RADIUS Version 1.1
draft-ietf-radext-radiusv11-01
The information below is for an old version of the document.
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| Author | Alan DeKok | ||
| Last updated | 2023-05-24 (Latest revision 2023-04-26) | ||
| Replaces | draft-dekok-radext-radiusv11 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-radext-radiusv11-01
RADEXT Working Group A. DeKok
Internet-Draft FreeRADIUS
Updates: 6614, 7360 (if approved) 24 May 2023
Intended status: Experimental
Expires: 25 November 2023
RADIUS Version 1.1
draft-ietf-radext-radiusv11-01
Abstract
This document defines Application-Layer Protocol Negotiation
Extensions for use with RADIUS/TLS and RADIUS/DTLS. These extensions
permit the negotiation of an additional application protocol for
RADIUS over (D)TLS. No changes are made to RADIUS/UDP or RADIUS/TCP.
The extensions allow the negotiation of a transport profile where the
RADIUS shared secret is no longer used, and all MD5-based packet
signing and attribute obfuscation methods are removed. When this
extension is used, the previous Authenticator field is repurposed to
contain an explicit request / response identifier, called a Token.
The Token also allows more than 256 packets to be outstanding on one
connection.
This extension can be seen as a transport profile for RADIUS, as it
is not an entirely new protocol. It uses the existing RADIUS packet
layout and attribute format without change. As such, it can carry
all present and future RADIUS attributes. Implementation of this
extension requires only minor changes to the protocol encoder and
decoder functionality. The protocol defined by this extension is
named "RADIUS version 1.1", or "RADIUS/1.1".
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-radext-radiusv11/.
Discussion of this document takes place on the RADEXT Working Group
mailing list (mailto:radext@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/radext/.
Source for this draft and an issue tracker can be found at
https://github.com/freeradius/radiusv11.git.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 25 November 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. The RADIUS/1.1 Transport profile for RADIUS . . . . . . . . . 7
3.1. ALPN Name for RADIUS/1.1 . . . . . . . . . . . . . . . . 7
3.2. Operation of ALPN . . . . . . . . . . . . . . . . . . . . 8
3.3. Configuration of ALPN for RADIUS/1.1 . . . . . . . . . . 9
3.3.1. Tabular Summary . . . . . . . . . . . . . . . . . . . 11
3.4. Additional TLS issues . . . . . . . . . . . . . . . . . . 12
3.5. Session Resumption . . . . . . . . . . . . . . . . . . . 12
4. RADIUS/1.1 Packet and Attribute Formats . . . . . . . . . . . 13
4.1. RADIUS/1.1 Packet Format . . . . . . . . . . . . . . . . 13
4.2. The Token Field . . . . . . . . . . . . . . . . . . . . . 14
4.2.1. Sending Packets . . . . . . . . . . . . . . . . . . . 15
4.2.2. Receiving Packets . . . . . . . . . . . . . . . . . . 15
5. Attribute handling . . . . . . . . . . . . . . . . . . . . . 16
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5.1. Obfuscated Attributes . . . . . . . . . . . . . . . . . . 16
5.1.1. User-Password . . . . . . . . . . . . . . . . . . . . 17
5.1.2. CHAP-Challenge . . . . . . . . . . . . . . . . . . . 18
5.1.3. Tunnel-Password . . . . . . . . . . . . . . . . . . . 18
5.1.4. Vendor-Specific Attributes . . . . . . . . . . . . . 19
5.2. Message-Authenticator . . . . . . . . . . . . . . . . . . 19
5.3. Message-Authentication-Code . . . . . . . . . . . . . . . 20
5.4. CHAP, MS-CHAP, etc. . . . . . . . . . . . . . . . . . . . 20
5.5. Original-Packet-Code . . . . . . . . . . . . . . . . . . 20
6. Other Considerations . . . . . . . . . . . . . . . . . . . . 21
6.1. Status-Server . . . . . . . . . . . . . . . . . . . . . . 21
6.2. Proxies . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.3. Crypto-Agility . . . . . . . . . . . . . . . . . . . . . 22
6.4. Error-Cause Attribute . . . . . . . . . . . . . . . . . . 23
6.5. Future Standards . . . . . . . . . . . . . . . . . . . . 24
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 25
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 25
9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 26
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
13.1. Normative References . . . . . . . . . . . . . . . . . . 28
13.2. Informative References . . . . . . . . . . . . . . . . . 28
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
The RADIUS protocol [RFC2865] uses MD5 [RFC1321] to sign packets, and
to obfuscate certain attributes. Decades of cryptographic research
has shown that MD5 is insecure, and that MD5 should no longer be
used. These discussions are most notably in [RFC6151], and in
Section 3 of [RFC6421], among others. In addition, the dependency on
MD5 makes it impossible to use RADIUS in a FIPS-140 compliant system,
as FIPS-140 forbids systems from relying on insecure cryptographic
methods for security.
While RADIUS originally used UDP transport, additional transport
protocols were defined for TCP ([RFC6613]), TLS ([RFC6614]), and DTLS
([RFC7360]). However, those transport protocols still relied on MD5.
That is, the shared secret was used along with MD5, even when the
RADIUS packets were being transported in (D)TLS. At the time, the
consensus of the RADEXT working group was that this continued use of
MD5 was acceptable. TLS was seen as a simple "wrapper" around
RADIUS, while using a fixed shared secret. The intention at the time
was to allow the use of (D)TLS while making essentially no changes to
the basic RADIUS encoding, decoding, signing, and packet validation.
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The ensuing years have shown that it is important for RADIUS to
remove its dependency on MD5. The continued use of MD5 is no longer
acceptable in a security-conscious environment. The use of MD5 in
[RFC6614] and [RFC7360] adds no security or privacy over that
provided by TLS. It is time to remove the use of MD5 from RADIUS.
This document defines an Application-Layer Protocol Negotiation
(ALPN) [RFC7301] extension for RADIUS over (D)TLS which removes their
dependency on MD5. Systems which implement this transport profile
are therefore capable of being FIPS-140 compliant. This extension
can best be understood as a transport profile for RADIUS, rather than
a whole-sale revision of the RADIUS protocol. A preliminary
implementation has shown that only minor code changes are required to
support RADIUS/1.1 on top of an existing RADIUS server.
While this document permits MD5 to be removed when using (D)TLS
transports, it makes no changes to UDP or TCP transports. It is
therefore RECOMMENDED that those transports only be used within
secure networks, and only used in situations where FIPS compliance is
not an issue.
