction 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, such as by removing the copyright notice or references to the Internet Society or other Internet organizations. The only exceptions are as needed for developing Internet standards, in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. 🌍
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. ♾️
This document and the information contained herein is provided on an "AS IS" basis, and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 🙈
# Acknowledgement 🫶
Funding for the RFC Editor function is currently provided by the Internet Society. 💖
📦 where this page comes from
- ietf: rfc2786 2000-03
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms