[MS-GKDI]:
Group Key Distribution Protocol
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Revision Summary
Date / Revision History / Revision Class / Comments6/17/2011 / 0.1 / New / Received document draft from product team.
12/16/2011 / 0.1 / None / No changes to the meaning, language, or formatting of the technical content.
3/30/2012 / 2.0 / Major / Significantly changed the technical content.
7/12/2012 / 3.0 / Major / Significantly changed the technical content.
10/25/2012 / 3.0 / None / No changes to the meaning, language, or formatting of the technical content.
1/31/2013 / 3.1 / Minor / Clarified the meaning of the technical content.
8/8/2013 / 3.2 / Major / Significantly changed the technical content.
11/14/2013 / 3.2 / None / No changes to the meaning, language, or formatting of the technical content.
2/13/2014 / 3.2 / None / No changes to the meaning, language, or formatting of the technical content.
5/15/2014 / 3.2 / None / No changes to the meaning, language, or formatting of the technical content.
6/30/2015 / 4.0 / Major / Significantly changed the technical content.
10/16/2015 / 4.0 / None / No changes to the meaning, language, or formatting of the technical content.
7/14/2016 / 4.0 / None / No changes to the meaning, language, or formatting of the technical content.
6/1/2017 / 4.0 / None / No changes to the meaning, language, or formatting of the technical content.
9/15/2017 / 5.0 / Major / Significantly changed the technical content.
Table of Contents
1Introduction
1.1Glossary
1.2References
1.2.1Normative References
1.2.2Informative References
1.3Overview
1.4Relationship to Other Protocols
1.5Prerequisites/Preconditions
1.6Applicability Statement
1.7Versioning and Capability Negotiation
1.8Vendor Extensible Fields
1.9Standards Assignments
2Messages
2.1Transport
2.2Common Data Types
2.2.1KDF Parameters
2.2.2FFC DH Parameters
2.2.3Public Key Formats
2.2.3.1FFC DH Key
2.2.3.2ECDH Key
2.2.4Group Key Envelope
2.3Directory Service Schema Elements
3Protocol Details
3.1ISDKey Server Details
3.1.1Abstract Data Model
3.1.2Timers
3.1.3Initialization
3.1.4Message Processing Events and Sequencing Rules
3.1.4.1GetKey (Opnum 0)
3.1.4.1.1Creating a New Root Key
3.1.4.1.2Generating a Group Key
3.1.4.1.3Creating or Updating a Server Configuration Object
3.1.5Timer Events
3.1.6Other Local Events
3.2ISDKey Client Details
3.2.1Abstract Data Model
3.2.2Timers
3.2.3Initialization
3.2.4Message Processing Events and Sequencing Rules
3.2.4.1Client Side Processing
3.2.4.2Retrieving a Group Key from a Server
3.2.4.3Computing the Desired Group Key
3.2.5Timer Events
3.2.6Other Local Events
4Protocol Examples
5Security
5.1Security Considerations for Implementers
5.2Index of Security Parameters
6Appendix A: Full IDL
7Appendix B: Product Behavior
8Change Tracking
9Index
1Introduction
The Group Key Distribution Protocol is used by clients to obtain cryptographic keys that correspond to arbitrary security descriptors that can be evaluated by an Active Directorydomain controller (DC). These keys can then be used by the client for various purposes, including encrypting data such that it can only be decrypted by a desired set of security principals.
Familiarity with cryptography concepts such as asymmetric and symmetric cryptography is required for a complete understanding of this specification. For more information about cryptography concepts, see [CRYPTO].
Sections 1.5, 1.8, 1.9, 2, and 3 of this specification are normative. All other sections and examples in this specification are informative.
1.1Glossary
This document uses the following terms:
access control entry (ACE): An entry in an access control list (ACL) that contains a set of user rights and a security identifier (SID) that identifies a principal for whom the rights are allowed, denied, or audited.
Active Directory: A general-purpose network directory service. Active Directory also refers to the Windows implementation of a directory service. Active Directory stores information about a variety of objects in the network. User accounts, computer accounts, groups, and all related credential information used by the Windows implementation of Kerberos are stored in Active Directory. Active Directory is either deployed as Active Directory Domain Services (AD DS) or Active Directory Lightweight Directory Services (AD LDS). [MS-ADTS] describes both forms. For more information, see [MS-AUTHSOD] section 1.1.1.5.2, Lightweight Directory Access Protocol (LDAP) versions 2 and 3, Kerberos, and DNS.
authentication level: A numeric value indicating the level of authentication or message protection that remote procedure call (RPC) will apply to a specific message exchange. For more information, see [C706] section 13.1.2.1 and [MS-RPCE].