The changes from traditional TLS-based transports for RADIUS are as
follows:
* ALPN is used for negotiation of this extension,
* TLS 1.3 or later is required,
* All uses of the RADIUS shared secret have been removed,
* The now-unused Request and Response Authenticator fields have been
repurposed to carry an opaque Token which identifies requests and
responses,
* The Identifier field is no longer used, and has been replaced by
the Token field,
* The Message-Authenticator attribute ([RFC3579] Section 3.2) is not
sent in any packet, and if received is ignored,
* Attributes such as User-Password, Tunnel-Password, and MS-MPPE
keys are sent encoded as "text" ([RFC8044] Section 3.4) or
"octets" ([RFC8044] Section 3.5), without the previous MD5-based
obfuscation. This obfuscation is no longer necessary, as the data
is secured and kept private through the use of TLS,
* Future RADIUS specifications are forbidden from defining new
cryptographic primitives.
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The following items are left unchanged from traditional TLS-based
transports for RADIUS:
* The RADIUS packet header is the same size, and the Code and Length
fields ([RFC2865] Section 3) have the same meaning as before,
* The default 4K packet size is unchanged, although [RFC7930] can
still be leveraged to use larger packets,
* All attributes which have simple encodings (i.e. without using MD5
obfuscation), all have the same encoding and meaning as before,
* As this extension is a transport profile for one "hop" (client to
server connection), it does not impact any other connection used
by a client or server. The only systems which are aware that this
transport profile is in use are the client and server who have
negotiated the use of this extension on a particular shared
connection,
* This extension uses the same ports (2083/tcp and 2083/udp) which
are defined for RADIUS/TLS [RFC6614] and RADIUS/DTLS [RFC7360].
A major benefit of this extensions is that a home server which
implements it can also choose to also be fully FIPS-140 compliant.
That is, a home server can remove all uses of MD4 and MD5. In that
case, however, the home server will not support CHAP, MS-CHAP, or any
authentication method which uses MD4 or MD5. We note that the choice
of which authentication method to accept is always left to the home
server. This specification does not change any authentication method
carried in RADIUS, and does not mandate (or forbid) the use of any
authentication method for any system.
As for proxies, there was never a requirement that proxies implement
CHAP or MS-CHAP authentication. So far as a proxy is concerned,
attributes relating to CHAP and MS-CHAP are simply opaque data that
is transported unchanged to the next hop. It is therefore possible
for a FIPS-140 compliant proxy to transport authentication methods
which depend on MD4 or MD5, so long as that data is forwarded to a
home server which supports those methods.
We reiterate that the decision to support (or not) any authentication
method is entirely site local, and is not a requirement of this
specification. The contents or meaning of any RADIUS attribute other
than Message-Authenticator (and similar attributes) are not modified.
The only change to the Message-Authenticator attribute is that is no
longer used.
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Unless otherwise described in this document, all RADIUS requirements
apply to this extension. That is, this specification defines a
transport profile for RADIUS. It is not an entirely new protocol,
and it defines only minor changes to the existing RADIUS protocol.
It does not change the RADIUS packet format, attribute format, etc.
This specification is compatible with all RADIUS attributes, past,
present, and future.
This specification is compatible with existing implementations of
RADIUS/TLS and RADIUS/DTLS. There is no need to define an ALPN name
for those protocols, as implementations can simply not send an ALPN
name when those protocols are used. Backwards compatibility with
existing implementations is both required, and assumed.
This specification is compatible with all past and future RADIUS
specifications. There is no need for any RADIUS specification to
mention this transport profile by name, or to make provisions for
this specification. This specification defines how to transform
RADIUS into RADIUS/1.1, and no further discussion of that
transformation is necessary.
In short, when negotiated on a connection, this specification permits
implementations to avoid MD5 when signing packets, or when
obfuscating certain attributes.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
* ALPN
Application-Layer Protocol Negotiation, as defined in [RFC7301].
* RADIUS
The Remote Authentication Dial-In User Service protocol, as
defined in [RFC2865], [RFC2866], and [RFC5176] among others.
While this protocol can be viewed as "RADIUS/1.0", for simplicity
and historical compatibility, we keep the name "RADIUS".
* RADIUS/UDP
RADIUS over the User Datagram Protocol as define above.
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* RADIUS/TCP
RADIUS over the Transmission Control Protocol [RFC6613].
* RADIUS/TLS
RADIUS over the Transport Layer Security protocol [RFC6614].
* RADIUS/DTLS
RADIUS over the Datagram Transport Layer Security protocol
[RFC7360].
* RADIUS over TLS
Either RADIUS/TLS or RADIUS/DTLS. This terminology is used
instead of alternatives such as "RADIUS/(D)TLS", or "either
RADIUS/TLS or RADIUS/DTLS".
* RADIUS/1.1
The transport profile defined in this document, which stands for
"RADIUS version 1.1". We use RADIUS/1.1 to refer interchangeably
to TLS and DTLS transport.
* TLS
The Transport Layer Security protocol. Generally when we refer to
TLS in this document, we are referring interchangeably to TLS or
DTLS transport.
3. The RADIUS/1.1 Transport profile for RADIUS
This section describes the ALPN transport profile in detail. It
first gives the name used for ALPN, and then describes how ALPN is
configured and negotiated by client and server. It then concludes by
discussing TLS issues such as what to do for ALPN during session
resumption.
3.1. ALPN Name for RADIUS/1.1
The ALPN name defined for RADIUS/1.1 is as follows:
"radius/1.1"
The protocol defined by this specification.
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Where ALPN is not configured or is not received in a TLS connection,
systems supporting ALPN MUST NOT use RADIUS/1.1.
Where ALPN is configured, the client signals support by sending the
ALPN string "radius/1.1". The server can accept this proposal and
reply with the ALPN string "radius/1.1", or reject this proposal, and
not reply with any ALPN string.
Implementations MUST signal ALPN "radius/1.1" in order for it to be
used in a connection. Implementations MUST NOT have an
administrative flag which causes a connection to use "radius/1.1",
but which does not signal that protocol via ALPN.
The next step in defining RADIUS/1.1 is to review how ALPN works.
3.2. Operation of ALPN
Once a system has been configured to support ALPN, it is negotiated
on a per-connection basis as per [RFC7301]. We give a brief overview
here of ALPN in order to provide a high-level description ALPN for
readers who do not need to understand [RFC7301] in detail. This
section is not normative.
