Request for Comments: 8044
Updates: 2865, 3162, 4072, 6158, 6572, 7268
Category: Standards Track
ISSN: 2070-1721
FreeRADIUS
January 2017
Data Types in RADIUS
Abstract
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RADIUS specifications have used data types for two decades without defining them as managed entities. During this time, RADIUS implementations have named the data types and have used them in attribute definitions. This document updates the specifications to better follow established practice. We do this by naming the data types defined in RFC 6158, which have been used since at least the publication of RFC 2865. We provide an IANA registry for the data types and update the "RADIUS Attribute Types" registry to include a Data Type field for each attribute. Finally, we recommend that authors of RADIUS specifications use these types in preference to existing practice. This document updates RFCs 2865, 3162, 4072, 6158, 6572, and 7268.
Status of This Memo
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This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc8044.
Copyright Notice
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Copyright © 2017 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 (http://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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Table of Contents
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1. Introduction ....................................................4 1.1. Specification Problems with Data Types .....................4 1.2. Implementation Problems with Data Types ....................5 1.3. No Mandated Changes ........................................5 1.4. Requirements Language ......................................5 2. Use of Data Types ...............................................6 2.1. Specification Use of Data Types ............................6 2.1.1. Field Names for Attribute Values ....................6 2.1.2. Attribute Definitions Using Data Types ..............7 2.1.3. Format of Attribute Definitions .....................8 2.1.4. Defining a New Data Type ............................9 2.2. Implementation Use of Data Types ...........................9 3. Data Type Definitions ..........................................10 3.1. integer ...................................................12 3.2. enum ......................................................12 3.3. time ......................................................13 3.4. text ......................................................14 3.5. string ....................................................15 3.6. concat ....................................................16 3.7. ifid ......................................................17 3.8. ipv4addr ..................................................18 3.9. ipv6addr ..................................................18 3.10. ipv6prefix ...............................................19 3.11. ipv4prefix ...............................................20 3.12. integer64 ................................................22 3.13. tlv ......................................................23 3.14. vsa ......................................................24 3.15. extended .................................................26 3.16. long-extended ............................................27 3.17. evs ......................................................30 4. Updated Registries .............................................31 4.1. New "Data Type" Registry ..................................31 4.2. Updates to the "RADIUS Attribute Types" Registry ..........32 5. Security Considerations ........................................32 6. IANA Considerations ............................................33 7. References .....................................................33 7.1. Normative References ......................................33 7.2. Informative References ....................................34 Acknowledgments ...................................................35 Author's Address ..................................................35
1. Introduction
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RADIUS specifications have historically defined attributes in terms of name, value, and data type. Of these three pieces of information, the name is recorded by IANA in the "RADIUS Attribute Types" registry but is not otherwise managed or restricted, as discussed in [RFC6929], Section 2.7.1. The value is managed by IANA and recorded in that registry. The data type is not managed or recorded in the "RADIUS Attribute Types" registry. Experience has shown that there is a need to create well-known data types and have them managed by IANA.
This document defines an IANA RADIUS "Data Type" registry and updates the "RADIUS Attribute Types" registry to use those newly defined data types. It recommends how both specifications and implementations should use the data types. It extends the "RADIUS Attribute Types" registry to have a data type for each assigned attribute.
In this section, we review the use of data types in specifications and implementations. We highlight ambiguities and inconsistencies. The rest of this document is devoted to resolving those problems.
1.1. Specification Problems with Data Types
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When attributes are defined in the specifications, the terms "Value" and "String" are used to refer to the contents of an attribute. However, these names are used recursively and inconsistently. We suggest that defining a field to recursively contain itself is problematic.
A number of data type names and definitions are given in [RFC2865], Section 5, at the bottom of page 25. These data types are named and clearly defined. However, this practice was not continued in later specifications.
Specifically, [RFC2865] defines attributes of data type "address" to carry IPv4 addresses. Despite this definition, [RFC3162] defines attributes of data type "Address" to carry IPv6 addresses. We suggest that the use of the word "address" to refer to disparate data types is problematic.
Other failures are that [RFC3162] does not give a data type name and definition for the data types IPv6 address, Interface-Id, or IPv6 prefix. [RFC2869] defines Event-Timestamp to carry a time but does not reuse the "time" data type defined in [RFC2865]. Instead, it just repeats the "time" definition. [RFC6572] defines multiple attributes that carry IPv4 prefixes. However, an "IPv4 prefix" data type is not named, defined as a data type, or called out as an addition to RADIUS. Further, [RFC6572] does not follow the recommendations of [RFC6158] and does not explain why it fails to follow those recommendations.
These ambiguities and inconsistencies need to be resolved.