big-endian: Multiple-byte values that are byte-ordered with the most significant byte stored in the memory location with the lowest address.
binary large object (BLOB): A collection of binary data stored as a single entity in a database.
common name (CN): A string attribute of a certificate that is one component of a distinguished name (DN). In Microsoft Enterprise uses, a CN must be unique within the forest where it is defined and any forests that share trust with the defining forest. The website or email address of the certificate owner is often used as a common name. Client applications often refer to a certification authority (CA) by the CN of its signing certificate.
container: An object in the directory that can serve as the parent for other objects. In the absence of schema constraints, all objects would be containers. The schema allows only objects of specific classes to be containers.
distinguished name (DN): A name that uniquely identifies an object by using the relative distinguished name (RDN) for the object, and the names of container objects and domains that contain the object. The distinguished name (DN) identifies the object and its location in a tree.
domain: A set of users and computers sharing a common namespace and management infrastructure. At least one computer member of the set must act as a domain controller (DC) and host a member list that identifies all members of the domain, as well as optionally hosting the Active Directory service. The domain controller provides authentication of members, creating a unit of trust for its members. Each domain has an identifier that is shared among its members. For more information, see [MS-AUTHSOD] section 1.1.1.5 and [MS-ADTS].
domain controller (DC): The service, running on a server, that implements Active Directory, or the server hosting this service. The service hosts the data store for objects and interoperates with other DCs to ensure that a local change to an object replicates correctly across all DCs. When Active Directory is operating as Active Directory Domain Services (AD DS), the DC contains full NC replicas of the configuration naming context (config NC), schema naming context (schema NC), and one of the domain NCs in its forest. If the AD DS DC is a global catalog server (GC server), it contains partial NC replicas of the remaining domain NCs in its forest. For more information, see [MS-AUTHSOD] section 1.1.1.5.2 and [MS-ADTS]. When Active Directory is operating as Active Directory Lightweight Directory Services (AD LDS), several AD LDS DCs can run on one server. When Active Directory is operating as AD DS, only one AD DS DC can run on one server. However, several AD LDS DCs can coexist with one AD DS DC on one server. The AD LDS DC contains full NC replicas of the config NC and the schema NC in its forest. The domain controller is the server side of Authentication Protocol Domain Support [MS-APDS].
Domain Name System (DNS): A hierarchical, distributed database that contains mappings of domain names to various types of data, such as IP addresses. DNS enables the location of computers and services by user-friendly names, and it also enables the discovery of other information stored in the database.
dynamic endpoint: A network-specific server address that is requested and assigned at run time. For more information, see [C706].
forest: In the Active Directory directory service, a forest is a set of naming contexts (NCs) consisting of one schema NC, one config NC, and one or more domain NCs. Because a set of NCs can be arranged into a tree structure, a forest is also a set of one or several trees of NCs.
globally unique identifier (GUID): A term used interchangeably with universally unique identifier (UUID) in Microsoft protocol technical documents (TDs). Interchanging the usage of these terms does not imply or require a specific algorithm or mechanism to generate the value. Specifically, the use of this term does not imply or require that the algorithms described in [RFC4122] or [C706] must be used for generating the GUID. See also universally unique identifier (UUID).
group key: A group seed key or group public key associated with a specified security descriptor in an Active Directory forest.
group key identifier: A triple that identifies the time period for which a group key was intended. A fully-specified group key identifier needs all three elements of the triple set to non-negative integer values. All group key identifiers returned by the server of this protocol are fully specified. One or more elements of the triple can be set to -1 in a client request to signify that any value of those elements is acceptable to the client. Within an Active Directory forest, a group key is identified uniquely by the combination of its associated security descriptor, its root key identifier, and its group key identifier.
group private key: A private key associated with a specified security descriptor in an Active Directory forest. It corresponds to the group public key for the same security descriptor and is derived from the group seed key for that security descriptor through a deterministic algorithm.
group public key: A public key associated with a specified security descriptor in an Active Directory forest. It corresponds to the group private key for the same security descriptor and is derived from the group seed key for that security descriptor through a deterministic algorithm.
Interface Definition Language (IDL): The International Standards Organization (ISO) standard language for specifying the interface for remote procedure calls. For more information, see [C706] section 4.
key derivation: The act of deriving a cryptographic key from another value (for example, the derivation of a cryptographic key from a password).
little-endian: Multiple-byte values that are byte-ordered with the least significant byte stored in the memory location with the lowest address.