1) The client proposes ALPN by sending an ALPN extension in the
ClientHello. This extension lists one or more application protocols
by name.
2) The server receives the extension, and validates the application
protocol name against the list it has configured.
If the server finds no acceptable common protocols (ALPN or
otherwise), it closes the connection.
3) Otherwise, the server return a ServerHello with either no ALPN
extension, or an ALPN extension with only one named application
protocol.
If the client did not signal ALPN, or the server does not accept
the ALPN proposal, the server does not reply with any ALPN name.
4) The client receives the ServerHello, validates the received
application protocol (if any) against the name it sent, and records
the application protocol which was chosen.
This check is necessary in order for the client to both know which
protocol the server has selected, and to validate that the
protocol sent by the server is one which is acceptable to the
client.
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The next step in defining RADIUS/1.1 is to define how ALPN is
configured on the client and server, and to give more detailed
requirements on ALPN configuration and operation.
3.3. Configuration of ALPN for RADIUS/1.1
Clients or servers supporting this specification can do so by
extending their TLS configuration through the addition of a new
configuration flag, called "RADIUS/1.1" here. The exact name given
below does not need to be used, but it is RECOMMENDED that
administrative interfaces or programming interfaces use a similar
name in order to provide consistent terminology. This flag controls
how the implementation signals use of this protocol via ALPN.
Configuration Flag Name
RADIUS/1.1
Allowed Values
forbid - Forbid the use of RADIUS/1.1
A client with this configuration MUST NOT signal any protocol
name via ALPN. The system MUST use RADIUS over TLS as defined
in [RFC6614] and [RFC7360].
A server with this configuration MUST NOT signal any protocol
name via ALPN. The system MUST use RADIUS over TLS as defined
in [RFC6614] and [RFC7360].
A server with this configuration MUST NOT close the connection
if it receives an ALPN name from the client. Instead, it
simply does not reply with ALPN, and finishes the TLS
connection setup as defined previously in [RFC6614]
allow - Allow (or negotiate) the use of RADIUS/1.1
This value MUST be the default setting for implementations
which support this specification.
A client with this configuration MUST use ALPN to signal that
"radius/1.1" can be used. The client MUST use RADIUS/1.1 if
the server responds signalling ALPN "radius/1.1". If no ALPN
response is received from the server, the client MUST use
RADIUS over TLS as defined in previous specifications.
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A server with this configuration MAY reply to a client with an
ALPN string of "radius/1.1", but only if the client first
signals support for that protocol name via ALPN. If the client
does not signal ALPN, the server MUST NOT reply with any ALPN
name.
require - Require the use of RADIUS/1.1
A client with this configuration MUST use ALPN to signal that
"radius/1.1" can be used. The client MUST use RADIUS/1.1 if
the server responds signalling ALPN "radius/1.1". If no ALPN
response is received from the server, the client MUST close the
connection.
A server with this configuration MUST close the connection if
the client does not signal "radius/1.1" via ALPN.
A server with this configuration MUST reply with the ALPN
protocol name "radius/1.1" if the client signals "radius/1.1".
The server and client both MUST then use RADIUS/1.1 as the
application-layer protocol. There is no reason to signal
support for a protocol, and then not use it.
Note that systems implementing this specification, but configured
with "forbid" as above, will behave exactly the same as systems which
do not implement this specification.
If a client or server determines that there are no compatible
application protocol names, then as per [RFC7301] Section 3.2, it
MUST send a TLS alert of "no_application_protocol" (120), which
signals to the other end that there is no compatible application
protocol. It MUST then close the connection. This requirement
applies to both new sessions, and to resumed sessions.
It is RECOMMENDED that a descriptive error is logged in this
situation, so that an administrator can determine why a particular
connection failed. The log message SHOULD include information about
the other end of the connection, such as IP address, certificate
information, etc. Similarly, a system receiving a TLS alert of
"no_application_protocol" SHOULD log a descriptive error message.
Such error messages are critical for helping administrators to
diagnose connectivity issues.
Note that there is no way for a client to signal if its RADIUS/1.1
configuration is set to "allow" or "require". The client MUST signal
"radius/1.1" via ALPN when it is configured with either value. The
difference between the two values for the client is only in how it
handles responses from the server.
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Similarly, there is no way for a server to signal if its RADIUS/1.1
configuration is set to "allow" or "require". In both cases if it
receives "radius/1.1" from the client via ALPN, the server MUST reply
with "radius/1.1", and agree to that negotiation. The difference
between the two values for the server is how it handles the situation
when no ALPN is signalled from the client.
3.3.1. Tabular Summary
The preceding text gives a large number of recommendations. In order
to give a simpler description of the outcomes, a table of possible
behaviors for client/server values of the RADIUS/1.1 flag is given
below. This table and the names given below are for informational
and descriptive purposes only. This section is not normative.
Server
no ALPN | forbid | allow | require
Client |--------------------------------------
----------|
No ALPN | RADIUS RADIUS RADIUS Close
| Note 1
|
forbid | RADIUS RADIUS RADIUS Close
| Note 1
|
allow | RADIUS RADIUS OK OK
| Note 3 Note 3
|
require | Close Close OK OK
| Note 2 Note 2
Figure 1: Possible outcomes for ALPN Negotiation
The table entries above have the following meaning:
Close
Note 1 - the server closes the connection, as the client does not
do RADIUS/1.1.
Note 2 - the client closes the connection, as the server does not
do RADIUS/1.1
RADIUS
RADIUS over TLS is used. RADIUS/1.1 is not used.
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Note 3 - The client sends ALPN, but the server does not reply with
ALPN.
OK
RADIUS/1.1 is signalled and used by both client and server.
The client sends "radius/1.1" via ALPN, and the server replies
with "radius/1.1" via ALPN.
3.4. Additional TLS issues
Implementations of this specification MUST require TLS version 1.3 or
later.
3.5. Session Resumption
[RFC7301] Section 3.1 states that ALPN is negotiated on each
connection, even if session resumption is used:
When session resumption or session tickets [RFC5077] are used, the
previous contents of this extension are irrelevant, and only the
values in the new handshake messages are considered.