1.2. Implementation Problems with Data Types
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RADIUS implementations often use "dictionaries" to map attribute names to type values and define data types for each attribute. The data types in the dictionaries are defined by each implementation but correspond to the "ad hoc" data types used in the specifications.
In effect, implementations have seen the need for well-defined data types and have created them. It is time for RADIUS specifications to follow this practice.
1.3. No Mandated Changes
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This document mandates no changes to any past, present, or future RADIUS implementation. It instead documents existing practice in order to simplify the process of writing RADIUS specifications, clarify the interpretation of RADIUS standards, and improve the communication between specification authors and IANA.
This document suggests that implementations SHOULD use the data types defined here, in preference to any ad hoc data types currently in use. This suggestion should have a minimal effect on implementations, as most ad hoc data types are compatible with the ones defined here. Any difference will typically be limited to the name of the data type.
This document updates [RFC6158] to permit the data types defined in the "Data Type" registry as "basic data types", as per Section 2.1 of [RFC6158]. The recommendations of [RFC6158] are otherwise unchanged.
1.4. Requirements Language
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
2. Use of Data Types
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The data types can be used in two places: specifications and implementations. This section discusses both uses and gives guidance on using the data types.
2.1. Specification Use of Data Types
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In this section, we give recommendations for how specifications should be written using data types. We first describe how attribute field names can be consistently named. We then describe how attribute definitions should use the data types and deprecate the use of "ASCII art" for attribute definitions. We suggest a format for new attribute definitions. This format includes recommended fields and suggestions for how those fields should be described.
Finally, we make recommendations for how new data types should be defined.
2.1.1. Field Names for Attribute Values
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Previous specifications used inconsistent and conflicting names for the contents of RADIUS attributes. For example, the term "Value" is used in [RFC2865], Section 5 to define a field that carries the contents of an attribute. It is then used in later sections as the subfield of attribute contents. The result is that the field is defined as recursively containing itself. Similarly, "String" is used both as a data type and as a subfield of other data types.
We correct this ambiguity by using context-specific names for various fields of attributes and data types. It then becomes clear that, for example, a field called "VSA-Data" must contain different data than a field called "EVS-Data". Each new name is defined where it is used.
We also define the following term:
Attr-Data
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The Value field of an Attribute as defined in [RFC2865], Section 5. The contents of this field MUST be of a valid data type as defined in the RADIUS "Data Type" registry.
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We consistently use "Attr-Data" to refer to the contents of an attribute, instead of the more ambiguous name "Value". It is RECOMMENDED that new specifications follow this practice.
We consistently use "Value" to refer to the contents of a data type, where that data type is simple. For example, an "integer" can have a "Value". In contrast, a Vendor-Specific Attribute carries complex information and thus cannot have a "Value".
For data types that carry complex information, we name the fields based on the data type. For example, a Vendor-Specific Attribute is defined to carry a "vsa" data type, and the contents of that data type are described herein as "VSA-Data".
These terms are used in preference to the term "String", which was previously used in ambiguous ways. It is RECOMMENDED that future specifications use type-specific names and the same naming scheme for new types. This use will maintain consistent definitions and help to avoid ambiguities.
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2.1.2. Attribute Definitions Using Data Types
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New RADIUS specifications MUST define attributes using data types from the RADIUS "Data Type" registry. The specification may, of course, define a new data type, update the "Data Type" registry, and use the new data type, all in the same document. The guidelines given in [RFC6929] MUST be followed when defining a new data type.
Attributes can usually be completely described via the Attribute Type value, name, and data type. The use of ASCII art is then limited only to the definition of new data types and for complex data types.
Use of the new extended attributes [RFC6929] makes ASCII art even more problematic. An attribute can be allocated from any of the extended spaces, with more than one option for the attribute header format. This allocation decision is made after the specification has been accepted for publication. As the allocation affects the format of the attribute header, it is essentially impossible to create the correct ASCII art prior to final publication. Allocation from the different spaces also changes the value of the Length field, making it difficult to define it correctly prior to final publication of the document.
It is therefore RECOMMENDED that ASCII art diagrams not be used for new RADIUS attribute specifications.
2.1.3. Format of Attribute Definitions
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When defining a new attribute, the following fields SHOULD be given:
Description
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A description of the meaning and interpretation of the attribute.
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Type
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The Attribute Type value, given in the "dotted number" notation from [RFC6929]. Specifications can often leave this as "TBD" (to be determined) and request that IANA fill in the allocated values.
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Length
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A description of the length of the attribute. For attributes of variable length, a maximum length SHOULD be given. Since the Length value may depend on the Type value, the definition of Length may be affected by IANA allocations.
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Data Type
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One of the named data types from the RADIUS "Data Type" registry.
