Microsoft Vendor-specific RADIUS Attributes
RFC 2548
Network Working Group G. Zorn
Request for Comments: 2548 Microsoft Corporation
Category: Informational March 1999
Microsoft Vendor-specific RADIUS Attributes
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
This document describes the set of Microsoft vendor-specific RADIUS
attributes. These attributes are designed to support Microsoft
proprietary dial-up protocols and/or provide support for features
which is not provided by the standard RADIUS attribute set [3]. It
is expected that this memo will be updated whenever Microsoft defines
a new vendor-specific attribute, since its primary purpose is to
provide an open, easily accessible reference for third-parties
wishing to interoperate with Microsoft products.
1. Specification of Requirements
In this document, the key words "MAY", "MUST, "MUST NOT", "optional",
"recommended", "SHOULD", and "SHOULD NOT" are to be interpreted as
described in [2].
2. Attributes
The following sections describe sub-attributes which may be
transmitted in one or more RADIUS attributes of type Vendor-Specific
[3]. More than one sub-attribute MAY be transmitted in a single
Vendor-Specific Attribute; if this is done, the sub-attributes SHOULD
be packed as a sequence of Vendor-Type/Vendor-Length/Value triples
following the inital Type, Length and Vendor-ID fields. The Length
field of the Vendor-Specific Attribute MUST be set equal to the sum
of the Vendor-Length fields of the sub-attributes contained in the
Vendor-Specific Attribute, plus six. The Vendor-ID field of the
Vendor-Specific Attribute(s) MUST be set to decimal 311 (Microsoft).
Zorn Informational [Page 1]
RFC 2548 Microsoft Vendor-specific RADIUS Attributes March 1999
2.1. Attributes for Support of MS-CHAP Version 1
2.1.1. Introduction
Microsoft created Microsoft Challenge-Handshake Authentication
Protocol (MS-CHAP) [4] to authenticate remote Windows workstations,
providing the functionality to which LAN-based users are accustomed.
Where possible, MS-CHAP is consistent with standard CHAP [5], and the
differences are easily modularized. Briefly, the differences between
MS-CHAP and standard CHAP are:
* MS-CHAP is enabled by negotiating CHAP Algorithm 0x80 in LCP
option 3, Authentication Protocol.
* The MS-CHAP Response packet is in a format designed for
compatibility with Microsoft Windows NT 3.5, 3.51 and 4.0,
Microsoft Windows95, and Microsoft LAN Manager 2.x networking
products. The MS-CHAP format does not require the authenticator
to store a clear-text or reversibly encrypted password.
* MS-CHAP provides an authenticator-controlled authentication
retry mechanism.
* MS-CHAP provides an authenticator-controlled password changing
mechanism.
* MS-CHAP defines an extended set of reason-for-failure codes,
returned in the Failure packet Message field.
The attributes defined in this section reflect these differences.
2.1.2. MS-CHAP-Challenge
Description
This Attribute contains the challenge sent by a NAS to a Microsoft
Challenge-Handshake Authentication Protocol (MS-CHAP) user. It
MAY be used in both Access-Request and Access-Challenge packets.
A summary of the MS-CHAP-Challenge Attribute format is shown below.
The fields are transmitted from left to right.
Zorn Informational [Page 2]
RFC 2548 Microsoft Vendor-specific RADIUS Attributes March 1999
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Type | Vendor-Length | String...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Vendor-Type
11 for MS-CHAP-Challenge.
Vendor-Length
> 2
String
The String field contains the MS-CHAP challenge.
2.1.3. MS-CHAP-Response
Description
This Attribute contains the response value provided by a PPP
Microsoft Challenge-Handshake Authentication Protocol (MS-CHAP)
user in response to the challenge. It is only used in Access-
Request packets.
A summary of the MS-CHAP-Response Attribute format is shown below.
The fields are transmitted from left to right.
Zorn Informational [Page 3]
RFC 2548 Microsoft Vendor-specific RADIUS Attributes March 1999
Show full document text