In order to prevent down-bidding attacks, RADIUS systems which
negotiate the "radius/1.1" protocol MUST associate that information
with the session ticket, and enforce the use of "radius/1.1" on
session resumption. That is, if "radius/1.1" was negotiated for a
session, both clients and servers MUST behave as if the RADIUS/1.1
flag was set to "require" for that session.
A client which is resuming a "radius/1.1" connection MUST advertise
only the capability to do "radius/1.1" for the resumed session. That
is, even if the client configuration is "allow" for new connections,
it MUST signal "radius/1.1" when resuming a session which had
previously negotiated "radius/1.1".
Similarly, when a server does resumption for a session which had
previously negotiated "radius/1.1", If the client attempts to resume
the sessions without signalling the use of RADIUS/1.1, the server
MUST close the connection. The server MUST send an appropriate TLS
error, and also SHOULD log a descriptive message as described above.
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In contrast, there is no requirement for a client or server to force
the use of [RFC6614] RADIUS/TLS on session resumption. Clients are
free to signal support for "radius/1.1" on resumed sessions, even if
the original session did not negotiate "radius/1.1". Servers are
free to accept this request, and to negotiate the use of "radius/1.1"
for such sessions.
4. RADIUS/1.1 Packet and Attribute Formats
This section describes the application-layer data which is sent
inside of (D)TLS when using the RADIUS/1.1 protocol. Unless
otherwise discussed herein, the application-layer data is unchanged
from traditional RADIUS. This protocol is only used when
"radius/1.1" has been negotiated by both ends of a connection.
4.1. RADIUS/1.1 Packet Format
When RADIUS/1.1 is used, the RADIUS header is modified from standard
RADIUS. While the header has the same size, some fields have
different meaning. The Identifier and the Request / Reeponse
Authenticator fields are no longer used. Any operations which depend
on those fields MUST NOT be performed. As packet signing and
security are handled by the TLS layer, RADIUS-specific cryptographic
primitives are no longer used.
A summary of the RADIUS/1.1 packet format is shown below. The fields
are transmitted from left to right.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Reserved-1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Reserved-2 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attributes ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 2: The RADIUS/1.1 Packet Format
Code
The Code field is one octet, and identifies the type of RADIUS
packet.
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The meaning of the Code field is unchanged from previous RADIUS
specifications.
Reserved-1
The Reserved-1 field is one octet. It MUST be set to zero for all
packets.
This field was previously called "Identifier" in RADIUS. It is
now unused, as the Token field replaces it as the way to identify
requests and responses. The Reserver-1 field MUST be ignoored
when receiving a packet.
Length
The Length field is two octets.
The meaning of the Length field is unchanged from previous RADIUS
specifications.
Token
The Token field is four octets, and aids in matching requests and
replies, as a replacement for the Identifier field. The RADIUS
server can detect a duplicate request if it receives the same
Token value for two packets on a particular connection.
Further requirements are given below in Section 4.2.1 for sending
packets, and in Section 4.2.2 for receiving packets.
Reserved-2
The Reserved-2 field is twelve (12) octets in length.
These octets MUST be set to zero when sending a packet.
These octets MUST be ignored when receiving a packet.
These octets are reserved for future protocol extensions.
4.2. The Token Field
This section describes in more detail how the Token field is used.
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4.2.1. Sending Packets
The Token field MUST change for every new unique packet which is sent
on the same connection. For DTLS transport, it is possible to
retransmit duplicate packets, in which case the Token value MUST NOT
be changed when a duplicate packet is (re)sent. When the contents of
a retransmitted packet change for any reason (such changing Acct-
Delay-Time as discussed in [RFC2866] Section 5.2), the Token value
MUST be changed. Note that on reliable transports, packets are never
retransmitted, and therefore every new packet sent has a unique Token
value.
Systems generating the Token can do so via any method they choose,
but for simplicity, it is RECOMMENDED that the Token values be
generated from a 32-bit counter which is unique to each connection.
Such a counter SHOULD be initialized to a random value, taken from a
random number generator, whenever a new connection is opened. The
counter can then be incremented for every new packet that the client
sends.
As there is no special meaning for the Token, there is no meaning
when a counter "wraps" around from a high value back to zero. The
originating system can simply continue to increment the Token value.
Once a RADIUS response to a request has been received and there is no
need to track the packet any longer, the Token value MAY be reused.
This SHOULD be after a suitable delay to ensure that Token values do
not conflict with outstanding packets. Note that the counter method
described above for generating Token values will automatically ensure
a long delay between multiple uses of the same Token value. The only
cost for tracking Tokens is a single 32-bit counter. Any other
method of generating unique and non-conflicting Token values is
likely to require substantially more resources to track outstanding
Token values.
If a RADIUS client has multiple independent subsystems which send
packets to a server, each subsystem MAY open a new port that is
unique to that subsystem. There is no requirement that all packets
go over one particular connection. That is, despite the use of a
32-bit Token field, RADIUS/1.1 clients are still permitted to open
multiple source ports as discussed in [RFC2865] Section 2.5.
4.2.2. Receiving Packets
A server which receives RADIUS/1.1 packets MUST perform packet
deduplication for all situations where it is required by RADIUS.
Where RADIUS does not require deduplication (e.g. TLS transport),
the server SHOULD NOT do deduplication.
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We note that in previous RADIUS specifications, the Identifier field
could have the same value for different types of packets on the same
connection, e.g. for Access-Request and Accounting-Request. This
overlap required that RADIUS clients and servers track the Identifier
field, not only on a per-connection basis, but also on a per-packet
type basis. This behavior adds complexity to implementations.
When using RADIUS/1.1, implementations MUST instead do deduplication
only on the Token field, and not on any other field or fields in the
packet header. A server MUST treat the Token as being an opaque
field with no intrinsic meaning. While the recommendation above is
for the sender to use a counter, other implementations are possible,
valid, and permitted. For example, a system could use a pseudo-
random number generator with a long period to generate unique values
for the Token field.
Where Token deduplication is done, it MUST be done on a per-
connection basis. If two packets which are received on different
connections contain the same Token value, then those packets MUST be
treated as distinct (i.e. different) packets.
This change from RADIUS means that the Identifier field is no longer
useful. The Reserved-1 field (previously used as the Identifier)
MUST be set to zero for all RADIUS/1.1 packets. RADIUS/1.1
Implementations MUST NOT examine this field or use it for packet
tracking or deduplication.