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Value
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A description of any attribute-specific limitations on the values carried by the specified data type. If there are no attribute-specific limitations, then the description of this field can be omitted, so long as the Description field is sufficiently explanatory.
Where the values are limited to a subset of the possible range, valid range(s) MUST be defined.
For attributes of data type "enum", a list of enumerated values and names MUST be given, as shown in [RFC2865], Section 5.6.
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Using a consistent format for attribute definitions helps to make the definitions clearer.
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2.1.4. Defining a New Data Type
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When a specification needs to define a new data type, it SHOULD follow the format used by the definitions in Section 3 of this document. The text at the start of the data type definition MUST describe the data type, including the expected use, and why a new data type is required. That text SHOULD include limits on expected values and why those limits exist. The fields "Name", "Value", "Length", and "Format" MUST be given, along with values.
The Name field SHOULD be a single name, all lowercase.
Contractions such as "ipv4addr" are RECOMMENDED where they add clarity.
We note that the use of "Value" in the RADIUS "Data Type" registry can be confusing. That name is also used in attribute definitions, but with a different meaning. We trust that the meaning here is clear from the context.
The Value field SHOULD be given as "TBD" in specifications. That number is assigned by IANA.
The Format field SHOULD be defined with ASCII art in order to have a precise definition. Machine-readable formats are also RECOMMENDED.
The definition of a new data type should be done only when absolutely necessary. We do not expect a need for a large number of new data types. When defining a new data type, the guidelines of [RFC6929] with respect to data types MUST be followed.
It is RECOMMENDED that vendors not define "vendor-specific" data types. As discussed in [RFC6929], those data types are rarely necessary and can cause interoperability problems.
Any new data type MUST have a unique name in the RADIUS "Data Type" registry. The number of the data type will be assigned by IANA.
2.2. Implementation Use of Data Types
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Implementations not supporting a particular data type MUST treat attributes of that data type as being of data type "string", as defined in Section 3.5. It is RECOMMENDED that such attributes be treated as "invalid attributes", as defined in [RFC6929], Section 2.8.
Where the contents of a data type do not match the definition, implementations MUST treat the enclosing attribute as being an invalid attribute. This requirement includes, but is not limited to, the following situations:
- Attributes with values outside of the allowed range(s) for the data type, e.g., as given in the data types "integer", "ipv4addr", "ipv6addr", "ipv4prefix", "ipv6prefix", or "enum".
- "text" attributes where the contents do not match the required format.
- Attributes where the length is shorter or longer than the allowed length(s) for the given data type.
The requirements for Reserved fields are more difficult to quantify. Implementations SHOULD be able to receive and process attributes where Reserved fields are non-zero. We do not, however, define any "correct" processing of such attributes. Instead, specifications that define one or more new meanings for Reserved fields SHOULD describe how each new meaning is compatible with older implementations. We expect that such descriptions are derived from practical experience with implementations. Implementations MUST set Reserved fields to zero when creating attributes.
3. Data Type Definitions
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This section defines the new data types. For each data type, it gives a definition, a name, a number, a length, and an encoding format. Where relevant, it describes subfields contained within the data type. These definitions have no impact on existing RADIUS implementations. There is no requirement that implementations use these names.
Where possible, the name of each data type has been taken from previous specifications. In some cases, a different name has been chosen. The change of name is sometimes required to avoid ambiguity (i.e., "address" versus "Address"). Otherwise, the new name has been chosen to be compatible with [RFC2865] or with usage in common implementations. In some cases, new names are chosen to clarify the interpretation of the data type.
The numbers assigned herein for the data types have no meaning other than to permit them to be tracked by IANA. As RADIUS does not encode information about data types in a packet, the numbers assigned to a data type will never occur in a packet. It is RECOMMENDED that new implementations use the names defined in this document in order to avoid confusion. Existing implementations may choose to use the names defined here, but that is not required.
The encoding of each data type is taken from previous specifications. The fields are transmitted from left to right.
Where the data types have interdependencies, the simplest data type is given first, and dependent ones are given later.
We do not create specific data types for the "tagged" attributes (i.e., attributes containing a Tag field) defined in [RFC2868]. That specification defines the tagged attributes as being backwards compatible with pre-existing data types. In addition, [RFC6158], Section 2.1 says that tagged attributes should not be used. There is therefore no benefit to defining additional data types for these attributes. We trust that implementors will be aware that tagged attributes must be treated differently from non-tagged attributes of the same data type.
Similarly, we do not create data types for some attributes having a complex structure, such as CHAP-Password, ARAP-Features, or Location-Information. ("CHAP" refers to the Challenge Handshake Authentication Protocol, and "ARAP" refers to the Apple Remote Access Protocol.) We need to strike a balance between correcting earlier mistakes and making this document more complex. In some cases, it is better to treat complex attributes as being of type "string", even though they need to be interpreted by RADIUS implementations. The guidelines given in Section 6.3 of [RFC6929] were used to make this determination.
