Additional Media Type Structured Syntax Suffixes
draft-ietf-appsawg-media-type-suffix-regs-03
A content media type name sometimes includes partitioned meta-information distinguish by a Structured Syntax, to permit noting an attribute of the media as a suffix to the name. This document defines several Structured Syntax Suffixes for use with media type registrations. In particular, it defines and registers the "+json", "+ber", "+der", "+fastinfoset", "+wbxml" and "+zip" Structured Syntax Suffixes, and updates the "+xml" Message Type Structured Syntax Suffix registration.
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1. Introduction
[RFC3023] created the +xml suffix convention that can be used when defining names for media types whose representation uses XML underneath. That is, they could have been successfully parsed as if the media type had been application/xml in addition to their being parsed as their media type that is using the +xml suffix. [I-D.ietf-appsawg-media-type-regs] defines the Message Type Structured Syntax Suffixes registry to be used for such Structured Syntax Suffixes.
A variety of Structured Syntax Suffixes have already been used in some media type registrations, in particular "+json", "+der", "+fastinfoset" and "+wbxml". This document defines and registers these Structured Syntax Suffixes in the Structured Syntax Suffix registry, along with "+ber" and "+zip". In addition, this document updates the "+xml" Structured Syntax Suffix registration.
Discussion of this document should occur in the Apps Area Working Group (apps-discuss@ietf.org). [RFC Editor note: remove this paragraph.]
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. When to Use these Structured Syntax Suffixes
Each of the Structured Syntax Suffixes defined in this document is appropriate for use when the media type identifies the semantics of the protocol payload. That is, knowing the semantics of the specific media type provides for more specific processing of the content than that afforded by generic processing of the underlying representation.
At the same time, using the suffix allows receivers of the media types to do generic processing of the underlying representation in cases where
- they do not need to perform special handling of the particular semantics of the exact media type, and,
- there is no special knowledge needed by such a generic processor in order to parse that underlying representation other than what would be needed to parse any example of that underlying representation.
3. Initial Structured Syntax Suffix Definitions
[RFC4627] defines the "application/json" media type. The suffix "+json" MAY be used with any media type whose representation follows that established for "application/json". The Message Type Structured Syntax Suffix registration form follows. See [I-D.ietf-appsawg-media-type-regs] for definitions of each of the registration form headings.
- Name:
- JavaScript Object Notation (JSON)
- +suffix:
- +json
- References:
-
[RFC4627]
- Encoding considerations:
- Per [RFC4627], JSON is allowed to be represented using UTF-8, UTF-16, or UTF-32. When JSON is written in UTF-8, JSON is 8bit compatible ([RFC2045]). When JSON is written in UTF-16 or UTF-32, JSON is binary ([RFC2045]).
- Fragment identifier considerations:
-
- The syntax and semantics of fragment identifiers specified for +json SHOULD be as specified for "application/json". (At publication of this document, there is no fragment identification syntax defined for "application/json".)
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+json" SHOULD be processed as follows:
- For cases defined in +json, where the fragment identifier resolves per the +json rules, then as specified in +json.
- For cases defined in +json, where the fragment identifier does not resolve per the +json rules, then as specified in "xxx/yyy+json".
- For cases not defined in +json, then as specified in "xxx/yyy+json".
- Interoperability considerations:
- n/a
- Security considerations:
- See [RFC4627]
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
The ITU defined the Basic Encoding Rules (BER) message transfer syntax in [ITU.X690.2008]. The suffix "+ber" MAY be used with any media type whose representation follows the BER message transfer syntax. The Message Type Structured Syntax Suffix registration form for +ber follows:
- Name:
- Basic Encoding Rules (BER) message transfer syntax
- +suffix:
- +ber
- References:
-
[ITU.X690.2008]
- Encoding considerations:
- BER is a binary encoding.
- Fragment identifier considerations:
-
- At publication of this document, there is no fragment identification syntax defined for +ber.
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+ber" SHOULD be processed as follows:
- For cases defined in +ber, where the fragment identifier resolves per the +ber rules, then as specified in +ber.
- For cases defined in +ber, where the fragment identifier does not resolve per the +ber rules, then as specified in "xxx/yyy+ber".
- For cases not defined in +ber, then as specified in "xxx/yyy+ber".
- Interoperability considerations:
- n/a
- Security considerations:
- Each individual media type registered with a +ber suffix can have additional security considerations.
- BER has a type-length-value structure, and it is easy to construct malicious content with invalid length fields that can cause buffer overrun conditions.
- Some BER schema allow for arbitrary levels of nesting, which may make it possible to construct malicious content that will cause a stack overflow.
- Interpreters of the BER structures should be aware of these issues and should take appropriate measures to guard against buffer overflows and stack overruns in particular and malicious content in general.