5. Attribute handling
Most attributes in RADIUS have no special encoding "on the wire", or
any special meaning between client and server. Unless discussed in
this section, all RADIUS attributes are unchanged in this
specification. This requirement includes attributes which contain a
tag, as defined in [RFC2868].
5.1. Obfuscated Attributes
As (D)TLS is used for this specification, there is no need to hide
the contents of an attribute on a hop-by-hop basis. The TLS
transport ensures that all attribute contents are hidden from any
observer.
Attributes defined as being obfuscated via MD5 no longer have the
obfuscation step applied when RADIUS/1.1 is used. Instead, those
attributes are simply encoded as their values, as with any other
attribute. Their encoding method MUST follow the encoding for the
underlying data type, with any encryption / obfuscation step omitted.
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There are often concerns where RADIUS is used, that passwords are
sent "in cleartext" across the network. This allegation was never
true for RADIUS, and definitely untrue when (D)TLS transport is used.
While passwords are encoded in packets as strings, the entire RADIUS
exchange including packets, attributes (and thus passwords) are
protected by TLS. For the unsure reader this protocol is the same
TLS which protects passwords used for web logins, e-mail reception
and sending, etc. As a result, any claims that passwords are sent
"in the clear" are categorically false.
There are risks from sending passwords over the network, even when
they are protected by TLS. One such risk somes from the common
practice of multi-hop RADIUS routing. As all security in RADIUS is
on a hop-by-hop basis, every proxy which receives a RADIUS packet can
see (and modify) all of the information in the packet. Sites wishing
to avoid proxies SHOULD use dynamic peer discovery [RFC7585], which
permits clients to make connections directly to authoritative servers
for a realm.
There are others ways to mitigate these risks. One is by ensuring
that the RADIUS over TLS session parameters are verified before
sending the password, usually via a method such as verifying a server
certificate. That is, passwords should only be sent to verified and
trusted parties. If the TLS session parameters are not verified,
then it is trivial to convince the RADIUS client to send passwords to
anyone.
Another way to mitigate these risks is for the system being
authenticated to use an authentication protocol which never sends
passwords (e.g. EAP-pwd [RFC5931]), or which sends passwords
protected by a TLS tunnel (e.g. EAP-TTLS [RFC5281]). The processes
to choose and configuring an authentication protocol are strongly
site-dependent, so further discussion of these issues are outside of
the scope of this document. The goal here is to ensure that the
reader has enough information to make an informed decision.
We note that as the RADIUS shared secret is no longer used, it is no
longer possible or necessary for any attribute to be obfuscated on a
hop-by-hop basis using the previous methods defined for RADIUS.
5.1.1. User-Password
The User-Password attribute ([RFC2865] Section 5.2) MUST be encoded
the same as any other attribute of data type 'string' ([RFC8044]
Section 3.5).
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The contents of the User-Password field MUST be at least one octet in
length, and MUST NOT be more than 128 octets in length. This
limitation is maintained from [RFC2865] Section 5.2 for compatibility
with legacy transports.
Note that the User-Password attribute is not of data type 'text'.
The original reason in [RFC2865] was because the attribute was
encoded as an opaque and obfuscated binary blob. We maintain that
data type here, even though the attribute is no longer obfuscated.
The contents of the User-Password attribute do not have to be
printable text, or UTF-8 data as per the definition of the 'text'
data type in [RFC8044] Section 3.4.
However, implementations should be aware that passwords are often
printable text, and where the passwords are printable text, it can be
useful to store and display them as printable text. Where
implementations can process non-printable data in the 'text' data
type, they MAY use the data type 'text' for User-Password.
5.1.2. CHAP-Challenge
[RFC2865] Section 5.3 allows for the CHAP challenge to be taken from
either the CHAP-Challenge attribute ([RFC2865] Section 5.40), or the
Request Authenticator field. Since RADIUS/1.1 connections no longer
use a Request Authenticator field, it is no longer possible to use
the Request Authenticator field as the CHAP-Challenge.
Clients which send CHAP-Password attribute ([RFC2865] Section 5.3) in
an Access-Request packet over a RADIUS/1.1 connection MUST also
include a CHAP-Challenge attribute ([RFC2865] Section 5.40).
Proxies may need to Access-Request packets over a non-RADIUS/1.1
transport and then forward those packets over a RADIUS/1.1
connection. In that case, if the received Access-Request packet
contains a CHAP-Password attribute but no CHAP-Challenge attribute,
the proxy MUST create a CHAP-Challenge attribute in the proxied
packet using the contents from the incoming Request Authenticator of
the received packet.
5.1.3. Tunnel-Password
The Tunnel-Password attribute ([RFC2868] Section 3.5) MUST be encoded
the same as any other attribute of data type 'string' which contains
a tag, such as Tunnel-Client-Endpoint ([RFC2868] Section 3.3). Since
the attribute is no longer obfuscated, there is no need for a Salt
field or Data-Length fields as described in [RFC2868] Section 3.5,
and the textual value of the password can simply be encoded as-is.
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Note that the Tunnel-Password attribute is not of data type 'text'.
The original reason in [RFC2868] was because the attribute was
encoded as an opaque and obfuscated binary blob. We maintain that
data type here, even though the attribute is no longer obfuscated.
The contents of the Tunnel-Password attribute do not have to be
printable text, or UTF-8 data as per the definition of the 'text'
data type in [RFC8044] Section 3.4.
However, implementations should be aware that passwords are often
printable text, and where the passwords are printable text, it can be
useful to store and display them as printable text. Where
implementations can process non-printable data in the 'text' data
type, they MAY use the data type 'text' for Tunnel-Password.
5.1.4. Vendor-Specific Attributes
Any Vendor-Specific attribute which uses similar obfuscation MUST be
encoded as per their base data type. Specifically, the MS-MPPE-Send-
Key and MS-MPPE-Recv-Key attributes ([RFC2548] Section 2.4) MUST be
encoded as any other attribute of data type 'string' ([RFC8044]
Section 3.4).
5.2. Message-Authenticator
The Message-Authenticator attribute ([RFC3579] Section 3.2) MUST NOT
be sent over a RADIUS/1.1 connection. That attribute is no longer
used or needed.
If the Message-Authenticator attribute is received over a RADIUS/1.1
connection, the attribute MUST be silently discarded, or treated as
an "invalid attribute", as defined in [RFC6929] Section 2.8. That
is, the Message-Authenticator attribute is no longer used to sign
packets. Its existence (or not) in this transport is meaningless.