3.1. integer
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The "integer" data type encodes a 32-bit unsigned integer in network byte order. Where the range of values for a particular attribute is limited to a subset of the values, specifications MUST define the valid range. Attributes with Values outside of the allowed ranges SHOULD be treated as invalid attributes.
Name integer ValueLength Four octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2. enum
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The "enum" data type encodes a 32-bit unsigned integer in network byte order. It differs from the "integer" data type only in that it is used to define enumerated types, such as Service-Type (Section 5.6 of [RFC2865]). Specifications MUST define a valid set of enumerated values, along with a unique name for each value. Attributes with Values outside of the allowed enumerations SHOULD be treated as invalid attributes.
Name enum ValueLength Four octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3. time
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The "time" data type encodes time as a 32-bit unsigned value in network byte order and in seconds since 00:00:00 UTC, January 1, 1970. We note that dates before the year 2017 are likely to indicate configuration errors or lack of access to the correct time.
Note that the "time" attribute is defined to be unsigned, which means that it is not subject to a signed integer overflow in the year 2038.
Name time ValueLength Four octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.4. text
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The "text" data type encodes UTF-8 text [RFC3629]. The maximum length of the text is given by the encapsulating attribute. Where the range of lengths for a particular attribute is limited to a subset of possible lengths, specifications MUST define the valid range(s). Attributes with lengths outside of the allowed values SHOULD be treated as invalid attributes.
Attributes of type "text" that are allocated in the standard space (Section 1.2 of [RFC6929]) are limited to no more than 253 octets of data. Attributes of type "text" that are allocated in the extended space can be longer. In both cases, these limits are reduced when the data is encapsulated inside of another attribute.
Where the text is intended to carry data in a particular format (e.g., Framed-Route), the format MUST be given. The specification SHOULD describe the format in a machine-readable way, such as via the Augmented Backus-Naur Form (ABNF) [RFC5234]. Attributes with Values not matching the defined format SHOULD be treated as invalid attributes.
Note that the "text" data type does not terminate with a NUL octet (hex 00). The Attribute has a Length field and does not use a terminator. Texts of length zero (0) MUST NOT be sent; omit the entire attribute instead.
Name text ValueLength
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One or more octets
Format 0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+- | Value ... +-+-+-+-+-+-+-+- -
3.5. string
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The "string" data type encodes binary data as a sequence of undistinguished octets. Where the range of lengths for a particular attribute is limited to a subset of possible lengths, specifications MUST define the valid range(s). Attributes with lengths outside of the allowed values SHOULD be treated as invalid attributes.
Attributes of type "string" that are allocated in the standard space (Section 1.2 of [RFC6929]) are limited to no more than 253 octets of data. Attributes of type "string" that are allocated in the extended space can be longer. In both cases, these limits are reduced when the data is encapsulated inside of another attribute.
Note that the "string" data type does not terminate with a NUL octet (hex 00). The Attribute has a Length field and does not use a terminator. Strings of length zero (0) MUST NOT be sent; omit the entire attribute instead. Where there is a need to encapsulate complex data structures and TLVs cannot be used, the "string" data type MUST be used. This requirement includes encapsulation of data structures defined outside of RADIUS that are opaque to the RADIUS infrastructure. It also includes encapsulation of some data structures that are not opaque to RADIUS, such as the contents of CHAP-Password.
There is little reason to define a new RADIUS data type for only one attribute. However, where the complex data type cannot be represented as TLVs and is expected to be used in many attributes, a new data type SHOULD be defined.
These requirements are stronger than [RFC6158], which makes the above encapsulation a "SHOULD". This document defines data types for use in RADIUS, so there are few reasons to avoid using them.
Name string ValueLength
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One or more octets
Format 0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+- | Octets ... +-+-+-+-+-+-+-+- -
3.6. concat
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The "concat" data type permits the transport of more than 253 octets of data in a "standard space" [RFC6929] attribute. It is otherwise identical to the "string" data type.
If multiple attributes of this data type are contained in a packet, all attributes of the same type code MUST be in order, and they MUST be consecutive attributes in the packet.
The amount of data transported in a "concat" data type can be no more than the RADIUS packet size. In practice, the requirement to transport multiple attributes means that the limit may be substantially smaller than one RADIUS packet. As a rough guide, it is RECOMMENDED that this data type transport no more than 2048 octets of data.