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
The ITU defined the Distinguished Encoding Rules (DER) message transfer syntax in [ITU.X690.2008]. The suffix "+der" MAY be used with any media type whose representation follows the DER message transfer syntax. The Message Type Structured Syntax Suffix registration form for +der follows:
- Name:
- Distinguished Encoding Rules (DER) message transfer syntax
- +suffix:
- +der
- References:
-
[ITU.X690.2008]
- Encoding considerations:
- DER is a binary encoding.
- Fragment identifier considerations:
-
- At publication of this document, there is no fragment identification syntax defined for +der.
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+der" SHOULD be processed as follows:
- For cases defined in +der, where the fragment identifier resolves per the +der rules, then as specified in +der.
- For cases defined in +der, where the fragment identifier does not resolve per the +der rules, then as specified in "xxx/yyy+der".
- For cases not defined in +der, then as specified in "xxx/yyy+der".
- Interoperability considerations:
- n/a
- Security considerations:
- Each individual media type registered with a +der suffix can have additional security considerations.
- DER has a type-length-value structure, and it is easy to construct malicious content with invalid length fields that can cause buffer overrun conditions.
- Some DER schema allow for arbitrary levels of nesting, which may make it possible to construct malicious content that will cause a stack overflow.
- Interpreters of the DER structures should be aware of these issues and should take appropriate measures to guard against buffer overflows and stack overruns in particular and malicious content in general.
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
The ITU defined the Fast Infoset document format as a binary representation of the XML Information Set in [ITU.X891.2005]. These documents further define the "application/fastinfoset" media type. The suffix "+fastinfoset" MAY be used with any media type whose representation follows that established for "application/fastinfoset". The Message Type Structured Syntax Suffix registration form follows:
- Name:
- Fast Infoset document format
- +suffix:
- +fastinfoset
- References:
-
[ITU.X891.2005]
- Encoding considerations:
- Fast Infoset is a binary encoding. The binary, quoted-printable and base64 content-transfer-encodings are suitable for use with Fast Infoset.
- Fragment identifier considerations:
-
- The syntax and semantics of fragment identifiers specified for +fastinfoset SHOULD be as specified for "application/fastinfoset". (At publication of this document, there is no fragment identification syntax defined for "application/fastinfoset".)
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+fastinfoset" SHOULD be processed as follows:
- For cases defined in +fastinfoset, where the fragment identifier resolves per the +fastinfoset rules, then as specified in +fastinfoset.
- For cases defined in +fastinfoset, where the fragment identifier does not resolve per the +fastinfoset rules, then as specified in "xxx/yyy+fastinfoset".
- For cases not defined in +fastinfoset, then as specified in "xxx/yyy+fastinfoset".
- Interoperability considerations:
- n/a
- Security considerations:
- There are no security considerations inherent in Fast Infoset. Each individual media type registered with a +fastinfoset suffix can have additional security considerations.
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
The WAP Forum has defined the WAP Binary XML (WBXML) document format as a binary representation of XML in [WBXML]. This document further defines the "application/vnd.wap.wbxml" media type. The suffix "+wbxml" MAY be used with any media type whose representation follows that established for "application/vnd.wap.wbxml". The Message Type Structured Syntax Suffix registration form follows:
- Name:
- WAP Binary XML (WBXML) document format
- +suffix:
- +wbxml
- References:
-
[WBXML]
- Encoding considerations:
- WBXML is a binary encoding.
- Fragment identifier considerations:
-
- The syntax and semantics of fragment identifiers specified for +wbxml SHOULD be as specified for "application/vnd.wap.wbxml". (At publication of this document, there is no fragment identification syntax defined for "application/vnd.wap.wbxml".)
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+wbxml" SHOULD be processed as follows:
- For cases defined in +wbxml, where the fragment identifier resolves per the +wbxml rules, then as specified in +wbxml.
- For cases defined in +wbxml, where the fragment identifier does not resolve per the +wbxml rules, then as specified in "xxx/yyy+wbxml".
- For cases not defined in +wbxml, then as specified in "xxx/yyy+wbxml".
- Interoperability considerations:
- n/a
- Security considerations:
- There are no security considerations inherent in WBXML. Each individual media type registered with a +wbxml suffix can have additional security considerations.
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
The ZIP format is a public domain, cross-platform, interoperable file storage and transfer format, originally defined by PKWARE, Inc.; it supports compression and encryption and is used as the underlying representation by a variety of file formats. The media type "application/zip" has been registered for such files. The suffix "+zip" MAY be used with any media type whose representation follows that established for "application/zip". The Message Type Structured Syntax Suffix registration form follows:
- Name:
- ZIP file storage and transfer format
- +suffix:
- +zip
- References:
-
[ZIP]
- Encoding considerations:
- ZIP is a binary encoding.