We note that any packet which contains a Message-Authenticator
attribute can still be processed. There is no need to discard an
entire packet simply because it contains a Message-Authenticator
attribute. Only the Message-Authenticator attribute itself is
ignored.
For proxies, the Message-Authenticator attribute was always defined
as being created and consumed on a "hop by hop" basis. That is, a
proxy which received a Message-Authenticator attribute from a client
would never forward that attribute as-is to another server. Instead,
the proxy would either suppress, or re-create, the Message-
Authenticator attribute in the outgoing request. This existing
behavior is leveraged in RADIUS/1.1 to suppress the use of Message-
Authenticator over a RADIUS/1.1 connection.
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5.3. Message-Authentication-Code
Similarly, the Message-Authentication-Code attribute defined in
[RFC6218] Section 3.3 MUST NOT be sent over a RADIUS/1.1 connection.
That attribute MUST be treated the same as Message-Authenticator,
above.
As the Message-Authentication-Code attribute is no longer used, the
related MAC-Randomizer attribute [RFC6218] Section 3.2 is also no
longer used. It MUST also be treated the same way as Message-
Authenticator, above.
5.4. CHAP, MS-CHAP, etc.
While some attributes such as CHAP-Password, etc. depend on insecure
cryptographic primitives such as MD5, these attributes are treated as
opaque blobs when sent between a RADIUS client and server. The
contents of the attributes are not obfuscated, and they do not depend
on the RADIUS shared secret. As a result, these attributes are
unchanged in RADIUS/1.1.
A server implementing this specification can proxy CHAP, MS-CHAP,
etc. without any issue. A home server implementing this
specification can authenticate CHAP, MS-CHAP, etc. without any issue.
5.5. Original-Packet-Code
[RFC7930] Section 4 defines an Original-Packet-Code attribute. This
attribute is needed because otherwise it is impossible to correlate
the Protocol-Error response packet with a particular request packet.
The definition in [RFC7930] Section 4 describes the reasoning behind
this need:
The Original-Packet-Code contains the code from the request that
generated the protocol error so that clients can disambiguate
requests with different codes and the same ID.
This attribute is no longer needed in RADIUS/1.1. The Identifier
field is unused, so it impossible for two requests to have the "same"
ID. Instead, the Token field permits clients and servers to
correlate requests and responses, independent of the Code being used.
Therefore, the Original-Packet-Code attribute ([RFC7930] Section 4)
MUST NOT be sent over a RADIUS/1.1 connection. That attribute is no
longer used or needed.
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If the Original-Packet-Code attribute is received over a RADIUS/1.1
connection, the attribute MUST either be silently discarded, or be
treated an as "invalid attribute", as defined in [RFC6929]
Section 2.8. That is, existence of the Token field means that the
Original-Packet-Code attribute is no longer needed to correlate
Protocol-Error replies with outstanding requests.
We note that any packet which contains an Original-Packet-Code
attribute can still be processed. There is no need to discard an
entire packet simply because it contains an Original-Packet-Code
attribute.
6. Other Considerations
Most of the differences between RADIUS and RADIUS/1.1 are in the
packet header and attribute handling, as discussed above. The
remaining issues are a small set of unrelated topics, and are
discussed here.
6.1. Status-Server
[RFC6613] Section 2.6.5, and by extension [RFC7360], suggest that the
Identifier value zero (0) be reserved for use with Status-Server as
an application-layer watchdog. This practice MUST NOT be used for
RADIUS/1.1, as the Identifier field is no longer used.
The rationale for reserving one value of the Identifier field was the
limited number of Identifiers available (256), and the overlap in
Identifiers between Access-Request packets and Status-Server packets.
If all 256 Identifier values had been used to send Access-Request
packets, then there would be no Identifier value available for
sending a Status-Server packet.
In contrast, the Token field allows for 2^32 outstanding packets on
one RADIUS/1.1 connection. If there is a need to send a Status-
Server packet, it is always possible to allocate a new value for the
Token field. Similarly, the value zero (0) for the Token field has
no special meaning. The edge condition is that there are 2^32
outstanding packets on one connection with no new Token value
available for Status-Server. In which case there are other serious
issues, such as allowing billions of packets to be outstanding. The
safest way forward in that case is likely to just close the
connection.
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6.2. Proxies
A RADIUS proxy normally decodes and then re-encodes all attributes,
included obfuscated ones. A RADIUS proxy will not generally rewrite
the content of the attributes it proxies (unless site-local policy
requires such a rewrite). While some attributes may be modified due
to administrative or policy rules on the proxy, the proxy will
generally not rewrite the contents of attributes such as User-
Password, Tunnel-Password, CHAP-Password, MS-CHAP-Password, MS-MPPE
keys, etc. All attributes are therefore transported through a
RADIUS/1.1 connection without changing their values or contents.
A proxy may negotiate RADIUS/1.1 (or not) with a particular client or
clients, and it may negotiate RADIUS/1.1 (or not) with a server or
servers it connect to, in any combination. As a result, this
specification is fully compatible with all past, present, and future
RADIUS attributes.
6.3. Crypto-Agility
The crypto-agility requirements of [RFC6421] are addressed in
[RFC6614] Appendix C, and in Section 10.1 of [RFC7360]. This
specification makes no changes from, or additions to, those
specifications. The use of ALPN, and the removal of MD5 has no
impact on security or privacy of the protocol.
RADIUS/TLS has been widely deployed in at least eduroam [RFC7593] and
[EDUROAM] and in OpenRoaming [OPENROAMING]. RADIUS/DTLS has seen
less adoption, but it is known to be supported in many RADIUS clients
and servers.
It is RECOMMENDED that all implementations of RADIUS over TLS be
updated to support this specification. The effort to implement this
specification is minimal, and once implementations support it,
administrators can gain the benefit of it with little or no
configuration changes. This specification is backwards compatible
with [RFC6614] and [RFC7360]. It is only potentially subject to
down-bidding attacks if implementations do not enforce ALPN
negotiation correctly on session resumption.
All crypto-agility needed or used by this specification is
implemented in TLS. This specification also removes all
cryptographic primitives from the application-layer protocol (RADIUS)
being transported by TLS. As discussed in the following section,
this specification also bans the development of all new cryptographic
or crypto-agility methods in the RADIUS protocol.