The "concat" data type MAY be used for "standard space" attributes. It MUST NOT be used for attributes in the "short extended space" or the "long extended space". It MUST NOT be used in any field or subfields of the following data types: "tlv", "vsa", "extended", "long-extended", or "evs".
Name concat ValueLength
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One or more octets
Format 0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+- | Octets ... +-+-+-+-+-+-+-+- -
3.7. ifid
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The "ifid" data type encodes an Interface-Id as an 8-octet IPv6 Interface Identifier in network byte order.
Name ifid ValueLength Eight octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface-Id ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Interface-Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.8. ipv4addr
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The "ipv4addr" data type encodes an IPv4 address in network byte order. Where the range of addresses for a particular attribute is limited to a subset of possible addresses, specifications MUST define the valid range(s). Attributes with Address values outside of the allowed range(s) SHOULD be treated as invalid attributes.
Name ipv4addr ValueLength Four octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.9. ipv6addr
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The "ipv6addr" data type encodes an IPv6 address in network byte order. Where the range of addresses for a particular attribute is limited to a subset of possible addresses, specifications MUST define the valid range(s). Attributes with Address values outside of the allowed range(s) SHOULD be treated as invalid attributes.
Name ipv6addr ValueLength Sixteen octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Address ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Address ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.10. ipv6prefix
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The "ipv6prefix" data type encodes an IPv6 prefix, using both a prefix length and an IPv6 address in network byte order. Where the range of prefixes for a particular attribute is limited to a subset of possible prefixes, specifications MUST define the valid range(s). Attributes with Address values outside of the allowed range(s) SHOULD be treated as invalid attributes.
Attributes with a Prefix-Length field having a value greater than 128 MUST be treated as invalid attributes.
Name ipv6prefix ValueLength
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At least two, and no more than eighteen, octets
Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix-Length | Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Reserved-
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This field, which is reserved and MUST be present, is always set to zero. This field is one octet in length.
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Prefix-Length
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The length of the prefix, in bits. At least 0 and no larger than 128. This field is one octet in length.
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Prefix
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-
The Prefix field is up to 16 octets in length. Bits outside of the Prefix-Length, if included, MUST be zero.
The Prefix field SHOULD NOT contain more octets than necessary to encode the Prefix field.
-
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3.11. ipv4prefix
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The "ipv4prefix" data type encodes an IPv4 prefix, using both a prefix length and an IPv4 address in network byte order. Where the range of prefixes for a particular attribute is limited to a subset of possible prefixes, specifications MUST define the valid range(s). Attributes with Address values outside of the allowed range(s) SHOULD be treated as invalid attributes.
Attributes with a Prefix-Length field having a value greater than 32 MUST be treated as invalid attributes.
Name ipv4prefix ValueLength Six octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix-Length | Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Reserved-
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This field, which is reserved and MUST be present, is always set to zero. This field is one octet in length.
Note that this definition differs from that given in [RFC6572]. See "Prefix-Length", below, for an explanation.
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Prefix-Length
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The length of the prefix, in bits. The values MUST be no
larger than 32. This field is one octet in length. Note that
this definition differs from that given in [RFC6572].
-
-
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As compared to [RFC6572], the Prefix-Length field has increased in size by two bits, both of which must be zero. The Reserved field has decreased in size by two bits. The result is that both fields are aligned on octet boundaries, which removes the need for bit masking of the fields.
Since [RFC6572] required the Reserved field to be zero, the definition here is compatible with the definition in the original specification.
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Prefix
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The Prefix field is 4 octets in length. Bits outside of the Prefix-Length MUST be zero. Unlike the "ipv6prefix" data type, this field is fixed length. If the address is all zeros (i.e., "0.0.0.0"), then the Prefix-Length MUST be set to 32.
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3.12. integer64
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The "integer64" data type encodes a 64-bit unsigned integer in network byte order. Where the range of values for a particular attribute is limited to a subset of the values, specifications MUST define the valid range(s). Attributes with Values outside of the allowed range(s) SHOULD be treated as invalid attributes.
Name integer64 ValueLength Eight octets Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.13. tlv
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The "tlv" data type encodes a Type-Length-Value, as defined in [RFC6929], Section 2.3.
Name tlv ValueLength
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Three or more octets
Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV-Type | TLV-Length | TLV-Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields TLV-Type-
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This field is one octet. Up-to-date values of this field are specified according to the policies and rules described in [RFC6929], Section 10. Values of 254-255 are reserved for use by future extensions to RADIUS. The value 26 has no special meaning and MUST NOT be treated as a Vendor-Specific Attribute.
The TLV-Type is meaningful only within the context defined by Type fields of the encapsulating Attributes, using the dotted-number notation introduced in [RFC6929].
A RADIUS server MAY ignore Attributes with an unknown "TLV-Type".