Network Data Representation (NDR): A specification that defines a mapping from Interface Definition Language (IDL) data types onto octet streams. NDR also refers to the runtime environment that implements the mapping facilities (for example, data provided to NDR). For more information, see [MS-RPCE] and [C706] section 14.
object: A set of attributes, each with its associated values. For more information on objects, see [MS-ADTS] section 1 or [MS-DRSR] section 1.
private key: One of a pair of keys used in public-key cryptography. The private key is kept secret and is used to decrypt data that has been encrypted with the corresponding public key. For an introduction to this concept, see [CRYPTO] section 1.8 and [IEEE1363] section 3.1.
public key: One of a pair of keys used in public-key cryptography. The public key is distributed freely and published as part of a digital certificate. For an introduction to this concept, see [CRYPTO] section 1.8 and [IEEE1363] section 3.1.
read-only domain controller (RODC): A domain controller (DC) that does not accept originating updates. Additionally, an RODC does not perform outbound replication. An RODC cannot be the primary domain controller (PDC) for its domain.
relative distinguished name (RDN): An attribute-value pair used in the distinguished name of an object. For more information, see [RFC2251].
remote procedure call (RPC): A context-dependent term commonly overloaded with three meanings. Note that much of the industry literature concerning RPC technologies uses this term interchangeably for any of the three meanings. Following are the three definitions: (*) The runtime environment providing remote procedure call facilities. The preferred usage for this meaning is "RPC runtime". (*) The pattern of request and response message exchange between two parties (typically, a client and a server). The preferred usage for this meaning is "RPC exchange". (*) A single message from an exchange as defined in the previous definition. The preferred usage for this term is "RPC message". For more information about RPC, see [C706].
replication: The process of propagating the effects of all originating writes to any replica of a naming context (NC), to all replicas of the NC. If originating writes cease and replication continues, all replicas converge to a common application-visible state.
root key: A type of seed key, which can be used by Group Key Distribution Protocol servers to derive group keys for any combination of security descriptor and group key identifier in an Active Directory forest. Each root key is associated with a GUID, known as its root key identifier.
root key identifier: A GUID that identifies a root key, for use by a Group Key Distribution Protocol server in deriving group keys.
RPC protocol sequence: A character string that represents a valid combination of a remote procedure call (RPC) protocol, a network layer protocol, and a transport layer protocol, as described in [C706] and [MS-RPCE].
security context: An abstract data structure that contains authorization information for a particular security principal in the form of a Token/Authorization Context (see [MS-DTYP] section 2.5.2). A server uses the authorization information in a security context to check access to requested resources. A security context also contains a key identifier that associates mutually established cryptographic keys, along with other information needed to perform secure communication with another security principal.
security descriptor: A data structure containing the security information associated with a securable object. A security descriptor identifies an object's owner by its security identifier (SID). If access control is configured for the object, its security descriptor contains a discretionary access control list (DACL) with SIDs for the security principals who are allowed or denied access. Applications use this structure to set and query an object's security status. The security descriptor is used to guard access to an object as well as to control which type of auditing takes place when the object is accessed. The security descriptor format is specified in [MS-DTYP] section 2.4.6; a string representation of security descriptors, called SDDL, is specified in [MS-DTYP] section 2.5.1.
security principal: A unique entity, also referred to as a principal, that can be authenticated by Active Directory. It frequently corresponds to a human user, but also can be a service that offers a resource to other security principals. Other security principals might be a group, which is a set of principals. Groups are supported by Active Directory.
seed key: A cryptographically random quantity that can be used to derive one or more cryptographic keys for use with specific cryptographic algorithms.
server configuration: An Active Directory object that contains a set of configuration parameters to be used when creating or updating a root key. A server configuration object is required in Active Directory with the RDN described in section 1.9 for successful operation of the Group Key Distribution Protocol.
Unicode string: A Unicode 8-bit string is an ordered sequence of 8-bit units, a Unicode 16-bit string is an ordered sequence of 16-bit code units, and a Unicode 32-bit string is an ordered sequence of 32-bit code units. In some cases, it could be acceptable not to terminate with a terminating null character. Unless otherwise specified, all Unicode strings follow the UTF-16LE encoding scheme with no Byte Order Mark (BOM).
universally unique identifier (UUID): A 128-bit value. UUIDs can be used for multiple purposes, from tagging objects with an extremely short lifetime, to reliably identifying very persistent objects in cross-process communication such as client and server interfaces, manager entry-point vectors, and RPC objects. UUIDs are highly likely to be unique. UUIDs are also known as globally unique identifiers (GUIDs) and these terms are used interchangeably in the Microsoft protocol technical documents (TDs). Interchanging the usage of these terms does not imply or require a specific algorithm or mechanism to generate the UUID. Specifically, the use of this term does not imply or require that the algorithms described in [RFC4122] or [C706] must be used for generating the UUID.