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6.4. Error-Cause Attribute
The Error-Cause attribute is defined in [RFC5176]. The "Table of
Attributes" section given in [RFC5176] Section 3.6 permits that
attribute to appear in CoA-NAK and Disconnect-NAK packets. As no
other packet type is listed, the implication is that the Error-Cause
attribute cannot appear in any other packet. [RFC7930] also permits
Error-Cause to appear in Protocol-Error packets.
However, [RFC5080] Section 2.6.1 suggests that Error-Cause may appear
in Access-Reject packets. No reference is given for this change from
[RFC5176]. There is not even an acknowledgement that this suggestion
is a change from any previous specification. We correct that issue
here.
This specification updates [RFC5176] to allow the Error-Cause
attribute to appear in Access-Reject packets. It is RECOMMENDED that
implementations include the Error-Cause attribute in Access-Reject
packets where appropriate.
That is, the reason for sending the Access-Reject packet (or
Protocol-Error packet) may match a defined Error-Cause value. In
that case, it is useful for implementations to send an Error-Cause
attribute with that value. This behavior can help RADIUS system
administrators debug issues in complex proxy chains.
For example, a proxy may normally forward Access-Request packets
which contain EAP-Message attributes. The proxy can determine if the
contents of the EAP-Message are invalid, for example if the first
octet has value larger than 4. In that case, there may be no benefit
to forwarding the packet, as the home server will reject it. It may
then then possible for the proxy (with the knowledge and consent of
involved parties) to immediately reply with an Access-Reject
containing an Error-Cause attribute with value 202 for "Invalid EAP
Packet (Ignored)".
Another possibility is that if a proxy is configured to forward
packets for a particular realm, but it has determined that there are
no available connections to the next hop for that realm. In that
case, it is may be possible for the proxy (again with the knowledge
and consent of involved parties) to reply with an Access-Reject
containing an Error-Cause attribute with value 502 for "Request Not
Routable (Proxy)"
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These examples are given only for illustrative and informational
purposes. While it is useful to return an informative value for the
Error-Cause attribute, proxies can only modify the traffic they
forward with the explicit knowledge and concsent of all involved
parties.
6.5. Future Standards
Future work may define new attributes, packet types, etc. It is
important to be able to do such work without requiring that every new
standard mention RADIUS/1.1 explicitly. Instead, this document
defines a mapping from RADIUS to RADIUS/1.1 which covers all RADIUS
practices and cryptographic primitives in current use. As a result,
any new standard which uses the existing RADIUS practices can simply
inherit that mapping, and they do not need to mention RADIUS/1.1
explicitly.
We reiterate that this specification defines a new transport profile
for RADIUS. It does not define a completely new protocol. Any
future specification which defines a new attribute MUST define it for
RADIUS/UDP first, after which those definitions can be applied to
this transport profile.
New specifications MAY define new attributes which use the
obfuscation methods for User-Password as defined in [RFC2865]
Section 5.2, or for Tunnel-Password as defined in [RFC2868]
Section 3.5. There is no need for those specifications to describe
how those new attributes are transported in RADIUS/1.1. Since
RADIUS/1.1 does not use MD5, any obfuscated attributes will by
definition be transported as their underlying data type, "text"
([RFC8044] Section 3.4) or "string" ([RFC8044] Section 3.5).
New RADIUS specifications MUST NOT define attributes which can only
be transported via RADIUS over TLS. The RADIUS protocol has no way
to signal the security requirements of individual attributes. Any
existing implementation will handle these new attributes as "invalid
attributes" ([RFC6929] Section 2.8), and could forward them over an
insecure link. As RADIUS security and signalling is hop-by-hop,
there is no way for a RADIUS client or server to even know if such
forwarding is taking place. For these reasons and more, it is
therefore inappropriate to define new attributes which are only
secure if they use a secure transport layer.
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The result is that specifications do not need to mention this
transport profile, or make any special provisions for dealing with
it. This specification defines how RADIUS packet encoding, decoding,
signing, and verification are performed when using RADIUS/1.1. So
long as any future specification uses the existing encoding, etc.
schemes defined for RADIUS, no additional text in future documents is
necessary in order to be compatible with RADIUS/1.1.
We note that it is theoretically possible for future standards to
define new cryptographic primitives for use with RADIUS/UDP. In that
case, those documents would likely have to describe how to transport
that data in RADIUS/1.1. We believe that such standards are unlikely
to be published, as other efforts in the RADEXT working group are
forbidding such updates to RADIUS.
7. Implementation Status
(This section to be removed by the RFC editor.)
This specification is being implemented (client and server) in the
FreeRADIUS project which is hosted on GitHub at
https://github.com/FreeRADIUS/freeradius-server/tree/v3.2.x The code
implementation "diff" is approximately 1,000 lines, including build
system changes and changes to configuration parsers.
8. Privacy Considerations
This specification requires secure transport for RADIUS, and this has
all of the privacy benefits of RADIUS/TLS [RFC6614] and RADIUS/DTLS
[RFC7360]. All of the insecure uses of RADIUS have been removed.
9. Security Considerations
The primary focus of this document is addressing security
considerations for RADIUS.
10. IANA Considerations
IANA is requested to update the "TLS Application-Layer Protocol
Negotiation (ALPN) Protocol IDs" registry with one new entry:
Protocol: radius/1.1
Id. Sequence: 0x72 0x61 0x64 0x69 0x75 0x73 0x2f 0x31 0x2e 0x31
("radius/1.1")
Reference: This document
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11. Acknowledgements
In hindsight, the decision to retain MD5 for RADIUS over TLS was
likely wrong. It was an easy decision to make in the short term, but
it has caused ongoing problems which this document addresses.
Thanks to Bernard Aboba, Karri Huhtanen, Heikki Vatiainen, Alexander
Clouter, Michael Richardson, Hannes Tschofenig, Matthew Newton, and
Josh Howlett for reviews and feedback.
12. Changelog
draft-dekok-radext-sradius-00
Initial Revision
draft-dekok-radext-radiusv11-00
Use ALPN from RFC 7301, instead of defining a new port. Drop the
name "SRADIUS".
Add discussion of Original-Packet-Code
draft-dekok-radext-radiusv11-01
Update formatting.
draft-dekok-radext-radiusv11-02
Add Flag field and description.
Minor rearrangements and updates to text.
draft-dekok-radext-radiusv11-03
Remove Flag field and description based on feedback and expected
use-cases.