A RADIUS client MAY ignore Attributes with an unknown "TLV-Type".
A RADIUS proxy SHOULD forward Attributes with an unknown "TLV-Type" verbatim.
-
TLV-Length
-
-
The TLV-Length field is one octet and indicates the length of this TLV, including the TLV-Type, TLV-Length, and TLV-Value fields. It MUST have a value between 3 and 255. If a client or server receives a TLV with an invalid TLV-Length, then the attribute that encapsulates that TLV MUST be considered to be an invalid attribute and is handled as per [RFC6929], Section 2.8.
TLVs having a TLV-Length of two (2) MUST NOT be sent; omit the entire TLV instead.
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TLV-Data
-
-
The TLV-Data field is one or more octets and contains information specific to the attribute. The format and length of the TLV-Data field are determined by the TLV-Type and TLV-Length fields.
The TLV-Data field MUST contain only known RADIUS data types. The TLV-Data field MUST NOT contain any of the following data types: "concat", "vsa", "extended", "long-extended", or "evs".
-
-
3.14. vsa
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The "vsa" data type encodes vendor-specific data, as given in [RFC2865], Section 5.26. It is used only in the Attr-Data field of a Vendor-Specific Attribute. It MUST NOT appear in the contents of any other data type.
Where an implementation determines that an attribute of data type "vsa" contains data that does not match the expected format, it SHOULD treat that attribute as being an invalid attribute.
Name vsa ValueLength
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Five or more octets
Format 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-Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | VSA-Data .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Vendor-Id-
-
The 4 octets are the Network Management Private Enterprise Code [PEN] of the vendor in network byte order.
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VSA-Data
-
-
The VSA-Data field is one or more octets. The actual format of the information is site specific or application specific, and a robust implementation SHOULD support the field as undistinguished octets.
The codification of the range of allowed usage of this field is outside the scope of this specification.
The "vsa" data type SHOULD contain a sequence of "tlv" data types. The interpretation of the TLV-Type and TLV-Data fields is dependent on the vendor's definition of that attribute.
The "vsa" data type MUST be used as the contents of the Attr-Data field of the Vendor-Specific Attribute. The "vsa" data type MUST NOT appear in the contents of any other data type.
-
-
3.15. extended
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The "extended" data type encodes the "Extended Type" format, as given in [RFC6929], Section 2.1. It is used only in the Attr-Data field of an attribute allocated from the standard space. It MUST NOT appear in the contents of any other data type.
Name extended ValueLength
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Two or more octets
Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended-Type | Ext-Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Extended-Type-
-
The Extended-Type field is one octet. Up-to-date values of this field are specified according to the policies and rules described in [RFC6929], Section 10. Unlike the Type field defined in [RFC2865], Section 5, no values are allocated for experimental or implementation-specific use. Values 241-255 are reserved and MUST NOT be used.
The Extended-Type is meaningful only within a context defined by the Type field. That is, this field may be thought of as defining a new type space of the form "Type.Extended-Type". See [RFC6929], Section 2.1 for additional discussion.
A RADIUS server MAY ignore Attributes with an unknown "Type.Extended-Type".
A RADIUS client MAY ignore Attributes with an unknown "Type.Extended-Type".
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Ext-Data
-
-
The Ext-Data field is one or more octets.
The contents of this field MUST be a valid data type as defined in the RADIUS "Data Type" registry. The Ext-Data field MUST NOT contain any of the following data types: "concat", "vsa", "extended", "long-extended", or "evs".
-
-
Implementations supporting this specification MUST use the
Identifier of "Type.Extended-Type" to determine the
interpretation of the Ext-Data field.
3.16. long-extended
-
The "long-extended" data type encodes the "Long Extended Type" format, as given in [RFC6929], Section 2.2. It is used only in the Attr-Data field of an attribute. It MUST NOT appear in the contents of any other data type.
Name long-extended ValueLength
-
Three or more octets
Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended-Type |M|T| Reserved | Ext-Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Extended-Type-
-
This field is identical to the Extended-Type field defined above in Section 3.15.
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M (More)
-
-
The More field (M flag) is one (1) bit in length and indicates whether or not the current attribute contains "more" than 251 octets of data. The More field MUST be clear (0) if the Length field has a value less than 255. The More field MAY be set (1) if the Length field has a value of 255.
If the More field is set (1), it indicates that the Ext-Data field has been fragmented across multiple RADIUS attributes.
When the More field is set (1), the Attribute MUST have a Length field value of 255; there MUST be an attribute following this one; and the next attribute MUST have both the same Type and Extended-Type. That is, multiple fragments of the same value MUST be in order and MUST be consecutive attributes in the packet, and the last attribute in a packet MUST NOT have the More field set (1).