- Fragment identifier considerations:
-
- The syntax and semantics of fragment identifiers specified for +zip SHOULD be as specified for "application/zip". (At publication of this document, there is no fragment identification syntax defined for "application/zip".)
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+zip" SHOULD be processed as follows:
- For cases defined in +zip, where the fragment identifier resolves per the +zip rules, then as specified in +zip.
- For cases defined in +zip, where the fragment identifier does not resolve per the +zip rules, then as specified in "xxx/yyy+zip".
- For cases not defined in +zip, then as specified in "xxx/yyy+zip".
- Interoperability considerations:
- n/a
- Security considerations:
- ZIP files support two forms of encryption: Strong Encryption and AES 128-bit, 192-bit and 256-bit encryption; see the specification for further details. Each individual media type registered with a +zip suffix can have additional security considerations.
- Contact:
- Apps Area Working Group (apps-discuss@ietf.org)
- Author/Change controller:
- The Apps Area Working Group has change control over this registration.
4. IANA Considerations
See the Message Type Structured Syntax Suffix registration forms in Section 3.1 - Section 3.6.
The existing Structured Syntax Suffix registration for "+xml" is modified to include the following
- Fragment identifier considerations:
-
- The syntax and semantics of fragment identifiers specified for +xml SHOULD be as specified for "application/xml". (At publication of this document, the fragment identification syntax considerations for "application/xml" are defined in [RFC3023], sections 5 and 7.)
- The syntax and semantics for fragment identifiers for a specific "xxx/yyy+xml" SHOULD be processed as follows:
- For cases defined in +xml, where the fragment identifier resolves per the +xml rules, then as specified in +xml.
- For cases defined in +xml, where the fragment identifier does not resolve per the +xml rules, then as specified in "xxx/yyy+xml".
- For cases not defined in +xml, then as specified in "xxx/yyy+xml".
5. Security Considerations
See the Security considerations sections found in the Message Type Structured Syntax Suffix registration forms from Section 3.1 - Section 3.5.
When updating a +<suffix> registration care should be taken to review all previously registered xxx/yyy+<suffix> media types regarding whether they might be affected by the updated +<suffix> registration, in particular by introduction of new or changing generic fragment identifier processing rules, as such rules take precedence over media-type-specific rules and thus might break existing registrations of specific media types, as well as particular implementations of applications that process affected media types. Such changes can introduce interoperability and security issues.
6. References
6.1. Normative References
| [RFC4627] |
Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, July 2006. |
| [ITU.X690.2008] |
International Telecommunications Union, "Recommendation ITU-T X.690 | ISO/IEC 8825-1 (2008), ASN.1 encoding rules: Specification of basic encoding Rules (BER), Canonical encoding rules (CER) and Distinguished encoding rules (DER)", ITU-T Recommendation X.690, November 2008. |
| [ITU.X891.2005] |
International Telecommunications Union, "Recommendation ITU-T X.891 | ISO/IEC 24824-1 (2007), Generic applications of ASN.1: Fast infoset", ITU-T Recommendation X.891, May 2005. |
| [WBXML] |
Open Mobile Alliance, "Binary XML Content Format Specification", OMA Wireless Access Protocol WAP-192-WBXML-20010725-a, July 2001. |
| [ZIP] |
PKWARE, Inc., "APPNOTE.TXT - .ZIP File Format Specification", PKWARE .ZIP File Format Specification - Version 6.3.2, September 2007. |
| [RFC2045] |
Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. |
| [RFC2119] |
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC3023] |
Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. |
6.2. Informative References
This section is to be removed before publication.
- draft-ietf-appsawg-media-type-suffix-regs-02
- Added BER/DER security considerations.
Reworked fragment identifier wording some more.
- draft-ietf-appsawg-media-type-suffix-regs-01
- Reordered the sections.
Cleaned up some MUSTard.
Fixed some references.
Added encoding considerations.
Reworked fragment identifier wording.
- draft-ietf-appsawg-media-type-suffix-regs-00
- Added the fragment identifier consideration sections.
Added a note about +xml fragment identifier considerations.
- draft-hansen-media-type-suffix-regs-02
- Added +zip.
Fixed up the ISO document references.
Minor changes.
- draft-hansen-media-type-suffix-regs-01
- Added +ber.
Minor changes.
Tony Hansen
Hansen
AT&T Laboratories
200 Laurel Ave. South
Middletown,
NJ
07748
USA
EMail: tony+sss@maillennium.att.com
Alexey Melnikov
Melnikov
Isode Ltd
5 Castle Business Village
36 Station Road
Hampton,
Middlesex
TW12 2BX
UK
EMail: Alexey.Melnikov@isode.com