Use "radius/1.0" instead of "radius/1"
Consistently refer to the specification as "RADIUSv11", and
consistently quote the ALPN name as "radius/1.1"
Add discussion of future attributes and future crypto-agility
work.
draft-dekok-radext-radiusv11-04
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Remove "radius/1.0" as it is unnecessary.
Update Introduction with more historical background, which
motivates the rest of the section.
Change Identifier field to be reserved, as it is entirely unused.
Update discussion on clear text passwords.
Clarify discussion of Status-Server, User-Password, and Tunnel-
Password.
Give high level summary of ALPN, clear up client / server roles,
and remove "radius/1.0" as it is unnecessary.
Add text on RFC6421.
draft-dekok-radext-radiusv11-05
Clarify naming. "radius/1.1" is the ALPN name. "RADIUS/1.1" is
the transport profile.
Clarify that future specifications do not need to make provisions
for dealing with this transport profile.
draft-dekok-radext-radiusv11-05
Typos and word smithing.
Define and use "RADIUS over TLS" instead of RADIUS/(D)TLS.
Many cleanups and rework based on feedback from Matthew Newton.
draft-ietf-radext-radiusv11-00
No changes from previous draft.
draft-ietf-radext-radiusv11-01
Move to "experimental" based on WG feedback.
Many cleanups based on review from Matthew Newton
Removed requirement for supporting TLS-PSK.
This document does not deprecate new cryptographic work in RADIUS.
The "deprecating insecure transports" document does that.
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13. References
13.1. Normative References
[BCP14] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, DOI 10.17487/RFC2865, June 2000,
<https://www.rfc-editor.org/info/rfc2865>.
[RFC6421] Nelson, D., Ed., "Crypto-Agility Requirements for Remote
Authentication Dial-In User Service (RADIUS)", RFC 6421,
DOI 10.17487/RFC6421, November 2011,
<https://www.rfc-editor.org/info/rfc6421>.
[RFC6929] DeKok, A. and A. Lior, "Remote Authentication Dial In User
Service (RADIUS) Protocol Extensions", RFC 6929,
DOI 10.17487/RFC6929, April 2013,
<https://www.rfc-editor.org/info/rfc6929>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC8044] DeKok, A., "Data Types in RADIUS", RFC 8044,
DOI 10.17487/RFC8044, January 2017,
<https://www.rfc-editor.org/info/rfc8044>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
13.2. Informative References
[EDUROAM] eduroam, "eduroam", n.d., <https://eduroam.org>.
[OPENROAMING]
Alliance, W. B., "OpenRoaming: One global Wi-Fi network",
n.d., <https://wballiance.com/openroaming/>.
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Internet-Draft RADIUSv11 May 2023
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2548] Zorn, G., "Microsoft Vendor-specific RADIUS Attributes",
RFC 2548, DOI 10.17487/RFC2548, March 1999,
<https://www.rfc-editor.org/info/rfc2548>.
[RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866,
DOI 10.17487/RFC2866, June 2000,
<https://www.rfc-editor.org/info/rfc2866>.
[RFC2868] Zorn, G., Leifer, D., Rubens, A., Shriver, J., Holdrege,
M., and I. Goyret, "RADIUS Attributes for Tunnel Protocol
Support", RFC 2868, DOI 10.17487/RFC2868, June 2000,
<https://www.rfc-editor.org/info/rfc2868>.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", RFC 3579,
DOI 10.17487/RFC3579, September 2003,
<https://www.rfc-editor.org/info/rfc3579>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC5080] Nelson, D. and A. DeKok, "Common Remote Authentication
Dial In User Service (RADIUS) Implementation Issues and
Suggested Fixes", RFC 5080, DOI 10.17487/RFC5080, December
2007, <https://www.rfc-editor.org/info/rfc5080>.
[RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Aboba, "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", RFC 5176,
DOI 10.17487/RFC5176, January 2008,
<https://www.rfc-editor.org/info/rfc5176>.
[RFC5281] Funk, P. and S. Blake-Wilson, "Extensible Authentication
Protocol Tunneled Transport Layer Security Authenticated
Protocol Version 0 (EAP-TTLSv0)", RFC 5281,
DOI 10.17487/RFC5281, August 2008,
<https://www.rfc-editor.org/info/rfc5281>.
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Internet-Draft RADIUSv11 May 2023
[RFC5931] Harkins, D. and G. Zorn, "Extensible Authentication
Protocol (EAP) Authentication Using Only a Password",
RFC 5931, DOI 10.17487/RFC5931, August 2010,
<https://www.rfc-editor.org/info/rfc5931>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<https://www.rfc-editor.org/info/rfc6151>.
[RFC6218] Zorn, G., Zhang, T., Walker, J., and J. Salowey, "Cisco
Vendor-Specific RADIUS Attributes for the Delivery of
Keying Material", RFC 6218, DOI 10.17487/RFC6218, April
2011, <https://www.rfc-editor.org/info/rfc6218>.
[RFC6613] DeKok, A., "RADIUS over TCP", RFC 6613,
DOI 10.17487/RFC6613, May 2012,
<https://www.rfc-editor.org/info/rfc6613>.
[RFC6614] Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
"Transport Layer Security (TLS) Encryption for RADIUS",
RFC 6614, DOI 10.17487/RFC6614, May 2012,
<https://www.rfc-editor.org/info/rfc6614>.
[RFC7360] DeKok, A., "Datagram Transport Layer Security (DTLS) as a
Transport Layer for RADIUS", RFC 7360,
DOI 10.17487/RFC7360, September 2014,
<https://www.rfc-editor.org/info/rfc7360>.
[RFC7585] Winter, S. and M. McCauley, "Dynamic Peer Discovery for
RADIUS/TLS and RADIUS/DTLS Based on the Network Access
Identifier (NAI)", RFC 7585, DOI 10.17487/RFC7585, October
2015, <https://www.rfc-editor.org/info/rfc7585>.
[RFC7593] Wierenga, K., Winter, S., and T. Wolniewicz, "The eduroam
Architecture for Network Roaming", RFC 7593,
DOI 10.17487/RFC7593, September 2015,
<https://www.rfc-editor.org/info/rfc7593>.
[RFC7930] Hartman, S., "Larger Packets for RADIUS over TCP",
RFC 7930, DOI 10.17487/RFC7930, August 2016,
<https://www.rfc-editor.org/info/rfc7930>.
Author's Address
Alan DeKok
FreeRADIUS
Email: aland@freeradius.org
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