That is, a packet containing a fragmented attribute needs to contain all fragments of the attribute, and those fragments need to be contiguous in the packet. RADIUS does not support inter-packet fragmentation, which means that fragmenting an attribute across multiple packets is impossible.
If a client or server receives an attribute fragment with the More field set (1), but for which no subsequent fragment can be found, then the fragmented attribute is considered to be an invalid attribute and is handled as per [RFC6929], Section 2.8.
-
T (Truncation)
-
-
This field is one bit in size and is called "T" for Truncation. It indicates that the attribute is intentionally truncated in this chunk and is to be continued in the next chunk of the sequence. The combination of the M flag and the T flag indicates that the attribute is fragmented (M flag) but that all of the fragments are not available in this chunk (T flag). Proxies implementing [RFC6929] will see these attributes as invalid (they will not be able to reconstruct them), but they will still forward them, as Section 5.2 of [RFC6929] indicates that they SHOULD forward unknown attributes anyway.
Please see [RFC7499] for further discussion of the uses of this flag.
-
Reserved
-
-
This field is six bits long and is reserved for future use. Implementations MUST set it to zero (0) when encoding an attribute for sending in a packet. The contents SHOULD be ignored on reception.
Future specifications may define one or more additional meanings for this field. Implementations therefore MUST NOT treat this field as invalid if it is non-zero.
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Ext-Data
-
-
The Ext-Data field is one or more octets.
The contents of this field MUST be a valid data type as defined in the RADIUS "Data Type" registry. The Ext-Data field MUST NOT contain any of the following data types: "concat", "vsa", "extended", "long-extended", or "evs".
-
-
Implementations supporting this specification MUST use the
Identifier of "Type.Extended-Type" to determine the
interpretation of the Ext-Data field.
-
-
-
The length of the data MUST be taken as the sum of the lengths of the fragments (i.e., Ext-Data fields) from which it is constructed. Any interpretation of the resulting data MUST occur after the fragments have been reassembled. If the reassembled data does not match the expected format, each fragment MUST be treated as an invalid attribute, and the reassembled data MUST be discarded.
We note that the maximum size of a fragmented attribute is limited only by the RADIUS packet length limitation. Implementations MUST be able to handle the case where one fragmented attribute completely fills the packet.
-
-
3.17. evs
-
The "evs" data type encodes an Extended-Vendor-Specific Attribute, as given in [RFC6929], Section 2.4. The "evs" data type is used solely to extend the vendor-specific space. It MAY appear inside of an "extended" data type or a "long-extended" data type. It MUST NOT appear in the contents of any other data type.
Where an implementation determines that an attribute of data type "evs" contains data that does not match the expected format, it SHOULD treat that attribute as being an invalid attribute.
Name evs ValueLength
-
Six or more octets
Format 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-Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-Type | EVS-Data .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Subfields Vendor-Id-
-
The 4 octets are the Network Management Private Enterprise Code [PEN] of the vendor in network byte order.
-
Vendor-Type
-
-
The Vendor-Type field is one octet. Values are assigned at the sole discretion of the vendor.
-
EVS-Data
-
-
The EVS-Data field is one or more octets. It SHOULD encapsulate a previously defined RADIUS data type. Non-standard data types SHOULD NOT be used. We note that the EVS-Data field may be of data type "tlv".
The actual format of the information is site specific or application specific, and a robust implementation SHOULD support the field as undistinguished octets. We recognize that vendors have complete control over the contents and format of the Ext-Data field; at the same time, we recommend that good practices be followed.
-
-
Further codification of the range of allowed usage of this
field is outside the scope of this specification.
4. Updated Registries
-
This section defines a new IANA registry for RADIUS data types and then updates the existing "RADIUS Attribute Types" registry to use the data types from the new registry.
4.1. New "Data Type" Registry
-
This section defines a new registry located under "RADIUS Types", called "Data Type". The registration procedures for the "Data Type" registry are "Standards Action" [RFC5226].
The "Data Type" registry contains three columns of data, as follows.
Value
-
The number of the data type. The Value field is an artifact of the registry and has no on-the-wire meaning.
Description
-
The name of the data type. This field is used only for the registry and has no on-the-wire meaning.
Reference
-
The specification where the data type was defined.
The initial contents of the registry are as follows.
Value Description Reference ----- ----------- ------------------- 1 integer [RFC2865], RFC 8044 2 enum [RFC2865], RFC 8044 3 time [RFC2865], RFC 8044 4 text [RFC2865], RFC 8044 5 string [RFC2865], RFC 8044 6 concat RFC 8044 7 ifid [RFC3162], RFC 8044 8 ipv4addr [RFC2865], RFC 8044 9 ipv6addr [RFC3162], RFC 8044 10 ipv6prefix [RFC3162], RFC 8044 11 ipv4prefix [RFC6572], RFC 8044 12 integer64 [RFC6929], RFC 8044 13 tlv [RFC6929], RFC 8044 14 vsa [RFC2865], RFC 8044 15 extended [RFC6929], RFC 8044 16 long-extended [RFC6929], RFC 8044 17 evs [RFC6929], RFC 8044 -
4.2. Updates to the "RADIUS Attribute Types" Registry
-
This section updates the "RADIUS Attribute Types" registry to have a new column, which is inserted between the existing "Description" and "Reference" columns. The new column is named "Data Type". The contents of that column are the name of a data type, corresponding to the attribute in that row, or blank if the Attribute Type is unassigned. The name of the data type is taken from the RADIUS "Data Type" registry, as defined above.
The existing registration requirements for the "RADIUS Attribute Types" registry are otherwise unchanged.
5. Security Considerations
-
This specification is concerned solely with updates to IANA registries. As such, there are no security considerations with the document itself.
However, the use of inconsistent names and poorly defined entities in a protocol is problematic. Inconsistencies in specifications can lead to security and interoperability problems in implementations. Further, having one canonical source for the definition of data types means that an implementor has fewer specifications to read. The implementation work is therefore simpler and more likely to be correct.
The goal of this specification is to reduce ambiguities in the RADIUS protocol, which we believe will lead to more robust and more secure implementations.
6. IANA Considerations
-
IANA has created one new registry, as described in Section 4.1.
IANA has updated the "RADIUS Attribute Types" registry, as described in Section 4.2.
IANA requires that all allocation requests in the "RADIUS Attribute Types" registry contain a Data Type field, which is required to contain one of the "Data Type" names contained in the RADIUS "Data Type" registry.
IANA requires that updates to the RADIUS "Data Type" registry contain the following fields, with the associated instructions:
- Value. IANA is instructed to assign the next unused integer in sequence to new data type definitions.
- Name. IANA is instructed to require that this name be unique in the registry.
- Reference. IANA is instructed to update this field with a reference to the document that defines the data type.
7. References
7.1. Normative References
-
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://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, <http://www.rfc-editor.org/info/rfc2865>. [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", RFC 3162, DOI 10.17487/RFC3162, August 2001, <http://www.rfc-editor.org/info/rfc3162>. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, <http://www.rfc-editor.org/info/rfc3629>. [RFC4072] Eronen, P., Ed., Hiller, T., and G. Zorn, "Diameter Extensible Authentication Protocol (EAP) Application", RFC 4072, DOI 10.17487/RFC4072, August 2005, <http://www.rfc-editor.org/info/rfc4072>. [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, <http://www.rfc-editor.org/info/rfc5234>. [RFC6158] DeKok, A., Ed., and G. Weber, "RADIUS Design Guidelines", BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011, <http://www.rfc-editor.org/info/rfc6158>. [RFC6572] Xia, F., Sarikaya, B., Korhonen, J., Ed., Gundavelli, S., and D. Damic, "RADIUS Support for Proxy Mobile IPv6", RFC 6572, DOI 10.17487/RFC6572, June 2012, <http://www.rfc-editor.org/info/rfc6572>. [RFC7499] Perez-Mendez, A., Ed., Marin-Lopez, R., Pereniguez-Garcia, F., Lopez-Millan, G., Lopez, D., and A. DeKok, "Support of Fragmentation of RADIUS Packets", RFC 7499, DOI 10.17487/RFC7499, April 2015, <http://www.rfc-editor.org/info/rfc7499>.
7.2. Informative References
-
[PEN] IANA, "PRIVATE ENTERPRISE NUMBERS", <http://www.iana.org/assignments/enterprise-numbers/>. [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, <http://www.rfc-editor.org/info/rfc2868>. [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS Extensions", RFC 2869, DOI 10.17487/RFC2869, June 2000, <http://www.rfc-editor.org/info/rfc2869>. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>. [RFC6929] DeKok, A. and A. Lior, "Remote Authentication Dial In User Service (RADIUS) Protocol Extensions", RFC 6929, DOI 10.17487/RFC6929, April 2013, <http://www.rfc-editor.org/info/rfc6929>. [RFC7268] Aboba, B., Malinen, J., Congdon, P., Salowey, J., and M. Jones, "RADIUS Attributes for IEEE 802 Networks", RFC 7268, DOI 10.17487/RFC7268, July 2014, <http://www.rfc-editor.org/info/rfc7268>.
Acknowledgments
-
Thanks to the RADEXT WG participants for their patience and reviews of this document.
Author's Address
-
Alan DeKok
The FreeRADIUS Server ProjectEmail:
aland@freeradius.org